EXHIBIT 4.3

                          INVESTORS' RIGHTS AGREEMENT


     This Investors' Rights Agreement (the "Agreement") is entered into as of
the 11th day of June, 1993, by and among International Network Services, a
California corporation (the "Company"), Donald K. McKinney and Rebecca McDaniel
McKinney, Trustees of the McKinney Family Trust, UAD June 2, 1986 (collectively,
"McKinney"), as purchaser of the Company's Series A Preferred Stock ("Series A
Stock"), and the purchasers of the Company's series B Preferred Stock ("Series B
Stock") set forth on Exhibit A of that certain Series B preferred Stock Purchase
Agreement of even date herewith (the "Purchase Agreement").  The purchasers of
the Series B Stock shall be referred to hereinafter as the "Purchasers" and each
individually as a "Purchaser." The Series A Stock and the Series B Stock, taken
together, shall be referred to as the "Preferred Stock."

                                   RECITALS
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     WHEREAS;  As a condition to purchasing shares of Preferred Stock, the
Purchasers and McKinney have requested that the Company extend to them
registration rights, information rights and a right of first refusal as set
forth below.

     NOW, THEREFORE, in consideration of the mutual promises, representations,
warranties, covenants and conditions set forth in this Agreement and in the
Purchase Agreement, the parties mutually agree as follows:

                                  I.  GENERAL
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     1.1  Definitions.  As used in this Agreement the following terms shall have
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the following respective meanings:

     "Holder" means any person owning of record Registrable Securities or any
assignee of record of such Registrable Securities in accordance with Section
2.10 hereof.

     "Register," "registered," and "registration" refer to a registration
effected by preparing and filing a registration statement in compliance with the
Securities Act, and the declaration or ordering of effectiveness of such
registration statement or document.

     "Registrable Securities" means (i) Common Stock acquired from the Company
and held by McKinney, (ii) Common Stock of the Company issued or issuable upon
conversion of the Shares; and (iii) any Common Stock of the Company issued as
(or issuable upon the conversion or exercise of any warrant, right or other
security which is issued as) a dividend or other distribution with respect to,
or in exchange for or in replacement of, such above-described securities.
Notwithstanding the foregoing, Registrable Securities shall not include any
securities sold by a person to the public either pursuant to a registration
statement or Rule 144 or sold in a private transaction in which the transferor's
rights under Article II of this Agreement are not assigned.

     "Registrable Securities then outstanding" shall be the number of shares
determined by calculating the total number of shares of the Company's Common
Stock that are Registrable Securities and either

 
(1) are then issued and outstanding or (2) are issuable pursuant to then
exercisable or convertible securities.

     "Registration Expenses" shall mean all expenses incurred by the Company in
complying with Sections 2.2, 2.3 and 2.4 hereof, including, without limitation,
all registration and filing fees, printing expenses, fees and disbursements of
counsel for the Company, reasonable fees and disbursements of a single special
counsel for the Holders, blue sky fees and expenses and the expense of any
special audits incident to or required by any such registration (but excluding
the compensation of regular employees of the Company which shall be paid in any
event by the Company).

     "Securities Act" shall mean the Securities Act of 1933, as amended.

     "Selling Expenses" shall mean all underwriting discounts and selling
commissions applicable to the sale.

     "Shares" shall mean all outstanding shares of the Company's Preferred
Stock, measured as of the completion of the transactions contemplated by this
Agreement.

     "Form S-3" means such form under the Securities Act as in effect on the
date hereof or any successor registration form under the Securities Act
subsequently adopted by the SEC which permits inclusion or incorporation of
substantial information by reference to other documents filed by the Company
with the SEC.

     "SEC" or "Commission" means the Securities and Exchange Commission.

                  II.  REGISTRATION, RESTRICTIONS ON TRANSFER
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     2.1  Restrictions on Transfer.
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          (a)  Each Holder agrees not to make any disposition of all or any
portion of the Shares (or the Common Stock issuable upon the conversion thereof)
unless and until the transferee has agreed in writing for the benefit of the
Company to be bound by this Section 2.1, provided and to the extent such
Sections are then applicable and:

           (i) There is then in effect a registration statement under the
Securities Act covering such proposed disposition and such disposition is made
in accordance with such registration statement; or

          (ii) (A)  Such Holder shall have notified the Company of the proposed
disposition and shall have furnished the Company with a detailed statement of
the circumstances surrounding the proposed disposition, and (B) if reasonably
requested by the Company, such Holder shall have furnished the Company with an
opinion of counsel, reasonably satisfactory to the Company, that such
disposition will not require registration of such shares under the Securities
Act.  It is agreed that the Company will

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not require Opinions of counsel for transactions made pursuant to Rule 144
except in unusual circumstances.

            (iii)  Notwithstanding the provisions of paragraphs (i) and (ii)
above, no such registration statement or opinion of counsel shall be necessary
for a transfer by a Holder which is (A) a partnership to its partners in
accordance with partnership interests, or (B) to the Holder's family member or
trust for the benefit of an individual Holder, provided the transferee will be
subject to the terms of this Section 2.1 to the same extent as if he were an
original Holder hereunder.

          (b)  Each certificate representing Shares shall (unless otherwise
permitted by the provisions of the Agreement) be stamped or otherwise imprinted
with a legend substantially similar to the following (in addition to any legend
required under applicable state securities laws or as provided elsewhere in the
Agreement):

     THE SECURITIES REPRESENTED HEREBY HAVE NOT BEEN REGISTERED UNDER
     THE SECURITIES ACT OF 1933 (THE "ACT") AND MAY NOT BE OFFERED, 
     SOLD OR OTHERWISE TRANSFERRED, PLEDGED OR HYPOTHECATED UNLESS 
     AND UNTIL REGISTERED UNDER THE ACT OR, IN THE OPINION OF COUNSEL
     OR BASED ON OTHER WRITTEN EVIDENCE IN FORM AND SUBSTANCE 
     SATISFACTORY TO THE ISSUER OF THESE SECURITIES, SUCH OFFER, SALE
     OR TRANSFER, PLEDGE OR HYPOTHECATION IS IN COMPLIANCE THEREWITH.

          (c)  The Company shall be obligated to reissue promptly unlegended
certificates at the request of any holder thereof if the holder shall have
obtained an opinion of counsel (which counsel may be counsel to the Company)
reasonably acceptable to the Company to the effect that the securities proposed
to be disposed of may lawfully be so disposed of without registration,
qualification or legend.

          (d)  Any legend endorsed on an instrument pursuant to applicable state
securities laws and the stop-transfer instructions with respect to such
securities shall be removed upon receipt by the Company of an order of the
appropriate blue sky authority authorizing such removal.

   2.2    Demand Registration.
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          2.2.1  Subject to the conditions of this Section 2.2, if the Company
shall receive at any time after June __, 1995 a written request from the Holders
of more than fifty percent (50%) of the Registrable Securities then outstanding
(the "Initiating Holders") that the Company file a registration statement under
the Securities Act covering the registration of Registrable Securities having an
aggregate offering price to the public, in excess of $7,500,000, then the
Company shall, within thirty (30) days of the receipt thereof, give written
notice of such request to all Holders, and subject to the limitations of Section
2.2.2, effect, as soon as practicable, the registration under the Securities Act
of all Registrable Securities that the Holders request to be registered.

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          2.2.2  If the Initiating Holders intend to distribute the Registrable
Securities covered by their request by means of an underwriting, they shall so
advise the Company as a part of their request made pursuant to this Section 2.2
and the Company shall include such information in the written notice referred to
in Section 2.2.1. In such event, the right of any Holder to include his
Registrable Securities in such registration shall be conditioned upon such
Holder's participation in such underwriting and the inclusion of such Holder's
Registrable Securities in the underwriting (unless otherwise mutually agreed by
a majority in interest of the Initiating Holders and such Holder) to the extent
provided herein.  All Holders proposing to distribute their securities through
such underwriting shall enter into an underwriting agreement in customary form
with the underwriter or underwriters selected for such underwriting by a
majority in interest of the Initiating Holders (which underwriter or
underwriters shall be reasonably acceptable to the Company).  Notwithstanding
any other provision of this Section 2.2, if the underwriter advises the Company
in writing that marketing factors require, a limitation of the number of
securities to be underwritten (including Registrable Securities) then the
Company shall so advise all Holders of Registrable Securities which would
otherwise be underwritten pursuant hereto, and the number of shares that may be
included in the underwriting shall be allocated to the Holders of such
Registrable Securities on a pro rata basis based on the number of Registrable
Securities held by all such Holders (including the Initiating Holders).  Any
Registrable Securities excluded or withdrawn from such underwriting shall be
withdrawn from the registration.

          2.2.3  The Company shall not be obligated to effect more than two (2)
registrations pursuant to this Section 2.2.

          2.2.4  The Company shall not be required to effect a registration
pursuant to this Section 2.2 during the period starting with the date of filing
of, and ending on the date one hundred eighty (180) days following the effective
date of the registration statement pertaining to the initial public offering of
the Company's common stock (the "Initial Offering"), provided that the Company
is making reasonable and good faith efforts to cause such registration statement
to become effective.  In addition, the Company shall not be required to effect a
registration pursuant to this Section 2.2 if within thirty (30) days of receipt
of a written request from Initiating Holders pursuant to Section 2.2.1, the
Company gives notice to the Holders of the Company's intention to file a
registration statement for its Initial Offering within ninety (90) days.

          2.2.5  Notwithstanding the foregoing, if the Company shall furnish
to Holders requesting a registration statement pursuant to this Section 2.2, a
certificate signed by the Chairman of the Board stating that in the good faith
judgment of the Board of Directors of the Company, it would be seriously
detrimental to the Company and its shareholders for such registration statement
to be filed and it is therefore essential to defer the filing of such
registration statement, the Company shall have the right to defer such filing
for a period of not more than ninety (90) days after receipt of the request of
the Initiating Holders; provided that such right to delay a request shall be
exercised by the Company no more than twice in any one-year period.

   2.3    Piggyback Registrations.  The Company shall notify all Holders of
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Registrable Securities in writing at least thirty (30) days prior to the filing
of any registration statement under the Securities Act for purposes of a public
offering of securities of the Company (including, but not limited to,
registration

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statements relating to secondary offerings of securities of the Company, but
excluding registration statements relating to employee benefit plans and
corporate reorganizations) and will afford each such Holder an opportunity to
include in such registration statement all or part of such Registrable
Securities held by such Holder.  Each Holder desiring to include in any such
registration statement all or any part of the Registrable Securities held by it
shall, within twenty (20) days after receipt of the above-described notice from
the Company, so notify the Company in writing.  Such notice shall state the
intended method of disposition of the Registrable Securities by such Holder.  If
a Holder decides not to include all of its Registrable Securities in any
registration statement thereafter filed by the Company, such Holder shall
nevertheless continue to have the right to include any Registrable Securities in
any subsequent registration statement or registration statements as may be filed
by the Company with respect to offerings of its securities, all upon the terms
and conditions set forth herein.

          2.3.1  Underwriting. If the registration statement under which the
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Company gives notice under this Section 2.3 is for an underwritten offering, the
Company shall so advise the Holders of Registrable Securities.  In such event,
the right of any such Holder to be included in a registration pursuant to this
Section 2.3 shall be conditioned upon such Holder's participation in such
underwriting and the inclusion of such Holder's Registrable Securities in the
underwriting to the extent provided herein. All Holders proposing to distribute
their Registrable Securities through such underwriting shall enter into an
underwriting agreement in customary form with the underwriter or underwriters
selected for such underwriting.  Notwithstanding any other provision of the
Agreement, if the underwriter determines in good faith that marketing factors
require a limitation of the number of shares to be underwritten, the number of
shares that may be included in the underwriting shall be allocated, first, to
the Company; second, to the Holders on a pro rata basis based on the total
number of Registrable Securities held by the Holders; and third, to any
shareholder of the Company (other than a Holder) on a pro rata basis.  No such
reduction shall reduce the securities being offered by the Company for its own
account to be included in the registration and underwriting, except that in no
event shall the amount of securities of the selling Holders included in the
registration be reduced below twenty-five percent (25%) of the total amount of
securities included in such registration, unless such offering is the Initial
Offering and such registration does not include shares of any other selling
shareholders, in which event any or all of the Registrable Securities of the
Holders may be excluded in accordance with the immediately preceding sentence.
In no event will shares of any other selling shareholder be included in such
registration which would reduce the number of shares which may be included by
Holders without the written consent of a majority of the Holders of the
Registrable Securities proposed to be sold in the offering.

     2.4  Form S-3 Registration.  In case the Company shall receive from any
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Holder or Holders of Registrable Securities a written request or requests that
the Company effect a registration on Form S-3 and any related qualification or
compliance with respect to all or a part of the Registrable Securities owned by
such Holder or Holders, the Company will:

          2.4.1  promptly give written notice of the proposed registration,
and any related qualification or compliance, to all other Holders of Registrable
Securities; and

          2.4.2  as soon as practicable, effect such registration and all such
qualifications and compliances as may be so requested and as would permit or
facilitate the sale and distribution of all or

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such portion of such Holder's or Holders' Registrable Securities as are
specified in such request, together with all or such portion of the Registrable
Securities of any other Holder or Holders joining in such request as are
specified in a written request given within fifteen (15) days after receipt of
such written notice from the Company; provided, however, that the Company shall
not be obligated to effect any such registration, qualification or compliance
pursuant to this Section 2.4: (i) if Form S-3 is not available for such offering
by the Holders, (ii) if the Holders, together with the holders of any other
securities of the Company entitled to inclusion in such registration, propose to
sell Registrable Securities and such other securities (if any) at an aggregate
price to the public of less than $500,000, (iii) if the Company shall furnish to
the Holders a certificate signed by the Chairman of the Board of Directors of
the Company stating that in the good faith judgment of the Board of Directors of
the Company, it would be seriously detrimental to the Company and its
shareholders for such Form S-3 Registration to be effected at such time, in
which event the Company shall have the right to defer the filing of the Form S-3
registration statement for a period of not more than ninety (90) days after
receipt of the request of the Holder or Holders under this Section 2.4, (iv) if
the Company has, within the twelve (12) month period preceding the date of such
request, already effected two (2) registrations on Form S-3 for the Holders
pursuant to this Section 2.4, or (v) in any particular jurisdiction in which the
Company would be required to qualify to do business or to execute a general
consent to service of process in effecting such registration, qualification or
compliance.

          2.4.3  Subject to the foregoing, the Company shall file a Form S-3
registration statement covering the Registrable Securities and other securities
so requested to be registered as soon as practicable after receipt of the
request or requests of the Holders.  All such Registration Expenses incurred in
connection with registrations requested pursuant to this Section 2.4 after the
first two (2) registrations shall be paid by the selling Holders pro rata in
proportion to the number of shares sold by each.

     2.5  Expenses of Registration.  Except as provided in Section 2.4.3, all
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Registration Expenses incurred in connection with any registration,
qualification or compliance pursuant to Section 2.2, Section 2.3 or Section 2.4
herein shall be borne by the Company.  All Selling Expenses incurred in
connection with any registrations hereunder, shall be borne by the holders of
the securities so registered pro rata on the basis of the number of shares so
registered.  The Company shall not, however, be required to pay for expenses of
any registration proceeding begun pursuant to Section 2.2 or 2.4, the request of
which has been subsequently withdrawn by the Initiating Holders unless (a) the
withdrawal is based upon material adverse information concerning the Company of
which the Initiating Holders were not aware at the time of such request or (b)
the Holders of a majority of Registrable securities agree to forfeit their right
to one requested registration pursuant to Section 2.2 or Section 2.4 (in which
event such right shall be forfeited by all Holders).  If the Holders are
required to pay the Registration Expenses, such expenses shall be borne by the
holders of securities (including Registrable Securities) requesting such
registration in proportion to the number of shares for which registration was
requested.  If the Company is required to pay the Registration Expenses of a
withdrawn offering pursuant to Section 2.5(a), then the Holders shall not
forfeit their rights pursuant to Section 2.2 or Section 2.4 to a demand
registration.

     2.6  Obligations of the Company.  Whenever required to effect the
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registration of any Registrable Securities, the Company shall, as expeditiously
as reasonably possible:

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          2.6.1  Prepare and file with the SEC a registration statement with
respect to such Registrable Securities and use its best efforts to cause such
registration statement to become effective, and, upon the request of the Holders
of a majority of the Registrable Securities registered thereunder, keep such
registration statement effective for up to ninety (90) days.

          2.6.2  Prepare and file with the SEC such amendments and supplements
to such registration statement and the prospectus used in connection with such
registration statement as may be necessary to comply with the provisions of the
Securities Act with respect to the disposition of all securities covered by such
registration statement.

          2.6.3  Furnish to the Holders such number of copies of a prospectus,
including a preliminary prospectus, in conformity with the requirements of the
Securities Act, and such other documents as they may reasonably request in order
to facilitate the disposition of Registrable Securities owned by them.

          2.6.4  Use its best efforts to register and qualify the securities
covered by such registration statement under such other securities or Blue Sky
laws of such jurisdictions as shall be reasonably requested by the Holders,
provided that the Company shall not be required in connection therewith or as a
condition thereto to qualify to do business or to file a general consent to
service of process in any such states or jurisdictions.

          2.6.5  In the event of any underwritten public offering, enter into
and perform its obligations under an underwriting agreement, in usual and
customary form, with the managing underwriter(s) of such offering.  Each Holder
participating in such underwriting shall also enter into and perform its
obligations under such an agreement.

          2.6.6  Notify each Holder of Registrable Securities covered by such
registration statement at any time when a prospectus relating thereto is
required to be delivered under the Securities Act of the happening of any event
as a result of which the prospectus included in such registration statement, as
then in effect, includes an untrue statement of a material fact or omits to
state a material fact required to be stated therein or necessary to make the
statements therein not misleading in the light of the circumstances then
existing.

          2.6.7  Furnish, at the request of a majority of the Holders
participating in the registration, on the date that such Registrable Securities
are delivered to the underwriters for sale, if such securities are being sold
through underwriters, or, if such securities are not being sold through
underwriters, on the date that the registration statement with respect to such
securities becomes effective, (i) an opinion, dated as of such date, of the
counsel representing the Company for the purposes of such registration, in form
and substance as is customarily given to underwriters in an underwritten public
offering and reasonably satisfactory to a majority in interest of the Holders
requesting registration, addressed to the underwriters, if any, and to the
Holders requesting registration of Registrable Securities and (ii) a letter
dated as of such date, from the independent certified public accountants of the
Company, in form and substance as is customarily given by independent certified
public accountants to underwriters in an underwritten public

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offering and reasonably satisfactory to a majority in interest of the Holders
requesting registration, addressed to the underwriters, if any, and to the
Holders requesting registration of Registrable Securities.

     2.7  Termination of Registration Rights.  All registration rights granted
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under this Article II shall terminate and be of no further force and effect
seven (7) years after the date following the Company's Initial Offering.

     2.8  Delay of Registration.  No Holder shall have any right to obtain or 
          ---------------------     
seek an injunction restraining or otherwise delaying any such registration as
the result of any controversy that might arise with respect to the
interpretation or implementation of this Article II.

     2.9  Indemnification.  In the event any Registrable Securities are included
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in a registration statement under Sections 2.2, 2.3 or 2.4:

          2.9.1  To the extent permitted by law, the Company will indemnify
and hold harmless each Holder, the partners, officers and directors of each
Holder, any underwriter (as defined in the Securities Act) for such Holder and
each person, if any, who controls such Holder or underwriter within the meaning
of the Securities Act or the Securities Exchange Act of 1934, as amended, (the
"1934 Act"), against any losses, claims, damages, or liabilities (joint or
several) to which they may become subject under the Securities Act, the 1934 Act
or other federal or state law, insofar as such losses, claims, damages or
liabilities (or actions in thereof) arise out of or are based upon any of the
following statements, omissions or violations (collectively a "Violation") by
the Company: (i) any untrue statement or alleged untrue statement of a material
fact contained in such registration statement, including any preliminary
prospectus or final prospectus contained therein or any amendments or
supplements thereto, (ii) the omission or alleged omission to state therein a
material fact required to be stated therein, or necessary to make the Statements
therein not misleading, or (iii) any violation or alleged violation by the
Company of the Securities Act, the 1934 Act, any state securities law or any
rule or regulation promulgated under the Securities Act, the 1934 Act or any
state securities law in connection with the offering covered by such
registration statement; and the Company will reimburse each such Holder,
partner, officer or director, underwriter or controlling person for any legal or
other expenses reasonably incurred by them in connection with investigating or
defending any such loss, claim, damage, liability or action; provided however,
that the indemnity agreement contained in this Section 2.9.1 shall not apply to
amounts paid in settlement of any such loss, claim, damage, liability or action
if such settlement is effected without the consent of the Company (which consent
shall not be unreasonably withheld), nor shall the Company be liable in any such
case for any such loss, claim, damage, liability or action to the extent that it
arises out of or is based upon a Violation which occurs in reliance upon and in
conformity with written information furnished expressly for use in connection
with such registration by such Holder, partner, officer, director, underwriter
or controlling person of such Holder.

          2.9.2  To the extent permitted by law, each selling Holder will
indemnify and hold harmless the Company, each of its directors, each of its
officers, each person, if any, who controls the Company within the meaning of
the Securities Act, any underwriter and any other Holder selling securities
under such registration statement or any of such other Holder's partners,
directors or officers or any person who controls such Holder, against any
losses, claims, damages or liabilities (joint or

                                      -8-

 
several) to which the Company or any such director, officer, controlling person,
underwriter or other such Holder, or partner, director, officer or controlling
person of such other Holder may become subject under the Securities Act, the
1934 Act or other federal or state law, insofar as such losses, claims, damages
or liabilities (or actions in respect thereto) arise out of or are based upon
any Violation, in each case to the extent (and only to the extent) that such
Violation occurs in reliance upon and in conformity with written information
furnished by such Holder under an instrument duly executed by such Holder and
stated to be specifically for use in connection with such registration; and each
such Holder will reimburse any legal or other expenses reasonably incurred by
the Company or any such director, officer, controlling person, underwriter or
other Holder, or partner, officer, director or controlling person of such other
Holder in connection with investigating or defending any such loss, claim,
damage, liability or action if it is judicially determined that there was such a
Violation; provided, however, that the indemnity agreement contained in this
Section 2.9.2 shall not apply to amounts paid in settlement of any such loss,
claim, damage, liability or action if such settlement is effected without the
consent of the Holder, which consent shall not be unreasonably withheld;
provided further, that in no event shall any indemnity under this Section 2.9
exceed the gross proceeds from the offering received by such Holder.

          2.9.3  Promptly after receipt by an indemnified party under this
Section 2.9 of notice of the commencement of any action (including any
governmental action), such indemnified party will, if a claim in respect thereof
is to be made against any indemnifying party under this Section 2.9, deliver to
the indemnifying party a written notice of the commencement thereof and the
indemnifying party shall have the right to participate in, and, to the extent
the indemnifying party so desires, jointly with any other indemnifying party
similarly noticed, to assume the defense thereof with counsel mutually
satisfactory to the parties; provided, however, that an indemnified party shall
have the right to retain its own counsel, with the fees and expenses to be paid
by the indemnifying party, if representation of such indemnified party by the
counsel retained by the indemnifying party would be inappropriate due to actual
or potential differing interests between such indemnified party and any other
party represented by such counsel in such proceeding.  The failure to deliver
written notice to the indemnifying party within a reasonable time of the
commencement of any such action, if materially prejudicial to its ability to
defend such action, shall relieve such indemnifying party of any liability to
the indemnified party under this Section 2.9, but the omission so to deliver
written notice to the indemnifying party will not relieve it of any liability
that it may have to any indemnified party otherwise than under this Section 2.9.

          2.9.4  If the indemnification provided for in this Section 2.9 is held
by a court of competent jurisdiction to be unavailable to an indemnified party
with respect to any losses, claims, damages or liabilities referred to herein,
the indemnifying party, in lieu of indemnifying such indemnified party
thereunder, shall to the extent permitted by applicable law contribute to the
amount paid or payable by such indemnified party as a result of such loss,
claim, damage or liability in such proportion as is appropriate to reflect the
relative fault of the indemnifying party on the one hand and of the indemnified
party on the other in connection with the Violation(s) that resulted in such
loss, claim, damage or liability, as well as any other relevant equitable
considerations.  The relative fault of the indemnifying party and of the
indemnified party shall be determined by a court of law by reference to, among
other things, whether the untrue or alleged untrue statement of a material fact
or the omission to state a material fact relates to information supplied by the
indemnifying party or by the indemnified party and the parties'

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relative intent, knowledge, access to information and opportunity to correct or
prevent such statement or omission.

          2.9.5  The foregoing indemnity agreements of the Company and Holders
are subject to the condition that, insofar as they relate to any Violation made
in a preliminary prospectus but eliminated or remedied in the amended prospectus
on file with the SEC at the time the registration statement in question becomes
effective or the amended prospectus filed with the SEC pursuant to SEC Rule
424(b) (the "Final Prospectus"), such indemnity agreement shall not inure to the
benefit of any person if a copy of the Final Prospectus was furnished to the
indemnified party and was not furnished to the person asserting the loss,
liability, claim or damage at or prior to the time such action is required by
the Securities Act.

          2.9.6  The obligations of the Company and Holders under this Section
2.9 shall survive the completion of any offering of Registrable Securities in a
registration statement, and otherwise.

     2.10 Assignment of Registration Rights. The rights to cause the Company to
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register Registrable Securities pursuant to this Article II may be assigned by a
Holder to a transferee or assignee of Registrable Securities; provided, however,
that no such transferee or assignee shall be entitled to registration rights
under Sections 2.2, 2.3 or 2.4 hereof unless it acquires at least one hundred
thousand (100,000) shares of Registrable Securities (as adjusted for stock
splits and combinations) and the Company shall, within twenty (20) days after
such transfer, be furnished with written notice of the name and address of such
transferee or assignee and the securities with respect to which such
registration rights are being assigned.  Notwithstanding the foregoing, rights
to cause the Company to register securities may be assigned to any subsidiary,
parent, general partner or limited partner of a Holder.

     2.11 Amendment of Registration Rights.  Any provision of this Article II 
          --------------------------------  
may be amended and the observance thereof may be waived (either generally or in
a particular instance and either retroactively or prospectively), only with the
written consent of the Company and the Holders of at a majority of the
Registrable Securities. Any amendment or waiver effected in accordance with this
Section 2. 11 shall be binding upon each Holder and the Company. By acceptance
of any benefits under this Article II, Holders of Registrable Securities hereby
agree to be bound by the provisions hereunder.

     2.12 Limitation on Subsequent Registration Rights.  After the date of this
          --------------------------------------------                         
Agreement, the Company shall not, without the prior written consent of the
Holders of a majority of the Registrable Securities, enter into any agreement
with any holder or prospective holder of any securities of the Company that
would permit such holder to require that the Company register any securities
held by such holder, or that would permit such holder to include shares in any
registration under Section 2.2, 2.3 or 2.4 of this Agreement unless the
inclusion of such holder's shares would in no way reduce the number of shares
includable in any such registration by any Holder.

     2.13 "Market Stand-Off" Agreement.  If requested by the Company and an
          ----------------------------                                     
underwriter of Common Stock (or other securities) of the Company, each Purchaser
or his permitted assignee holding more than one percent (1%) of the Company's
voting securities shall not sell or otherwise transfer or dispose of any Common
Stock (or other securities) of the Company held by such Purchaser (other than

                                      -10-

 
those included in the registration) for a period specified by the underwriters
not to exceed one hundred eighty (180) days following the effective date of a
mention statement of the Company filed under the Securities Act, provided that:

          (i)   such agreement shall apply only to the Company's Initial
                Offering; and

          (ii)  all officers and directors of the Company enter into similar
                agreements.

     The obligations described in this Section 2.13 shall not apply to a
registration relating solely to employee benefit plans on Form S-1 or Form S-8
or similar forms that may be promulgated in the future, or a registration
relating solely to a Commission Rule 145 transaction on Form S-4 or similar
forms that may be promulgated in the future. The Company may impose stop-
transfer instructions with respect to the shares (or securities) subject to the
foregoing restriction until the end of said one hundred eighty (180) day period.

                        III.  COVENANTS OF THE COMPANY
                              ------------------------

     3.1  Basic Financial Information and Reporting.
          ----------------------------------------- 

          3.1.1  The Company will maintain true books and records of account in
which full and correct entries will be made of all its business transactions
pursuant to a system of accounting established and administered in accordance
with generally accepted accounting principles consistently applied, and will set
aside on its books all such proper accruals and reserves as shall be required
under generally accepted accounting principles consistently applied.

          3.1.2  As soon as practicable after the end of each fiscal year of the
Company, and in any event within 90 days thereafter, the Company will furnish
each Purchaser a consolidated balance sheet of the Company, as at the end of
such fiscal year, and a consolidated statement of income and a consolidated
statement of cash flows of the Company, for such year, all prepared in
accordance with generally accepted accounting principles and setting forth in
each case in comparative form the figures for the previous fiscal year, all in
reasonable detail.  Such financial statements shall be accompanied by a report
and opinion thereon by independent public accountants of national standing
selected by the Company's Board of Directors.

          3.1.3  The Company will furnish each Purchaser, as soon as
practicable after the end of the first, second and third quarterly accounting
periods in each fiscal year of the Company, and in any event within forty-five
(45) days thereafter, a consolidated balance sheet of the Company as of the end
of each such quarterly period, and a consolidated statement of income and a
consolidated statement of cash flows of the Company for such period and for the
current fiscal year to date, prepared in accordance with generally accepted
accounting principles, with the exception that no notes need be attached to such
statements and year-end audit adjustments may not have been made.

          3.1.4  So long as a Purchaser (with its affiliates) shall own not
less than five hundred thousand (500,000) shares of Registrable Securities (a
"Major Purchaser"), the Company will furnish each

                                      -11-

 
such Major Purchaser (i) at least thirty (30) days prior to the beginning of
each fiscal year an annual budget and operating plans for such fiscal year, and
(ii) within thirty (30) days after the end of each month, an unaudited balance
sheet and statements of income and cash flows, prepared in accordance with
generally accepted accounting principles, with the exception that no notes need
be attached to such statements and year-end audit adjustments may not have been
made, but such statement shall set forth applicable budget figures and variances
from budget.

     3.2  Inspection Rights.  Each Major Purchaser shall have the right to visit
          -----------------                                                     
and inspect any of the properties of the Company or any of its subsidiaries, and
to discuss the affairs, finances and accounts of the Company or any of its
subsidiaries with its officers, all at such reasonable times and as often as may
be reasonably requested; provided, however, that the Company shall not be
obligated under this Section 3.2 with respect to a competitor of the Company or
with respect to information which the Board of Directors determines in good
faith is confidential and should not, therefore, be disclosed.

     3.3  Confidentiality of Records.  Each Purchaser agrees to use, and to use
          --------------------------                                           
its best efforts to insure that its authorized representatives use, the same
degree of care as such Purchaser uses to protect its own confidential
information to keep confidential any information furnished to it which the
Company identifies as being confidential or proprietary (so long as such
information is not in the public domain), except that such Purchaser may
disclose such proprietary or confidential information to any partner, subsidiary
or parent of such Purchaser for the purpose of evaluating its investment in the
Company as long as such partner, subsidiary or parent is advised of the
confidentiality provisions of this Section 3.3.

     3.4  Reservation of Common Stock.  The Company will at all times reserve 
          ---------------------------       
and keep available, solely for issuance and delivery upon the conversion of the
Preferred Stock, all Common Stock issuable from time to time upon such
conversion.

     3.5  Stock Vesting.  Unless otherwise approved by the Board of Directors,
          -------------       
all stock and stock equivalents issued after the date of this Agreement to
employees, directors and consultants will be subject to four-year vesting with
no vesting until the end of the first year and monthly vesting thereafter. The
repurchase option, to which all unvested shares of stock shall be subject, shall
provide that upon termination of the employment of the shareholder, with or
without cause, the Company or its assignee (to the extent permissible under
applicable securities laws) retains the option to repurchase at cost any
unvested shares held by such shareholder.

     3.6  Key Man Insurance.  Subject to the approval of the Board of Directors,
          -----------------                                                     
the Company will use its best efforts to obtain and maintain in full force and
effect term life insurance in the amount of one million ($1,000,000) dollars on
the life of Don McKinney naming the Company as beneficiary.

     3.7  Proprietary Information and Inventions Agreement.  The Company shall
          ------------------------------------------------                    
require all employees to execute and deliver a Proprietary Information and
Inventions Agreement substantially in the form attached to the Purchase
Agreement as Exhibit H.

     3.8  Real Property Holding Corporation.  The Company covenants that it will
          ---------------------------------                                     
operate in a manner such that it will not become a "United States real property
holding corporation" as that term is

                                      -12-

 
defined in Section 897(c)(2) of the Internal Revenue Code of 1986, as amended,
and the regulations thereunder ("FIRPTA").  The Company agrees to make
determinations as to its status as a USRPHC, and will file statements concerning
those determinations with the Internal Revenue Service, in the manner and at the
times required under Reg. (S) 1.897-2(h), or any supplementary or successor
provision thereto. Within 30 days of a request from an Purchaser or any of its
partners, the Company will inform the requesting party, in the manner set forth
in Reg. (S) 1.897-2(h)(1)(iv) or any supplementary or successor provision
thereto, whether that party's interest in the Company constitutes a United
States real property interest (within the meaning of Internal Revenue Code
Section 897(c)(1) and the regulations thereunder) and whether the Company has
provided to the Internal Revenue Service all required notices as to its USRPHC
status.

     3.9  Audit Committee.  The Company covenants that it shall take all
          ---------------                                               
appropriate action to create and maintain an Audit Committee consisting of two
members of the Board of Directors. Immediately following the Closing, the
members of the Audit Committee shall be Lawrence Finch and one outside director
approved by the Company and a majority of the holders of the Company's Series B
Stock.

     3.10 Compensation Committee.  The Company covenants that it shall take all
          ----------------------                                               
appropriate action to create and maintain a Compensation Committee consisting of
two members of the Board of Directors.  Immediately following the Closing, the
members of the Compensation Committee shall be Lawrence Finch and McKinney.  The
Company shall not (i) pay any employee annual compensation (including salary,
stock, loans and/or other perquisites) which exceeds $75,000, or (ii) enter into
any transaction with a relative or "affiliate" (as such term is defined under
the Securities Act) of any member of the Company's management, without the
unanimous consent of the Compensation Committee.

     3.11 Termination of Covenants.  All covenants of the Company contained in
          ------------------------                                            
Article III of this Agreement shall expire and terminate as to each Purchaser
after the time of effectiveness of the Company's first firm commitment
underwritten public offering registered under the Securities Act.

                         IV.  RIGHTS OF FIRST REFUSAL.
                              ----------------------- 

     4.1  Subsequent Offerings.  Each Major Purchaser shall have a right of 
          --------------------        
first refusal to purchase its pro rata share of all Equity Securities, as
defined below, that the Company may, from time to time, propose to sell and
issue after the date of this Agreement, other than the Equity Securities
excluded by Section 4.6 hereof. Each Major Purchaser's pro rata share is equal
to the ratio of the number of shares of the Company's Common Stock (including
all shares of Common Stock issued or issuable upon conversion of Preferred
Stock) which such Major Purchaser is deemed to be a holder immediately prior to
the issuance of such Equity Securities to the total number of shares of the
Company's outstanding Common Stock (including all shares of Common Stock
issuable upon conversion of all outstanding shares of Preferred Stock). The term
"Equity Securities" shall mean (i) any stock or similar security of the Company,
(ii) any security convertible, with or without consideration, into any stock or
similar security (including any option to purchase such a convertible security),
(iii) any security carrying any warrant or right to subscribe to or purchase any
stock or similar security or (iv) any such warrant or right.

                                      -13-

 
     4.2  Exercise of Rights.  If the Company proposes to issue any Equity
          ------------------                                              
Securities, it shall give each Major Purchaser written notice of its intention,
describing the Equity Securities, the price and the terms and conditions upon
which the Company proposes to issue the same.  Each Major Purchaser shall have
fifteen (15) days from the giving of such notice to agree to purchase its pro
rata share of the Equity Securities for the price and upon the terms and
conditions specified in the notice by giving written notice to the Company and
stating therein the quantity of Equity Securities to be purchased.
Notwithstanding the foregoing, the Company shall not be required to offer or
sell such Equity Securities to any Major Purchaser who would cause the Company
to be in violation of applicable federal securities laws by virtue of such offer
or sale.

     4.3  Issuance of Equity Securities to Other Persons.  If not all of the 
          ----------------------------------------------    
Major Purchasers elect to purchase their pro rata share of the Equity
Securities, then the Company shall promptly notify in writing the Major
Purchasers who do so elect and shall offer such Major Purchasers the right to
acquire such unsubscribed shares ("Subscription Notice"). The Major Purchasers
shall have five (5) days after receipt of the Subscription Notice to notify the
Company of its election to purchase all or a portion thereof of the unsubscribed
shares. If the Major Purchasers fail to exercise in full the rights of first
refusal, the Company shall have sixty (60) days thereafter to sell the Equity
Securities in respect of which the Major Purchasers' rights were not exercised,
at a price and upon terms and conditions no more favorable to the purchasers
thereof than specified in the Company's notice to the Major Purchasers pursuant
to Section 4.2 hereof. If the Company has not sold such Equity Securities within
such ninety (90) days, the Company shall not thereafter issue or sell any Equity
Securities, without first offering such securities to the Major Purchasers in
the manner provided above.

     4.4  Termination of Rights of First Refusal.  The rights of first refusal
          --------------------------------------                              
established by this Article IV shall terminate upon the closing of an
underwritten public offering of Common Stock of the Company made pursuant to an
effective registration statement under the Securities Act.

     4.5  Transfer of Rights of First Refusal.  The rights of first refusal of
          -----------------------------------                                 
each Major Purchaser under this Article IV may be transferred to any constituent
partner or affiliate of such Major Purchaser, to any successor in interest to
all or substantially all the assets of such Major Purchaser, or to a transferee
who acquires one hundred thousand (100,000) shares of Registrable Securities (as
adjusted for stock splits and combinations), provided, the Company must receive,
within twenty (20) days after such transfer, written notice of the name and
address of such transferee or assignee and the securities with respect to which
the rights of first refusal are being transferred.

     4.6  Excluded Securities.  The rights of first refusal established by this
          -------------------                                                  
Article IV shall have no application to any of the following Equity Securities:

          4.6.1  shares of Common Stock (and/or options, warrants or other
Common Stock purchase rights issued pursuant to such options, warrants or other
rights) issued or to be issued to employees, officers or directors of, or
consultants or advisors to the Company or any subsidiary, pursuant to stock
purchase or stock option plans or other arrangements that are approved by the
Board;

                                      -14-

 
          4.6.2  stock issued pursuant to any rights or agreements outstanding
as of the date of this Agreement, options and warrants outstanding as of the
date of this Agreement, and stock issued pursuant to any such rights or
agreements granted after the date of this Agreement, provided that the rights of
first refusal established by this Article IV applied with respect to the initial
sale or grant by the Company of such rights or agreements;

          4.6.3  any Equity Securities issued pursuant to a merger,
consolidation, acquisition or similar business combination;

          4.6.4  any Equity Securities that are issued by the Company as part of
an underwritten public offering referred to in Section 4.4 hereof;

          4.6.5  shares of Common Stock issued in connection with any stock
split, stock dividend or recapitalization by the Company;

          4.6.6  shares of Common Stock issued upon conversion of the Preferred
Stock;

          4.6.7  any Equity Securities issued pursuant to any equipment leasing
arrangement, or bank financing; and

          4.6.8  securities issued in a transaction with a corporation or other
third party that also involves significant other strategic business elements
such as, but not limited to, a joint marketing agreement, a computer software
development agreement or a license agreement.

                              V.  MISCELLANEOUS.
                                  ------------- 

     5.1  Governing Law.  This Agreement shall be governed by and construed 
          -------------         
under the laws of the State of California as applied to agreements among
California residents entered into and to be performed entirely within
California.

     5.2  Survival.  The representations, warranties, covenants, and agreements
          --------                                                             
made herein shall survive any investigation made by any Holder and the closing
of the transactions contemplated hereby. All statements as to factual matters
contained in any certificate or other instrument delivered by or on behalf of
the Company pursuant hereto in connection with the transactions contemplated
hereby shall be deemed to be representations and warranties by the Company
hereunder solely as of the date of such certificate or instrument.

     5.3  Successors and Assigns.  Except as otherwise expressly provided 
          ----------------------            
herein, the provisions hereof shall inure to the benefit of, and be binding
upon, the successors, assigns, heirs, executors, and administrators of the
parties hereto and shall inure to the benefit of and be enforceable by each
person who shall be a holder of Registrable Securities from time to time;
provided, however, that prior to the receipt by the Company of adequate written
notice of the transfer of any Registrable Securities specifying the full name
and address of the transferee, the Company may deem and treat the person listed
as the

                                      -15-

 
holder of such shares in its records as the absolute owner and holder of such
shares for all purposes, including the payment of dividends or any redemption
price.

     5.4  Separability.  In case any provision of the Agreement shall be 
          ------------       
invalid, illegal, or unenforceable, the validity, legality, and enforceability
of the remaining provisions shall not in any way be affected or impaired
thereby.

     5.5  Amendment and Waiver.
          -------------------- 

          5.5.1  Except as otherwise expressly provided, this Agreement may be
amended or modified only upon the written consent of the Company and a majority
of the Holders of Registrable Securities.

          5.5.2  Except as otherwise expressly provided, the obligations of the
Company and the rights of the Holders under this Agreement may be waived only
with the written consent of a majority of the Holders of Registrable Securities.
Except as otherwise expressly provided, the obligations of the Holders and
rights of the Holders and its rights in the Company and McKinney may be waived
only with the Company and McKinney's written consent, respectively.

     5.6  Delays or Omissions . It is agreed that no delay or omission to 
          --------------------       
exercise any right, power, or remedy accruing to any party, upon any breach,
default or noncompliance of any other party under this Agreement shall impair
any such right, power, or remedy, nor shall it be construed to be a waiver of
any such breach, default or noncompliance, or any acquiescence therein, or of
any similar breach, default or noncompliance thereafter occurring. It is further
agreed that any waiver, permit, consent, or approval of any kind or character on
any party's part of any breach, default or noncompliance under the Agreement or
any waiver on such Holder's part of any provisions or conditions of this
Agreement must be in writing and shall be effective only to the extent
specifically set forth in such writing. All remedies, either under this
Agreement, by law, or otherwise afforded to any party hereunder, shall be
cumulative and not alternative.

     5.7  Notices.  All notices required or permitted hereunder shall be in
          -------                                                          
writing and shall be deemed effectively given: (i) upon personal delivery to the
party to be notified, (ii) when sent by confirmed telex or facsimile if sent
during normal business hours of the recipient; if not, then on the next business
day, (iii) five (5) days after having been sent by registered or certified mail,
return receipt requested, postage prepaid, or (iv) one (1) day after deposit
with a nationally recognized overnight courier, specifying next day delivery,
with written verification of receipt.  All communications shall be sent to the
party to be notified at the address as set forth on the signature pages hereof
or at such other address as such party may designate by ten (10) days advance
written notice to the other parties hereto.

     5.8  Attorneys' Fees.  In the event that any dispute among the parties to
          ---------------                                                     
this Agreement should result in litigation, the prevailing party in such dispute
shall be entitled to recover from the losing party all fees, costs and expenses
of enforcing any right of such prevailing party under or with respect to this
Agreement, including without limitation, such reasonable fees and expenses of
attorneys and accountants, which shall include, without limitation, all fees,
costs and expenses of appeals.

                                      -16-

 
     5.9  Titles and Subtitles.  The titles of the sections and subsections of
          --------------------                                                
this Agreement are for convenience of reference only and are not to be
considered in construing this Agreement.

     5.10 Counterparts. This Agreement may be executed in any number of
          ------------                                                 
counterparts, each of which shall be an original, but all of which together
shall constitute one instrument.

                                      -17-

 
     IN WITNESS WHEREOF, the parties hereto have executed this Agreement as of
the date set forth in the first paragraph hereof.

COMPANY:

INTERNATIONAL NETWORK SERVICES
4701 Patrick Henry Drive, Suite 1701
Santa Clara, CA 95054



By:   /s/ Donald K. McKinney
   -----------------------------
      President



DONALD K. MCKINNEY AND REBECCA
MCDANIEL MCKINNEY, TRUSTEES OF THE
MCKINNEY FAMILY TRUST,
UAD JUNE 2, 1986
c/o International Network Services
4701 Patrick Henry Drive, Suite 1701
Santa Clara, CA 95054



/s/ Donald K. McKinney
- -----------------------
Donald K. McKinney



/s/ Rebecca McDaniel McKinney
- ------------------------------
Rebecca McDaniel McKinney



                          INVESTORS' RIGHTS AGREEMENT

                                      -18-

 
                              PURCHASERS:

                                    SIGMA PARTNERS II, L.P.
                                    2894 Sand Hill Road, Ste. 121
                                    Menlo Park, CA 94025

                                    By: Sigma Management II, L.P.
                                    Its General Partner



                                    By: /s/ Lawrence G. Finch
                                        ---------------------------------------
                                            General Partner

                                    SIGMA ASSOCIATES II, L.P.
                                    2884 Sand Hill Road, Ste. 121
                                    Menlo Park, CA 94025

                                    By: Sigma Management II, L.P.
                                    Its General Partner



                                    By: /s/ Lawrence G. Finch
                                        ----------------------------------------
                                            General Partner


                                    SEQUOIA CAPITAL V
                                    3000 Sand Hill Road, Building 4, Ste. 280
                                    Menlo Park, CA 94025

                                    BY: Sequoia Partners (F.R.)
                                    Its General Partner



                                    By: /s/ Douglas Leone
                                        ----------------------------------------
                                            General Partner



                          INVESTORS' RIGHTS AGREEMENT

                                      -19-

 
                                  SEQUOIA I TECHNOLOGY PARTNERS V
                                  3000 Sand Hill Road, Building 4, Ste. 280
                                  Menlo Park, CA 94025
                                  
                                  By: Sequoia Partners (FR)
                                  Its General Partner
                                  
                                  
                                  
                                  By: /s/ Douglas Leone
                                      ----------------------------------------
                                           General Partner
                                  
                                  SEQUOIA XXIII
                                  3000 Sand Hill Road, Building 4, Ste. 280
                                  Menlo Park, CA 94025
                                  
                                  By: Sequoia Partners (FR)
                                  Its General Partner
                                  
                                  
                                  
                                  By: /s/ Douglas Leone
                                      ----------------------------------------
                                           General Partner
                                  
                                  THE BOARD OF TRUSTEES OF THE
                                  LELAND STANFORD JUNIOR UNIVERSITY
                                  c/o Stanford University Investment Management
                                  2770 Sand Hill Road
                                  Menlo Park, CA 94025
                                  
                                  
                                  
                                  By: /s/ Carol Gilmer
                                      ----------------------------------------



                          INVESTORS' RIGHTS AGREEMENT

                                      -20-

 
                                    VERNON R. ANDERSON AND LYSBETH W.
                                    ANDERSON, TRUSTEES OF THE
                                    VERNON R. & LYSBETH W. ANDERSON
                                    FAMILY TRUST, UAD 7/13/83
                                    25225 La Loma Drive
                                    Los Altos Hills, CA 94022



                                    /s/ Vernon R. Anderson
                                    --------------------------------------------
                                    Vernon R. Anderson



                                    /s/ Lysbeth W. Anderson
                                    --------------------------------------------
                                    Lysbeth W. Anderson


                                    /s/ Brenton Warren Anderson
                                    --------------------------------------------
                                    Brenton Warren Anderson
                                    25225 La Loma Drive
                                    Los Altos Hills, CA 94022


                                    /s/ Tracy S. Bloom
                                    --------------------------------------------
                                    Tracy S. Bloom
                                    5168 Shady Avenue
                                    San Jose, CA 95129



                          INVESTORS' RIGHTS AGREEMENT

                                      -21-

 


                FIRST AMENDMENT TO INVESTORS' RIGHTS AGREEMENT
                ----------------------------------------------



     This First Amendment to Investors' Rights Agreement (the "First Amendment")
is entered into as of the 1st day of July 1994 by and among International
Network Services, a California corporation (the "Company"), Donald K. McKinney
and Rebecca McDaniel McKinney, Trustees of the McKinney Family Trust, UAD June
2, 1986 (collectively, "McKinney"), as purchaser of the Company's Series A
Preferred Stock ("Series A Stock"), the purchasers of the Company's Series B
Preferred Stock ("Series B Stock") set forth on Exhibit A of that certain Series
B Preferred Stock Purchase Agreement (the "Series B Purchase Agreement"), the
purchasers of the Company's Series C Preferred Stock ("Series C Stock") set
forth on Exhibit A of that certain Series C Preferred Stock Purchase Agreement
of even date herewith (the "Series C Purchase Agreement"), Cisco Systems as a
purchaser of a warrant to purchase 1,315,789 shares of Series C Preferred Stock
(the "Cisco Warrant") pursuant to the Series C Purchase Agreement, the
purchasers of the warrants to purchase Common Stock (the "Common Warrants")
pursuant to that certain Note and Warrant Purchase Agreement dated as of March
15, 1994, (the "Note and Warrant Purchase Agreement") and Imperial Bank as a
purchaser of a warrant to purchase 63,211 shares of Series C Preferred Stock
(the "Bank Warrant"). The purchasers of the Series B Stock, the Series C Stock,
the Cisco Warrant, the Common Warrants and the Bank Warrant shall be referred to
hereinafter as the "Purchasers" and each individually as a "Purchaser."  The
Series A Stock, the Series B Stock and Series C Stock, taken together, shall be
referred to as the "Preferred Stock.


                                   RECITALS
                                   --------

     A.   The Company, McKinney and the Series B Purchasers previously entered
into the Investors' Rights Agreement to provide McKinney and the Series B
Purchasers with certain registration rights, information rights and a right of
first refusal.

     B.   The Company is entering into a Series C Purchase Agreement as of the
date hereof pursuant to which the Company is issuing Series C Stock and is
obligated to provide the Purchasers with rights under the Investors' Rights
Agreement.

     C.   The Company is issuing the Cisco Warrant to Cisco Systems ("Cisco")
and is obligated to provide Cisco with rights under the Investors' Rights
Agreement.

     D.   The Company is issuing the Common Warrants to purchase shares of the
Company's Common Stock and is obligated to provide purchasers of these Common
Warrants with rights under the Investors' Rights Agreement.

     E.   The Company is issuing the Bank Warrant to Imperial Bank and is
obligated to provide Imperial Bank with rights under the Investors' Rights
Agreement.

 
     NOW, THEREFORE, in consideration of the mutual promises, representations,
warranties, covenants and conditions set forth in this First Amendment, the
Series C Purchase Agreement, the Note and Warrant Purchase Agreement, and the
Imperial Bank Warrant, the parties mutually agree as follows:

     1.   The definition of "Purchaser" shall be deleted from the first
paragraph of the Investors' Rights Agreement and shall be added to Section 1.1
of the Investors' Rights Agreement and shall read in full as follows:

          ""Purchaser" shall mean the purchasers of the Series B Stock, the
          Series C Preferred Stock (the "Series C Stock"), the warrant to
          purchase 1,315,789 shares of Series C Preferred Stock dated July 1,
          1994 issued to Cisco Systems (the "Cisco Warrant"), the warrants to
          purchase Common Stock issued under the Note and Warrant Purchase
          Agreement dated as of March 15, 1994 (the "Common Warrants") and the
          warrant to purchase 63,211 shares of Series C Preferred dated July 1,
          1994 issued to Imperial Bank (the "Bank Warrant")."

     2.   The definition of "Shares" contained in Subsection 1.1 of the
Investors' Rights Agreement is hereby amended to read in full as follows:

          ""Shares" shall mean (i) all outstanding shares of the Company's
          Series A Preferred Stock, Series B Preferred Stock and Series C
          Preferred Stock, (ii) the shares of Series C Preferred Stock issuable
          upon the exercise of the Cisco Warrant and the Bank Warrant, and (iii)
          the shares of Common Stock issuable upon the exercise of the Common
          Warrants."

     3.   Section 2.2.1 Demand Registration. of the Investors' Rights Agreement
                        -------------------                                    
is hereby amended to read in full as follows:

          "Subject to the conditions of this Section 2.2, if the Company shall
          receive at any time after June 30, 1997 a written request from the
          Holders of more than fifty percent (50%) of the Registrable Securities
          then outstanding (the "Initiating Holders") that the Company file a
          registration statement under the Securities Act covering the
          registration of Registrable Securities having an aggregate offering
          price to the public, in excess of $7,500,000, then the Company shall,
          within thirty (30) days of the receipt thereof, give written notice of
          such request to all Holders, and subject to the limitations of Section
          2.2.2, effect, as soon as practicable, the registration under the
          Securities Act of all Registrable Securities that the Holders request
          to be registered; provided however that the Initiating Holders may
          deliver such written request prior to June 30, 1997 so long as at
          least six months have expired from the closing of the Initial Offering
          (as defined below) and the other conditions of Section 2.2 have been
          met."

                                      -2-

 
     4.   A new Section 3.12 shall be added which shall read in full as follows:

          "3.12   Visitation Rights.  Except as set forth below, so long as
                  -----------------                                        
          Cisco Systems holds both at least one million two hundred sixty-five
          thousand (1,265,000) shares of Series C Preferred Stock and at least
          five percent of the outstanding Common Stock on a fully-diluted basis
          (including conversion of all Preferred Stock, exercise of options, but
          no exercise of warrants), the Company shall invite a representative of
          Cisco Systems to attend all meetings of the Company's Board of
          Directors in a nonvoting observer capacity and, in this respect, shall
          give such representative copies of all notices, minutes, consents and
          other materials that are provided generally to the Company's
          directors; provided, however, that the Company reserves the right to
          exclude such representative from access to any material or meeting or
          portion thereof if the Company believes that such exclusion is
          reasonably necessary (a) because of a conflict of interest, (b) to
          preserve the attorney-client privilege, or (c) to protect confidential
          proprietary information.  Such representative may participate in
          discussion of matters brought to the attention of the Board of
          Directors.  Cisco Systems shall have no rights under this Section 3.12
          while the representative of Cisco Systems is serving as a member of
          the Board of Directors of the Company.  The rights set forth in the
          Section 3.12 may not be transferred."

     5.   Section 4.1 Subsequent Offerings. of the Investors' Rights Agreement
                      --------------------                                    
is hereby amended to read in full as follows:

          "Each Major Purchaser shall have a right of first refusal to purchase
          its pro rata share of all Equity Securities, as defined below, that
          the Company may, from time to time, propose to sell and issue after
          the date of this First Amendment, other than the Equity Securities
          excluded by Section 4.6 hereof.  Each Major Purchaser's pro rata share
          is equal to the ratio of the number of shares of the Company's Common
          Stock (including all shares of Common Stock issued or issuable upon
          conversion of Preferred Stock, but excluding any shares issuable
          pursuant to an unexercised warrant) which such Major Purchaser is
          deemed to be a holder immediately prior to the issuance of such Equity
          Securities to the total number of shares of the Company's outstanding
          Common Stock (including all shares of Common Stock issuable upon
          conversion of all outstanding shares of Preferred Stock, but excluding
          any shares issuable pursuant to an unexercised warrant). The term
          "Equity Securities" shall mean (i) any stock or similar security of
          the Company, (ii) any security convertible, with or without
          consideration, into any stock or similar security (including any
          option to purchase such convertible security), (iii) any security
          carrying any warrant or right to subscribe to or purchase any stock or
          similar security of (iv) any such warrant or right."


     6.   A new Section 4.6.9 shall be added which shall read in full as
follows:

                                      -3-

 
          "4.6.9. and the Series C Preferred Stock, (including the Common Stock
          issuable upon conversion thereof) and the warrant to purchase Series C
          Preferred Stock issued to Cisco Systems (including the Series C
          Preferred Stock issuable upon exercise thereof and Common Stock issued
          upon conversion thereof), all issued either pursuant to the Series C
          Preferred Stock Purchase Agreement dated July 1, 1994 or to a
          subsequent purchase agreement entered into prior to August 2, 1994."

     7.   All other provisions of the Investors' Rights Agreement shall remain
in full force and effect.

                                      -4-

 
     IN WITNESS WHEREOF, the parties hereto have entered into this First
Amendment as of the date first set forth above.


COMPANY:

INTERNATIONAL NETWORK SERVICES


650 Castro Street, Suite 260
Mountain View, CA 94041


By:   /s/ Donald K. McKinney
     -------------------------
          President


MCKINNEY:

DONALD K. MCKINNEY AND REBECCA
MCDANIEL MCKINNEY, TRUSTEES OF THE
MCKINNEY FAMILY TRUST, UAD JUNE 2,
1986
c/o International Network Services
650 Castro Street, Suite 260
Mountain View, CA 94041


By:   /s/ Donald K. McKinney
     ------------------------
          Donald K. McKinney


  /s/ Rebecca McDaniel McKinney
 ----------------------------------
          Rebecca McDaniel McKinney

                                      -5-

 
                                   PURCHASERS:


                                   SIGMA PARTNERS II, L.P.
                                   2884 Sand Hill Road, Ste. 121
                                   Menlo Park, CA 94025


                                   By:  Sigma Management II, L.P.
                                        Its General Partner


                                   By:  /s/ Lawrence G. Finch
                                       ----------------------------------
                                            Its General Partner


                                   SIGMA ASSOCIATES II, L.P.
                                   2884 Sand Hill Road, Ste. 121
                                   Menlo Park, CA 94025


                                   By:  Sigma Management II, L.P.
                                        Its General Partner


                                   By:  /s/ Lawrence G. Finch
                                       ----------------------------------
                                            General Partner


                                   SEQUOIA CAPITAL V
                                   3000 Sand Hill Road, Bldg 4, Ste. 280
                                   Menlo Park, CA 94025


                                   By:  Sequoia Partners (FR)
                                        Its General Partner


                                   By:  /s/ Douglas Leone
                                       ---------------------------------
                                            General Partner

                                      -6-

 
                                   SEQUOIA TECHNOLOGY PARTNERS V
                                   3000 Sand Hill Road, Bldg 4, Ste. 280
                                   Menlo Park, CA 94025


                                   By:  Sequoia Partners (FR)
                                        Its General Partner


                                   By:  /s/ Douglas Leone
                                       ---------------------------------
                                            General Partner


                                   SEQUOIA XXIII
                                   3000 Sand Hill Road, Bldg 4, Ste. 280
                                   Menlo Park, CA 94025


                                   By:  Sequoia Partners (FR)
                                        Its General Partner


                                   By:  /s/ Donald T. Valentine
                                       ---------------------------------
                                            General Partner

                                   SEQUOIA XXIV
                                   3000 Sand Hill Road, Bldg 4, Ste. 280
                                   Menlo Park, CA 94025


                                   By:  /s/ Donald T. Valentine
                                       ---------------------------------
                                        Its General Partner


                                   By:  /s/ Donald T. Valentine
                                       ---------------------------------
                                            General Partner

                                      -7-

 
                                   THE BOARD OF TRUSTEES OF THE LELAND 
                                   STANFORD JUNIOR UNIVERSITY
                                   c/o Stanford University Investment Management
                                   2770 Sand Hill Road
                                   Menlo Park, CA 94025



                                   By:  /s/ Carol Gilmer
                                       ---------------------------------------


                                   VERNON R. ANDERSON AND LYSBETH W. 
                                   ANDERSON, TRUSTEES OF THE VERNON R. & 
                                   LYSBETH W. ANDERSON FAMILY TRUST, UAD 
                                   7/13/83
                                   25225 La Loma Drive
                                   Los Altos Hills, CA 94022


                                    /s/ Vernon R. Anderson
                                   -------------------------------------------
                                   Vernon R. Anderson


                                    /s/ Lysbeth W. Anderson
                                   -------------------------------------------
                                   Lysbeth W. Anderson


                                   BRENTON WARREN ANDERSON
                                   25225 La Loma Drive
                                   Los Altos Hills, CA 94022


                                    /s/ Brenton Warren Anderson
                                   -------------------------------------------
                                   Brenton Warren Anderson

                                   TRACY S. BLOOM
                                   5290 Lanagan Street
                                   Colorado Springs, CO  80919



                                   ___________________________________________
                                   Tracy S. Bloom

                                      -8-

 
                                   CISCO SYSTEMS
                                   170 West Tasman Drive
                                   San Jose, CA  95134


                                   By:  /s/ Sally Taylor
                                       ---------------------------------------
                                            Title: Controller


                                   IMPERIAL BANK
                                   226 Airport Parkway, Suite 100
                                   San Jose, CA  95110


                                   By:  /s/
                                       ---------------------------------------
                                           Title: Vice President

                                      -9-

 


                SECOND AMENDMENT TO INVESTORS' RIGHTS AGREEMENT
                -----------------------------------------------


     This Second Amendment to Investors' Rights Agreement (the "Second
Amendment") is entered into as of the 29th day of July 1994 by and among
International Network Services, a California corporation (the "Company"), Donald
K. McKinney and Rebecca McDaniel McKinney, Trustees of the McKinney Family
Trust, UAD June 2, 1986 (collectively, "McKinney"), as purchaser of the
Company's Series A Preferred Stock ("Series A Stock"), the purchasers of the
Company's Series B Preferred Stock ("Series B Stock") set forth on Exhibit A of
that certain Series B Preferred Stock Purchase Agreement dated June 11, 1993
(the "Series B Purchase Agreement"), the purchasers (the "Initial Series C
Purchasers") of the Company's Series C Preferred Stock ("Series C Stock") set
forth on Exhibit A of that certain Series C Preferred Stock Purchase Agreement
dated July 1, 1994 (the "Series C Purchase Agreement"), Cisco Systems, Inc., as
a purchaser of a warrant to purchase 1,315,789 shares of Series C Preferred
Stock (the "Cisco Warrant") pursuant to the Series C Purchase Agreement, the
purchasers of the warrants to purchase Common Stock (the "Common Warrants")
pursuant to that certain Note and Warrant Purchase Agreement dated as of March
15, 1994, (the "Note and Warrant Purchase Agreement"), Imperial Bank as a
purchaser of a warrant to purchase 63,291 shares of Series C Preferred Stock
(the "Bank Warrant") and the additional purchasers (the "Additional Series C
Purchasers") of the Company's Series C Stock set forth on Exhibit A to that
certain First Amendment to the Series C Purchase Agreement of even date
herewith. The Series A Stock, the Series B Stock and Series C Stock, taken
together, shall be referred to as the "Preferred Stock."

                                    RECITALS
                                    --------

     A.   The Company, McKinney, the purchasers of the Series B Stock, the
Initial Series C Purchasers, Cisco Systems, Inc., the purchasers of the Common
Warrants and Imperial Bank previously entered into the Investors' Rights
Agreement, as amended, to provide McKinney, the purchasers of the Series B
Stock, the Initial Series C Purchasers, Cisco Systems, Inc., the purchasers of
the Common Warrants and Imperial Bank with certain registration rights,
information rights and a right of first refusal.

     B.   The Company is entering into the First Amendment to the Series C
Purchase Agreement as of the date hereof pursuant to which the Company is
issuing additional shares of Series C Stock to the Additional Series C
Purchasers and is obligated to provide the Additional Series C Purchasers with
rights under the Investors' Rights Agreement.

     NOW, THEREFORE, in consideration of the mutual promises, representations,
warranties, covenants and conditions set forth in this Second Amendment and the
Amendment to the Series C Purchase Agreement, the parties mutually agree as
follows:

 
     1.   The definition of "Purchaser" set forth in Section 1.1 of the
Investors' Rights Agreement is hereby amended to read in full as follows:

          ""Purchaser" shall mean the purchasers of the Series B Stock, the
          Series C Preferred Stock (the "Series C Stock") issued pursuant to the
          Series C Preferred Stock Purchase Agreement dated July 1, 1994 and the
          First Amendment to the Series C Preferred Stock Purchase Agreement
          dated July 29, 1994, the warrant to purchase 1,315,789 shares of
          Series C Preferred Stock dated July 1, 1994 issued to Cisco Systems
          (the "Cisco Warrant"), the warrants to purchase Common Stock issued
          under the Note and Warrant Purchase Agreement dated as of March 15,
          1994 (the "Common Warrants") and the warrant to purchase 63,291 shares
          of Series C Preferred dated July 1, 1994 issued to Imperial Bank (the
          "Bank Warrant")."

     2.   All other provisions of the Investors' Rights Agreement shall remain
in full force and effect.

                                      -2-

 
     IN WITNESS WHEREOF, the parties hereto have entered into this Second
Amendment as of the date first set forth above.


COMPANY:

INTERNATIONAL NETWORK SERVICES


650 Castro Street, Suite 260
Mountain View, CA 94041


By:   /s/ Donald K. McKinney
     -------------------------------
         President


MCKINNEY:

DONALD K. MCKINNEY AND REBECCA
MCDANIEL MCKINNEY, TRUSTEES OF THE
MCKINNEY FAMILY TRUST, UAD JUNE 2,
1986
c/o International Network Services
650 Castro Street, Suite 260
Mountain View, CA 94041


By:   /s/ Donald K. McKinney
     -------------------------------
         Donald K. McKinney


  /s/ Rebecca McDaniel McKinney
 ----------------------------------
        Rebecca McDaniel McKinney

                                      -3-

 
                              PURCHASERS:                                 
                                                                              
                                                                              
                              SIGMA PARTNERS II, L.P.                         
                              2884 Sand Hill Road, Ste. 121                   
                              Menlo Park, CA 94025                            
                                                                              
                                                                              
                              By:   Sigma Management II, L.P.                 
                                    Its General Partner                       
                                                                              
                                                                              
                              By:    /s/ Lawrence G. Finch                    
                                    ----------------------------------------    
                                    Its General Partner                       
                                                                              
                                                                              
                              SIGMA ASSOCIATES II, L.P.                       
                              2884 Sand Hill Road, Ste. 121                   
                              Menlo Park, CA 94025                            
                                                                              
                                                                              
                              By:   Sigma Management II, L.P.                 
                                    Its General Partner                       
                                                                              
                                                                              
                              By:   /s/ Lawrence G. Finch                     
                                   -----------------------------------        
                                       General Partner                         
                                                                              
                                                                              
                              SEQUOIA CAPITAL V                               
                              3000 Sand Hill Road, Bldg. 4, Ste. 280          
                              Menlo Park, CA 94025                            
                                                                              
                                                                              
                              By:   Sequoia Partners (FR)                     
                                    Its General Partner                       
                                                                              
                                                                              
                              By:    /s/ Doug Leone                           
                                    ----------------------------------------   
                                    General Partner                            

                                      -4-

 
                              SEQUOIA TECHNOLOGY PARTNERS V                    
                              3000 Sand Hill Road, Bldg. 4, Ste. 280           
                              Menlo Park, CA 94025                             
                                                                               
                                                                               
                              By:   Sequoia Partners (FR)                      
                                    Its General Partner                        
                                                                               
                                                                               
                              By:    /s/ Doug Leone                            
                                    ----------------------------------------   
                                    General Partner                            
                                                                               
                                                                               
                              SEQUOIA XXIII                                    
                              3000 Sand Hill Road, Bldg. 4, Ste. 280           
                              Menlo Park, CA 94025                             
                                                                               
                                                                               
                              By:   Sequoia Partners (FR)                      
                                    Its General Partner                        
                                                                               
                                                                               
                              By:    /s/ Doug Leone                            
                                    ----------------------------------------    
                                    General Partner                            
                                                                               
                                                                               
                              SEQUOIA XXIV                                     
                              3000 Sand Hill Road, Bldg. 4, Ste. 280           
                              Menlo Park, CA 94025                             
                                                                               
                                                                               
                              By:    /s/ Doug Leone                            
                                    -----------------------------------        
                                    Its General Partner                        
                                                                               
                                                                               
                              By:    /s/ Doug Leone                            
                                    ----------------------------------------    
                                    General Partner                             

                                      -5-

 
                              THE BOARD OF TRUSTEES OF THE LELAND              
                              STANFORD JUNIOR UNIVERSITY                       
                              c/o Stanford University Investment Management    
                              2770 Sand Hill Road                              
                              Menlo Park, CA 94025                             
                                                                               
                                                                               
                              By:   /s/ Carol Gilmer                           
                                   -----------------------------------------   
                                                                               
                                                                               
                              VERNON R. ANDERSON AND LYSBETH W. ANDERSON,      
                              TRUSTEES OF THE VERNON R. & LYSBETH W.           
                              ANDERSON FAMILY TRUST, UAD 7/13/83               
                              25225 La Loma Drive                              
                              Los Altos Hills, CA 94022                        
                                                                               
                                                                               
                               /s/ Vernon R. Anderson                          
                              ----------------------------------------------   
                              Vernon R. Anderson                               
                                                                               
                                                                               
                               /s/ Lysbeth W. Anderson                         
                              ----------------------------------------------   
                              Lysbeth W. Anderson                              
                                                                               
                                                                               
                              BRENTON WARREN ANDERSON                          
                              25225 La Loma Drive                              
                              Los Altos Hills, CA 94022                        
                                                                               
                                                                               
                               /s/ Brenton Warren Anderson                     
                              ----------------------------------------------   
                              Brenton Warren Anderson                          
                                                                               
                                                                               
                              TRACY S. BLOOM                                   
                              5290 Lanagan Street                              
                              Colorado Springs, CO 80919                       
                                                                               
                                                                               
                               /s/ Tracy S. Bloom                              
                              ----------------------------------------------   
                              Tracy S. Bloom                                   

                                      -6-

 
                              CISCO SYSTEMS                                    
                              170 West Tasman Drive                            
                              San Jose, CA 95134                               
                                                                               
                                                                               
                              By:   ________________________________________   
                                    Title                                      
                                                                               
                                                                               
                              IMPERIAL BANK                                    
                              226 Airport Parkway, Suite 100                   
                              San Jose, CA 95110                               
                                                                               
                                                                               
                              By:    /s/                                       
                                    ----------------------------------------   
                                    Title: Vice President                      
                                                                               
                                                                               
                              ______________________________________________   
                                                                               
                                                                               
                              Canaan Capital Limited Partnership               
                              C/O CANAAN PARTNERS                              
                              2884 Sand Hill Road, Suite 115                   
                              Menlo Park, CA 94025                             
                                                                               
                              By:   Canaan Capital Management L.P.,            
                                    General Partner                            
                                                                               
                              By:   Canaan Capital Partners L.P.,              
                                    General Partner                            
                                                                               
                                                                               
                              By:    /s/ Eric Young                            
                                    ----------------------------------------   
                                    General Partner                            
 
                                      -7-

 
                              Canaan Capital Offshore Limited Partnership, C.V.
                              C/O CANAAN PARTNERS
                              2884 Sand Hill Road, Suite 115
                              Menlo Park, CA 94025

                              By:   Canaan Capital Management L.P.,
                                    General Partner

                              By:   Canaan Capital Partners L.P.,
                                    General Partner


                              By:    /s/ Eric Young
                                    ---------------------------------------   
                                    Title

                              Quai Limited
                              c/o Windlesham Services Limited
                              22A Old Court Place
                              London, England  W84PP


                              By: /s/
                                 -------------------------------------------
                                    Title

                                      -8-

 
                                                                     EXHIBIT 4.3

                THIRD AMENDMENT TO INVESTORS' RIGHTS AGREEMENT
                ----------------------------------------------


     This Third Amendment to Investors' Rights Agreement (the "Third Amendment")
is entered into as of the 18th day of July 1996, by and among International
Network Services, a California corporation (the "Company"), Donald K. McKinney
and Rebecca McDaniel McKinney, Trustees of the McKinney Family Trust, UAD June
2, 1986 (collectively, "McKinney"), as purchaser of the Company's Series A
Preferred Stock ("Series A Stock"), the purchasers of the Company's Series B
Preferred Stock ("Series B Stock") set forth on Exhibit A of that certain Series
B Preferred Stock Purchase Agreement dated June 11, 1993 (the "Series B Purchase
Agreement"), the purchasers (the "Initial Series C Purchasers") of the Company's
Series C Preferred Stock ("Series C Stock") set forth on Exhibit A of that
certain Series C Preferred Stock Purchase Agreement dated July 1, 1994 (the
"Series C Purchase Agreement"), Cisco Systems, Inc., as a purchaser of a warrant
to purchase 1,315,789 shares of Series C Preferred Stock (the "Cisco Warrant")
pursuant to the Series C Purchase Agreement, the purchasers of the warrants to
purchase Common Stock (the "Common Warrants") pursuant to that certain Note and
Warrant Purchase Agreement dated as of March 15, 1994, (the "Note and Warrant
Purchase Agreement"), Imperial Bank as a purchaser of a warrant to purchase
63,291 shares of Series C Preferred Stock (the "Bank Warrant") and the
additional purchasers (the "Additional Series C Purchasers") of the Company's
Series C Stock set forth on Exhibit A to that certain First Amendment to the
Series C Purchase Agreement dated as of July 29, 1994.

                                    RECITALS
                                    --------

     A.  The Holders of Registrable Securities (as defined in the Investors'
Rights Agreement) possess certain registration rights pursuant to the Investors'
Rights Agreement dated as of June 11, 1993, as amended by the First Amendment to
Investors' Rights Agreement dated as of July 1, 1994 and the Second Amendment to
Investors' Rights Agreement dated as of July 29, 1994 ( the "Investors' Rights
Agreement").

     B.  Under Section 2.11 of the Investors' Rights Agreement, the Company and
the Holders of a majority of the Registrable Securities may amend the Investors'
Rights Agreement.

     NOW, THEREFORE, in consideration of the mutual promises, representations,
warranties, covenants and conditions set forth in this Third Amendment, the
parties mutually agree as follows:

 
     1.  Section 2.3 of the Investors' Rights Agreement is hereby amended and
restated to read in full as follows:

          "Piggyback Registrations.  The Company shall notify all Holders of
           -----------------------                                          
          Registrable Securities in writing at least thirty (30) days prior to
          the filing of any registration statement under the Securities Act for
          purposes of a public offering of securities of the Company (including,
          but not limited to, registration statements relating to secondary
          offerings of securities of the Company, but excluding registration
          statements relating to employee benefit plans and corporate
          reorganizations) and will afford each such Holder an opportunity to
          include in such registration statement all or part of such Registrable
          Securities held by such Holder; provided, however, that the Company
          shall not be required to notify Holders of Registrable Securities and
          such Holders shall not be entitled to include Registrable Securities
          in a registration statement relating to the Company's Initial
          Offering, the closing of which occurs on or prior to December 31,
          1996. Each Holder desiring to include in any such registration
          statement all or any part of the Registrable Securities held by it
          shall, within twenty (20) days after receipt of the above-described
          notice from the Company, so notify the Company in writing. Such notice
          shall state the intended method of disposition of the Registrable
          Securities by such Holder. If a Holder decides not to include all of
          its Registrable Securities in any registration statement thereafter
          filed by the Company, such Holder shall nevertheless continue to have
          the right to include any Registrable Securities in any subsequent
          registration statement or registration statements as may be filed by
          the Company with respect to offerings of its securities, all upon the
          terms and conditions set forth herein."

     2.   All other provisions of the Investors' Rights Agreement shall remain
in full force and effect.

 
     IN WITNESS WHEREOF, the parties hereto have entered into this Third
Amendment as of the date first set forth above.


                              COMPANY:

                              INTERNATIONAL NETWORK SERVICES


                              650 Castro Street, Suite 260
                              Mountain View, CA 94041


                              By:   /s/ Kevin J. Laughlin
                                   ----------------------
                              Title:


                              McKINNEY:

                              DONALD K. McKINNEY AND REBECCA
                              McDANIEL McKINNEY, TRUSTEES OF THE
                              McKINNEY FAMILY TRUST, UAD JUNE 2,
                              1986
                              c/o International Network Services
                              650 Castro Street, Suite 260
                              Mountain View, CA 94041


                               By:   /s/ Donald K. McKinney
                                    --------------------------------
                                     Donald K. McKinney


                                /s/ Rebecca McDaniel McKinney
                               -------------------------------------
                                    Rebecca McDaniel McKinney

 
                              SIGMA PARTNERS II, L.P.
                              2884 Sand Hill Road, Ste. 121
                              Menlo Park, CA 94025


                              By:   Sigma Management II, L.P.
                                    Its General Partner


                              By:   /s/ Lawrence G. Finch
                                   ------------------------------
                                    Its General Partner



                              SIGMA ASSOCIATES II, L.P.
                              2884 Sand Hill Road, Ste. 121
                              Menlo Park, CA 94025


                              By:   Sigma Management II, L.P.
                                    Its General Partner


                              By:   /s/ Lawrence G. Finch
                                   ------------------------------
                                    General Partner



                              SEQUOIA CAPITAL V
                              3000 Sand Hill Road, Bldg. 4, Ste. 280
                              Menlo Park, CA 94025


                              By:   Sequoia Partners (FR)
                                    Its General Partner


                              By:   /s/ Douglas Leone
                                   ------------------------------
                                    General Partner

 
                              SEQUOIA TECHNOLOGY PARTNERS V
                              3000 Sand Hill Road, Bldg. 4, Ste. 280
                              Menlo Park, CA 94025


                              By:   Sequoia Partners (FR)
                                    Its General Partner


                              By:     /s/ Douglas Leone
                                     ----------------------------
                                      General Partner



                              SEQUOIA XXIII
                              3000 Sand Hill Road, Bldg. 4, Ste. 280
                              Menlo Park, CA 94025


                              By:   Sequoia Partners (FR)
                                    Its General Partner


                              By:     /s/ Douglas Leone
                                     ----------------------------
                                      General Partner


                              SEQUOIA XXIV
                              3000 Sand Hill Road, Bldg. 4, Ste. 280
                              Menlo Park, CA 94025


                              By:     /s/ Douglas Leone
                                     ----------------------------
                                      Its General Partner


                              By:   
                                     ----------------------------
                                      General Partner

 
                              THE BOARD OF TRUSTEES OF THE LELAND 
                              STANFORD JUNIOR UNIVERSITY
                              c/o Stanford University Investment Management
                              2770 Sand Hill Road
                              Menlo Park, CA 94025


                              By:
                                   ------------------------------


                              VERNON R. ANDERSON AND LYSBETH W. ANDERSON,
                              TRUSTEES OF THE 
                              VERNON R. & LYSBETH W. ANDERSON 
                              FAMILY TRUST, UAD 7/13/83
                              25225 La Loma Drive
                              Los Altos Hills, CA 94022


                              /s/ Vernon R. Anderson TTEE
                              -----------------------------------
                              Vernon R. Anderson


                              -----------------------------------
                              Lysbeth W. Anderson



                              BRENTON WARREN ANDERSON
                              25225 La Loma Drive
                              Los Altos Hills, CA 94022


                              /s/ Brenton Warren Anderson
                              -----------------------------------
                              Brenton Warren Anderson


                              TRACY S. BLOOM
                              5290 Lanagan Street
                              Colorado Springs, CO 80919


                              -----------------------------------
                              Tracy S. Bloom

 
                              CISCO SYSTEMS
                              170 West Tasman Drive
                              San Jose, CA 95134


                              By:     /s/ Donald A. LeBeau
                                     -----------------------------------
                              Title:



                              IMPERIAL BANK
                              226 Airport Parkway, Suite 100
                              San Jose, CA 95110


                              By:
                                    -----------------------------------
                              Title:

                              -----------------------------------------
 


                              Canaan Capital Limited Partnership
                              C/O CANAAN PARTNERS
                              2884 Sand Hill Road, Suite 115
                              Menlo Park, CA 94025

                              By:  Canaan Capital Management L.P.,
                                   General Partner

                              By:  Canaan Capital Partners L.P.,
                                   General Partner


                              By:  /s/ Eric Young
                                   ------------------------------------
                                   General Partner

 
                              Canaan Capital Offshore Limited Partnership, C.V.
                              C/O CANAAN PARTNERS
                              2884 Sand Hill Road, Suite 115
                              Menlo Park, CA 94025

                              By:   Canaan Capital Management L.P.,
                                    General Partner

                              By:   Canaan Capital Partners L.P.,
                                    General Partner


                              By:   /s/ Eric Young
                                    -----------------------------------
                              Title:

                              Quai Limited
                              c/o Windlesham Services Limited
                              22A Old Court Place
                              London, England  W84PP


                              By:
                                    -----------------------------------
                              Title: