Exhibit 10.1
                      FORM OF REGISTRATION RIGHTS AGREEMENT

     This AGREEMENT (this "Agreement"), dated as of [__], 2006, among Level 3
Communications, Inc., a Delaware corporation ("Parent") and Cheshire Holding
Corp., as agent (the "Stockholders' Agent") for the securityholders of the
Looking Glass Networks Holding Co., Inc., a Delaware corporation (the
"Company").

                              W I T N E S S E T H:

     WHEREAS, Parent, Eldorado Acquisition One, Inc., a Delaware corporation
("Merger Sub"), the Company and the Stockholders' Agent are parties to a
Agreement and Plan of Merger, dated as of June 2, 2006 (the "Merger Agreement"),
pursuant to which Merger Sub will be merged with and into the Company, with the
Company continuing as the surviving corporation (the "Merger");

     WHEREAS, in connection with the Merger, certain stockholders of the Company
will receive an aggregate of [ ] shares (such shares, the "Shares") of common
stock, par value $0.01 per share of Parent ("Parent Common Stock"), including [
] shares to be held in escrow pursuant to the Escrow Agreement;

     WHEREAS, it is a condition to consummation of the Merger that Parent enter
into this Agreement providing for the registration of the shares of Parent
Common Stock to be received by certain stockholders of the Company in the
Merger;

     WHEREAS, the Stockholders' Agent was appointed by the Selling Stockholders
pursuant to that certain Consent, Waiver and Appointment of Stockholders' Agent,
dated as of June 2, 2006, among the Stockholders' Agent, the Company and other
parties named therein (the "Consent") and pursuant to the Consent, the
Stockholders' Agent was authorized to enter this Agreement on behalf the Selling
Stockholders; and

     WHEREAS, Parent is willing to prepare and file a registration statement
under the Securities Act of 1933, as amended (the "Securities Act"), with the
Securities and Exchange Commission (the "SEC") with respect to the Shares and to
maintain the effectiveness of such registration statement, upon the terms and
subject to the conditions set forth herein;

     NOW THEREFORE, in consideration of the foregoing and the respective
covenants and agreements hereinafter contained, the parties hereby agree as
follows:

     SECTION 1. Definitions. All terms used in this Agreement which are defined
in the Merger Agreement shall have the meanings specified in the Merger
Agreement unless the context otherwise requires.

     SECTION 2. Registration of the Shares.

     2.1 Shelf Registration Statement. As soon as reasonably practicable after
the date hereof and in any event within five (5) business days following the
consummation of the Acquisition, Parent shall prepare and file with the SEC a
shelf registration statement, relating to the offer and sale by the Stockholders
receiving Shares in the Merger (including the Escrow




Agent) (the "Selling Stockholders") at any time and from time to time on a
delayed or continuous basis in accordance with Rule 415 under the Securities Act
and in accordance with this Agreement, of all the Shares (the "Registration
Statement"). If, at the time of filing of the Registration Statement, the
Registration Statement is eligible to become effective upon filing pursuant to
Rule 462(e) (or any successor rule) under the Securities Act, Parent shall file
the Registration Statement as an automatic shelf registration statement pursuant
to such rule. If the Registration Statement is not so eligible to become
effective upon filing, Parent shall use its reasonable best efforts to have the
Registration Statement declared effective as promptly as practicable (with such
date on which the Registration Statement becomes effective referred to as the
"Effective Date"). Promptly (i) upon the filing thereof in the case of an
automatic shelf or (ii) upon oral receipt of an order of the SEC declaring the
Registration Statement effective, Parent shall deliver to the Stockholders'
Agent a copy of such Registration Statement and any amendments thereto together
with an opinion of counsel representing Parent for the purposes of such
Registration, in form and substance reasonably acceptable to the Stockholders'
Agent, addressed to the Stockholders' Agent, in such capacity as a
representative of the Stockholders receiving Shares in the Merger, including,
confirming that the Registration Statement is effective and that all of the
Shares have been duly registered and, subject to the transfer restrictions
contained in this Agreement, are freely transferable and that all of the shares
have been admitted for listing on the NASDAQ Stock Market.

     2.2 Adjustment. If at any time the Shares as a class shall have been
increased, decreased, changed into or exchanged for a different number or class
of shares or securities as a result of a reorganization, recapitalization,
reclassification, stock dividend, stock split, reverse stock split, combination
or exchange of shares or other similar change in capitalization, then an
appropriate and proportionate adjustment shall be made to the number of Shares
for all purposes under this Agreement.

     SECTION 3. Maintenance of Registration Statement and Prospectuses.

     3.1 Parent shall use its reasonable best efforts to keep the Registration
Statement and the prospectus contained therein (as amended or supplemented from
time to time, the "Prospectuses" and each a "Prospectus") continuously effective
until the Termination Date (as defined below). In the event the Registration
Statement cannot be kept effective for such period, Parent shall use its
reasonable best efforts to prepare and file with the SEC and have declared
effective as promptly as practicable and in any event within ten (10) business
days following the date on which the Registration Statement was no longer
effective another registration statement on the same terms and conditions as the
initial Registration Statement and such registration statement shall be
considered the Registration Statement for purposes hereof. Parent shall furnish
to the Stockholders' Agent such number of copies of a Prospectus in conformity
with the requirements of the Act, and an electronic copy of the Prospectus to
facilitate the disposition of the Shares owned by the Selling Stockholders.

     3.2 Parent shall advise the Stockholders' Agent promptly in writing when
the Registration Statement, or any post-effective amendment thereto, has been
declared effective by the SEC. Parent shall advise the Stockholders' Agent in
writing of the receipt by Parent of any stop order from the SEC suspending the
effectiveness of the Registration Statement, and if at any time there shall be a
stop order suspending the effectiveness of the Registration Statement,

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Parent shall use its reasonable best efforts to obtain promptly the withdrawal
of such order. Parent shall advise the Stockholders' Agent promptly in writing
of the existence of any fact and the happening of any event that makes any
statement of a material fact made or incorporated by reference in the
Registration Statement or Prospectus untrue, or that requires the making of any
additions to or changes in the Registration Statement or Prospectus in order to
make the statements therein not misleading and in such event Parent shall
prepare and file with the SEC, as soon as reasonably practicable, an amendment
to such Registration Statement or an amendment or supplement to such Prospectus
or a Current Report on Form 8-K, as the case may be, so that, as so amended or
supplemented, such Registration Statement and such Prospectus will 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 light of
the circumstances then existing, not misleading. Upon receipt of such written
advice, the Stockholder's Agent shall cause the Selling Stockholders to
discontinue and refrain from making any sales of Shares by use of such
Registration Statement or such Prospectus, until such time as Parent advises the
Stockholders' Agent that such Registration Statement or such Prospectus no
longer contains an untrue statement or omission of a material fact.

     3.3 The Stockholders' Agent shall furnish to Parent such information
regarding the Selling Stockholders and the distribution of the Shares as Parent
may from time to time reasonably request in writing in order to comply with the
Securities Act. The Stockholders' Agent shall notify Parent as promptly as
practicable of any inaccuracy or change in information previously furnished by
such party to Parent or of the happening of any event in either case as a result
of which any Prospectus relating to the Registration Statement contains an
untrue statement of a material fact regarding such party or the distribution of
such Shares, or omits to state any material fact regarding such party or the
distribution of such Shares required to be stated therein or necessary to make
the statements therein not misleading in light of the circumstances then
existing, and to furnish promptly to Parent any additional information required
to correct or update any previously furnished information or required so that
such Prospectus shall not contain, with respect to such party or the
distribution of such Shares 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 not misleading in light of the circumstances then existing.

     3.4 Notwithstanding anything to the contrary contained herein, for a period
not to exceed forty-five (45) consecutive calendar days and not to exceed
seventy (70) aggregate calendar days in any twelve-month period (each a "Black
Out Period"), Parent will not be required to file any registration statement
pursuant to this Agreement, file any amendment thereto, furnish any supplement
to a prospectus included in a registration statement pursuant to this Agreement,
make any other filing with the SEC required pursuant to this Agreement, cause
any registration statement or other filing with the SEC to become effective, or
take any similar action, and any and all sales of Shares by the Selling
Stockholders pursuant to an effective registration statement shall be suspended:
(i) if an event has occurred and is continuing as a result of which any such
registration statement or prospectus would, in Parent's good faith judgment
after consultation with outside counsel, 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 not misleading, (ii) if Parent notifies
the Stockholders' Agent that such actions would, in Parent's good faith judgment
after consultation with outside counsel, require the disclosure of

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material non-public information which the Board of Directors of Parent has
determined would be seriously detrimental to Parent to disclose and which Parent
would not otherwise be required to disclose or (iii) if Parent notifies the
Stockholders' Agent that, in Parent's good faith judgment after consultation
with outside counsel, it is necessary to suspend sales of Shares by the Selling
Stockholders, to facilitate a pending or proposed public or Rule 144A offering
by Parent of Parent Common Stock or Common Stock Equivalents (as defined below),
provided, however, that any such suspension of sales of Shares pursuant to
clause (iii) shall be not longer than twenty-one (21) consecutive calendar days,
provided, further, that no such suspension of sales of Shares pursuant to clause
(iii) may occur during the five (5) trading day period following the Effective
Date. Upon the termination of the condition described in clauses (i), (ii) or
(iii) above, Parent shall promptly give written notice to the Stockholders'
Agent and shall promptly file any registration statement or amendment thereto
required to be filed by it pursuant to this Agreement, furnish any prospectus
supplement or amendment required to be furnished pursuant to this Agreement,
make any other filing with the SEC required of it or terminate any suspension of
sales it has put into effect and shall take such other actions to permit
registered sales of Shares as contemplated by this Agreement. For purposes of
this Agreement, "Common Stock Equivalents" shall mean any rights, warrants,
options, convertible securities or indebtedness, exchangeable securities or
indebtedness, or other rights, exercisable for or convertible or exchangeable
into, directly or indirectly, Parent Common Stock and securities convertible or
exchangeable into Parent Common Stock, whether at the time of issuance or upon
the passage of time or the occurrence of any future event. All calendar days
prior to the Termination Date in which the Registration Statement is not kept
continuously effective (whether in accordance with the provisions of Section 3.1
or otherwise) shall count against the permissible Black Out Periods specified in
this Section 3.4.

     3.5 Parent shall take all actions necessary to execute such documents and
cause all of the Shares to be admitted for listing on the NASDAQ Stock Market,
which listing shall be effective on the Effective Date.

     SECTION 4. Blue Sky. In connection with the registration under Section 2
hereof, Parent shall take all actions necessary to permit the resale by the
Selling Stockholders of any Parent Common Stock under the blue sky laws of the
several states, except that Parent shall not for any such purpose be required to
qualify generally to do business as a foreign corporation in any jurisdiction
wherein it would not but for the requirements of this Section 4 be obligated to
be so qualified, subject itself to taxation in any such jurisdiction or to
consent to general service of process in any such jurisdiction.

     SECTION 5. Expenses. All expenses incident to Parent's performance of or
compliance with this Agreement will be borne by Parent, including, without
limitation, all: (i) registration and filing fees and expenses; (ii) expenses of
printing; (iii) fees and expenses of counsel for Parent; and (iv) fees and
expenses of one counsel for the Selling Stockholders, provided, however, such
fees pursuant to this clause (iv) shall not exceed $5,000. Notwithstanding the
foregoing, Parent shall not be liable for and shall not pay any expenses or fees
of more than one counsel for the Selling Stockholders or any commissions to be
paid in connection with any sale of the Shares by the Selling Stockholders.

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     SECTION 6. Termination. The obligations of Parent hereunder, with respect
to the Shares, shall terminate upon the earlier of (i) the date on which all
Shares covered by the Registration Statement have been disposed of by the
Selling Stockholders and (ii) the second anniversary of the Closing Date of the
Merger. The date on which such obligations shall terminate shall be referred to
as the "Termination Date."

     SECTION 7. Indemnification.

     7.1 Parent will, and does hereby agree to, indemnify and hold harmless each
Selling Stockholder, and each of their directors, officers, employees and agents
and each person controlling a Selling Stockholder with respect to any
registration effected pursuant to this Agreement against all claims, losses,
damages, and liabilities (or actions in respect thereto) including any of the
foregoing incurred in settlement of any litigation, commenced or threatened, to
which a Selling Stockholder may become subject under the Securities Act, the
Securities Exchange Act of 1934 (the "Exchange Act"), or other federal or state
law insofar as such claims, losses, damages or liabilities (or actions in
respect thereto) arise out of or are based on any untrue statement (or alleged
untrue statement) of a material fact contained in any registration statement or
prospectus relating to the Shares, or other document, or any amendment or
supplement thereto, or any omission (or alleged omission) to state therein a
material fact required to be stated therein or necessary to make the statements
therein not misleading, and will reimburse each such party for any legal and any
other expenses reasonably incurred in connection with investigating or defending
any such claim, loss, damage, liability, or action; provided that Parent will
not be liable in any such case to the extent that any such claim, loss, damage,
liability or expense arises out of or is based on any untrue statement or
omission based upon written information furnished to Parent by such party and
stated to be specifically for use therein and provided further, that Parent
shall only reimburse such parties for the fees and expenses of a single legal
counsel for all such parties.

     7.2 The Selling Stockholders will, severally based on Shares sold pursuant
to a registration effected pursuant to this Agreement, but not jointly, if
Shares held by or issuable to such party are included in a registration effected
pursuant to this Agreement, indemnify Parent, each of its directors and
officers, each person controlling Parent and the officers and directors of each
such controlling person against all claims, losses, damages, and liabilities (or
actions in respect thereof) including any of the foregoing incurred in
settlement of any litigation, commenced or threatened, arising out of or based
on any untrue statement (or alleged untrue statement) of a material fact
contained in the Registration Statement or the Prospectus included therein, or
any omission (or alleged omission) to state therein a material fact required to
be stated therein or necessary to make the statements therein not misleading,
and will reimburse Parent, and each such director, officer and controlling
person, for any legal or any other expenses reasonably incurred in connection
with investigating or defending any such claim, loss, damage, liability, or
action, in each case to the extent, but only to the extent that such untrue
statement (or alleged untrue statement) or omission (or alleged omission) was
made in such Registration Statement or Prospectus, in reliance upon and in
conformity with written information furnished to Parent by such party and stated
to be specifically for use therein. Notwithstanding the foregoing, the liability
of each Selling Stockholder under this Section shall be limited in an amount
equal to the per share sales price (less any underwriting discounts and
commissions) multiplied by the number of Shares sold by such party pursuant to
the Registration Statement.

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     7.3 Each party entitled to indemnification under this Section 7 (the
"Indemnified Party") shall give written notice to the party required to provide
such indemnification (the "Indemnifying Party") of any claim as to which
indemnification may be sought promptly after such Indemnified Party has actual
knowledge thereof, and shall permit the Indemnifying Party to assume the defense
of any such claim or any litigation resulting therefrom; provided that counsel
for the Indemnifying Party, who shall conduct the defense of such claim or
litigation, shall be subject to approval by the Indemnified Party (whose
approval shall not be unreasonably withheld) and after the Indemnifying Party
assumes the defense thereof, the Indemnifying Party shall not be liable to such
Indemnified Party for any legal or other expenses subsequently incurred by the
latter in connection with the defense thereof, unless in the reasonable judgment
of the Indemnified Party, representation of such Indemnified Party by such
counsel would be inappropriate due to actual or potential differing interests
between such Indemnified Party and the Indemnifying Party in such proceeding in
which case such Indemnified Party shall have the right to employ separate
counsel to participate in such defense at the expense of the Indemnifying Party;
it being understood that the Indemnifying Party shall not, in connection with
any one such action or separate but substantially similar or related actions in
the same jurisdiction arising out of the same general allegations, be liable for
the reasonable fees and expenses of more than one separate firm of attorneys at
any time for all such Indemnified Parties provided, however, that the
Indemnifying Party shall bear the expenses of independent counsel for the
Indemnified Party if the Indemnified Party reasonably determines that
representation of more than one party by the same counsel would be inappropriate
due to actual or potential conflicts of interest between the Indemnified Party
and the Indemnifying Party; and provided further that the failure of any
Indemnified Party to give notice as provided herein shall not relieve the
Indemnifying Party of its obligations under this Section 7, except to the extent
that such failure to give notice shall materially adversely affect the
Indemnifying Party in the defense of any such claim or any such litigation. No
Indemnifying Party, in the defense of any such claim or litigation, shall,
except with the consent of each Indemnified Party, consent to entry of any
judgment or enter into any settlement that does not include as an unconditional
term thereof the giving by the claimant or plaintiff therein, to such
Indemnified Party, of a release from all liability in respect to such claim or
litigation.

     7.4 If the indemnification provided for in subsection (a) or (b) of this
Section 7 is for any reason unavailable to an Indemnified Party with respect to
any claims, actions, demands, losses, damages, liabilities, costs or expenses
referred to therein, then each Indemnifying Party under any such subsection, in
lieu of indemnifying such Indemnified Party thereunder, hereby agrees to
contribute to the amount paid or payable by such Indemnified Party as a result
of such claims, actions, demands, losses, damages, liabilities, cost or expenses
in such proportion as is appropriate to reflect the relative fault of the
Indemnifying Party on the one hand and of the Indemnified Party on the other in
connection with the statements or omissions which resulted in such claims,
actions, demands, losses, damages, liabilities, costs or expenses, as well as
any other relevant equitable considerations. The relative fault of the
Indemnifying Party and of the Indemnified Party 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 Indemnifying Party or by the Indemnified
Party and the parties' relative intent, knowledge, access to information and
opportunity to correct or prevent such statement or omission. Notwithstanding
the foregoing, the amount any Selling Stockholder shall be obligated to
contribute pursuant to this subsection (d) shall be limited to an

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amount equal to the per share sale price (less any underwriting discount and
commissions) multiplied by the number of Shares sold by such party pursuant to
the Registration Statement which gives rise to such obligation to contribute
(less aggregate amount of any damages which such party has otherwise been
required to pay in respect of such claim, action, demand, loss, damage,
liability, cost or expense or any substantially similar claim, action, demand,
loss, damage, liability, cost or expense arising from the sale of such Shares).
No person guilty of fraudulent misrepresentation (within the meaning of Section
11(f) of the Securities Act) shall be entitled to contribution hereunder from
any person who was not guilty of such fraudulent misrepresentation. The
obligations of the Selling Stockholders under this paragraph will be several
(based on Shares sold pursuant to a registration effected pursuant to this
Agreement) and not joint.

     SECTION 8. Rule 144 Reporting. With a view to making available to the
Selling Stockholders the benefits of certain rules and regulations of the SEC
which may permit the sale of the Shares to the public without registration,
Parent agrees to use its best efforts to:

     8.1 comply, on a timely basis with all the reporting requirements of the
Exchange Act, and comply with all other public information reporting
requirements of the SEC as a condition to the availability of an exemption from
the Securities Act under Rule 144 thereunder, as amended from time to time, or
successor rule thereto, for the sale of Shares by the Selling Stockholders;

     8.2 provide, at Parent's expense, such opinion of counsel as may be
reasonably requested by the transfer agent for the Shares in connection with
each sale of Shares pursuant to an exemption from the registration requirements
of the Securities Act (under Rule 144 thereunder, as amended from time to time,
or successor rule thereto or otherwise) or otherwise, so long as the Selling
Stockholders have furnished to counsel documentation reasonably acceptable to
such counsel related to the transfer and the Shares; and

     8.3 whenever the Selling Stockholders are able to demonstrate to Parent
that the provisions of Rule 144(k) (or any successor rule) under the Securities
Act are available to them and have furnished to Parent such documentation in
connection therewith as Parent may reasonably request, provide, at Parent's
expense, new certificates that do not bear a restrictive legend.

     8.4 so long as the Selling Stockholder owns any Shares, furnish to the
Stockholders' Agent forthwith upon request, a copy of the most recent annual or
quarterly report of Parent, and such other reports and documents as such party
may reasonably request in availing itself of any rule or regulation of the SEC
allowing it to sell any such Shares without registration; provided that such
reports are not otherwise available to the Stockholder's Agent on the SEC's
Edgar web site or Parent's web site.

     SECTION 9. Amendments. This Agreement may not be amended without the
written consent of Parent and (i) the Selling Stockholders owning at least
two-thirds (2/3rds) of the aggregate of the Shares, or (ii) the Stockholders'
Agent.

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     SECTION 10. Miscellaneous.

     10.1 Benefits of Agreement. Except as otherwise provided herein, nothing in
this Agreement, expressed or implied, shall give or be construed to give any
person, firm or corporation, other than the parties hereto, any legal or
equitable right, remedy or claim under any covenant, condition or provision
contained in this Agreement being for the sole benefit of the parties hereto.

     10.2 Successors and Assigns. This Agreement shall be binding upon Parent
and its successors and assigns and shall inure to the benefit of the Selling
Stockholders and to the benefit of their successors and permitted assigns.

     10.3 Notices. Any notice, request, instruction or other document to be
given hereunder shall be in writing and delivered personally or sent by
registered or certified mail, postage prepaid, by reputable national express
courier or shipping cost prepaid, according to the instructions set forth below.
Such notices shall be deemed given: at the time delivered by hand, if personally
delivered; three business days after having been sent by registered or certified
mail; and one business day after having been sent by express courier.

                  If to the Stockholders' Agent:

                           Cheshire Holding Corp.
                           c/o JPMorgan Chase Bank, N.A.
                           270 Park Avenue
                           New York, NY 10017
                           Attn:  Charles O. Freegood

                  Copy to (which shall not constitute notice):

                           Kirkland & Ellis LLP
                           200 East Randolph Drive
                           Chicago, Illinois  60601
                           Attn:  Jon A. Ballis

                  If to Parent:

                           Level 3 Communications, Inc.
                           1025 Eldorado Blvd.
                           Broomfield, CO 80021
                           Attn:  General Counsel

                  Copy to (which shall not constitute notice):

                           Willkie Farr & Gallagher LLP
                           787 Seventh Avenue
                           New York, New York 10019
                           Attn:  David K. Boston

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                  Governing Law. THIS AGREEMENT SHALL BE GOVERNED BY AND
CONSTRUED IN ACCORDANCE WITH THE LAWS OF THE STATE OF NEW YORK, WITHOUT REGARD
TO PRINCIPLES OF CONFLICTS OF LAW.

                  Counterparts.; Facsimile. This Agreement may be executed in
two or more counterparts, each of which will be deemed an original, but all such
counterparts taken together will constitute one and the same Agreement. Any
facsimile copies hereof or signature hereon shall, for all purposes, be deemed
originals

                  Severability. In the event any provision in this Agreement
shall be held invalid, illegal or unenforceable in any respect for any reason,
the validity, legality and enforceability of any such provision in every other
respect and the remaining provisions shall not in any way be affected or
impaired thereby.

                            [Signature Page Follows]









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

                   LEVEL 3 COMMUNICATIONS, INC.


                   By:  ________________________________________________
                        Name:
                        Title:


                   CHESHIRE HOLDING CORP., in its capacity as Stockholders'
                        Agent and on behalf of the Selling Stockholders




                   By:  ________________________________________________
                        Name:
                        Title:

                 [Registration Rights Agreement Signature Page]