Document:

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                                                                     EXHIBIT 4.6

                             SUBORDINATION AGREEMENT

     This Subordination Agreement is made as of January 30, 2003, by and
between the undersigned "Creditors" signatory hereto and all subsequent holders
of the Notes (as defined herein) or beneficial interests therein (collectively,
the "Creditors") and SILICON VALLEY BANK, a California-chartered bank, with its
principal place of business at 3003 Tasman Drive, Santa Clara, California 95054
and with a loan production office located at 2221 Washington Street, Suite 200,
Newton, Massachusetts 02462, doing business under the name "Silicon Valley East"
("Bank"), and for purposes of Section 17 below, U.S. Bank National Association,
as Collateral Agent and as Fiscal Agent, respectively, under the Exchange
Agreement and the Fiscal Agency Agreement referred to below (collectively, in
such capacities, the "Agent").

                                    RECITALS

     A. IBASIS, INC., a Delaware corporation, IBASIS GLOBAL, INC., a Delaware
corporation and IBASIS SECURITIES CORPORATION, a Massachusetts corporation
(collectively, "Borrower") has requested and/or obtained certain loans or other
credit accommodations from Bank to Borrower which are or may be from time to
time secured by assets and property of Borrower.

     B. The Creditors have extended loans or other credit accommodations to
Borrower, and/or may extend loans or other credit accommodations to Borrower
from time to time or may acquire Notes from other Creditors.

     C. In order to induce Bank to extend credit to Borrower and, at any time or
from time to time, at Bank's option, to make such further loans, extensions of
credit, or other accommodations to or for the account of Borrower, or to
purchase or extend credit upon any instrument or writing in respect of which
Borrower may be liable in any capacity, or to grant such renewals or extension
of any such loan, extension of credit, purchase, or other accommodation as Bank
may deem advisable, the Creditors are willing to subordinate: (i) all of
Borrower's indebtedness and obligations to the Creditors pursuant to (a) those
notes issued in connection with the Securities Exchange Agreement (the "Exchange
Agreement") among the Borrower, the investors signatory thereto (the
"Investors") and U.S. Bank National Association as Collateral Agent and Fiscal
Agent for the Investors, dated as of January ___, 2003 (the "Symphony Notes")
and (b) each additional note issued pursuant to a "Permitted Exchange" (as such
term is defined in the Exchange Agreement) (the "Additional Notes" and, together
with the Symphony Notes, the "Notes") (all of Borrower's indebtedness and
obligations under the Notes being hereinafter collectively referred to as the
"Subordinated Debt") to all of Borrower's indebtedness and obligations to Bank;
and (ii) all of the Creditors' security interests, if any, to all of Bank's
security interests in the Borrower's property.

     NOW, THEREFORE, THE PARTIES AGREE AS FOLLOWS:

     1. The Creditors subordinate to Bank any security interest or lien that the
Creditors may have in any property of Borrower. Notwithstanding the respective
dates of attachment or perfection of the security interest of the Creditors and
the security interest of Bank, the security interest of Bank in the Collateral
(the "Collateral"), as defined in a certain Loan and Security Agreement (the
"Loan Agreement") among iBasis, Inc., iBasis Global, Inc. and Bank dated as of
December 30, 2002 and as also defined in a certain Security Agreement between
iBasis Securities Corporation and Bank dated December 30, 2002, as each may be
amended from time to time, shall at all times be senior to the security interest
of the Creditors.

     2. All Subordinated Debt is subordinated in right of payment to all
obligations of Borrower to Bank now existing or hereafter arising, together with
all costs of collecting such obligations (including attorneys' fees), including,
without limitation, all interest accruing after the commencement by or against
Borrower of any bankruptcy, reorganization or similar proceeding, and all
obligations under the Loan Agreement (the "Senior Debt").

     3. Except as otherwise expressly provided herein, the Creditors will not
demand or receive from Borrower (and Borrower will not pay to the Creditors) all
or any part of the Subordinated Debt, by way of payment, prepayment, setoff,
lawsuit or otherwise, nor will the Creditors exercise any remedy with respect to
the Collateral, nor will the Creditors accelerate the Subordinated Debt, or
commence, or cause to commence, prosecute or participate in any administrative,
legal or equitable action against Borrower, until such time as both (i) the
Senior Debt is fully paid in cash and (ii) Bank has no commitment or obligation
to lend any

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her funds to Borrower. Nothing in the foregoing paragraph shall prohibit the
Creditors from converting all or any part of the Subordinated Debt into equity
securities of Borrower.

     4. Subject to Section 5, Borrower shall be permitted to make, and the
Creditors shall be permitted to accept or receive the following permitted
payments ("Permitted Payments"): (i) scheduled payments of interest when due
pursuant to the terms of the Subordinated Debt, (ii) payment in full of
principal outstanding under the Subordinated Debt at the later of (x) the
maturity date of the Subordinated Debt or (y) January 15, 2005 and (iii) other
payments specifically consented to in writing by Bank prior to the making of
such payment. In accordance with Section 3 above, Borrower acknowledges that it
cannot voluntarily prepay the entire indebtedness or any portion thereof due the
Creditors nor make any payments other than Permitted Payments, without Bank's
prior written consent and the Creditors acknowledge that they will not accept
any payment, other than a Permitted Payment, without Bank's prior written
consent.

     5.

          (i) If, after an event of default under the Subordinated Debt, the
     Creditors desire to exercise remedies, the Creditors shall provide Bank
     with a written notice (the "Creditors' Notice") that there has occurred an
     event of default under the Subordinated Debt. Bank shall respond to such
     notice to the Fiscal Agent and to the Creditors at the addresses set forth
     in their notice, within fifteen (15) days after receipt of the Creditors'
     Notice and Bank shall elect at its sole option to: (1) deliver a Blockage
     Notice (as defined below) to the Creditors or (2) deliver a notice that the
     Creditors may exercise remedies provided that the Creditors shall remit the
     proceeds of all Collateral to Bank until the Senior Debt is paid in full.
     If the Bank shall fail to respond to the Creditors' Notice, in accordance
     with the preceding sentence, within fifteen (15) days after receipt of the
     Creditors' Notice, the Creditors may exercise their rights and remedies
     provided that the Creditors shall remit to Bank all payments, distributions
     and or other proceeds received by the Creditors from the Borrower or with
     respect to the Collateral until the Senior Debt is paid full.

          (ii) If, at any time, there is an Event of Default under the Senior
     Debt, Bank may deliver written notice to the Fiscal Agent and to the
     Creditors that there is an Event of Default under the Senior Debt (a
     "Blockage Notice") and the Creditors shall not be entitled to accept or
     receive any payments on the Subordinated Debt (including, without
     limitation, any Permitted Payments) until the earlier of: (1) the Senior
     Debt is paid in full and Bank's commitment to lend has been terminated, (2)
     Bank rescinds the Blockage Notice or the Event of Default has been cured or
     waived by Bank in writing or (3) the end of the Blockage Period. The
     "Blockage Period" shall commence at the time the Blockage Notice is
     delivered to the Creditors and expire on the earlier to occur of the
     following: (1) (x) 180 days following the delivery of the Blockage Notice
     for non-payment Events of Default under the Senior Debt or (y) indefinitely
     for all payment Events of Default under the Senior Debt; PROVIDED THAT if,
     with respect to a Blockage Period based on non-payment defaults under the
     Senior Debt, prior to the expiration of such 180-day period Bank has
     commenced a judicial proceeding or a non-judicial action to collect or
     enforce the Senior Debt or exercised rights with respect to the Collateral
     and Bank continues to diligently pursue same, or a case or proceeding by or
     against Borrower is commenced under the federal Bankruptcy Code or any
     other insolvency law, then such period shall be extended during the
     continuation of such proceedings and actions until the payment in cash or
     other property or securities in the full amount of the allowed claim of
     Bank under the Senior Debt; or (2) Bank's written consent to the
     termination of the Blockage Period. With respect to non-payment defaults
     under the Senior Debt, in no event shall the Blockage Period during any
     period of 365 consecutive days exceed 180 days in the aggregate, whether
     pursuant to one Blockage Notice or multiple Blockage Notices.

     6. The Creditors shall promptly deliver to Bank in the form received
(except for endorsement or assignment by the Creditors where required by Bank)
for application to the Senior Debt any payment, distribution, security or
proceeds received by the Creditors with respect to the Subordinated Debt other
than in accordance with this Agreement (other than equity securities or debt
subordinated to the Senior Debt on the same terms as the Subordinated Debt).

     7. In the event of Borrower's insolvency, reorganization or any case or
proceeding under any bankruptcy or insolvency law or laws relating to the relief
of debtors, these provisions shall remain in full force and effect, and Bank's
claims against Borrower and the estate of Borrower shall be paid in full before
any payment is made to the Creditors.

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     8. Until the Senior Debt is fully paid in cash, and Bank's obligation to
lend any funds to Borrower has been terminated, the Creditors hereby authorize
Bank, as Creditors' attorney-in-fact, to file in any bankruptcy, insolvency or
similar proceeding involving Borrower the appropriate claim or claims in respect
of the Subordinated Debt on behalf of the Creditors if the Creditors do not do
so prior to 15 days before the expiration of the time to file claims in such
proceeding and if Bank elects, in its sole discretion, to file such claim or
claims.

     9. The Creditors shall immediately affix a legend to each of the Notes and
all other instruments evidencing the Subordinated Debt stating that the Notes
and such other instruments are subject to the terms of this Agreement. By the
execution of this Agreement, the Creditors hereby authorize Bank to amend any
financing statements filed by the Creditors against Borrower as follows: "In
accordance with a certain Subordination Agreement by and among the Secured
Party, the Debtor and Silicon Valley Bank, the Secured Party has subordinated
any security interest or lien that Secured Party may have in any property of the
Debtor to the security interest of Silicon Valley Bank in all assets of the
Debtor, notwithstanding the respective dates of attachment or perfection of the
security interest of the Secured Party and Silicon Valley Bank."

     10. No amendment of the documents evidencing or relating to the
Subordinated Debt shall directly or indirectly modify the provisions of this
Agreement in any manner which might terminate or impair the subordination of the
Subordinated Debt or the subordination of the security interest or lien that the
Creditors may have in any property of Borrower. In addition, such instruments
shall not be, in any event, amended to (i) increase the rate of interest with
respect to the Subordinated Debt, or (ii) accelerate the payment of the
principal or interest or any other portion of the Subordinated Debt.

     11. If, at any time after payment in full of the Senior Debt any payments
of the Senior Debt must be disgorged by Bank for any reason (including, without
limitation, the bankruptcy of Borrower), this Agreement and the relative rights
and priorities set forth herein shall be reinstated as to all such disgorged
payments as though such payments had not been made and the Creditors shall
immediately pay over to Bank all payments received with respect to the
Subordinated Debt to the extent that such payments would have been prohibited
hereunder. At any time and from time to time, without notice to the Creditors,
Bank may take such actions with respect to the Senior Debt as Bank, in its sole
discretion, may deem appropriate, including, without limitation, terminating
advances to Borrower, increasing the principal amount, extending the time of
payment, increasing applicable interest rates, renewing, compromising or
otherwise amending the terms of any documents affecting the Senior Debt and any
collateral securing the Senior Debt, and enforcing or failing to enforce any
rights against Borrower or any other person. No such action or inaction shall
impair or otherwise affect Bank's rights hereunder.

     12. This Agreement shall bind any successors or assignees of the Creditors,
including any transferees of Notes or beneficial interests in Notes, and shall
benefit any successors or assigns of Bank. This Agreement shall remain effective
until terminated in writing by Bank. This Agreement is solely for the benefit of
the Creditors and Bank and not for the benefit of Borrower or any other party.
The Creditors further agree that if Borrower is in the process of refinancing a
portion of the Senior Debt with a new lender, and if Bank makes a request of the
Creditors, the Creditors shall agree to enter into a new subordination agreement
with the new lender on substantially the terms and conditions of this Agreement,
and such subordination agreement shall be deemed to be in full force and effect,
regardless of whether or not executed by such Creditors from and after the
earlier of (x) such request, or (y) the consummation of such refinancing.

     13. This Agreement may be executed in two or more counterparts, each of
which shall be deemed an original and all of which together shall constitute one
instrument.

     14. This Agreement shall be governed by and construed in accordance with
the laws of the Commonwealth of Massachusetts, without giving effect to
conflicts of laws principles. The Creditors and Bank submit to the non-exclusive
jurisdiction of the state and federal courts located in Boston, Massachusetts in
any action, suit, or proceeding of any kind, against it which arises out of or
by reason of this Agreement; provided, however, that if for any reason Bank
cannot avail itself of the Courts of The Commonwealth of Massachusetts, the
Creditors accept jurisdiction of the Courts and venue in Santa Clara County,
California. THE CREDITORS AND BANK WAIVE THEIR RESPECTIVE RIGHTS TO A JURY TRIAL
OF ANY CLAIM OR CAUSE OF ACTION BASED UPON OR ARISING OUT OF THIS AGREEMENT OR
ANY OF THE TRANSACTIONS CONTEMPLATED HEREIN.

     15. This Agreement represents the entire agreement with respect to the
subject matter hereof, and supersedes all prior negotiations, agreements and
commitments. The Creditors are not relying on any representations by Bank or
Borrower in entering

                                       -3-
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into this Agreement, and the Creditors have kept and will continue to keep
themselves fully apprised of the financial and other condition of Borrower.
Subject to the last sentence of paragraph 12 above, this Agreement may be
amended only by written instrument signed by the Creditors and Bank.

     16. In the event that Bank is holding original chattel paper, documents,
instruments, or investment property of Borrower, Bank hereby acknowledges that
it is holding such Collateral for the benefit of the Creditors as an additional
secured party, as well as holding such Collateral for its own account, subject
to the relative priorities set forth herein. The Creditors hereby acknowledge
and agree that Bank has no fiduciary duty, duty of safekeeping, duty as bailee
or any other duty to the Creditors with regard to such Collateral. Bank hereby
agrees to deliver such original Collateral to the Creditors upon payment in full
of all Senior Debt and termination of this Agreement.

     17. (i) The Collateral Agent and each Creditor hereby agrees that (a) any
and all rights and powers of the Collateral Agent under or pursuant to the
Securities Exchange Agreement dated as of January __, 2003 by and among the
Borrower, the Guarantors defined therein, the Creditors and the Collateral Agent
(as the same may be amended or modified from time to time, the "Exchange
Agreement") shall be subject to the terms of this Subordination Agreement, and
(b) the Collateral Agent shall not knowingly take, and the Creditors shall not
instruct or direct the Collateral Agent to take, any action that would be in
violation of the terms hereof.

     (ii) The Collateral Agent is entering into this Subordination Agreement
solely in its capacity as Collateral Agent under the Exchange Agreement, and not
otherwise. The Collateral Agent shall have no any liability or responsibility
for the actions or omissions of any Creditor, or for any Creditor's compliance
with (or failure to comply with) the terms of this Subordination Agreement. The
Collateral Agent shall not have individual liability to the Bank if it shall
mistakenly pay over or distribute to any Creditor (or the Borrower) any amounts
to which the Bank is entitled under this Subordination Agreement, so long as the
Collateral Agent is acting in good faith. Nothing in this Subordination
Agreement shall be construed to subordinate or apply to any payment of fees or
expenses to the Collateral Agent to which it is entitled.

     (iii) In entering into this Subordination Agreement, and in performing or
observing any of the terms of this Subordination Agreement, and otherwise in
respect of any matter arising under or in respect of this Subordination
Agreement, the Collateral Agent shall enjoy and shall be protected by each of
the rights, immunities, indemnities and other protections set forth in the
Exchange Agreement; and any obligations, duties or liabilities to which the
Collateral Agent may be or become subject under or in respect of this
Subordination Agreement shall be subject to and limited by the terms of the
Exchange Agreement (including, without limitation, the terms of Section 11
thereof). Subject to the other provisions of this Section 17, in no event shall
the Collateral Agent have any liability hereunder that it would not have, nor
shall the Collateral Agent be obligated to take any action hereunder that it
would not be required to take, under the terms of the Exchange Agreement. The
Collateral Agent has no responsibility for the terms of this Subordination
Agreement or its sufficiency for any purpose.

     (iv) The Parties agree that the Fiscal Agent shall be responsible hereunder
solely for receiving and transmitting notices pursuant to Section 5(i) and (ii),
and shall have no responsibility for the performance by the Borrower or the
Creditors of their respective obligations hereunder. The Fiscal Agent is acting
hereunder as Fiscal Agent pursuant to A Fiscal Agency Agreement dated as of
January __ , 2002, among the Borrower and the Fiscal Agent, (the "Fiscal Agency
Agreement"), and not in its individual capacity. The Fiscal Agent shall not
knowingly take, and neither the Borrower nor the Creditors shall instruct or
direct the Fiscal Agent to take, any action that would be in violation of the
terms hereof.

     (v) The Fiscal Agent is entering into this Subordination Agreement solely
in its capacity as Fiscal Agent under the Fiscal Agency Agreement, and not
otherwise. The Fiscal Agent shall have no any liability or responsibility for
the actions or omissions of any Creditor, or for any Creditor's compliance with
(or failure to comply with) the terms of this Subordination Agreement. The
Fiscal Agent shall not have individual liability to the Bank if it shall
mistakenly pay over or distribute to any Creditor (or the Borrower) any amounts
to which the Bank is entitled under this Subordination Agreement, so long as the
Fiscal Agent is acting in good faith. Nothing in this Subordination Agreement
shall be construed to subordinate or apply to any payment of fees or expenses to
the Fiscal Agent to which it is entitled.

                                       -4-
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     (vi) In entering into this Subordination Agreement, and in performing or
observing any of the terms of this Subordination Agreement, and otherwise in
respect of any matter arising under or in respect of this Subordination
Agreement, the Fiscal Agent shall enjoy and shall be protected by each of the
rights, immunities, indemnities and other protections set forth in the Fiscal
Agency Agreement; and any obligations, duties or liabilities to which the Fiscal
Agent may be or become subject under or in respect of this Subordination
Agreement shall be subject to and limited by the terms of the Fiscal Agency
Agreement. Subject to the other provisions of this Section 17, in no event shall
the Fiscal Agent have any liability hereunder that it would not have, nor shall
the Fiscal Agent be obligated to take any action hereunder that it would not be
required to take, under the terms of the Fiscal Agency Agreement. The Fiscal
Agent has no responsibility for the terms of this Subordination Agreement or its
sufficiency for any purpose.

          IN WITNESS WHEREOF, the undersigned have executed this Agreement as of
     the date first above written.

                                 "Bank"

                                 SILICON VALLEY BANK

                                 By: /s/ John Peck
                                    ---------------------------

                                 Title: Vice President
                                       ------------------------

     Agreed to solely for purposes of Section 17 above:

     U. S. BANK NATIONAL ASSOCIATION,
     as Collateral Agent and as Fiscal Agent

     By: /s/ John A. Brennan
        --------------------------

     Title: Trust Officer
           -----------------------

                                       -5-
<Page>

                                        RHAPSODY FUND, LP

                                        BY SYMPHONY ASSET MANAGEMENT LLC,
                                        AS GENERAL PARTNER

                                        By: /s/ Neil Rudolph
                                           -----------------------------
                                           Name: Neil Rudolph
                                           Title: Chief Operating Officer

                                        ARPEGGIO FUND

                                        BY SYMPHONY ASSET MANAGEMENT LLC,
                                        AS INVESTMENT ADVISOR

                                        By: /s/ Neil Rudolph
                                           -----------------------------
                                           Name: Neil Rudolph
                                           Title: Chief Operating Officer

                                        INTERNATIONAL MONETARY FUND
                                        -CONVERTIBLE ARBITRAGE ACCOUNT

                                        BY SYMPHONY ASSET MANAGEMENT LLC,
                                        AS INVESTMENT ADVISOR

                                        By: /s/ Neil Rudolph
                                           -----------------------------
                                           Name: Neil Rudolph
                                           Title: Chief Operating Officer

                                        CSV LIMITED

                                        BY SYMPHONY ASSET MANAGEMENT LLC,
                                        AS INVESTMENT ADVISOR

                                        By: /s/ Neil Rudolph
                                           -----------------------------
                                           Name: Neil Rudolph
                                           Title: Chief Operating Officer

<Page>

                                        CITISAM, LTD.

                                        BY SYMPHONY ASSET MANAGEMENT LLC,
                                        AS INVESTMENT ADVISOR

                                        By: /s/ Neil Rudolph
                                           -----------------------------
                                           Name: Neil Rudolph
                                           Title: Chief Operating Officer

                                        ANDANTE FUND, LP

                                        BY SYMPHONY ASSET MANAGEMENT LLC,
                                        AS GENERAL PARTNER

                                        By: /s/ Neil Rudolph
                                           -----------------------------
                                           Name: Neil Rudolph
                                           Title: Chief Operating Officer

                                        VIVACE FUND, LP

                                        BY SYMPHONY ASSET MANAGEMENT LLC,
                                        AS GENERAL PARTNER

                                        By: /s/ Neil Rudolph
                                           -----------------------------
                                           Name: Neil Rudolph
                                           Title: Chief Operating Officer

                                        ADAGIO FUND

                                        BY SYMPHONY ASSET MANAGEMENT LLC,
                                        AS INVESTMENT ADVISOR

                                        By: /s/ Neil Rudolph
                                           -----------------------------
                                           Name: Neil Rudolph
                                           Title: Chief Operating Officer

<Page>

     The undersigned approves of the terms of this Agreement.

     "Borrower"

     IBASIS, INC.

     By: /s/ Ofer Gneezy
        --------------------------

     Title: President and CEO
           -----------------------

     IBASIS GLOBAL, INC.

     By: /s/ Richard G. Tennant
        --------------------------

     Title: Treasurer and CEO
           -----------------------

     IBASIS SECURITIES CORPORATION.

     By: /s/ Gordon VanderBrug
        --------------------------

     Title: Executive Vice President
           -----------------------

                                       -7-<Page>

                                                                     EXHIBIT 4.7

================================================================================

                                  iBASIS, INC.
                                     Issuer

                                      AND

                         U.S. BANK NATIONAL ASSOCIATION
                                  Fiscal Agent

                            FISCAL AGENCY AGREEMENT

                          Dated as of January 30, 2003

================================================================================

<Page>

                               TABLE OF CONTENTS

<Table>
<Caption>
                                                                            PAGE
                                                                            ----
<S>         <C>                                                              <C>
SECTION 1.  DEFINITIONS.......................................................1
SECTION 2.  APPOINTMENT OF FISCAL AGENT AND PAYING AGENT......................3
SECTION 3.  AUTHORIZED AMOUNTS; LIMITATION OF PAYMENTS........................4
SECTION 4.  FORMS OF NOTES; TRANSFER AND EXCHANGE.............................4
SECTION 5.  NOTE AMOUNT.......................................................6
SECTION 6.  AUTHORIZED REPRESENTATIVES........................................6
SECTION 7.  PAYMENTS ON NOTES AND DISBURSEMENTS FROM THE NOTE
            ACCOUNT; RECORD DATES.............................................6
SECTION 8.  PAYMENTS ON THE NOTES; WITHHOLDING................................7
SECTION 9.  [RESERVED] .......................................................7
SECTION 10. NOTE REGISTER; REGISTRATION, TRANSFER, EXCHANGE;
            PERSONS DEEMED OWNERS ............................................7
SECTION 11. MUTILATED, DESTROYED, LOST, OR STOLEN NOTES......................10
SECTION 12. CANCELLATION.....................................................11
SECTION 13. APPLICATION OF FUNDS; RETURN OF UNCLAIMED FUNDS..................11
SECTION 14. FISCAL AGENT'S STANDARD OF CASE; LIABILITY.......................12
SECTION 15. ISSUANCE OF NOTES ON CLOSING DATE................................13
SECTION 16. COMPENSATION AND INDEMNIFICATION.................................13
SECTION 17. SUPPLEMENTAL AGREEMENTS..........................................14
SECTION 18. LIMITATION ON SUITS..............................................16
SECTION 19. UNDERTAKING FOR COSTS............................................16
SECTION 20. [RESERVED] ......................................................16
SECTION 21. NOTICES..........................................................16
SECTION 22. RESIGNATION OR REMOVAL OF FISCAL AGENT AND
            APPOINTMENT OF SUCCESSOR FISCAL AGENT; MERGER,
            CONVERSION AND CONSOLIDATION.....................................17
SECTION 23. BENEFIT OF AGREEMENT.............................................18
SECTION 24. [RESERVED] ......................................................18
SECTION 25. NOTES HELD BY THE FISCAL AGENT; OTHER BUSINESS
            RELATIONS .......................................................18
SECTION 26. AMENDMENT........................................................19
SECTION 27. GOVERNING LAW....................................................19
SECTION 28. COUNTERPARTS.....................................................19
</Table>

<Page>

                               TABLE OF CONTENTS
                                  (CONTINUED)

<Table>
<Caption>
                                                                            PAGE
                                                                            ----
<S>         <C>                                                             <C>
SECTION 29. EXHIBITS ........................................................19
SECTION 30. [RESERVED] ......................................................19
SECTION 31. PRESCRIPTION.....................................................19
SECTION 32. IDENTIFICATION OF NOTEHOLDERS ...................................19
SECTION 33. SURVIVAL OF PROVISIONS...........................................19
SECTION 34. SUCCESSORS AND ASSIGNS...........................................20

                                    EXHIBITS

Exhibit A - Form of Note....................................................A-1
Exhibit B Form of Investor Representation Letter ...........................B-2
</Table>

                                       ii
<Page>

                             FISCAL AGENCY AGREEMENT

     FISCAL AGENCY AGREEMENT, dated as of January 30, 2003 (this "Agreement"),
between iBASIS, INC., a Delaware corporation (together with its permitted
successors and assigns, the "Company"), iBASIS GLOBAL, INC., a Delaware
corporation (together with its permitted successors and assigns, "iBasis
Global", and collectively with the Company, the "Issuer") and U.S. BANK NATIONAL
ASSOCIATION, as the fiscal agent, paying agent, note registrar and
authenticating agent hereunder (in such capacity, together with its permitted
successors and assigns, the "Fiscal Agent").

                              PRELIMINARY STATEMENT

     WHEREAS, pursuant to a certain Securities Exchange Agreement, as defined
below, the Symphony Funds (as defined in the Securities Exchange Agreement) are
exchanging (i) an aggregate principal amount of $30,200,000 in aggregate
principal amount of the Company's 5 3/4% Convertible Subordinated Notes due 2005
for (ii) $15,100,000 in aggregate principal amount of the Issuer's 11.5% Senior
Secured Notes due 2005 to be issued hereunder and warrants exercisable for an
aggregate of 3,071,184 shares of Common Stock, $0.001 par value, of the Company,
to be issued pursuant to a certain Warrant Agreement (as that term is defined in
the Securities Exchange Agreement); and

     WHEREAS, the Issuer wishes to appoint the Fiscal Agent to act as paying
agent, registrar and transfer agent in respect of the Issuer's 11.5% Senior
Secured Notes due 2005 Notes to be issuer hereunder, and otherwise to provide
the services set forth herein, and the Fiscal Agent is willing to accept such
appointment and perform such duties as provided in and subject to the terms of
this Agreement;

     NOW, THEREFORE, in consideration of the mutual covenants herein contained,
the parties hereto agree as follows:

     Section 1. DEFINITIONS.

     Except as otherwise specified herein or as the context may otherwise
require, the following terms have the respective meanings set forth below for
all purposes of this Agreement, and the definitions of such terms are equally
applicable both to the singular and plural forms of such terms and to the
masculine, feminine and neuter genders of such terms.

     "AUTHENTICATING AGENT" shall mean any Person authorized by the Issuer or
the Fiscal Agent pursuant to Section 4 to authenticate any Notes.

     "AUTHORIZED OFFICER" shall mean, with respect to any Person, any chairman,
deputy chairman, president, vice president, managing director, director,
secretary, treasurer or other officer thereof or any chairman, deputy chairman,
president, vice president, secretary, treasurer or other officer of any duly
appointed agent thereof who is authorized to act for such Person in matters
relating to, and binding upon, such Person.

     "AUTHORIZED REPRESENTATIVE" shall mean any member, officer, director,
employee, agent or attorney-in-fact of the Issuer authorized to execute Notes on
behalf of the Issuer by manual or

<Page>

facsimile signature and to give instructions and notices on behalf of the Issuer
pursuant to Section 6 hereof.

     "BUSINESS DAY" shall mean a day that satisfies the following conditions:
(1) it is a day on which commercial banks settle payments in New York, New York
and (2) it is a day on which commercial banks are open for business in the city
in which the Corporate Trust Office is located and in the city in which the
Corporate Trust Home Office is located.

     "CLOSING DATE" shall mean January 30, 2003.

     "CODE" shall mean the United States Internal Revenue Code of 1986, as
amended.

     "COLLATERAL AGENT": shall mean the U.S. Bank National Association acting in
its capacity as Collateral Agent under the Securities Exchange Agreement, or any
successor serving in such capacity under the Securities Exchange Agreement.

     "CORPORATE TRUST OFFICE" shall mean the corporate trust office of the
Fiscal Agent designated by the Fiscal Agent for the administration of this
Agreement, which is currently located at 2 Avenue de Lafayette, Boston,
Massachusetts 02111, Attention: Corporate Trust Services, or at such other
address as the Fiscal Agent may designate from time to time by notice to the
Noteholders and the Issuer.

     "CORPORATE TRUST HOME OFFICE" shall mean the principal corporate trust
office of the Fiscal Agent, which is currently located at 180 E. Fifth Street,
St, Paul Minnesota 55101, Attention: Corporate Trust Services, or at such other
address as the Fiscal Agent may designate from time to time by notice to the
Noteholders and the Issuer as its principal corporate trust office.

     "DISQUALIFIED TRANSFEREE" shall have the meaning set forth in Section
10(h).

     "DTC" shall mean The Depository Trust Company.

     "ERISA" shall mean the United States Employee Retirement Income Security
Act of 1974, as amended from time to time.

     "EXCHANGE ACT": The Securities Exchange Act of 1934, as amended.

     "FISCAL AGENT" shall mean U.S. Bank National Association, as the Fiscal
Agent hereunder, until a successor Person shall have become the Fiscal Agent
pursuant to the provisions hereof, and thereafter the term Fiscal Agent shall
mean such successor Person.

     "HOLDER" or "NOTEHOLDER" shall mean the registered holder of any Note as
set forth in the Note Register maintained by the Note Registrar. Notwithstanding
any notice to the contrary, the Fiscal Agent shall have no obligation to
recognize or deal with any Person claiming an interest in the Notes other than
such registered holders.

     "INVESTMENT COMPANY ACT" shall mean the United States Investment Company
Act of 1940, as amended.

                                        2             FISCAL AGENCY AGREEMENT
<Page>

     "INVESTOR REPRESENTATION LETTER" shall mean a letter substantially in the
form of Exhibit B hereto, duly completed as appropriate.

     "ISSUER ORDER" shall mean a written order dated and signed in the name of
the Issuer by an Authorized Representative of the Issuer.

     "NOTE ACCOUNT" shall mean the account established by the Fiscal Agent
pursuant to Section 5(b) hereof.

     "NOTE REGISTER" shall have the meaning set forth in Section 10(a) hereof.

     "NOTE REGISTRAR" shall have the meaning set forth in Section 10(a) hereof.

     "NOTEHOLDER" see "Holder."

     "NOTES" shall mean the Issuer's 11.5% Senior Secured Notes due 2005, duly
issued by the Issuer and authenticated and delivered by the Fiscal Agent under
this Agreement, which Notes shall be substantially in the form attached hereto
as Exhibit A.

     "OFFICER'S CERTIFICATE" shall mean, for any Person, a certificate signed on
behalf of such Person by an Authorized Officer of such Person.

     "OPINION OF COUNSEL" shall mean a written opinion, addressed to the Fiscal
Agent and inform and substance reasonably satisfactory to the Fiscal Agent, of
an attorney at law admitted to practice before the highest court of any state of
the United States or the District of Columbia or, with respect to matters
relating to the laws of New York or Delaware, which attorney or attorneys may,
except as otherwise expressly provided in this Agreement, be counsel for the
Issuer or the Fiscal Agent and who shall be reasonably satisfactory to the
Fiscal Agent.

     "PAYMENT DATE" shall mean each January 15 and July 15, commencing July 15,
2003.

     "PERSON" shall mean an individual, corporation (including a business
trust), partnership, limited liability company, limited liability partnership,
joint venture, association, joint stock company, trust (including any
beneficiary thereof), unincorporated association or government or any agency or
political subdivision thereof.

     "QUALIFIED INSTITUTIONAL BUYER" shall have the meaning set forth in Section
4(c) hereof.

     "QUALIFIED PURCHASER" shall have the meaning set forth in Section 4(c)
hereof.

     "RECORD DATE" shall mean, with respect to a Payment Date, the fifteenth
(15th) day (whether or not a Business Day) prior to such Payment Date.

     "REGISTERED" shall mean, with respect to any debt obligation, a debt
obligation (a) that is (in the case of a U.S. issuer) issued after July 18, 1984
and (b) that is in registered form for purposes of the Code.

     "RELEVANT DATE" shall have the meaning set forth in Section 31 hereof.

                                        3            FISCAL AGENCY AGREEMENT
<Page>

     "RESPONSIBLE OFFICER" shall mean, with respect to the Fiscal Agent, any
officer of the Corporate Trust Office of the Fiscal Agent, including any Vice
President, Managing Director, Director, Assistant Vice President, Secretary,
Assistant Secretary, Assistant Treasurer or any other officer of the Fiscal
Agent customarily performing functions similar to those performed by the
above-designated officers and with direct responsibility for the administration
of this Agreement and also, with respect to a particular matter, any other
officer to whom such matter is referred because of such officer's knowledge of
and familiarity with the particular subject.

     "RULE 144A" shall mean Rule 144A under the Securities Act.

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

     "SECURITIES EXCHANGE AGREEMENT" shall mean that certain Securities Exchange
Agreement dated as of January 30, 2003 among the Company, iBasis Global, iBasis
Securities Corporation, the Symphony Funds identified therein and the Collateral
Agent.

     "STATED MATURITY" shall mean January 15, 2005.

     Section 2. APPOINTMENT OF FISCAL AGENT AND PAYING AGENT.

          (a)  The Issuer hereby appoints the Fiscal Agent to act as fiscal
agent and as paying agent in respect of the Notes upon the terms and subject to
the conditions set forth herein and in the Notes. The Issuer may at any time and
from time to time vary or terminate the appointment of a paying agent for the
Notes or appoint any additional paying agents for the Notes. The Issuer shall
give prompt written notice to the Fiscal Agent of the appointment or termination
of any such paying agent and of the location and any change in the location of
any such office or agency. The Fiscal Agent shall provide notice to the Holders
of any such change or variation of which a Responsible Officer of the Fiscal
Agent receives actual notices.

          (b)  The Issuer hereby further appoints the Fiscal Agent as registrar
and transfer agent in respect of the Notes upon the terms and subject to the
conditions set forth herein and in the Notes. The Issuer may at any time and
from time to time vary or terminate the appointment of a transfer agent for the
Notes or appoint any additional transfer agents for the Notes. The Issuer shall
give prompt written notice to the Fiscal Agent of the appointment or termination
of any such transfer agent and of the location and any change in the location of
any such office or agency. The Fiscal Agent shall provide notice to the Holders
of any such change or variation of which a Responsible Officer of the Fiscal
Agent receives actual notices.

          (c)  The Fiscal Agent hereby accepts its appointment hereunder and
agrees to perform its duties hereunder in accordance with the terms hereof.

     Section 3. AUTHORIZED AMOUNTS; LIMITATION OF PAYMENTS.

          (a)  The aggregate principal amount of the Notes that may be
authenticated and delivered pursuant to this Agreement shall not exceed U.S.
$15,100,000, excluding Notes authenticated and delivered upon registration of
transfer of, or in exchange for, or in lieu of, other Notes pursuant to Sections
10, 11 or 12 of this Agreement.

                                        4            FISCAL AGENCY AGREEMENT
<Page>

          (b)  No later than the Business Day immediately preceding each Payment
Date, the Issuer shall deposit with the Fiscal Agent by wire transfer of
immediately available funds, the aggregate amount due and payable under the
Notes on such Payment Date, for deposit to the Note Account. Upon receipt
thereof, the Fiscal Agent shall deposit such amount to the Note Account, to be
applied in accordance with the terms of this Agreement.

          (c)  As a condition to the payment of principal of and interest on any
Note without U.S. federal back-up withholding, the Issuer shall require the
delivery by each Holder of a properly completed and signed Internal Revenue
Service Form W-9 (or applicable successor form).

     Section 4. FORMS OF NOTES; TRANSFER AND EXCHANGE.

          (a)  The Notes and the Fiscal Agent's certificate of authentication
thereon shall be in substantially the form attached hereto as EXHIBIT A, with
such appropriate insertions, omissions, substitutions and other variations as
the Issuer may direct (with the Fiscal Agent's consent, in the case of the
Certificate of Authentication), and may have such letters, numbers or other
marks of identification and such legends or endorsements placed thereon, as may,
consistently herewith, be determined to be appropriate by the Authorized
Representative of the Issuer executing such Notes, as evidenced by such Person's
execution of such Notes, or as may be required to comply with any law or with
any rule or regulation made pursuant thereto or with any rule or regulation of
any securities exchange on which the Notes may be listed, or to conform to
usage. Any portion of the text of any Note may be set forth on the reverse
thereof, with the appropriate reference thereto on the face of the Note.

          (b)  The Notes may be typed, printed, lithographed or engraved or
produced by any combination of these methods (with or without steel engraved
borders) or may be produced in any other manner, all as determined by the
Authorized Officers of the Issuer executing such Notes, as evidenced by their
execution thereof.

          (c)  On the Closing Date, the Notes shall be issued as provided in
Section 15 in the form of one or more notes in definitive, fully registered form
and substantially in the form attached hereto as EXHIBIT A.

          (d)  The Notes are being offered and sold in reliance on the exemption
from registration under Rule 144A to persons that are "qualified institutional
buyers" as defined in Rule 144A under the Securities Act (a "QUALIFIED
INSTITUTIONAL BUYER") (except for any sale directly from the Issuer) and a
"qualified purchasers" as defined under Section 2(a)(51) of the Investment
Company Act (a "QUALIFIED PURCHASER"). Upon the transfer or exchange of any
Note, such Notes shall be issued in the form of one or more certificated notes
in definitive, fully registered form with the legend set forth in EXHIBIT A
added to the form of such Notes, except as otherwise authorized by the Issuer at
the time of issuance. The Notes shall be executed on behalf of the Issuer by one
of its Authorized Representatives. The signature of such Authorized
Representative on the Notes may be manual or facsimile. Notes bearing the manual
or facsimile signature of an individual who was, at the time of such signature,
an Authorized Representative of the Issuer shall bind the Issuer,
notwithstanding the fact that such individual has ceased to hold such office
prior to the authentication and delivery of such Notes or did not hold such
office

                                        5            FISCAL AGENCY AGREEMENT
<Page>

at the date of issuance of such Notes. The Notes shall be registered in the name
of the Holder or a nominee thereof and shall be issued in minimum denominations
of U.S.$500,000 and integral multiples of U.S.$1,000 in excess thereof.

          (e)  The Notes shall be payable solely from amounts deposited with the
Fiscal Agent by the Issuer for such purpose pursuant to the terms hereof.

          (f)  Each Note authenticated and delivered by the Fiscal Agent
pursuant to this Agreement on the Closing Date shall be dated as of the Closing
Date. All other Notes that are authenticated hereunder shall be dated the date
of their authentication.

     No Note shall be entitled to any benefit under this Agreement or be valid
or obligatory for any purpose, unless there appears on such Note a certificate
of authentication, substantially in the form provided for herein, executed by
the Fiscal Agent (or an Authenticating Agent on its behalf) by the manual
signature of one of its Authorized Officers, and such certificate upon any Note
shall be conclusive evidence, and the only evidence, that such Note has been
duly authenticated and delivered hereunder. Such certificate by the Fiscal Agent
upon any Note executed by the Issuer shall be conclusive evidence that the Note
so authenticated has been duly authenticated and delivered hereunder and that
the Holder thereof is entitled to the benefits of this Agreement. Upon the
written request and at the expense of the Issuer, the Fiscal Agent shall and, at
the election of the Fiscal Agent, the Fiscal Agent may, appoint one or more
Authenticating Agents with power to act on its behalf and subject to its
direction in the authentication of Notes in connection with transfers and
exchanges pursuant to the terms of the Notes and this Agreement, as fully to all
intents and purposes as though each such Authenticating Agent had been expressly
authorized thereunder and hereunder to authenticate the Notes; PROVIDED,
HOWEVER, that any such appointment shall be upon terms and conditions reasonably
acceptable to the Fiscal Agent (with respect to which the Fiscal Agent may
require, among other things, appropriate indemnification for any damages, losses
or reasonable costs arising from acts or omissions of such Authenticating
Agent). For all purposes of this Agreement, the authentication of Notes by an
Authenticating Agent shall be deemed to be the authentication of Notes "by the
Fiscal Agent." Any corporation into which any Authenticating Agent may be merged
or converted or with which it may be consolidated, or any corporation resulting
from any merger, consolidation or conversion to which any Authenticating Agent
shall be a party, or any corporation succeeding to the corporate trust business
of any Authenticating Agent, shall be the successor of such Authenticating Agent
hereunder, without the execution or filing of any other document or any further
act on the part of the parties hereto or such Authenticating Agent or such
successor corporation. Any Authenticating Agent may at any time resign by giving
written notice of resignation to the Fiscal Agent and the Issuer. The Fiscal
Agent may at any time terminate the agency of any Authenticating Agent by giving
written notice of termination to such Authenticating Agent and the Issuer. Upon
receiving such notice of resignation or upon such a termination, the Fiscal
Agent may at its election, promptly appoint a successor Authenticating Agent,
whereupon the Fiscal Agent shall give written notice of such appointment to the
Issuer. The provisions of Sections 14 and 16 shall be applicable to any
Authenticating Agent.

                                        6            FISCAL AGENCY AGREEMENT
<Page>

     Section 5. NOTE ACCOUNT.

          (a)  On or prior to the Closing Date, the Fiscal Agent shall establish
a segregated account for the purpose of receiving and holding amounts deposited
hereunder by the Issuer for payment of amounts due and payable on the Notes (the
"NOTE ACCOUNT"). On each Payment Date, the Fiscal Agent shall apply available
funds held in the Note Account to the payment to Holders of amounts due and
payable on the Notes. The Fiscal Agent shall not be under any duty to advance
its own funds in any instance. If amounts deposited by the Issuer are
insufficient to pay amounts due and payable in full, the Fiscal Agent may apply
the available amount on deposit in the Note Account by distributing such amount
to Holders pro rata or in such other manner as the Fiscal Agent deems expedient.
The Fiscal Agent shall not be under any obligation to invest, or otherwise pay
interest on, amounts held in the Note Account from time to time.

     Section 6. AUTHORIZED REPRESENTATIVES.

     From time to time or at the request of the Fiscal Agent, the Issuer shall
furnish the Fiscal Agent with a signature list certifying the incumbency and
specimen signatures of the Authorized Representatives. The Fiscal Agent shall be
entitled to conclusively rely on the last such certificate delivered to it for
the purposes of determining the identity of Authorized Representatives.

     Section 7. PAYMENTS ON NOTES AND DISBURSEMENTS FROM THE NOTE ACCOUNT;
RECORD DATES.

          (a)  On each Payment Date, all amounts in the Note Account shall be
applied as provided in Section 5 hereof.

          (b)  Payments on the Notes shall be due and payable on each Payment
Date to the Persons in whose name the Notes are registered at the close of
business on the Record Date for such Distribution Date.

          (c)  In the case where any Payment Date is not a Business Day, payment
need not be made by the Fiscal Agent on such date, but may be made on the
immediately succeeding Business Day.

     Section 8. PAYMENTS ON THE NOTES; WITHHOLDING.

          (a)  All payments in respect of the Notes or otherwise hereunder shall
be made in U.S. Dollars. All payments on the Notes shall be made by U.S. Dollar
check drawn by the Fiscal Agent on an account maintained by it and shall be
mailed or, at the option of the relevant Noteholder, transmitted by wire
transfer from an account maintained by the Fiscal Agent (subject to usual and
necessary banking procedures regarding U.S. Dollar denominated accounts),
subject in all cases to any tax, fiscal or other laws or regulations applicable
in the place of payment. Any such Holder desiring to receive such wire transfers
shall deliver a written request therefor to the Fiscal Agent setting forth the
Note numbers of the Notes held by it and for which it desires to receive payment
by wire transfer and specifying the banking institution and account number (with
any other appropriate information necessary to enable the Fiscal Agent to
transmit such payment and to assure proper credit to such Holder's account) to
which such payments are to be

                                        7            FISCAL AGENCY AGREEMENT
<Page>

transferred. A record of each payment made shall be maintained by or on behalf
of the Fiscal Agent in accordance with its customary procedures, and such record
shall be PRIMA FACIE evidence that the payment in question has been made. The
Issuer and the Fiscal Agent shall be fully protected in conclusively relying
upon any such request in making payments on the Notes, and any payment
transmitted in accordance with such request shall be deemed to have been made
upon transmission thereof to the banking institution identified in such request.

          (b)  Subject to the foregoing provisions of this Section 8, each Note
delivered under this Agreement and upon registration of transfer of or in
exchange for or in lieu of any other Note shall carry the rights of accrued and
unpaid amounts due on such other Note.

          (c)  The Issuer and the Fiscal Agent may deem and treat the registered
Holder of any Note as the absolute owner of such Note, whether or not such Note
shall be overdue and notwithstanding any notation of ownership or other writing
on such Note, for the purpose of receiving payment thereof and for all other
purposes, and neither the Issuer nor the Fiscal Agent shall be affected by any
notice to the contrary. All such payments so made to such Holder or upon such
Holder's order shall be valid and, to the extent of the sum or sums so paid,
effectual to satisfy and discharge the liability for the monies payable upon any
such Note.

     Section 9. [RESERVED.]

     Section 10. NOTE REGISTER; REGISTRATION, TRANSFER, EXCHANGE; PERSONS DEEMED
OWNERS.

          (a)  The Issuer shall cause to be kept a register (the "NOTE
REGISTER") in which, subject to such reasonable regulations as it may prescribe,
the Issuer shall provide for the registration of the Notes and the registration
of transfers of the Notes. The Fiscal Agent is hereby irrevocably appointed by
the Issuer as "NOTE REGISTRAR" for the purpose of registering Notes and
transfers of Notes as herein provided (it being hereby acknowledged that nothing
contained herein shall limit, bar or restrict the ability or the right of the
Fiscal Agent to appoint agents or to delegate duties from time to time or to
resign or to be removed pursuant to Section 22). The Issuer shall notify the
Fiscal Agent in writing of any Notes owned by or pledged to the Issuer or any of
its affiliates promptly upon the acquisition thereof or the creation of such
pledge.

     All Notes issued upon any registration of transfer or exchange of Notes
shall be the valid obligations of the Issuer, evidencing the same debt, and
entitled to the same benefits under this Agreement, as the Notes surrendered
upon such registration of transfer or exchange.

     Every Note presented or surrendered for registration of transfer or
exchange shall (if so required by the Issuer or the Fiscal Agent) be duly
endorsed, or be accompanied by a written instrument of transfer in form
satisfactory to the Fiscal Agent duly executed by the Holder thereof or its
attorney-in-fact duly authorized in writing.

     No service charge shall be made to a Holder for any registration of
transfer or exchange of Notes, but the Issuer and/or the Fiscal Agent may
require payment of a sum sufficient to cover any tax or other governmental
charge that may be imposed in connection with any registration of transfer or
exchange of Notes.

                                        8            FISCAL AGENCY AGREEMENT
<Page>

          (b)  No Note may be sold or transferred (including, without limitation
by pledge or hypothecation) unless the purchaser or transferee is a Qualified
Institutional Buyer, which sale or transfer is exempt from the registration
requirements of the Securities Act and is exempt under applicable state
securities laws. No purported transfer of any interest in any Note or any
portion thereof that is not made in accordance with this Section 10 shall be
binding upon the Fiscal Agent or the Issuer and any such purported transfer
shall be null and void AB INITIO and vest in the transferee no rights against
the Fiscal Agent or the Issuer.

          (c)  TRANSFERS AND EXCHANGES OF NOTES. Transfers of Notes, in whole or
in part, shall only be made in accordance with this Section 10(c).

               (i)  TRANSFER OF NOTES. Upon receipt by the Fiscal Agent, as Note
     Registrar, of (A) a Holder's Note properly endorsed for assignment to a
     transferee and (B) a properly completed and executed Investor
     Representation Letter in the form of EXHIBIT B, the Fiscal Agent will cause
     one or more Notes in definitive form to be issued to the transferee(s).

               (ii) EXCHANGE OF NOTES. If a Holder of one or more Notes wishes
     at any time to exchange such Notes for one or more Notes of different
     notional amounts (but not less than the minimum authorized denomination
     applicable thereto) that will be beneficially owned by such Holder, such
     Holder may exchange or cause the exchange of such Notes for an equivalent
     interest in new Notes in definitive form as provided below. Upon receipt by
     the Fiscal Agent, as Note Registrar, of (A) such Holder's Notes properly
     endorsed for such exchange and (B) written instructions from the Holder (or
     such beneficial Holder, as identified by the Holder) of such Note
     designating the number and notional amounts of the Notes to be exchanged
     (the aggregate of such notional amounts being equal to the aggregate
     notional amount of the Notes surrendered for exchange) and certifying that
     such exchange does not represent a change in beneficial ownership, then the
     Fiscal Agent, as Note Registrar, shall cancel such Note in accordance with
     Section 12 hereof, record the exchange in the Note Register in accordance
     with Section 10(a) hereof and authenticate and deliver one or more Notes in
     definitive form, registered in the same names as the Notes surrendered by
     such Holder or such different names as are specified in the endorsement
     described in clause (A) above, in notional amounts designated by such
     Holder (the aggregate of such amounts being equal to the beneficial
     interest in the Notes surrendered by such Holder).

          (d)  The Fiscal Agent may conclusively rely on the statement in any
Investor Representation Letter and shall be entitled to rely conclusively on the
continuing accuracy thereof from time to time (unless and until a Responsible
Officer is otherwise notified in writing by the signatory thereto or by the
Issuer) in determining whether the provisions of this Section 10 have been
complied with. Notwithstanding anything to the contrary in this Agreement, no
transfer of a Note may be made if such transfer would require registration of
the Issuer under the Investment Company Act (subject, as regards the Fiscal
Agent's duties, to Section 10(f) below).

          (e)  At any time when the Issuer is not subject to Section 13 or 15(d)
of the United States Securities Exchange Act of 1934, as amended, upon the
request of any Noteholder, the Issuer shall promptly furnish to such Noteholder
or to a prospective purchaser of any Note

                                        9            FISCAL AGENCY AGREEMENT
<Page>

designated by such Noteholder, as the case may be, the information which the
Issuer determines to be required to be delivered pursuant to Rule 144A(d)(4)
under the Securities Act ("RULE 144A INFORMATION") in order to permit compliance
by such Noteholder with Rule 144A in connection with the resale of such Note by
such Noteholder. Upon request by the Issuer, the Fiscal Agent shall cooperate
with the Issuer in mailing or otherwise distributing (at the Issuer's expense)
to such Noteholders or prospective purchasers, at and pursuant to the Issuer's
written direction, the foregoing materials prepared and provided by the Issuer;
PROVIDED, HOWEVER, that the Fiscal Agent shall be entitled to affix thereto or
enclose therewith such disclaimers as the Fiscal Agent shall deem reasonably
appropriate, at its discretion (such as, for example, a disclaimer that such
Rule 144A Information was assembled by the Issuer and not by the Fiscal Agent,
that the Fiscal Agent has not reviewed or verified the accuracy thereof, and
that it makes no representation as to the sufficiency of such information under
Rule 144A or for any other purpose).

          (f)  Notwithstanding any term to the contrary appearing herein or in
the Notes, the Fiscal Agent shall not be responsible for ascertaining whether
any transfer complies with, or otherwise to monitor or determine compliance
with, the requirements or terms of the Securities Act, applicable state
securities laws, ERISA, the Code or the Investment Company Act; except that if a
certificate is specifically required by the terms of this Section 10 to be
provided to the Fiscal Agent by a prospective transferee, transferor or the
Issuer, the Fiscal Agent shall be under a duty to receive and examine the same
to determine whether it conforms substantially on its face to the applicable
requirements of this Section 10. The Investor Representation Letter furnished
pursuant to this Section 10 may be relied on conclusively by the Fiscal Agent in
determining whether the provisions of this Section 10 have been complied with.
None of the Issuer, the Fiscal Agent or any other person shall be required to
register the Notes under the Securities Act or any state securities laws.

          (g)  If a Responsible Officer of the Fiscal Agent has actual knowledge
that (i) a transfer or attempted or purported transfer of any Note or interest
therein was consummated in compliance with the provisions of this Section 10 on
the basis of a materially incorrect certification from the transferor or
purported transferor, (ii) a transferee failed to deliver to the Fiscal Agent
any certificate required to be delivered hereunder or (iii) the Holder of any
Note or interest therein is in material breach of any representation or
agreement set forth in any certificate or any deemed representation or agreement
of such Holder, the Fiscal Agent shall not register such attempted or purported
transfer and if a transfer has been registered, such transfer shall be
absolutely null and void AB INITIO and shall vest no rights in the purported
transferee (such purported transferee, a "DISQUALIFIED TRANSFEREE") and the last
preceding Holder of such Note that was not a Disqualified Transferee shall be
restored to all rights as a Holder thereof retroactively to the date of transfer
of such Note by such Holder.

          (h)  If and to the extent any Notes are registered to DTC, or its
nominee, or another clearing agency, or any custodian on its behalf, (i)
transfers of beneficial interests shall be pursuant to the applicable rules and
procedures of DTC or such other clearing agency, as the case may be, (ii) the
Fiscal Agent shall have no responsibility for compliance with any of the
restrictions on transfer set forth herein in connection with such transfers of
beneficial interest, and (iii) the Fiscal Agent shall not be responsible for the
accuracy of the records of DTC or any actions or omissions of DTC.

                                       10            FISCAL AGENCY AGREEMENT
<Page>

     Section 11. MUTILATED, DESTROYED, LOST, OR STOLEN NOTES.

          (a)  In case any Note shall become mutilated or defaced, or be
destroyed, stolen or lost, the Issuer shall execute, and the Fiscal Agent or
Authenticating Agent shall authenticate and deliver, a new Note bearing a number
not contemporaneously outstanding, in substitution for the Note so mutilated or
defaced, destroyed, stolen or lost. In every case, the applicant for a
substituted Note shall, at its expense, furnish to the Issuer and the Fiscal
Agent such security or indemnity as may be required by them to save each of them
harmless. In every case of destruction, loss or theft, the applicant shall also
furnish to the Issuer and the Fiscal Agent evidence to their satisfaction of the
destruction, loss or theft of such Note and of the ownership thereof. In every
case of mutilation or defacement, the applicant shall surrender to the Fiscal
Agent the Note so mutilated or defaced. Upon the issuance of any substitute
Note, the Fiscal Agent may require the payment of a sum sufficient to cover any
tax or other governmental charge that may be imposed in relation thereto and any
other expenses connected therewith.

          (b)  In case any mutilated, defaced, destroyed, stolen or lost Note
has matured or is about to mature, the Issuer may pay or authorize the payment
of the same not earlier than the date such payment is otherwise due instead of
issuing a substitute Note, provided security or indemnity is furnished as above
required.

          (c)  Every substitute Note issued pursuant to the provisions of this
Section 11 by virtue of the fact that any Note is destroyed, stolen or lost
shall, with respect to such Note, constitute an additional contractual
obligation of the Issuer, whether or not the destroyed, stolen or lost Note
shall at any time be enforceable by any person, and shall be entitled to all the
benefits of this Agreement equally and proportionately with any and all other
Notes duly issued hereunder.

          (d)  All Notes shall be held and owned upon the express condition that
(to the extent permitted by law) the foregoing provisions of this Section are
exclusive with respect to the replacement or payment of mutilated, defaced,
destroyed, stolen or lost Notes and shall preclude any and all other rights or
remedies notwithstanding any law or statute now existing or hereinafter enacted
to the contrary with respect to the replacement or payment of negotiable
instruments or other securities without their surrender.

     Section 12. CANCELLATION.

     All Notes surrendered for payment, registration of transfer or exchange
shall, if surrendered to any person other than the Fiscal Agent, be delivered to
the Fiscal Agent and shall be promptly cancelled by it. The Issuer may at any
time deliver to the Fiscal Agent for cancellation any Notes previously
authenticated and delivered hereunder which the Issuer may have acquired in any
manner whatsoever, and all Notes so delivered shall be promptly cancelled by the
Fiscal Agent. No Notes shall be authenticated in lieu of or in exchange for any
Notes cancelled as provided in this Section, except as expressly permitted by
this Agreement. Cancelled Notes may be held or destroyed by the Fiscal Agent,
and the Fiscal Agent shall promptly deliver to the Issuer a certificate of
destruction with respect to any Note which is destroyed.

                                       11            FISCAL AGENCY AGREEMENT
<Page>

Section 13. APPLICATION OF FUNDS; RETURN OF UNCLAIMED FUNDS.

     Until used or applied as herein provided, all funds received by the Fiscal
Agent hereunder shall be held for the purposes for which they were received and
for the benefit of the Holders of the Notes. Subject to any abandoned property,
property laws that may be applicable, any funds paid, or caused to be paid, by
the Issuer to the Fiscal Agent and held by the Fiscal Agent for payment of
amounts due in respect of any Notes that remain unclaimed for thirty (30) months
after such amounts shall have become due and payable, shall be paid or repaid,
as the case may be, to the Issuer by the Fiscal Agent and the Fiscal Agent shall
inform the Issuer as to the specific Notes to which such funds relate, and any
Person claiming such funds shall thereafter have an unsecured claim against the
Issuer for payment thereof and shall look only to the Issuer for the payment
thereof and all liability of the Fiscal Agent with respect to such funds shall
thereupon cease. Any funds held by the Fiscal Agent shall remain uninvested. The
Fiscal Agent may also adopt and employ, at the expense of the Issuer, any other
reasonable means of notification of such release of payment (including, but not
limited to, mailing notice of such release to Holders or whose right to or
interest in monies due and payable but not claimed is determinable from the
records of the Fiscal Agent, at the last address of record of each such Holder).

Section 14. FISCAL AGENT'S STANDARD OF CARE; LIABILITY.

          (a)  Neither the Fiscal Agent nor its directors, officers, employees
or agents shall be liable for any act or omission hereunder except in the case
of gross negligence, bad faith or willful misconduct of the Fiscal Agent in
violation of its duties under this Agreement. The duties and obligations of the
Fiscal Agent shall be determined solely by the express provisions of this
Agreement, its duties and obligations shall be solely those specifically set
forth in this Agreement, and no implied covenants shall be read into this
Agreement against the Fiscal Agent.

          (b)  The Fiscal Agent may consult with counsel selected by the Fiscal
Agent and shall be fully protected in any action taken or not taken in good
faith in accordance with the advice of such counsel. The Fiscal Agent may rely
conclusively and shall be fully protected in acting or refraining from acting
upon any notice, certificate or other document furnished to it hereunder and
reasonably believed by it in good faith to be genuine. The Fiscal Agent shall be
entitled to presume the genuiness and due authorization of any signature
appearing on any document or instrument. The Fiscal Agent shall not be liable
for any action taken by it in good faith and reasonably believed by it to be
within the discretion or powers conferred upon it, or taken by it pursuant to
any direction or instruction by which it is governed hereunder, or omitted to be
taken by it by reason of the lack of direction or instruction required hereby
for such action. The Fiscal Agent shall in no event be liable for the
application or misapplication of funds by any other Person, or for the acts or
omissions of any other Person (including, without limitation, the Issuer or any
authenticating agent). The Fiscal Agent shall not be bound to make any
investigation into the facts or matters stated in any certificate, report or
other document; provided, however, that if the form thereof is prescribed by
this Agreement the Fiscal Agent shall examine the same to determine whether it
conforms on its face to the requirements hereof. The Fiscal Agent may exercise
or carry out any of its duties under this Agreement either directly or
indirectly through agents, nominees, custodians or attorneys, and shall not be
responsible for any acts or omissions on the part of any such agent, nominee,
custodian or attorney appointed

                                       12            FISCAL AGENCY AGREEMENT
<Page>

with due care. To the extent permitted by applicable law, the Fiscal Agent shall
not be required to give any bond or surety in the execution of its duties. The
Fiscal Agent shall not be obligated to take any remedial action unless and until
first provided indemnity and security satisfactory to it for payment of any
costs, expenses or liabilities that may be incurred. The Fiscal Agent shall not
be deemed to have knowledge or notice of any matter unless actually known to a
Responsible Officer of the Fiscal Agent or unless a Responsible Officer of the
Fiscal Agent has received written notice thereof from the Issuer, the Collateral
Agent or the Holder of a Note.

          (c)  In the absence of gross negligence or bad faith on the part of
the Fiscal Agent, the Fiscal Agent may conclusive rely, as to the truth of the
statements and the correctness of the opinions expressed therein, upon any
certificates or opinions furnished to the Fiscal Agent which conform to the
requirements of this Agreement.

          (d)  The Fiscal Agent shall not be liable for any error of judgment
made in good faith by a Responsible Officer or Responsible Officers of the
Fiscal Agent, unless it shall be conclusively determined by a court of competent
jurisdiction that the Fiscal Agent was negligent in ascertaining the pertinent
facts.

          (e)  None of the provisions of this Agreement shall require the Fiscal
Agent to expend or risk its own funds or otherwise to incur any liability,
financial or otherwise, in the performance of any of its duties hereunder, or in
the exercise of any of its rights or powers if it shall have reasonable grounds
for believing that repayment of such funds or indemnity satisfactory to it
against such risk or liability is not assured to it.

          (f)  Whenever in the administration of the provisions of this
Agreement the Fiscal Agent shall reasonably deem it necessary or desirable that
a matter be proved or established prior to the taking or suffering of any action
to be taken hereunder, such matter (unless other evidence in respect thereof be
herein specifically prescribed) may, in the absence of gross negligence or bad
faith on the part of the Fiscal Agent, be deemed to be conclusively proved and
established by a certificate signed by an Authorized Representative and
delivered to the Fiscal Agent and such certificate, in the absence of gross
negligence or bad faith on the part of the Fiscal Agent, shall be full authority
to the Fiscal Agent for any action taken, suffered or omitted by it under the
provisions of this Agreement in reliance thereon.

          (g)  Anything in this Agreement to the contrary notwithstanding, in no
event shall the Fiscal Agent be liable for special, indirect or consequential
loss or damage of any kind whatsoever (including but not limited to lost
profits), even if the Fiscal Agent has been advised of the likelihood of such
loss or damage and regardless of the form of the action.

Section 15. ISSUANCE OF NOTES ON CLOSING DATE.

     The Notes to be issued on the Closing Date shall be executed by the Issuer
and shall be delivered to the Fiscal Agent for authentication, and thereupon the
same shall be authenticated and delivered by the Fiscal Agent (or any
authenticating agent appointed thereby) upon Issuer Order.

                                       13            FISCAL AGENCY AGREEMENT
<Page>

Section 16. COMPENSATION AND INDEMNIFICATION.

The Issuer agrees to pay to the Fiscal Agent such reasonable fees for its
services as shall be agreed from time to time between the Fiscal Agent and the
Issuer, and to reimburse the Fiscal Agent for its reasonable out-of-pocket
costs, expenses (including reasonable legal fees and expenses), disbursements
and advances, if any, incurred or made in accordance with any provisions of this
Agreement, its administration of the terms hereof, performance of its duties
hereunder or exercise an enforcement of the terms hereof (in each case whether
acting as fiscal agent, paying agent, registrar or otherwise hereunder), except
any such expense, cost, disbursement or advance as may be attributable to the
Fiscal Agent's gross negligence, bad faith or willful misconduct. The Issuer
agrees to indemnify and hold harmless the Fiscal Agent, its directors, officers,
employees and agents (each, an "Indemnified Party", and collectively, the
"Indemnified Parties") from and against any and all liabilities, damages,
losses, costs and expenses (including reasonable legal fees and expenses)
relating to or arising out of or in connection with the Fiscal Agent's
appointment hereunder, or its Agreements (in each case whether acting as fiscal
agent, paying agent, registrar or otherwise hereunder), except to the extent
caused by the gross negligence, bad faith or willful misconduct of such
Indemnified Party. The foregoing indemnity includes, but is not limited to, any
action taken or omitted in good faith within the scope of this Agreement upon
telephone, facsimile or other electronically transmitted instructions, if
authorized herein, received from or reasonably believed by the Fiscal Agent,
acting in good faith, to have been given by, an Authorized Representative. The
obligations of the Issuer pursuant to this Section shall survive the
satisfaction or termination of this Agreement, and the resignation or removal of
the Fiscal Agent pursuant to Section 22.

Section 17. SUPPLEMENTAL AGREEMENTS.

          (a)  WITHOUT CONSENT OF HOLDERS. Without the consent of any Holders of
the Notes, the Issuer and the Fiscal Agent, at any time and from time to time,
may enter into one or more agreements supplemental hereto for any of the
following purposes:

               (i)   to evidence the succession of a successor entity to the
     Issuer and the assumption by any such successor of the covenants of the
     Issuer herein and in the Notes; PROVIDED that such action shall not
     adversely affect the interests of the Holders of Notes in any material
     respect;

               (ii) to take any action deemed reasonably necessary by the Issuer
     to prevent the reduction of amounts payable on the Notes;

               (iii) to evidence and provide for the acceptance of appointment
     hereunder by a successor Fiscal Agent with respect to the Notes, pursuant
     to the requirements of Section 22 hereof;

               (iv) to take any action necessary or helpful to prevent the
     Issuer or the Fiscal Agent (in its capacity as Fiscal Agent under this
     Agreement) from becoming subject to any withholding or other taxes, fees or
     assessments;

               (v)   to cure any ambiguity, correct or supplement any provision
     herein which may be inconsistent with any other provision hereunder, or to
     make any other

                                       14            FISCAL AGENCY AGREEMENT
<Page>

     provisions with respect to matters or questions arising herein upon receipt
     by the Fiscal Agent of written direction from the Issuer (as to which the
     Fiscal Agent may rely) describing in reasonable detail such ambiguity or
     inconsistency or other circumstance requiring amendment, and the
     modification proposed; provided that such action shall not adversely affect
     the interests of the Holders of Notes in any material respect;

               (vi)  to correct any manifest error in any provision hereof
     upon receipt by the Fiscal Agent of written direction from the Issuer (as
     to which the Fiscal Agent may rely) describing in reasonable detail such
     error and the modification necessary to correct such error; or

               (vii) to increase the aggregate principal amount of Notes
     authorized and permitted to be issued hereunder to $28,750,000.

          (b)  WITH CONSENT OF HOLDERS. With the consent of the Holders of Notes
     representing more than 66-2/3% of the aggregate principal amount of the
     outstanding Notes affected by a supplemental agreement or agreement
     referred to below, the Issuer and the Fiscal Agent may enter into an
     agreement or agreements supplemental hereto for the purpose of adding any
     provisions to, or changing in any manner or eliminating any of the
     provisions of, this Agreement or of modifying in any manner the rights of
     the Holders of Notes under this Agreement; PROVIDED, HOWEVER, that no such
     supplemental agreement shall, without the consent of the Holder of each
     outstanding Note affected thereby:

               (i)   change the method or methods by which any payment amount
     shall be determined for any Note, or reduce the amount thereof, or change
     the coin or currency in which any Note or any amount thereon is payable; or

               (ii)  reduce the percentage amount of the outstanding Notes, the
     consent of whose Holders is required for any such supplemental agreement,
     or the consent of whose Holders is required for any waiver of compliance
     with certain provisions of this Agreement or certain defaults hereunder and
     their consequences provided for in this Agreement; or

(iii) modify any of the provisions of this Section 17, except to
increase any such percentage or to provide that certain other provisions of this
Agreement cannot be modified or waived without the consent of the Holder of each
outstanding Note affected thereby.

          (c)  EXECUTION AND EFFECT OF SUPPLEMENTAL AGREEMENTS. Upon the
execution of any supplemental agreement under this Section, this Agreement shall
be modified in accordance therewith, and such supplemental agreement shall form
a part of this Agreement for all purposes; and every Holder of a Note
theretofore or thereafter authenticated and delivered hereunder shall be bound
thereby. In executing any supplemental agreement pursuant to this Section 17,
the Fiscal Agent shall be entitled to receive, and shall be protected in
conclusively relying upon, an Opinion of Counsel to the effect that such
supplemental agreement, and the Fiscal Agent's execution and delivery thereof,
is authorized or permitted under this Agreement.

                                       15            FISCAL AGENCY AGREEMENT
<Page>

The Fiscal Agent shall not be obligated to enter into any supplemental agreement
which affects its rights, duties or obligations hereunder.

          (d)  REFERENCE TO SUPPLEMENTAL AGREEMENTS. Notes authenticated and
delivered after the execution of any supplemental agreement pursuant to this
Section 17 may, and shall if required by the Fiscal Agent, bear a notation in
form approved by the Fiscal Agent as to any matter provided for in such
supplemental agreement. If the Issuer shall so determine, new Notes so modified
as to conform, in the opinion of the Fiscal Agent and the Issuer, to any such
supplemental agreement, may be prepared and executed by the Issuer and
authenticated and delivered by the Fiscal Agent in exchange for outstanding
Notes.

     Section 18. LIMITATION ON SUITS.

It is understood and intended that no one or more of such Holders shall have any
right in any manner whatever by virtue of, or by availing of, any provision of
this Agreement to affect, disturb or prejudice the rights of any other Holder or
to obtain or to seek to obtain priority or preference over any other Holder or
to enforce any right under this Agreement, except in the manner herein provided
and for the equal and ratable benefit of all of such Holders.

     Section 19. [RESERVED.]

     Section 20. [RESERVED.]

     Section 21. NOTICES.

          (a)  All communications by or on behalf of the Issuer relating to the
issuance, transfer, exchange or payment of Notes or any interest therein shall
be directed to the Fiscal Agent at its address set forth in subsection (b)(ii)
hereof.

     Where this Agreement provides for notice to Noteholders of any event, such
notice shall be sufficiently given (unless otherwise herein expressly provided)
if such notice is in writing and either mailed, first-class postage prepaid, or
delivered via facsimile, hand delivery or overnight courier to each Noteholder
affected by such event, at such Noteholder's address as it appears on the Note
Register, in the case of (a) not later than the latest date, and not earlier
than the earliest date, prescribed for the giving of such notice.

     In any case where notice to Noteholders is given by mail, neither the
failure to mail such notice, nor any defect in any notice so mailed, to any
particular Noteholder shall affect the sufficiency of such notice with respect
to other Noteholders. Any notice that is given in the manner herein provided
shall conclusively be presumed to have been duly given whether or not actually
received by such Noteholder. Any notice to Noteholders provided for in this
Agreement shall be deemed to have been given on the date of mailing.

     Where this Agreement provides for notice in any manner, such notice may be
waived in writing by any Person entitled to receive such notice, either before
or after the event, and such waiver shall be the equivalent of such notice.
Waivers of notice by Noteholders shall be filed with the Fiscal Agent, but such
filing shall not be a condition precedent to the validity of any action taken in
reliance upon such waiver.

                                       16            FISCAL AGENCY AGREEMENT
<Page>

     In the event that, by reason of the suspension of the regular mail service
as a result of a strike, work stoppage or similar activity, it shall be
impractical to mail notice of any event to Noteholders when such notice is
required to be given pursuant to any provision of this Agreement, then any
manner of giving such notice as shall be reasonably satisfactory to the Fiscal
Agent shall be deemed to be a sufficient giving of such notice.

          (b)  Notices and other communications hereunder shall (except to the
extent otherwise expressly provided) be in writing and shall be addressed as
follows, or to such other addresses as the parties hereto shall specify from
time to time:

               (i)   if to the Issuer:
                     iBasis, Inc.
                     20 Second Avenue
                     Burlington, MA 01803
                     Telephone: 781-505-7500,

                     with a copy to: Johan V. Brigham, Esq., Bingham
                     McCutcheon LLP, 150 Federal Street, Boston MA
                     02110;

               (ii)  if to the Fiscal Agent or the Collateral Agent: at the
                     Corporate Trust Office, or at any other address
                     furnished in writing to the Issuer by the Fiscal Agent.

     Section 22. RESIGNATION OR REMOVAL OF FISCAL AGENT AND APPOINTMENT OF
SUCCESSOR FISCAL AGENT; MERGER, CONVERSION AND CONSOLIDATION.

          (a)  The Issuer agrees, for the benefit of the Holders from time to
time of the Notes, that there shall at all times be a Fiscal Agent hereunder,
which shall be a company authorized to engage in the activities set forth in
this Agreement, subject to supervision or examination by governmental
authorities, until all the Notes authenticated and delivered hereunder (A) shall
have been delivered to the Fiscal Agent for cancellation or (B) become due and
payable and monies sufficient to pay the amounts due in respect of the Notes
shall have been made available for payment and either paid or returned to the
Issuer as provided herein, whichever event occurs earlier. Any transfer agent
appointed by the Fiscal Agent pursuant to Section 8(b) of this Agreement shall
be a bank or trust company authorized to exercise corporate trust powers and
that has a combined capital and surplus of at least $50,000,000.

          (b)  The Fiscal Agent may at any time resign as such agent by giving
written notice to the Issuer of such intention on its part, specifying the date
on which its desired resignation shall become effective; PROVIDED, HOWEVER, that
such date shall be not less than 60 days after the giving of such notice by the
Fiscal Agent to the Issuer. The Fiscal Agent may be removed at any time by the
filing with it of an instrument in writing signed by an Authorized
Representative of the Issuer and specifying such removal and the date, which
shall be at least 60 days after the date of such written notice, upon which it
is intended to become effective. Any

                                       17            FISCAL AGENCY AGREEMENT
<Page>

such resignation or removal shall take effect on the date of the appointment by
the Issuer of a successor fiscal agent and the acceptance of such appointment by
such successor fiscal agent that qualifies as such under clause (a) of this
Section. In the event of resignation by the Fiscal Agent, if a successor agent
has not been appointed by the Issuer within 60 days after the giving of notice
by the Fiscal Agent of its intention to resign, the Fiscal Agent may, at the
expense of the Issuer, petition any court of competent jurisdiction for
appointment of a successor Fiscal Agent; provided that it shall be qualified
under clause (a) of this Section. Upon any such resignation or removal, the
Fiscal Agent shall transfer to the successor Fiscal Agent (or, if none shall
have been appointed, to the Issuer) all monies held by the Fiscal Agent on
behalf of the Issuer in respect of any Notes, any unissued Notes and all books
and records related to Notes maintained by the Fiscal Agent, including a copy of
the Note Register.

          (c)  Any corporation or bank into which the Fiscal Agent hereunder may
be merged or converted, or any corporation or bank with which the Fiscal Agent
may be consolidated, or any corporation or bank resulting from any merger,
conversion or consolidation to which the Fiscal Agent shall be a party, or any
corporation or bank to which the Fiscal Agent shall sell or otherwise transfer
all or substantially all of the corporate trust business of the Fiscal Agent,
shall be the successor Fiscal Agent under this Agreement without the execution
or filing of any paper or any further act on the part of any of the parties
hereto.

          (d)  The successor Fiscal Agent shall give prompt notice of the
resignation and removal of the Fiscal Agent and the appointment of a successor
Fiscal Agent to the Holders of the Notes by notifying the Holders of the Notes
in accordance with Section 21 hereof. Each notice shall include the name of the
successor Fiscal Agent and the address of the office from which this Agreement
shall be administered.

     Section 23. BENEFIT OF AGREEMENT.

     This Agreement is solely for the benefit of the parties hereto (and to the
extent provided herein, for the benefit of the Holders of the Notes from time to
time, or the beneficial owners for whose account they hold), and their
respective successors and assigns, and nothing herein, express or implied, shall
give to any other persons any benefits or any legal or equitable right, remedy
or claim under or by virtue of this Agreement. No party hereto may assign any of
its rights or obligations hereunder except with the prior written consent of all
the parties hereto.

     Section 24. [RESERVED.]

     Section 25. NOTES HELD BY THE FISCAL AGENT; OTHER BUSINESS RELATIONS.

     The Fiscal Agent, in its individual or other capacity, may become the owner
or pledgee of the Notes with the same rights it would have if it were not acting
as issuing and paying agent hereunder. The Fiscal Agent may conduct other
business with the Issuer from time to time (including but not limited to its
appointment and service as Collateral Agent under the Securities Exchange
Agreement ).

                                       18            FISCAL AGENCY AGREEMENT
<Page>

     Section 26. AMENDMENT.

     This Agreement may not be amended by either party hereto except in
accordance with the provisions of Section 17 hereof.

     Section 27. GOVERNING LAW; SEALED INSTRUMENT.

     This Agreement is to be delivered and performed in, and shall be construed
and enforced in accordance with, and the rights of the parties shall be governed
by, the laws of The Commonwealth of Massachusetts. Each of the parties intends
this Agreement to take effect as a sealed instrument.

     Section 28. COUNTERPARTS.

     This Agreement may be executed by the parties hereto in any number of
counterparts, and by each of the parties hereto in separate counterparts, and
each such counterpart, when so executed and delivered, shall be deemed to be an
original, but all such counterparts shall together constitute but one and the
same instrument.

     Section 29. EXHIBITS.

     The exhibits to this Agreement are hereby incorporated and made a part
hereof and are an integral part of this Agreement.

     Section 30. [RESERVED.]

     Section 31. PRESCRIPTION.

     The Notes shall become void unless presented for payment within ten years
from the related Relevant Date therefor. "RELEVANT DATE" means the date on which
the final payment in respect of the Notes first becomes due, except that if the
full amount of the monies payable has not been duly received by the Fiscal Agent
on or prior to such due date, it means the date on which such monies have been
so received.

     Section 32. IDENTIFICATION OF NOTEHOLDERS.

     On demand of the Issuer, a Holder of a Note shall notify the Issuer whether
or not such Note is held by a United States person and the name and status of
the Holder as an individual, partnership, corporation, or other entity and such
other information the Issuer shall reasonably request for purposes of tax
reporting of the Issuer or other Noteholders.

     Section 33. TERMINATION: SURVIVAL OF PROVISIONS.

     Upon the soonest to occur of (i) the date on which the final payment on the
Notes (whether at maturity, upon acceleration or otherwise) been made, (ii) the
date on which all of the outstanding Notes have otherwise been surrendered to
the Fiscal Agent by the Issuer or on its behalf to the Fiscal Agent for
cancellation, or (ii) the date on which the Issuer, the Fiscal Agent and the
Holders of outstanding Notes otherwise agree in writing that this Agreement
shall

                                       19            FISCAL AGENCY AGREEMENT
<Page>

terminate (and, in the case of any of the foregoing, the Fiscal Agent shall have
distributed or applied all of the funds held in the Note Account in accordance
with this Agreement), the obligations and duties of the Fiscal Agent under this
Agreement shall terminate. Notwithstanding the termination of this Agreement,
the rights of the Fiscal Agent and obligations of the Issuer under Section 16,
the rights of the Issuer under Section 32 and the obligations of the Noteholders
under Section 32, shall survive.

     Section 34. Successors and Assigns.

     This Agreement shall be binding upon the Fiscal Agent and the Issuer and
their respective successors and assigns and shall inure to the benefit of the
Fiscal Agent and the Issuer and their respective successors and assigns.

                                       20            FISCAL AGENCY AGREEMENT
<Page>

IN WITNESS WHEREOF, each of the parties hereto has caused this Agreement to be
executed and delivered in its name and on its behalf by a duly authorized
officer, intending it to take effect as of the day and year first above written.

                                                iBASIS, INC.

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

                                                iBASIS GLOBAL, INC.

                                                By: /s/ Richard G. Tennant
                                                   -----------------------------
                                                Name:  Richard G. Tennant
                                                Title: Treasurer and CFO

                                                U.S. BANK NATIONAL ASSOCIATION,
                                                as Fiscal Agent

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

                                      S-1               FISCAL AGENCY AGREEMENT
<Page>

                                                                       EXHIBIT A

                                 [FORM OF NOTE]

UNLESS THIS CERTIFICATE IS PRESENTED BY AN AUTHORIZED REPRESENTATIVE OF THE
DEPOSITORY TRUST COMPANY (55 WATER STREET, NEW YORK, NEW YORK) (THE
"DEPOSITARY", WHICH TERM INCLUDES ANY SUCCESSOR DEPOSITARY FOR THE CERTIFICATES)
TO THE ISSUER OR ITS AGENT FOR REGISTRATION OF TRANSFER, EXCHANGE OR PAYMENT,
AND ANY CERTIFICATE ISSUED IS REGISTERED IN THE NAME OF CEDE & CO. OR IN SUCH
OTHER NAME AS REQUESTED BY AN AUTHORIZED REPRESENTATIVE OF THE DEPOSITARY (AND
ANY PAYMENT HEREIN IS MADE TO CEDE & CO. OR TO SUCH OTHER ENTITY AS IS REQUESTED
BY AN AUTHORIZED REPRESENTATIVE OF THE DEPOSITARY), ANY TRANSFER, PLEDGE, OR
OTHER USE HEREOF FOR VALUE OR OTHERWISE BY OR TO ANY PERSON IS WRONGFUL INASMUCH
AS THE REGISTERED OWNER HEREOF, CEDE & CO., HAS AN INTEREST HEREIN. THE NOTE
EVIDENCED HEREBY 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) 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 NOTE RESELL OR OTHERWISE TRANSFER THIS NOTE
EXCEPT (A) TO iBASIS, INC. OR ANY SUBSIDIARY THEREOF, (B) TO A QUALIFIED
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); (3) PRIOR TO SUCH TRANSFER (OTHER THAN A TRANSFER PURSUANT TO CLAUSE
(2)(C) ABOVE), IT WILL FURNISH TO U.S. NATIONAL BANK ASSOCIATION, AS FISCAL
AGENT (OR A SUCCESSOR FISCAL AGENT, AS APPLICABLE), SUCH CERTIFICATIONS, LEGAL
OPINIONS OR OTHER INFORMATION AS THE FISCAL AGENT MAY REASONABLY REQUIRE TO
CONFIRM THAT SUCH TRANSFER IS BEING MADE PURSUANT TO AN EXEMPTION FROM, OR IN A
TRANSACTION NOT SUBJECT TO, THE REGISTRATION REQUIREMENTS OF THE SECURITIES ACT;
AND (4) AGREES THAT IT WILL DELIVER TO EACH PERSON TO WHOM THIS NOTE IS
TRANSFERRED A NOTICE SUBSTANTIALLY TO THE EFFECT OF THIS LEGEND. IN CONNECTION
WITH ANY TRANSFER OF THIS NOTE, THE HOLDER MUST CHECK THE APPROPRIATE BOX SET
FORTH ON THE REVERSE HEREOF RELATING TO THE MANNER OF SUCH TRANSFER AND SUBMIT
THIS CERTIFICATE TO U.S. NATIONAL BANK ASSOCIATION, AS FISCAL AGENT (OR A
SUCCESSOR FISCAL AGENT, AS APPLICABLE). THE FISCAL AGENCY AGREEMENT CONTAINS A
PROVISION REQUIRING THE FISCAL AGENT TO REFUSE TO REGISTER ANY TRANSFER OF THIS
NOTE IN VIOLATION OF THE FOREGOING RESTRICTION.

THE TERMS OF THIS NOTE ARE SUBJECT TO THAT CERTAIN SUBORDINATION AGREEMENT DATED
AS OF JANUARY 30, 2003, AMONG SILICON VALLEY BANK,

                                      A-1
<Page>

THE CREDITORS NAMED THEREIN AND U.S. BANK NATIONAL ASSOCIATION, AS COLLATERAL
AGENT AND FISCAL AGENT.

                                      A-2
<Page>

                                  iBASIS, INC.
                              iBASIS GLOBAL, INC.
                       11.5% SENIOR SECURED NOTE DUE 2005

                                                             CUSIP: ____________
No.: ___                                                            $15,100,000

iBasis, Inc., a corporation duly organized and validly existing under the laws
of the State of Delaware, and iBasis Global, Inc., a corporation duly organized
and validly existing under the laws of the State of Delaware (herein
collectively called the "Issuer", which term includes any successor corporation
under the Fiscal Agency Agreement referred to on the reverse hereof), for value
received hereby, on a joint and several basis, promise to pay to Cede & Co. or
registered assigns, the principal sum of Fifteen Million One Hundred Thousand
Dollars ($15,100,000) on January 15, 2005, at the office or agency of the Issuer
maintained for that purpose in accordance with the terms of the Fiscal Agency
Agreement, in such coin or currency of the United States of America as at the
time of payment shall be legal tender for the payment of public and private
debts, and to pay interest, semi-annually on January 15 and July 15 of each
year, commencing July 15, 2003, on said principal sum at said office or agency,
in like coin or currency, at the rate per annum of 11.5%, from January 15 or
July 15, as the case may be, next preceding the date of this Note to which
interest has been paid or duly provided for, unless the date hereof is a date to
which interest has been paid or duly provided for, in which case from the date
of this Note, or unless no interest has been paid or duly provided for on the
Notes, in which case from January _30, 2003, until payment of said principal sum
has been made or duly provided for.

Notwithstanding the foregoing, if the date hereof is after any January 1 or July
1, as the case may be, and before the following January 15 or July 15, this Note
shall bear interest from such January 15 or July 15; provided, however, that if
the Issuer shall default in the payment of interest due on such January 15 or
July 15, then this Note shall bear interest from the next preceding January 15
or July 15 to which interest has been paid or duly provided for or, if no
interest has been paid or duly provided for on such Note, from January _30,
2003. Except as otherwise provided in the Fiscal Agency Agreement or the
Exchange Agreement referred to on the reverse hereof, the interest payable on
the Note pursuant to the Exchange Agreement on any January 15 or July 15 will be
paid to the Person entitled thereto as it appears in the Note register at the
close of business on the record date, which shall be the January 1 or July 1
(whether or not a Business Day) next preceding such January 15 or July 15, as
provided in the Fiscal Agency Agreement; provided, however, that any such
interest not punctually paid or duly provided for shall be payable as provided
in the Exchange Agreement or the Fiscal Agency Agreement. Interest may, at the
option of the Issuer, be paid either (i) by check mailed to the registered
address of such Person (provided that the holder of Notes with an aggregate
principal amount in excess of $2,000,000 shall, at the written election of such
holder, be paid by wire transfer of immediately available funds) or (ii) by
transfer to an account maintained by such Person located in the United States;
provided, however, that payments to the Depositary will be made by wire transfer
of immediately available funds to the account of the Depositary or its nominee.
Reference is made to the further provisions of this Note set forth on the
reverse hereof, including, without limitation, provisions subordinating the
payment of principal of and premium, if any, and interest on the Notes to the
prior payment in full of all Senior Debt, as defined in the

                                      A-3
<Page>

Subordination Agreement referred to on the reverse hereof. Such further
provisions shall for all purposes have the same effect as though fully set forth
at this place.

This Note shall be deemed to be a contract made under the laws of The
Commonwealth of Massachusetts, and for all purposes shall be construed in
accordance with and governed by the laws of The Commonwealth of Massachusetts,
without regard to the principles of conflicts of laws.

This Note shall not be valid or become obligatory for any purpose until the
certificate of authentication hereon shall have been manually signed by the
Fiscal Agent or a duly authorized authenticating agent under the Fiscal Agency
Agreement.

                                      A-4
<Page>

IN WITNESS WHEREOF, the Issuer has caused this Note to be duly executed.

                                                iBASIS, INC.

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

                                                iBASIS GLOBAL, INC.

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

Dated: January ___, 2003

FISCAL AGENT'S CERTIFICATE OF AUTHENTICATION
This is one of the Notes described in the within-named Fiscal Agency Agreement.

U.S. BANK NATIONAL ASSOCIATION, as Fiscal Agent

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

By:
   -------------------------------
      As Authenticating Agent
  (if different from Fiscal Agent)

                                      A-5
<Page>

                                REVERSE OF NOTE

                                  iBASIS, INC.
                              iBASIS GLOBAL, INC.

                      11.5% SENIOR SECURED NOTES DUE 2005

This Note is one of a duly authorized issue of Notes of the Issuer, designated
as its 11.5% Senior Secured Notes Due 2005 (herein called the "Notes"), limited
to the aggregate principal amount of $15,100,000, all issued or to be issued
under and pursuant to a Securities Exchange Agreement dated as of January 30,
2003 (herein called the "Exchange Agreement"), among the Issuer, iBasis
Securities Corporation, the Symphony Funds party thereto and U.S. Bank National
Association, as collateral agent (herein called the "Collateral Agent") to which
Exchange Agreement and all exchange agreements supplemental thereto reference is
hereby made for a description of the rights, limitations of rights, obligations,
duties and immunities thereunder of the Collateral Agent, the Issuer and the
holders of the Notes. The Issuer has appointed U.S. Bank National Association as
fiscal agent, (herein called the "Fiscal Agent") and as paying agent in respect
of the Notes upon the terms and subject to the conditions contained in a Fiscal
Agency Agreement dated as of January _30, 2003 (herein called the "Fiscal Agency
Agreement"), between the Issuer and the Fiscal Agent.

In case an Event of Default (as defined in the Exchange Agreement) shall have
occurred and be continuing, the principal of, premium, if any, and accrued
interest on all Notes may be declared by either the Collateral Agent or the
holders of not less than 25% in aggregate principal amount of the Notes then
outstanding, and upon said declaration shall become, due and payable, in the
manner, with the effect and subject to the conditions provided in the Exchange
Agreement.

The Exchange Agreement contains provisions prohibiting the changing, waiver,
discharge or termination of the Exchange Agreement without the consent of each
holder of a Note directly affected thereby if such change, waiver, discharge or
termination shall (i) extend the fixed maturity of any Note, or reduce the rate
or extend the time of payment of interest thereon, or reduce the principal
amount thereof, (ii) amend, modify or waive the provisions of Section 13.4 of
the Exchange Agreement, (iii) reduce the percentage specified in, or otherwise
modify the definition of "Demand Holders" or "Required Holders" stated therein,
(iv) consent to the assignment or transfer by the Issuer of any of its rights
and obligations under the Exchange Agreement, (v) establish any new obligations
for any holder of a Note not relating to the subject matter of the Exchange
Agreement or (ii) release all or substantially all of the collateral or
guarantees with respect to the Obligations specified in the Exchange Agreement.
Subject to the provisions of the Exchange Agreement, the holders of a majority
in aggregate principal amount of the Notes at the time outstanding may on behalf
of the holders of all of the Notes waive any past Default or Event of Default
under the Exchange Agreement and its consequences except a default in the
payment of interest. Any such consent or waiver by the holder of this Note
(unless revoked as provided in the Exchange Agreement) shall be conclusive and
binding upon such holder and upon all future holders and owners of this Note and
any Notes which may be issued in exchange or substitution hereof, irrespective
of whether or not any notation thereof is made upon this Note or such other
Notes.

                                      A-6
<Page>

The indebtedness evidenced by the Notes is, to the extent and in the manner
provided in the Subordination Agreement dated as of January 30, 2003 (herein
called the "Subordination Agreement"), among the Investors party thereto and
Silicon Valley Bank, subordinated and subject in right of payment to the prior
payment in full of all Senior Debt (as defined in the Subordination Agreement),
and this Note is issued subject to the provisions of the Subordination Agreement
with respect to such subordination. Each holder of this Note, by accepting the
same, agrees to and shall be bound by such provisions.

No reference herein to the Exchange Agreement, the Fiscal Agency Agreement or
the Subordination Agreement and no provision of this Note or of the Exchange
Agreement, the Fiscal Agency Agreement or the Subordination Agreement shall
alter or impair the obligation of the Issuer, which is absolute and
unconditional, to pay the principal of and any premium and interest on this Note
at the place, at the respective times, at the rate and in the coin or currency
herein prescribed.

Interest on the Notes shall be computed on the basis of a 360-day year of twelve
30-day months. The Notes are issuable in registered form, without coupons, in
denominations of $1,000 principal amount and any integral multiple of $1,000. At
the office or agency of the Issuer referred to on the face hereof, and in the
manner and subject to the limitations provided in the Exchange Agreement,
without payment of any service charge but with payment of a sum sufficient to
cover any tax, assessment or other governmental charge that may be imposed in
connection with any registration or exchange of Notes, Notes may be exchanged
for a like aggregate principal amount of Notes of any other authorized
denominations.

The Notes may be prepaid at the election of the Issuer, as a whole or in part
from time to time, at any time, upon notice as set forth in Section 4.2 of the
Exchange Agreement, at the following prepayment prices (expressed in percentages
of the outstanding principal amount of the Note, as the case may be, being
prepaid) plus accrued and unpaid interest on such prepaid principal amount to
the prepayment date, minus the number of percentage points reflected by the
product of (i) 10.1695 and (ii) the difference between (A) the average closing
trading price of the Common Stock of iBasis, Inc. (the "Common Stock") for the
five trading days immediately prior to, but not including, the date of such
prepayment and (B) the Common Stock price denoted below in the column titled
"Minimum Common Stock Price" (the "Note Prepayment Price"); provided, however,
that in no event shall the Note Prepayment Price be less than 100% of the
outstanding principal amount of the Notes to be prepaid, plus accrued and unpaid
interest on such principal amount to the prepayment date:

                                      A-7
<Page>

<Table>
<Caption>
                                                                    PERCENTAGE OF
                                                                    OUTSTANDING                MINIMUM COMMON
DATE OF PREPAYMENT                                                  PRINCIPAL AMOUNT           STOCK PRICE
-------------------------------------------------------------------------------------------------------------
AFTER                              PRIOR TO AND INCLUDING
-------------------------------------------------------------------------------------------------------------
<S>                                <C>                              <C>                        <C>
November 15, 2002                  January 15, 2003                 124.9167%                  $2.00
January 15, 2003                   July 15, 2003                    123.0000%                  $2.25
July 15, 2003                      January 15, 2004                 117.2500%                  $3.50
January 15, 2004                   July 15, 2004                    111.5000%                  $4.25
July 15, 2004                      January 15, 2005                 105.7500%                  $5.00
</Table>

If a Change of Control (as defined in the Exchange Agreement) occurs at any time
prior to maturity of the Notes, the Issuer shall, within one Business Day, make
an offer to prepay all of the Notes then outstanding at the Note Prepayment
Price set forth above. If the Issuer or any Subsidiary receives any Net Asset
Sale Proceeds (as defined in the Exchange Agreement) in excess of $250,000 (or
if a Default or an Event of Default shall then exist, regardless of amount),
which in each such case does not result in a Change of Control, then the Issuer
shall, within one Business Day (or cause its Subsidiary receiving such proceeds
to pay) to the holders as a prepayment of the Notes the lesser of (a) the amount
of such Net Asset Sale Proceeds and (b) the Aggregate Prepayment Amount
(excluding any portion of such Net Asset Sale Proceeds which so long as no
Default or Event of Default exists, (x) in the case of proceeds of business
interruption insurance, is used in the ordinary course of the Issuer's and its
Subsidiaries' business and (y) in the case of proceeds of casualty insurance, is
applied for the purpose of replacing, repairing, restoring or rebuilding the
relevant tangible property).

Upon due presentment for registration of transfer of this Note at the office or
agency of the Issuer maintained for that purpose in accordance with the terms of
the Fiscal Agency Agreement, a new Note or Notes of authorized denominations for
an equal aggregate principal amount will be issued to the transferee in exchange
thereof; subject to the limitations provided in the Exchange Agreement and the
Fiscal Agency Agreement, without charge except for any tax, assessment or other
governmental charge imposed in connection therewith.

The Issuer, the Fiscal Agent, any authenticating agent, any paying agent and any
Note registrar may deem and treat the registered holder hereof as the absolute
owner of this Note (whether or not this Note shall be overdue and
notwithstanding any notation of ownership or other writing hereon made by anyone
other than the Issuer or any Note registrar) for the purpose of receiving
payment hereof, or on account hereof, for the conversion hereof and for all
other purposes, and neither the Issuer nor the Fiscal Agent nor any other
authenticating agent nor any paying agent nor other conversion agent nor any
Note registrar shall be affected by any notice to the contrary. All payments
made to or upon the order of such registered holder shall, to the extent of the
sum or sums paid, satisfy and discharge liability for monies payable on this
Note.

No recourse for the payment of the principal of or any premium or interest on
this Note, or for any claim based hereon or otherwise in respect hereof, and no
recourse under or upon any obligation, covenant or agreement of the Issuer in
the Exchange Agreement or any supplemental

                                      A-8
<Page>

exchange agreement or in any Note, or because of the creation of any
indebtedness represented thereby, shall be had against any incorporator,
stockholder, employee, agent, officer or director or subsidiary, as such, past,
present or future, of the Issuer or of any successor corporation, either
directly or through the Issuer or any successor corporation, whether by virtue
of any constitution, statute or rule of law or by the enforcement of any
assessment or penalty or otherwise, all such liability being, by acceptance
hereof and as part of the consideration for the issue hereof, expressly waived
and released.

This Note shall be deemed to be a contract made under the laws of The
Commonwealth of Massachusetts, and for all purposes shall be construed in
accordance with the laws of The Commonwealth of Massachusetts, without regard to
principles of conflicts of laws. Terms used in this Note and defined in the
Exchange Agreement are used herein as therein defined.

                                      A-9
<Page>

                                 ABBREVIATIONS

The following abbreviations, when used in the inscription of the face of this
Note, shall be construed as though they were written out in full according to
applicable laws or regulations.

          TEN COM - as tenants in common
          TEN ENT - as tenant by the entireties
          JT TEN - as joint tenants with right of survivorship and not as
          tenants in common
          UNIF GIFT MIN ACT - ____________ Custodian _____________
                               (Cust)                   (Minor)

          under Uniform Gifts to Minors Act

          --------------------------------------------
                          (State)
Additional abbreviations may also be used though not in the above list.

                                      A-10
<Page>

                                   ASSIGNMENT
FOR VALUE RECEIVED the undersigned hereby sell(s), assign(s) and transfer(s)
unto

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

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

PLEASE INSERT SOCIAL SECURITY OR
OTHER IDENTIFYING NUMBER OF ASSIGNEE

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

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

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

----------------------------------------------------
    (Please print or typewrite name and address
    including postal zip code of assignee)

----------------------------------------------------
the within Note and all rights thereunder, and hereby irrevocably constitutes
and appoints

----------------------------------------------------
Attorney to transfer said Note on the books of the Issuer, with full power of
substitution in the premises.

In connection with any transfer of the Note (other than any transfer pursuant to
a registration statement that has been declared effective under the Securities
Act), the undersigned confirms that such Note is being transferred:

     / /  To iBasis, Inc. or a subsidiary thereof; or
     / /  Pursuant to and in compliance with Rule 144A under the Securities Act
of 1933, as amended; and unless the box below is checked, the undersigned
confirms that such Note is not being transferred to an "affiliate" of the Issuer
as defined in Rule 144 under the Securities Act of 1933, as amended (an
"Affiliate").

/ /  The transferee is an Affiliate of the Issuer.

Dated:
      ------------------------                  --------------------------------

                                                --------------------------------
                                                       Signature(s)

                                      A-11
<Page>

                                                Signature(s) must be guaranteed
                                                by an "eligible guarantor
                                                institution" meeting the
                                                requirements of the Note
                                                registrar, which requirements
                                                include membership or
                                                participation in the Security
                                                Transfer Agent Medallion Program
                                                ("STAMP") or such other
                                                "signature guarantee program" as
                                                may be determined by the Note
                                                registrar in addition to, or in
                                                substitution for, STAMP, all in
                                                accordance with the Securities
                                                Exchange Act of 1934, as
                                                amended.

                                                -------------------------------
                                                Signature Guarantee
NOTICE: The signature of the assignment must correspond with the name as written
upon the face of the Note in every particular without alteration or enlargement
or any change whatever.

                                      A-12
<Page>

                                   ASSIGNMENT

Social Security or taxpayer I.D. or other identifying number of assignee:

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

     FOR VALUE RECEIVED, the undersigned hereby sells, assigns and transfers
unto:

------------------------------------------------------------------------------
                         (name and address of assignee)

the within Senior Note and all rights thereunder, and hereby irrevocably
constitutes and appoints _________________, attorney, to transfer said Senior
Note on the books kept for registration thereof, with full power of substitution
in the premises.

Dated:                                                                        */
     ------------------------                   ------------------------------
                                                Signature Guaranteed

                                                                              */
                                                ------------------------------
----------
*/ NOTICE: The signature to this assignment must correspond with the name of the
registered owner as it appears on the face of the within Senior Note in every
particular, without alteration, enlargement or any change whatever.

                                      A-13
<Page>

                                                                       EXHIBIT B

                     FORM OF INVESTOR REPRESENTATION LETTER

                        FORM OF INVESTOR REPRESENTATION

     This certificate is delivered to U.S. Bank National Association in
connection with the sale today by [NAME OF TRANSFEROR] (the "Transferor") of
[AMOUNT] of 11.5% Senior Secured Notes, CUSIP No: 450732 AB 8, (the "Notes")
issued by iBasis, Inc. and iBasis Global, Inc. (the "Sale") to the undersigned
(the "Investor"). The Investor hereby represents and warrants that it has full
power and authority to execute and deliver this certificate and hereby
represents and warrants that:

1.   Such Investor understands that the Sale has not been registered under the
Securities Act of 1933, as amended (the "Act"), or the securities laws of any
state, and its Notes may not be transferred, resold or otherwise disposed of,
except pursuant to an effective registration statement under the Act or pursuant
to an exemption from the registration requirements of the Act.

2.   Such Investor is acquiring its Notes for its own account only and not with
a view to distribution of such Notes, in whole or in part, in violation of the
Act or the securities laws of any state.

3.   Such Investor is a "qualified institutional buyer" as such term is defined
in Rule 144A under the Act, and has such knowledge and experience in financial
and business matters that it is capable of evaluating the merits and risks of
the acquisition of its respective Notes and having had access to, or having been
furnished with, all information as it has considered necessary, has concluded
that it is able to bear those risks.

4.   Such Investor acknowledges that so long as appropriate its respective Notes
will bear a legend relating to restrictions on transfer except in compliance
with the Act.

     IN WITNESS WHEREOF, the undersigned has executed this certificate as of the
___ day of ______ 200_.

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

                                                Title:

                                                For:

                                       B-1

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