Ribbon Communications Inc - Ordinary Shares 10-Q 30 Jul 15 2015 Q2 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	6 Months Ended
	Jun. 26, 2015	Jul. 23, 2015
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	Large Accelerated Filer
Document Type	10-Q
Document Period End Date	Jun. 26, 2015
Document Fiscal Year Focus	2,015
Document Fiscal Period Focus	Q2
Amendment Flag	false
Entity Common Stock, Shares Outstanding		49,586,313
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	Jun. 26, 2015	Dec. 31, 2014
Current assets:
Cash and cash equivalents	$ 34,128	$ 41,157
Marketable securities	64,542	64,443
Accounts receivable, net of allowance for doubtful accounts of $60 at June 26, 2015 and $58 at December 31, 2014	48,654	62,943
Inventory	25,699	22,114
Deferred income taxes	1,001	991
Other current assets	17,450	15,239
Total current assets	191,474	206,887
Property and equipment, net	15,473	17,845
Intangible assets, net	29,956	22,594
Goodwill	40,310	39,263
Investments	14,851	42,407
Deferred income taxes	1,012	1,043
Other assets	2,326	2,596
Total assets	295,402	332,635
Current liabilities:
Accounts payable	5,146	7,497
Accrued expenses	22,513	32,149
Current portion of deferred revenue	41,811	36,967
Current portion of long-term liabilities	711	794
Total current liabilities	70,181	77,407
Deferred revenue	7,652	8,009
Deferred income taxes	1,982	1,623
Other long-term liabilities	3,119	5,246
Total liabilities	$ 82,934	$ 92,285
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; 49,576,911 shares issued and outstanding at June 26, 2015; 49,357,033 shares issued and outstanding at December 31, 2014	50	49
Additional paid-in capital	1,233,013	1,226,226
Accumulated deficit	(1,026,049)	(991,347)
Accumulated other comprehensive income	5,454	5,422
Total stockholders' equity	212,468	240,350
Total liabilities and stockholders' equity	$ 295,402	$ 332,635

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Jun. 26, 2015	Dec. 31, 2014
Allowance for doubtful accounts	$ 60	$ 58
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	49,576,911	49,357,033
Common stock, shares outstanding	49,576,911	49,357,033

Consolidated Statements of Oper

Consolidated Statements of Operations - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 26, 2015	Jun. 27, 2014	Jun. 26, 2015	Jun. 27, 2014
Revenue:
Product	$ 27,042	$ 45,845	$ 51,907	$ 90,985
Service	27,659	29,725	52,939	55,327
Total revenue	54,701	75,570	104,846	146,312
Cost of revenue:
Product	11,269	16,811	22,917	30,474
Service	9,018	11,471	18,285	22,127
Total cost of revenue	20,287	28,282	41,202	52,601
Gross profit	34,414	47,288	63,644	93,711
Operating expenses:
Research and development	19,968	20,921	39,307	39,893
Sales and marketing	17,540	18,782	37,305	38,363
General and administrative	10,444	11,995	19,668	23,181
Acquisition-related	24	0	131	1,306
Restructuring	1,487	391	1,148	1,560
Total operating expenses	49,463	52,089	97,559	104,303
Loss from operations	(15,049)	(4,801)	(33,915)	(10,592)
Interest income (expense), net	(20)	50	8	85
Other income, net	5	(10)	50	2,325
Loss before income taxes	(15,064)	(4,761)	(33,857)	(8,182)
Income tax provision	(279)	(736)	(845)	(1,268)
Net loss	$ (15,343)	$ (5,497)	$ (34,702)	$ (9,450)
Loss per share:
Basic (in dollars per share)	$ (0.31)	$ (0.11)	$ (0.70)	$ (0.18)
Diluted (in dollars per share)	$ (0.31)	$ (0.11)	$ (0.70)	$ (0.18)
Shares used to compute loss per share:
Basic (in shares)	49,484	49,424	49,454	51,211
Diluted (in shares)	49,484	49,424	49,454	51,211

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Loss - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 26, 2015	Jun. 27, 2014	Jun. 26, 2015	Jun. 27, 2014
Statement of Comprehensive Income [Abstract]
Net loss	$ (15,343)	$ (5,497)	$ (34,702)	$ (9,450)
Other comprehensive income (loss), net of tax:
Foreign currency translation adjustments	(90)	(33)	(48)	61
Unrealized gain (loss) on available-for sale marketable securities, net of tax	(25)	(62)	80	(72)
Other comprehensive income (loss), net of tax	(115)	(95)	32	(11)
Comprehensive loss, net of tax	$ (15,458)	$ (5,592)	$ (34,670)	$ (9,461)

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	6 Months Ended
	Jun. 26, 2015	Jun. 27, 2014
Cash flows from operating activities:
Net loss	$ (34,702)	$ (9,450)
Adjustments to reconcile net loss to cash flows provided by operating activities:
Depreciation and amortization of property and equipment	6,902	5,899
Amortization of intangible assets	3,238	2,207
Stock-based compensation	11,629	12,712
Loss on disposal of property and equipment	22	61
Deferred income taxes	335	519
Changes in operating assets and liabilities:
Accounts receivable	14,223	8,254
Inventory	(3,590)	4,386
Other operating assets	(1,389)	2,698
Accounts payable	(1,994)	(620)
Accrued expenses and other long-term liabilities	(13,466)	(4,635)
Deferred revenue	4,524	(1,777)
Net cash (used in) provided by operating activities	(14,268)	20,254
Cash flows from investing activities:
Purchases of property and equipment	(4,524)	(6,271)
Business acquisition, net of cash acquired	(10,147)	(34,010)
Divestiture of business	0	2,000
Purchases of marketable securities	(3,737)	(47,880)
Maturities/sales of marketable securities	30,620	134,127
Net cash provided by investing activities	12,212	47,966
Cash flows from financing activities:
Proceeds from sale of common stock in connection with employee stock purchase plan	1,668	1,197
Proceeds from exercise of stock options	1,739	4,541
Payment of tax withholding obligations related to net share settlements of restricted stock awards	(2,164)	(1,571)
Repurchase of common stock	(6,084)	(83,518)
Principal payments of capital lease obligations	(41)	(44)
Net cash used in financing activities	(4,882)	(79,395)
Effect of exchange rate changes on cash and cash equivalents	(91)	47
Net decrease in cash and cash equivalents	(7,029)	(11,128)
Cash and cash equivalents, beginning of year	41,157	72,423
Cash and cash equivalents, end of period	34,128	61,295
Supplemental disclosure of cash flow information:
Interest paid	30	44
Income taxes paid	435	1,052
Income tax refunds received	311	28
Supplemental disclosure of non-cash investing activities:
Capital expenditures incurred, but not yet paid	343	147
Business acquisition purchase consideration - assumed equity awards	$ 0	$ 1,671

BASIS OF PRESENTATION

BASIS OF PRESENTATION	6 Months Ended
	Jun. 26, 2015
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 advance, protect and unify their communications and improve collaboration. 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") 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"), policy/routing servers, network intelligence applications (Network-as-a-Service ("NaaS") IQ), media and signaling gateways and network analytics tools. The Company utilizes both direct and indirect sales channels to reach its target customers. Customers and prospective customers in the service provider space are traditional and emerging communications service providers, including long distance carriers, local exchange carriers, Internet service providers, wireless operators, cable operators, international telephone companies and carriers that provide services to other carriers. Enterprise customers and target enterprise customers include financial institutions, retailers, state and local governments, and other multinational corporations. 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, 2014 (the "Annual Report") filed with the SEC on February 25, 2015. During the preparation of the Company's consolidated financial statements for the three month period ended June 26, 2015, the Company identified an error related to the historical foreign translation of depreciation expense on certain foreign fixed assets that resulted in a historical understatement of expense in prior fiscal years totaling $1.4 million on a cumulative basis. There is no tax effect on these expenses as the amounts were calculated in the appropriate foreign currencies. The Company does not believe this error is material to its previously issued historical consolidated financial statements for any of the periods impacted and accordingly, has not adjusted the historical financial statements. The Company has recorded the cumulative impact of the adjustment in the three months ended June 26, 2015. This adjustment resulted in a one-time $1.4 million overstatement of depreciation expense in both the three and six months ended June 26, 2015. The Company does not believe this adjustment is material to its condensed consolidated financial statements for either the three or six months ended June 26, 2015. The Company effected a one-for-five reverse stock split of its issued, outstanding and authorized common stock, which became effective as of the commencement of trading on the NASDAQ Global Select Market on January 30, 2015. Unless otherwise indicated, all references herein to shares outstanding and share issuances have been adjusted to give effect to the Company's January 2015 reverse stock split. On January 2, 2015 (the "Treq Asset Acquisition Date"), the Company acquired from Treq Labs, Inc. ("Treq") certain assets related to Treq's business of designing, developing, marketing, selling, servicing and maintaining software defined networking ("SDN") technology, SDN controller software and SDN management software (the "SDN Business"). The financial results of the SDN Business are included in the Company's condensed consolidated financial statements starting on the Treq Asset Acquisition Date. On February 19, 2014 (the "PT Acquisition Date"), the Company completed the acquisition of Performance Technologies, Incorporated ("PT"). The financial results of PT are included in the Company's condensed consolidated financial statements starting on the PT Acquisition Date. 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 the three or six months ended June 26, 2015. 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, convertible subordinated debt 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 April 2015, the Financial Accounting Standards Board ("FASB") issued Accounting Standards Update ("ASU") 2015-05, Customer's Accounting for Fees Paid in a Cloud Computing Arrangement ("ASU 2015-05"), which provides guidance on a customer's accounting for cloud computing costs. Under ASU 2015-05, a customer must determine whether a cloud computing arrangement contains a software license. If so, the customer would account for the fees related to the software license element in a manner consistent with how the acquisition of other software licenses is accounted for under Accounting Standards Codification ("ASC") 350-40, Intangibles - Goodwill and Other - Internal Use Software ("ASC 350-40"). If the arrangement does not contain a software license, the customer would account for cloud computing arrangements as service contracts. An arrangement would contain a software license element if both of the following criteria are met: (i) the customer has the contractual right to take possession of the software at any time during the hosting period without significant penalty; and (ii) it is feasible for the customer to either run the software on its own hardware or contract with another party unrelated to the vendor to host the software. ASU 2015-05 is effective for the Company for both annual and interim reporting beginning January 1, 2016. Early adoption is permitted. Entities may adopt the guidance either retrospectively or prospectively to arrangements entered into, or materially modified after the effective date. The Company is currently assessing the potential impact of the adoption of ASU 2015-05 on its consolidated financial statements. In April 2015, the FASB issued ASU 2015-03, Simplifying the Presentation of Debt Issuance Costs ("ASU 2015-03"). Under ASU 2015-03, an entity must present debt issuance costs on the balance sheet as a direct deduction from the related debt liability rather than as an asset. Amortization of the costs is reported as interest expense. ASU 2015-03 is effective for the Company for both annual and interim reporting beginning January 1, 2016. Early adoption is permitted. Entities must apply the new guidance retrospectively to all prior periods (i.e., the balance sheet for each period should be adjusted). The Company is currently assessing the potential impact of the adoption of ASU 2015-03 on its consolidated financial statements. In August 2014, the FASB issued ASU 2014-15, Disclosure of Uncertainties about an Entity's Ability to Continue as a Going Concern ("ASU 2014-15"). ASU 2014-15 provides guidelines determining when and how to disclose going concern uncertainties in the financial statements. The new standard requires management to perform interim and annual assessments of an entity's ability to continue as a going concern within one year of the date the financial statements are issued. An entity must provide certain disclosures if conditions or events raise substantial doubt about the entity's ability to continue as a going concern. ASU 2014-15is effective for the Company for annual periods ending after December 15, 2016, and interim periods thereafter, with early adoption permitted. The adoption of ASU 2014-15 is not expected to have a material impact on the Company's consolidated financial statements. In June 2014, the FASB issued ASU 2014-12, Compensation - Stock Compensation (Topic 718): Accounting for Share-Based Payments When the Terms of an Award Provide That a Performance Target Could Be Achieved after the Requisite Service Period (a consensus of the FASB Emerging Issues Task Force) (“ASU 2014-12”). ASU 2014-12 clarifies that entities should treat performance targets that can be met after the requisite service period of a share-based payment award as performance conditions that affect vesting. Therefore, an entity would not record compensation expense (measured as of the grant date without taking into account the effect of the performance target) related to an award for which transfer to the employee is contingent upon the entity’s satisfaction of a performance target until it becomes probable that the performance target will be met. ASU 2014-12 does not contain any new disclosure requirements. ASU 2014-12 is effective for the Company on January 1, 2016. The adoption of ASU 2014-12 is not expected to 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. ASU 2014-09 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. ASU 2014-09 applies to all contracts with customers that are within the scope of other topics in the FASB ASC. Certain of ASU 2014-09’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. In July 2015, the FASB decided to defer the original effective date of interim and annual reporting periods by one year. As a result, public entities would not be required to apply the new revenue standard until annual reporting periods beginning after December 15, 2017. The Company is currently assessing the potential impact of the adoption of ASU 2014-09 on its consolidated financial statements.

BUSINESS ACQUISITIONS

BUSINESS ACQUISITIONS	6 Months Ended
	Jun. 26, 2015
Business Combinations [Abstract]
BUSINESS ACQUISITIONS	BUSINESS ACQUISITIONS Treq Labs, Inc. On the Treq Asset Acquisition Date, the Company acquired from Treq its SDN Business. The SDN Business provides solutions that optimize networks for voice, video and UC for both enterprise and service provider customers. The Company believes that the acquisition of the SDN Business will accelerate Sonus' delivery of its SDN strategy. In consideration for the acquisition of the SDN Business, Sonus paid $10.1 million in cash at the Treq Asset Acquisition Date, with an additional consideration payment of $750,000 paid on July 2, 2015 and a second additional consideration payment of $750,000 due on January 4, 2016. The Company also entered into an Earn-Out Agreement, dated as of January 2, 2015, with Treq and Karl F. May, the seller representative in the transaction (the "Earn-Out Agreement"), under which the Company has agreed to issue up to an aggregate of 1.3 million shares of common stock over a three -year period subsequent to the Treq Asset Acquisition Date if aggregate revenue thresholds of at least $60 million are achieved by the SDN Business during that period, and up to an aggregate of an additional 2.2 million shares ( 3.5 million shares in total) if aggregate revenue thresholds of at least $150 million are achieved by the SDN Business during that period. If the initial revenue thresholds are not met, no shares will be issued. Based on historical and forecasted sales, no incremental contingent consideration was recorded either initially as of the Treq Asset Acquisition Date or through June 26, 2015. Any shares issued pursuant to the Earn-Out Agreement will be issued in reliance on the exemption from registration available under Section 4(a)(2) of the Securities Act of 1933, as amended (the "Securities Act") and will be subsequently registered for resale under the Securities Act by the Company. The transaction has been accounted for as a business combination. The Company finalized its valuation of the identifiable intangible assets in the second quarter of fiscal 2015. Based on the purchase price allocation, the Company recorded $1.0 million of goodwill, primarily due to expected synergies between the combined companies and expanded market opportunities. The goodwill is deductible for tax purposes. A summary of the purchase consideration for the SDN Business is as follows (in thousands): Fair value of consideration transferred: Cash, net of cash acquired $ 10,147 Unpaid purchase consideration 1,500 Fair value of total consideration $ 11,647 Fair value of assets acquired and liabilities assumed: Intangible assets: In-process research and development $ 9,100 Developed technology 1,500 Goodwill 1,047 $ 11,647 The valuation of the acquired intangible assets is inherently subjective and relies on significant unobservable inputs. The Company used an income approach to preliminarily value the acquired in-process research and development and developed technology 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 will begin to amortize the in-process research and development intangible asset at the time that the related products become generally available. Once the products become generally available, the Company will amortize 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 actual results of the SDN Business for the period since the Treq Asset Acquisition Date were not material to the Company's financial results. The Company has not provided pro forma information as the results of the SDN Business are not material to the Company's financial results. Performance Technologies, Incorporated On the PT Acquisition Date, the Company acquired all of the outstanding common stock of PT for cash consideration of $35.0 million , or $3.75 per share of PT common stock. This acquisition has enabled Sonus to expand its solutions portfolio with signaling technology and acquire expertise to enable mobile service providers to offer new real-time multimedia services through their mobile infrastructure. Delivering these services across the LTE next-generation mobile networks will require adoption of the next-generation signaling technology known in the industry as Diameter Signal. The acquisition of PT has allowed Sonus to diversify its product portfolio with an integrated, virtualized Diameter and SIP-based solution and deliver strategic value to service providers seeking to offer new multimedia services through mobile, cloud-based, real-time communications. The transaction has been accounted for as a business combination. The Company finalized the valuation of acquired assets, identifiable intangible assets and certain accrued liabilities in the fourth quarter of 2014. The Company recorded $8.8 million of goodwill, primarily due to expected synergies between the combined companies and expanded market opportunities. The goodwill is not deductible for tax purposes. A summary of the allocation of the purchase consideration for PT is as follows (in thousands): Fair value of consideration transferred: Cash, net of cash acquired $ 35,022 Fair value of equity awards assumed 1,671 Fair value of total consideration $ 36,693 Fair value of assets acquired and liabilities assumed: Marketable securities $ 2,315 Other current assets 9,337 Property and equipment 2,251 Intangible assets: Developed technology 13,200 Customer relationships 3,900 Goodwill 8,781 Current liabilities (2,762 ) Other long-term liabilities (329 ) $ 36,693 The valuation of the acquired intangible assets is inherently subjective and relies on significant unobservable inputs. The Company used an income approach to preliminarily value the acquired customer relationships and developed technology 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 contract renewal, 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 information as the results of PT are not material to the Company's financial results. 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 and services fees, such as legal, audit, consulting, paying agent and other fees. These expenses also include cash payments to certain former PT executives under their respective PT change of control agreements. The amounts recorded in the three and six months ended June 26, 2015 relate to professional fees in connection with the acquisition of the SDN Business. The amount recorded in the six months ended June 27, 2014 represents professional and services fees and expenses related to cash payments to certain former PT executives under their respective PT change of control agreements in connection with the PT acquisition. The Company did not record acquisition-related expense in the three months ended June 27, 2014. The components of acquisition-related costs included in the Company's results of operations for the three and six months ended June 26, 2015 and June 27, 2014 are as follows (in thousands): Three months ended Six months ended June 26, June 27, June 26, June 27, Professional and services fees $ 24 $ — $ 131 $ 1,057 Change of control agreements — — — 249 $ 24 $ — $ 131 $ 1,306 Sale of Multi-Protocol Server Business On June 20, 2014 (the "MPS Sale Date"), the Company sold its PT Multi-Protocol Server ("MPS") business for $2.0 million to an affiliate of Sunhillo Corporation, comprised of $0.2 million of inventory, $0.1 million of fixed assets, $0.2 million of deferred revenue and $1.9 million of PT goodwill allocable to the MPS business. The Company had acquired the MPS business in connection with the acquisition of PT. The results of operations of the MPS business are excluded from the Company's condensed consolidated results after the MPS Sale Date.

EARNINGS (LOSS) PER SHARE

EARNINGS (LOSS) PER SHARE	6 Months Ended
	Jun. 26, 2015
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 26, June 27, June 26, June 27, Weighted average shares outstanding—basic 49,484 49,424 49,454 51,211 Potential dilutive common shares — — — — Weighted average shares outstanding—diluted 49,484 49,424 49,454 51,211 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"), aggregating 8.9 million shares for the three and six months ended June 26, 2015 and 8.8 million shares for the three and six months ended June 27, 2014 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. 26, 2015
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 three months ended March 28, 2014, the Company sold $45.9 million of its available-for-sale securities and realized gross gains aggregating $46,000 , which are included as a component of Other income (expense), net in the Company's condensed consolidated statement of operations for the six months ended June 27, 2014. The Company did not realize any gross losses on these sales. In addition, $41.7 million of the Company's available-for-sale securities matured during the three months ended March 28, 2014 and were redeemed upon maturity. The Company did not sell any of its available-for-sale securities during the three or six months ended June 26, 2015 or the three months ended June 27, 2014. Investments with continuous unrealized losses for one year or greater at June 26, 2015 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 26, 2015 . The amortized cost, gross unrealized gains and losses and fair value of the Company's marketable debt securities and investments at June 26, 2015 and December 31, 2014 were comprised of the following (in thousands): June 26, 2015 Amortized cost Unrealized gains Unrealized losses Fair value Cash equivalents $ 10,345 $ — $ — $ 10,345 Marketable securities Municipal obligations $ 2,279 $ 1 $ — $ 2,280 U.S. government agency notes 2,150 1 — 2,151 Corporate debt securities 52,121 2 (48 ) 52,075 Commercial paper 5,086 — — 5,086 Certificates of deposit 2,950 — — 2,950 $ 64,586 $ 4 $ (48 ) $ 64,542 Investments Municipal obligations $ 1,435 $ 1 $ (2 ) $ 1,434 U.S. government agency notes 2,301 2 — 2,303 Corporate debt securities 11,133 — (19 ) 11,114 $ 14,869 $ 3 $ (21 ) $ 14,851 December 31, 2014 Amortized cost Unrealized gains Unrealized losses Fair value Cash equivalents $ 11,653 $ — $ — $ 11,653 Marketable securities Municipal obligations $ 1,273 $ 1 $ (1 ) $ 1,273 U.S. government agency notes 4,016 — — 4,016 Corporate debt securities 40,921 2 (59 ) 40,864 Commercial paper 9,340 — — 9,340 Certificates of deposit 8,950 — — 8,950 $ 64,500 $ 3 $ (60 ) $ 64,443 Investments Municipal obligations $ 2,702 $ 1 $ (3 ) $ 2,700 U.S. government agency notes 2,300 — (1 ) 2,299 Corporate debt securities 35,897 4 (86 ) 35,815 Commercial paper 1,093 — — 1,093 Certificates of deposit 500 — — 500 $ 42,492 $ 5 $ (90 ) $ 42,407 The Company's available-for-sale debt securities classified as Investments in the condensed consolidated balance sheets at June 26, 2015 and December 31, 2014 had maturity dates after one year but within 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 26, 2015 and December 31, 2014 . These financial assets are comprised of the Company's available-for-sale debt securities and reported under the captions Cash and cash equivalents, Short-term investments 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 $ 10,345 $ 10,345 $ — $ — Marketable securities Municipal obligations $ 2,280 $ — $ 2,280 $ — U.S. government agency notes 2,151 — 2,151 — Corporate debt securities 52,075 — 52,075 — Commercial paper 5,086 — 5,086 — Certificates of deposit 2,950 — 2,950 — $ 64,542 $ — $ 64,542 $ — Investments Municipal obligations $ 1,434 $ — $ 1,434 $ — U.S. government agency notes 2,303 — 2,303 — Corporate debt securities 11,114 — 11,114 — $ 14,851 $ — $ 14,851 $ — 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 $ 11,653 $ 11,653 $ — $ — Marketable securities Municipal obligations $ 1,273 $ — $ 1,273 $ — U.S. government agency notes 4,016 — 4,016 — Corporate debt securities 40,864 — 40,864 — Commercial paper 9,340 — 9,340 — Certificates of deposit 8,950 — 8,950 — $ 64,443 $ — $ 64,443 $ — Investments Municipal obligations $ 2,700 $ — $ 2,700 $ — U.S. government agency notes 2,299 — 2,299 — Corporate debt securities 35,815 — 35,815 — Commercial paper 1,093 — 1,093 — Certificates of deposit 500 — 500 — $ 42,407 $ — $ 42,407 $ — The Company's 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. 26, 2015
Inventory Disclosure [Abstract]
INVENTORY	INVENTORY Inventory consists of the following (in thousands): June 26, December 31, On-hand final assemblies and finished goods inventories $ 22,658 $ 19,285 Deferred cost of goods sold 3,041 2,829 $ 25,699 $ 22,114

INTANGIBLE ASSETS AND GOODWILL

INTANGIBLE ASSETS AND GOODWILL	6 Months Ended
	Jun. 26, 2015
Goodwill and Intangible Assets Disclosure [Abstract]
INTANGIBLE ASSETS AND GOODWILL	INTANGIBLE ASSETS AND GOODWILL The Company's intangible assets at June 26, 2015 and December 31, 2014 consist of the following (dollars in thousands): June 26, 2015 Weighted average amortization period (years) Cost Accumulated amortization Net carrying value In-process research and development 7.00 $ 9,100 $ — $ 9,100 Intellectual property 5.00 999 999 — Developed technology 6.24 23,780 7,416 16,364 Customer relationships 5.57 10,040 5,589 4,451 Internal use software 3.00 730 689 41 6.05 $ 44,649 $ 14,693 $ 29,956 December 31, 2014 Weighted average amortization period (years) Cost Accumulated amortization Net carrying value Intellectual property 5.00 $ 999 $ 999 $ — Developed technology 6.18 22,280 5,193 17,087 Customer relationships 5.57 10,040 4,695 5,345 Internal use software 3.00 730 568 162 5.75 $ 34,049 $ 11,455 $ 22,594 Amortization expense for intangible assets for the three and six months ended June 26, 2015 and June 27, 2014 was as follows (in thousands): Three months ended Six months ended Statement of operations classification June 26, June 27, June 26, June 27, Developed technology $ 1,116 $ 613 $ 2,223 $ 1,183 Cost of revenue - product Customer relationships 415 505 894 903 Sales and marketing Internal use software 60 60 121 121 Cost of revenue - product $ 1,591 $ 1,178 $ 3,238 $ 2,207 The Company has not recorded amortization expense in connection with the in-process research and development intangible assets because the related products are not yet generally available. The Company will begin to amortize the in-process research and development intangible assets at the time that the related products become generally available and will amortize the identifiable intangible assets in relation to the expected cash flows from the individual intangible assets over their respective useful lives, which the Company expects will occur over the next several quarters. Estimated future amortization expense for the Company's intangible assets at June 26, 2015 is as follows (in thousands): Years ending December 31, Remainder of 2015 $ 3,869 2016 7,189 2017 7,281 2018 4,644 2019 3,611 Thereafter 3,362 $ 29,956 The changes in the carrying value of the Company's goodwill in the six months ended June 26, 2015 and June 27, 2014 were as follows (in thousands): Balance at January 1, 2015 Goodwill $ 42,369 Accumulated impairment losses (3,106 ) 39,263 Acquisition of SDN Business 1,047 Balance at June 26, 2015 $ 40,310 Balance at June 26, 2015 Goodwill $ 43,416 Accumulated impairment losses (3,106 ) $ 40,310 Balance at January 1, 2014 Goodwill $ 35,485 Accumulated impairment losses (3,106 ) 32,379 Acquisition of PT 8,725 Sale of MPS business (1,897 ) Balance at June 27, 2014 $ 39,207 Balance at June 27, 2014 Goodwill $ 42,313 Accumulated impairment losses (3,106 ) $ 39,207

ACCRUED EXPENSES

ACCRUED EXPENSES	6 Months Ended
	Jun. 26, 2015
Payables and Accruals [Abstract]
ACCRUED EXPENSES	ACCRUED EXPENSES Accrued expenses consist of the following (in thousands): June 26, December 31, Employee compensation and related costs $ 9,647 $ 20,042 Other 12,866 12,107 $ 22,513 $ 32,149

RESTRUCTURING ACCRUAL

RESTRUCTURING ACCRUAL	6 Months Ended
	Jun. 26, 2015
Restructuring and Related Activities [Abstract]
RESTRUCTURING ACCRUAL	RESTRUCTURING ACCRUAL 2015 Restructuring Initiative To better align the Company's cost structure to its current revenue expectations, the Company recently announced a cost reduction review. As part of this review, on April 16, 2015, the Company initiated a restructuring plan to reduce its workforce by approximately 150 positions, or 12.5% of its worldwide workforce (the "2015 Restructuring Initiative"). In connection with the 2015 Restructuring Initiative, the Company recorded $2.9 million of restructuring expense for severance and related costs in the three months ended June 26, 2015. A summary of the 2015 Restructuring Initiative accrual activity for the six months ended June 26, 2015 is as follows (in thousands): 2015 Restructuring Initiative Balance at Initiatives Cash Balance at Severance $ — $ 2,899 $ (2,452 ) $ 447 The Company expects that the remaining amounts accrued under the 2015 Restructuring Initiative will be paid in the three months ending September 25, 2015. 2012 Restructuring Initiative On August 7, 2012, the Company announced that it had committed to a restructuring initiative to streamline operations and reduce operating costs by closing and consolidating certain facilities and reducing its worldwide workforce (the "2012 Restructuring Initiative"). The Company regularly reviews its restructuring accruals against expected cash expenditures to determine if adjustments are required. As a result of such reviews, the Company recorded credits to restructuring expense aggregating $1.8 million in the six months ended June 26, 2015. This amount is comprised of a credit of $1.4 million recorded in the three months ended June 26, 2015 in connection with a settlement with the landlord of the Company's Fremont, California facility to vacate the facility without penalty or future payments and a credit of $0.3 million recorded in the three months ended March 27, 2015. The amount reversed in the three months ended March 27, 2015 is comprised of approximately $272,000 for facilities in connection with a settlement with the landlord of the Company's Dulles, Virginia facility for an amount that was lower than had previously been accrued and approximately $67,000 in connection with changes in the amounts of severance ultimately paid to certain individuals. The Company recorded $1.2 million of restructuring expense in the three months ended June 27, 2014 and $1.6 million in the six months ended June 27, 2014 for severance and related costs in connection with reducing its workforce. A summary of the 2012 Restructuring Initiative accrual activity for the six months ended June 26, 2015 is as follows (in thousands): 2012 Restructuring Initiative Balance at Initiatives Adjustments for changes in estimate Cash Balance at Severance $ 1,682 $ — $ (67 ) $ (1,479 ) $ 136 Facilities 3,652 — (1,684 ) (1,514 ) 454 $ 5,334 $ — $ (1,751 ) $ (2,993 ) $ 590 The Company expects that the remaining amounts for severance accrued under the 2012 Restructuring Initiative will be paid in the fourth quarter of 2015 and the remaining amounts accrued for facilities will be paid in fiscal 2016. Balance Sheet Classification of Restructuring Accruals The current portion of the restructuring accrual is included as a component of Accrued expenses in the Company's condensed consolidated balance sheets. The portion of restructuring payments due more than one year from the balance sheet date is included in Other long-term liabilities in the Company's condensed consolidated balance sheets. The long-term portions of accrued restructuring were $0.2 million at June 26, 2015 and $1.9 million at December 31, 2014 .

DEBT

DEBT	6 Months Ended
	Jun. 26, 2015
Debt Disclosure [Abstract]
DEBT	DEBT The Company entered into 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 on June 27, 2014, which agreement was amended by a First Amendment to Credit Agreement on June 26, 2015 (the "Credit Agreement"). The Credit Agreement provides for a revolving credit facility of up to $15 million with a maturity date of June 30, 2016 and provides that the Company can select the interest rates under the credit facility from among the following options: (1) the Eurodollar Rate (which is defined as the rate per annum equal to the London Interbank Offered Rate plus 1.5% per annum) for a Eurodollar Rate Loan; and (2) the highest of (a) the Federal Funds Rate plus 1/2 of 1%, (b) the rate of interest in effect on the borrowing date as publicly announced from time to time by Bank of America as its prime rate, and (c) the monthly Eurodollar Rate plus 1% . The Credit Agreement also provides that the Company pays a 0.15% commitment fee on the unused commitments available for borrowing. The obligations of the Company under the Credit Agreement are guaranteed by Sonus International, Inc., Sonus Federal, Inc. and Network Equipment Technologies, Inc. ("NET") (collectively, together with the Company, the "Loan Parties") pursuant to a Master Continuing Guaranty and are secured by the assets of the Loan Parties pursuant to a Security and Pledge Agreement. The Company did not have any amounts outstanding under the Credit Agreement at June 26, 2015 .

COMMON STOCK REPURCHASES AND UN

COMMON STOCK REPURCHASES AND UNDERWRITTEN OFFERING (Notes)	6 Months Ended
	Jun. 26, 2015
Equity [Abstract]
COMMON STOCK REPURCHASES AND UNDERWRITTEN OFFERING	COMMON STOCK REPURCHASES AND UNDERWRITTEN OFFERING Stock Buyback Program 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 being funded using the Company's working capital. During the six months ended June 26, 2015 , the Company spent $6.1 million , including transaction fees, to repurchase and retire 0.4 million shares of its common stock under the stock buyback program. During the six months ended June 27, 2014 , the Company spent $8.2 million , including transaction fees, to repurchase and retire 0.5 million shares of its common stock under the stock buyback program. At June 26, 2015 , the Company had $16.8 million remaining under the stock buyback program for future repurchases. Underwritten Offering On March 20, 2014, the Company announced the commencement of an underwritten public offering of 7.5 million shares of its common stock on behalf of Galahad Securities Limited and its affiliated entities (collectively, the "Legatum Group"). The underwriter of the offering was granted a 30 -day option to purchase up to 1.125 million additional shares from the Legatum Group. The Legatum Group received all the proceeds from the underwritten offering; no shares in the underwritten offering were sold by Sonus or any of its officers or directors. Sonus purchased 4.3 million shares of its common stock from the underwriter for $17.4410 per share, the price equal to the price paid by the underwriter to the Legatum Group in the underwritten offering, for a total of $75.3 million , including transaction fees of $0.3 million . This repurchase was not completed under the Company's stock buyback program. Sonus funded the share repurchase with cash on hand. The repurchased shares were retired upon completion of the transaction.

STOCK-BASED COMPENSATION PLANS

STOCK-BASED COMPENSATION PLANS	6 Months Ended
	Jun. 26, 2015
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
STOCK-BASED COMPENSATION PLANS	STOCK-BASED COMPENSATION PLANS Stock Incentive Plan The Company's 2007 Stock Incentive Plan, as amended (the "2007 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 June 11, 2015 annual meeting of stockholders, the Company's stockholders approved amendments to the 2007 Plan to, among other things: • Increase the number of shares available for future grant by 1.4 million shares; and • Revise the rate at which restricted stock, restricted stock units, performance awards and other stock unit awards are counted against the shares of common stock available for issuance under the 2007 Plan from 1.57 shares for every one share issued in connection with such award to 1.61 shares for every one share issued in connection with such award. Shares of common stock subject to awards that were granted under the two previous ratios of 1.57 and 1.5 will return to the 2007 Plan upon forfeiture of such awards at the respective previous ratios. Executive and Board of Directors Equity Arrangements In connection with the Company's annual incentive program, 22 executives of the Company were given the choice to receive all or half of their fiscal year 2015 bonuses (the "2015 Bonus"), if any are earned, in the form of shares of the Company's common stock (the "2015 Bonus Shares"). Each executive could also elect not to participate in this program and to earn his or her 2015 Bonus, if any, in the form of cash. The amount of the 2015 Bonus, if any, for each executive shall be determined by the Compensation Committee of the Board of Directors of the Company (the "Compensation Committee"). The number of shares of the Company's common stock that will be granted to those executives who elected to receive their 2015 Bonus entirely in the form of shares of common stock will be calculated by dividing an amount equal to 1.5 times each executive's 2015 Bonus earned by $20.55 , the closing price of the Company's common stock on January 2, 2015. The number of shares of the Company's common stock that will be granted to those executives who elected to receive one-half of their 2015 Bonus in the form of shares of common stock will be calculated by dividing an amount equal to 1.5 times one-half of each executive's 2015 Bonus earned by $20.55 , with the cash portion equal 50% of their respective 2015 Bonus earned. The 2015 Bonus, if any, will be granted and/or paid on a date concurrent with the timing of the payout of bonuses under the Company-wide incentive bonus program and will be fully vested on the date of grant. Of the eligible executives, 16 elected to receive their entire 2015 Bonus in shares of common stock, five elected to receive 50% of their 2015 Bonus in shares of common stock and 50% in cash and one elected not to participate and instead to receive his entire 2015 Bonus in cash. As of June 26, 2015, four participants in the 2015 Bonus separated from the Company and accordingly, forfeited any 2015 Bonus Shares they might otherwise have earned. As of June 26, 2015, the Company determined that the grant date criteria for the 2015 Bonus Shares had not been met; accordingly, the Company is marking to market the 2015 Bonus Shares expected to be earned and recording expense based on the aggregate fair value of the 2015 Bonus Shares at June 26, 2015. If earned, the 2015 Bonus Shares will not be granted until the date of the 2015 Bonus payment; accordingly, there are no shares related to the 2015 Bonus reported in the RSA table below. On January 22, 2014, 21 executives of the Company were given the choice to receive all or half of their fiscal year 2014 bonuses (the "2014 Bonus"), if any were earned, in the form of shares of the Company's common stock (the "2014 Bonus Shares"). Of the eligible executives, 17 elected to receive their entire 2014 Bonus in shares of common stock, while 4 elected to receive 50% of their 2014 Bonus in shares of common stock and 50% in cash. The 2014 Bonus Shares were granted on February 20, 2015 and vested immediately. The Company granted approximately 266,000 2014 Bonus Shares, with the number of shares granted calculated by dividing amounts equal to 1.5 times each executive's 2014 Bonus earned, as determined by the Compensation Committee, by $15.40 , the closing price of the Company's common stock on January 2, 2014. The Company recorded stock-based compensation expense for the 2014 Bonus Shares from January 1, 2014 through the grant date. These shares are reported as both "Granted" and "Vested" in the RSA table below. On March 16, 2015, the Company granted 131,250 PSUs in the aggregate to eight of its executives with both market and service conditions. The terms of the PSUs are such that up to one-third of the shares subject to the PSUs will vest on each of the first, second and third anniversaries of the date of grant (collectively, the "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 Performance Period, measured by the Compensation Committee at the end of each of the 2015, 2016 and 2017 fiscal years, respectively (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 PSUs that fail to be earned will be forfeited. The PSUs include a market condition which requires 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 PSUs. The Company is recording expense for the PSUs through the final Vesting Date of March 16, 2018. The PSUs are reported as "Granted" in the performance-based awards table below. In connection with the separation of two executives from the Company during the second quarter of 2015 and in accordance with their employment agreements with the Company, the Company accelerated the vesting of certain unvested stock options, RSAs and PSUs. These RSAs and PSUs are reported as "Vested" in the respective tables below. Stock Options The activity related to the Company's outstanding stock options during the six months ended June 26, 2015 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, 2015 7,521,432 $ 16.47 Granted 293,670 $ 15.88 Exercised (152,108 ) $ 10.89 Forfeited (409,632 ) $ 16.33 Expired (148,415 ) $ 22.35 Outstanding at June 26, 2015 7,104,947 $ 16.45 6.38 $ 266 Vested or expected to vest at June 26, 2015 6,777,011 $ 16.44 6.28 $ 261 Exercisable at June 26, 2015 4,436,966 $ 16.66 5.20 $ 222 The grant date fair values of options to purchase common stock granted in the six months ended June 26, 2015 were estimated using the Black-Scholes valuation model with the following assumptions: Three months ended Six months ended June 26, June 26, Risk-free interest rate 1.65% 1.46% - 1.74% Expected dividends — — Weighted average volatility 54.3% 54.3% Expected life (years) 5.0 5.0 - 6.0 Additional information regarding the Company's stock options for the six months ended June 26, 2015 is as follows: Three months ended Six months ended June 26, June 26, Weighted average grant date fair value of stock options granted $ 3.72 $ 8.04 Total intrinsic value of stock options exercised (in thousands) $ 16 $ 918 Cash received from the exercise of stock options (in thousands) $ 52 $ 1,739 Restricted Stock Awards and Units The activity related to the Company's RSAs for the six months ended June 26, 2015 is as follows: Shares Weighted Average Grant Date Fair Value Unvested balance at January 1, 2015 370,182 $ 16.74 Granted 1,663,051 $ 15.13 Vested (421,147 ) $ 17.50 Forfeited (153,570 ) $ 16.25 Unvested balance at June 26, 2015 1,458,516 $ 14.74 The activity related to the Company's unvested RSUs for the six months ended June 26, 2015 is as follows: Shares Weighted Average Grant Date Fair Value Unvested balance at January 1, 2015 — $ — Granted 120,215 $ 16.05 Vested — $ — Forfeited (10,672 ) $ 16.05 Unvested balance at June 26, 2015 109,543 $ 16.05 The total fair value of shares of restricted stock that vested during the six months ended June 26, 2015 was $7.4 million . Performance-Based Stock Awards and Units The activity related to the Company's PSAs for the six months ended June 26, 2015 is as follows: Shares Weighted Average Grant Date Fair Value Unvested balance at January 1, 2015 34,235 $ 13.60 Granted — $ — Vested (28,610 ) $ 13.60 Forfeited — $ — Unvested balance at June 26, 2015 5,625 $ 13.60 The activity related to the Company's PSUs for the six months ended June 26, 2015 is as follows: Shares Weighted Average Grant Date Fair Value Unvested balance at January 1, 2015 — $ — Granted 131,250 $ 14.68 Vested (11,666 ) $ 14.18 Forfeited (8,334 ) $ 15.38 Unvested balance at June 26, 2015 111,250 $ 14.68 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. S tock-Based Compensation The condensed consolidated statements of operations include stock-based compensation for the three and six months ended June 26, 2015 and June 27, 2014 as follows (in thousands): Three months ended Six months ended June 26, June 27, June 26, June 27, Product cost of revenue $ 83 $ 104 $ 157 $ 183 Service cost of revenue 397 412 777 691 Research and development 1,445 1,749 2,803 3,062 Sales and marketing 1,852 1,303 2,868 2,552 General and administrative 3,032 3,370 5,024 6,224 $ 6,809 $ 6,938 $ 11,629 $ 12,712 There is no income tax benefit for employee stock-based compensation expense for the six months ended June 26, 2015 or June 27, 2014 due to the valuation allowance recorded. At June 26, 2015 , there was $37.9 million , net of expected forfeitures, of unrecognized stock-based compensation expense related to unvested stock options, awards and units. This expense is expected to be recognized over a weighted average period of approximately two and one-half years .

MAJOR CUSTOMERS

MAJOR CUSTOMERS	6 Months Ended
	Jun. 26, 2015
Risks and Uncertainties [Abstract]
MAJOR CUSTOMERS	MAJOR CUSTOMERS The following customer contributed 10% or more of the Company's revenue in each of the three and six month periods ended June 26, 2015 and June 27, 2014 : Three months ended Six months ended June 26, June 27, June 26, June 27, AT&T Inc. 19% 20% 13% 24% There were no other customers who contributed 10% or more of the Company's revenue in any of the three or six month periods ended June 26, 2015 and June 27, 2014. At June 26, 2015 , two customers each accounted for 10% or more of the Company's accounts receivable balance, representing approximately 34% in the aggregate of the Company's accounts receivable balance. At December 31, 2014 , 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. 26, 2015
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 26, June 27, June 26, June 27, United States 71 % 71 % 67 % 72 % Europe, Middle East and Africa 12 14 13 13 Japan 9 9 13 8 Other Asia Pacific 4 4 4 4 Other 4 2 3 3 100 % 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. 26, 2015
Income Tax Disclosure [Abstract]
INCOME TAXES	INCOME TAXES The Company's income tax provisions for the six months ended June 26, 2015 and June 27, 2014 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 26, 2015 and June 27, 2014 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.

COMMITMENTS AND CONTINGENCIES

COMMITMENTS AND CONTINGENCIES	6 Months Ended
	Jun. 26, 2015
Commitments and Contingencies Disclosure [Abstract]
COMMITMENTS AND CONTINGENCIES	COMMITMENTS AND CONTINGENCIES On April 6, 2015, Ming Huang, a purported shareholder of the Company (the “Plaintiff”), filed a Class Action Complaint alleging violations of the federal securities laws (the “Complaint”) in the United States District Court for the District of New Jersey (Civil Action No. 3:15-02407), against Sonus and two of its officers, Raymond P. Dolan, the Company’s President and Chief Executive Officer, and Mark T. Greenquist, the Company’s Chief Financial Officer (collectively, the “Defendants”). 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 the claim that the Defendants made misleading forward-looking statements concerning the Company’s fiscal first quarter 2015 financial performance. The Company believes that the Defendants have meritorious defenses to the allegations made in the Complaint and does not expect the results of this suit to have a material effect on its business or consolidated financial statements. 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. 26, 2015
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, 2014 (the "Annual Report") filed with the SEC on February 25, 2015. During the preparation of the Company's consolidated financial statements for the three month period ended June 26, 2015, the Company identified an error related to the historical foreign translation of depreciation expense on certain foreign fixed assets that resulted in a historical understatement of expense in prior fiscal years totaling $1.4 million on a cumulative basis. There is no tax effect on these expenses as the amounts were calculated in the appropriate foreign currencies. The Company does not believe this error is material to its previously issued historical consolidated financial statements for any of the periods impacted and accordingly, has not adjusted the historical financial statements. The Company has recorded the cumulative impact of the adjustment in the three months ended June 26, 2015. This adjustment resulted in a one-time $1.4 million overstatement of depreciation expense in both the three and six months ended June 26, 2015. The Company does not believe this adjustment is material to its condensed consolidated financial statements for either the three or six months ended June 26, 2015. The Company effected a one-for-five reverse stock split of its issued, outstanding and authorized common stock, which became effective as of the commencement of trading on the NASDAQ Global Select Market on January 30, 2015. Unless otherwise indicated, all references herein to shares outstanding and share issuances have been adjusted to give effect to the Company's January 2015 reverse stock split. On January 2, 2015 (the "Treq Asset Acquisition Date"), the Company acquired from Treq Labs, Inc. ("Treq") certain assets related to Treq's business of designing, developing, marketing, selling, servicing and maintaining software defined networking ("SDN") technology, SDN controller software and SDN management software (the "SDN Business"). The financial results of the SDN Business are included in the Company's condensed consolidated financial statements starting on the Treq Asset Acquisition Date. On February 19, 2014 (the "PT Acquisition Date"), the Company completed the acquisition of Performance Technologies, Incorporated ("PT"). The financial results of PT are included in the Company's condensed consolidated financial statements starting on the PT Acquisition Date.
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.
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, convertible subordinated debt 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 April 2015, the Financial Accounting Standards Board ("FASB") issued Accounting Standards Update ("ASU") 2015-05, Customer's Accounting for Fees Paid in a Cloud Computing Arrangement ("ASU 2015-05"), which provides guidance on a customer's accounting for cloud computing costs. Under ASU 2015-05, a customer must determine whether a cloud computing arrangement contains a software license. If so, the customer would account for the fees related to the software license element in a manner consistent with how the acquisition of other software licenses is accounted for under Accounting Standards Codification ("ASC") 350-40, Intangibles - Goodwill and Other - Internal Use Software ("ASC 350-40"). If the arrangement does not contain a software license, the customer would account for cloud computing arrangements as service contracts. An arrangement would contain a software license element if both of the following criteria are met: (i) the customer has the contractual right to take possession of the software at any time during the hosting period without significant penalty; and (ii) it is feasible for the customer to either run the software on its own hardware or contract with another party unrelated to the vendor to host the software. ASU 2015-05 is effective for the Company for both annual and interim reporting beginning January 1, 2016. Early adoption is permitted. Entities may adopt the guidance either retrospectively or prospectively to arrangements entered into, or materially modified after the effective date. The Company is currently assessing the potential impact of the adoption of ASU 2015-05 on its consolidated financial statements. In April 2015, the FASB issued ASU 2015-03, Simplifying the Presentation of Debt Issuance Costs ("ASU 2015-03"). Under ASU 2015-03, an entity must present debt issuance costs on the balance sheet as a direct deduction from the related debt liability rather than as an asset. Amortization of the costs is reported as interest expense. ASU 2015-03 is effective for the Company for both annual and interim reporting beginning January 1, 2016. Early adoption is permitted. Entities must apply the new guidance retrospectively to all prior periods (i.e., the balance sheet for each period should be adjusted). The Company is currently assessing the potential impact of the adoption of ASU 2015-03 on its consolidated financial statements. In August 2014, the FASB issued ASU 2014-15, Disclosure of Uncertainties about an Entity's Ability to Continue as a Going Concern ("ASU 2014-15"). ASU 2014-15 provides guidelines determining when and how to disclose going concern uncertainties in the financial statements. The new standard requires management to perform interim and annual assessments of an entity's ability to continue as a going concern within one year of the date the financial statements are issued. An entity must provide certain disclosures if conditions or events raise substantial doubt about the entity's ability to continue as a going concern. ASU 2014-15is effective for the Company for annual periods ending after December 15, 2016, and interim periods thereafter, with early adoption permitted. The adoption of ASU 2014-15 is not expected to have a material impact on the Company's consolidated financial statements. In June 2014, the FASB issued ASU 2014-12, Compensation - Stock Compensation (Topic 718): Accounting for Share-Based Payments When the Terms of an Award Provide That a Performance Target Could Be Achieved after the Requisite Service Period (a consensus of the FASB Emerging Issues Task Force) (“ASU 2014-12”). ASU 2014-12 clarifies that entities should treat performance targets that can be met after the requisite service period of a share-based payment award as performance conditions that affect vesting. Therefore, an entity would not record compensation expense (measured as of the grant date without taking into account the effect of the performance target) related to an award for which transfer to the employee is contingent upon the entity’s satisfaction of a performance target until it becomes probable that the performance target will be met. ASU 2014-12 does not contain any new disclosure requirements. ASU 2014-12 is effective for the Company on January 1, 2016. The adoption of ASU 2014-12 is not expected to 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. ASU 2014-09 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. ASU 2014-09 applies to all contracts with customers that are within the scope of other topics in the FASB ASC. Certain of ASU 2014-09’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. In July 2015, the FASB decided to defer the original effective date of interim and annual reporting periods by one year. As a result, public entities would not be required to apply the new revenue standard until annual reporting periods beginning after December 15, 2017. The Company is currently assessing the potential impact of the adoption of ASU 2014-09 on its consolidated financial statements.

BUSINESS ACQUISITIONS (Tables)

BUSINESS ACQUISITIONS (Tables)	6 Months Ended
	Jun. 26, 2015
Business Combinations [Abstract]
Summary of preliminary allocation of the purchase consideration	A summary of the allocation of the purchase consideration for PT is as follows (in thousands): Fair value of consideration transferred: Cash, net of cash acquired $ 35,022 Fair value of equity awards assumed 1,671 Fair value of total consideration $ 36,693 Fair value of assets acquired and liabilities assumed: Marketable securities $ 2,315 Other current assets 9,337 Property and equipment 2,251 Intangible assets: Developed technology 13,200 Customer relationships 3,900 Goodwill 8,781 Current liabilities (2,762 ) Other long-term liabilities (329 ) $ 36,693 A summary of the purchase consideration for the SDN Business is as follows (in thousands): Fair value of consideration transferred: Cash, net of cash acquired $ 10,147 Unpaid purchase consideration 1,500 Fair value of total consideration $ 11,647 Fair value of assets acquired and liabilities assumed: Intangible assets: In-process research and development $ 9,100 Developed technology 1,500 Goodwill 1,047 $ 11,647
Schedule of Components of Acquisition Related Costs	The components of acquisition-related costs included in the Company's results of operations for the three and six months ended June 26, 2015 and June 27, 2014 are as follows (in thousands): Three months ended Six months ended June 26, June 27, June 26, June 27, Professional and services fees $ 24 $ — $ 131 $ 1,057 Change of control agreements — — — 249 $ 24 $ — $ 131 $ 1,306

EARNINGS (LOSS) PER SHARE (Tabl

EARNINGS (LOSS) PER SHARE (Tables)	6 Months Ended
	Jun. 26, 2015
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 26, June 27, June 26, June 27, Weighted average shares outstanding—basic 49,484 49,424 49,454 51,211 Potential dilutive common shares — — — — Weighted average shares outstanding—diluted 49,484 49,424 49,454 51,211

CASH EQUIVALENTS AND INVESTME25

CASH EQUIVALENTS AND INVESTMENTS (Tables)	6 Months Ended
	Jun. 26, 2015
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 26, 2015 and December 31, 2014 were comprised of the following (in thousands): June 26, 2015 Amortized cost Unrealized gains Unrealized losses Fair value Cash equivalents $ 10,345 $ — $ — $ 10,345 Marketable securities Municipal obligations $ 2,279 $ 1 $ — $ 2,280 U.S. government agency notes 2,150 1 — 2,151 Corporate debt securities 52,121 2 (48 ) 52,075 Commercial paper 5,086 — — 5,086 Certificates of deposit 2,950 — — 2,950 $ 64,586 $ 4 $ (48 ) $ 64,542 Investments Municipal obligations $ 1,435 $ 1 $ (2 ) $ 1,434 U.S. government agency notes 2,301 2 — 2,303 Corporate debt securities 11,133 — (19 ) 11,114 $ 14,869 $ 3 $ (21 ) $ 14,851 December 31, 2014 Amortized cost Unrealized gains Unrealized losses Fair value Cash equivalents $ 11,653 $ — $ — $ 11,653 Marketable securities Municipal obligations $ 1,273 $ 1 $ (1 ) $ 1,273 U.S. government agency notes 4,016 — — 4,016 Corporate debt securities 40,921 2 (59 ) 40,864 Commercial paper 9,340 — — 9,340 Certificates of deposit 8,950 — — 8,950 $ 64,500 $ 3 $ (60 ) $ 64,443 Investments Municipal obligations $ 2,702 $ 1 $ (3 ) $ 2,700 U.S. government agency notes 2,300 — (1 ) 2,299 Corporate debt securities 35,897 4 (86 ) 35,815 Commercial paper 1,093 — — 1,093 Certificates of deposit 500 — — 500 $ 42,492 $ 5 $ (90 ) $ 42,407
Schedule of fair value of financial assets	The following table shows the fair value of the Company's financial assets at June 26, 2015 and December 31, 2014 . These financial assets are comprised of the Company's available-for-sale debt securities and reported under the captions Cash and cash equivalents, Short-term investments 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 $ 10,345 $ 10,345 $ — $ — Marketable securities Municipal obligations $ 2,280 $ — $ 2,280 $ — U.S. government agency notes 2,151 — 2,151 — Corporate debt securities 52,075 — 52,075 — Commercial paper 5,086 — 5,086 — Certificates of deposit 2,950 — 2,950 — $ 64,542 $ — $ 64,542 $ — Investments Municipal obligations $ 1,434 $ — $ 1,434 $ — U.S. government agency notes 2,303 — 2,303 — Corporate debt securities 11,114 — 11,114 — $ 14,851 $ — $ 14,851 $ — 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 $ 11,653 $ 11,653 $ — $ — Marketable securities Municipal obligations $ 1,273 $ — $ 1,273 $ — U.S. government agency notes 4,016 — 4,016 — Corporate debt securities 40,864 — 40,864 — Commercial paper 9,340 — 9,340 — Certificates of deposit 8,950 — 8,950 — $ 64,443 $ — $ 64,443 $ — Investments Municipal obligations $ 2,700 $ — $ 2,700 $ — U.S. government agency notes 2,299 — 2,299 — Corporate debt securities 35,815 — 35,815 — Commercial paper 1,093 — 1,093 — Certificates of deposit 500 — 500 — $ 42,407 $ — $ 42,407 $ —

INVENTORY (Tables)

INVENTORY (Tables)	6 Months Ended
	Jun. 26, 2015
Inventory Disclosure [Abstract]
Schedule of inventory	Inventory consists of the following (in thousands): June 26, December 31, On-hand final assemblies and finished goods inventories $ 22,658 $ 19,285 Deferred cost of goods sold 3,041 2,829 $ 25,699 $ 22,114

INTANGIBLE ASSETS AND GOODWILL

INTANGIBLE ASSETS AND GOODWILL (Tables)	6 Months Ended
	Jun. 26, 2015
Goodwill and Intangible Assets Disclosure [Abstract]
Schedule of intangible assets	The Company's intangible assets at June 26, 2015 and December 31, 2014 consist of the following (dollars in thousands): June 26, 2015 Weighted average amortization period (years) Cost Accumulated amortization Net carrying value In-process research and development 7.00 $ 9,100 $ — $ 9,100 Intellectual property 5.00 999 999 — Developed technology 6.24 23,780 7,416 16,364 Customer relationships 5.57 10,040 5,589 4,451 Internal use software 3.00 730 689 41 6.05 $ 44,649 $ 14,693 $ 29,956 December 31, 2014 Weighted average amortization period (years) Cost Accumulated amortization Net carrying value Intellectual property 5.00 $ 999 $ 999 $ — Developed technology 6.18 22,280 5,193 17,087 Customer relationships 5.57 10,040 4,695 5,345 Internal use software 3.00 730 568 162 5.75 $ 34,049 $ 11,455 $ 22,594
Schedule of amortization expense related to intangible assets	Amortization expense for intangible assets for the three and six months ended June 26, 2015 and June 27, 2014 was as follows (in thousands): Three months ended Six months ended Statement of operations classification June 26, June 27, June 26, June 27, Developed technology $ 1,116 $ 613 $ 2,223 $ 1,183 Cost of revenue - product Customer relationships 415 505 894 903 Sales and marketing Internal use software 60 60 121 121 Cost of revenue - product $ 1,591 $ 1,178 $ 3,238 $ 2,207
Schedule of estimated future amortization expense for intangible assets	Estimated future amortization expense for the Company's intangible assets at June 26, 2015 is as follows (in thousands): Years ending December 31, Remainder of 2015 $ 3,869 2016 7,189 2017 7,281 2018 4,644 2019 3,611 Thereafter 3,362 $ 29,956
Schedule of goodwill	The changes in the carrying value of the Company's goodwill in the six months ended June 26, 2015 and June 27, 2014 were as follows (in thousands): Balance at January 1, 2015 Goodwill $ 42,369 Accumulated impairment losses (3,106 ) 39,263 Acquisition of SDN Business 1,047 Balance at June 26, 2015 $ 40,310 Balance at June 26, 2015 Goodwill $ 43,416 Accumulated impairment losses (3,106 ) $ 40,310 Balance at January 1, 2014 Goodwill $ 35,485 Accumulated impairment losses (3,106 ) 32,379 Acquisition of PT 8,725 Sale of MPS business (1,897 ) Balance at June 27, 2014 $ 39,207 Balance at June 27, 2014 Goodwill $ 42,313 Accumulated impairment losses (3,106 ) $ 39,207

ACCRUED EXPENSES (Tables)

ACCRUED EXPENSES (Tables)	6 Months Ended
	Jun. 26, 2015
Payables and Accruals [Abstract]
Schedule of accrued expenses	Accrued expenses consist of the following (in thousands): June 26, December 31, Employee compensation and related costs $ 9,647 $ 20,042 Other 12,866 12,107 $ 22,513 $ 32,149

RESTRUCTURING ACCRUAL (Tables)

RESTRUCTURING ACCRUAL (Tables)	6 Months Ended
	Jun. 26, 2015
Restructuring and Related Activities [Abstract]
Summary of restructuring accrual activity	2015 Restructuring Initiative Balance at Initiatives Cash Balance at Severance $ — $ 2,899 $ (2,452 ) $ 447 The Company expects that the remaining amounts accrued under the 2015 Restructuring Initiative will be paid in the three months ending September 25, 2015. 2012 Restructuring Initiative On August 7, 2012, the Company announced that it had committed to a restructuring initiative to streamline operations and reduce operating costs by closing and consolidating certain facilities and reducing its worldwide workforce (the "2012 Restructuring Initiative"). The Company regularly reviews its restructuring accruals against expected cash expenditures to determine if adjustments are required. As a result of such reviews, the Company recorded credits to restructuring expense aggregating $1.8 million in the six months ended June 26, 2015. This amount is comprised of a credit of $1.4 million recorded in the three months ended June 26, 2015 in connection with a settlement with the landlord of the Company's Fremont, California facility to vacate the facility without penalty or future payments and a credit of $0.3 million recorded in the three months ended March 27, 2015. The amount reversed in the three months ended March 27, 2015 is comprised of approximately $272,000 for facilities in connection with a settlement with the landlord of the Company's Dulles, Virginia facility for an amount that was lower than had previously been accrued and approximately $67,000 in connection with changes in the amounts of severance ultimately paid to certain individuals. The Company recorded $1.2 million of restructuring expense in the three months ended June 27, 2014 and $1.6 million in the six months ended June 27, 2014 for severance and related costs in connection with reducing its workforce. A summary of the 2012 Restructuring Initiative accrual activity for the six months ended June 26, 2015 is as follows (in thousands): 2012 Restructuring Initiative Balance at Initiatives Adjustments for changes in estimate Cash Balance at Severance $ 1,682 $ — $ (67 ) $ (1,479 ) $ 136 Facilities 3,652 — (1,684 ) (1,514 ) 454 $ 5,334 $ — $ (1,751 ) $ (2,993 ) $ 590

STOCK-BASED COMPENSATION PLANS

STOCK-BASED COMPENSATION PLANS (Tables)	6 Months Ended
	Jun. 26, 2015
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 during the six months ended June 26, 2015 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, 2015 7,521,432 $ 16.47 Granted 293,670 $ 15.88 Exercised (152,108 ) $ 10.89 Forfeited (409,632 ) $ 16.33 Expired (148,415 ) $ 22.35 Outstanding at June 26, 2015 7,104,947 $ 16.45 6.38 $ 266 Vested or expected to vest at June 26, 2015 6,777,011 $ 16.44 6.28 $ 261 Exercisable at June 26, 2015 4,436,966 $ 16.66 5.20 $ 222
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 six months ended June 26, 2015 were estimated using the Black-Scholes valuation model with the following assumptions: Three months ended Six months ended June 26, June 26, Risk-free interest rate 1.65% 1.46% - 1.74% Expected dividends — — Weighted average volatility 54.3% 54.3% Expected life (years) 5.0 5.0 - 6.0
Schedule of stock options, additional information	Additional information regarding the Company's stock options for the six months ended June 26, 2015 is as follows: Three months ended Six months ended June 26, June 26, Weighted average grant date fair value of stock options granted $ 3.72 $ 8.04 Total intrinsic value of stock options exercised (in thousands) $ 16 $ 918 Cash received from the exercise of stock options (in thousands) $ 52 $ 1,739
Schedule of activity related to unvested restricted stock grants	The activity related to the Company's RSAs for the six months ended June 26, 2015 is as follows: Shares Weighted Average Grant Date Fair Value Unvested balance at January 1, 2015 370,182 $ 16.74 Granted 1,663,051 $ 15.13 Vested (421,147 ) $ 17.50 Forfeited (153,570 ) $ 16.25 Unvested balance at June 26, 2015 1,458,516 $ 14.74
Schedule of activity related to performance stock awards	The activity related to the Company's PSAs for the six months ended June 26, 2015 is as follows: Shares Weighted Average Grant Date Fair Value Unvested balance at January 1, 2015 34,235 $ 13.60 Granted — $ — Vested (28,610 ) $ 13.60 Forfeited — $ — Unvested balance at June 26, 2015 5,625 $ 13.60
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 26, 2015 and June 27, 2014 as follows (in thousands): Three months ended Six months ended June 26, June 27, June 26, June 27, Product cost of revenue $ 83 $ 104 $ 157 $ 183 Service cost of revenue 397 412 777 691 Research and development 1,445 1,749 2,803 3,062 Sales and marketing 1,852 1,303 2,868 2,552 General and administrative 3,032 3,370 5,024 6,224 $ 6,809 $ 6,938 $ 11,629 $ 12,712

MAJOR CUSTOMERS (Tables)

MAJOR CUSTOMERS (Tables)	6 Months Ended
	Jun. 26, 2015
Risks and Uncertainties [Abstract]
Schedule of customers contributing 10% or more of the revenue	The following customer contributed 10% or more of the Company's revenue in each of the three and six month periods ended June 26, 2015 and June 27, 2014 : Three months ended Six months ended June 26, June 27, June 26, June 27, AT&T Inc. 19% 20% 13% 24%

GEOGRAPHIC INFORMATION (Tables)

GEOGRAPHIC INFORMATION (Tables)	6 Months Ended
	Jun. 26, 2015
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 26, June 27, June 26, June 27, United States 71 % 71 % 67 % 72 % Europe, Middle East and Africa 12 14 13 13 Japan 9 9 13 8 Other Asia Pacific 4 4 4 4 Other 4 2 3 3 100 % 100 % 100 % 100 %

BASIS OF PRESENTATION - Narrati

BASIS OF PRESENTATION - Narrative (Details)	Jan. 30, 2015	Jun. 26, 2015USD ($)	Jun. 26, 2015USD ($)segment
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Stock split, conversion ratio	0.2
Number of reportable operating segments | segment			1
Foreign Translation of Depreciation Expense
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Cumulative understatement of expense		$ 1,400,000
Tax effect of understatement		0
Depreciation		$ 1,400,000	$ 1,400,000

BUSINESS ACQUISITIONS - (Detail

BUSINESS ACQUISITIONS - (Details) - USD ($) $ / shares in Units, shares in Millions	Jan. 02, 2015	Feb. 19, 2014	Jun. 26, 2015	Jun. 27, 2014	Jun. 26, 2015	Jun. 27, 2014	Jan. 04, 2016	Jul. 02, 2015	Dec. 31, 2014	Dec. 31, 2013
Fair value of consideration transferred:
Cash, net of cash acquired					$ 10,147,000	$ 34,010,000
Allocation of the purchase consideration:
Goodwill			$ 40,310,000	$ 39,207,000	40,310,000	39,207,000			$ 39,263,000	$ 32,379,000
Acquisition-related			24,000	0	131,000	1,306,000
Treq Labs, Inc [Member]
Acquisition Of Net
Shares authorized in earn-out agreement	3.5
Business combination, contingent liability			0		0
Fair value of consideration transferred:
Cash, net of cash acquired	$ 10,147,000
Business Combination, Consideration Transferred, Liabilities Incurred	1,500,000
Fair value of total consideration	11,647,000
Allocation of the purchase consideration:
Business Combination, Recognized Identifiable Assets Acquired, Goodwill, and Liabilities Assumed, Net	11,647,000
PT [Member]
Acquisition Of Net
Cash consideration		$ 35,000,000
Cash consideration per share of the acquired entity (in dollars per share)		$ 3.75
Fair value of consideration transferred:
Cash, net of cash acquired		$ 35,022,000
Assumption of equity awards in connection with acquisition of Network Technologies, Inc.		1,671,000
Fair value of total consideration		36,693,000
Allocation of the purchase consideration:
Marketable securities		2,315,000
Other current assets		9,337,000
Property and equipment		2,251,000
Goodwill		8,781,000
Current liabilities		(2,762,000)
Other long-term liabilities		(329,000)
Business Combination, Recognized Identifiable Assets Acquired, Goodwill, and Liabilities Assumed, Net		36,693,000
Professional Fees			24,000	0	131,000	1,057,000
Change of Control Agreements			0	0	0	249,000
Acquisition-related			$ 24,000	$ 0	$ 131,000	$ 1,306,000
In Process Research and Development [Member] | Treq Labs, Inc [Member]
Allocation of the purchase consideration:
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Intangible Assets, Other than Goodwill	9,100,000
Developed Technology Rights [Member] | Treq Labs, Inc [Member]
Allocation of the purchase consideration:
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Intangible Assets, Other than Goodwill	1,500,000
Goodwill	$ 1,047,000
Developed Technology Rights [Member] | PT [Member]
Allocation of the purchase consideration:
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Intangible Assets, Other than Goodwill		13,200,000
Customer relationships [Member] | PT [Member]
Allocation of the purchase consideration:
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Intangible Assets, Other than Goodwill		$ 3,900,000
Scenario, Forecast [Member] | Treq Labs, Inc [Member]
Acquisition Of Net
Future consideration payment							$ 750,000	$ 750,000
Earn-Out Agreement Revenue Level 1 [Member]
Acquisition Of Net
Duration of earn-out agreement	3 years
Earn-Out Agreement Revenue Level 1 [Member] | Treq Labs, Inc [Member]
Acquisition Of Net
Shares authorized in earn-out agreement	1.3
Earn-out agreement aggregate revenue threshold	$ 60,000,000
Earn-Out Agreement Revenue Level 2 [Member] | Treq Labs, Inc [Member]
Acquisition Of Net
Shares authorized in earn-out agreement	2.2
Earn-out agreement aggregate revenue threshold	$ 150,000,000

BUSINESS ACQUISITIONS - Sale of

BUSINESS ACQUISITIONS - Sale of MPS (Details) - USD ($) $ in Thousands	Jun. 20, 2014	Jun. 26, 2015	Jun. 27, 2014
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Divestiture of business		$ 0	$ 2,000
Multi Protocol Server [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Divestiture of business		$ 2,000
Inventory	$ (200)
Fixed assets	(100)
Deferred revenue	200
Goodwill	$ (1,900)

EARNINGS (LOSS) PER SHARE - (De

EARNINGS (LOSS) PER SHARE - (Details) - shares shares in Thousands	3 Months Ended		6 Months Ended
	Jun. 26, 2015	Jun. 27, 2014	Jun. 26, 2015	Jun. 27, 2014
Reconciliation of weighted average shares outstanding from basic to diluted
Weighted average shares outstanding - basic	49,484	49,424	49,454	51,211
Potential dilutive common shares	0	0	0	0
Weighted average shares outstanding - diluted	49,484	49,424	49,454	51,211
Common stock and unvested shares of restricted stock not included because their effect would have been antidilutive (in shares)	8,900	8,800	8,900	8,800

CASH EQUIVALENTS AND INVESTME37

CASH EQUIVALENTS AND INVESTMENTS - Narrative (Details) - Jun. 26, 2015 - USD ($) $ in Thousands	Total	Total
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities sold	$ 45,900
Available-for-sale securities, gross realized gains	46
Proceeds from maturities of available-for-sale securities	$ 41,700
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. 26, 2015	Dec. 31, 2014
Amortized cost, gross unrealized gains and losses and fair value of marketable debt and equity securities and investments
Cash equivalents, amortized cost	$ 10,345	$ 11,653
Cash equivalents, fair value	10,345	11,653
Marketable securities, amortized cost	64,586	64,500
Marketable securities, unrealized gains	4	3
Marketable securities, unrealized losses	(48)	(60)
Marketable securities, fair value	64,542	64,443
Investments, amortized cost	14,869	42,492
Investments, unrealized gains	3	5
Investments, unrealized losses	(21)	(90)
Investments, fair value	14,851	42,407
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	2,279	1,273
Marketable securities, unrealized gains	1	1
Marketable securities, unrealized losses	0	(1)
Marketable securities, fair value	2,280	1,273
Investments, amortized cost	1,435	2,702
Investments, unrealized gains	1	1
Investments, unrealized losses	(2)	(3)
Investments, fair value	1,434	2,700
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	2,150	4,016
Marketable securities, unrealized gains	1	0
Marketable securities, unrealized losses	0	0
Marketable securities, fair value	2,151	4,016
Investments, amortized cost	2,301	2,300
Investments, unrealized gains	2	0
Investments, unrealized losses	0	(1)
Investments, fair value	2,303	2,299
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	52,121	40,921
Marketable securities, unrealized gains	2	2
Marketable securities, unrealized losses	(48)	(59)
Marketable securities, fair value	52,075	40,864
Investments, amortized cost	11,133	35,897
Investments, unrealized gains	0	4
Investments, unrealized losses	(19)	(86)
Investments, fair value	11,114	35,815
Commercial paper [Member]
Amortized cost, gross unrealized gains and losses and fair value of marketable debt and equity securities and investments
Marketable securities, amortized cost	5,086	9,340
Marketable securities, unrealized gains	0	0
Marketable securities, unrealized losses	0	0
Marketable securities, fair value	5,086	9,340
Investments, amortized cost		1,093
Investments, unrealized gains		0
Investments, unrealized losses		0
Investments, fair value		1,093
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	2,950	8,950
Marketable securities, unrealized gains	0	0
Marketable securities, unrealized losses	0	0
Marketable securities, fair value	$ 2,950	8,950
Investments, amortized cost		500
Investments, unrealized gains		0
Investments, unrealized losses		0
Investments, fair value		$ 500

CASH EQUIVALENTS AND INVESTME39

CASH EQUIVALENTS AND INVESTMENTS - Schedule of Short-Term Investments by Measurement (Detail) - USD ($) $ in Thousands	Jun. 26, 2015	Dec. 31, 2014
Cash and cash equivalents, Marketable securities and Investments
Cash equivalents, fair value	$ 10,345	$ 11,653
Marketable securities, fair value	64,542	64,443
Investments, fair value	14,851	42,407
Total carrying value [Member]
Cash and cash equivalents, Marketable securities and Investments
Cash equivalents, fair value	10,345	11,653
Marketable securities, fair value	64,542	64,443
Investments, fair value	14,851	42,407
Quoted prices in active markets (Level 1) [Member]
Cash and cash equivalents, Marketable securities and Investments
Cash equivalents, fair value	10,345	11,653
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	64,542	64,443
Investments, fair value	14,851	42,407
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	2,280	1,273
Investments, fair value	1,434	2,700
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
Investments, 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	2,280	1,273
Investments, fair value	1,434	2,700
Municipal obligations [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
U.S. government agency notes [Member] | Total carrying value [Member]
Cash and cash equivalents, Marketable securities and Investments
Marketable securities, fair value	2,151	4,016
Investments, fair value	2,303	2,299
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	2,151	4,016
Investments, fair value	2,303	2,299
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	52,075	40,864
Investments, fair value	11,114	35,815
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	52,075	40,864
Investments, fair value	11,114	35,815
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
Commercial paper [Member] | Total carrying value [Member]
Cash and cash equivalents, Marketable securities and Investments
Marketable securities, fair value	5,086	9,340
Investments, fair value		1,093
Commercial paper [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
Commercial paper [Member] | Significant other observable inputs (Level 2) [Member]
Cash and cash equivalents, Marketable securities and Investments
Marketable securities, fair value	5,086	9,340
Investments, fair value		1,093
Commercial paper [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
Certificates of deposit [Member] | Total carrying value [Member]
Cash and cash equivalents, Marketable securities and Investments
Marketable securities, fair value	2,950	8,950
Investments, fair value		500
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
Certificates of deposit [Member] | Significant other observable inputs (Level 2) [Member]
Cash and cash equivalents, Marketable securities and Investments
Marketable securities, fair value	2,950	8,950
Investments, fair value		500
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

INVENTORY - (Details)

INVENTORY - (Details) - USD ($) $ in Thousands	Jun. 26, 2015	Dec. 31, 2014
Inventory Disclosure [Abstract]
On-hand final assemblies and finished goods inventories	$ 22,658	$ 19,285
Deferred cost of goods sold	3,041	2,829
Gross inventory	25,699	22,114
Less current portion	$ (25,699)	$ (22,114)

INTANGIBLE ASSETS AND GOODWIL41

INTANGIBLE ASSETS AND GOODWILL - (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 26, 2015	Jun. 27, 2014	Jun. 26, 2015	Jun. 27, 2014	Dec. 31, 2014	Dec. 31, 2013
Intangible Assets And Goodwill
Goodwill, Gross	$ 43,416	$ 42,313	$ 43,416	$ 42,313	$ 42,369	$ 35,485
Goodwill, Impaired, Accumulated Impairment Loss	3,106	3,106	$ 3,106	3,106	$ 3,106	$ 3,106
Weighted average amortization period (years)			6 years 18 days		5 years 9 months
Cost	44,649		$ 44,649		$ 34,049
Accumulated amortization	14,693		14,693		11,455
Net carrying value	29,956		29,956		$ 22,594
Amortization expense	1,591	1,178	3,238	2,207
Estimated future amortization expense for intangible assets
Remainder of 2014	3,869		3,869
2,015	7,189		7,189
2,016	7,281		7,281
2,017	4,644		4,644
2,018	3,611		3,611
Thereafter	3,362		3,362
Total	29,956		$ 29,956
In Process Research and Development [Member]
Intangible Assets And Goodwill
Weighted average amortization period (years)			7 years
Cost	9,100		$ 9,100
Accumulated amortization	0		0
Net carrying value	9,100		$ 9,100
Intellectual Property [Member]
Intangible Assets And Goodwill
Weighted average amortization period (years)			5 years		5 years
Cost	999		$ 999		$ 999
Accumulated amortization	999		999		999
Net carrying value	0		$ 0		$ 0
Developed technology [Member]
Intangible Assets And Goodwill
Weighted average amortization period (years)			6 years 2 months 28 days		6 years 2 months 6 days
Cost	23,780		$ 23,780		$ 22,280
Accumulated amortization	7,416		7,416		5,193
Net carrying value	16,364		16,364		$ 17,087
Amortization expense	1,116	613	$ 2,223	1,183
Customer relationships [Member]
Intangible Assets And Goodwill
Weighted average amortization period (years)			5 years 6 months 26 days		5 years 6 months 24 days
Cost	10,040		$ 10,040		$ 10,040
Accumulated amortization	5,589		5,589		4,695
Net carrying value	4,451		4,451		$ 5,345
Amortization expense	415	505	$ 894	903
Internal use software [Member]
Intangible Assets And Goodwill
Weighted average amortization period (years)			3 years		3 years
Cost	730		$ 730		$ 730
Accumulated amortization	689		689		568
Net carrying value	41		41		$ 162
Amortization expense	$ 60	$ 60	$ 121	$ 121

INTANGIBLE ASSETS AND GOODWIL42

INTANGIBLE ASSETS AND GOODWILL - (Details 2) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
	Jun. 27, 2014	Jun. 26, 2015	Dec. 31, 2014	Dec. 31, 2013
Goodwill [Roll Forward]
Goodwill	$ 42,313	$ 43,416	$ 42,369	$ 35,485
Accumulated impairment losses	(3,106)	(3,106)	(3,106)	(3,106)
Goodwill, beginning of period	39,207	40,310	$ 39,263	$ 32,379
Acquisition of SDN Business	8,725	1,047
Sale of MPS business	(1,897)
Goodwill, end of period	$ 39,207	$ 40,310

ACCRUED EXPENSES - (Details)

ACCRUED EXPENSES - (Details) - USD ($) $ in Thousands	Jun. 26, 2015	Dec. 31, 2014
Payables and Accruals [Abstract]
Employee compensation and related costs	$ 9,647	$ 20,042
Other	12,866	12,107
Total	$ 22,513	$ 32,149

RESTRUCTURING ACCRUAL - (Detail

RESTRUCTURING ACCRUAL - (Details) $ in Thousands	Apr. 16, 2015position	Jun. 26, 2015USD ($)	Mar. 27, 2015USD ($)	Jun. 27, 2014USD ($)	Jun. 26, 2015USD ($)	Jun. 27, 2014USD ($)	Dec. 31, 2014USD ($)
RESTRUCTURING ACCRUAL
Accrued restructuring		$ 200			$ 200		$ 1,900
Restructuring Reserve [Roll Forward]
Initiatives charged to expense		1,487		$ 391	1,148	$ 1,560
2015 Restructuring [Member]
RESTRUCTURING ACCRUAL
Expected number of positions eliminated | position	150
Expected percentage of positions eliminated	12.50%
Restructuring Reserve [Roll Forward]
Balance at the beginning of the period			$ 0		0
Initiatives charged to expense					2,899
Cash payments					2,452
Balance at the end of the period		447			447
2015 Restructuring [Member] | Employee Severance [Member]
RESTRUCTURING ACCRUAL
Restructuring Costs		2,900
2012 Restructuring Plan [Member]
Restructuring accrual activity
Proceeds from settlement with landlord		1,400	272
Reversal of severance costs		(300)	(67)
Restructuring Reserve [Roll Forward]
Balance at the beginning of the period			5,334		5,334
Initiatives charged to expense				$ 1,200	0	$ 1,600
Adjustments for changes in estimate					(1,751)
Cash payments					2,993
Balance at the end of the period		590			590
2012 Restructuring Plan [Member] | Employee Severance [Member]
Restructuring Reserve [Roll Forward]
Balance at the beginning of the period			1,682		1,682
Initiatives charged to expense					0
Adjustments for changes in estimate					(67)
Cash payments					1,479
Balance at the end of the period		136			136
2012 Restructuring Plan [Member] | Facilities [Member]
Restructuring Reserve [Roll Forward]
Balance at the beginning of the period			$ 3,652		3,652
Initiatives charged to expense					0
Adjustments for changes in estimate					(1,684)
Cash payments					1,514
Balance at the end of the period		$ 454			$ 454

DEBT - (Details)

DEBT - (Details) - Jun. 27, 2014 - Revolving Credit Facility [Member] - USD ($)	Total
Line of Credit Facility [Line Items]
Maximum borrowing capacity	$ 15,000,000
Unused commitment fee percentage	0.15%
London Interbank Offered Rate (LIBOR) [Member]
Line of Credit Facility [Line Items]
Interest rate	1.50%
Federal Funds Purchased [Member]
Line of Credit Facility [Line Items]
Interest rate	0.50%
Eurodollar [Member]
Line of Credit Facility [Line Items]
Interest rate	1.00%

COMMON STOCK REPURCHASES AND 46

COMMON STOCK REPURCHASES AND UNDERWRITTEN OFFERING (Details) - USD ($) $ / shares in Units, shares in Millions	Mar. 20, 2014	Jun. 26, 2015	Jun. 27, 2014	Jan. 02, 2014	Jul. 29, 2013
Class of Stock [Line Items]
Payments for repurchase of common stock	$ 75,300,000	$ 6,084,000	$ 83,518,000
Stock repurchased and retired during period	4.3	0.4	0.5
Share Price	$ 17.4410	$ 20.55		$ 15.40
Remaining authorized repurchase amount	$ 1,125,000	$ 16,800,000
Stock issued during period	7.5
Over-allotment Option Period	30 days
Transaction Fees	$ 300,000
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		$ 6,100,000	$ 8,200,000

STOCK-BASED COMPENSATION PLAN47

STOCK-BASED COMPENSATION PLANS - (Details) $ / shares in Units, $ in Thousands	Mar. 16, 2015executivesshares	Feb. 19, 2014USD ($)$ / shares	Jan. 22, 2014executivesshares	Mar. 28, 2014	Jun. 26, 2015USD ($)$ / sharesshares	Jun. 27, 2014USD ($)	Jun. 26, 2015USD ($)executives$ / sharesshares	Jun. 27, 2014USD ($)	Jun. 11, 2015shares	Jun. 10, 2015	Mar. 27, 2015	Mar. 20, 2014$ / shares	Jan. 02, 2014$ / shares
Stock-based compensation
Additional shares authorized to be repurchased | shares									1,400,000
Number of executives | executives			21				22
Number of Executives Electing to Receive Cash Bonus | executives			4
Share-based Compensation by Share-based Payment Award, Stock Percentage of Award			50.00%				50.00%
Share-based Compensation by Share-based Payment Award, Cash Percentage of Award			50.00%				50.00%
Share-based Compensation Arrangement by Share-based Payment Award, Percentage of Salary Base to Calculate Shares Granted			150.00%				150.00%
Share Price					$ 20.55		$ 20.55					$ 17.4410	$ 15.40
Number of Executives Electing to Receive Stock Bonus | executives			17
Stock-based compensation (in dollars) | $					$ 6,809	$ 6,938	$ 11,629	$ 12,712
Fair value of the assumed awards attributable to future stock-based compensation expense | $					$ 37,900		$ 37,900
Expected period for unrecognized expense							2 years 6 months
Stock-based compensation | $							$ 11,629	12,712
Number of shares
Granted (in shares) | shares			266,000
Range of assumptions used in estimating fair value of options
Expected life					5 years
Cash received from the exercise of stock options (in dollars) | $							1,739	4,541
Product cost of revenue [Member]
Stock-based compensation
Stock-based compensation (in dollars) | $					$ 83	104	157	183
Service cost of revenue [Member]
Stock-based compensation
Stock-based compensation (in dollars) | $					397	412	777	691
Research and development [Member]
Stock-based compensation
Stock-based compensation (in dollars) | $					1,445	1,749	2,803	3,062
Sales and marketing [Member]
Stock-based compensation
Stock-based compensation (in dollars) | $					1,852	1,303	2,868	2,552
General and Administrative Expense [Member]
Stock-based compensation
Stock-based compensation (in dollars) | $					$ 3,032	$ 3,370	$ 5,024	$ 6,224
Minimum [Member]
Range of assumptions used in estimating fair value of options
Expected life							5 years
Maximum [Member]
Range of assumptions used in estimating fair value of options
Expected life							6 years
PT [Member]
Stock-based compensation
Business Combination, Consideration Transferred, Equity Interests Issued and Issuable | $		$ 1,671
Business Acquisition, Share Price		$ 3.75
Stock options [Member]
Stock-based compensation
Number of executives | executives							16
Number of shares
Outstanding at the beginning of the period (in shares) | shares							7,521,432
Granted (in shares) | shares							293,670
Exercised (in shares) | shares							(152,108)
Forfeited (in shares) | shares							(409,632)
Expired (in shares) | shares							(148,415)
Outstanding at the end of the period (in shares) | shares					7,104,947		7,104,947
Vested or expected to vest at the end of the period (in shares) | shares					6,777,011		6,777,011
Exercisable at the end of the period (in shares) | shares					4,436,966		4,436,966
Weighted average exercise price
Outstanding at the beginning of the period (in dollars per share)							$ 16.47
Granted (in dollars per share)							15.88
Exercised (in dollars per share)							10.89
Forfeited (in dollars per share)							16.33
Expired (in dollars per share)							22.35
Outstanding at the end of the period (in dollars per share)					$ 16.45		16.45
Vested or expected to vest at the end of the period (in dollars per share)					16.44		16.44
Exercisable at the end of the period (in dollars per share)					$ 16.66		$ 16.66
Weighted average remaining contractual life (in years)
Outstanding at the end of the period							6 years 4 months 16 days
Vested or expected to vest at the end of the period							6 years 3 months 11 days
Exercisable at the end of the period							5 years 2 months 12 days
Aggregate intrinsic value (in dollars)
Outstanding at the end of the period (in dollars) | $					$ 266		$ 266
Vested or expected to vest at the end of the period (in dollars) | $					261		261
Exercisable at the end of the period (in dollars) | $					$ 222		$ 222
Range of assumptions used in estimating fair value of options
Risk-free interest rates, minimum							1.46%
Risk-free interest rates, maximum							1.74%
Expected dividends					0.00%		0.00%
Weighted average volatility					54.30%		54.30%
Weighted average grant date fair value of stock options granted (in dollars per share)					$ 3.72		$ 8.04
Total intrinsic values of stock options exercised (in dollars) | $					$ 16		$ 918
Cash received from the exercise of stock options (in dollars) | $					$ 52		$ 1,739
Stock Option and Cash Option [Member]
Stock-based compensation
Number of executives | executives							5
Cash Only [Member]
Stock-based compensation
Number of executives | executives							1
Restricted stock awards [Member]
Stock-based compensation
Total fair value (in dollars) | $							$ 7,400
Change in unvested restricted stock awards
Unvested balance at the beginning of the period (in shares) | shares							370,182
Granted (in shares) | shares							1,663,051
Vested (in shares) | shares							(421,147)
Forfeited (in shares) | shares							(153,570)
Unvested balance at the end of the period (in shares) | shares					1,458,516		1,458,516
Weighted average grant-date fair value
Unvested balance at the end of the period (in dollars per share)							$ 16.74
Granted (in dollars per share)							15.13
Vested (in dollars per share)							17.50
Forfeited (in dollars per share)							16.25
Unvested balance at end of the period (in dollars per share)					$ 14.74		$ 14.74
Restricted Stock Units (RSUs) [Member]
Change in unvested restricted stock awards
Unvested balance at the beginning of the period (in shares) | shares							0
Granted (in shares) | shares							120,215
Vested (in shares) | shares							0
Forfeited (in shares) | shares							(10,672)
Unvested balance at the end of the period (in shares) | shares					109,543		109,543
Weighted average grant-date fair value
Unvested balance at the end of the period (in dollars per share)							$ 0
Granted (in dollars per share)							16.05
Vested (in dollars per share)							0
Forfeited (in dollars per share)							16.05
Unvested balance at end of the period (in dollars per share)					$ 16.05		$ 16.05
Performance share awards [Member]
Change in unvested restricted stock awards
Unvested balance at the beginning of the period (in shares) | shares							34,235
Granted (in shares) | shares							0
Vested (in shares) | shares							(28,610)
Forfeited (in shares) | shares							0
Unvested balance at the end of the period (in shares) | shares					5,625		5,625
Weighted average grant-date fair value
Unvested balance at the end of the period (in dollars per share)							$ 13.60
Granted (in dollars per share)							0
Vested (in dollars per share)							13.60
Forfeited (in dollars per share)							0
Unvested balance at end of the period (in dollars per share)					$ 13.60		$ 13.60
Performance Share Units [Member]
Change in unvested restricted stock awards
Unvested balance at the beginning of the period (in shares) | shares							0
Granted (in shares) | shares	131,250						131,250
Vested (in shares) | shares							(11,666)
Forfeited (in shares) | shares							(8,334)
Unvested balance at the end of the period (in shares) | shares					111,250		111,250
Weighted average grant-date fair value
Unvested balance at the end of the period (in dollars per share)							$ 0
Granted (in dollars per share)							14.68
Vested (in dollars per share)							14.18
Forfeited (in dollars per share)							15.38
Unvested balance at end of the period (in dollars per share)					$ 14.68		$ 14.68
Share-based Compensation Arrangement by Share-based Payment Award, Number of Executives Granted Shares | executives	8
2007 Plan [Member]
Stock-based compensation
Convertible Stock, Conversion Rate									1.61	1.57	1.5
Employee Stock [Member]
Stock-based compensation
Share-based Compensation by Share-based Payment Award, Offering Period				6 months
Share-based Compensation Arrangement by Share-based Payment Award, Purchase Price of Common Stock, Percent				85.00%

MAJOR CUSTOMERS - (Details)

MAJOR CUSTOMERS - (Details) - customer	3 Months Ended		6 Months Ended
	Jun. 26, 2015	Jun. 27, 2014	Jun. 26, 2015	Jun. 27, 2014	Dec. 31, 2014
Revenue [Member] | Less than [Member]
MAJOR CUSTOMERS
Threshold percentage			10.00%
Revenue [Member] | Customer [Member] | CenturyLink [Member]
MAJOR CUSTOMERS
Concentration risk, percentage	19.00%	20.00%
Revenue [Member] | Customer [Member] | Verizon [Member]
MAJOR CUSTOMERS
Concentration risk, percentage			13.00%	24.00%
Accounts receivable balance [Member]
MAJOR CUSTOMERS
Threshold percentage			10.00%
Accounts receivable balance [Member] | Customer [Member]
MAJOR CUSTOMERS
Concentration risk, percentage			34.00%
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. 26, 2015	Jun. 27, 2014	Jun. 26, 2015	Jun. 27, 2014
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	71.00%	71.00%	67.00%	72.00%
Europe, Middle East and Africa [Member]
Revenue by geographic area and by customer
Percentage of total revenue	12.00%	14.00%	13.00%	13.00%
Japan [Member]
Revenue by geographic area and by customer
Percentage of total revenue	9.00%	9.00%	13.00%	8.00%
Other Asia Pacific [Member]
Revenue by geographic area and by customer
Percentage of total revenue	4.00%	4.00%	4.00%	4.00%
Other [Member]
Revenue by geographic area and by customer
Percentage of total revenue	4.00%	2.00%	3.00%	3.00%

COMMITMENTS AND CONTINGENCIES (

COMMITMENTS AND CONTINGENCIES (Details)	Apr. 16, 2015executives
Commitments and Contingencies Disclosure [Abstract]
Number of officers listed as defendants	2