Exhibit 10.20 SECURED PROMISSORY NOTE Sunnyvale, California $250,000.00 September 30, 1996 1. Obligation. The undersigned, Alan I. Fraser ("Borrower") hereby promises to pay to the order of Digital Link Corporation, a California corporation, ("Lender" or "Holder") on or before September 30, 1999, at Lender's principal place of business at 217 Humboldt Court, Sunnyvale, California 94089, or at such other place as Holder may direct, the principal sum of Two Hundred Fifty Thousand Dollars ($250,000.00), together with all interest accrued on unpaid principal, at a rate of six and two one hundredths percent (6.02%) per annum (calculated on the basis of a 360day year), compounded annually, which rate is not less than the minimum rate established pursuant to Section 1274(d) of the Internal Revenue Code of 1986, as amended, as of the date hereof. As used herein, the term "Holder" shall initially mean Lender, and shall subsequently mean each person or entity to whom this Note is duly assigned. If any payment of principal or interest under this Note becomes due and payable on a day other than a business day then the maturity of such payment will be extended to the next succeeding business day, and with respect to the payment of principal, interest thereon will be payable at the rate set forth herein during the period of such extension. 2. Prepayment. Prepayment of unpaid principal and/or interest due under this Note may be made at any time without penalty. Unless otherwise agreed in writing by Holder, all payments will be made in lawful tender of the United States and will be applied (a) first, to the payment of accrued interest, and (b) second, (to the extent that the amount of such prepayment exceeds the amount of all such accrued interest), to the payment of principal. 3. Security. Payment of this Note is secured by a security interest in assets and properties of Borrower granted pursuant to the terms and conditions of a Security Agreement dated of even date herewith among Borrower and Lender, as such may be amended from time to time (the "Security Agreement"). 4. Default; Acceleration of Obligation. Borrower will be deemed to be in default under this Note and the outstanding unpaid principal balance of this Note, together with all interest accrued thereon, will immediately become due and payable in full, without the need for any further action on the part of Holder, upon the occurrence of any of the following events (each an "Event of Default"): (a) upon Borrower's failure to make any payment when due under this Note; (b) upon any sale, transfer or other disposition of the Collateral by Borrower; (c) upon the filing by or against Borrower of any voluntary or involuntary petition in bankruptcy or any petition for relief under the federal bankruptcy code or any other state or federal law for the relief of debtors; provided, however, with respect to an involuntary petition in bankruptcy, such petition has not been dismissed within thirty (30) days after the filing of such petition; (d) upon the execution by Borrower of an assignment for the benefit of creditors or the appointment of a receiver, custodian, trustee or similar party to take possession of Borrower's assets or property; or (e) upon any breach, default or violation by Borrower of any term, condition, obligation, representation or covenant of the Security Agreement. 5. Remedies On Default; Acceleration. Upon any Event of Default, Holder will have, in addition to its rights and remedies under this Note, full recourse against any real, personal, tangible or intangible assets of Borrower, and may pursue any legal or equitable remedies that are available to Holder, and may declare the entire unpaid principal amount of this Note and all unpaid accrued interest under this Note to be immediately due and payable in full. 6. Waiver and Amendment. Any provision of this Note may be amended or modified only by a writing signed by both Borrower and Holder. Except as provided below with respect to waivers by Borrower, no waiver or consent with respect to this Note will be binding or effective unless it is set forth in writing and signed by the party against whom such waiver is asserted. No course of dealing between Borrower and Holder will operate as a waiver or modification of any party's rights or obligations under this Note. No delay or failure on the part of either party in exercising any right or remedy under this Note will operate as a waiver of such right or any other right. A waiver given on one occasion will not be construed as a bar to, or as a waiver of, any right or remedy on any future occasion. 7. Waivers of Borrower. Borrower hereby waives presentment, notice of non-payment, notice of dishonor, protest, demand and diligence. This Note may be amended only by a writing executed by Borrower and Holder. 8. Governing Law. This Note will be governed by and construed in accordance with the internal laws of the State of California as applied to agreements between residents thereof to be performed entirely within such State, without reference to that body of law relating to conflict of laws or choice of law. 9. Severability; Headings. The invalidity or unenforceability of any term or provision of this Note will not affect the validity or enforceability of any other term or provision hereof. The headings in this Note are for convenience of reference only and will not alter or otherwise affect the meaning of this Note. 10. Jurisdiction; Venue. Borrower, by its execution of this Note, hereby irrevocably submits to the in personam jurisdiction of the state courts of the State of California and of the United States District Court for the Northern District of California that are located in Santa Clara County, California, for the purpose of any suit, action or other proceeding arising out of or based upon this Note. 11. Attorneys' Fees. If suit is brought for collection of this Note or enforcement of the Security Agreement, Borrower agrees to pay all reasonable expenses, including attorneys' fees, incurred by Holder in connection therewith whether or not such suit is prosecuted to judgment. 12. Assignment. This Note is freely transferable and assignable by Holder, provided that such transfer is made in compliance with all applicable state and federal securities laws. Any reference to Holder herein will be deemed to refer to any subsequent transferee of this Note at such time as such transferee holds this Note. This Note may not be assigned or delegated by Borrower, whether by voluntary assignment or transfer, operation of law, merger or otherwise. IN WITNESS WHEREOF, Borrower has executed this Note as of the date and year first above written. BORROWER \s\ Alan I. Fraser Alan I. Fraser