<PAGE>

                                                                    Exhibit 1.01
                                                                    ------------
                              __________ Shares/1/



                                 DSL.net, Inc.

                                  Common Stock

                             UNDERWRITING AGREEMENT
                             ----------------------

                                                                __________, 1999


DEUTSCHE BANK SECURITIES INC.
DONALDSON, LUFKIN & JENRETTE
SECURITIES CORPORATION
LEHMAN BROTHERS INC.
DLJdirect Inc.
As representatives of the several Underwriters
 named in Schedule I hereto
 c/o Deutsche Bank Securities Inc.
 One South Street
 Baltimore, Maryland 21202

Dear Sirs:

     DSL.net, Inc., a Delaware corporation (the "COMPANY"), proposes to issue
and sell ____________ shares of its common stock, $.0005 par value per share
(the "FIRM SHARES"), to the several underwriters named in Schedule I hereto (the
"UNDERWRITERS").  The Company also proposes to issue and sell to the several
Underwriters not more than an additional _______ shares of its common stock,
$.0005 par value per share (the "ADDITIONAL SHARES"), if requested by the
Underwriters as provided in Section 2 hereof.  The Firm Shares and the
Additional Shares are hereinafter referred to collectively as the "SHARES". The
shares of common stock of the Company to be outstanding after giving effect to
the sales contemplated hereby are hereinafter referred to as the "COMMON STOCK".

     SECTION 1.  Registration Statement and Prospectus.  The Company has
prepared and filed with the Securities and Exchange Commission (the
"COMMISSION") in accordance with the provisions of the Securities Act of 1933,
as amended, and the rules and regulations of the Commission thereunder
(collectively, the "ACT"), a registration statement on Form S-1, including a
prospectus, relating to the Shares. The registration statement, as amended at
the time it became effective, including the information (if any) deemed to be
part of the registration statement at the time of effectiveness pursuant to Rule
430A under the Act, is hereinafter referred to as the "REGISTRATION STATEMENT";
and the prospectus in the form first used to confirm sales of Shares is
hereinafter referred to as the "PROSPECTUS". If the Company has filed or is
required pursuant to the terms hereof to file a registration statement pursuant
to Rule 462(b)

-----------------
/1/ Insert number of shares to be sold (not including green shoe).
<PAGE>

under the Act registering additional shares of Common Stock (a "RULE
462(b) REGISTRATION STATEMENT"), then, unless otherwise specified, any reference
herein to the term "Registration Statement" shall be deemed to include such Rule
462(b) Registration Statement.

     SECTION 2. Agreements to Sell and Purchase and Lock-Up Agreements. On the
basis of the representations and warranties contained in this Agreement, and
subject to its terms and conditions, the Company agrees to issue and sell, and
each Underwriter agrees, severally and not jointly, to purchase from the Company
at a price per Share of $______ (the "PURCHASE PRICE") the number of Firm Shares
set forth opposite the name of such Underwriter in Schedule I hereto.

     On the basis of the representations and warranties contained in this
Agreement, and subject to its terms and conditions, the Company agrees to issue
and sell the Additional Shares and the Underwriters shall have the right to
purchase, severally and not jointly, up to _______ Additional Shares from the
Company at the Purchase Price.  Additional Shares may be purchased solely for
the purpose of covering over-allotments made in connection with the offering of
the Firm Shares.  The Underwriters may exercise their right to purchase
Additional Shares in whole or in part from time to time by giving written notice
thereof to the Company within 30 days after the date of this Agreement.  You
shall give any such notice on behalf of the Underwriters and such notice shall
specify the aggregate number of Additional Shares to be purchased pursuant to
such exercise and the date for payment and delivery thereof, which date shall be
a business day (i) no earlier than two business days after such notice has been
given (and, in any event, no earlier than the Closing Date (as hereinafter
defined)) and (ii) no later than ten business days after such notice has been
given.  If any Additional Shares are to be purchased, each Underwriter,
severally and not jointly, agrees to purchase from the Company the number of
Additional Shares (subject to such adjustments to eliminate fractional shares as
you may determine) which bears the same proportion to the total number of
Additional Shares to be purchased from the Company as the number of Firm Shares
set forth opposite the name of such Underwriter in Schedule I bears to the total
number of Firm Shares.

     The Company hereby agrees not to (i) offer, pledge, sell, contract to sell,
sell any option or contract to purchase, purchase any option or contract to
sell, grant any option, right or warrant to purchase, or otherwise transfer or
dispose of, directly or indirectly, any shares of Common Stock or any securities
convertible into or exercisable or exchangeable for Common Stock or (ii) enter
into any swap or other arrangement that transfers all or a portion of the
economic consequences associated with the ownership of any Common Stock
(regardless of whether any of the transactions described in clause (i) or (ii)
is to be settled by the delivery of Common Stock, or such other securities, in
cash or otherwise), except to the Underwriters pursuant to this Agreement, for a
period of 180 days after the date of the Prospectus without the prior written
consent of Deutsche Bank Securities Inc. Notwithstanding the foregoing, during
such  period (i) the Company may grant stock options pursuant to the Company's
existing stock option plan and employee stock purchase plan, (ii) the Company
may issue shares of Common Stock upon the exercise of an option or warrant or
the conversion of a security outstanding on the date hereof granted or issued
under the Company's existing stock option plan or employee stock purchase plan,
and (iii) the Company may issue shares of Common Stock and other securities
convertible into or exercisable or exchangeable for shares of Common Stock in
connection with acquisitions (including asset acquisitions) and strategic
partner relationships, provided that, each holder of such Common Stock or such
other securities shall, prior to or concurrently with the issuance of

                                       2
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such Common Stock or other securities, agree in writing to be bound by
restrictions set forth in the agreements described in the last sentence of this
paragraph. The Company also agrees not to file any registration statement (other
than a registration statement on Form S-8 registering Common Stock issuable
under the Company's existing stock option plan and employee stock purchase plan)
with respect to any shares of Common Stock or any securities convertible into or
exercisable or exchangeable for Common Stock for a period of 180 days after the
date of the Prospectus without the prior written consent of Deutsche Bank
Securities Inc. The Company shall, prior to or concurrently with the execution
of this Agreement, deliver an agreement executed by (i) each of the directors
and officers of the Company and (ii) each stockholder of the Company (other than
those listed on Annex I hereto), to the effect that such person will not, except
as provided therein, during the period commencing on the date such person signs
such agreement and ending 180 days after the date of the Prospectus, without the
prior written consent of Deutsche Bank Securities Inc., (A) engage in any of the
transactions described in the first sentence of this paragraph or (B) make any
demand for, or exercise any right with respect to, the registration of any
shares of Common Stock or any securities convertible into or exercisable or
exchangeable for Common Stock.

     SECTION 3. Terms of Public Offering. The Company is advised by you that the
Underwriters propose (i) to make a public offering of their respective portions
of the Shares as soon after the execution and delivery of this Agreement as in
your judgment is advisable and (ii) initially to offer the Shares upon the terms
set forth in the Prospectus.

     SECTION 4. Delivery and Payment. The Shares shall be represented by
definitive certificates and shall be issued in such authorized denominations and
registered in such names as Deutsche Bank Securities Inc. shall request no later
than two business days prior to the Closing Date or the applicable Option
Closing Date (as defined below), as the case may be.  The Company shall deliver
the Shares, with any transfer taxes thereon duly paid by the Company, to
Deutsche Bank Securities Inc. through the facilities of The Depository Trust
Company ("DTC"), for the respective accounts of the several Underwriters,
against payment to the Company of the Purchase Price therefor by wire transfer
of Federal or other funds immediately available in New York City.  The
certificates representing the Shares shall be made available for inspection not
later than 9:30 A.M., New York City time, on the business day prior to the
Closing Date or the applicable Option Closing Date, as the case may be, at the
office of DTC or its designated custodian (the "DESIGNATED OFFICE").  The time
and date of delivery and payment for the Firm Shares shall be 9:00 a.m., New
York City time, on ________, 1999 or such other time on the same or such other
date as Deutsche Bank Securities Inc. and the Company shall agree in writing.
The time and date of delivery for the Firm Shares are hereinafter referred to as
the  "CLOSING DATE".  The time and date of delivery and payment for any
Additional Shares to be purchased by the Underwriters shall be 9:00 a.m., New
York City time, on the date specified in the applicable exercise notice given by
you pursuant to Section 2 or such other time on the same or such other date as
Deutsche Bank Securities Inc. and the Company shall agree in writing.  The time
and date of delivery for any Additional Shares are hereinafter referred to as an
"OPTION CLOSING DATE".

     The documents to be delivered on the Closing Date or any Option Closing
Date on behalf of the parties hereto pursuant to Section 8 of this Agreement
shall be delivered at the offices of Brobeck, Phleger & Harrison LLP, 1633
Broadway, New York, New York  10019 and the Shares shall be delivered at the
Designated Office, all on the Closing Date or such Option Closing Date, as the
case may be.

                                       3
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     SECTION 5.  Agreements of the Company.  The Company agrees with you:

     (a)  To advise you promptly and, if requested by you, to confirm such
advice in writing, (i) of any request by the Commission for amendments to the
Registration Statement or amendments or supplements to the Prospectus or for
additional information, (ii) of the issuance by the Commission of any stop order
suspending the effectiveness of the Registration Statement or of the suspension
of qualification of the Shares for offering or sale in any jurisdiction, or the
initiation of any proceeding for such purposes, (iii) when any amendment to the
Registration Statement becomes effective, (iv) if the Company is required to
file a Rule 462(b) Registration Statement after the effectiveness of this
Agreement, when the Rule 462(b) Registration Statement has become effective and
(v) of the happening of any event during the period referred to in Section 5(d)
below which makes any statement of a material fact made in the Registration
Statement or the Prospectus untrue or which requires any additions to or changes
in the Registration Statement or the Prospectus in order to make the statements
therein not misleading. If at any time the Commission shall issue any stop order
suspending the effectiveness of the Registration Statement, the Company will use
its best efforts to obtain the withdrawal or lifting of such order at the
earliest possible time.

     (b)  To furnish to you three (3) signed copies of the Registration
Statement as first filed with the Commission and of each amendment to it,
including all exhibits, and to furnish to you and each Underwriter designated by
you such number of conformed copies of the Registration Statement as so filed
and of each amendment to it, without exhibits, as you may reasonably request.

     (c)  To prepare the Prospectus, the form and substance of which shall be
satisfactory to you, and to file the Prospectus in such form with the Commission
within the applicable period specified in Rule 424(b) under the Act; during the
period specified in Section 5(d) below, not to file any further amendment to the
Registration Statement and not to make any amendment or supplement to the
Prospectus of which you shall not previously have been advised or to which you
shall reasonably object after being so advised; and, during such period, to
prepare and file with the Commission, promptly upon your reasonable request, any
amendment to the Registration Statement or amendment or supplement to the
Prospectus which may be necessary or advisable in connection with the
distribution of the Shares by you, and to use its best efforts to cause any such
amendment to the Registration Statement to become promptly effective.

     (d)  Prior to 10:00 A.M., New York City time, on the first business day
after the date of this Agreement and from time to time thereafter for such
period as in the opinion of counsel for the Underwriters a prospectus is
required by law to be delivered in connection with sales by an Underwriter or a
dealer, to furnish in New York City to each Underwriter and any dealer as many
copies of the Prospectus (and of any amendment or supplement to the Prospectus)
as such Underwriter or dealer may reasonably request.

                                       4
<PAGE>

     (e)  If during the period specified in Section 5(d), any event shall
occur or condition shall exist as a result of which, in the opinion of counsel
for the Underwriters, it becomes necessary to amend or supplement the Prospectus
in order to make the statements therein, in the light of the circumstances when
the Prospectus is delivered to a purchaser, not misleading, or if, in the
opinion of counsel for the Underwriters, it is necessary to amend or supplement
the Prospectus to comply with applicable law, forthwith to prepare and file with
the Commission an appropriate amendment or supplement to the Prospectus so that
the statements in the Prospectus, as so amended or supplemented, will not in the
light of the circumstances when it is so delivered, be misleading, or so that
the Prospectus will comply with applicable law, and to furnish to each
Underwriter and to any dealer as many copies thereof as such Underwriter or
dealer may reasonably request.

     (f)  Prior to any public offering of the Shares, to cooperate with you and
counsel for the Underwriters in connection with the registration or
qualification of the Shares for offer and sale by the several Underwriters and
by dealers under the state securities or Blue Sky laws of such jurisdictions as
you may request, to continue such registration or qualification in effect so
long as required for distribution of the Shares and to file such consents to
service of process or other documents as may be necessary in order to effect
such registration or qualification; provided, however, that the Company shall
not be required in connection therewith to qualify as a foreign corporation in
any jurisdiction in which it is not now so qualified or to take any action that
would subject it to general consent to service of process or taxation other than
as to matters and transactions relating to the Prospectus, the Registration
Statement, any preliminary prospectus or the offering or sale of the Shares, in
any jurisdiction in which it is not now so subject.

     (g)  To mail and make generally available to its stockholders as soon as
practicable an earnings statement covering a period of at least twelve months
beginning after the effective date of the Registration Statement that shall
satisfy the provisions of Section 11(a) of the Act, and to advise you in writing
when such statement has been so made available.

     (h)  During the period of three years after the date of this Agreement, to
furnish to you as soon as available copies of all reports or other
communications furnished to the record holders of Common Stock or furnished to
or filed with the Commission or any national securities exchange on which any
class of securities of the Company is listed and such other publicly available
information concerning the Company and its subsidiaries as you may reasonably
request.

     (i)  Whether or not the transactions contemplated in this Agreement are
consummated or this Agreement is terminated, to pay or cause to be paid all
expenses incident to the performance of its obligations under this Agreement,
including: (i) the fees, disbursements and expenses of the Company's counsel and
the Company's accountants in connection with the registration and delivery of
the Shares under the Act and all other fees and expenses (subject to the
provisions of clauses (iv) and (v) below, other than the fees and expenses of
counsel to the Underwriters) in connection with the preparation, printing,
filing and distribution of the Registration Statement (including financial
statements and exhibits), any preliminary prospectus, the Prospectus and all
amendments and supplements to any of the foregoing, including the mailing and
delivering of copies thereof to the Underwriters and dealers in the quantities
specified herein during the period specified in Section 5(d) hereof, (ii) all
costs and expenses related to the transfer and delivery of the Shares to the
Underwriters, including any transfer or other taxes payable thereon, (iii) all
costs of printing or producing this Agreement and any other agreements or
documents in connection with the offering, purchase, sale or delivery of the
Shares, (iv) all expenses in

                                       5
<PAGE>

connection with the registration or qualification of the Shares for offer and
sale under the securities or Blue Sky laws of the several states and all costs
of printing or producing any Preliminary and Supplemental Blue Sky Memoranda in
connection therewith (including the filing fees and reasonable fees and
disbursements of counsel for the Underwriters in connection with such
registration or qualification and memoranda relating thereto, (which shall not
exceed $10,000), (v) the filing fees and reasonable fees and disbursements of
counsel for the Underwriters in connection with the review and clearance of the
offering of the Shares by the National Association of Securities Dealers, Inc.,
(vi) all fees and expenses in connection with the preparation and filing of the
registration statement on Form 8-A relating to the Common Stock and all costs
and expenses incident to the listing of the Shares on the Nasdaq National
Market, (vii) the cost of printing certificates representing the Shares, (viii)
the costs and charges of any transfer agent, registrar and/or depositary, and
(ix) all other costs and expenses incident to the performance of the obligations
of the Company hereunder for which provision is not otherwise made in this
Section.

     (j)  To use its best efforts to list for quotation the Shares on the Nasdaq
National Market and to maintain the listing of the Shares on the Nasdaq National
Market for a period of three years after the date of this Agreement.

     (k)  To use its best efforts to do and perform all things required or
necessary to be done and performed under this Agreement by the Company prior to
the Closing Date or any Option Closing Date, as the case may be, and to satisfy
all conditions precedent to the delivery of the Shares.

     (l)  If the Registration Statement at the time of the effectiveness of this
Agreement does not cover all of the Shares, to file a Rule 462(b) Registration
Statement with the Commission registering the Shares not so covered in
compliance with Rule 462(b) by 10:00 P.M., New York City time, on the date of
this Agreement and to pay to the Commission the filing fee for such Rule 462(b)
Registration Statement at the time of the filing thereof or to give irrevocable
instructions for the payment of such fee pursuant to Rule 111(b) under the Act.

     SECTION 6. Representations and Warranties of the Company.  The Company
represents and warrants to each Underwriter that:

     (a)  The Registration Statement has become effective (other than any Rule
462(b) Registration Statement to be filed by the Company after the effectiveness
of this Agreement); any Rule 462(b) Registration Statement filed after the
effectiveness of this Agreement will become effective no later than 10:00 P.M.,
New York City time, on the date of this Agreement; and no stop order suspending
the effectiveness of the Registration Statement is in effect, and no proceedings
for such purpose are pending before or, to the Company's knowledge, threatened
by the Commission.

     (b)  (i) The Registration Statement (other than any Rule 462(b)
Registration Statement to be filed by the Company after the effectiveness of
this Agreement), when it became effective, did not contain and, as amended, if
applicable, will not contain any untrue statement of a material fact or omit to
state a material fact required to be stated therein or necessary to make the
statements therein not misleading, (ii) the Registration Statement (other than
any Rule 462(b)

                                       6
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Registration Statement to be filed by the Company after the effectiveness of
this Agreement) and the Prospectus comply and, as amended or supplemented, if
applicable, will comply in all material respects with the Act, (iii) if the
Company is required to file a Rule 462(b) Registration Statement after the
effectiveness of this Agreement, such Rule 462(b) Registration Statement and any
amendments thereto, when they become effective (A) will not contain any untrue
statement of a material fact or omit to state a material fact required to be
stated therein or necessary to make the statements therein not misleading and
(B) will comply in all material respects with the Act and (iv) the Prospectus
does not contain and, as amended or supplemented, if applicable, will not
contain any untrue statement of a material fact or omit to state a material fact
necessary to make the statements therein, in the light of the circumstances
under which they were made, not misleading, except that the representations and
warranties set forth in this paragraph do not apply to statements or omissions
in the Registration Statement or the Prospectus based upon information relating
to any Underwriter furnished to the Company in writing by such Underwriter
through you expressly for use therein.

     (c)  Each preliminary prospectus filed as part of the registration
statement as originally filed or as part of any amendment thereto, or filed
pursuant to Rule 424 under the Act, complied when so filed in all material
respects with the Act, and did not contain an untrue statement of a material
fact or omit to state a material fact required to be stated therein or necessary
to make the statements therein, in the light of the circumstances under which
they were made, not misleading, except that the representations and warranties
set forth in this paragraph do not apply to any material misstatement or
omission or alleged material misstatement or omission that was cured in any
subsequently filed preliminary prospectus or the Prospectus, as amended or
supplemented, or statements or omissions in any preliminary prospectus based
upon information relating to any Underwriter furnished to the Company in writing
by such Underwriter through you expressly for use therein.

     (d)  Each of the Company and its subsidiaries has been duly incorporated or
formed, as applicable, is validly existing as a corporation or limited liability
company, as applicable, in good standing under the laws of its jurisdiction of
incorporation or formation and has the corporate power or limited liability
company power and authority to carry on its business as described in the
Prospectus and to own, lease and operate its properties, and each is duly
qualified and is in good standing as a foreign corporation or limited liability
company, as applicable, authorized to do business in each jurisdiction in which
the nature of its business or its ownership or leasing of property requires such
qualification, except where the failure to be so qualified would not have a
material adverse effect on the business, prospects, financial condition or
results of operations of the Company and its subsidiaries, taken as a whole.

     (e)  There are no outstanding subscriptions, rights, warrants, options,
calls, convertible securities, commitments of sale or liens granted or issued by
the Company or any of its subsidiaries relating to or entitling any person to
purchase or otherwise to acquire any shares of the capital stock of the Company
or any of its subsidiaries, except as otherwise disclosed in the Registration
Statement.

     (f)  All the outstanding shares of capital stock of the Company have been
duly authorized and validly issued and are fully paid and non-assessable; and
the Shares have been duly authorized and, when issued and delivered to the
Underwriters against payment therefor as provided by this Agreement, will be
validly issued, fully paid and non-assessable, and the issuance of such Shares
will not be subject to any preemptive or similar rights.

                                       7
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     (g)  All of the outstanding shares of capital stock or limited liability
company interests, as applicable, of each of the Company's subsidiaries have
been duly authorized and validly issued and are fully paid and non-assessable,
and are owned by the Company, directly or indirectly through one or more
subsidiaries, free and clear of any security interest, claim, lien, encumbrance
or adverse interest of any nature.

     (h)  The authorized capital stock of the Company conforms as to legal
matters to the description thereof contained in the Prospectus.

     (i)  Neither the Company nor any of its subsidiaries is in violation of its
respective charter or limited liability company agreement, as applicable, or by-
laws or in default in the performance of any obligation, agreement, covenant or
condition contained in any indenture, loan agreement, mortgage, lease or other
agreement or instrument that is material to the Company and its subsidiaries,
taken as a whole, to which the Company or any of its subsidiaries is a party or
by which the Company or any of its subsidiaries or their respective property is
bound.

     (j)  The execution, delivery and performance of this Agreement by the
Company, the compliance by the Company with all the provisions hereof and the
consummation of the transactions contemplated hereby will not (i) require any
consent, approval, authorization or other order of, or qualification with, any
court or governmental body or agency (except such as may be required under the
Act, the Securities Exchange Act of 1934 and the securities or Blue Sky laws of
the various states), (ii) conflict with or constitute a breach of any of the
terms or provisions of, or a default under, the charter or limited liability
company agreement, as applicable or by-laws of the Company or any of its
subsidiaries or any indenture, loan agreement, mortgage, lease or other
agreement or instrument that is material to the Company and its subsidiaries,
taken as a whole, to which the Company or any of its subsidiaries is a party or
by which the Company or any of its subsidiaries or their respective property is
bound, (iii) violate or conflict with any applicable law or any rule,
regulation, judgment, order or decree of any court or any governmental body or
agency having jurisdiction over the Company, any of its subsidiaries or their
respective property or (iv) result in the suspension, termination or revocation
of any Authorization (as defined below) of the Company or any of its
subsidiaries or any other impairment of the rights of the holder of any such
Authorization.

     (k)  There are no legal or governmental proceedings pending or, to the
Company's knowledge, threatened to which the Company or any of its subsidiaries
is or, to the Company's knowledge, could be a party or to which any of their
respective property is or, to the Company's knowledge, could be subject that are
required to be described in the Registration Statement or the Prospectus and are
not so described; nor are there any statutes, regulations, contracts or other
documents that are required to be described in the Registration Statement or the
Prospectus or to be filed as exhibits to the Registration Statement that are not
so described or filed as required.

     (l)  Neither the Company nor any of its subsidiaries has violated any
foreign, federal, state or local law or regulation relating to the protection of
human health and safety, the environment or hazardous or toxic substances or
wastes, pollutants or contaminants

                                       8
<PAGE>

("ENVIRONMENTAL LAWS"), any provisions of the Employee Retirement Income
Security Act of 1974, as amended, or any provisions of the Foreign Corrupt
Practices Act, or the rules and regulations promulgated thereunder, except for
such violations which, singly or in the aggregate, would not have a material
adverse effect on the business, prospects, financial condition or results of
operation of the Company and its subsidiaries, taken as a whole.

     (m)  Each of the Company and its subsidiaries has such permits, licenses,
consents, exemptions, franchises, authorizations and other approvals (each, an
"AUTHORIZATION") of, and has made all filings with and notices to, all
governmental or regulatory authorities and self-regulatory organizations and all
courts and other tribunals, including, without limitation, under any applicable
Environmental Laws, as are necessary to own, lease, license and operate its
respective properties and to conduct its business, except where the failure to
have any such Authorization or to make any such filing or notice would not,
singly or in the aggregate, have a material adverse effect on the business,
prospects, financial condition or results of operations of the Company and its
subsidiaries, taken as a whole. Each such Authorization is valid and in full
force and effect and each of the Company and its subsidiaries is in compliance
with all the terms and conditions thereof and with the rules and regulations of
the authorities and governing bodies having jurisdiction with respect thereto;
and no event has occurred (including, without limitation, the receipt of any
notice from any authority or governing body) which allows or, after notice or
lapse of time or both, would allow, revocation, suspension or termination of any
such Authorization or results or, after notice or lapse of time or both, would
result in any other impairment of the rights of the holder of any such
Authorization; and such Authorizations contain no restrictions that are
burdensome to the Company or any of its subsidiaries; except as is disclosed in
the Registration Statement or where such failure to be valid and in full force
and effect or to be in compliance, the occurrence of any such event or the
presence of any such restriction would not, singly or in the aggregate, have a
material adverse effect on the business, prospects, financial condition or
results of operations of the Company and its subsidiaries, taken as a whole.

     (n)  There are no costs or liabilities associated with Environmental Laws
(including, without limitation, any capital or operating expenditures required
for clean-up, closure of properties or compliance with Environmental Laws or any
Authorization, any related constraints on operating activities and any potential
liabilities to third parties) which would, singly or in the aggregate, have a
material adverse effect on the business, prospects, financial condition or
results of operations of the Company and its subsidiaries, taken as a whole.

     (o)  This Agreement has been duly authorized, executed and delivered by the
Company.

     (p)  PricewaterhouseCoopers LLP are independent public accountants with
respect to the Company and its subsidiaries as required by the Act.

     (q)  The consolidated financial statements included in the Registration
Statement and the Prospectus (and any amendment or supplement thereto), together
with related schedules and notes, present fairly the consolidated financial
position, results of operations and changes in financial position of the Company
and its subsidiaries on the basis stated therein at the respective dates or for
the respective periods to which they apply; such statements and related
schedules and notes have been prepared in accordance with generally accepted
accounting principles

                                       9
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consistently applied throughout the periods involved, except as disclosed
therein; the supporting schedules, if any, included in the Registration
Statement present fairly in accordance with generally accepted accounting
principles the information required to be stated therein; and the other
financial and statistical information and data set forth in the Registration
Statement and the Prospectus (and any amendment or supplement thereto) are, in
all material respects, accurately presented and prepared on a basis consistent
with such financial statements and the books and records of the Company.

     (r)  The Company is not and, after giving effect to the offering and sale
of the Shares and the application of the proceeds thereof as described in the
Prospectus, will not be, an "investment company" as such term is defined in the
Investment Company Act of 1940, as amended.

     (s)  Except as disclosed in the Registration Statement, there are no
contracts, agreements or understandings between the Company and any person
granting such person the right to require the Company to file a registration
statement under the Act with respect to any securities of the Company or to
require the Company to include such securities with the Shares registered
pursuant to the Registration Statement.

     (t)  Since the respective dates as of which information is given in the
Prospectus other than as set forth in the Prospectus (exclusive of any
amendments or supplements thereto subsequent to the date of this Agreement), (i)
there has not occurred any material adverse change or any development involving
a prospective material adverse change in the condition, financial or otherwise,
or the earnings, business, management or operations of the Company and its
subsidiaries, taken as a whole, (ii) there has not been any material adverse
change or any development involving a prospective material adverse change in the
capital stock or in the long-term debt of the Company or any of its subsidiaries
and (iii) neither the Company nor any of its subsidiaries has incurred any
material liability or obligation, direct or contingent.

     (u)  Each certificate signed by any officer of the Company and delivered
to the Underwriters or counsel for the Underwriters shall be deemed to be a
representation and warranty by the Company to the Underwriters as to the matters
covered thereby.

     (v)  Neither the Company nor any of its subsidiaries owns any real
property. The Company and its Subsidiaries have good and marketable title to all
personal property owned by them which is material to the business of the Company
and its subsidiaries, taken as a whole, in each case free and clear of all
liens, encumbrances and defects except such as are described in the Prospectus
or such as do not materially affect the value of such property and do not
materially interfere with the use made and proposed to be made of such property
by the Company and its subsidiaries; and any real property and buildings held
under lease by the Company and its subsidiaries are held by them under valid,
subsisting and enforceable leases with such exceptions as are not material and
do not materially interfere with the use made and proposed to be made of such
property and buildings by the Company and its subsidiaries, taken as a whole, in
each case except as described in the Prospectus.

                                       10
<PAGE>

     (w)  The Company and its subsidiaries own, or possess valid and enforceable
licenses to, or rights to use, all patents, patent rights, inventions,
copyrights, know-how (including trade secrets and other unpatented and/or
unpatentable proprietary or confidential information, systems or procedures),
trademarks, service marks and trade names ("INTELLECTUAL PROPERTY") currently
employed by the Company and its subsidiaries in connection with the business now
operated by them, except where the failure to own or possess licenses for or
rights to use such Intellectual Property would not, singly or in the aggregate,
have a material adverse effect on the business, prospects, financial condition
or results of operation of the Company and its subsidiaries, taken as a whole.
Neither the Company, nor its subsidiaries, has received any written notice, nor
are they aware of facts which would form a reasonable basis for any such claim,
that: (i) challenges the Company's or its subsidiaries' rights in or to any
Intellectual Property; (ii) challenges the validity or scope of any Intellectual
Property; (iii) any third party has or will be able to establish any rights in
the Intellectual Property, except for the ownership rights of the owners of the
Intellectual Property which is licensed to the Company or the rights of parties
to whom the Company has granted licenses of such Intellectual Property; (iv) the
Intellectual Property infringes or otherwise violates any patent, copyright,
trade secret, trademark or other proprietary right of any third party; or (v)
there is infringement of the Intellectual Property by any third party, which, in
the case of any such claim specified in clauses (i), (ii), (iii), (iv) or (v)
above, singly or in the aggregate, if the subject of an unfavorable decision,
ruling or finding, would have a material adverse effect on the business,
prospects, financial condition or results of operations of the Company and its
subsidiaries, taken as a whole, except that the Company has received notice from
the United States Patent and Trademark Office that its registration of the
trademark "DSL.net" may be removed from the list of supplemental registrations
under certain circumstances.

     (x)  The Company and each of its subsidiaries are insured by insurers of
recognized financial responsibility against such losses and risks and in such
amounts as are prudent and customary in the businesses in which they are
engaged; and neither the Company nor any of its subsidiaries (i) has received
written notice from any insurer or agent of such insurer that substantial
capital improvements or other material expenditures will have to be made in
order to continue such insurance or (ii) has any reason to believe that it will
not be able to renew its existing insurance coverage as and when such coverage
expires or to obtain similar coverage from similar insurers at a cost that would
not have a material adverse effect on the business, prospects, financial
conditions or results of operations of the Company and its subsidiaries, taken
as a whole.

     (y)  No relationship, direct or indirect, exists between or among the
Company or any of its subsidiaries on the one hand, and the directors, officers,
shareholders, customers or suppliers of the Company or any of its subsidiaries
on the other hand, which is required by the Act to be described in the
Registration Statement or the Prospectus which is not so described.

     (z)  There is no (i) significant unfair labor practice complaint,
grievance or arbitration proceeding pending or, to the Company's knowledge,
threatened against the Company or any of its subsidiaries before the National
Labor Relations Board or any state or local labor relations board, (ii) strike,
labor dispute, slowdown or stoppage pending or, to the Company's knowledge,
threatened against the Company or any of its subsidiaries or (iii) union
representation question existing with respect to the employees of the Company
and its subsidiaries, except for such actions specified in clause (i), (ii) or
(iii) above, which, singly or in the aggregate, would not have a material
adverse effect on the business, prospects, financial condition or results of
operations of the Company and its subsidiaries, taken as a whole. To the
Company's knowledge, no collective bargaining organizing activities are taking
place with respect to the Company or any of its subsidiaries.

                                       11
<PAGE>

     (aa) The Company and each of its subsidiaries maintains a system of
internal accounting controls sufficient to provide reasonable assurance that (i)
transactions are executed in accordance with management's general or specific
authorizations; (ii) transactions are recorded as necessary to permit
preparation of financial statements in conformity with generally accepted
accounting principles and to maintain asset accountability; (iii) access to
assets is permitted only in accordance with management's general or specific
authorization; and (iv) the recorded accountability for assets is compared with
the existing assets at reasonable intervals and appropriate action is taken with
respect to any differences.

     (bb) All material tax returns required to be filed by the Company and
each of its subsidiaries in any jurisdiction have been filed, other than those
filings being contested in good faith, and all material taxes, including
withholding taxes, penalties and interest, assessments, fees and other charges
due pursuant to such returns or pursuant to any assessment received by the
Company or any of its subsidiaries have been paid, other than those being
contested in good faith and for which adequate reserves have been provided.

     (cc) The Company has reviewed its operations and any third parties with
which the Company has a material relationship to evaluate the extent to which
the business or operations of the Company will be affected by the Year 2000
Problem. As a result of such review, the Company does not believe that the Year
2000 Problem will have a material adverse effect on the business, prospects,
financial condition or results of operation of the Company and its subsidiaries,
taken as a whole. The "YEAR 2000 PROBLEM" as used herein means any significant
risk that computer hardware or software used in the receipt, transmission,
processing, manipulation, storage, retrieval, retransmission or other
utilization of data or in the operation of mechanical or electrical systems of
any kind will not be able to reliably distinguish dates beginning on January 1,
2000 from dates prior to January 1, 2000.

     (dd) The Company has not at any time during the last five (5) years (i)
made any unlawful contribution to any candidate for foreign office or failed to
disclose fully any contribution in violation of law, or (ii) made any payment to
any federal or state governmental officer or official, or other person charged
with similar public or quasi-public duties, other than payments required or
permitted by the laws of the United States or any jurisdiction thereof.

     (ee) The Company has not taken and will not take, directly or indirectly,
any action designed to or that might reasonably be expected to cause or result
in stabilization or manipulation of the price of the Common Stock to facilitate
the sale or resale of the Shares.

     SECTION 7. Indemnification.  (a) The Company agrees:

          (i)  to indemnify and hold harmless each Underwriter and each person,
if any, who controls any Underwriter within the meaning of the Act, against any
losses, claims, damages or liabilities to which such Underwriter or any such
controlling person may become subject under the Act or otherwise, insofar as
such losses, claims, damages or liabilities (or actions or proceedings in
respect thereof) arise out of or are based upon (i) any untrue statement

                                       12
<PAGE>

or alleged untrue statement of any material fact contained in the Registration
Statement, any Preliminary Prospectus, the Prospectus or any amendment or
supplement thereto, (ii) the omission or alleged omission to state therein a
material fact required to be stated therein or necessary to make the statements
therein not misleading, or (iii) any alleged act or failure to act by any
Underwriter in connection with, or relating in any manner to, the Shares or the
offering contemplated hereby, and which is included as part of or referred to in
any loss, claim, damage, liability or action arising out of or based upon
matters covered by clause (i) or (ii) above (provided, that the Company shall
not be liable under this clause (iii) to the extent that it is determined in a
final judgment by a court of competent jurisdiction that such loss, claim,
damage, liability or action resulted directly from any such acts or failures to
act undertaken or omitted to be taken by such Underwriter through its gross
negligence or willful misconduct); provided, however, that the Company will not
be liable in any such case to the extent that any such loss, claim, damage or
liability arises out of or is based upon an untrue statement or alleged untrue
statement, or omission or alleged omission made in the Registration Statement,
any preliminary prospectus, the Prospectus, or such amendment or supplement, in
reliance upon and in conformity with written information furnished to the
Company by or through the Representatives specifically for use in the
preparation thereof; and further provided, however, that the Company will not be
liable to any Underwriter who failed to deliver a Prospectus, as then amended or
supplemental, to the person asserting any claim for any such loss, claim, damage
or liability that arises out of or is based upon an untrue statement or alleged
untrue statement, or omission or alleged omission made in any preliminary
prospectus if such actual or alleged untrue statement or omission was cured in
the Prospectus, as then amended or supplemented.

          (ii) to reimburse each Underwriter and each such controlling person
upon demand for any legal or other out-of-pocket expenses reasonably incurred by
such Underwriter or such controlling person in connection with investigating or
defending any such loss, claim, damage or liability, action or proceeding or in
responding to a subpoena or governmental inquiry related to the offering of the
Shares, whether or not such Underwriter or controlling person is a party to any
action or proceeding. In the event that it is finally judicially determined that
the Underwriters were not entitled to receive payments for legal and other
expenses pursuant to this subparagraph, the Underwriters will promptly return
all sums that had been advanced pursuant hereto.

     (b)  Each Underwriter severally and not jointly will indemnify and hold
harmless the Company, each of its directors, each of its officers who have
signed the Registration Statement and each person, if any, who controls the
Company within the meaning of the Act, against any losses, claims, damages or
liabilities to which the Company or any such director, officer, or controlling
person may become subject under the Act or otherwise, insofar as such losses,
claims, damages or liabilities (or actions or proceedings in respect thereof)
arise out of or are based upon (i) any untrue statement or alleged untrue
statement of any material fact contained in the Registration Statement, any
Preliminary Prospectus, the Prospectus or any amendment or supplement thereto,
or (ii) the omission or the alleged omission to state therein a material fact
required to be stated therein or necessary to make the statements therein not
misleading in the light of the circumstances under which they were made; and
will reimburse any legal or other expenses reasonably incurred by the Company or
any such director, officer, or controlling person in connection with
investigating or defending any such loss, claim, damage, liability, action or

                                       13
<PAGE>

proceeding; provided, however, that each Underwriter will be liable in each case
to the extent, but only to the extent, that such untrue statement or alleged
untrue statement or omission or alleged omission has been made in the
Registration Statement, any Preliminary Prospectus, the Prospectus or such
amendment or supplement, in reliance upon and in conformity with written
information furnished to the Company by or through the Representatives
specifically for use in the preparation thereof. This indemnity agreement will
be in addition to any liability which such Underwriter may otherwise have.

     (c)  In case any proceeding (including any governmental investigation)
shall be instituted involving any person in respect of which indemnity may be
sought pursuant to this Section 7, such person (the "indemnified party") shall
promptly notify the person against whom such indemnity may be sought (the
"indemnifying party") in writing. No indemnification provided for in Section
7(a) or (b) shall be available to any party who shall fail to give notice as
provided in this Section 7(c) if the party to whom notice was not given was
unaware of the proceeding to which such notice would have related and was
materially prejudiced by the failure to give such notice, but the failure to
give such notice shall not relieve the indemnifying party or parties from any
liability which it or they may have to the indemnified party for contribution or
otherwise than on account of the provisions of Section 7(a) or (b). In case any
such proceeding shall be brought against any indemnified party and it shall
notify the indemnifying party of the commencement thereof, the indemnifying
party shall be entitled to participate therein and, to the extent that it shall
wish, jointly with any other indemnifying party similarly notified, to assume
the defense thereof, with counsel satisfactory to such indemnified party and
shall pay as incurred the fees and disbursements of such counsel related to such
proceeding. In any such proceeding, any indemnified party shall have the right
to retain its own counsel at its own expense. Notwithstanding the foregoing, the
indemnifying party shall pay as incurred (or within 30 days of presentation) the
fees and expenses of the counsel retained by the indemnified party in the event
(i) the indemnifying party and the indemnified party shall have mutually agreed
to the retention of such counsel, (ii) the named parties to any such proceeding
(including any impleaded parties) include both the indemnifying party and the
indemnified party and representation of both parties by the same counsel would
be inappropriate due to actual or potential differing interests between them or
(iii) the indemnifying party shall have failed to assume the defense and employ
counsel acceptable to the indemnified party within a reasonable period of time
after notice of commencement of the action. It is understood that the
indemnifying party shall not, in connection with any proceeding or related
proceedings in the same jurisdiction, be liable for the reasonable fees and
expenses of more than one separate firm for all such indemnified parties. Such
firm shall be designated in writing by you in the case of parties indemnified
pursuant to Section 7(a) and by the Company in the case of parties indemnified
pursuant to Section 7(b). The indemnifying party shall not be liable for any
settlement of any proceeding effected without its written consent but if settled
with such consent or if there be a final judgment for the plaintiff, the
indemnifying party agrees to indemnify the indemnified party from and against
any loss or liability by reason of such settlement or judgment. In addition, the
indemnifying party will not, without the prior written consent of the
indemnified party, settle or compromise or consent to the entry of any judgment
in any pending or threatened claim, action or proceeding of which
indemnification may be sought hereunder (whether or not any indemnified party is
an actual or potential party to such claim, action or proceeding) unless such
settlement, compromise or consent includes an unconditional release of each
indemnified party from all liability arising out of such claim, action or
proceeding.

                                       14
<PAGE>

     (d)  If the indemnification provided for in this Section 7 is unavailable
to or insufficient to hold harmless an indemnified party under Section 7(a), (b)
or (c) above in respect of any losses, claims, damages or liabilities (or
actions or proceedings in respect thereof) referred to therein, then each
indemnifying party shall contribute to the amount paid or payable by such
indemnified party as a result of such losses, claims, damages or liabilities (or
actions or proceedings in respect thereof) in such proportion as is appropriate
to reflect the relative benefits received by the Company on the one hand and the
Underwriters on the other from the offering of the Shares. If, however, the
allocation provided by the immediately preceding sentence is not permitted by
applicable law then each indemnifying party shall contribute to such amount paid
or payable by such indemnified party in such proportion as is appropriate to
reflect not only such relative benefits but also the relative fault of the
Company on the one hand and the Underwriters on the other in connection with the
statements or omissions which resulted in such losses, claims, damages or
liabilities, (or actions or proceedings in respect thereof), as well as any
other relevant equitable considerations. The relative benefits received by the
Company on the one hand and the Underwriters on the other shall be deemed to be
in the same proportion as the total net proceeds from the offering (before
deducting expenses) received by the Company bear to the total underwriting
discounts and commissions received by the Underwriters, in each case as set
forth in the table on the cover page of the Prospectus. The relative fault shall
be determined by reference to, among other things, whether the untrue or alleged
untrue statement of a material fact or the omission or alleged omission to state
a material fact relates to information supplied by the Company on the one hand
or the Underwriters on the other and the parties' relative intent, knowledge,
access to information and opportunity to correct or prevent such statement or
omission.

     The Company, and the Underwriters agree that it would not be just and
equitable if contributions pursuant to this Section 7(d) were determined by pro
rata allocation (even if the Underwriters were treated as one entity for such
purpose) or by any other method of allocation which does not take account of the
equitable considerations referred to above in this Section 7(d).  The amount
paid or payable by an indemnified party as a result of the losses, claims,
damages or liabilities (or actions or proceedings in respect thereof) referred
to above in this Section 7(d) shall be deemed to include any legal or other
expenses reasonably incurred by such indemnified party in connection with
investigating or defending any such action or claim.  Notwithstanding the
provisions of this subsection (d),  (i) no Underwriter shall be required to
contribute any amount in excess of the underwriting discounts and commissions
applicable to the Shares purchased by such Underwriter, and (ii) no person
guilty of fraudulent misrepresentation (within the meaning of Section 11(f) of
the Act) shall be entitled to contribution from any person who was not guilty of
such fraudulent misrepresentation.  The Underwriters' obligations in this
Section 7(d) to contribute are several in proportion to their respective
underwriting obligations and not joint.

     (e)  In any proceeding relating to the Registration Statement, any
Preliminary Prospectus, the Prospectus or any supplement or amendment thereto,
each party against whom contribution may be sought under this Section 7 hereby
consents to the jurisdiction of any court having jurisdiction over any other
contributing party, agrees that process issuing from such court may be served
upon him or it by any other contributing party and consents to the service of
such process and agrees that any other contributing party may join him or it as
an additional defendant in any such proceeding in which such other contributing
party is a party.

                                       15
<PAGE>

     (f)  Any losses, claims, damages, liabilities or expenses for which an
indemnified party is entitled to indemnification or contribution under this
Section 7 shall be paid by the indemnifying party to the indemnified party as
such losses, claims, damages, liabilities or expenses are incurred. The
indemnity and contribution agreements contained in this Section 7 and the
representations and warranties of the Company set forth in this Agreement shall
remain operative and in full force and effect, regardless of (i) any
investigation made by or on behalf of any Underwriter or any person controlling
any Underwriter, the Company, its directors or officers or any persons
controlling the Company, (ii) acceptance of any Shares and payment therefor
hereunder, and (iii) any termination of this Agreement. A successor to any
Underwriter, or to the Company, its directors or officers, or any person
controlling the Company, shall be entitled to the benefits of the indemnity,
contribution and reimbursement agreements contained in this Section 7.

     (g)  The remedies provided for in this Section 7 are not exclusive and
shall not limit any rights or remedies which may otherwise be available to any
indemnified party at law or in equity.

     SECTION 8.  Conditions of Underwriters' Obligations.  The several
obligations of the Underwriters to purchase the Firm Shares under this Agreement
are subject to the satisfaction of each of the following conditions:

     (a)  All the representations and warranties of the Company contained in
this Agreement shall be true and correct on the Closing Date with the same force
and effect as if made on and as of the Closing Date.

     (b)  If the Company is required to file a Rule 462(b) Registration
Statement after the effectiveness of this Agreement, such Rule 462(b)
Registration Statement shall have become effective by 10:00 P.M., New York City
time, on the date of this Agreement; and no stop order suspending the
effectiveness of the Registration Statement shall have been issued and, to the
Company's knowledge, no proceedings for that purpose shall have been commenced
or shall be pending before or contemplated by the Commission.

     (c)  You shall have received on the Closing Date a certificate dated the
Closing Date, signed by David Struwas and Robert Berlin, in their capacities as
the President and Chief Executive Officer and Chief Financial Officer of the
Company, respectively, confirming the matters set forth in Sections 6(t), 8(a)
and 8(b) (which, with respect to the commencement, pendency and contemplation of
stop order proceedings by the Commission, shall be to their knowledge) and that
the Company has complied with all of the agreements and satisfied all of the
conditions herein contained and required to be complied with or satisfied by the
Company on or prior to the Closing Date.

     (d)  Since the respective dates as of which information is given in the
Prospectus other than as set forth in the Prospectus (exclusive of any
amendments or supplements thereto subsequent to the date of this Agreement), (i)
there shall not have occurred any change or any development involving a
prospective change in the condition, financial or otherwise, or the earnings,
business, management or operations of the Company and its subsidiaries, taken as
a whole, (ii) there shall not have been any change or any development involving
a prospective change in the capital stock or in the long-term debt of the
Company or any of its subsidiaries and (iii) neither the Company nor any of its
subsidiaries shall have incurred any liability or obligation, direct or
contingent, the effect of which, in any such case described in clause 8(d)(i),
8(d)(ii) or 8(d)(iii), in your judgment, is material and adverse and, in your
judgment, makes it impracticable to market the Shares on the terms and in the
manner contemplated in the Prospectus.

                                       16
<PAGE>

     (e)  You shall have received on the Closing Date an opinion (satisfactory
to you and counsel for the Underwriters), dated the Closing Date, of Testa,
Hurwitz & Thibeault, LLP counsel for the Company, to the effect that:

          (i)  the Company has been duly incorporated, is validly existing as a
corporation in good standing under the laws of its jurisdiction of incorporation
and has the corporate power and authority to carry on its business as described
in the Prospectus and to own, lease and operate its properties;

          (ii) the Shares have been duly authorized and, when issued and
delivered to the Underwriters against payment therefor as provided by this
Agreement, will be validly issued, fully paid and nonassessable, and the
issuance of such Shares will not be subject to any preemptive rights, rights of
first refusal or first offer, or similar rights arising under the Delaware
General Corporation Law, the Company's certificate of incorporation or any
agreement filed as an exhibit to the Registration Statement;

          (iii)  this Agreement has been duly authorized, executed and
delivered by the Company;

          (iv) the authorized capital stock of the Company conforms as to
legal matters to the description thereof set forth under the caption
"Description of Capital Stock" in the Prospectus;

          (v)  the Registration Statement has become effective under the Act
and, to such counsel's knowledge, no stop order suspending its effectiveness has
been issued and no proceedings for that purpose are, to such counsel's
knowledge, pending before or contemplated by the Commission;

          (vi) the statements under the captions "Description of Capital Stock"
and "Underwriting" in the Prospectus, insofar as such statements purport to
summarize legal matters present fair summaries of such legal matters, in all
material respects;

          (vii)  the execution, delivery and performance of this Agreement by
the Company, the compliance by the Company with all the provisions hereof and
the consummation of the transactions contemplated hereby will not (A) require
any consent, approval, authorization or other order of, or qualification with,
any court or governmental body or agency (except such as may be required under
the Act, the Exchange Act, and the securities or Blue Sky laws of the various
states), or (B) conflict with or constitute a breach of any of the terms or
provisions of, or a default under, the certificate of incorporation or by-laws
of the Company or any agreement that is filed as an exhibit to the Registration
Statement;

                                       17
<PAGE>

          (viii)  such counsel does not know of any legal or governmental
proceedings pending or threatened to which the Company or any of its
subsidiaries is a party or to which any of their respective property is subject
that are required to be described in the Registration Statement or the
Prospectus and are not so described, or of any contracts or other documents that
are required to be described in the Registration Statement or the Prospectus or
to be filed as exhibits to the Registration Statement that are not so described
or filed as required;

          (ix) the Company is not and, after giving effect to the offering and
sale of the Shares and the application of the proceeds thereof as described in
the Prospectus, will not be, an "investment company" as such term is defined in
the Investment Company Act of 1940, as amended;

          (x)  to such counsel's knowledge, except as disclosed in the
Registration Statement, there are no contracts, agreements or understandings
between the Company and any person granting such person the right to require the
Company to file a registration statement under the Act with respect to any
securities of the Company or to require the Company to include such securities
with the Shares registered pursuant to the Registration Statement; and

          (xi) such counsel has in the course of the preparation of the
Registration Statement and the Prospectus, participated in conferences with
officers, employees and other representatives of the Company,
PricewaterhouseCoopers LLP (the Company's independent public accountants), Day,
Berry & Howard, Swidler Berlin Sherreff and Friedman LLP (regulatory counsel to
the Company) and your representatives and counsel concerning the information
contained in the Registration Statement and the Prospectus and although such
counsel need not pass upon, nor assume any responsibility for, the accuracy,
completeness or fairness of the statements contained in the Registration
Statement and the Prospectus and need not make any independent check or
verification thereof, based on such participation no fact has come to the
attention of such counsel that cause such counsel to believe that the
Registration Statement (except for financial statements, financial statement
schedules, and other financial and statistical data included therein, as to
which such counsel need make no statement), at the time it became effective,
contained an untrue statement of a material fact or omitted to state a material
fact required to be stated therein or necessary in order to make the statements
therein not misleading, or that the Prospectus (except for financial statements,
financial statement schedules, and other financial and statistical data
included, as to which such counsel need make no statement), as of the date of
such Prospectus or as of the Closing Date, included or includes an untrue
statement of a material fact or omitted or omits to state a material fact
necessary in order to make the statements therein, in the light of the
circumstances under which they were made, not misleading.

     The opinion of Testa, Hurwitz & Thibeault, LLP described in Section 8(e)
above shall be rendered to you at the request of the Company and shall so state
therein.

     (f)  You shall have received on the Closing Date an opinion (satisfactory
to you and counsel for the underwriters), dated the Closing Date, of Day, Berry
& Howard, counsel for the Company, to the effect that:

                                       18
<PAGE>

          (i)  all the outstanding shares of capital stock of the Company have
been duly authorized and validly issued and are fully paid and nonassessable and
not subject to any preemptive rights, rights of first refusal or first offer, or
similar rights arising under the Delaware General Corporation Law, the Company's
certificate of incorporation or any agreement filed as an exhibit to the
Registration Statement;

          (ii) all of the outstanding shares of capital stock or limited
liability company interests of each of the Company's subsidiaries have been duly
authorized and validly issued and are fully paid and nonassessable, and are
owned by the Company, directly or indirectly through one or more subsidiaries,
free and clear of any security interest, claim, lien, encumbrance or adverse
interest of any nature;

          (iii)  the Company is duly qualified and is in good standing as a
foreign corporation authorized to do business in the State of Connecticut; and

          (iv) the statements under the caption "Business--Legal Proceedings,"
in the Prospectus, insofar as such statements purport to summarize legal matters
present fair summaries of such legal matters, in all material respects;

     (g)  You shall have received on the Closing Date an opinion, dated the
Closing Date, of Swidler Berlin Sherreff Friedman, LLP, regulatory counsel for
the Company, which opinion shall be to your reasonable satisfaction.

     (h)  You shall have received on the Closing Date an opinion, dated the
Closing Date, of Brobeck, Phleger & Harrison LLP, counsel for the Underwriters,
as to the matters referred to in Sections 8(e)(ii), 8(e)(vi), 8(e)(viii) (but
only with respect to the statements under the caption "Description of Capital
Stock" and "Underwriting") and 8(e)(xii).

     In giving such opinions, with respect to the matters covered by Section
8(e)(xi), Testa, Hurwitz & Thibeault LLP and Brobeck, Phleger & Harrison LLP may
state that their opinion and belief are based upon their participation in the
preparation of the Registration Statement and Prospectus and any amendments or
supplements thereto and review and discussion of the contents thereof, but are
without independent check or verification except as specified.

     (i)  You shall have received, on each of the date hereof and the Closing
Date, a letter dated the date hereof or the Closing Date, as the case may be, in
form and substance satisfactory to you, from PricewaterhouseCoopers LLP,
independent public accountants, containing the information and statements of the
type ordinarily included in accountants' "comfort letters" to Underwriters with
respect to the financial statements and certain financial information contained
in the Registration Statement and the Prospectus.

     (j)  The Company shall have delivered to you the agreements specified in
Section 2 hereof which agreements shall be in full force and effect on the
Closing Date.

     (k)  The Shares shall have been duly listed for quotation on the Nasdaq
National Market.

                                       19
<PAGE>

     (l)  The Company shall not have failed on or prior to the Closing Date to
perform or comply with any of the agreements herein contained and required to be
performed or complied with by the Company on or prior to the Closing Date.

     The several obligations of the Underwriters to purchase any Additional
Shares hereunder are subject to the delivery to you on the applicable Option
Closing Date of such documents as you may reasonably request with respect to the
good standing of the Company, the due authorization and issuance of such
Additional Shares and other matters related to the issuance of such Additional
Shares.

     SECTION 9.   Effectiveness of Agreement and Termination.  This Agreement
shall become effective upon the execution and delivery of this Agreement by the
parties hereto.

     This Agreement may be terminated at any time on or prior to the Closing
Date by you by written notice to the Company if any of the following has
occurred:  (i) any outbreak or escalation of hostilities or other national or
international calamity or crisis or change in economic conditions or in the
financial markets of the United States or elsewhere that, in your judgment, is
material and adverse and, in your judgment, makes it impracticable to market the
Shares on the terms and in the manner contemplated in the Prospectus, (ii) the
suspension or material limitation of trading in securities or other instruments
on the New York Stock Exchange, the American Stock Exchange, the Chicago Board
of Options Exchange, the Chicago Mercantile Exchange, the Chicago Board of Trade
or the Nasdaq National Market or limitation on prices for securities or other
instruments on any such exchange or the Nasdaq National Market, (iii) the
suspension of trading of any securities of the Company on any exchange or in the
over-the-counter market, (iv) the enactment, publication, decree or other
promulgation of any federal or state statute, regulation, rule or order of any
court or other governmental authority which in your opinion materially and
adversely affects, or will materially and adversely affect, the business,
prospects, financial condition or results of operations of the Company and its
subsidiaries, taken as a whole, (v) the declaration of a banking moratorium by
either federal or New York State authorities or (vi) the taking of any action by
any federal, state or local government or agency in respect of its monetary or
fiscal affairs which in your opinion has a material adverse effect on the
financial markets in the United States.

     If on the Closing Date or on an Option Closing Date, as the case may be,
any one or more of the Underwriters shall fail or refuse to purchase the Firm
Shares or Additional Shares, as the case may be, which it has or they have
agreed to purchase hereunder on such date and the aggregate number of Firm
Shares or Additional Shares, as the case may be, which such defaulting
Underwriter or Underwriters agreed but failed or refused to purchase is not more
than one-tenth of the total number of Firm Shares or Additional Shares, as the
case may be, to be purchased on such date by all Underwriters, each non-
defaulting Underwriter shall be obligated severally, in the proportion which the
number of Firm Shares set forth opposite its name in Schedule I bears to the
total number of Firm Shares which all the non-defaulting Underwriters have
agreed to purchase, or in such other proportion as you may specify, to purchase
the Firm Shares or Additional Shares, as the case may be, which such defaulting
Underwriter or Underwriters agreed but failed or refused to purchase on such
date; provided that in no event shall the number of Firm Shares or Additional
Shares, as the case may be, which any Underwriter has agreed to purchase
pursuant to Section 2 hereof be increased pursuant to this

                                       20
<PAGE>

Section 9 by an amount in excess of one-ninth of such number of Firm Shares or
Additional Shares, as the case may be, without the written consent of such
Underwriter. If on the Closing Date any Underwriter or Underwriters shall fail
or refuse to purchase Firm Shares and the aggregate number of Firm Shares with
respect to which such default occurs is more than one-tenth of the aggregate
number of Firm Shares to be purchased by all Underwriters and arrangements
satisfactory to you and the Company for purchase of such Firm Shares are not
made within 48 hours after such default, this Agreement will terminate without
liability on the part of any non-defaulting Underwriter and the Company. In any
such case which does not result in termination of this Agreement, either you or
the Company shall have the right to postpone the Closing Date, but in no event
for longer than seven days, in order that the required changes, if any, in the
Registration Statement and the Prospectus or any other documents or arrangements
may be effected. If, on an Option Closing Date, any Underwriter or Underwriters
shall fail or refuse to purchase Additional Shares and the aggregate number of
Additional Shares with respect to which such default occurs is more than one-
tenth of the aggregate number of Additional Shares to be purchased on such date,
the non-defaulting Underwriters shall have the option to (i) terminate their
obligation hereunder to purchase such Additional Shares or (ii) purchase not
less than the number of Additional Shares that such non-defaulting Underwriters
would have been obligated to purchase on such date in the absence of such
default. Any action taken under this paragraph shall not relieve any defaulting
Underwriter from liability in respect of any default of any such Underwriter
under this Agreement.

     SECTION 10. Miscellaneous.  Notices given pursuant to any provision of this
Agreement shall be addressed as follows: (i) if to the Company, to DSL.net,
Inc., 545 Long Wharf Drive, New Haven, Connecticut  06511, Attention: General
Counsel and (ii) if to any Underwriter or to you, to you c/o Deutsche Bank
Securities Inc., One Bankers Trust Plaza, 130 Liberty Street, New York, New York
10006, Attention:  General Counsel, or in any case to such other address as the
person to be notified may have requested in writing.

     The respective indemnities, contribution agreements, representations,
warranties and other statements of the Company and the several Underwriters set
forth in or made pursuant to this Agreement shall remain operative and in full
force and effect, and will survive delivery of and payment for the Shares,
regardless of (i) any investigation, or statement as to the results thereof,
made by or on behalf of any Underwriter, the officers or directors of any
Underwriter, any person controlling any Underwriter, the Company, the officers
or directors of the Company or any person controlling the Company, (ii)
acceptance of the Shares and payment for them hereunder and (iii) termination of
this Agreement.

     If for any reason the Shares are not delivered by or on behalf of the
Company as provided herein (other than as a result of any termination of this
Agreement pursuant to Section 9), the Company agrees to reimburse the several
Underwriters for all out-of-pocket expenses (including the fees and
disbursements of counsel) incurred by them. Notwithstanding any termination of
this Agreement, the Company shall be liable for all expenses which it has agreed
to pay pursuant to Section 5(i) hereof.  The Company also agrees to reimburse
the several Underwriters, their directors and officers and any persons
controlling any of the Underwriters for any and all fees and expenses
(including, without limitation, the fees disbursements of counsel) incurred by
them in connection with enforcing their rights hereunder (including, without
limitation, pursuant to Section 7 hereof).

                                       21
<PAGE>

     Except as otherwise provided, this Agreement has been and is made solely
for the benefit of and shall be binding upon the Company, the Underwriters, the
Underwriters' directors and officers, any controlling persons referred to
herein, the Company's directors and the Company's officers who sign the
Registration Statement and their respective successors and assigns, all as and
to the extent provided in this Agreement, and no other person shall acquire or
have any right under or by virtue of this Agreement.  The term "successors and
assigns" shall not include a purchaser of any of the Shares from any of the
several Underwriters merely because of such purchase.

     This Agreement shall be governed and construed in accordance with the laws
of the State of New York.

     This Agreement may be signed in various counterparts which together shall
constitute one and the same instrument.

     Please confirm that the foregoing correctly sets forth the agreement
between the Company and the several Underwriters.

                                          Very truly yours,

                                          DSL.net, Inc.


                                          By:
                                             ---------------------------------
                                             Title:
DEUTSCHE BANK SECURITIES INC.
DONALDSON, LUFKIN & JENRETTE
  SECURITIES CORPORATION
LEHMAN BROTHERS INC.
DLJdirect INC.
Acting severally on behalf of themselves
  and the several Underwriters named
  in Schedule I hereto
By:  DEUTSCHE BANK SECURITIES INC.

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

                                       22
<PAGE>

                                   SCHEDULE I
                                   ----------



Underwriters                                              Number of Firm Shares
                                                            to be Purchased

Deutsche Bank Securities Inc.
Donaldson, Lufkin & Jenrette Securities Corporation
Lehman Brothers
DLJ direct
                                                          Total

                                       23
<PAGE>

                                    Annex I
                                    -------

[Insert names of stockholders of the Company who will not be required to sign
lock ups]

                                       24