Ribbon Communications Inc - Ordinary Shares 10-Q 4 Aug 17 2017 Q2 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	6 Months Ended
	Jun. 30, 2017	Jul. 26, 2017
Document And Entity Information
Entity Registrant Name	SONUS NETWORKS INC
Entity Central Index Key	1,105,472
Current Fiscal Year End Date	--12-31
Entity Filer Category	Accelerated Filer
Document Type	10-Q
Document Period End Date	Jun. 30, 2017
Document Fiscal Year Focus	2,017
Document Fiscal Period Focus	Q2
Amendment Flag	false
Entity Common Stock, Shares Outstanding		49,686,299

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Current assets:
Cash and cash equivalents	$ 32,606	$ 31,923
Marketable securities	54,793	61,836
Accounts receivable, net of allowance for doubtful accounts of $10 at both June 30, 2017 and December 31, 2016	42,664	53,862
Inventory	16,759	18,283
Other current assets	14,307	12,010
Total current assets	161,129	177,914
Property and equipment, net	10,656	11,741
Intangible assets, net	25,645	30,197
Goodwill	49,891	49,393
Investments	38,523	32,371
Deferred income taxes	1,586	1,542
Other assets	4,923	4,901
Total assets	292,353	308,059
Current liabilities:
Accounts payable	5,849	6,525
Accrued expenses	18,613	25,886
Current portion of deferred revenue	51,277	43,504
Current portion of long-term liabilities	1,210	1,154
Total current liabilities	76,949	77,069
Deferred revenue	7,530	7,188
Deferred income taxes	3,462	3,047
Other long-term liabilities	1,419	1,633
Total liabilities	89,360	88,937
Commitments and contingencies (Note 15)
Stockholders' equity:
Preferred stock, $0.01 par value per share; 5,000,000 shares authorized, none issued and outstanding	0	0
Common stock, $0.001 par value per share; 120,000,000 shares authorized; 49,677,161 shares issued and outstanding at June 30, 2017; 49,041,881 shares issued and outstanding at December 31, 2016	50	49
Additional paid-in capital	1,257,521	1,250,744
Accumulated deficit	(1,060,165)	(1,037,174)
Accumulated other comprehensive income	5,587	5,503
Total stockholders' equity	202,993	219,122
Total liabilities and stockholders' equity	$ 292,353	$ 308,059

Condensed Consolidated Balance3

Condensed Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Statement of Financial Position [Abstract]
Allowance for doubtful accounts	$ 10	$ 10
Preferred stock, par value (in dollars per share)	$ 0.01	$ 0.01
Preferred stock, shares authorized	5,000,000	5,000,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value (in dollars per share)	$ 0.001	$ 0.001
Common stock, shares authorized	120,000,000	120,000,000
Common stock, shares issued	49,297,373	49,041,881
Common stock, shares outstanding	49,297,373	49,041,881

Condensed Consolidated Statemen

Condensed Consolidated Statements of Operations - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Revenue:
Product	$ 28,790	$ 35,349	$ 54,185	$ 70,118
Service	26,943	25,508	54,916	49,890
Total revenue	55,733	60,857	109,101	120,008
Cost of revenue:
Product	9,287	11,409	19,040	22,945
Service	10,044	9,220	19,911	18,432
Total cost of revenue	19,331	20,629	38,951	41,377
Gross profit	36,402	40,228	70,150	78,631
Operating expenses:
Research and development	20,064	17,457	40,273	34,775
Sales and marketing	15,720	16,192	30,396	32,787
General and administrative	8,141	9,287	17,160	17,658
Acquisition-related	4,679	0	4,735	0
Restructuring	501	0	1,071	0
Total operating expenses	49,105	42,936	93,635	85,220
Loss from operations	(12,703)	(2,708)	(23,485)	(6,589)
Interest income, net	254	217	512	381
Other income, net	575	10	576	113
Loss before income taxes	(11,874)	(2,481)	(22,397)	(6,095)
Income tax provision	(471)	(435)	(594)	(1,475)
Net loss	$ (12,345)	$ (2,916)	$ (22,991)	$ (7,570)
Loss per share:
Basic (in dollars per share)	$ (0.25)	$ (0.06)	$ (0.47)	$ (0.15)
Diluted (in dollars per share)	$ (0.25)	$ (0.06)	$ (0.47)	$ (0.15)
Shares used to compute loss per share:
Basic (in shares)	49,543	49,423	49,330	49,453
Diluted (in shares)	49,543	49,423	49,330	49,453

Condensed Consolidated Stateme5

Condensed Consolidated Statements of Comprehensive Loss - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Statement of Comprehensive Income [Abstract]
Net loss	$ (12,345)	$ (2,916)	$ (22,991)	$ (7,570)
Other comprehensive income (loss), net of tax:
Foreign currency translation adjustments	(10)	262	115	435
Unrealized gain (loss) on available-for sale marketable securities, net of tax	(34)	37	(31)	272
Reclassification adjustment for realized losses included in net loss	0	0	0	18
Other comprehensive income (loss), net of tax	(44)	299	84	725
Comprehensive loss, net of tax	$ (12,389)	$ (2,617)	$ (22,907)	$ (6,845)

Condensed Consolidated Stateme6

Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016
Cash flows from operating activities:
Net loss	$ (22,991)	$ (7,570)
Adjustments to reconcile net loss to cash flows provided by operating activities:
Depreciation and amortization of property and equipment	3,595	3,970
Amortization of intangible assets	4,552	3,719
Stock-based compensation	7,500	9,056
Loss on disposal of property and equipment	6	26
Gain on sale of IP addresses	576	0
Deferred income taxes	446	587
Changes in operating assets and liabilities:
Accounts receivable	11,317	14,955
Inventory	829	844
Other operating assets	(1,061)	(2,566)
Accounts payable	(535)	(1,732)
Accrued expenses and other long-term liabilities	(8,089)	(11,182)
Deferred revenue	7,848	(888)
Net cash provided by operating activities	2,841	9,219
Cash flows from investing activities:
Purchases of property and equipment	(2,593)	(2,636)
Business acquisition, net of cash acquired	0	(750)
Purchases of marketable securities	(28,731)	(59,138)
Maturities/sales of marketable securities	29,067	44,364
Proceeds from the sale of IP addresses	576	0
Net cash used in investing activities	(1,681)	(18,160)
Cash flows from financing activities:
Proceeds from sale of common stock in connection with employee stock purchase plan	593	632
Proceeds from exercise of stock options	90	15
Payment of tax withholding obligations related to net share settlements of restricted stock awards	(1,406)	(832)
Repurchase of common stock	0	(4,980)
Principal payments of capital lease obligations	(20)	(24)
Net cash used in financing activities	(743)	(5,189)
Effect of exchange rate changes on cash and cash equivalents	266	280
Net increase (decrease) in cash and cash equivalents	683	(13,850)
Cash and cash equivalents, beginning of year	31,923	50,111
Cash and cash equivalents, end of period	32,606	36,261
Supplemental disclosure of cash flow information:
Interest paid	75	19
Income taxes paid	747	596
Income tax refunds received	80	249
Supplemental disclosure of non-cash investing activities:
Capital expenditures incurred, but not yet paid	222	256
Property and equipment acquired under capital lease	$ 0	$ 36

BASIS OF PRESENTATION

BASIS OF PRESENTATION	6 Months Ended
	Jun. 30, 2017
Accounting Policies [Abstract]
BASIS OF PRESENTATION	BASIS OF PRESENTATION Business Sonus Networks, Inc. (“Sonus” or the “Company”) is a leading provider of networked solutions for communications service providers (e.g., telecommunications, wireless and cable service providers) and enterprises to help them secure and unify their real-time communications infrastructures. Sonus helps many of the world's leading communications service providers and enterprises embrace the next generation of Session Initiation Protocol ("SIP") and 4G/LTE (Long-Term Evolution)-based solutions, including Voice over IP ("VoIP"), Voice over WiFi ("VoWiFi"), video and Unified Communications ("UC") through secure, reliable and scalable Internet Protocol ("IP") networks. Sonus' products include session border controllers ("SBCs"), diameter signaling controllers ("DSCs") and VoWiFi solutions, which are supported by a global services team with experience in the design, deployment and maintenance of the world's largest IP networks. Sonus' communications solutions provide a secure way for its customers to link and leverage multivendor, multiprotocol communications systems and applications across their networks, around the world and in a rapidly changing ecosystem of IP-enabled devices such as smartphones and tablets. Sonus' solutions help realize the intended value and benefits of UC platforms by allowing disparate communications environments, commonplace in most enterprises today, to work seamlessly together. Likewise, Sonus' solutions facilitate the evolution to cloud-based delivery of UC solutions. Proposed Merger On May 23, 2017, we entered into an Agreement and Plan of Merger (the “Merger Agreement”) with (i) Solstice Sapphire Investments, Inc. ("NewCo") and its wholly-owned subsidiaries and (ii) GENBAND Holdings Company ("GENBAND") and itwo related holding companies such that, following a series of merger transactions, both the Company and GENBAND will each become a wholly-owned subsidiary of NewCo. Former stockholders of the Company will own approximately 50% , and former shareholders of GENBAND and the two related holding companies will own approximately 50% , of the shares of NewCo common stock issued and outstanding immediately following the consummation of the mergers. GENBAND is a Cayman Islands exempted company limited by shares that was formed on April 7, 2010. Through its wholly owned operating subsidiaries, GENBAND creates rapid communications and applications for service providers, enterprises, independent software vendors, system integrators and developers globally. A majority of GENBAND's shares are held by funds affiliated with One Equity Partners. GENBAND shares are not listed on an exchange or quoted on any automated services, and there is no established trading market for GENBAND shares. As consideration, the Company will issue shares to the GENBAND equity holders, with the number of shares issued equal to the number of shares of the Company’s common stock outstanding immediately prior to the close date of the mergers. In addition, Sonus will repay GENBAND’s long-term debt to a related party totaling $45.0 million and repay GENBAND’s management fees due to a majority shareholder aggregating $10.3 million . The Company will also repay GENBAND’s outstanding balance under its line of credit facility and issue a promissory note for $22.5 million to the GENBAND equity holders. The Company will also pay GENBAND’s transaction fees incurred in connection with the mergers, estimated to approximate $9 million . The Company believes that the cash acquired from GENBAND as part of the mergers will exceed the balance outstanding under GENBAND's line of credit facility. The Company's Board of Directors unanimously approved the Merger Agreement and the transactions contemplated thereby, and the Company has agreed to hold a special meeting of the Company's stockholders to submit the Merger Agreement to its stockholders for their consideration (the “Special Stockholders’ Meeting”). Basis of Presentation In the opinion of management, the accompanying unaudited condensed consolidated financial statements include all adjustments, consisting only of normal recurring items, necessary for their fair presentation with accounting principles generally accepted in the United States of America ("GAAP") and with the rules and regulations of the U.S. Securities and Exchange Commission ("SEC"). Interim results are not necessarily indicative of results for a full year or any future interim period. The information included in this Quarterly Report on Form 10-Q should be read in conjunction with the Company's Annual Report on Form 10-K for the year ended December 31, 2016 (the "Annual Report"), which was filed with the SEC on February 27, 2017. Significant Accounting Policies The Company's significant accounting policies are disclosed in Note 2 to the Consolidated Financial Statements included in the Annual Report. There were no material changes to the significant accounting policies during either the three or six months ended June 30, 2017 . Principles of Consolidation The condensed consolidated financial statements include the accounts of Sonus and its wholly-owned subsidiaries. Intercompany transactions and balances have been eliminated in consolidation. Use of Estimates and Judgments The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reporting periods. Significant estimates and judgments relied upon in preparing these consolidated financial statements include accounting for business combinations, revenue recognition for multiple element arrangements, inventory valuations, assumptions used to determine the fair value of stock-based compensation, intangible assets and goodwill valuations, including impairments, legal contingencies and recoverability of Sonus' net deferred tax assets and the related valuation allowances. Sonus regularly assesses these estimates and records changes in estimates in the period in which they become known. Sonus bases its estimates on historical experience and various other assumptions that it believes to be reasonable under the circumstances. Actual results could differ from those estimates. Fair Value of Financial Instruments The carrying amounts of the Company's financial instruments, which include cash equivalents, marketable securities, investments, accounts receivable, accounts payable and other long-term liabilities, approximate their fair values. Operating Segments The Company operates in a single segment. Operating segments are identified as components of an enterprise about which separate discrete financial information is available for evaluation by the chief operating decision maker in making decisions regarding resource allocation and assessing performance. To date, the chief operating decision maker has made such decisions and assessed performance at the company level, as one segment. The Company's chief operating decision maker is its President and Chief Executive Officer. Recent Accounting Pronouncements In May 2017, the Financial Accounting Standards Board ("FASB") issued Accounting Standards Update ("ASU") 2017-09, Compensation - Stock Compensation (Topic 718): Scope of Modification Accounting ("ASU 2017-09"), which amends the scope of modification accounting for share-based payment arrangements. ASU 2017-09 provides guidance on the types of changes to the terms or conditions of share-based payment awards to which an entity would be required to apply modification accounting under Accounting Standards Codification ("ASC") 718. Specifically, an entity would not apply modification accounting if the fair value, vesting conditions and classification of the awards are the same immediately before and after the modification. ASU 2017-09 is effective for the Company beginning January 1, 2018 for both interim and annual reporting periods, with early adoption permitted. The Company does not expect the adoption of ASU 2017-09 will have a material impact on its consolidated financial statements. In January 2017, the FASB issued ASU 2017-04, Intangibles - Goodwill and Other (Topic 350): Simplifying the Test for Goodwill Impairment ("ASU 2017-04"), which removes the requirement to compare the implied fair value of goodwill with its carrying amount as part of step two of the goodwill impairment test. As a result, under ASU 2017-04, an entity should perform its annual, or interim, goodwill impairment test by comparing the fair value of a reporting unit with its carrying amount and should recognize an impairment charge for the amount by which the carrying amount exceeds the reporting unit's fair value; however, the loss recognized should not exceed the total amount of goodwill allocated to that reporting unit. In addition, ASU 2017-04 clarifies the requirements for excluding and allocating foreign currency translation adjustments to reporting units in connection with an entity's testing of reporting units for goodwill impairment; clarifies that an entity should consider income tax effects from any tax-deductible goodwill on the carrying amount of the reporting unit when measuring the goodwill impairment loss, if applicable; and makes minor changes to other related guidance within the ASC. ASU 2017-04 is effective prospectively for the Company beginning January 15, 2020, with early adoption permitted for interim or annual goodwill impairment tests performed on testing dates after January 1, 2017. The Company elected to early-adopt ASU 2017-04 as of January 1, 2017; such early adoption did not have a material impact on the Company's consolidated financial results. In October 2016, the FASB issued ASU 2016-16, Income Taxes (Topic 740): Intra-Entity Transfers of Assets Other Than Inventory ("ASU 2016-16"), which removes the prohibition in ASC 740, Income Taxes, against the immediate recognition of the current and deferred income tax effects of intra-entity transfers of assets other than inventory. ASU 2016-16 is intended to reduce the complexity of GAAP and diversity in practice related to the tax consequences of certain types of intra-entity asset transfers, particularly those involving intellectual property. ASU 2016-16 is effective for the Company beginning January 1, 2019 for both interim and annual reporting periods. The Company does not believe that the adoption of ASU 2016-16 will have a material impact on its consolidated financial statements. In August 2016, the FASB issued ASU 2016-15, Statement of Cash Flows (Topic 230): Classification of Certain Cash Receipts and Cash Payments ("ASU 2016-15"), which amends the guidance in ASC 230 on the classification of certain cash receipts and payments in the statement of cash flows. The primary purpose of ASU 2016-15 is to reduce the diversity in practice that has resulted from the lack of consistent principles on this topic. ASU 2016-15 adds or clarifies guidance on eight cash flow issues, including debt prepayment or debt extinguishment costs, settlement of zero-coupon debt instruments or certain other debt instruments, contingent consideration payments made after a business combination, proceeds from the settlement of insurance claims, proceeds from the settlement of corporate-owned life insurance policies, distributions received from equity method investees, beneficial interests in securitization transactions and separately identifiable cash flows and application of the predominance principle. ASU 2016-15 is effective for the Company beginning January 1, 2018 for both interim and annual reporting periods, with early adoption permitted. Entities must apply the guidance retrospectively to all periods presented but may apply it prospectively from the earliest date practicable if retrospective application would be impracticable. The Company does not expect the adoption of ASU 2016-15 will have a material impact on its consolidated financial statements. In June 2016, the FASB issued ASU 2016-13, Financial Instruments - Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instrument s ("ASU 2016-13"), which adds an impairment model that is based on expected losses rather than incurred losses. Under ASU 2016-13, an entity recognizes as an allowance its estimate of expected credit losses, which the FASB believes will result in more timely recognition of such losses. ASU 2016-13 is effective for the Company beginning January 1, 2020 for both interim and annual reporting periods, with early adoption permitted. The Company does not expect the adoption of ASU 2016-13 will have a material impact on its consolidated financial statements. In March 2016, the FASB issued ASU 2016-09, Compensation - Stock Compensation (Topic 718): Improvements to Employee Share-Based Payment Accounting ("ASU 2016-09"), which simplifies several aspects of the accounting for employee share-based payment transactions, including the accounting for income taxes, forfeitures and statutory tax withholding requirements, as well as classification in the statement of cash flows. ASU 2016-09 became effective for the Company beginning January 1, 2017 for both interim and annual reporting periods. Under ASU 2016-09, the Company will now recognize unrealized excess tax benefits. Due to the Company's full valuation allowance on its federal and state income taxes, the adoption of ASU 2016-09 did not have a material impact on the Company's accounting for income taxes. Without the valuation allowance, the Company would have recognized an increased deferred tax asset approximating $5 million . The Company has elected to continue to apply forfeiture rates to its expense attribution related to stock options, restricted stock awards and restricted stock units, as the Company believes that such continued application results in more accurate expense attribution over the life of these equity grants. The adoption of ASU 2016-09 did not have a material impact on the Company's consolidated financial statements. In February 2016, the FASB issued ASU 2016-02, Leases (Topic 842) Section A - Leases: Amendments to the FASB Accounting Standards Codification ("ASU 2016-02"), its new standard on accounting for leases. ASU 2016-02 introduces a lessee model that brings most leases onto the balance sheet. The new standard also aligns many of the underlying principles of the new lessor model with those in ASC 606, the FASB's new revenue recognition standard (i.e., those related to evaluating when profit can be recognized). Furthermore, ASU 2016-02 addresses other concerns related to the current leases model. For example, ASU 2016-02 eliminates the current GAAP requirement for an entity to use bright-line tests in determining lease classification. ASU 2016-02 is effective for the Company for both interim and annual periods beginning January 1, 2019. The Company is currently assessing the potential impact of the adoption of ASU 2016-02 on its consolidated financial statements. In July 2015, the FASB issued ASU 2015-11, Simplifying the Measurement of Inventory ("ASU 2015-11"), which simplifies the measurement of inventory by requiring entities to measure most inventory at the lower of cost and net realizable value, replacing the previous requirement to measure most inventory at the lower of cost or market. ASU 2015-11 does not apply to inventories that are measured by using either the last-in, first-out method or the retail inventory method. ASU 2015-11 became effective for the Company for both interim and annual reporting periods beginning January 1, 2017. The adoption of ASU 2015-11 did not have a material impact on the Company's consolidated financial statements. In May 2014, the FASB issued ASU 2014-09, Revenue from Contracts with Customers (“ASU 2014-09”), its final standard on revenue from contracts with customers, along with additional ASUs which, among other things, clarified the implementation of the new revenue guidance and delayed the adoption by one year, to January 1, 2018 (collectively, the "New Revenue Standard"). The New Revenue Standard outlines a single comprehensive model for entities to use in accounting for revenue arising from contracts with customers and supersedes most current revenue recognition guidance, including industry-specific guidance. The core principle of the revenue model is that an entity recognizes revenue to depict the transfer of promised goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services. In applying the revenue model to contracts within its scope, an entity identifies the contract(s) with a customer, identifies the performance obligations in the contract, determines the transaction price, allocates the transaction price to the performance obligations in the contract and recognizes revenue when (or as) the entity satisfies a performance obligation. The New Revenue Standard applies to all contracts with customers that are within the scope of other topics in the ASC. Certain of the New Revenue Standard's provisions also apply to transfers of nonfinancial assets, including in-substance nonfinancial assets that are not an output of an entity’s ordinary activities (i.e., property, plant and equipment; real estate; or intangible assets). Existing accounting guidance applicable to these transfers has been amended or superseded. The Company continues to assess the potential impact of the adoption of the New Revenue Standard on its consolidated financial statements, and currently believes that such adoption will, in general, accelerate the recognition of revenue (i.e., more revenue will be recognized upon delivery than is currently recognized ratably or upon payment) compared to the current standards in effect, in particular, sales of software-only products and sales to customers currently accounted for on a cash basis. The Company currently expects to adopt the New Revenue Standard using the modified retrospective option, and is in the process of updating its revenue recognition software to comply with the New Revenue Standard. The Company expects to begin parallel testing in the third quarter of 2017.

BUSINESS ACQUISITION

BUSINESS ACQUISITION	6 Months Ended
	Jun. 30, 2017
Business Combinations [Abstract]
BUSINESS ACQUISITIONS	BUSINESS ACQUISITION Acquisition of Taqua, LLC On September 26, 2016 (the "Taqua Acquisition Date"), the Company acquired Taqua, LLC ("Taqua"), a leading supplier of IP communications systems, applications and services to mobile and fixed operators. Taqua enables the transformation of software-based service provider networks to deliver next-generation voice, video and messaging services, including VoIP, VoWiFi and Voice over Long-Term Evolution ("VoLTE"). The acquisition of Taqua has, among other things, accelerated the Company's mobile strategy by adding a Virtualized Mobile Core ("VMC") Platform and an IP Multimedia Subsystem ("IMS") Service Core and expanded the Company's fixed portfolio by adding a Class 5 Softswitch (the T7000) for network transformation projects and a Multimedia Controller used in IP Peering applications (the T7100), both of which are complementary to Sonus' current product offerings. In consideration for the acquisition of Taqua, Sonus paid $19.9 million in cash to the sellers on the Taqua Acquisition Date, net of cash acquired. The Company also entered into an Earn-Out Agreement, dated as of September 26, 2016, with Taqua Holdings, LLC and Jeffrey L. Brawner, the seller representative in the transaction, under which there is the potential for additional cash payments of up to $65.0 million in the aggregate to the sellers if certain annual revenue thresholds are exceeded as measured annually through 2020. The Company had initially recorded $10.0 million of contingent consideration as of the Taqua Acquisition Date, with the estimate based on historical sales and probability weighted cash flows related to forecasted sales. During the fourth quarter of 2016, the Company reassessed the historical and updated forecasted sales and accordingly, reversed the previous estimated contingent consideration such that as of both June 30, 2017 and December 31, 2016, no incremental contingent consideration was recorded. The transaction has been accounted for as a business combination and the financial results of Taqua have been included in the Company's condensed consolidated financial statements for the period subsequent to its acquisition. The Company finalized its valuation of the identifiable intangible assets in the second quarter of 2017. During both the first quarter of 2017 and the fourth quarter of 2016, the Company recorded changes to the initial preliminary purchase price allocation. The primary adjustments in the first quarter of 2017 were a $0.4 million increase to current liabilities and a $0.1 million increase to noncurrent liabilities. The primary adjustments recorded in the fourth quarter of 2016 were the reversal of the $10.0 million of previously recorded contingent consideration discussed above, a reduction of $12.1 million to the developed technology intangible asset and an increase of $5.5 million to the customer relationship intangible assets. These adjustments, as well as other immaterial adjustments to the balance sheet accounts, resulted in a net reduction to goodwill of $2.2 million since September 30, 2016. Based on this final purchase price allocation, the Company recorded $9.6 million of goodwill, which is primarily due to expected synergies between the combined companies and expanded market opportunities resulting from the expanded product offering portfolio. The goodwill is deductible for tax purposes. A summary of the final allocation of the purchase consideration for Taqua is as follows (in thousands): Fair value of consideration transferred: Cash, net of cash acquired $ 19,919 Fair value of assets acquired and liabilities assumed: Current assets $ 3,347 Property and equipment 1,478 Intangible assets: Developed technology 2,100 Customer relationships 9,510 Goodwill 9,581 Other noncurrent assets 23 Current liabilities (5,435 ) Long-term liabilities (685 ) $ 19,919 The valuation of the acquired intangible assets is inherently subjective and relies on significant unobservable inputs. The Company used an income approach to value the acquired developed technology and customer relationship intangible assets. The valuation for each of these intangible assets was based on estimated projections of expected cash flows to be generated by the assets, discounted to the present value at discount rates commensurate with perceived risk. The valuation assumptions take into consideration the Company's estimates of technology attrition and revenue growth projections. The Company is amortizing the identifiable intangible assets in relation to the expected cash flows from the individual intangible assets over their respective useful lives (see Note 6 ). The Company has not provided pro forma financial information, as the historical amount are not significant to the Company's consolidated financial statements. Acquisition-Related Expenses Acquisition-related expenses include those expenses related to acquisitions that would otherwise not have been incurred by the Company. These expenses include professional, services and other costs, such as legal, audit, consulting, paying agent and other related expenses. The expense recorded in the three months ended June 30, 2017 relates to the proposed merger with GENBAND, while the expense recorded in the six months ended June 30, 2017 also includes approximately $56,000 of costs related to the Taqua acquisition. The Company did not record acquisition-related expenses in the three or six months ended June 30, 2016.

EARNINGS (LOSS) PER SHARE

EARNINGS (LOSS) PER SHARE	6 Months Ended
	Jun. 30, 2017
Earnings Per Share [Abstract]
EARNINGS (LOSS) PER SHARE	EARNINGS (LOSS) PER SHARE Basic earnings (loss) per share is computed by dividing net income (loss) by the weighted average number of shares outstanding during the period. For periods in which the Company reports net income, diluted net income per share is determined by using the weighted average number of common and dilutive common equivalent shares outstanding during the period unless the effect is antidilutive. The calculations of shares used to compute basic and diluted loss per share are as follows (in thousands): Three months ended Six months ended June 30, June 30, June 30, June 30, Weighted average shares outstanding—basic 49,543 49,423 49,330 49,453 Potential dilutive common shares — — — — Weighted average shares outstanding—diluted 49,543 49,423 49,330 49,453 Options to purchase the Company's common stock, unvested shares of restricted stock, unvested shares of performance-based stock and shares in connection with future purchases under the Company's Amended and Restated 2000 Employee Stock Purchase Plan, as amended (the "ESPP"), totaling 8.0 million shares for the three and six months ended June 30, 2017 and 8.7 million shares for the three and six months ended June 30, 2016 have not been included in the computation of diluted loss per share because their effect would have been antidilutive.

CASH EQUIVALENTS AND INVESTMENT

CASH EQUIVALENTS AND INVESTMENTS	6 Months Ended
	Jun. 30, 2017
Investments, All Other Investments [Abstract]
CASH EQUIVALENTS, MARKETABLE SECURITIES AND INVESTMENTS	CASH EQUIVALENTS AND INVESTMENTS The Company invests in debt instruments, primarily U.S. government-backed, municipal and corporate obligations, which management believes to be high quality (investment grade) credit instruments. During the six months ended June 30, 2016, the Company sold $3.8 million of its available-for-sale securities and recognized gross losses aggregating $18,000 , which is included as a component of Other income, net, in the Company's condensed consolidated statement of operations for that period. The Company did not sell any of its available-for-sale securities in the six months ended June 30, 2017. Investments with continuous unrealized losses for one year or greater at June 30, 2017 were nominal. Since the Company currently does not intend to sell these securities and does not believe it will be required to sell any securities before they recover in value, it does not believe these declines are other-than-temporary. On a quarterly basis, the Company reviews its marketable securities and investments to determine if there have been any events that could create a credit impairment. Based on its reviews, the Company does not believe that any impairment existed with its current holdings at June 30, 2017 . The amortized cost, gross unrealized gains and losses and fair value of the Company's marketable debt securities and investments at June 30, 2017 and December 31, 2016 were comprised of the following (in thousands): June 30, 2017 Amortized cost Unrealized gains Unrealized losses Fair value Cash equivalents $ 7,669 $ — $ — $ 7,669 Marketable securities Municipal obligations $ 1,091 $ — $ — $ 1,091 U.S. government agency notes 23,866 — (39 ) 23,827 Corporate debt securities 28,693 — (44 ) 28,649 Certificates of deposit 1,226 — — 1,226 $ 54,876 $ — $ (83 ) $ 54,793 Investments U.S. government agency notes $ 16,590 $ — $ (44 ) $ 16,546 Corporate debt securities 16,664 5 (33 ) 16,636 Certificates of deposit 5,341 — — 5,341 $ 38,595 $ 5 $ (77 ) $ 38,523 December 31, 2016 Amortized cost Unrealized gains Unrealized losses Fair value Cash equivalents $ 6,619 $ — $ — $ 6,619 Marketable securities Municipal obligations $ 3,264 $ — $ (3 ) $ 3,261 U.S. government agency notes 16,477 3 (3 ) 16,477 Corporate debt securities 41,893 4 (45 ) 41,852 Certificates of deposit 246 — — 246 $ 61,880 $ 7 $ (51 ) $ 61,836 Investments U.S. government agency notes $ 19,473 $ 3 $ (39 ) $ 19,437 Corporate debt securities 10,520 — (44 ) 10,476 Certificates of deposit 2,458 — — 2,458 $ 32,451 $ 3 $ (83 ) $ 32,371 The Company's available-for-sale debt securities classified as Investments in the condensed consolidated balance sheets at June 30, 2017 and December 31, 2016 had maturity dates after one year but within approximately two years or less from the balance sheet date. Fair Value Hierarchy Fair value is the price that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants. As such, fair value is a market-based measurement that should be determined based on assumptions that market participants would use in pricing an asset or a liability. The three-tier fair value hierarchy is based on the level of independent, objective evidence surrounding the inputs used to measure fair value. A financial instrument's categorization within the fair value hierarchy is based upon the lowest level of input that is significant to the fair value measurement. The fair value hierarchy is as follows: Level 1. Level 1 applies to assets or liabilities for which there are quoted prices in active markets for identical assets or liabilities. Level 2. Level 2 applies to assets or liabilities for which there are inputs that are directly or indirectly observable in the marketplace, such as quoted prices for similar assets or liabilities in active markets or quoted prices for identical assets or liabilities in markets with insufficient volume or infrequent transactions (less active markets). Level 3. Level 3 applies to assets or liabilities for which there are unobservable inputs to the valuation methodology that are significant to the measurement of the fair value of the assets or liabilities. The following table shows the fair value of the Company's financial assets at June 30, 2017 and December 31, 2016 . These financial assets are comprised of the Company's available-for-sale debt securities and reported under the captions Cash and cash equivalents, Marketable securities and Investments in the condensed consolidated balance sheets (in thousands): Fair value measurements at Total carrying Quoted prices in active markets (Level 1) Significant other observable inputs (Level 2) Significant unobservable inputs (Level 3) Cash equivalents $ 7,669 $ 7,669 $ — $ — Marketable securities Municipal obligations $ 1,091 $ — $ 1,091 $ — U.S. government agency notes 23,827 — 23,827 — Corporate debt securities 28,649 — 28,649 — Certificates of deposit 1,226 — 1,226 — $ 54,793 $ — $ 54,793 $ — Investments U.S. government agency notes $ 16,546 $ — $ 16,546 $ — Corporate debt securities 16,636 — 16,636 — Certificates of deposit 5,341 — 5,341 — $ 38,523 $ — $ 38,523 $ — Fair value measurements at Total carrying Quoted prices in active markets (Level 1) Significant other observable inputs (Level 2) Significant unobservable inputs (Level 3) Cash equivalents $ 6,619 $ 6,619 $ — $ — Marketable securities Municipal obligations $ 3,261 $ — $ 3,261 $ — U.S. government agency notes 16,477 — 16,477 — Corporate debt securities 41,852 — 41,852 — Certificates of deposit 246 — 246 — $ 61,836 $ — $ 61,836 $ — Investments U.S. government agency notes $ 19,437 $ — $ 19,437 $ — Corporate debt securities 10,476 — 10,476 — Certificates of deposit 2,458 — 2,458 — $ 32,371 $ — $ 32,371 $ — The Company's marketable securities and investments have been valued with the assistance of valuations provided by third-party pricing services, as derived from such services' pricing models. Inputs to the models may include, but are not limited to, reported trades, executable bid and asked prices, broker/dealer quotations, prices or yields of securities with similar characteristics, benchmark curves or information pertaining to the issuer, as well as industry and economic events. The pricing services may use a matrix approach, which considers information regarding securities with similar characteristics to determine the valuation for a security. The Company is ultimately responsible for the condensed consolidated financial statements and underlying estimates. Accordingly, the Company assesses the reasonableness of the valuations provided by the third-party pricing services by reviewing actual trade data, broker/dealer quotes and other similar data, which are obtained from quoted market prices or other sources.

INVENTORY

INVENTORY	6 Months Ended
	Jun. 30, 2017
Inventory Disclosure [Abstract]
INVENTORY	INVENTORY Inventory at June 30, 2017 and December 31, 2016 consists of the following (in thousands): June 30, December 31, On-hand final assemblies and finished goods inventories $ 15,935 $ 15,346 Deferred cost of goods sold 2,824 4,237 18,759 19,583 Less current portion (16,759 ) (18,283 ) Noncurrent portion (included in Other assets) $ 2,000 $ 1,300

INTANGIBLE ASSETS AND GOODWILL

INTANGIBLE ASSETS AND GOODWILL	6 Months Ended
	Jun. 30, 2017
Goodwill and Intangible Assets Disclosure [Abstract]
INTANGIBLE ASSETS AND GOODWILL	INTANGIBLE ASSETS AND GOODWILL The Company's intangible assets at June 30, 2017 and December 31, 2016 consist of the following (dollars in thousands): June 30, 2017 Weighted average amortization period (years) Cost Accumulated amortization Net carrying value Developed technology 6.54 $ 34,980 $ 19,620 $ 15,360 Customer relationships 5.78 19,540 9,255 10,285 Internal use software 3.00 730 730 — 6.23 $ 55,250 $ 29,605 $ 25,645 December 31, 2016 Weighted average amortization period (years) Cost Accumulated amortization Net carrying value Developed technology 6.54 $ 34,980 $ 16,453 $ 18,527 Customer relationships 5.78 19,540 7,870 11,670 Internal use software 3.00 730 730 — 6.23 $ 55,250 $ 25,053 $ 30,197 Amortization expense for intangible assets for the three and six months ended June 30, 2017 and 2016 was as follows (in thousands): Three months ended Six months ended Statement of operations classification June 30, June 30, June 30, June 30, Developed technology $ 1,601 $ 1,455 $ 3,167 $ 3,082 Cost of revenue - product Customer relationships 692 318 1,385 637 Sales and marketing $ 2,293 $ 1,773 $ 4,552 $ 3,719 Estimated future amortization expense for the Company's intangible assets at June 30, 2017 is as follows (in thousands): Years ending December 31, Remainder of 2017 $ 4,587 2018 6,615 2019 5,608 2020 4,166 2021 2,395 Thereafter 2,274 $ 25,645 The changes in the carrying value of the Company's goodwill in the six months ended June 30, 2017 were as follows (in thousands): Balance at January 1, 2017 Goodwill $ 52,499 Accumulated impairment losses (3,106 ) 49,393 Purchase accounting adjustments - Taqua 498 Balance at June 30, 2017 $ 49,891 Balance at June 30, 2017 Goodwill $ 52,997 Accumulated impairment losses (3,106 ) $ 49,891 There were no changes in the carrying value of the Company's goodwill in the six months ended June 30, 2016 . The balance of the Company's goodwill at June 30, 2016 was comprised of the following (in thousands): Balance at June 30, 2016 Goodwill $ 43,416 Accumulated impairment losses (3,106 ) $ 40,310

ACCRUED EXPENSES

ACCRUED EXPENSES	6 Months Ended
	Jun. 30, 2017
Payables and Accruals [Abstract]
ACCRUED EXPENSES	ACCRUED EXPENSES Accrued expenses at June 30, 2017 and December 31, 2016 consist of the following (in thousands): June 30, December 31, Employee compensation and related costs $ 11,715 $ 15,879 Other 6,898 10,007 $ 18,613 $ 25,886

RESTRUCTURING ACCRUAL

RESTRUCTURING ACCRUAL	6 Months Ended
	Jun. 30, 2017
Restructuring and Related Activities [Abstract]
RESTRUCTURING ACCRUAL	RESTRUCTURING ACCRUAL 2016 Restructuring Initiative In July 2016, the Company announced a program to further accelerate its investment in new technologies as the communications industry migrates to a cloud-based architecture (the "2016 Restructuring Initiative"), and that it planned to utilize most of the savings from this initiative to shift headcount toward new strategic initiatives, such as new products and an expanded go-to-market footprint in selected geographies and discrete vertical markets. The Company recorded $2.0 million of restructuring expense in the aggregate in connection with this initiative, comprised of $1.9 million for severance and related costs and $0.1 million to abandon its facility in Rochester, New York (the "Rochester Facility"). The actions under the 2016 Restructuring Initiative have been implemented and accordingly, the Company does not expect to record additional expense in connection with this initiative. The Company expects that the amounts accrued for severance and related costs under the 2016 Restructuring Initiative will be paid by end of the fourth quarter of 2017 and that the amounts accrued for facilities will be paid by the end of October 2019, when the lease on the Rochester Facility expires. In connection with the 2016 Restructuring Initiative, the Company recorded $0.3 million of restructuring expense in the three months ended June 30, 2017 and $0.5 million of restructuring expense in the six months ended June 30, 2017. The amount recorded in the three months ended June 30, 2017 is comprised of $0.2 million for severance and related costs and $0.1 million related to the Rochester Facility. The amount recorded in the six months ended June 30, 2017 is comprised of $0.4 million for severance and related costs and $0.1 million related to the Rochester Facility. A summary of the 2016 Restructuring Initiative accrual activity for the six months ended June 30, 2017 is as follows (in thousands): Balance at Initiatives Adjustments for changes in estimate Cash Balance at Severance $ 497 $ 405 $ (26 ) $ (763 ) $ 113 Facilities — 126 — (3 ) 123 $ 497 $ 531 $ (26 ) $ (766 ) $ 236 Taqua Restructuring Initiative In connection with the acquisition of Taqua, the Company's management approved a restructuring plan in the third quarter of 2016 to eliminate certain redundant positions within the combined companies. On October 24, 2016, the Audit Committee of the Company's Board of Directors approved a broader Taqua restructuring plan related to headcount and redundant facilities (both restructuring plans, the "Taqua Restructuring Initiative"). The Company recorded $1.8 million of restructuring expense in the aggregate in connection with this initiative, comprised of $1.2 million for severance and related costs and $0.6 million related to the elimination of redundant facilities. The actions under the Taqua Restructuring Initiative have been implemented and accordingly, the Company does not expect to record additional expense in connection with this initiative. The Company expects that the amounts accrued for severance and related costs under the Taqua Restructuring Initiative will be paid by the end of 2017 and that the amounts accrued for facilities will be paid by the end of 2018. In connection with the Taqua Restructuring Initiative, the Company recorded $0.2 million of restructuring expense in the three months ended June 30, 2017 for severance and related costs and $0.6 million of restructuring expense in the six months ended June 30, 2017, comprised of $0.2 million for severance and related costs and $0.4 million related to redundant facilities. A summary of the Taqua Restructuring Initiative accrual activity for the six months ended June 30, 2017 is as follows (in thousands): Balance at Initiatives Adjustments for changes in estimate Cash Balance at Severance $ 384 $ 245 $ (49 ) $ (569 ) $ 11 Facilities 218 370 — (190 ) 398 $ 602 $ 615 $ (49 ) $ (759 ) $ 409 2015 Restructuring Initiative To better align the Company's cost structure to its current revenue expectations, in April 2015, the Company announced a cost reduction review and restructuring initiative (the "2015 Restructuring Initiative"). A summary of the 2015 Restructuring Initiative accrual activity for the six months ended June 30, 2017 is as follows (in thousands): Balance at Initiatives Adjustments for changes in estimate Cash Balance at Severance $ 168 $ — $ — $ (168 ) $ — Balance Sheet Classification At June 30, 2017 , the Company's restructuring accruals aggregated $0.6 million , of which $0.3 million was included in Other long-term liabilities and represented future lease payments on restructured facilities. At December 31, 2016 , the Company's restructuring accruals aggregated $1.3 million , of which approximately $62,000 was included in Other long-term liabilities and represented future lease payments on restructured facilities. The remainder of the restructuring accruals at both June 30, 2017 and December 31, 2016 are included in Accrued expenses in the condensed consolidated balance sheets.

DEBT

DEBT	6 Months Ended
	Jun. 30, 2017
Debt Disclosure [Abstract]
DEBT	DEBT The Company maintained a credit agreement by and among the Company, as Borrower, Bank of America, N.A. ("Bank of America"), as Administrative Agent, Swing Line Lender and L/C Issuer, and the other lenders from time to time party thereto entered into on June 27, 2014 (the "Credit Agreement"), which agreement was amended by a First Amendment to Credit Agreement on June 26, 2015 and further amended by a Second Amendment to Credit Agreement on June 13, 2016 (the "Amended Credit Agreement"). The obligations of the Company under the Amended Credit Agreement were guaranteed by Sonus International, Inc., Sonus Federal, Inc., Network Equipment Technologies, Inc. and Taqua (collectively with the Company, the "Loan Parties") pursuant to a Master Continuing Guaranty and were secured by the assets of the Loan Parties pursuant to a Security and Pledge Agreement. The credit facility expired by its terms on June 30, 2017 and was not renewed. The Company did not have any amounts outstanding under the Amended Credit Agreement at either June 30, 2017 or December 31, 2016 .

COMMON STOCK REPURCHASES (Notes

COMMON STOCK REPURCHASES (Notes)	6 Months Ended
	Jun. 30, 2017
Equity [Abstract]
COMMON STOCK REPURCHASES	COMMON STOCK REPURCHASES On July 29, 2013, the Company announced that its Board of Directors had authorized a stock buyback program to repurchase up to $100 million of the Company's common stock from time to time on the open market or in privately negotiated transactions. The timing and amount of any shares repurchased will be determined by the Company's management based on its evaluation of market conditions and other factors. The Company may elect to implement a 10b5-1 repurchase program, which would permit shares to be repurchased when the Company might otherwise be precluded from doing so under insider trading laws. The Company has not implemented such a 10b5-1 repurchase program to date. The stock buyback program may be suspended or discontinued at any time. The stock buyback program is funded with the Company's working capital. The Company did not repurchase any shares during the six months ended June 30, 2017 . During the six months ended June 30, 2016 , the Company spent $5.0 million , including transaction fees, to repurchase and retire 0.6 million shares of its common stock under the stock buyback program. At June 30, 2017 , the Company had $5.4 million remaining under the stock buyback program for future repurchases.

STOCK-BASED COMPENSATION PLANS

STOCK-BASED COMPENSATION PLANS	6 Months Ended
	Jun. 30, 2017
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
STOCK-BASED COMPENSATION PLANS	STOCK-BASED COMPENSATION PLANS Amended and Restated Stock Incentive Plan The Company's Amended and Restated Stock Incentive Plan, as amended (the "Plan"), provides for the award of options to purchase the Company's common stock ("stock options"), stock appreciation rights ("SARs"), restricted common stock awards ("RSAs"), restricted common stock units ("RSUs"), performance-based stock awards ("PSAs"), performance-based stock units ("PSUs") and other stock-based awards to employees, officers, directors (including those directors who are not employees or officers of the Company), consultants and advisors of the Company and its subsidiaries. At its 2017 annual meeting of stockholders held on June 9, 2017 (the "2017 Annual Meeting"), the Company's stockholders approved amendments to the Plan including, among other things, to: • Increase the aggregate number of shares of the Company's common stock authorized for issuance under the Plan by an additional 900,000 shares; • Make the Plan more explicit by providing that any dividends on unvested restricted stock or with respect to shares of common stock granted under restricted stock units and other stock unit awards will be paid to a participant only if and when such shares become free from the restrictions on transferability and forfeitability that apply to such shares and that any dividend equivalents with respect to restricted stock units and other stock unit awards will be subject to the same vesting conditions and restrictions on transfer and forfeitability applicable to the underlying award with respect to which it is paid. No interest will be paid on any such equivalents or dividend equivalents; • Explicitly require a participant who accepts an award under the Plan to be bound by any clawback policy that the Company has in effect or may adopt in the future; and • Eliminate the requirement that each share of stock subject to an award of restricted stock, restricted stock units, performance awards or other stock unit awards (collectively, "full value awards") be counted against the share reserve as 1.50 shares for every one share subject to such award. This change applies to all full value awards from and after June 9, 2017, the date of the Annual Meeting. Shares of common stock subject to awards that were granted under any prior ratio that applied at the time such awards were granted will continue to return to the Plan upon forfeiture of such awards at the previous applicable ratio. Executive Equity Arrangements On March 31, 2017, the Company granted an aggregate of 165,000 PSUs with both market and service conditions to five of its executives (the "2017 PSUs"). The terms of the 2017 PSUs are such that up to one-third of the shares subject to the 2017 PSUs will vest on each of the first, second and third anniversaries of the date of grant (collectively, the "2017 PSU Vesting Dates") to the extent of achievement of the Company's total shareholder return ("TSR") compared to the TSR of the companies included in the NASDAQ Telecommunications Index for the same fiscal year, measured by the Compensation Committee after each of the 2017, 2018 and 2019 fiscal years, respectively (as used in this paragraph, each, a "Performance Period"). The shares determined to be earned will vest on the anniversary of the grant date following each Performance Period. Shares subject to the 2017 PSUs that fail to be earned will be forfeited. The 2017 PSUs include a market condition that required the use of a Monte Carlo simulation approach to model future stock price movements based upon the risk-free rate of return, the volatility of each entity, and the pair-wise covariance between each entity. These results were then used to calculate the grant date fair values of the 2017 PSUs. Because the 2017 PSUs have market conditions, the Company is required to record expense for the 2017 PSUs through the final 2017 PSU Vesting Date of March 31, 2020, regardless of the number of shares that are ultimately earned. On April 1, 2016, the Company granted an aggregate of 131,250 PSUs with both market and service conditions to six of its executives (the "2016 PSUs"). The terms of the 2016 PSUs are such that up to one-third of the shares subject to the 2016 PSUs will vest on each of the first, second and third anniversaries of the date of grant (collectively, the "2016 PSU Vesting Dates") to the extent of achievement of the Company's TSR compared to the TSR of the companies included in the NASDAQ Telecommunications Index for the same fiscal year, measured by the Compensation Committee of the Company's Board of Directors (the "Compensation Committee") after each of the 2016, 2017 and 2018 fiscal years, respectively (as used in this paragraph, each, a "Performance Period"). The shares determined to be earned will vest on the anniversary of the grant date following each Performance Period. Shares subject to the 2016 PSUs that fail to be earned will be forfeited. The 2016 PSUs include a market condition that required the use of a Monte Carlo simulation approach to model future stock price movements based upon the risk-free rate of return, the volatility of each entity, and the pair-wise covariance between each entity. These results were then used to calculate the grant date fair values of the 2016 PSUs. Because the 2016 PSUs have market conditions, the Company is required to record expense for the 2016 PSUs through the final 2016 PSU Vesting Date of April 1, 2019, regardless of the number of shares that are ultimately earned. In February 2017, the Compensation Committee determined that the performance metrics for the 2016 PSUs for the 2016 Performance Period had been achieved at the 90.4% level, and accordingly, 24,106 shares in the aggregate were released to the four executives holding such outstanding grants on March 16, 2017. The unearned shares relating to the 2016 Performance Period, aggregating 2,560 shares, were forfeited on March 16, 2017. These amounts are included in the performance-based units table below. On March 16, 2015, the Company granted an aggregate of 131,250 PSUs with both market and service conditions to eight of its executives (the "2015 PSUs"). In 2015, subsequent to the grant date, two executives separated from the Company and, in accordance with their respective employment agreements with the Company, the Company accelerated the vesting of certain unvested 2015 PSUs. The terms of the 2015 PSUs are such that up to one-third of the shares subject to the 2015 PSUs will vest on each of the first, second and third anniversaries of the date of grant (collectively, the "2015 PSU Vesting Dates") to the extent of achievement of the Company's TSR compared to the TSR of the companies included in the NASDAQ Telecommunications Index for the same Performance Period, measured by the Compensation Committee at the end of each of the 2015, 2016 and 2017 fiscal years, respectively (as used in this paragraph, each, a "Performance Period"). The shares determined to be earned will vest on the anniversary of the grant date following each Performance Period. Shares subject to the 2015 PSUs that fail to be earned will be forfeited. The 2015 PSUs include a market condition that required the use of a Monte Carlo simulation approach to calculate the grant date fair values of the 2015 PSUs. Because the 2015 PSUs have market conditions, the Company is required to record expense for the 2015 PSUs through the final 2015 PSU Vesting Date of March 16, 2018, regardless of the number of shares that are ultimately earned, if any. In February 2017, the Compensation Committee determined that the performance metrics for the 2015 PSUs for the 2016 Performance Period had been achieved at the 76.0% level, and accordingly, 23,750 shares in the aggregate were released to the four executives holding such outstanding grants on April 1, 2017. The unearned shares relating to the 2016 Performance Period, aggregating 7,500 shares, were forfeited on April 1, 2017. These amounts are included in the performance-based units table below. Stock Options The activity related to the Company's outstanding stock options for the six months ended June 30, 2017 is as follows: Number of Shares Weighted Average Exercise Price Weighted Average Remaining Contractual Term (years) Aggregate Intrinsic Value (in thousands) Outstanding at January 1, 2017 5,610,106 $ 15.73 Granted 5,200 $ 6.46 Exercised (21,815 ) $ 4.13 Forfeited (27,665 ) $ 14.32 Expired (154,043 ) $ 19.31 Outstanding at June 30, 2017 5,411,783 $ 15.67 4.88 $ 168 Vested or expected to vest at June 30, 2017 5,378,996 $ 15.69 4.86 $ 163 Exercisable at June 30, 2017 4,954,545 $ 15.76 4.63 $ 137 The grant date fair values of options to purchase common stock granted in the three and six months ended June 30, 2017 were estimated using the Black-Scholes valuation model with the following assumptions: Three months ended Six months ended June 30, June 30, Risk-free interest rate 1.81% 1.81% - 1.95% Expected dividends — — Weighted average volatility 51.4% 51.3% Expected life (years) 5.0 5.0 Additional information regarding the Company's stock options for the three and six months ended June 30, 2017 is as follows: Three months ended Six months ended June 30, June 30, Weighted average grant date fair value of stock options granted $ 3.48 $ 2.98 Total intrinsic value of stock options exercised (in thousands) $ 25 $ 62 Cash received from the exercise of stock options (in thousands) $ 39 $ 90 Restricted Stock Awards and Units The activity related to the Company's RSAs for the six months ended June 30, 2017 is as follows: Shares Weighted Average Grant Date Fair Value Unvested balance at January 1, 2017 2,030,028 $ 9.69 Granted 727,272 $ 6.86 Vested (633,917 ) $ 9.53 Forfeited (14,083 ) $ 14.71 Unvested balance at June 30, 2017 2,109,300 $ 8.73 The activity related to the Company's RSUs for the six months ended June 30, 2017 is as follows: Shares Weighted Average Grant Date Fair Value Unvested balance at January 1, 2017 110,219 $ 11.95 Granted — $ — Vested (25,661 ) $ 11.28 Forfeited (11,064 ) $ 8.34 Unvested balance at June 30, 2017 73,494 $ 12.72 The total fair value of shares of restricted stock granted under RSAs and RSUs that vested during the six months ended June 30, 2017 was $6.3 million . Performance-Based Stock Units The activity related to the Company's PSUs for the six months ended June 30, 2017 is as follows: Shares Weighted Average Grant Date Fair Value Unvested balance at January 1, 2017 147,085 $ 12.11 Granted 165,000 $ 8.41 Vested (47,856 ) $ 13.04 Forfeited (10,060 ) $ 11.87 Unvested balance at June 30, 2017 254,169 $ 9.54 The total fair value of shares of restricted stock granted under PSUs that vested during the six months ended June 30, 2017 was $0.6 million . The Company did not have outstanding PSAs during the six months ended June 30, 2017 or at December 31, 2016. Employee Stock Purchase Plan The Company's ESPP provides for six -month offering periods with the purchase price of the stock equal to 85% of the lesser of the market price on the first or last day of the offering period. The maximum number of shares of common stock an employee may purchase during each offering period is 500 , subject to certain adjustments pursuant to the ESPP. Stock-Based Compensation The condensed consolidated statements of operations include stock-based compensation for the three and six months ended June 30, 2017 and 2016 as follows (in thousands): Three months ended Six months ended June 30, June 30, June 30, June 30, Product cost of revenue $ 87 $ 93 $ 186 $ 164 Service cost of revenue 261 322 578 654 Research and development 1,238 1,210 2,555 2,389 Sales and marketing 907 1,224 819 2,244 General and administrative 1,744 1,792 3,362 3,605 $ 4,237 $ 4,641 $ 7,500 $ 9,056 During the three months ended March 31, 2017, the Company reversed $1.0 million of incremental expense to correct an error in 2016 related to the acceleration of certain stock awards held by an executive who separated from the Company in 2016. Management had reviewed and considered the impact of the error and determined that it was not material to the Company's consolidated financial results for the third and fourth quarters of 2016, as well as the 2016 fiscal year. Management has also determined that the correction of this error is not material to the results of operations for the 2017 completed reporting periods. There is no income tax benefit for employee stock-based compensation expense for the six months ended June 30, 2017 or June 30, 2016 due to the valuation allowance recorded. At June 30, 2017 , there was $19.2 million , net of expected forfeitures, of unrecognized stock-based compensation expense related to unvested stock options, awards, units and ESPP shares. This expense is expected to be recognized over a weighted average period of approximately two years .

MAJOR CUSTOMERS

MAJOR CUSTOMERS	6 Months Ended
	Jun. 30, 2017
Risks and Uncertainties [Abstract]
MAJOR CUSTOMERS	MAJOR CUSTOMERS The following customers contributed 10% or more of the Company's revenue in at least one of the three or six month periods ended June 30, 2017 and June 30, 2016 : Three months ended Six months ended June 30, June 30, June 30, June 30, Verizon Communications Inc. 12% 13% 14% * AT&T Inc. 12% 16% * 14% Level 3 Communications * * * 11% _______________________ * Represents less than 10% of revenue At June 30, 2017 , two customers accounted for 10% or more of the Company's accounts receivable balance, representing approximately 28% of the Company's accounts receivable balance in the aggregate. At December 31, 2016 , no customer accounted for 10% or more of the Company's accounts receivable balance. The Company performs ongoing credit evaluations of its customers and generally does not require collateral on accounts receivable. The Company maintains an allowance for doubtful accounts and such losses have been within management's expectations.

GEOGRAPHIC INFORMATION

GEOGRAPHIC INFORMATION	6 Months Ended
	Jun. 30, 2017
Segment Reporting [Abstract]
GEOGRAPHIC INFORMATION	GEOGRAPHIC INFORMATION The Company's classification of revenue by geographic area is determined by the location to which the product is shipped or where the services are performed. The following table summarizes revenue by geographic area as a percentage of total revenue: Three months ended Six months ended June 30, June 30, June 30, June 30, United States 69 % 70 % 68 % 69 % Europe, Middle East and Africa 13 13 12 13 Japan 9 8 12 11 Other Asia Pacific 5 6 4 5 Other 4 3 4 2 100 % 100 % 100 % 100 % International revenue, both as a percentage of total revenue and absolute dollars, may vary from one period to the next, and accordingly, historical data may not be indicative of future periods.

INCOME TAXES

INCOME TAXES	6 Months Ended
	Jun. 30, 2017
Income Tax Disclosure [Abstract]
INCOME TAXES	INCOME TAXES The Company's income tax provisions for the six months ended June 30, 2017 and 2016 reflect the Company's estimates of the effective rates expected to be applicable for the respective full years, adjusted for any discrete events, which are recorded in the period that they occur. These estimates are reevaluated each quarter based on the Company's estimated tax expense for the full year. The estimated effective rates for the six months ended June 30, 2017 and 2016 do not include any benefit for the Company's domestic losses, as the Company has concluded that a valuation allowance on any domestic benefit is required. Included in the Company's provision for the six months ended June 30, 2016 is a discrete charge of $0.7 million related to an uncertain tax position of the Company's subsidiary in France.

COMMITMENTS AND CONTINGENCIES

COMMITMENTS AND CONTINGENCIES	6 Months Ended
	Jun. 30, 2017
Commitments and Contingencies Disclosure [Abstract]
COMMITMENTS AND CONTINGENCIES	COMMITMENTS AND CONTINGENCIES On July 19, 2017, Taqua Holdings, LLC ("Holdings") filed a lawsuit against the Company, GENBAND, Taqua and several of the Company's merger-related subsidiaries and GENBAND Holdings' merger-related holding companies (collectively, the "Holdings Lawsuit Defendants") in Texas state court, District of Dallas County (Case No. DC-17-08630) based on the parties' Earn-Out Agreement (the "Holdings Complaint") which expressly provides that the Company is to have "the absolute right and sole and absolute discretion to operate and otherwise make decisions with respect to the conduct of the Business." The lawsuit alleges that: (i) the Company purportedly breached the Earn-Out Agreement by implementing a restructuring plan, the Taqua Restructuring Initiative, that was allegedly intended to undermine Taqua's business and the COmpany's payment obligation; and (ii) the Company purportedly acquired Taqua for the purpose of eliminating Taqua as a competitor before the Company's pending merger with GENBAND (the "GENBAND Merger"), and that the Company never intended to promote Taqua products. The Holdings Complaint purports to seek monetary damages for the Company's alleged breach of the Earn-Out Agreement (which is described in Note 2 of this Quarterly Report on Form 10-Q and a copy of which is filed as Exhibit 10.31 to the Company's Annual Report on Form 10-K for the year ended December 31, 2016) and an injunction of both the Taqua Restructuring Initiative and the GENBAND Merger. The Holdings Lawsuit Defendants believe Holdings' allegations are without merit and intend to contest the lawsuit vigorously. The Company intends to respond that, among other things: (i) the Earn-Out Agreement contains an explicit dispute resolution and arbitration clause that does not permit lawsuits except where pre-arbitral injunctive relief is sought; and (ii) no injunctive relief is available in this case because: (x) the plaintiff failed to act and the Taqua Restructuring Initiative is complete; and (y) the plaintiff's earn-out claim, if successful, is inherently a claim for which money damages are available. Further, the Company intends to vigorously defend and to countersue on the grounds that this lawsuit is an unjustified attempt by Holdings to avoid two escrow-related claims totaling over $700,000 made by the Company against escrow funds established pursuant to the purchase agreement. The Company does not expect the results of this suit to have a material adverse effect on its business or consolidated financial statements. On April 6, 2015, Ming Huang, a purported shareholder of the Company, filed a Class Action Complaint (Civil Action No. 3:15-02407), alleging violations of the federal securities laws (the "Complaint") in the United States District Court for the District of New Jersey (the "District of New Jersey"), against the Company and two of its officers, Raymond P. Dolan, the Company's President and Chief Executive Officer, and Mark T. Greenquist, the Company's former Chief Financial Officer (collectively, the "Defendants"). On September 21, 2015, in response to motions subsequently filed with the District of New Jersey by four other purported shareholders of the Company seeking status as lead plaintiff, the District of New Jersey appointed Richard Sousa as lead plaintiff (the "Plaintiff"). The Plaintiff claims to represent purchasers of the Company's common stock during the period from October 23, 2014 to March 24, 2015, and seeks unspecified damages. The principal allegation contained in the Complaint is that the Defendants made misleading forward-looking statements concerning the Company's fiscal first quarter of 2015 financial performance. On September 22, 2015, the Company filed a Motion to Transfer (the “Motion to Transfer”) this case to the United States District Court for the District of Massachusetts (the "District of Massachusetts"). On March 21, 2016, the District of New Jersey granted the Company's Motion to Transfer. On May 4, 2016, the Plaintiff filed an amended complaint (the "Amended Complaint") (Civil Action No. 1:16-cv-10657-GAO). On June 20, 2016, the Company and the other Defendants filed a Motion to Dismiss the Amended Complaint (the "Motion to Dismiss") and on July 25, 2016, the Plaintiff filed an opposition to the Motion to Dismiss. The Company filed its reply to the Plaintiff's opposition to the Motion to Dismiss on August 15, 2016. A hearing on the Motion to Dismiss was held on February 28, 2017. On June 7, 2017, the District of Massachusetts granted the Defendants' Motion to Dismiss, with prejudice, and no appeal was filed, ending the litigation. The Company is also fully cooperating with an SEC inquiry regarding the development and issuance of the Company's first quarter 2015 revenue and earnings guidance. At this time, it is not possible to predict the outcome of the SEC's inquiry, including whether or not any proceedings will be initiated or, if so, when or how the matter will be resolved, and therefore an estimate of the possible range of loss, if any, cannot be made. In addition, the Company is often a party to disputes and legal proceedings that it considers routine and incidental to its business. Management does not expect the results of any of these actions to have a material effect on the Company's business or consolidated financial statements.

BASIS OF PRESENTATION (Policies

BASIS OF PRESENTATION (Policies)	6 Months Ended
	Jun. 30, 2017
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation In the opinion of management, the accompanying unaudited condensed consolidated financial statements include all adjustments, consisting only of normal recurring items, necessary for their fair presentation with accounting principles generally accepted in the United States of America ("GAAP") and with the rules and regulations of the U.S. Securities and Exchange Commission ("SEC"). Interim results are not necessarily indicative of results for a full year or any future interim period. The information included in this Quarterly Report on Form 10-Q should be read in conjunction with the Company's Annual Report on Form 10-K for the year ended December 31, 2016 (the "Annual Report"), which was filed with the SEC on February 27, 2017.
Principles of Consolidation	Principles of Consolidation The condensed consolidated financial statements include the accounts of Sonus and its wholly-owned subsidiaries. Intercompany transactions and balances have been eliminated in consolidation.
Use of Estimates and Judgments	Use of Estimates and Judgments The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reporting periods. Significant estimates and judgments relied upon in preparing these consolidated financial statements include accounting for business combinations, revenue recognition for multiple element arrangements, inventory valuations, assumptions used to determine the fair value of stock-based compensation, intangible assets and goodwill valuations, including impairments, legal contingencies and recoverability of Sonus' net deferred tax assets and the related valuation allowances. Sonus regularly assesses these estimates and records changes in estimates in the period in which they become known. Sonus bases its estimates on historical experience and various other assumptions that it believes to be reasonable under the circumstances. Actual results could differ from those estimates.
Fair Value of Financial Instruments	Fair Value of Financial Instruments The carrying amounts of the Company's financial instruments, which include cash equivalents, marketable securities, investments, accounts receivable, accounts payable and other long-term liabilities, approximate their fair values.
Operating Segments	Operating Segments The Company operates in a single segment. Operating segments are identified as components of an enterprise about which separate discrete financial information is available for evaluation by the chief operating decision maker in making decisions regarding resource allocation and assessing performance. To date, the chief operating decision maker has made such decisions and assessed performance at the company level, as one segment. The Company's chief operating decision maker is its President and Chief Executive Officer.
Recent Accounting Pronouncements	Recent Accounting Pronouncements In May 2017, the Financial Accounting Standards Board ("FASB") issued Accounting Standards Update ("ASU") 2017-09, Compensation - Stock Compensation (Topic 718): Scope of Modification Accounting ("ASU 2017-09"), which amends the scope of modification accounting for share-based payment arrangements. ASU 2017-09 provides guidance on the types of changes to the terms or conditions of share-based payment awards to which an entity would be required to apply modification accounting under Accounting Standards Codification ("ASC") 718. Specifically, an entity would not apply modification accounting if the fair value, vesting conditions and classification of the awards are the same immediately before and after the modification. ASU 2017-09 is effective for the Company beginning January 1, 2018 for both interim and annual reporting periods, with early adoption permitted. The Company does not expect the adoption of ASU 2017-09 will have a material impact on its consolidated financial statements. In January 2017, the FASB issued ASU 2017-04, Intangibles - Goodwill and Other (Topic 350): Simplifying the Test for Goodwill Impairment ("ASU 2017-04"), which removes the requirement to compare the implied fair value of goodwill with its carrying amount as part of step two of the goodwill impairment test. As a result, under ASU 2017-04, an entity should perform its annual, or interim, goodwill impairment test by comparing the fair value of a reporting unit with its carrying amount and should recognize an impairment charge for the amount by which the carrying amount exceeds the reporting unit's fair value; however, the loss recognized should not exceed the total amount of goodwill allocated to that reporting unit. In addition, ASU 2017-04 clarifies the requirements for excluding and allocating foreign currency translation adjustments to reporting units in connection with an entity's testing of reporting units for goodwill impairment; clarifies that an entity should consider income tax effects from any tax-deductible goodwill on the carrying amount of the reporting unit when measuring the goodwill impairment loss, if applicable; and makes minor changes to other related guidance within the ASC. ASU 2017-04 is effective prospectively for the Company beginning January 15, 2020, with early adoption permitted for interim or annual goodwill impairment tests performed on testing dates after January 1, 2017. The Company elected to early-adopt ASU 2017-04 as of January 1, 2017; such early adoption did not have a material impact on the Company's consolidated financial results. In October 2016, the FASB issued ASU 2016-16, Income Taxes (Topic 740): Intra-Entity Transfers of Assets Other Than Inventory ("ASU 2016-16"), which removes the prohibition in ASC 740, Income Taxes, against the immediate recognition of the current and deferred income tax effects of intra-entity transfers of assets other than inventory. ASU 2016-16 is intended to reduce the complexity of GAAP and diversity in practice related to the tax consequences of certain types of intra-entity asset transfers, particularly those involving intellectual property. ASU 2016-16 is effective for the Company beginning January 1, 2019 for both interim and annual reporting periods. The Company does not believe that the adoption of ASU 2016-16 will have a material impact on its consolidated financial statements. In August 2016, the FASB issued ASU 2016-15, Statement of Cash Flows (Topic 230): Classification of Certain Cash Receipts and Cash Payments ("ASU 2016-15"), which amends the guidance in ASC 230 on the classification of certain cash receipts and payments in the statement of cash flows. The primary purpose of ASU 2016-15 is to reduce the diversity in practice that has resulted from the lack of consistent principles on this topic. ASU 2016-15 adds or clarifies guidance on eight cash flow issues, including debt prepayment or debt extinguishment costs, settlement of zero-coupon debt instruments or certain other debt instruments, contingent consideration payments made after a business combination, proceeds from the settlement of insurance claims, proceeds from the settlement of corporate-owned life insurance policies, distributions received from equity method investees, beneficial interests in securitization transactions and separately identifiable cash flows and application of the predominance principle. ASU 2016-15 is effective for the Company beginning January 1, 2018 for both interim and annual reporting periods, with early adoption permitted. Entities must apply the guidance retrospectively to all periods presented but may apply it prospectively from the earliest date practicable if retrospective application would be impracticable. The Company does not expect the adoption of ASU 2016-15 will have a material impact on its consolidated financial statements. In June 2016, the FASB issued ASU 2016-13, Financial Instruments - Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instrument s ("ASU 2016-13"), which adds an impairment model that is based on expected losses rather than incurred losses. Under ASU 2016-13, an entity recognizes as an allowance its estimate of expected credit losses, which the FASB believes will result in more timely recognition of such losses. ASU 2016-13 is effective for the Company beginning January 1, 2020 for both interim and annual reporting periods, with early adoption permitted. The Company does not expect the adoption of ASU 2016-13 will have a material impact on its consolidated financial statements. In March 2016, the FASB issued ASU 2016-09, Compensation - Stock Compensation (Topic 718): Improvements to Employee Share-Based Payment Accounting ("ASU 2016-09"), which simplifies several aspects of the accounting for employee share-based payment transactions, including the accounting for income taxes, forfeitures and statutory tax withholding requirements, as well as classification in the statement of cash flows. ASU 2016-09 became effective for the Company beginning January 1, 2017 for both interim and annual reporting periods. Under ASU 2016-09, the Company will now recognize unrealized excess tax benefits. Due to the Company's full valuation allowance on its federal and state income taxes, the adoption of ASU 2016-09 did not have a material impact on the Company's accounting for income taxes. Without the valuation allowance, the Company would have recognized an increased deferred tax asset approximating $5 million . The Company has elected to continue to apply forfeiture rates to its expense attribution related to stock options, restricted stock awards and restricted stock units, as the Company believes that such continued application results in more accurate expense attribution over the life of these equity grants. The adoption of ASU 2016-09 did not have a material impact on the Company's consolidated financial statements. In February 2016, the FASB issued ASU 2016-02, Leases (Topic 842) Section A - Leases: Amendments to the FASB Accounting Standards Codification ("ASU 2016-02"), its new standard on accounting for leases. ASU 2016-02 introduces a lessee model that brings most leases onto the balance sheet. The new standard also aligns many of the underlying principles of the new lessor model with those in ASC 606, the FASB's new revenue recognition standard (i.e., those related to evaluating when profit can be recognized). Furthermore, ASU 2016-02 addresses other concerns related to the current leases model. For example, ASU 2016-02 eliminates the current GAAP requirement for an entity to use bright-line tests in determining lease classification. ASU 2016-02 is effective for the Company for both interim and annual periods beginning January 1, 2019. The Company is currently assessing the potential impact of the adoption of ASU 2016-02 on its consolidated financial statements. In July 2015, the FASB issued ASU 2015-11, Simplifying the Measurement of Inventory ("ASU 2015-11"), which simplifies the measurement of inventory by requiring entities to measure most inventory at the lower of cost and net realizable value, replacing the previous requirement to measure most inventory at the lower of cost or market. ASU 2015-11 does not apply to inventories that are measured by using either the last-in, first-out method or the retail inventory method. ASU 2015-11 became effective for the Company for both interim and annual reporting periods beginning January 1, 2017. The adoption of ASU 2015-11 did not have a material impact on the Company's consolidated financial statements. In May 2014, the FASB issued ASU 2014-09, Revenue from Contracts with Customers (“ASU 2014-09”), its final standard on revenue from contracts with customers, along with additional ASUs which, among other things, clarified the implementation of the new revenue guidance and delayed the adoption by one year, to January 1, 2018 (collectively, the "New Revenue Standard"). The New Revenue Standard outlines a single comprehensive model for entities to use in accounting for revenue arising from contracts with customers and supersedes most current revenue recognition guidance, including industry-specific guidance. The core principle of the revenue model is that an entity recognizes revenue to depict the transfer of promised goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services. In applying the revenue model to contracts within its scope, an entity identifies the contract(s) with a customer, identifies the performance obligations in the contract, determines the transaction price, allocates the transaction price to the performance obligations in the contract and recognizes revenue when (or as) the entity satisfies a performance obligation. The New Revenue Standard applies to all contracts with customers that are within the scope of other topics in the ASC. Certain of the New Revenue Standard's provisions also apply to transfers of nonfinancial assets, including in-substance nonfinancial assets that are not an output of an entity’s ordinary activities (i.e., property, plant and equipment; real estate; or intangible assets). Existing accounting guidance applicable to these transfers has been amended or superseded. The Company continues to assess the potential impact of the adoption of the New Revenue Standard on its consolidated financial statements, and currently believes that such adoption will, in general, accelerate the recognition of revenue (i.e., more revenue will be recognized upon delivery than is currently recognized ratably or upon payment) compared to the current standards in effect, in particular, sales of software-only products and sales to customers currently accounted for on a cash basis. The Company currently expects to adopt the New Revenue Standard using the modified retrospective option, and is in the process of updating its revenue recognition software to comply with the New Revenue Standard. The Company expects to begin parallel testing in the third quarter of 2017.

BUSINESS ACQUISITION (Tables)

BUSINESS ACQUISITION (Tables)	6 Months Ended
	Jun. 30, 2017
Business Combinations [Abstract]
Schedule of Recognized Identified Assets Acquired and Liabilities Assumed	A summary of the final allocation of the purchase consideration for Taqua is as follows (in thousands): Fair value of consideration transferred: Cash, net of cash acquired $ 19,919 Fair value of assets acquired and liabilities assumed: Current assets $ 3,347 Property and equipment 1,478 Intangible assets: Developed technology 2,100 Customer relationships 9,510 Goodwill 9,581 Other noncurrent assets 23 Current liabilities (5,435 ) Long-term liabilities (685 ) $ 19,919

EARNINGS (LOSS) PER SHARE (Tabl

EARNINGS (LOSS) PER SHARE (Tables)	6 Months Ended
	Jun. 30, 2017
Earnings Per Share [Abstract]
Schedule of calculations of shares used to compute basic and diluted earnings (loss) per share	The calculations of shares used to compute basic and diluted loss per share are as follows (in thousands): Three months ended Six months ended June 30, June 30, June 30, June 30, Weighted average shares outstanding—basic 49,543 49,423 49,330 49,453 Potential dilutive common shares — — — — Weighted average shares outstanding—diluted 49,543 49,423 49,330 49,453

CASH EQUIVALENTS AND INVESTME25

CASH EQUIVALENTS AND INVESTMENTS (Tables)	6 Months Ended
	Jun. 30, 2017
Investments, All Other Investments [Abstract]
Schedule of amortized cost, gross unrealized gains and losses and fair value of marketable debt and equity securities and investments	The amortized cost, gross unrealized gains and losses and fair value of the Company's marketable debt securities and investments at June 30, 2017 and December 31, 2016 were comprised of the following (in thousands): June 30, 2017 Amortized cost Unrealized gains Unrealized losses Fair value Cash equivalents $ 7,669 $ — $ — $ 7,669 Marketable securities Municipal obligations $ 1,091 $ — $ — $ 1,091 U.S. government agency notes 23,866 — (39 ) 23,827 Corporate debt securities 28,693 — (44 ) 28,649 Certificates of deposit 1,226 — — 1,226 $ 54,876 $ — $ (83 ) $ 54,793 Investments U.S. government agency notes $ 16,590 $ — $ (44 ) $ 16,546 Corporate debt securities 16,664 5 (33 ) 16,636 Certificates of deposit 5,341 — — 5,341 $ 38,595 $ 5 $ (77 ) $ 38,523 December 31, 2016 Amortized cost Unrealized gains Unrealized losses Fair value Cash equivalents $ 6,619 $ — $ — $ 6,619 Marketable securities Municipal obligations $ 3,264 $ — $ (3 ) $ 3,261 U.S. government agency notes 16,477 3 (3 ) 16,477 Corporate debt securities 41,893 4 (45 ) 41,852 Certificates of deposit 246 — — 246 $ 61,880 $ 7 $ (51 ) $ 61,836 Investments U.S. government agency notes $ 19,473 $ 3 $ (39 ) $ 19,437 Corporate debt securities 10,520 — (44 ) 10,476 Certificates of deposit 2,458 — — 2,458 $ 32,451 $ 3 $ (83 ) $ 32,371
Schedule of fair value of financial assets	The following table shows the fair value of the Company's financial assets at June 30, 2017 and December 31, 2016 . These financial assets are comprised of the Company's available-for-sale debt securities and reported under the captions Cash and cash equivalents, Marketable securities and Investments in the condensed consolidated balance sheets (in thousands): Fair value measurements at Total carrying Quoted prices in active markets (Level 1) Significant other observable inputs (Level 2) Significant unobservable inputs (Level 3) Cash equivalents $ 7,669 $ 7,669 $ — $ — Marketable securities Municipal obligations $ 1,091 $ — $ 1,091 $ — U.S. government agency notes 23,827 — 23,827 — Corporate debt securities 28,649 — 28,649 — Certificates of deposit 1,226 — 1,226 — $ 54,793 $ — $ 54,793 $ — Investments U.S. government agency notes $ 16,546 $ — $ 16,546 $ — Corporate debt securities 16,636 — 16,636 — Certificates of deposit 5,341 — 5,341 — $ 38,523 $ — $ 38,523 $ — Fair value measurements at Total carrying Quoted prices in active markets (Level 1) Significant other observable inputs (Level 2) Significant unobservable inputs (Level 3) Cash equivalents $ 6,619 $ 6,619 $ — $ — Marketable securities Municipal obligations $ 3,261 $ — $ 3,261 $ — U.S. government agency notes 16,477 — 16,477 — Corporate debt securities 41,852 — 41,852 — Certificates of deposit 246 — 246 — $ 61,836 $ — $ 61,836 $ — Investments U.S. government agency notes $ 19,437 $ — $ 19,437 $ — Corporate debt securities 10,476 — 10,476 — Certificates of deposit 2,458 — 2,458 — $ 32,371 $ — $ 32,371 $ —

INVENTORY (Tables)

INVENTORY (Tables)	6 Months Ended
	Jun. 30, 2017
Inventory Disclosure [Abstract]
Schedule of inventory	Inventory at June 30, 2017 and December 31, 2016 consists of the following (in thousands): June 30, December 31, On-hand final assemblies and finished goods inventories $ 15,935 $ 15,346 Deferred cost of goods sold 2,824 4,237 18,759 19,583 Less current portion (16,759 ) (18,283 ) Noncurrent portion (included in Other assets) $ 2,000 $ 1,300

INTANGIBLE ASSETS AND GOODWILL

INTANGIBLE ASSETS AND GOODWILL (Tables)	6 Months Ended
	Jun. 30, 2017
Goodwill and Intangible Assets Disclosure [Abstract]
Schedule of intangible assets	The Company's intangible assets at June 30, 2017 and December 31, 2016 consist of the following (dollars in thousands): June 30, 2017 Weighted average amortization period (years) Cost Accumulated amortization Net carrying value Developed technology 6.54 $ 34,980 $ 19,620 $ 15,360 Customer relationships 5.78 19,540 9,255 10,285 Internal use software 3.00 730 730 — 6.23 $ 55,250 $ 29,605 $ 25,645 December 31, 2016 Weighted average amortization period (years) Cost Accumulated amortization Net carrying value Developed technology 6.54 $ 34,980 $ 16,453 $ 18,527 Customer relationships 5.78 19,540 7,870 11,670 Internal use software 3.00 730 730 — 6.23 $ 55,250 $ 25,053 $ 30,197
Schedule of amortization expense related to intangible assets	Amortization expense for intangible assets for the three and six months ended June 30, 2017 and 2016 was as follows (in thousands): Three months ended Six months ended Statement of operations classification June 30, June 30, June 30, June 30, Developed technology $ 1,601 $ 1,455 $ 3,167 $ 3,082 Cost of revenue - product Customer relationships 692 318 1,385 637 Sales and marketing $ 2,293 $ 1,773 $ 4,552 $ 3,719
Schedule of estimated future amortization expense for intangible assets	Estimated future amortization expense for the Company's intangible assets at June 30, 2017 is as follows (in thousands): Years ending December 31, Remainder of 2017 $ 4,587 2018 6,615 2019 5,608 2020 4,166 2021 2,395 Thereafter 2,274 $ 25,645
Schedule of goodwill	The changes in the carrying value of the Company's goodwill in the six months ended June 30, 2017 were as follows (in thousands): Balance at January 1, 2017 Goodwill $ 52,499 Accumulated impairment losses (3,106 ) 49,393 Purchase accounting adjustments - Taqua 498 Balance at June 30, 2017 $ 49,891 Balance at June 30, 2017 Goodwill $ 52,997 Accumulated impairment losses (3,106 ) $ 49,891

ACCRUED EXPENSES (Tables)

ACCRUED EXPENSES (Tables)	6 Months Ended
	Jun. 30, 2017
Payables and Accruals [Abstract]
Schedule of accrued expenses	Accrued expenses at June 30, 2017 and December 31, 2016 consist of the following (in thousands): June 30, December 31, Employee compensation and related costs $ 11,715 $ 15,879 Other 6,898 10,007 $ 18,613 $ 25,886

RESTRUCTURING ACCRUAL (Tables)

RESTRUCTURING ACCRUAL (Tables)	6 Months Ended
	Jun. 30, 2017
Restructuring and Related Activities [Abstract]
Summary of restructuring accrual activity	A summary of the 2016 Restructuring Initiative accrual activity for the six months ended June 30, 2017 is as follows (in thousands): Balance at Initiatives Adjustments for changes in estimate Cash Balance at Severance $ 497 $ 405 $ (26 ) $ (763 ) $ 113 Facilities — 126 — (3 ) 123 $ 497 $ 531 $ (26 ) $ (766 ) $ 236 A summary of the 2015 Restructuring Initiative accrual activity for the six months ended June 30, 2017 is as follows (in thousands): Balance at Initiatives Adjustments for changes in estimate Cash Balance at Severance $ 168 $ — $ — $ (168 ) $ — A summary of the Taqua Restructuring Initiative accrual activity for the six months ended June 30, 2017 is as follows (in thousands): Balance at Initiatives Adjustments for changes in estimate Cash Balance at Severance $ 384 $ 245 $ (49 ) $ (569 ) $ 11 Facilities 218 370 — (190 ) 398 $ 602 $ 615 $ (49 ) $ (759 ) $ 409

STOCK-BASED COMPENSATION PLANS

STOCK-BASED COMPENSATION PLANS (Tables)	6 Months Ended
	Jun. 30, 2017
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Schedule of activity related to outstanding stock options	The activity related to the Company's outstanding stock options for the six months ended June 30, 2017 is as follows: Number of Shares Weighted Average Exercise Price Weighted Average Remaining Contractual Term (years) Aggregate Intrinsic Value (in thousands) Outstanding at January 1, 2017 5,610,106 $ 15.73 Granted 5,200 $ 6.46 Exercised (21,815 ) $ 4.13 Forfeited (27,665 ) $ 14.32 Expired (154,043 ) $ 19.31 Outstanding at June 30, 2017 5,411,783 $ 15.67 4.88 $ 168 Vested or expected to vest at June 30, 2017 5,378,996 $ 15.69 4.86 $ 163 Exercisable at June 30, 2017 4,954,545 $ 15.76 4.63 $ 137
Schedule of assumptions used to estimate the fair value of options at the date of grant using the Black-Scholes option pricing model	The grant date fair values of options to purchase common stock granted in the three and six months ended June 30, 2017 were estimated using the Black-Scholes valuation model with the following assumptions: Three months ended Six months ended June 30, June 30, Risk-free interest rate 1.81% 1.81% - 1.95% Expected dividends — — Weighted average volatility 51.4% 51.3% Expected life (years) 5.0 5.0
Schedule of stock options, additional information	Additional information regarding the Company's stock options for the three and six months ended June 30, 2017 is as follows: Three months ended Six months ended June 30, June 30, Weighted average grant date fair value of stock options granted $ 3.48 $ 2.98 Total intrinsic value of stock options exercised (in thousands) $ 25 $ 62 Cash received from the exercise of stock options (in thousands) $ 39 $ 90
Schedule of activity related to unvested restricted stock grants	The activity related to the Company's RSAs for the six months ended June 30, 2017 is as follows: Shares Weighted Average Grant Date Fair Value Unvested balance at January 1, 2017 2,030,028 $ 9.69 Granted 727,272 $ 6.86 Vested (633,917 ) $ 9.53 Forfeited (14,083 ) $ 14.71 Unvested balance at June 30, 2017 2,109,300 $ 8.73 The activity related to the Company's RSUs for the six months ended June 30, 2017 is as follows: Shares Weighted Average Grant Date Fair Value Unvested balance at January 1, 2017 110,219 $ 11.95 Granted — $ — Vested (25,661 ) $ 11.28 Forfeited (11,064 ) $ 8.34 Unvested balance at June 30, 2017 73,494 $ 12.72
Schedule of activity related to performance stock awards	The activity related to the Company's PSUs for the six months ended June 30, 2017 is as follows: Shares Weighted Average Grant Date Fair Value Unvested balance at January 1, 2017 147,085 $ 12.11 Granted 165,000 $ 8.41 Vested (47,856 ) $ 13.04 Forfeited (10,060 ) $ 11.87 Unvested balance at June 30, 2017 254,169 $ 9.54
Schedule of stock-based compensation expenses which are included in condensed consolidated statement of operations	The condensed consolidated statements of operations include stock-based compensation for the three and six months ended June 30, 2017 and 2016 as follows (in thousands): Three months ended Six months ended June 30, June 30, June 30, June 30, Product cost of revenue $ 87 $ 93 $ 186 $ 164 Service cost of revenue 261 322 578 654 Research and development 1,238 1,210 2,555 2,389 Sales and marketing 907 1,224 819 2,244 General and administrative 1,744 1,792 3,362 3,605 $ 4,237 $ 4,641 $ 7,500 $ 9,056

MAJOR CUSTOMERS (Tables)

MAJOR CUSTOMERS (Tables)	6 Months Ended
	Jun. 30, 2017
Risks and Uncertainties [Abstract]
Schedule of customers contributing 10% or more of the revenue	The following customers contributed 10% or more of the Company's revenue in at least one of the three or six month periods ended June 30, 2017 and June 30, 2016 : Three months ended Six months ended June 30, June 30, June 30, June 30, Verizon Communications Inc. 12% 13% 14% * AT&T Inc. 12% 16% * 14% Level 3 Communications * * * 11% _______________________ * Represents less than 10% of revenue

GEOGRAPHIC INFORMATION (Tables)

GEOGRAPHIC INFORMATION (Tables)	6 Months Ended
	Jun. 30, 2017
Segment Reporting [Abstract]
Summary of revenue by geographic area as a percentage of total revenue	The Company's classification of revenue by geographic area is determined by the location to which the product is shipped or where the services are performed. The following table summarizes revenue by geographic area as a percentage of total revenue: Three months ended Six months ended June 30, June 30, June 30, June 30, United States 69 % 70 % 68 % 69 % Europe, Middle East and Africa 13 13 12 13 Japan 9 8 12 11 Other Asia Pacific 5 6 4 5 Other 4 3 4 2 100 % 100 % 100 % 100 %

BASIS OF PRESENTATION - Narrati

BASIS OF PRESENTATION - Narrative (Details) $ in Millions	May 23, 2017USD ($)	Jun. 30, 2017USD ($)segment
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Number of reportable operating segments | segment		1
Accounting Standards Update 2016-09 [Member]
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Deferred income taxes		$ 5
GENBAND Holdings Company
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Repayment, long term debt	$ 45
Repayment, management fees	10.3
Repayment promissory note	22.5
Repayment, transaction fees	$ 9
Solstice Sapphire Investments, Inc
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Percentage of voting interest acquired	50.00%
GENBAND Holdings Company and two related holding companies
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Percentage of voting interest acquired	50.00%

BUSINESS ACQUISITION - Narrativ

BUSINESS ACQUISITION - Narrative Taqua LLC Acquisition (Details) - USD ($)	Sep. 26, 2016	Jun. 30, 2017	Dec. 31, 2016	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016	Dec. 31, 2016
Business Acquisition [Line Items]
Cash, net of cash acquired					$ 0	$ 750,000
Goodwill		$ 49,891,000	$ 49,393,000	$ 40,310,000	49,891,000	40,310,000	$ 49,393,000
Acquisition-related expenses		4,679,000		$ 0	4,735,000	$ 0
Taqua, LLC [Member]
Business Acquisition [Line Items]
Cash, net of cash acquired	$ 19,919,000
Contingent consideration estimate	10,000,000				0		$ 0
Goodwill	9,581,000
Increase to current liabilities		400,000
Increase to noncurrent liabilities		$ 100,000
Reversal of previously recorded contingent consideration			10,000,000
Reduction to goodwill			2,200,000
Acquisition-related expenses					$ 56,000
Taqua, LLC [Member] | Developed technology [Member]
Business Acquisition [Line Items]
Increase (decrease) in intangible assets			(12,100,000)
Taqua, LLC [Member] | Customer Relationships [Member]
Business Acquisition [Line Items]
Increase (decrease) in intangible assets			$ 5,500,000
Maximum [Member] | Taqua, LLC [Member]
Business Acquisition [Line Items]
Contingent consideration estimate	$ 65,000,000

BUSINESS ACQUISITION - Summary

BUSINESS ACQUISITION - Summary of Taquq LLC Acquisition (Details) - USD ($) $ in Thousands	Sep. 26, 2016	Jun. 30, 2017	Jun. 30, 2016	Dec. 31, 2016
Business Acquisition [Line Items]
Cash, net of cash acquired		$ 0	$ 750
Current assets	$ 3,347
Goodwill		$ 49,891	$ 40,310	$ 49,393
Taqua, LLC [Member]
Business Acquisition [Line Items]
Cash, net of cash acquired	19,919
Property and equipment	1,478
Goodwill	9,581
Other noncurrent assets	23
Current liabilities	(5,435)
Long-term liabilities	(685)
Total Assets and Liabilities, Net	19,919
Developed technology [Member] | Taqua, LLC [Member]
Business Acquisition [Line Items]
Intangible assets	2,100
Customer Relationships [Member] | Taqua, LLC [Member]
Business Acquisition [Line Items]
Intangible assets	$ 9,510

EARNINGS (LOSS) PER SHARE - (De

EARNINGS (LOSS) PER SHARE - (Details) - shares shares in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Reconciliation of weighted average shares outstanding from basic to diluted
Weighted average shares outstanding - basic	49,543	49,423	49,330	49,453
Potential dilutive common shares	0	0	0	0
Weighted average shares outstanding - diluted	49,543	49,423	49,330	49,453
Common stock and unvested shares of restricted stock not included because their effect would have been antidilutive (in shares)	8,000	8,700

CASH EQUIVALENTS AND INVESTME37

CASH EQUIVALENTS AND INVESTMENTS - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
	Jun. 30, 2016	Jun. 30, 2017
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities sold	$ 3,800
Available-for-sale securities, gross realized gains	$ 18
Minimum [Member]
Schedule of Available-for-sale Securities [Line Items]
Period considered to classify available-for-sale securities as investments		1 year
Maximum [Member]
Schedule of Available-for-sale Securities [Line Items]
Period considered to classify available-for-sale securities as investments		2 years

CASH EQUIVALENTS AND INVESTME38

CASH EQUIVALENTS AND INVESTMENTS - Schedule of Activity for Short-Term Investments (Detail) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Amortized cost, gross unrealized gains and losses and fair value of marketable debt and equity securities and investments
Cash equivalents, amortized cost	$ 7,669	$ 6,619
Cash equivalents, fair value	7,669	6,619
Marketable securities, amortized cost	54,876	61,880
Marketable securities, unrealized gains	0	7
Marketable securities, unrealized losses	(83)	(51)
Marketable securities, fair value	54,793	61,836
Investments, amortized cost	38,595	32,451
Investments, unrealized gains	5	3
Investments, unrealized losses	(77)	(83)
Investments, fair value	38,523	32,371
Municipal obligations [Member]
Amortized cost, gross unrealized gains and losses and fair value of marketable debt and equity securities and investments
Marketable securities, amortized cost	1,091	3,264
Marketable securities, unrealized gains	0	0
Marketable securities, unrealized losses	0	(3)
Marketable securities, fair value	1,091	3,261
U.S. government agency notes [Member]
Amortized cost, gross unrealized gains and losses and fair value of marketable debt and equity securities and investments
Marketable securities, amortized cost	23,866	16,477
Marketable securities, unrealized gains	0	3
Marketable securities, unrealized losses	(39)	(3)
Marketable securities, fair value	23,827	16,477
Investments, amortized cost	16,590	19,473
Investments, unrealized gains	0	3
Investments, unrealized losses	(44)	(39)
Investments, fair value	16,546	19,437
Corporate debt securities [Member]
Amortized cost, gross unrealized gains and losses and fair value of marketable debt and equity securities and investments
Marketable securities, amortized cost	28,693	41,893
Marketable securities, unrealized gains	0	4
Marketable securities, unrealized losses	(44)	(45)
Marketable securities, fair value	28,649	41,852
Investments, amortized cost	16,664	10,520
Investments, unrealized gains	5	0
Investments, unrealized losses	(33)	(44)
Investments, fair value	16,636	10,476
Certificates of deposit [Member]
Amortized cost, gross unrealized gains and losses and fair value of marketable debt and equity securities and investments
Marketable securities, amortized cost	1,226	246
Marketable securities, unrealized gains	0	0
Marketable securities, unrealized losses	0	0
Marketable securities, fair value	1,226	246
Investments, amortized cost	5,341	2,458
Investments, unrealized gains	0	0
Investments, unrealized losses	0	0
Investments, fair value	$ 5,341	$ 2,458

CASH EQUIVALENTS AND INVESTME39

CASH EQUIVALENTS AND INVESTMENTS - Schedule of Short-Term Investments by Measurement (Detail) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Cash and cash equivalents, Marketable securities and Investments
Cash equivalents, fair value	$ 7,669	$ 6,619
Marketable securities, fair value	54,793	61,836
Investments, fair value	38,523	32,371
Total carrying value [Member]
Cash and cash equivalents, Marketable securities and Investments
Cash equivalents, fair value	7,669	6,619
Marketable securities, fair value	54,793	61,836
Investments, fair value	38,523	32,371
Quoted prices in active markets (Level 1) [Member]
Cash and cash equivalents, Marketable securities and Investments
Cash equivalents, fair value	7,669	6,619
Marketable securities, fair value	0	0
Investments, fair value	0	0
Significant other observable inputs (Level 2) [Member]
Cash and cash equivalents, Marketable securities and Investments
Cash equivalents, fair value	0	0
Marketable securities, fair value	54,793	61,836
Investments, fair value	38,523	32,371
Significant unobservable inputs (Level 3) [Member]
Cash and cash equivalents, Marketable securities and Investments
Cash equivalents, fair value	0	0
Marketable securities, fair value	0	0
Investments, fair value	0	0
Municipal obligations [Member] | Total carrying value [Member]
Cash and cash equivalents, Marketable securities and Investments
Marketable securities, fair value	1,091	3,261
Municipal obligations [Member] | Quoted prices in active markets (Level 1) [Member]
Cash and cash equivalents, Marketable securities and Investments
Marketable securities, fair value	0	0
Municipal obligations [Member] | Significant other observable inputs (Level 2) [Member]
Cash and cash equivalents, Marketable securities and Investments
Marketable securities, fair value	1,091	3,261
Municipal obligations [Member] | Significant unobservable inputs (Level 3) [Member]
Cash and cash equivalents, Marketable securities and Investments
Marketable securities, fair value	0	0
U.S. government agency notes [Member] | Total carrying value [Member]
Cash and cash equivalents, Marketable securities and Investments
Marketable securities, fair value	23,827	16,477
Investments, fair value	16,546	19,437
U.S. government agency notes [Member] | Quoted prices in active markets (Level 1) [Member]
Cash and cash equivalents, Marketable securities and Investments
Marketable securities, fair value	0	0
Investments, fair value	0	0
U.S. government agency notes [Member] | Significant other observable inputs (Level 2) [Member]
Cash and cash equivalents, Marketable securities and Investments
Marketable securities, fair value	23,827	16,477
Investments, fair value	16,546	19,437
U.S. government agency notes [Member] | Significant unobservable inputs (Level 3) [Member]
Cash and cash equivalents, Marketable securities and Investments
Marketable securities, fair value	0	0
Investments, fair value	0	0
Corporate debt securities [Member] | Total carrying value [Member]
Cash and cash equivalents, Marketable securities and Investments
Marketable securities, fair value	28,649	41,852
Investments, fair value	16,636	10,476
Corporate debt securities [Member] | Quoted prices in active markets (Level 1) [Member]
Cash and cash equivalents, Marketable securities and Investments
Marketable securities, fair value	0	0
Investments, fair value	0	0
Corporate debt securities [Member] | Significant other observable inputs (Level 2) [Member]
Cash and cash equivalents, Marketable securities and Investments
Marketable securities, fair value	28,649	41,852
Investments, fair value	16,636	10,476
Corporate debt securities [Member] | Significant unobservable inputs (Level 3) [Member]
Cash and cash equivalents, Marketable securities and Investments
Marketable securities, fair value	0	0
Investments, fair value	0	0
Certificates of deposit [Member] | Total carrying value [Member]
Cash and cash equivalents, Marketable securities and Investments
Marketable securities, fair value	1,226	246
Investments, fair value	5,341	2,458
Certificates of deposit [Member] | Quoted prices in active markets (Level 1) [Member]
Cash and cash equivalents, Marketable securities and Investments
Marketable securities, fair value	0	0
Investments, fair value	0	0
Certificates of deposit [Member] | Significant other observable inputs (Level 2) [Member]
Cash and cash equivalents, Marketable securities and Investments
Marketable securities, fair value	1,226	246
Investments, fair value	5,341	2,458
Certificates of deposit [Member] | Significant unobservable inputs (Level 3) [Member]
Cash and cash equivalents, Marketable securities and Investments
Marketable securities, fair value	0	0
Investments, fair value	$ 0	$ 0

INVENTORY - (Details)

INVENTORY - (Details) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Inventory Disclosure [Abstract]
On-hand final assemblies and finished goods inventories	$ 15,935	$ 15,346
Deferred cost of goods sold	2,824	4,237
Gross inventory	18,759	19,583
Less current portion	(16,759)	(18,283)
Inventory, Noncurrent	$ 2,000	$ 1,300

INTANGIBLE ASSETS AND GOODWIL41

INTANGIBLE ASSETS AND GOODWILL - (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016	Dec. 31, 2016
Intangible Assets And Goodwill
Weighted average amortization period (years)			6 years 2 months 22 days		6 years 2 months 22 days
Cost	$ 55,250		$ 55,250		$ 55,250
Accumulated amortization	29,605		29,605		25,053
Net carrying value	25,645		25,645		$ 30,197
Amortization expense	2,293	$ 1,773	4,552	$ 3,719
Estimated future amortization expense for intangible assets
Remainder of 2017	4,587		4,587
2,018	6,615		6,615
2,019	5,608		5,608
2,020	4,166		4,166
2,021	2,395		2,395
Thereafter	2,274		2,274
Total	25,645		$ 25,645
Developed technology [Member]
Intangible Assets And Goodwill
Weighted average amortization period (years)			6 years 6 months 15 days		6 years 6 months 15 days
Cost	34,980		$ 34,980		$ 34,980
Accumulated amortization	19,620		19,620		16,453
Net carrying value	15,360		15,360		$ 18,527
Amortization expense	1,601	1,455	$ 3,167	3,082
Customer Relationships [Member]
Intangible Assets And Goodwill
Weighted average amortization period (years)			5 years 9 months 12 days		5 years 9 months 12 days
Cost	19,540		$ 19,540		$ 19,540
Accumulated amortization	9,255		9,255		7,870
Net carrying value	10,285		10,285		$ 11,670
Amortization expense	692	$ 318	$ 1,385	$ 637
Internal use software [Member]
Intangible Assets And Goodwill
Weighted average amortization period (years)			3 years		3 years
Cost	730		$ 730		$ 730
Accumulated amortization	730		730		730
Net carrying value	$ 0		$ 0		$ 0

INTANGIBLE ASSETS AND GOODWIL42

INTANGIBLE ASSETS AND GOODWILL - (Details 2) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2017	Jun. 30, 2017	Dec. 31, 2016	Sep. 26, 2016	Jun. 30, 2016
Goodwill [Roll Forward]
Goodwill		$ 52,997	$ 52,499		$ 43,416
Accumulated impairment losses		(3,106)	(3,106)		(3,106)
Goodwill, beginning of period	$ 49,891	$ 49,891	$ 49,393		$ 40,310
Goodwill, end of period	49,891
Taqua, LLC [Member]
Goodwill [Roll Forward]
Goodwill, beginning of period				$ 9,581
Acquisition	$ 498

ACCRUED EXPENSES - (Details)

ACCRUED EXPENSES - (Details) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Payables and Accruals [Abstract]
Employee compensation and related costs	$ 11,715	$ 15,879
Other	6,898	10,007
Total	$ 18,613	$ 25,886

RESTRUCTURING ACCRUAL - Narrati

RESTRUCTURING ACCRUAL - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended		8 Months Ended	12 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2017	Dec. 31, 2016
Restructuring Cost and Reserve [Line Items]
Restructuring	$ 501	$ 0	$ 1,071	$ 0
Restructuring reserve	600		600		$ 600	$ 600	$ 1,300
2016 Restructuring [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring	300		531			2,000
Restructuring reserve	236		236		236	236	497
Taqua Restructuring Incentive [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring			615		1,800
Restructuring reserve	409		409		409	409	602
Employee Severance [Member] | 2016 Restructuring [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring	200		405			1,900
Restructuring reserve	113		113		113	113	497
Employee Severance [Member] | Taqua Restructuring Incentive [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring	200		245		1,200
Restructuring reserve	11		11		11	11	384
Facility Closing [Member] | 2016 Restructuring [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring	100		126			100
Restructuring reserve	123		123		123	123	0
Facility Closing [Member] | Taqua Restructuring Incentive [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring			370		600
Restructuring reserve	398		398		398	398	218
Other Noncurrent Liabilities [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring reserve	$ 300		$ 300		$ 300	$ 300	$ 62

RESTRUCTURING ACCRUAL - Rollfor

RESTRUCTURING ACCRUAL - Rollforward (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended		8 Months Ended	12 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2017
Restructuring Reserve [Roll Forward]
Balance at the beginning of the period			$ 1,300
Initiatives charged to expense	$ 501	$ 0	1,071	$ 0
Balance at the end of the period	600		600		$ 600	$ 600
2016 Restructuring [Member]
Restructuring Reserve [Roll Forward]
Balance at the beginning of the period			497
Initiatives charged to expense	300		531			2,000
Adjustments for changes in estimate			(26)
Cash payments			(766)
Balance at the end of the period	236		236		236	236
Taqua Restructuring Incentive [Member]
Restructuring Reserve [Roll Forward]
Balance at the beginning of the period			602
Initiatives charged to expense			615		1,800
Adjustments for changes in estimate			(49)
Cash payments			(759)
Balance at the end of the period	409		409		409	409
Employee Severance [Member] | 2016 Restructuring [Member]
Restructuring Reserve [Roll Forward]
Balance at the beginning of the period			497
Initiatives charged to expense	200		405			1,900
Adjustments for changes in estimate			(26)
Cash payments			(763)
Balance at the end of the period	113		113		113	113
Employee Severance [Member] | Taqua Restructuring Incentive [Member]
Restructuring Reserve [Roll Forward]
Balance at the beginning of the period			384
Initiatives charged to expense	200		245		1,200
Adjustments for changes in estimate			(49)
Cash payments			(569)
Balance at the end of the period	11		11		11	11
Employee Severance [Member] | 2015 Restructuring [Member]
Restructuring Reserve [Roll Forward]
Balance at the beginning of the period			168
Initiatives charged to expense			0
Adjustments for changes in estimate			0
Cash payments			(168)
Balance at the end of the period	0		0		0	0
Facility Closing [Member] | 2016 Restructuring [Member]
Restructuring Reserve [Roll Forward]
Balance at the beginning of the period			0
Initiatives charged to expense	100		126			100
Adjustments for changes in estimate			0
Cash payments			(3)
Balance at the end of the period	123		123		123	123
Facility Closing [Member] | Taqua Restructuring Incentive [Member]
Restructuring Reserve [Roll Forward]
Balance at the beginning of the period			218
Initiatives charged to expense			370		600
Adjustments for changes in estimate			0
Cash payments			(190)
Balance at the end of the period	$ 398		$ 398		$ 398	$ 398

COMMON STOCK REPURCHASES (Detai

COMMON STOCK REPURCHASES (Details) - USD ($)	6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jul. 29, 2013
Class of Stock [Line Items]
Payments for repurchase of common stock	$ 0	$ 4,980,000
Stock repurchased and retired during period (in shares)	0	600,000
Remaining authorized repurchase amount	$ 5,400,000
Common Stock [Member]
Class of Stock [Line Items]
Stock buyback program authorized amount			$ 100,000,000
Stock Buyback Program [Member]
Class of Stock [Line Items]
Payments for repurchase of common stock		$ 5,000,000

STOCK-BASED COMPENSATION PLAN47

STOCK-BASED COMPENSATION PLANS - (Details)	Apr. 01, 2017shares	Mar. 31, 2017executiveshares	Mar. 16, 2017shares	Apr. 01, 2016executiveshares	Mar. 16, 2015executiveshares	Feb. 28, 2017executiveshares	Jun. 30, 2017USD ($)$ / sharesshares	Jun. 30, 2016USD ($)	Jun. 30, 2017USD ($)$ / sharesshares	Jun. 30, 2016USD ($)	Dec. 31, 2015executive	Jun. 09, 2017shares	Dec. 31, 2016shares
Stock-based compensation
Stock authorized for issuance (in shares)							120,000,000		120,000,000				120,000,000
Common stock, capital shares held, conversion ratio												1.50
Range of assumptions used in estimating fair value of options
Cash received from the exercise of stock options (in dollars) | $									$ 90,000	$ 15,000
Weighted average grant-date fair value
Stock-based compensation (in dollars) | $							$ 4,237,000	$ 4,641,000	7,500,000	9,056,000
Tax benefit from stock based compensation expense | $									0	0
Fair value of the assumed awards attributable to future stock-based compensation expense | $							19,200,000		$ 19,200,000
Expected period for unrecognized expense									2 years
Product cost of revenue [Member]
Weighted average grant-date fair value
Stock-based compensation (in dollars) | $							87,000	93,000	$ 186,000	164,000
Service cost of revenue [Member]
Weighted average grant-date fair value
Stock-based compensation (in dollars) | $							261,000	322,000	578,000	654,000
Research and development [Member]
Weighted average grant-date fair value
Stock-based compensation (in dollars) | $							1,238,000	1,210,000	2,555,000	2,389,000
Sales and marketing [Member]
Weighted average grant-date fair value
Stock-based compensation (in dollars) | $							907,000	1,224,000	819,000	2,244,000
General and Administrative Expense [Member]
Weighted average grant-date fair value
Stock-based compensation (in dollars) | $							$ 1,744,000	$ 1,792,000	$ 3,362,000	$ 3,605,000
Performance Share Units [Member]
Change in unvested restricted stock awards
Unvested balance at the beginning of the period (in shares)									147,085
Granted (in shares)									165,000
Vested (in shares)									(47,856)
Forfeited (in shares)									(10,060)
Unvested balance at the end of the period (in shares)							254,169		254,169
Weighted average grant-date fair value
Unvested balance at the end of the period (in dollars per share) | $ / shares									$ 12.11
Granted (in dollars per share) | $ / shares									8.41
Vested (in dollars per share) | $ / shares									13.04
Forfeited (in dollars per share) | $ / shares									11.87
Unvested balance at end of the period (in dollars per share) | $ / shares							$ 9.54		$ 9.54
Total fair value (in dollars) | $									$ 600,000
Stock Options [Member]
Number of shares
Outstanding at the beginning of the period (in shares)									5,610,106
Granted (in shares)									5,200
Exercised (in shares)									(21,815)
Forfeited (in shares)									(27,665)
Expired (in shares)									(154,043)
Outstanding at the end of the period (in shares)							5,411,783		5,411,783
Vested or expected to vest at the end of the period (in shares)							5,378,996		5,378,996
Exercisable at the end of the period (in shares)							4,954,545		4,954,545
Weighted average exercise price
Outstanding at the beginning of the period (in dollars per share) | $ / shares									$ 15.73
Granted (in dollars per share) | $ / shares									6.46
Exercised (in dollars per share) | $ / shares									4.13
Forfeited (in dollars per share) | $ / shares									14.32
Expired (in dollars per share) | $ / shares									19.31
Outstanding at the end of the period (in dollars per share) | $ / shares							$ 15.67		15.67
Vested or expected to vest at the end of the period (in dollars per share) | $ / shares							15.69		15.69
Exercisable at the end of the period (in dollars per share) | $ / shares							$ 15.76		$ 15.76
Weighted average remaining contractual life (in years)
Outstanding at the end of the period									4 years 10 months 17 days
Vested or expected to vest at the end of the period									4 years 10 months 10 days
Exercisable at the end of the period									4 years 7 months 18 days
Aggregate intrinsic value (in dollars)
Outstanding at the end of the period (in dollars) | $							$ 168,000		$ 168,000
Vested or expected to vest at the end of the period (in dollars) | $							163,000		163,000
Exercisable at the end of the period (in dollars) | $							$ 137,000		$ 137,000
Range of assumptions used in estimating fair value of options
Risk-free interest rate									1.95%
Expected dividends							0.00%		0.00%
Weighted average volatility							51.40%		51.30%
Expected life									5 years
Weighted average grant date fair value of stock options granted (in dollars per share) | $ / shares							$ 3.48		$ 2.98
Total intrinsic values of stock options exercised (in dollars) | $							$ 25,000		$ 62,000
Cash received from the exercise of stock options (in dollars) | $							$ 39,000		$ 90,000
Restricted stock awards [Member]
Change in unvested restricted stock awards
Unvested balance at the beginning of the period (in shares)									2,030,028
Granted (in shares)									727,272
Vested (in shares)									(633,917)
Forfeited (in shares)									(14,083)
Unvested balance at the end of the period (in shares)							2,109,300		2,109,300
Weighted average grant-date fair value
Unvested balance at the end of the period (in dollars per share) | $ / shares									$ 9.69
Granted (in dollars per share) | $ / shares									6.86
Vested (in dollars per share) | $ / shares									9.53
Forfeited (in dollars per share) | $ / shares									14.71
Unvested balance at end of the period (in dollars per share) | $ / shares							$ 8.73		$ 8.73
Total fair value (in dollars) | $									$ 6,300,000
Restricted Stock Units (RSUs) [Member]
Change in unvested restricted stock awards
Unvested balance at the beginning of the period (in shares)									110,219
Granted (in shares)									0
Vested (in shares)									(25,661)
Forfeited (in shares)									(11,064)
Unvested balance at the end of the period (in shares)							73,494		73,494
Weighted average grant-date fair value
Unvested balance at the end of the period (in dollars per share) | $ / shares									$ 11.95
Granted (in dollars per share) | $ / shares									0
Vested (in dollars per share) | $ / shares									11.28
Forfeited (in dollars per share) | $ / shares									8.34
Unvested balance at end of the period (in dollars per share) | $ / shares							$ 12.72		$ 12.72
Employee Stock [Member]
Weighted average grant-date fair value
Offering period									6 months
Purchase price of common stock (percentage)									85.00%
Maximum number of shares purchasable per employee									500
2017 Performance Share Units [Member] | Performance Share Units [Member]
Stock-based compensation
Number of executives granted shares | executive		5
Change in unvested restricted stock awards
Granted (in shares)		165,000
2017 Performance Share Units [Member] | Performance Share Units [Member] | Share-based Compensation Award, Tranche One [Member]
Stock-based compensation
Vesting percentage		33.33%
2017 Performance Share Units [Member] | Performance Share Units [Member] | Share-based Compensation Award, Tranche Two [Member]
Stock-based compensation
Vesting percentage		33.33%
2017 Performance Share Units [Member] | Performance Share Units [Member] | Share-based Compensation Award, Tranche Three [Member]
Stock-based compensation
Vesting percentage		33.33%
2016 Performance Share Units [Member] | Performance Share Units [Member]
Stock-based compensation
Number of executives granted shares | executive				6		4
Percent of performance metrics achieved						90.40%
Change in unvested restricted stock awards
Granted (in shares)				131,250
Vested (in shares)						(24,106)
Forfeited (in shares)			(2,560)
2016 Performance Share Units [Member] | Performance Share Units [Member] | Share-based Compensation Award, Tranche One [Member]
Stock-based compensation
Vesting percentage				33.33%
2016 Performance Share Units [Member] | Performance Share Units [Member] | Share-based Compensation Award, Tranche Two [Member]
Stock-based compensation
Vesting percentage				33.33%
2016 Performance Share Units [Member] | Performance Share Units [Member] | Share-based Compensation Award, Tranche Three [Member]
Stock-based compensation
Vesting percentage				33.33%
2015 Performance Share Units [Member] | Performance Share Units [Member]
Stock-based compensation
Number of executives granted shares | executive					8	4					2
Percent of performance metrics achieved						76.00%
Change in unvested restricted stock awards
Granted (in shares)					131,250
Vested (in shares)						(23,750)
Forfeited (in shares)	(7,500)
2015 Performance Share Units [Member] | Performance Share Units [Member] | Share-based Compensation Award, Tranche One [Member]
Stock-based compensation
Vesting percentage					33.33%
2015 Performance Share Units [Member] | Performance Share Units [Member] | Share-based Compensation Award, Tranche Two [Member]
Stock-based compensation
Vesting percentage					33.33%
2015 Performance Share Units [Member] | Performance Share Units [Member] | Share-based Compensation Award, Tranche Three [Member]
Stock-based compensation
Vesting percentage					33.33%
Restatement Adjustment [Member] | Sales and marketing [Member]
Weighted average grant-date fair value
Stock-based compensation (in dollars) | $									$ (1,000,000)
Common Stock [Member]
Stock-based compensation
Stock authorized for issuance (in shares)												900,000

MAJOR CUSTOMERS - (Details)

MAJOR CUSTOMERS - (Details) - customer	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016	Dec. 31, 2016
Revenue [Member] | Less than [Member]
MAJOR CUSTOMERS
Threshold percentage			10.00%
Revenue [Member] | Customer [Member] | Verizon Communications[Member]
MAJOR CUSTOMERS
Concentration risk, percentage	12.00%	13.00%	14.00%
Revenue [Member] | Customer [Member] | AT&T [Member]
MAJOR CUSTOMERS
Concentration risk, percentage	12.00%	16.00%		14.00%
Revenue [Member] | Customer [Member] | Level 3 Communications [Member]
MAJOR CUSTOMERS
Concentration risk, percentage				11.00%
Accounts receivable balance [Member]
MAJOR CUSTOMERS
Threshold percentage			10.00%
Accounts receivable balance [Member] | Customer [Member]
MAJOR CUSTOMERS
Concentration risk, percentage			28.00%
Number of major customers	2		2		0

GEOGRAPHIC INFORMATION - Summar

GEOGRAPHIC INFORMATION - Summary of Revenue by Geographic Area as a Percentage of Total Revenue (Details) - Revenue [Member] - Geographical area [Member]	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Revenue by geographic area and by customer
Percentage of total revenue	100.00%	100.00%	100.00%	100.00%
United States [Member]
Revenue by geographic area and by customer
Percentage of total revenue	69.00%	70.00%	68.00%	69.00%
Europe, Middle East and Africa [Member]
Revenue by geographic area and by customer
Percentage of total revenue	13.00%	13.00%	12.00%	13.00%
Japan [Member]
Revenue by geographic area and by customer
Percentage of total revenue	9.00%	8.00%	12.00%	11.00%
Other Asia Pacific [Member]
Revenue by geographic area and by customer
Percentage of total revenue	5.00%	6.00%	4.00%	5.00%
Other [Member]
Revenue by geographic area and by customer
Percentage of total revenue	4.00%	3.00%	4.00%	2.00%

INCOME TAXES - (Details)

INCOME TAXES - (Details) $ in Millions	6 Months Ended
	Jun. 30, 2016USD ($)
Income Tax Disclosure [Abstract]
Discrete charge related to an uncertain tax position	$ 0.7

COMMITMENTS AND CONTINGENCIES (

COMMITMENTS AND CONTINGENCIES (Details)	Jul. 19, 2017USD ($)	Sep. 21, 2015shareholder	Apr. 06, 2015officer
Loss Contingencies [Line Items]
Number of officers listed as defendants | officer			2
Number of shareholders seeking plaintiff status | shareholder		4
Subsequent Event [Member] | Case No. DC - 17 - 08630 [Member]
Loss Contingencies [Line Items]
Escrow related claims | $	$ 700,000