<Page>

                                                                     EXHIBIT 4.3

                                  iBASIS, INC.

                                       AND

                         U.S. BANK NATIONAL ASSOCIATION,

                                       AS

                                  WARRANT AGENT

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



                    WARRANT AND REGISTRATION RIGHTS AGREEMENT

                          DATED AS OF JANUARY 29, 2003

<Page>

                    WARRANT AND REGISTRATION RIGHTS AGREEMENT

                                TABLE OF CONTENTS

<Table>
<Caption>
                                                                             PAGE

<S>         <C>                                                                 <C>
Section 1.  Appointment of Warrant Agent.........................................1
Section 2.  Warrant Certificates; Warrant Shares.................................1
Section 3.  Execution of Warrant Certificates and Warrant Share Certificates.....2
Section 4.  Registration and Countersignature....................................2
Section 5.  Transfer and Exchange of Warrants....................................3
Section 6.  Registration of Transfers and Exchanges..............................3
            6.1.   Transfer and Exchange of Physical Warrants....................3
            6.2.   Restrictions on Transfer of Physical Warrants for a
                   Beneficial Interest in a Global Warrant.......................4
            6.3.   Transfer and Exchange of Global Warrants......................4
            6.4.   Transfer of a Beneficial Interest in a Global Warrant for
                   a Physical Warrant............................................5
            6.5.   Restrictions on Transfer and Exchange of Global Warrants......5
            6.6.   Authentication of Definitive Warrants in Absence of
                   Depositary....................................................5
            6.7.   Legends.......................................................6
            6.8.   Cancellation and/or Adjustment of a Global Warrant............6
Section 7.  Issuance of Warrants; Terms of Warrants: Exercise of Warrants........7
            7.1.   Method of Exercise; Payment, Issuance of New Warrant;
                   Transfer and Exchange.........................................7
            7.2.   Warrantholder Representations................................10
            7.3.   Stock Fully Paid; Reservation of Shares......................10
            7.4.   Adjustment of Exercise Price and Number of Shares............11
            7.5.   Adjustments for Consolidation, Merger, Sale of Assets,
                   Reorganization, etc..........................................16
            7.6.   Notice of Adjustments........................................17
            7.7.   No Rights or Liabilities as Stockholder......................17
Section 8.  Registration Rights.................................................17
            8.1.   Demand Registration Rights...................................17
            8.2.   Piggyback Registration Rights................................19
            8.3.   Certain Other Provisions.....................................20
            8.4.   Indemnification and Contribution.............................23
            8.5.   Reports Under Exchange Act...................................26
Section 9.  Definitions.........................................................26
Section 10. Payment of Taxes....................................................30
Section 11. Mutilated or Missing Warrant Certificates and Warrant Share
            Certificates........................................................31
Section 12. Fractional Interests................................................31
Section 13. Merger, Consolidation or Change of Name of Warrant Agent............31
Section 14. Warrant Agent.......................................................32
Section 15. Change of Warrant Agent.............................................35
Section 16. Notices to Company and Warrant Agent................................35
Section 17. Supplements and Amendments..........................................37
Section 18. Successors..........................................................37
Section 19. Survival of Registration Rights Provisions, Warrant Agent
            Provisions..........................................................37
</Table>

<Page>

<Table>
<S>         <C>                                                                 <C>
Section 20. Governing Law; Submission to Jurisdiction: Waiver of Jury Trial.....37
Section 21. Exercise of Rights and Remedies.....................................38
Section 22. Benefits of This Agreement..........................................38
Section 23. Counterparts........................................................38
</Table>

<Page>

     WARRANT AND REGISTRATION RIGHTS AGREEMENT (this "AGREEMENT"), dated as of
January 29, 2003, between iBasis, Inc., a Delaware (the "COMPANY"), and U.S.
Bank National Association, as Warrant Agent (the "WARRANT Agent").

     WHEREAS, the Company proposes to issue Warrants, as hereinafter described
(the "WARRANTS"), which in the aggregate initially entitle the holders of the
Warrants to purchase, at an Initial Exercise Price of $0.65 per share, 3,071,184
shares of Common Stock, par value $0.001 per share, of the Company (representing
5.58% of the Common Stock outstanding on a diluted basis, after giving effect to
the exercise of such Warrants) on the date such Warrants are issued (the Common
Stock issuable on exercise of any Warrant being referred to herein as the
"WARRANT SHARES"), in connection with the execution of the Securities Exchange
Agreement (as amended, supplemented and otherwise modified from time to time,
the "EXCHANGE AGREEMENT") dated as of the date hereof among the Company, iBasis
Global, Inc., the guarantors named therein, the Symphony Funds named therein and
U.S. Bank National Association, as Collateral Agent.

     WHEREAS, each holder of 11.5% Notes due 2005 issued in connection with the
execution of the Exchange Agreement and the consummation of the transactions
thereby (the "NOTES") shall receive its proportionate share of Warrants to
purchase 3,071,184 Warrant Shares.

     WHEREAS, upon exercise of any Warrants, the Warrantholder shall own Warrant
Shares, which shall continue to be subject to the terms of this Agreement.

     WHEREAS, the Warrant Shares shall have registration rights as provided
herein.

     WHEREAS, the Company desires the Warrant Agent to act on behalf of the
Company, and the Warrant Agent is willing so to act, in connection with the
issuance, transfer, exchange and exercise of Warrants, the issue, transfer and
exchange of the Warrant Shares, and the registration rights with respect to such
Warrant Shares, and other matters as provided herein.

     NOW, THEREFORE, in consideration of the premises and the mutual agreements
herein set forth, the parties hereto agree as follows:

     Section 1. APPOINTMENT OF WARRANT AGENT. The Company hereby appoints the
Warrant Agent to act as agent for the Company in accordance with the
instructions set forth hereinafter in this Agreement, and the Warrant Agent
hereby accepts such appointment.

     Section 2. WARRANT CERTIFICATES; WARRANT SHARES. The certificates
evidencing the Warrants (the "WARRANT CERTIFICATES") to be delivered pursuant to
this Agreement shall be in fully registered form only and shall initially be
represented by a global warrant (the "GLOBAL WARRANT"), substantially in the
form of Exhibit A, registered in the name of The Depositary Trust Company (the
"DEPOSITARY") or its nominee and delivered to the Warrant Agent, as custodian
for the Depository and recorded in the book-entry system maintained by the
Depository. Upon written request, a beneficial owner of an interest in the
Global Warrant will be entitled to receive a physical certificate representing
such interest (a "PHYSICAL WARRANT"), as provided in Section 6. The Global
Warrant shall represent such of the outstanding Warrants as shall be specified
therein and each shall provide that it shall represent the aggregate amount of
outstanding Warrants from time to time endorsed thereon and that the aggregate
amount of outstanding Warrants represented thereby may from time to time be
reduced or increased, as appropriate. Any

<Page>

endorsement of the Global Warrant to reflect the amount of any increase or
decrease in the amount of Warrant Shares represented thereby shall be made by
the Warrant Agent and the Depositary in accordance with instructions given by
the holder thereof. The certificates evidencing the Warrant Shares to be
delivered upon exercise of a Warrant (the "WARRANT SHARE CERTIFICATES") shall be
substantially in the form of the specimen certificate attached hereto as Exhibit
B.

     Section 3. EXECUTION OF WARRANT CERTIFICATES AND WARRANT SHARE
CERTIFICATES. Warrant Certificates shall be signed on behalf of the Company by
its President or a Vice President and by its Secretary or an Assistant
Secretary. Each such signature upon the Warrant Certificates may be in the form
of a facsimile signature of the present or any future President, Vice President,
Secretary or Assistant Secretary and may be imprinted or otherwise reproduced on
the Warrant Certificates and for that purpose the Company may adopt and use the
facsimile signature of any person who shall have been President, Vice President,
Secretary or Assistant Secretary, notwithstanding the fact that at the time the
Warrant Certificates shall be countersigned and delivered or disposed of he or
she shall have ceased to hold such office.

     In case any officer of the Company who shall have signed any of the Warrant
Certificates shall cease to be such officer before the Warrant Certificates so
signed shall have been countersigned by the Warrant Agent, or disposed of by the
Company, such Warrant Certificates nevertheless may be countersigned and
delivered or disposed of as though such person had not ceased to be such officer
of the Company; and any Warrant Certificate may be signed on behalf of the
Company by any person who, at the actual date of the execution of such Warrant
Certificate, shall be a proper officer of the Company to sign such Warrant
Certificate, although at the date of the execution of this Warrant Agreement any
such person was not such officer.

     Warrant Certificates shall be dated the date of countersignature by the
Warrant Agent.

     The Warrant Share Certificates shall be executed in accordance with the
by-laws of the Company.

     Section 4. REGISTRATION AND COUNTERSIGNATURE. The Warrants shall be
numbered and shall be registered on the books of the Company maintained at the
principal office of the Warrant Agent in Boston, Massachusetts (the "WARRANT
REGISTER") as they are issued.

     Warrant Certificates shall be manually countersigned by the Warrant Agent
and shall not be valid for any purpose unless so countersigned. The Warrant
Agent shall, upon written instructions of the President, a Vice President, the
Treasurer or the Chief Financial Officer of the Company, initially countersign,
issue and deliver such number of Warrants as are set forth in such written
instructions, and the Warrant Agent shall be fully protected in conclusively
relying on such written instructions. Such written instructions shall not
instruct the Warrant Agent to countersign Warrants entitling the holders thereof
to purchase more than the number of Warrant Shares referred to above in the
first recital hereof. The Warrant Agent shall also countersign and deliver
Warrants as otherwise provided in this Agreement.

     The Company and the Warrant Agent may deem and treat the registered
holder(s) of the Warrant Certificates and the Warrant Shares as the absolute
owner(s) thereof (notwithstanding

                                      - 2 -
<Page>

any notation of ownership or other writing thereon made by anyone), for all
purposes, and neither the Company nor the Warrant Agent shall be affected by any
notice to the contrary.

     Section 5. TRANSFER AND EXCHANGE OF WARRANTs. The Warrant Agent shall from
time to time, subject to the limitations set forth in Section 6, register the
transfer of any outstanding Warrants upon the records to be maintained by it for
that purpose, upon surrender thereof duly endorsed or accompanied (if so
required by it) by a written instrument or instruments of transfer in form
satisfactory to the Warrant Agent, duly executed by the registered Warrantholder
or Warrantholders thereof or by the duly appointed legal representative thereof
or by a duly authorized attorney. Subject to the terms of this Agreement, each
Warrant Certificate may be exchanged for another certificate or certificates
entitling the Warrantholder thereof to purchase a like aggregate number of
Warrant Shares as the certificate or certificates surrendered then entitle such
Warrantholder to purchase. Any Warrantholder desiring to exchange a Warrant
Certificate or Warrant Certificates shall make such request in writing delivered
to the Warrant Agent, and shall surrender, duly endorsed or accompanied (if so
required by the Warrant Agent) by a written instrument or instruments of
transfer in form satisfactory to the Warrant Agent, the Warrant Certificate or
Warrant Certificates to be so exchanged.

     Upon registration of transfer, the Warrant Agent shall countersign and
deliver by certified mail a new Warrant Certificate or Warrant Certificates to
the Persons entitled thereto. The Warrant Certificates may be exchanged at the
option of the Warrantholder thereof, when surrendered at the office or agency of
the Company maintained for such purpose, which initially will be the corporate
trust office of the Warrant Agent in Boston, Massachusetts for another Warrant
Certificate, or other Warrant Certificates of different denominations, of like
tenor and representing in the aggregate the right to purchase a like number of
Warrant Shares.

     No service charge shall be made for any exchange or registration of
transfer of Warrant Certificates, but the Company may require payment of a sum
sufficient to cover any stamp or other tax or other governmental charge that is
imposed in connection with any such exchange or registration of transfer.

     Section 6. REGISTRATION OF TRANSFERS AND EXCHANGES.

          6.1. TRANSFER AND EXCHANGE OF PHYSICAL WARRANTS. When Physical
     Warrants are presented to the Warrant Agent with a request:

          (i)  to register the transfer of the Physical Warrants; or

          (ii) to exchange such Physical Warrants for an equal number of
               Physical Warrants of other authorized denominations,

the Warrant Agent shall register the transfer or make the exchange as requested
if the requirements under this Agreement as set forth in this Section 6 for such
transactions are met; PROVIDED, HOWEVER, that the Physical Warrants presented or
surrendered for registration of transfer or exchange:

                                      - 3 -
<Page>

     (1)  shall be duly endorsed or accompanied by a written instrument of
          transfer in form satisfactory to the Warrant Agent, duly executed by
          the Warrantholder thereof or his attorney duly authorized in writing;
          and

     (2)  in the case of Physical Warrants the offer and sale of which have not
          been registered under the Securities Act, such Physical Warrants shall
          be accompanied, in the sole discretion of the Company, by the
          following additional information and documents, as applicable:

          (A)  if such Physical Warrants are being delivered to the Warrant
               Agent by a holder for registration in the name of such holder,
               without transfer, a certification from such holder to that effect
               (in substantially the form of Exhibit C hereto); or

          (B)  if such Physical Warrants are being transferred to a "qualified
               institutional buyer" (as defined in Rule 144A under the
               Securities Act (a "QUALIFIED INSTITUTIONAL BUYER")) in accordance
               with Rule 144A under the Securities Act., a certification to that
               effect (in substantially the form of Exhibit C hereto).

          6.2. RESTRICTIONS ON TRANSFER OF PHYSICAL WARRANTS FOR A BENEFICIAL
     INTEREST IN A GLOBAL WARRANT. A Physical Warrant may not be exchanged for a
     beneficial interest in a Global Warrant except upon satisfaction of the
     requirements set forth below. Upon receipt by the Warrant Agent of a
     Physical Warrant, duly endorsed or accompanied by appropriate instruments
     of transfer, in form satisfactory to the Warrant Agent, together with:

          (A)  a certification, in substantially the form of Exhibit C hereto,
               that such Physical Warrant is being transferred to a Qualified
               Institutional Buyer; and

          (B)  written instructions directing the Warrant Agent to make, or to
               direct the Depositary to make, an endorsement on the Global
               Warrant to reflect an increase in the aggregate amount of the
               Warrants represented by the Global Warrant,

then the Warrant Agent shall cancel such Physical Warrant and cause, or direct
the Depositary to cause, in accordance with the standing instructions and
procedures existing between the Depositary and the Warrant Agent, the number of
Warrants represented by the Global Warrant to be increased accordingly. If no
Global Warrant is then outstanding, the Company shall issue and the Warrant
Agent shall upon written instructions from the Company authenticate a new Global
Warrant in the appropriate amount.

          6.3. TRANSFER AND EXCHANGE OF GLOBAL WARRANTS. The transfer and
     exchange of Global Warrants or beneficial interests therein shall be
     effected through the Depositary, in accordance with this Agreement
     (including the restrictions on transfer set forth herein) and the
     procedures of the Depositary therefore.

                                      - 4 -
<Page>

          6.4. TRANSFER OF A BENEFICIAL INTEREST IN A GLOBAL WARRANT FOR A
     PHYSICAL WARRANT.

               6.4.1. Any Person having a beneficial interest in a Global
          Warrant may upon request exchange such beneficial interest for a
          Physical Warrant. Upon receipt by the Warrant Agent of written
          instructions or such other form of instructions as is customary for
          the Depositary from the Depositary or its nominee on behalf of any
          person having a beneficial interest in a Global Warrant and upon
          receipt by the Warrant Agent of a written order or such other form of
          instructions as is customary for the Depositary or the person
          designated by the Depositary as having such a beneficial interest
          containing registration instructions and, in the case of any such
          transfer or exchange of a beneficial interest in a Global Warrant the
          offer and sale of which have not been registered under the Securities
          Act, the following additional information and documents:


          (A)  if such beneficial interest is being transferred to the Person
               designated by the Depositary as being the beneficial owner, a
               certification from such person to that effect (in substantially
               the form of Exhibit C hereto); or

          (B)  if such beneficial interest is being transferred to a Qualified
               Institutional Buyer in accordance with Rule 144A under the
               Securities Act, a certification to that effect (in substantially
               the form of Exhibit C hereto),

          then the Warrant Agent will cause, in accordance with the standing
          instructions and procedures existing between the Depositary and the
          Warrant Agent, the aggregate amount of the Global Warrant to be
          reduced and, following such reduction, the Company will execute and,
          upon receipt of an authentication order in the form of an officers'
          certificate, the Warrant Agent will authenticate and deliver to the
          transferee a Physical Warrant.

               6.4.2. Physical Warrants issued in exchange for a beneficial
          interest in a Global Warrant pursuant to this Section 6.4. shall be
          registered in such names and in such authorized denominations as the
          Depositary, pursuant to instructions from its direct or indirect
          participants or otherwise, shall instruct the Warrant Agent in
          writing. The Warrant Agent shall deliver such Physical Warrants to the
          Persons in whose names such Physical Warrants are so registered.

          6.5. RESTRICTIONS ON TRANSFER AND EXCHANGE OF GLOBAL WARRANTS.
     Notwithstanding any other provisions of this Agreement, a Global Warrant
     may not be transferred as a whole except by the Depositary to a nominee of
     the Depositary or by a nominee of the Depositary to the Depositary or
     another nominee of the Depositary or by the Depositary or any such nominee
     to a successor Depositary or a nominee of such successor Depositary.

          6.6. AUTHENTICATION OF DEFINITIVE WARRANTS IN ABSENCE OF DEPOSITARY.
     If at any time the Depositary for the Warrants notifies the Company that
     the. Depositary is

                                      - 5 -
<Page>

     unwilling or unable to continue as Depositary for the Global Warrants and a
     successor Depositary for the Global Warrants cannot be appointed by the
     Company within 90 days after delivery of such notice, then the Company will
     execute, and the Warrant Agent, upon written instructions from the Company
     requesting the authentication and delivery of Physical Warrants as a result
     of the inability to retain a successor Depositary, will authenticate and
     deliver Physical Warrants, in an aggregate number equal to the aggregate
     number of Warrants represented by the Global Warrants, in exchange for such
     holder's beneficial interest in Global Warrants.

          6.7. LEGENDS. For so long as transfer of a Warrant is not permitted
     without registration under the Securities Act, each Warrant Certificate
     evidencing such Warrant (and all Warrants issued in exchange therefor or
     substitution thereof) shall bear a legend substantially to the following
     effect:

          "THIS SECURITY HAS NOT BEEN REGISTERED UNDER THE UNITED STATES
          SECURITIES ACT OF 1933, AS AMENDED (THE "SECURITIES ACT"), AND,
          ACCORDINGLY, MAY NOT BE OFFERED OR SOLD EXCEPT AS SET FORTH BELOW. BY
          ITS ACQUISITION HEREOF, THE HOLDER (1) REPRESENTS THAT IT IS A
          "QUALIFIED INSTITUTIONAL BUYER" (AS DEFINED IN RULE 144A UNDER THE
          SECURITIES ACT), (2) AGREES THAT IT WILL NOT WITHIN TWO YEARS AFTER
          THE ORIGINAL ISSUANCE OF THIS SECURITY RESELL OR OTHERWISE TRANSFER
          THIS SECURITY EXCEPT (A) TO THE ISSUER OR ANY SUBSIDIARY THEREOF, (B)
          TO A QUALIFED INSTITUTIONAL BUYER IN COMPLIANCE WITH RULE 144A UNDER
          THE SECURITIES ACT, OR (C) PURSUANT TO A REGISTRATION STATEMENT WHICH
          HAS BEEN DECLARED EFFECTIVE UNDER THE SECURITIES ACT (AND WHICH
          CONTINUES TO BE EFFECTIVE AT THE TIME OF SUCH TRANSFER) AND (3) AGREES
          THAT IT WILL DELIVER TO EACH PERSON TO WHOM THIS SECURITY IS
          TRANSFERRED A NOTICE SUBSTANTIALLY TO THE EFFECT OF THIS LEGEND."

          6.8. CANCELLATION AND/OR ADJUSTMENT OF A GLOBAL WARRANT. At such time
     as all beneficial interests in a Global Warrant have either been exchanged
     for Physical Warrants, redeemed, repurchased or cancelled, such Global
     Warrant shall be returned to or retained and cancelled by the Warrant
     Agent. At any time prior to such cancellation, if any beneficial interest
     in a Global Warrant is exchanged for Physical Warrants, redeemed,
     repurchased or cancelled, the number of Warrants represented by such Global
     Warrant shall be reduced and an endorsement shall be made on such Global
     Warrant, by the Warrant Agent to reflect such reduction.

               6.8.1. OBLIGATIONS WITH RESPECT TO TRANSFERS AND EXCHANGES OF
          PHYSICAL WARRANTS.

                                      - 6 -
<Page>

               (i)  To permit registrations of transfers and exchanges, the
                    Company shall execute, at the Warrant Agent's request, and
                    the Warrant Agent shall authenticate Physical Warrants and
                    Global Warrants.

               (ii) All Physical Warrants and Global Warrants issued upon any
                    registration, transfer or exchange of Physical Warrants or
                    Global Warrants shall be the valid obligations of the
                    Company, entitled to the same benefits under this Agreement
                    as the Physical Warrants or Global Warrants surrendered upon
                    the registration of transfer or exchange.

               (iii) Prior to due presentment for registration of transfer of
                    any Warrant, the Warrant Agent and the Company may deem and
                    treat the person in whose name any Warrant is registered as
                    the absolute owner of such Warrant, and neither the Warrant
                    Agent nor the Company shall be affected by notice to the
                    contrary.

Section 7. ISSUANCE OF WARRANTS; TERMS OF WARRANTS: EXERCISE OF WARRANTS.

          7.1. METHOD OF EXERCISE; PAYMENT, ISSUANCE OF NEW WARRANT; TRANSFER
     AND EXCHANGE.

               7.1.1. METHOD OF EXERCISE.

                    7.1.1.1. CASH EXERCISE. Subject to the terms of this
               Agreement, each Warrant holder shall have the right to exercise
               the Warrants evidenced by the Warrant Certificates it holds, in
               whole or in part, during normal business hours on any Business
               Day on or prior to the Expiration Date, by surrender of the
               Warrant Certificates held by it to the Company at its principal
               office, accompanied by a subscription substantially in the form
               attached to the Warrant Certificates duly executed by such holder
               and accompanied by (a) wire transfer of immediately available
               funds or (b) certified or official bank check payable to the
               order of the Company, in each case in the amount obtained by
               multiplying (i) the number of shares of Common Stock (without
               giving effect to any adjustment thereof pursuant to the
               provisions of hereof) for which the Warrant is then being
               exercised, as designated in such subscription, by (ii) the
               Initial Exercise Price. Thereupon, such holder shall be entitled
               to receive the number of duly authorized, validly issued, fully
               paid and nonassessable Warrant Shares (or Other Securities)
               determined as provided in Sections 7.4 and 7.5 hereof.

                    7.1.1.2. CONVERSION. Subject to the terms of this Agreement,
               each Warrant holder shall have the right to convert the Warrants
               evidenced by the Warrant Certificates it holds, in whole or in
               part, into Warrant Shares (or Other Securities), during normal
               business hours on any Business Day on or prior to the Expiration
               Date, by surrender of the Warrant Certificates

                                      - 7 -
<Page>

               held by it to the Company at its principal office, accompanied by
               a conversion notice substantially in the form attached to the
               Warrant Certificates duly executed by such holder. Thereupon,
               such holder shall be entitled to receive a number of duly
               authorized, validly issued, fully paid and nonassessable Warrant
               Shares (or Other Securities) equal to:

                    (a) the excess of

                         (i) (x) the number of Warrant Shares (or Other
                    Securities) determined as provided in Sections 7.4 and 7.5
                    hereof which such holder would be entitled to receive upon
                    exercise of such Warrant for the number of Warrant Shares
                    designated in such conversion notice (without giving effect
                    to any adjustment thereof pursuant to the provisions hereof)
                    for which the Warrant is then being exercised, as designated
                    in such conversion notice, MULTIPLIED BY (y) the Current
                    Market Price of each such Warrant Share (or such Other
                    Securities) so receivable upon such exercise

               OVER

                         (ii) (x) the number of Warrant Shares (without giving
                    effect to any adjustment thereof pursuant to the provisions
                    hereof) which such holder would be entitled to receive upon
                    exercise of such Warrant for the number of Warrant Shares
                    designated in such conversion notice (without giving effect
                    to any adjustment thereof pursuant to the provisions
                    hereof), MULTIPLIED BY (y) the Initial Exercise Price

               DIVIDED BY

                         (b) such Current Market Price of each such Warrant
                    Share (or Other Securities).

                    7.1.1.3. NOTE TENDER. Subject to the terms of this
               Agreement, each Warrant holder shall have the right to exercise
               the Warrants evidenced by the Warrant Certificates it holds, in
               whole or in part, during normal business hours on any Business
               Day on or prior to the Expiration Date, by surrender of the
               Warrant Certificates held by it to the Company at its principal
               office, accompanied by a note tender notice substantially in the
               form attached to the Warrant Certificates duly executed by such
               holder and accompanied by a Note. Thereupon, such holder shall be
               deemed to have exercised the Warrants represented by such Warrant
               Certificates for the number of Warrant Shares (up to the maximum
               number of Warrant Shares set forth on the face of such Warrant
               Certificates and without giving effect to any adjustment thereof
               pursuant to the provisions hereof) obtained by dividing (i) the
               sum of the outstanding face amount of such Note (or such lesser
               amount indicated on the note tender notice) PLUS any

                                      - 8 -
<Page>

               cash or payment-in-kind interest accrued on such Note, PLUS any
               accrued prepayment penalty or premium by (ii) the Initial
               Exercise Price. Thereupon, such holder shall be entitled to
               receive the number of duly authorized, validly issued, fully paid
               and nonassessable Warrant Shares (or Other Securities) determined
               as provided in Sections 7.4 and 7.5.

               7.1.2. WHEN EXERCISE EFFECTIVE. Each exercise of a Warrant shall
          be deemed to have been effected immediately prior to the close of
          business on the Business Day on which such Warrant shall have been
          surrendered to the Company at the office of the Warrant Agent and
          payment made as provided in Section 7.1.1 hereof, and at such time the
          Person or Persons in whose name or names any certificate or
          certificates for Warrant Shares (or Other Securities) shall be
          issuable upon such exercise as provided in Section 7.1.3 hereof shall
          be deemed to have become the holder or holders of record thereof.

               7.1.3. DELIVERY OF STOCK CERTIFICATES, ETC. As soon as
          practicable, but no later than five Business Days after each exercise
          of a Warrant, in whole or in part, except as otherwise provided in
          Section 7.1.4, the Company at its expense (including the payment by it
          of any applicable issue taxes) will cause to be issued in the name of
          and delivered to the holder thereof or, subject to the provisions of
          the Exchange Agreement, as such holder (upon payment by such holder of
          any applicable transfer taxes and subject to Section 6 above) may
          direct:

                    (a) a certificate or certificates for the number of duly
               authorized, validly issued, fully paid and nonassessable Warrant
               Shares (or Other Securities) to which such holder shall be
               entitled upon such exercise plus, in lieu of any fractional share
               to which such holder would otherwise be entitled, cash in an
               amount equal to the same fraction of the Current Market Price per
               share on the Business Day immediately preceding the date of such
               exercise; and

                    (b) in case such exercise is in part only, a new Warrant or
               Warrants of like tenor, dated the date hereof and calling in the
               aggregate on the face or faces thereof for the number of Warrant
               Shares equal (without giving effect to any adjustment thereof
               pursuant to the terms hereof) to the number of such shares called
               for on the face of such Warrant minus the number of such shares
               designated by the holder upon such exercise as provided in
               Section 7.1.1 hereof; and

                    (c) in case such exercise is by a partial tender of Notes,
               replacement Notes in the amount of the outstanding principal
               balance thereof, dated the date as of which all accrued interest
               thereon shall then most recently have been paid (including any
               payment effected in connection with a Note tender by including
               such accrued interest in the calculation provided by Section
               7.1.3(i)).

                                      - 9 -
<Page>

               7.1.4. CASH CLOSE OUT. Upon the exercise of the Warrants as
          provided in Section 7.1.1, the Company may elect either (i) to comply
          with the requirements of Section 7.1.3(a) with respect to the issuance
          of Warrant Shares in connection with such exercise or (ii) upon
          written notice to the holder not more than two Business Days following
          the date of exercise, to pay to the holder an amount equal to the
          Market Price for each Warrant Share issuable upon such exercise (the
          "CASH CLOSE OUT") in lieu of issuing such Warrant Shares. Any Cash
          Close Out made under this Section 7.1.4 shall be paid within two
          Business Days of the exercise of such Warrant by (a) wire transfer of
          immediately available funds or (b) certified or official bank check
          payable to the order of the holder.

               7.1.5. COMPANY TO REAFFIRM OBLIGATIONS. The Company will, at the
          time of or at any time after each exercise of a Warrant, upon the
          request of the holder hereof, acknowledge in writing its continuing
          obligation to afford to such holder all rights to which such holder
          shall continue to be entitled after such exercise in accordance with
          the terms of this Warrant Agreement and the Warrants; provided that if
          any such holder shall fail to make any such request, the failure shall
          not affect the continuing obligation of the Company to afford such
          rights to such holder.

          7.2. WARRANTHOLDER REPRESENTATIONS. Prior to the exercise of any
     Warrant, the Warrantholder must represent and warrant to the Company, in
     writing, as follows:

               (i)   it is acquiring the Warrant Shares for its own account for
                     investment and not with a view to, or for sale in
                     connection with, any distribution thereof, nor with any
                     present intention of distributing or selling the same; and
                     the Warrantholder has no present or contemplated agreement,
                     undertaking, arrangement, obligation, indebtedness or
                     commitment providing for the disposition thereof;

               (ii)  the Warrantholder is an "accredited investor" as defined in
                     Rule 501(a) under the Securities Act; and

               (iii) the Warrantholder has made such inquiry concerning the
                     Company and its business and personnel as it has deemed
                     appropriate; and the Warrantholder has sufficient knowledge
                     and experience in finance and business that is capable of
                     evaluating the risks and merits of investment in the
                     Company.

          7.3. STOCK FULLY PAID; RESERVATION OF SHARES. The Company represents,
     warrants, covenants and agrees that all Warrant Shares which may be issued
     upon the exercise of the rights represented by the Warrants will, upon
     issuance and payment therefor in accordance with the terms of the Warrant,
     be duly authorized, validly issued, fully paid and non-assessable. The
     Company further covenants and agrees that during the period within which
     the rights represented by the Warrants may be exercised, the Company will
     at all times have authorized and reserved solely for the purpose of the
     issuance upon

                                     - 10 -
<Page>

     exercise of the Warrants a sufficient number of shares of Common Stock to
     provide for the exercise of the rights represented by the Warrants.

     The Company will (a) not increase the par value of any shares of Common
Stock receivable upon the exercise of any Warrant above the amount payable
therefor upon such exercise immediately prior to such increase in par value, (b)
take all such action as may be necessary or appropriate in order that the
Company may validly and legally issue fully paid and non-assessable Warrant
Shares upon the exercise of each Warrant, and (c) use its reasonable efforts to
obtain all such authorizations, exemptions or consents from any public
regulatory body having jurisdiction thereof as may be necessary to enable the
Company to perform its obligations under this Agreement and each Warrant.
Without limiting the generality of the foregoing, the Company will from time to
time take all such action as may be required to assure that the par value per
share, if any, of the Common Stock is at all times equal to or less than the
lowest quotient obtained by dividing the then current exercise price of each
Warrant by the number of Warrant Shares into which such Warrant can from time to
time be exercised.

          7.4. ADJUSTMENT OF EXERCISE PRICE AND NUMBER OF SHARES.

               7.4.1. GENERAL; NUMBER OF SHARES; EXERCISE PRICE. The number of
          Warrant Shares which the holder of a Warrant shall be entitled to
          receive upon each exercise thereof shall be determined by multiplying
          the number of shares of Common Stock which would otherwise (but for
          the provisions of this Section 7.4) be issuable upon such exercise, as
          designated by the holder hereof pursuant to Section 7.1.1 hereof, by a
          fraction of which (a) the numerator is the Initial Exercise Price of
          such Warrant and (b) the denominator is the Exercise Price of such
          Warrant in effect on the date of such exercise. The "Exercise Price"
          shall initially be the Initial Exercise Price, and shall be adjusted
          and readjusted from time to time as provided in this Section 7.4 and,
          as so adjusted or readjusted, shall remain in effect until a further
          adjustment or readjustment thereof is required by this Section 7.4.

               7.4.2. ISSUANCE OF ADDITIONAL WARRANTS DUE TO ISSUANCE OF
          ADDITIONAL COMMON SHARES. In case the Company at any time or from time
          to time after the date hereof shall issue or sell Additional Common
          Shares (including Additional Common Shares deemed to be issued
          pursuant to Section 7.4.4, 7.4.5. or 7.4.5), other than an Excluded
          Issuance, without consideration or for a consideration per share less
          than the Fair Market Value, then in each such case such Exercise Price
          shall be reduced (but not increased), concurrently with such issue or
          sale, to a price (calculated to the nearest 0.000001 of a cent)
          determined by multiplying the Exercise Price in effect immediately
          prior to such issue or sale (the "ANTIDILUTION PRICE") by a fraction:

                    (a) the numerator of which shall be the sum of (i) the
               number of shares of Common Stock outstanding immediately prior to
               such issue or sale MULTIPLIED BY the Antidilution Price PLUS (ii)
               the consideration, if any, deemed received by the Company upon
               such issue or sale; and

                                     - 11 -
<Page>

                    (b) the denominator of which shall be the product of (i) the
               total number of shares of Common Stock deemed to be outstanding
               immediately after such issue or sale MULTIPLIED BY (ii) the
               Antidilution Price.

          In each case, the number of shares of Common Stock shall be calculated
          in accordance with Section 7.4.8.

               7.4.3. DIVIDENDS AND DISTRIBUTIONS. In case the Company at any
          time or from time to time after the date hereof shall declare, order,
          pay or make a dividend or other distribution (including without
          limitation any distribution of additional stock or other securities or
          property or Options, by way of dividend or spin-off, distribution,
          reclassification, recapitalization or similar corporate rearrangement
          or otherwise) on the shares of Common Stock, other than a dividend
          payable in (or otherwise deemed to be an issuance of) Additional
          Common Shares or periodic cash dividends declared and paid in the
          ordinary course of business, then, and in each such case, the holder
          of a Warrant shall receive, upon the exercise of such Warrant at any
          time on or after such record date, the number of Warrant Shares to be
          received upon exercise of such Warrant determined as provided herein
          and, in addition and without further payment, and without any
          additional action required on the part of such holder, such dividend
          or other distribution to which such holder would have been entitled by
          way of such dividend or other distribution and subsequent dividends
          and other distributions through the date of exercise as if such holder
          (x) had exercised such Warrant immediately prior to such record date
          and (y) had retained such dividend or other distribution in respect of
          the shares of Common Stock and all subsequent dividends and other
          distributions of any nature whatsoever in respect of any stock or
          securities paid as dividends and other distributions and originating
          directly or indirectly from such shares of Common Stock.

               7.4.4. TREATMENT OF OPTIONS AND CONVERTIBLE SECURITIES. In case
          the Company at any time or from time to time after the date hereof
          shall issue, sell, grant or assume, or shall fix a record date for the
          determination of holders of any class of securities entitled to
          receive, any Options or Convertible Securities, then, and in each such
          case, the maximum number of Additional Common Shares (as set forth in
          the instrument relating thereto, without regard to any provisions
          contained therein for a subsequent adjustment of such number the
          purpose of which is to protect against dilution) at any time issuable
          upon the exercise of such Options or, in the case of Convertible
          Securities and Options therefor, the conversion or exchange of such
          Convertible Securities, shall be deemed to be Additional Common Shares
          issued as of the time of such issue, sale, grant or assumption or, in
          case such a record date shall have been fixed, as of the close of
          business on such record date. Notwithstanding the foregoing, this
          Section 7.4.4 shall not apply to (I.E., there shall not be a deemed
          issuance of Additional Common Shares with respect to) the issuance,
          sale, grant or assumption of, or fixing of a record date for
          determination of entitlement to receive, an Excluded Issuance. In
          addition:

                                     - 12 -
<Page>

                    (a) no further adjustment of the Exercise Price shall be
               made upon the exercise of any Options or the conversion or
               exchange of Convertible Securities and the consequent issue or
               sale of Convertible Securities or shares of Common Stock;

                    (b) if Options or Convertible Securities by their terms
               provide, with the passage of time or otherwise, for any increase
               in the consideration payable to the Company, or decrease in the
               number of Common Shares issuable, upon the exercise, conversion
               or exchange thereof (by change of rate or otherwise), the
               Exercise Prices computed upon the original issue, sale, grant or
               assumption thereof (or upon the occurrence of the record date
               with respect thereto), and any subsequent adjustments based
               thereon, shall, upon any such increase or decrease becoming
               effective, be recomputed to reflect such increase or decrease
               insofar as it affects such Options, or the rights of conversion
               or exchange under such Convertible Securities, which are
               outstanding at such time;

                    (c) if the consideration provided for in any Option or the
               additional consideration, if any, payable upon the conversion or
               exchange of any Convertible Security shall be reduced, or the
               ratio at which any Option is exercisable or any Convertible
               Security is convertible into or exchangeable for shares of Common
               Stock shall be increased, at any time under or by reason of
               provisions with respect thereto designed to protect against
               dilution, then, effective concurrently with each such change, the
               Exercise Price then in effect shall first be adjusted to
               eliminate the previous effects (if any) of the issuance (or
               deemed issuance) of such Option or Convertible Security on the
               Exercise Price and then readjusted as if such Option or
               Convertible Security had been issued on the date of such change
               with the terms in effect after such change; and

                    (d) upon the expiration (or purchase by the Company and
               cancellation or retirement) of any Options which shall not have
               been exercised, or the expiration of any rights of conversion or
               exchange under any Convertible Securities which (or purchase by
               the Company and cancellation or retirement of any Convertible
               Securities the rights of conversion or exchange under which)
               shall not have been exercised, the Exercise Price computed upon
               the original issue, sale, grant or assumption thereof (or upon
               the occurrence of the record date with respect thereto), and any
               subsequent adjustments based thereon, shall, upon (and effective
               as of) such expiration (or such cancellation or retirement, as
               the case may be), be recomputed as if:

                         (i) in the case of Options or Convertible Securities,
                    the only Additional Common Shares issued or sold were the
                    Additional Common Shares, if any, actually issued or sold
                    upon the exercise of such Options or the conversion or
                    exchange of such Convertible Securities and the
                    consideration received therefor was

                                     - 13 -
<Page>

                    the consideration actually received by the Company for the
                    issue, sale, grant or assumption of all such Options,
                    whether or not exercised, plus the additional consideration
                    actually received by the Company upon any exercise thereof,
                    or the consideration actually received by the Company for
                    the issue or sale of all such Convertible Securities,
                    whether or not actually converted or exchanged, plus the
                    additional consideration actually received by the Company
                    upon any conversion or exchange thereof, and

                         (ii) in the case of Options for Convertible Securities,
                    only the Convertible Securities, if any, actually issued or
                    sold upon the exercise of such Options were issued at the
                    time of the issue, sale, grant or assumption of such
                    Options, and the consideration received by the Company for
                    the Additional Common Shares deemed to have then been issued
                    was the consideration actually received by the Company for
                    the issue, sale, grant or assumption of all such Options,
                    whether or not exercised, plus the consideration deemed to
                    have been received by the Company (pursuant to Section 7.4.6
                    hereof) upon the issue or sale of such Convertible
                    Securities with respect to which such Options were actually
                    exercised.

               7.4.5. TREATMENT OF STOCK DIVIDENDS, STOCK SPLITS, ETC. In case
          the Company at any time or from time to time after the date hereof
          shall declare or pay any dividend on the shares of Common Stock
          payable in shares of Common Stock or other securities, or shall effect
          a subdivision of the outstanding shares of Common Stock into a greater
          number of shares of Common Stock (by reclassification or otherwise
          than by payment of a dividend in shares of Common Stock), then, and in
          each such case, Additional Common Shares shall be deemed to have been
          issued (a) in the case of any such dividend, immediately after the
          close of business on the record date for the determination of holders
          of any class of securities entitled to receive such dividend, or (b)
          in the case of any such subdivision, at the close of business on the
          day immediately prior to the day upon which such corporate action
          becomes effective.

               7.4.6. COMPUTATION OF CONSIDERATION. For the purposes of this
          Section 7.4:

                    (a) the consideration for the issue or sale of any
               Additional Common Shares shall, irrespective of the accounting
               treatment of such consideration, be computed at the fair value
               thereof at the time of such issue or sale, as determined in good
               faith by the Board, without deduction for any expenses paid or
               incurred by the Company or any commissions or compensations paid
               or concessions or discounts allowed to underwriters, dealers or
               others performing similar services in connection with such issue
               or sale. In the event Additional Common Shares are issued or sold
               together with other stock or securities or other assets of the
               Company for a

                                     - 14 -
<Page>

               consideration which covers both, the consideration for the issue
               or sale of Additional Common Shares shall be the portion of such
               consideration so received, computed as provided in this Section
               7.4.6, allocable to such Additional Common Shares, all as
               determined in good faith by the Board. Notwithstanding the
               foregoing, if Additional Common Shares are issued (i) to an
               Affiliate of the Company or (ii) in connection with any
               acquisition by the Company of stock or assets of a third party or
               parties, the fair value of such Additional Common Shares at the
               time of such issue or sale shall be the value as determined in
               good faith by the Board, except that in the case of issuances to
               Affiliates of the Company, or in connection with acquisitions by
               the Company of stock or assets of a third party, such fair value
               shall be the value set forth in an opinion of independent
               accountants or investment bankers selected by the Company, if
               such engagement is reasonably requested by the Majority
               Warrantholders;

                    (b) Additional Common Shares deemed to have been issued
               pursuant to Section 7.4.4 hereof shall be deemed to have been
               issued for a consideration per share determined by dividing:

                         (i) the total amount of consideration, if any, received
                    and/or receivable by the Company as direct consideration for
                    the issue, sale, grant or assumption of the Options or
                    Convertible Securities in question, plus the minimum
                    aggregate amount of additional consideration (as set forth
                    in the instruments relating thereto, without regard to any
                    provision contained therein for a subsequent adjustment of
                    such consideration the purpose of which is to protect
                    against dilution) payable to the Company upon the exercise
                    in full of such Options or the conversion or exchange of
                    such Convertible Securities or, in the case of Options for
                    Convertible Securities, the exercise of such Options for
                    Convertible Securities and the conversion or exchange of
                    such Convertible Securities, in each case computing such
                    consideration as provided in the foregoing clause (a), by

                         (ii) the maximum number of shares of Common Stock (as
                    set forth in the instruments relating thereto, without
                    regard to any provision contained therein for a subsequent
                    adjustment of such number the purpose of which is to protect
                    against dilution) issuable upon the exercise of such Options
                    or the conversion or exchange of such Convertible
                    Securities; and

                    (c) Additional Common Shares deemed to have been issued
               pursuant to Section 7.4.5 hereof shall be deemed to have been
               issued for no consideration, unless the Company actually receives
               consideration for any such issuance.

                                     - 15 -
<Page>

               7.4.7. ADJUSTMENTS FOR COMBINATIONS, ETC. In case the outstanding
          shares of Common Stock shall be combined or consolidated, by
          reclassification or otherwise, into a lesser number of shares of
          Common Stock, the Exercise Price in effect immediately prior to such
          combination or consolidation shall, concurrently with the
          effectiveness of such combination or consolidation, be proportionately
          increased.

               7.4.8. SHARES DEEMED OUTSTANDING. Unless otherwise specifically
          provided herein, for all purposes of the computations to be made
          pursuant to this Section 7.4, there shall be deemed to be outstanding
          all shares of Common Stock issuable pursuant to the exercise of
          Options and conversion of Convertible Securities outstanding at the
          time as of which such computation is made. No adjustment shall be made
          in the Exercise Price upon the issuance of shares of Common Stock
          pursuant to Options and Convertible Securities so deemed to be
          outstanding, but this Section 7.4.8 shall not prevent other
          adjustments in the Exercise Price arising by virtue of such
          outstanding Options or Convertible Securities pursuant to the
          provisions of Sections 7.4.2, 7.4.4 and 7.4.5 hereof.

               7.4.9. WARRANT AGENT'S DISCLAIMER. The Warrant Agent shall have
          no duties or responsibilities under this Section 7.4, including, but
          not limited to, determining when an adjustment under this Section 7.4
          should be made, how such adjustment should be made or what the
          adjustment should be. The Warrant Agent makes no representation as to
          the validity or value of any securities or assets issued upon exercise
          of Warrants. The Warrant Agent shall not be responsible for the
          Company's failure to comply with this Section 7.4.

          7.5. ADJUSTMENTS FOR CONSOLIDATION, MERGER, SALE OF ASSETS,
     REORGANIZATION, ETC. In case the Company after the date hereof (a) shall
     consolidate with or merge into any other Person and shall not be the
     continuing or surviving corporation of such consolidation or merger, or (b)
     shall permit any other Person to consolidate with or merge into the Company
     and the Company shall be the continuing or surviving Person and the holders
     of a majority of the Company's capital stock before such consolidation or
     merger shall cease to hold a majority of the Company's capital stock after
     such consolidation or merger, or (c) shall effect a capital reorganization
     or reclassification of the Common Stock or Other Securities, then in the
     case of each such transaction proper provision shall be made so that, upon
     the basis and the terms and in the manner provided in this Agreement, the
     holders of the Warrants, upon the exercise thereof at any time after the
     consummation of such transaction, shall be entitled to receive (at the
     aggregate Exercise Price in effect at the time of such consummation for all
     Common Stock or Other Securities issuable upon such exercise immediately
     prior to such consummation), in lieu of the Common Stock or Other
     Securities issuable upon such exercise prior to such consummation, the
     greatest amount of securities, cash or other property to which such holder
     would actually have been entitled as a shareholder upon such consummation
     if such holder had exercised the rights represented by the Warrant
     Certificate held by it immediately prior thereto.

                                     - 16 -
<Page>

          7.6. NOTICE OF ADJUSTMENTS. Whenever the Exercise Price is adjusted,
     the Company will promptly deliver to the Warrant Agent and to each
     registered Warrantholder at the address provided to the Warrant Agent a
     certificate setting forth, in reasonable detail, the event that triggered
     the adjustment or issuance, the amount of the adjustment or issuance, the
     method by which such adjustment or issuance was calculated (including a
     description of the basis on which the Board made any determination
     hereunder), and the Exercise Price after giving effect to such adjustment.
     Unless and until the Warrant Agent receives such a certificate, it may
     assume without inquiry that the Exercise Price of any outstanding Warrants
     has not been adjusted.

          7.7. NO RIGHTS OR LIABILITIES AS STOCKHOLDER. Nothing contained in
     this Agreement or in any Warrant shall be construed as conferring upon any
     Warrantholder who has not exercised a Warrant any rights as a stockholder
     of the Company prior to exercise of any Warrant or as imposing any
     obligation on such Warrantholder to purchase any Securities or as imposing
     any liabilities on such holder as a stockholder of the Company, whether
     such obligation or liabilities are asserted by the Company or by creditors
     of the Company.

     Section 8. REGISTRATION RIGHTS. The Company will perform and comply, and
cause each of its Subsidiaries to perform and comply, with each of the following
provisions as are applicable to it. Each holder of Warrant Shares will perform
and comply with each of the following provisions as are applicable to such
holder.

          8.1. DEMAND REGISTRATION RIGHTS.

               8.1.1. GENERAL. One or more holders of Warrants or Warrant Shares
          who at such time hold greater than 20% of the Warrant Shares that have
          been or may be issued upon exercise, conversion or exchange of the
          Warrants ("INITIATING HOLDERS") may request, by written notice to the
          Company, that the Company effect the registration under the Securities
          Act for a Public Offering of all or a specified part of the
          Registrable Securities held by such Initiating Holders, without
          exercising, converting or exchanging the Warrants held by such
          Initiating Holders prior to making such request. Such notice shall
          specify the intended method or methods of distribution. Promptly after
          receipt of such notice from the Initiating Holders, the Company shall
          give notice of such requested registration to all other holders of
          Registrable Securities and Warrantholders in accordance with Section
          8.2. The Company will then use its reasonable best efforts to effect
          the registration under the Securities Act of the Registrable
          Securities which the Company has been requested to register by such
          Initiating Holders, together with all other Registrable Securities
          which the Company has been requested to register pursuant to Section
          8.2 or otherwise by notice delivered to the Company within 20 days
          after the Company has given the required notice of such requested
          registration (which request shall specify the intended method of
          disposition of such Registrable Securities), all to the extent
          requisite to permit the disposition (in accordance with the intended
          methods thereof as aforesaid) of the Registrable Securities which the
          Company has been so requested to register; PROVIDED, HOWEVER, that the
          Company shall not be obligated to take any action to effect any

                                     - 17 -
<Page>

          such registration pursuant to this Section 8.1.1 within 180 days
          immediately following the effective date of any registration statement
          pertaining to an underwritten public offering of securities of the
          Company for its own account (other than a Rule 145 Transaction, or a
          registration relating solely to employee benefit plans).

               8.1.2. FORM; LIMITATIONS. Except as otherwise provided above,
          each registration requested pursuant to Section 8.1.1 shall be
          effected by the filing of a registration statement on Form S-1 (or any
          other form which includes substantially the same information as would
          be required to be included in a registration statement on such form as
          currently constituted), unless the use of a different form has been
          agreed to in writing by holders of at least a majority of the
          Registrable Securities to be included in the proposed registration
          statement in question (the "MAJORITY PARTICIPATING HOLDERS") or the
          Company is then eligible to use Form S-3 for a Public Offering by the
          Majority Participating Holders of their Warrant Shares; PROVIDED,
          HOWEVER, that the Company shall not be required to effect any
          registration requested pursuant to Section 8.1.1 on any form other
          than Form S-3 (or any successor form) if the Company has previously
          effected three or more registrations of Registrable Securities under
          Section 8.1.1 on any form other than Form S-3 (or any successor form).
          No registration of Registrable Securities which shall not have become
          and remained effective in accordance with this Section 8.1 shall be
          included in the calculation of the number of registrations
          contemplated by this Section 8.1.2 (unless the Initiating Holders
          withdraw their request for such registration, other than (i) if such
          withdrawal is a result of information concerning the business or
          financial condition of the Company which is made known after the date
          on which such registration was requested or (ii) if the Initiating
          Holders pay all the expenses of such registration otherwise payable by
          the Company pursuant to Section 8.1.3). If at the time of any request
          to register Registrable Securities pursuant to this Section 8.1.1, the
          Company is engaged or has plans to engage in a registered public
          offering or is engaged in any other activity which, in the good faith
          determination of the Board, would be adversely affected by the
          requested registration, then the Company may at its option direct that
          such request be delayed for a period not in excess of 30 days from the
          date of such request, such right to delay a request to be exercised by
          the Company not more than once in any 12-month period. In the event
          that, in the judgment of the Company, it is advisable to suspend use
          of a prospectus included in a registration statement due to pending
          material developments or other events that have not yet been publicly
          disclosed and as to which the Company believes public disclosure would
          be detrimental to the Company, the Company shall notify all selling
          stockholders to such effect, and, upon receipt of such notice, each
          such selling stockholder shall immediately discontinue any sales of
          Registrable Securities pursuant to such registration statement until
          such selling stockholder has received copies of a supplemented or
          amended prospectus or until such selling stockholder is advised in
          writing by the Company that the then current prospectus may be used
          and has received copies of any additional or supplemental filings that
          are incorporated or deemed incorporated by reference in such
          prospectus. Notwithstanding anything to the contrary herein, the
          Company shall not exercise

                                     - 18 -
<Page>

          its rights under the foregoing sentence to suspend sales of
          Registrable Securities for a period in excess of 30 days consecutively
          or 60 days in any 365-day period.

               8.1.3. PAYMENT OF EXPENSES. The Company shall pay all reasonable
          expenses of holders of Warrant Shares incurred in connection with the
          first three registrations of Registrable Securities requested pursuant
          to this Section 8.1 (including the reasonable fees and expenses of a
          single legal counsel representing all selling stockholders), other
          than underwriting discounts and commissions, if any, and applicable
          transfer taxes, if any.

               8.1.4. ADDITIONAL PROCEDURES. In the case of a registration
          pursuant to this Section 8.1.2, whenever the Initiating Holders shall
          request that such registration shall be effected pursuant to an
          underwritten offering, the Company shall include such information in
          the written notices to holders of Registrable Securities referred to
          in Section 8.1.2. In such event, the right of any holder of
          Registrable Securities to have securities owned by such holder
          included in such registration pursuant to this Section 8.1.1 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 upon by the Majority
          Participating Holders and such holder). If requested by the
          underwriters of such registration, the Company, together with the
          holders of Registrable Securities proposing to distribute their
          securities through such underwriting, will enter into an underwriting
          agreement with such underwriters for such offering containing such
          representations and warranties by the Company and such holders and
          such other terms and provisions as are customarily contained in
          underwriting agreements with respect to secondary distributions,
          including, without limitation, customary indemnity and contribution
          provisions (subject, in each case, to the limitations on such
          liabilities set forth in this Agreement).

          8.2. PIGGYBACK REGISTRATION RIGHTS.

               8.2.1. GENERAL. Each time the Company proposes to register any
          shares of Common Stock under the Securities Act on a form which would
          permit registration of Registrable Securities for sale to the public,
          for its own account and/or for the account of any holders of
          Registrable Securities or Affiliate of a holder of Registrable
          Securities (pursuant to Section 8.1 or otherwise), for sale in a
          Public Offering, the Company will give notice to all holders of
          Registrable Securities of its intention to do so. Any such holder may,
          by written response delivered to the Company within 20 days after the
          effectiveness of such notice, request that all or a specified part of
          the Registrable Securities held by such holder be included in such
          registration. The Company thereupon will use its reasonable efforts to
          cause to be included in such registration under the Securities Act all
          shares of Common Stock which the Company has been so requested to
          register by such holders, to the extent required to permit the
          disposition (in accordance with the methods to be used by the Company
          or other holders of shares of Common Stock in such Public Offering) of
          the Registrable Securities to be so registered. No registration of
          Registrable Securities effected under this Section 8.2 shall

                                     - 19 -
<Page>

          relieve the Company of any of its obligations to effect registrations
          of Registrable Securities pursuant to Section 8.1. The Company may
          withdraw or suspend any registration covered by this Section 8.2 at
          any time (subject, in the case of any registration also covered by
          Section 8.1, to any limitations set forth therein).

               8.2.2. EXCLUDED TRANSACTIONS. The Company shall not be obligated
          to effect any registration of Registrable Securities under this
          Section 8.2 incidental to the registration of any of its securities in
          connection with:

                    (a) Any Public Offering relating to employee benefit plans
               or dividend reinvestment plans; or

                    (b) Any Public Offering relating to the acquisition or
               merger after the date hereof by the Company or any of its
               Subsidiaries of or with any other businesses.

               8.2.3. PAYMENT OF EXPENSES. The Company shall pay all reasonable
          fees and expenses of a single legal counsel representing any and all
          holders of Registrable Securities incurred in connection with the
          first three registrations of Registrable Securities requested pursuant
          to this Section 8.2.

               8.2.4. ADDITIONAL PROCEDURES. Holders of Warrant Shares
          participating in any Public Offering pursuant to this Section 8.2
          shall take all such actions and execute all such documents and
          instruments that are reasonably requested by the Company to effect the
          sale of their Warrant Shares in such Public Offering, including,
          without limitation, being parties to the underwriting agreement
          entered into by the Company and any other selling stockholders in
          connection therewith and being liable in respect of the
          representations and warranties by, and the other agreements (including
          without limitation customary selling stockholder representations,
          warranties, indemnifications and "lock-up" agreements) for the benefit
          of the underwriters; PROVIDED, HOWEVER, that (a) with -------- -------
          respect to individual representations, warranties, indemnities and
          agreements of selling holders of Warrant Shares in such Public
          Offering, the aggregate amount of such liability shall not exceed such
          holder's net proceeds from such offering and (b) to the extent selling
          holders of Warrant Shares give further representations, warranties and
          indemnities, then with respect to all other representations,
          warranties and indemnities of sellers of shares in such Public
          Offering, the aggregate amount of such liability shall not exceed the
          lesser of (i) such holder's pro rata portion of any such liability, in
          accordance with such holder's portion of the total number of Warrant
          Shares included in the offering or (ii) such holder's net proceeds
          from such offering.

          8.3. CERTAIN OTHER PROVISIONS.

               8.3.1. UNDERWRITER'S CUTBACK. In connection with any registration
          of Warrant Shares, the underwriter may determine that marketing
          factors (including, without limitation, an adverse effect on the per
          share offering price) require a

                                     - 20 -
<Page>

          limitation of the number of Warrant Shares to be underwritten.
          Notwithstanding any contrary provision of Section 8.1 or Section 8.2,
          and subject to the terms of this Section 8.3.1, the underwriter may
          limit the number of shares which would otherwise be included in such
          registration by excluding any or all Registrable Securities from such
          registration (it being understood that the number of shares which the
          Company seeks to have registered in such registration shall not be
          subject to exclusion, in whole or in part, under this Section 8.3.1).
          Upon receipt of notice from the underwriter of the need to reduce the
          number of shares to be included in the registration, the Company shall
          advise all holders of the Company's securities that would otherwise be
          registered and underwritten pursuant hereto, and the number of shares
          of such securities, including Registrable Securities, that may be
          included in the registration shall be allocated in the following
          manner, unless the underwriter shall determine that marketing factors
          require a different allocation: (i) shares, other than Registrable
          Securities, requested to be included in such registration by
          stockholders shall be excluded unless (x) the Company has, prior to
          the date hereof, or after the date hereof with the consent of the
          Majority Holders, granted registration rights which are to be treated
          on an equal basis with Registrable Securities for the purpose of the
          exercise of the underwriter cutback (with it being specifically agreed
          and acknowledged that the registration rights granted to Silicon
          Valley Bank pursuant to the Registration Rights Agreement, dated on or
          around December 30, 2002, between the Company and Silicon Valley Bank
          are to be treated on an equal basis with Registrable Securities for
          the purposes of this underwriting cutback), or (y) such shares are
          issued upon the exercise of warrants to purchase Common Stock that are
          issued in connection with a Permitted Exchange (as defined in the
          Exchange Agreement), with it being specifically acknowledged that the
          registration rights granted to the holders of any such shares of
          Common Stock are to be treated on an equal basis with Registrable
          Securities for purposes of this underwriting cutback; and (ii) if
          further limitation on the number of shares to be included in the
          offering is required, the number of Registrable Securities and other
          shares of Common Stock that may be included in such registration shall
          be allocated among holders thereof in proportion, as nearly as
          practicable, to the respective amounts of Common Stock which each
          stockholder requested be registered in such registration. No
          securities excluded from the underwriting by reason of the
          underwriter's marketing limitation shall be included in such
          registration. Upon delivery of a written request that Registrable
          Securities be included in an underwritten offering pursuant to Section
          8.1.1 or Section 8.2.1, the holder thereof may not thereafter elect to
          withdraw therefrom without the written consent the Company and the
          Majority Participating Holders.

               8.3.2. REGISTRATION PROCEDURES. If and in each case when the
          Company is required to use its reasonable best efforts to effect a
          registration of any Registrable Securities as provided in Section 8.1
          or Section 8.2, the Company shall take appropriate and customary
          actions in furtherance thereof, including, without limitation:

                                     - 21 -
<Page>

                    (a) promptly filing with the Commission a registration
               statement and using best efforts to cause such registration
               statement to become effective;

                    (b) preparing and filing with the Commission such amendments
               and supplements to such registration statements as may be
               required to comply with the Securities Act and to keep such
               registration statement effective for a period not to exceed 270
               days from the date of effectiveness or such earlier time as the
               Registrable Securities covered by such registration statement
               shall have been disposed of in accordance with the intended
               method of distribution therefor or the expiration of the time
               when a prospectus relating to such registration is required to be
               delivered under the Securities Act; PROVIDED, HOWEVER, that if
               the registration is effected by the filing of a registration
               statement on Form S-3, then the Company shall keep such
               registration statement effective for a period not to exceed 3
               years from the date of effectiveness or such earlier time as the
               Registrable Securities covered by such registration statement
               have been disposed of in accordance with the intended method of
               distribution therefore, the expiration of the time when a
               prospectus relating to such registration is required to be
               delivered under the Securities Act, or such registration
               statement no longer covers Registrable Securities;

                    (c) using its best efforts to register or qualify such
               Registrable Securities under the state securities or "blue sky"
               laws of such jurisdictions as the sellers shall reasonably
               request; provided, HOWEVER, that the Company shall not be
               obligated to file any general consent to service of process or to
               qualify as a foreign corporation in any jurisdiction in which it
               is not so qualified or to subject itself to taxation in respect
               of doing business in any jurisdiction in which it would not
               otherwise be so subject; and

                    (d) otherwise cooperating reasonably with, and taking such
               customary actions as may reasonably be requested by the holders
               of Registrable Securities in connection with, such registration.

               8.3.3. SELECTION OF UNDERWRITERS AND COUNSEL. The underwriters
          and legal counsel to be retained in connection with any Public
          Offering shall be selected by the Board or, in the case of an offering
          following a request therefor under Section 8.1.1, the Initiating
          Holders with the consent of the Company (which consent shall not be
          unreasonably withheld).

               8.3.4. LOCK-UP. Without the prior written consent of the
          underwriters managing any Public Offering, for a period beginning
          seven days immediately preceding and ending on the 90th day following
          the effective date of the registration statement used in connection
          with such offering, no holder of Warrant Shares (whether or not a
          selling stockholder pursuant to such registration statement)
          representing at least 1% of the outstanding Common Stock shall

                                     - 22 -
<Page>

          (a) offer, pledge, sell, contract to sell, sell any option or contract
          to purchase, purchase any option or contract to sell, grant any
          option, right or warrant to purchase, lend, or otherwise transfer,
          directly or indirectly, any shares of Common Stock or any securities
          convertible into or exercisable or exchangeable for such Common Stock
          or (b) enter into any swap or other arrangement that transfers to
          another, in whole or in part, any of the economic consequences of
          ownership of Common Stock, whether any such transaction described in
          clause (a) or (b) above is to be settled by delivery of such Common
          Stock or such other securities, in cash or otherwise; PROVIDED,
          HOWEVER, that the foregoing restrictions shall not apply to (i) the
          sale of Common Stock pursuant to any such registration statement filed
          in accordance with Section 8.1 or Section 8.2; (ii) transactions
          relating to shares of Common Stock or other securities acquired in
          open market transactions; or (iii) the exercise, conversion or
          exchange of Warrants or conversions of shares of Common Stock into
          other classes of Common Stock without change of holder.

               8.3.5. FUTURE REGISTRATION RIGHTS. If, after the date hereof, the
          Company enters into an agreement or other commitment with any other
          Person that has the effect of establishing registration rights with
          respect to the Company's capital stock the terms of which are more
          favorable, taken as a whole, to such Person than the registration
          rights established in favor of the holders of Registrable Securities
          and Warrantholders pursuant to Section 8.1 or Section 8.2, then the
          Company will promptly so notify the such holders in writing, and the
          Company shall, without the necessity of any action on the part of such
          holders, extend the benefits of such more favorable terms to such
          holders as if such terms were contained in this Agreement, or permit
          such holders to enter into such other agreement establishing such
          rights in lieu of this agreement.

          8.4. INDEMNIFICATION AND CONTRIBUTION.

               8.4.1. INDEMNITIES OF THE COMPANY. In the event of any
          registration of any Registrable Securities or other debt or equity
          securities of the Company or any of its Subsidiaries under the
          Securities Act pursuant to Section 8.1, Section 8.2 or otherwise, and
          in connection with any registration statement or any other disclosure
          document produced by or on behalf of the Company or any of its
          Subsidiaries including, without limitation, reports required and other
          documents filed under the Exchange Act, and other documents pursuant
          to which any debt or equity securities of the Company or any of its
          Subsidiaries are sold (whether or not for the account of the Company
          or its Subsidiaries), the Company will, and hereby does, and will
          cause each of its Subsidiaries, jointly and severally, to indemnify
          and hold harmless each seller of Registrable Securities, any Person
          who is or might be deemed to be a controlling Person of the Company or
          any of its Subsidiaries within the meaning of section 15 of the
          Securities Act or section 20 of the

                                     - 23 -
<Page>

          Exchange Act, their respective direct and indirect partners, advisory
          board members, directors, officers, trustees, members and
          stockholders, and each other Person, if any, who controls any such
          seller or any such controlling Person within the meaning of section 15
          of the Securities Act or section 20 of the Exchange Act (each such
          person being referred to herein as a "COVERED PERSON"), against any
          losses, claims, damages or liabilities (or actions or proceedings in
          respect thereof), joint or several, to which such Covered Person may
          be or become subject under the Securities Act, the Exchange Act, any
          other securities or other law of any jurisdiction, the common law or
          otherwise, insofar as such losses, claims, damages or liabilities (or
          actions or proceedings in respect thereof) arise out of or are based
          upon (i) any untrue statement or alleged untrue statement of any
          material fact contained or incorporated by reference in any
          registration statement under the Securities Act, any preliminary
          prospectus or final prospectus included therein, or any related
          summary prospectus, or any amendment or supplement thereto, or any
          document incorporated by reference therein, or any other such
          disclosure document (including without limitation reports and other
          documents filed under the Exchange Act and any document incorporated
          by reference therein) or other document or report, (ii) any 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
          or any of its subsidiaries of any federal, state, foreign or common
          law rule or regulation applicable to the Company or any of its
          Subsidiaries and relating to action or inaction in connection with any
          such registration, disclosure document or other document or report,
          and will reimburse such Covered Person for any legal or any other
          reasonable expenses incurred by it in connection with investigating or
          defending any such loss, claim, damage, liability, action or
          proceeding; PROVIDED, HOWEVER, that neither the Company nor any of its
          Subsidiaries shall be liable to any Covered Person in any such case to
          the extent that any such loss, claim, damage, liability, action or
          proceeding arises out of or is based upon an untrue statement or
          alleged untrue statement or omission or alleged omission made in such
          registration statement, preliminary prospectus, final prospectus,
          summary prospectus, amendment or supplement, incorporated document or
          other such disclosure document or other document or report, in
          reliance upon and in conformity with written information furnished to
          the Company or to any of its Subsidiaries through an instrument duly
          executed by such Covered Person specifically stating that it is for
          use in the preparation thereof. The indemnities of the Company and of
          its subsidiaries contained in this Section 8.4.1 shall remain in full
          force and effect regardless of any investigation made by or on behalf
          of such Covered Person and shall survive any transfer of securities.

               8.4.2. INDEMNITIES TO THE COMPANY. The Company and any of its
          Subsidiaries may require, as a condition to including any securities
          in any registration statement filed pursuant to this Agreement, that
          the Company and any of its Subsidiaries shall have received an
          undertaking satisfactory to it from the prospective seller of such
          securities, to indemnify and hold harmless the Company and any of its
          Subsidiaries, each director of the Company or any of its Subsidiaries,
          each officer of the Company or any of its Subsidiaries who shall sign
          such registration statement and each other Person (other than such
          seller), if any, who controls the Company and any of its Subsidiaries
          within the meaning of section 15 of the Securities Act or section 20
          of the Exchange Act and each other

                                     - 24 -
<Page>

          prospective seller of such securities with respect to any statement in
          or omission from such registration statement, any preliminary
          prospectus, final prospectus or summary prospectus included therein,
          or any amendment or supplement thereto, or any other disclosure
          document (including, without limitation, reports and other documents
          filed under the Exchange Act or any document incorporated therein) or
          other document or report, if such statement or omission was made in
          reliance upon and in conformity with written information furnished to
          the Company or any of its Subsidiaries through an instrument executed
          by such seller specifically stating that it is for use in the
          preparation thereof. Such indemnity shall remain in full force and
          effect regardless of any investigation made by or on behalf of the
          Company, any of its Subsidiaries or any such director, officer or
          controlling Person and shall survive any transfer of securities.

               8.4.3. CONTRIBUTION. If the indemnification provided for in
          Section 8.4.1 or Section 8.4.2 hereof is unavailable to a party that
          would have been entitled to indemnification pursuant to the foregoing
          provisions of this Section 8.4 (an "INDEMNITEE") in respect of any
          losses, claims, damages or liabilities (or actions or proceedings in
          respect thereof) referred to therein, then each party that would have
          been an indemnifying party thereunder shall, in lieu of indemnifying
          such Indemnitee, contribute to the amount paid or payable by such
          Indemnitee as a result of such losses, claims, damages or liabilities
          (or actions or proceedings in respect thereof) in such proportion as
          is appropriate to reflect the relative fault of such indemnifying
          party on the one hand and such Indemnitee on the other in connection
          with the statements or omissions which resulted in such losses,
          claims, damages or liabilities (or actions or proceedings in respect
          thereof). The relative fault shall be determined by reference to,
          among other things, whether the untrue or alleged untrue statement of
          a material fact or the omission or alleged omission to state a
          material fact relates to information supplied by such indemnifying
          party or such Indemnitee and the parties' relative intent, knowledge,
          access to information and opportunity to correct or prevent such
          statement or omission. The parties agree that it would not be just or
          equitable if contribution pursuant to this Section 8.4.3 were
          determined by pro rata allocation or by any other method of allocation
          which does not take account of the equitable considerations referred
          to in the preceding sentence. The amount paid or payable by a
          contributing party as a result of the losses, claims, damages or
          liabilities (or actions or proceedings in respect thereof) referred to
          above in this Section 8.4.3 shall include any legal or other expenses
          reasonably incurred by such Indemnitee in connection with
          investigating or defending any such action or claim. No Person guilty
          of fraudulent misrepresentation (within the meaning of section 11(f)
          of the Securities Act) shall be entitled to contribution from any
          Person who was not guilty of such fraudulent misrepresentation.

               8.4.4. LIMITATION ON LIABILITY OF HOLDERS OF REGISTRABLE
          SECURITIES. The liability of each holder of Registrable Securities in
          respect of any indemnification or contribution obligation of such
          holder arising under this Section 8.4 shall not in any event exceed an
          amount equal to the net proceeds to such holder (after deduction of
          all underwriters' discounts and commissions) from the disposition of

                                     - 25 -
<Page>

          the Registrable Securities disposed of by such holder pursuant to such
          registration.

          8.5. REPORTS UNDER EXCHANGE ACT. In order to provide to the holders of
     Warrant Shares the benefits of Rule 144 and any other rule or regulation of
     the Commission that may at any time permit any such holder to sell
     securities of the Company to the public without registration, and in order
     to make it possible for the holders of Warrant Shares to register the sale
     of the Registrable Securities pursuant to a registration on Form S-3, the
     Company agrees to:

                    (a) make and keep public information available, as those
               terms are understood and defined in Rule 144;

                    (b) take such action, including the registration of its
               Common Stock under section 12 of the Exchange Act, as is
               necessary to enable the holders of Warrant Shares to utilize Form
               S-3 for the sale of their Registrable Securities (ignoring, for
               this purpose, the provisions of Items I.A.5 and I.B.3 of the
               General Instructions thereto);

                    (c) file with the Commission in a timely manner all reports
               and other documents required of the Company under the Securities
               Act and the Exchange Act; and

                    (d) furnish to any holder of Warrant Shares, so long as the
               holder owns any Registrable Securities, forthwith upon request
               (i) a written statement by the Company that it has complied with
               the reporting requirements of Rule 144, the Securities Act and
               the Exchange Act, or that it qualifies as a registrant whose
               securities may be resold in a secondary offering pursuant to Form
               S-3; (ii) a copy of the most recent annual or quarterly report of
               the Company filed with the Commission and such other reports and
               documents so filed by the Company; and (iii) such other
               information as may be reasonably requested in availing any holder
               of Shares any rule or regulation of the Commission which permits
               the selling of any such securities without registration or
               pursuant to such form.

     Section 9. DEFINITIONS. For the purposes of this Agreement, the following
terms have the meanings below:

          "ADDITIONAL COMMON SHARES" shall mean, subject to Section 7.4.8, all
     shares of Common Stock (including treasury shares) issued or sold (or,
     pursuant to Section 7.4.4 or 7.4.5 hereof, deemed to be issued) by the
     Company after the date hereof, whether or not subsequently reacquired or
     retired by the Company, other than (i) shares of Common Stock issued or
     issuable upon conversion, exercise or exchange of the Warrants; and (ii)
     Excluded Issuances.

          "AFFILIATE" shall mean, with respect to the Company or any of its
     Subsidiaries (or any other specified Person), any other Person which,
     directly or indirectly controls or is controlled by or is under direct or
     indirect common control with the Company or such

                                     - 26 -
<Page>

     Subsidiary (or such specified Person), and, without limiting the generality
     of the foregoing, shall include (a) any other Person which beneficially
     owns or holds 10% of more of any class of voting securities of such Person
     or 10% or more of the equity interest in such Person, (b) any other Person
     of which such Person beneficially owns or holds 10% or more of any class of
     voting securities or in which such Person beneficially owns or holds 10% or
     more of the equity interest in such Person and (c) any director or
     executive officer of such Person. For the purposes of this definition, the
     term "control" (including, with correlative meanings, the terms "controlled
     by" and "under common control with"), as used with respect to any Person,
     means the possession, directly or indirectly, of the power to direct or
     cause the direction of the management and policies of such Person, whether
     through the ownership of voting securities or by contract or otherwise.

          "ANTIDILUTION PRICE" has the meaning set forth in Section 7.4.2.

          "BOARD" shall mean the Board of Directors of the Company.

          "BUSINESS DAY" shall mean any day, excluding Saturday, Sunday and any
     day which shall be in New York, New York or Boston, Massachusetts a legal
     holiday or a day on which banking institutions are authorized by law or
     other governmental actions to close.

          "CASH CLOSE OUT" has the meaning set forth in Section 7.1.4.

          "COMMISSION" shall mean the Securities and Exchange Commission.

          "COMMON STOCK" shall mean the Company's common stock, par value $0.001
     per share.

          "COMPANY" has the meaning set forth in the introductory paragraph
     hereof.

          "COVERED PERSON" shall have the meaning set forth in Section 8.4.1.

          "CONVERTIBLE SECURITIES" shall mean any evidences of indebtedness,
     shares of stock (other than shares of Common Stock) or other securities,
     including warrants, directly or indirectly convertible into or exchangeable
     for shares of Common Stock.

          "CURRENT MARKET PRICE" shall mean on any date specified herein, the
     average daily Market Price during the period of the most recent 10 days,
     ending two trading days immediately preceding such date, on which the
     national securities exchanges were open for trading, except that if no
     Common Stock is then listed or admitted to trading on any national
     securities exchange or quoted in the over-the-counter market, the Current
     Market Price shall be the Market Price on such date.

          "EXCHANGE ACT" shall mean the Securities Exchange Act of 1934, as in
     effect from time to time.

                                     - 27 -
<Page>

          "EXCLUDED ISSUANCE" shall mean the issuance of shares of Common Stock
     (or options exercisable therefor) to officers, directors, and employees of
     the Company, which shares are either (a) currently subject to the Company's
     stock option plan or (b) 2,250,000 shares that are not currently subject to
     the Company's stock option plan.

          "EXERCISE PRICE" shall have the meaning set forth in Section 7.4.1.

          "EXPIRATION DATE" shall mean 5:00 P.M. Boston time on January 15,
     2008.

          "FAIR MARKET VALUE" shall mean, as of any date, as to any share of
     Common Stock, the Board's good faith determination of the fair value of
     such shares as of the applicable reference date.

          "INDEMNITEE" shall have the meaning set forth in Section 8.4.3.

          "INITIAL EXERCISE PRICE" shall have the meaning set forth in the first
     paragraph of this Agreement.

          "INITIATING HOLDER" shall have the meaning set forth in Section 8.1.1.

          "MAJORITY HOLDERS" shall mean, as of any date, the holders of a
     majority of the Warrant Shares outstanding on such date.

          "MAJORITY PARTICIPATING HOLDERS" shall have the same meaning set forth
     in Section 8.1.2.

          "MAJORITY WARRANTHOLDERS" shall mean at any time holders of more than
     50% of the Warrants or, if the Warrants have been exercised, the Warrant
     Shares.

          "MARKET PRICE" shall mean on any date specified herein, the amount per
     share of Common Stock equal to (a) the last sale price of Common Stock,
     regular way, on such date or, if no such sale takes place on such date, the
     average of the closing bid and asked prices thereof on such date, in each
     case as officially reported on the principal national securities exchange
     on which Common Stock is then listed or admitted to trading, or (b) if
     Common Stock is not then listed or admitted to trading on any national
     securities exchange but is designated as a national market system security
     by the NASD, the last trading price of Common Stock on such date, or (c) if
     there shall have been no trading on such date or if Common Stock is not so
     designated, the average of the closing bid and asked prices of Common Stock
     on such date as shown by the NASD automated quotation system, or if
     applicable, the OTCBB, or (d) if the Common Stock is not then listed or
     admitted to trading on any national exchange or quoted in the
     over-the-counter market, the Market Price thereof determined by good faith
     mutual agreement of the Company and the Majority Warrantholders. If, in the
     case of subsection (d), the Company and the Majority Warrantholders are
     unable to agree on the value of such Common Stock within 10 business days,
     the Market Price shall be determined in accordance with the following
     appraisal process:

                                     - 28 -
<Page>

          Within the following five business days, each of the Company and the
     Majority Warrantholders shall select and retain a firm of recognized
     expertise in the valuation of business to perform a valuation of the Market
     Price. Such firms shall then value the shares of the Common Stock, on a
     going concern basis, without regard to any minority, marketability or other
     discount resulting from consideration of a minority interest, the Company's
     status as a closely held corporation or the existence of any put or call
     rights. The Company shall provide to both valuation firms any information
     reasonably requested by either such firm in connection with its valuation.
     Each such firm shall deliver its valuation report to the Company and the
     holder within 20 days after receiving all requested information from the
     Company. If the greater of the valuations of a share of the Common Stock is
     no more than 110% of the lesser of such valuations, the Market Price shall
     be deemed to be the average of the two valuations. If the greater of such
     valuations exceeds 110% of the lesser of such valuations, the two valuation
     firms shall select a third mutually acceptable valuation firm within five
     business days of such determination. Such third valuation firm shall be
     directed to provide, within 15 business days, its valuation report, and the
     valuation determined by the first two valuation firms that is closest to
     the valuation determined by the third valuation firm shall be the Market
     Price as of the reference date. The Company shall bear all costs and
     expenses of this appraisal process.

          "NOTE" shall have the meaning set forth in the Recitals hereof.

          "OPTIONS" shall mean options, warrants or other rights to subscribe
     for, purchase or otherwise acquire either Common Stock or Convertible
     Securities.

          "OTHER SECURITIES" shall mean any stock (other than Common Stock) and
     other securities of the Company or any other Person which the holders of
     the Warrants at any time shall be entitled to receive, or shall have
     received, upon the exercise of the Warrants, in lieu of or in addition to
     Common Stock, or which at any time shall be issuable or shall have been
     issued in exchange for or in replacement of Common Stock or Other
     Securities pursuant to Section 6 hereof or otherwise.

          "PERSON" shall mean an individual, a corporation, a partnership, a
     limited liability company, a trust, an unincorporated organization or a
     government organization or an agency or political subdivision thereof.

          "PUBLIC OFFERING" shall mean a public offering and sale of Common
     Stock for cash pursuant to an effective registration statement under the
     Securities Act.

          "REGISTRABLE SECURITIES" shall mean the Warrant Shares and all shares
     of Common Stock directly or indirectly issued or issuable with respect to
     the Warrant Shares by way of stock dividend or stock split or in connection
     with a combination of shares, recapitalization, merger, consolidation or
     other reorganization; PROVIDED, HOWEVER, that shares of Common Stock which
     are Registrable Shares shall cease to be Registrable Shares (i) upon any
     sale pursuant to a registration statement or Rule 144 under the Securities
     Act or (ii) at such time as they become eligible for sale pursuant to Rule
     144(k) under the Securities Act.

                                     - 29 -
<Page>

          "RULE 144" shall mean Rule 144 under the Securities Act (or any
     successor Rule).

          "RULE 145 TRANSACTION" shall mean a registration on Form S-4 pursuant
     to Rule 145 of the Securities Act (or any successor Form or provision, as
     applicable).

          "SECURITIES" shall mean any debt or equity securities of the Company,
     whether now or hereafter authorized, and any instrument convertible into or
     exchangeable for Securities or a Security. "Security" shall mean one of the
     Securities.

          "SECURITIES ACT" shall mean the Securities Act of 1933, as in effect
     from time to time.

          "STOCK" shall include any and all shares, interests or other
     equivalents (however designated) of, or participants in, the capital stock
     of a corporation of any class.

          "SUBSIDIARY" shall mean, for any Person, (i) a corporation a majority
     of whose voting stock is at the time, directly or indirectly, owned by such
     Person, by one or more Subsidiaries of such Person or by such Person and
     one or more Subsidiaries of such Person, (ii) a partnership in which such
     Person or a Subsidiary of such Person is, at the date of determination, a
     general or limited partner of such partnership, but only if such Person or
     its Subsidiary is entitled to receive more than 50% of the assets of such
     partnership upon its dissolution, (iii) a limited liability company, a
     majority of whose membership interests is, at the time, directly or
     indirectly owned by such Person or with respect to which such Person has a
     right, under any scenario, to receive 50% or more of the distributions of
     the assets of such limited liability company upon its dissolution, or (iv)
     any other Person (other than a corporation or partnership) in which such
     Person, a Subsidiary of such Person or such Person and one or more
     Subsidiaries of such Person, directly or indirectly, at the date of
     determination thereof, has (a) at least a majority ownership interest or
     (b) the power to elect or direct the election of a majority of the
     directors or other governing body of such Person.

          "WARRANTHOLDERS" shall mean the holders of the Warrants as of the date
     hereof, together with any permitted transferees of such holders which
     subsequently acquire Warrants.

          "WARRANT SHARES" shall mean the shares received or to be received upon
     exercise, conversion or exchange of the Warrants.

     Section 10. PAYMENT OF TAXES. The Company will pay all documentary stamp
taxes attributable to the initial issuance of Warrant Shares upon the exercise
of Warrants; provided, however, that the Company shall not be required to pay
any tax or governmental charge which may be payable in respect of any transfer
involved in the issue of any Warrant Certificates or any Warrant Share
Certificates in a name other than that of the registered holder of a Warrant
Share Certificate or a Warrant Certificate surrendered upon the exercise of a
Warrant, and the Company shall not be required to issue or deliver such Warrant
Certificates or Warrant Share Certificates unless or until the person or persons
requesting the issuance thereof shall have paid to the Company the amount of
such tax or charge or shall have established to the satisfaction of the Company
that such tax or charge has been paid. The Warrant Agent shall have no duty or

                                     - 30 -
<Page>

obligation to take any action under any Section of this Agreement which requires
the payment by a Warrantholder of applicable taxes and governmental charges
unless and until the Warrant Agent is satisfied that all such taxes and/or
charges have been paid.

     Section 11. MUTILATED OR MISSING WARRANT CERTIFICATES AND WARRANT SHARE
CERTIFICATES. In case any of the Warrant Certificates shall be mutilated, lost,
stolen or destroyed, the Company, at its expense, shall issue and the Warrant
Agent shall countersign, in exchange and substitution for and upon cancellation
of the mutilated Warrant Certificate, or in lieu of and substitution for the
Warrant Certificate lost, stolen or destroyed, a new Warrant Certificate of like
tenor and representing an equivalent number of Warrants, but only upon receipt
of evidence reasonably satisfactory to the Company and the Warrant Agent of such
loss, theft or destruction of such Warrant Certificate and indemnity, if
requested, satisfactory to the Company and the Warrant Agent.

     Section 12. FRACTIONAL INTERESTS.

     (a) The Company shall not be required to issue fractional Warrant Shares on
the exercise of Warrants or otherwise. If more than one Warrant shall be
presented for exercise in full at the same time by the same holder, the number
of full Warrant Shares which shall be issuable upon the exercise thereof shall
be computed on the basis of the aggregate number of Warrant Shares purchasable
on exercise of the Warrants so presented. If any fraction of a Warrant Share
would, except for the provisions of this Section 12, be issuable on the exercise
of any Warrants (or specified portion thereof), the Company shall pay an amount
in cash equal to the Current Market Price of such fractional Warrant Share as of
the day immediately preceding the date the Warrant is presented for exercise,
multiplied by such fraction.

     (b) Warrants may be issued in fractional interests. Holders of fractional
interests in Warrants will be entitled to purchase a number of Warrant Shares
equal to the product obtained by multiplying the number of Warrant Shares
issuable with respect to a full Warrant multiplied by the fractional interest
owned by such holder in the Warrant.

     (c) Whenever a payment for fractional Warrant Shares is to be made by the
Warrant Agent, the Company shall (i) promptly prepare and deliver to the Warrant
Agent a certificate setting forth in reasonable detail the facts related to such
payment and the prices and/or formulas utilized in calculating such payments,
and (ii) provide sufficient monies to the Warrant Agent in the form of fully
collected funds to make such payments. The Warrant Agent shall be fully
protected in relying upon such a certificate and shall have no duty with respect
to, and shall not be deemed to have knowledge of any payment for fractional
Warrant Shares under any Section of this Agreement relating to the payment of
fractional Warrant Shares unless and until the Warrant Agent shall have received
such a certificate and sufficient monies.

     Section 13. MERGER, CONSOLIDATION OR CHANGE OF NAME OF WARRANT AGENT. Any
person into which the Warrant Agent may be merged or with which it may be
consolidated, or any person resulting from any merger or consolidation to which
the Warrant Agent shall be a party, or any person succeeding to substantially
all of the business of the Warrant Agent (including the administration of this
Agreement), shall be the successor to the Warrant Agent hereunder without the
execution or filing of any paper or any further act on the part of any of the
parties hereto,

                                     - 31 -
<Page>

provided that such person would be eligible for appointment as a successor
warrant agent under the provisions of Section 15. In case at the time such
successor to the Warrant Agent shall succeed to the agency created by this
Agreement, and in case at that time any of the Warrant Certificates shall have
been countersigned but not delivered, any such successor to the Warrant Agent
may adopt the countersignature of the original Warrant Agent; and in case at
that time any of the Warrant Certificates shall not have been countersigned, any
successor to the Warrant Agent may countersign such Warrant Certificates either
in the name of the predecessor Warrant Agent or in the name of the successor to
the Warrant Agent; and in all such cases such Warrant Certificates shall have
the full force and effect provided in the Warrant Certificates and in this
Agreement.

     In case at any time the name of the Warrant Agent shall be changed and at
such time any of the Warrant Certificates shall have been countersigned but not
delivered, the Warrant Agent whose name has been changed may adopt the
countersignature under its prior name, and in case at that time any of the
Warrant Certificates shall not have been countersigned, the Warrant Agent may
countersign such Warrant Certificates either in its prior name or in its changed
name, and in all such cases such Warrant Certificates shall have the full force
and effect provided in the Warrant Certificates and in this Agreement.

     Section 14. WARRANT AGENT. The Warrant Agent undertakes the duties and
obligations imposed by this Agreement (and no implied duties or obligations
shall be read into this Agreement against the Warrant Agent) upon the following
terms and conditions, by all of which the Company and the Warrantholders, by
their acceptance thereof, shall be bound:

     (a) The statements contained herein and in the Warrant Certificates shall
be taken as statements of the Company and the Warrant Agent assumes no
responsibility for the correctness of any of the same except such as describe
the Warrant Agent or action taken or to be taken by it. The Warrant Agent
assumes no responsibility with respect to the distribution of the Warrant
Certificates and the Warrant Share Certificates except as herein otherwise
provided.

     (b) The Warrant Agent shall not be responsible for any failure of the
Company to comply with any of the covenants contained in this Agreement or in
the Warrant Certificates to be complied with by the Company.

     (c) The Warrant Agent may consult at any time with counsel of its own
selection (who may be counsel for the Company) and the Warrant Agent shall incur
no liability or responsibility to the Company or to any Warrantholder in respect
of any action taken, suffered or omitted to be taken by it hereunder in
accordance with the opinion or the advice of such counsel.

     (d) The Warrant Agent shall incur no liability or responsibility to the
Company or to any Warrantholder for any action taken in reliance on any Warrant
Certificate, certificate of shares, notice, resolution, waiver, consent, order,
certificate, or other paper, document or instrument (whether in its original or
facsimile form) believed by it to be genuine and to have been signed, sent or
presented by the proper party or parties.

     (e) The Company agrees (i) to pay to the Warrant Agent reasonable
compensation for all services rendered by the Warrant Agent (including fees and
expenses of its counsel) and to

                                     - 32 -
<Page>

reimburse the Warrant Agent for all expenses, taxes and governmental charges and
other charges and disbursements of any kind and nature incurred by the Warrant
Agent in the preparation, delivery, execution, administration and amendment of
this Agreement and the exercise and performance of its duties hereunder and (ii)
to indemnify the Warrant Agent (and any predecessor Warrant Agent) and save it
harmless against any and all claims (whether asserted by the Company, a holder
or any other person), damages, losses, fines, penalties, settlements, expenses
(including taxes other than taxes based on the income of the Warrant Agent),
liabilities, including judgments, costs and counsel fees and expenses, for any
action taken, suffered or omitted to be taken by the Warrant Agent in connection
with the execution of this Agreement and the acceptance and administration of
this Agreement, except as a result of its gross negligence or willful misconduct
(each as finally determined by a court of competent jurisdiction). The costs and
expenses incurred in enforcing this right of indemnification shall be paid by
the Company. The provisions of this Section 14 shall survive the expiration of
the Warrants, the termination of this Agreement and the resignation or removal
of the Warrant Agent.

     (f) The Warrant Agent shall be under no obligation to institute any action,
suit or legal proceeding or to take any other action likely to involve expense
unless the Company or one or more registered Warrantholders shall furnish the
Warrant Agent with reasonable security and indemnity satisfactory to it for any
costs and expenses which may be incurred, but this provision shall not limit the
power of the Warrant Agent to take such action as it may consider proper,
whether with or without any such security or indemnity. All rights of action
under this Agreement or under any of the Warrants may be enforced by the Warrant
Agent without the possession of any of the Warrant Certificates or Warrant Share
Certificates or the production thereof at any trial or other proceeding relative
thereto, and any such action, suit or proceeding instituted by the Warrant Agent
shall be brought in its name as Warrant Agent and any recovery of judgment shall
be for the ratable benefit of the registered holders of the Warrants, as their
respective rights or interests may appear.

     (g) The Warrant Agent, and any stockholder, affiliate, director, officer or
employee of it, may buy, sell or deal in any of the Warrants or other securities
of the Company or become pecuniarily interested in any transaction in which the
Company may be interested, or contract with or lend money to the Company or
otherwise act as fully and freely as though it were not Warrant Agent under this
Agreement. Nothing herein shall preclude the Warrant Agent from acting in any
other capacity for the Company or for any other legal entity.

     (h) The Warrant Agent shall act hereunder solely as agent for the Company,
and its duties shall be determined solely by the provisions hereof. The Warrant
Agent shall not be liable for any action taken, suffered or omitted to be taken
by it in connection with this Agreement except for its own gross negligence or
willful misconduct, each as finally determined by a court of competent
jurisdiction. Anything to the contrary notwithstanding, in no event shall the
Warrant Agent be liable for special, punitive, indirect, consequential or
incidental loss or damage of any kind whatsoever (including but not limited to
lost profits), even if the Warrant Agent has been advised of the likelihood of
such loss or damage.

     (i) The Warrant Agent shall not at any time be under any duty or
responsibility to any Warrantholder to make or cause to be made any adjustment
of the Exercise Price or number

                                     - 33 -
<Page>

of the Warrant Shares or other securities or property deliverable as provided in
this Agreement, or to determine whether any facts exist which may require any of
such adjustments, or with respect to the nature or extent of any such
adjustments, when made, or with respect to the method employed in making the
same. The Warrant Agent shall not be accountable with respect to the validity or
value or the kind or amount of any Warrant Shares or of any securities or
property which may at any time be issued or delivered upon the exercise of any
Warrant or with respect to whether any such Warrant Shares or other securities
will when issued be validly issued and fully paid and nonassessable, and makes
no representation with respect thereto.

     (j) Notwithstanding anything in this Agreement to the contrary, neither the
Company nor the Warrant Agent shall have any liability to any Warrantholder or
other person as a result of its inability to perform any of its obligations
under this Agreement by reason of any preliminary or permanent injunction or
other order, decree or ruling issued by a court of competent jurisdiction or by
a governmental, regulatory or administrative agency or commission, or any
statute, rule, regulation or executive order promulgated or enacted by any
governmental authority prohibiting or otherwise restraining performance of such
obligation; provided that the Company must use its reasonable best efforts to
have any such order, decree or ruling lifted or otherwise overturned as soon as
possible.

     (k) With respect to the exercise by a Warrantholder of any Warrants in
accordance with the terms of this Agreement and with respect to any other
actions or omissions that may arise as a result of or under this Agreement, to
the extent the Warrant Agent has any questions or uncertainties as to what
actions it should take with respect thereto, the Warrant Agent may seek written
direction from the Company as to what course of action the Warrant Agent should
take and the Warrant Agent shall be fully protected and incur no liability in
refraining from taking any action thereunder unless and until the Warrant Agent
has received such written direction from the Company. Any application by the
Warrant Agent for such written instructions from the Company may, at the option
of the Warrant Agent, set forth in writing any action proposed to be taken or
omitted by the Warrant Agent under this Agreement and the date on and/or after
which such action shall be taken or such omission shall be effective. The
Warrant Agent shall not be liable for any action taken by, or omission of, the
Warrant Agent in accordance with a proposal included in such application on or
after the date specified in such application (which date shall not be less than
three Business Days after the date any officer of the Company actually receives
such application, unless any such officer shall have consented in writing to any
earlier date) unless prior to taking any such action (or the effective date in
the case of an omission), the Warrant Agent shall have received written
instructions in response to such application specifying the action to be taken
or omitted.

     (l) No provision of this Agreement shall require the Warrant Agent to
expend or risk its own funds or otherwise incur any financial liability in the
performance of any of its duties hereunder or in the exercise of its rights if
there shall be reasonable grounds for believing that repayment of such funds or
adequate indemnification against such risk or liability is not reasonably
assured to it.

     (m) Whenever in the performance of its duties under this Agreement the
Warrant Agent shall deem it necessary or desirable that any fact or matter be
proved or established by the Company prior to taking, suffering or omitting to
take any action hereunder, such fact or matter

                                     - 34 -
<Page>

(unless other evidence in respect thereof be herein specifically prescribed) may
be deemed to be conclusively proved and established by a certificate signed by
any one of the President, a Vice President, the Treasurer or the Secretary of
the Company and delivered to the Warrant Agent; and such certificate shall be
full authorization and protection to the Warrant Agent for any action taken or
suffered by it under the provisions of this Agreement in reliance upon such
certificate.

     (n) The Warrant Agent is hereby authorized and directed to accept
instructions with respect to the performance of its duties hereunder from any
one of the President, a Vice President, the Secretary or the Treasurer of the
Company, and to apply to such officers for advice or instructions in connection
with its duties, and such instructions shall be full authorization and
protection to the Warrant Agent, and the Warrant Agent shall not be liable for
any action taken, suffered or omitted to be taken by it in accordance with
instructions of any such officer.

     (o) The Warrant Agent may execute and exercise any of the rights or powers
hereby vested in it or perform any duty hereunder either itself or by or through
its attorneys or agents, and the Warrant Agent shall not be answerable or
accountable for any act, default, neglect or misconduct of any such attorneys or
agents or for any loss to the Company resulting from any such act, default,
neglect or misconduct, absent gross negligence or willful misconduct (each as
finally determined by a court of competent jurisdiction) in the selection and
continued employment thereof.

     Section 15. CHANGE OF WARRANT AGENT. The Warrant Agent or any successor
Warrant Agent may resign and be discharged from its duties under this Agreement
upon 60 days' notice in writing mailed to the Company. Upon such resignation or
if the Warrant Agent shall become incapable of acting as Warrant Agent, the
Company shall appoint a successor to such Warrant Agent. If the Company shall
fail to make such appointment within a period of 60 days after it has been
notified in writing of such resignation or incapacity by the Warrant Agent or by
the registered holder of a Warrant Certificate or a Warrant Share Certificate,
then the registered holder of any Warrant Certificate or Warrant Share
Certificate may apply to any court of competent jurisdiction for the appointment
of a successor to the Warrant Agent. Pending appointment of a successor to such
Warrant Agent, either by the Company or by such a court, the duties of the
Warrant Agent shall be carried out by the Company. The Majority Warrantholders
shall be entitled at any time to remove the Warrant Agent and appoint a
successor to such Warrant Agent. Such successor to the Warrant Agent must be
approved by the Company, which shall not unreasonably withhold such approval.
After appointment the successor to the Warrant Agent shall be vested with the
same powers, rights, duties and responsibilities as if it had been originally
named as Warrant Agent without further act or deed; but the former Warrant Agent
upon payment of all fees and expenses due it and its agents and counsel shall
deliver and transfer to the successor to the Warrant Agent any property at the
time held by it hereunder and execute and deliver any further assurance,
conveyance, act or deed necessary for the purpose. Failure to give any notice
provided for in this Section 15, however, or any defect therein, shall not
affect the legality or validity of the appointment of a successor to the Warrant
Agent.

     Section 16. NOTICES TO COMPANY AND WARRANT AGENT. Any notice or demand
authorized by this Agreement to be given or made by the Warrant Agent or by the
registered holder of any Warrant Certificate to or on the Company shall be
sufficiently given or made when and if delivered by facsimile transmission
(provided confirmation of receipt is received immediately

                                     - 35 -
<Page>

thereafter) or when received, if deposited in the mail, first class or
registered, postage prepaid, addressed (until another address is filed in
writing by the Company with the Warrant Agent), as follows:

                                    iBasis, Inc.
                                    20 Second Avenue
                                    Burlington, MA  01803
                                    Attention:  Chief Financial Officer
                                    Facsimile No.: 781-505-7304

                                    with a copy to:

                                    Bingham, McCutchen LLP
                                    1900 University Avenue
                                    Palo Alto, CA  94303-2223
                                    Attn:   Johan V. Brigham
                                    Facsimile No.: 650-849-4800

     In case the Company shall fail to maintain such office or agency or shall
fail to give such notice of the location or of any change in the location
thereof, presentations may be made and notices and demands may be served at the
office of the Warrant Agent designated for such purpose.

     Any notice pursuant to this Agreement to be given by the Company or by the
registered holder(s) of any Warrant Certificate to the Warrant Agent shall be
sufficiently given when and if delivered by facsimile transmission (provided
confirmation of receipt is received immediately thereafter) or deposited in the
mail, first-class or registered, postage prepaid, addressed (until another
address is filed in writing by the Warrant Agent with the Company) to the
Warrant Agent as follows:

                                    U.S. Bank National Association

                                    2 Avenue de Lafayette - 6th Floor

                                    Boston, MA  02111
                                    Attention:  Corporate Trust Services
                                    Facsimile No.: 617-662-1458

                                    with copies to:

                                    Nixon Peabody LLP
                                    101 Federal Street
                                    Boston, MA  02110
                                    Attn: Robert J. Coughlin
                                    Facsimile No.: 617-345-1300

                                    and

                                     - 36 -
<Page>

                                    Ropes & Gray
                                    One International Place
                                    Boston, MA 02110
                                    Attn:  Thomas B. Draper
                                    Facsimile No.: 617-951-7050

     Section 17. SUPPLEMENTS AND AMENDMENTS. The Company and the Warrant Agent
may from time to time supplement or amend this Agreement or the Warrant
Certificates without the approval of any Warrantholders in order to cure any
ambiguity or to correct or supplement any provision contained herein or therein
which may be defective or inconsistent with any other provision herein, or to
make any other revisions in regard to matters or questions arising hereunder
which the Company and the Warrant Agent may deem necessary or desirable and
which shall not in any way adversely affect the interests of the Warrantholders.
Any supplement or amendment not covered by the preceding sentence shall require
the consent of the Majority Warrantholders, the Company and the Warrant Agent.
Prior to executing any supplement or amendment, the Warrant Agent shall be
entitled to rely on an officer's certificate of the Company to the effect that
such amendment or supplement complies with the terms of this Section 17.
Notwithstanding anything in this Agreement to the contrary, the prior written
consent of the Warrant Agent must be obtained in connection with any supplement
or amendment which alters the rights or duties of the Warrant Agent.

     Section 18. SUCCESSORS. All the covenants and provisions of this Agreement
by or for the benefit of the Company or the Warrant Agent shall bind and inure
to the benefit of their respective successors and assigns hereunder.

     Section 19. SURVIVAL OF REGISTRATION RIGHTS PROVISIONS, WARRANT AGENT
PROVISIONS. The provisions of Sections 8 and 14 shall survive the exercise or
expiration of the Warrants.

     Section 20. GOVERNING LAW; SUBMISSION TO JURISDICTION: WAIVER OF JURY
TRIAL. This Agreement and each Warrant Certificates issued hereunder shall be
deemed to be a contract made under the laws of The Commonwealth of Massachusetts
and for all purposes shall be governed by and construed in accordance with the
internal laws of said State, without regard to principles of conflicts of laws.
Each party hereto hereby submits to the nonexclusive jurisdiction of the United
States District Court for the District of Massachusetts and of any Massachusetts
state court sitting in Boston for purposes of all legal proceedings arising out
of or relating to this agreement or the transactions contemplated hereby. Each
party hereto irrevocably waives, to the fullest extent permitted by law, any
objection which it may now or hereafter have to the laying of the venue of any
such proceeding brought in such a court and any claim that any such proceeding
brought in such a court has been brought in an inconvenient forum.

     TO THE EXTENT NOT PROHIBITED BY APPLICABLE LAW WHICH CANNOT BE WAIVED, EACH
PARTY HERETO HEREBY WAIVES AND COVENANTS THAT IT WILL NOT ASSERT (WHETHER AS
PLAINTIFF, DEFENDANT OR OTHERWISE) ANY RIGHT TO TRIAL BY JURY IN ANY FORUM IN
RESPECT OF ANY ISSUE OR ACTION, CLAIM, CAUSE OF ACTION OR SUIT (IN CONTRACT,
TORT OR OTHERWISE), INQUIRY, PROCEEDING OR INVESTIGATION ARISING OUT OF OR BASED
UPON THIS AGREEMENT OR THE SUBJECT MATTER HEREOF OR IN ANY WAY CONNECTED WITH OR
RELATED OR INCIDENTAL TO THE TRANSACTIONS

                                     - 37 -
<Page>

CONTEMPLATED HEREBY, IN EACH CASE WHETHER NOW EXISTING OR HEREAFTER ARISING.
EACH PARTY HERETO ACKNOWLEDGES THAT IT HAS BEEN INFORMED BY THE OTHER PARTIES
HERETO THAT THIS SECTION 20 CONSTITUTES A MATERIAL INDUCEMENT UPON WHICH THEY
ARE RELYING AND WILL RELY IN ENTERING INTO THIS AGREEMENT. Any party hereto may
file an original counterpart or a copy of this Section 20 with any court as
written evidence of the consent of each party hereto to the waiver of its right
to trial by jury.

     Section 21. EXERCISE OF RIGHTS AND REMEDIES. No delay of or omission in the
exercise of any right, power or remedy accruing to any party as a result of any
breach or default by any other party under this Agreement shall impair any such
right, power or remedy, nor shall it be construed as a waiver of or acquiescence
in any such breach or default, or of any similar breach or default occurring
later; nor shall any such delay, omission or waiver of any single breach or
default be deemed a waiver of any other breach or default occurring before or
after that waiver.

     Section 22. BENEFITS OF THIS AGREEMENT. Nothing in this Agreement shall be
construed to give to any Person or corporation other than the Company, the
Warrant Agent and the Warrantholders (including any holder of a beneficial
interest in any Warrant) any legal or equitable right, remedy or claim under
this Agreement, and this Agreement shall be for the sole and exclusive benefit
of the Company, the Warrant Agent and the Warrantholders (including any holder
of a beneficial interest in any Warrant).

     Section 23. COUNTERPARTS. This Agreement may be executed in any number of
counterparts and each of such counterparts shall for all purposes be deemed to
be an original, and all such counterparts shall together constitute but one and
the same instrument.

                            [SIGNATURE PAGE FOLLOWS]

                                     - 38 -
<Page>

     IN WITNESS WHEREOF, the parties hereto have caused this Agreement to be
duly executed, as of the day and year first above written.

                                   iBASIS, INC.

                                   By /s/ Ofer Gneezy
                                     ----------------------------
                                   Name:  Ofer Gneezy
                                   Title: President and CEO


                                   U.S. BANK NATIONAL ASSOCIATION,
                                   as Warrant Agent

                                   By /s/ John A. Brennan
                                     ----------------------------
                                   Name:  John A. Brennan
                                   Title: Trust Officer

                                     - 39 -
<Page>

                                                             [Warrant Agreement]

                                                                       EXHIBIT A

                           FORM OF WARRANT CERTIFICATE

                                     - 40 -
<Page>

                                                             [Warrant Agreement]

                                                                       EXHIBIT B

                        FORM OF COMMON STOCK CERTIFICATE

                                   [Attached]

                                     - 41 -
<Page>

                                                             [Warrant Agreement]

                                                                       EXHIBIT B

                            FORM OF QIB CERTIFICATION