# **Exhibit 10.43**

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# **EXECUTION COPY**

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# **REVOLVING CREDIT AGREEMENT**

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This Revolving CreditFacility (“Agreement” or “Credit Facility”) is entered into as ofMarch 30, 2006 (“Effective Date”) by and between VistulaCommunications Services, Inc., a Delaware corporation (“Borrower”or the “Company”) and Indigo Investments I LLC (“Lender”, or “Purchaser”).Each of Borrower and Lender may be referred to herein individually as a “Party”and collectively as the “Parties”.

 

**WITNESSETH:**

 

**WHEREAS,** the Company desires to sell and issue to theLender, and the Purchaser wishes to purchase from the Company, a Note in theprincipal amount of up to five million United States dollars ($5,000,000).

 

**NOW, THEREFORE,** in consideration of the foregoing premisesand the covenants contained herein and other good and valuable consideration,the receipt and sufficiency of which are hereby acknowledged, the Partieshereto agree as follows:

 

**SECTION 1. **Initial Advance; PeriodicLoans. (a) From and after the date hereof through and until September 30,2006, Lender hereby agrees to make periodic loans to the Borrower in anaggregate principal amount at any one time outstanding, not to exceed $5,000,000(“Maximum Amount”). Borrower shall execute a promissory note substantiallyin the form of Exhibit A hereto evidencing its obligationshereunder (the “Note”). On the Effective Date, up to $1,300,000 shall beadvanced to the Borrower for working capital and general corporate purposes(the “Initial Advance”). For the avoidance of doubt, the first$1,300,000 advanced to the Company pursuant to this Section 1(a),regardless of when such advances are made, shall not be subject to therequirements set forth in Section 1(b) below.

 

(b)                                 Duringthe Term (as defined below), from time to time, Borrower may notify theLender of its need to borrow additional funds pursuant to this Agreement.Within ten (10) business days of receipt of such notice from the Borrowerseeking to borrow funds, the Lender shall forward to the Borrower the amount offunds requested by Borrower in such notice, up to, but (together with theInitial Advance) not in excess of, the Maximum Amount; provided, that Borrowerprovides Lender with an officer’s certificate, the form and substance ofwhich must be satisfactory to Lender, certifying that at the time of suchnotice: (i) Borrower is incompliance with the covenants set forth in Section 7 of this Agreement; (ii) Borrowerhas not violated any of the negative covenants set forth in Section 8 ofthis Agreement; and (iii) such requested advance does not exceed 80% ofthe Company’s Computer Directed Router Reports (“CDR”) detailing chargesto be billed to acceptable customers. Lender shall have the absolute right torequest additional evidence, as deemed necessary by the Lender in its solediscretion, in support of such officer’s certificate.

 

**SECTION 2. **Periodic Finance Charges;Commitment Fee; Warrants. (a) All outstanding principal shall bearinterest at a rate of 1.5% per month simple interest. In an Event of 

 

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Default (as defined in Section 12)the interest rate shall increase by an amount equal to the lesser of 2.5% permonth or the maximum amount permitted under applicable law (the “DefaultRate”).

 

(b)                                 Inaddition, the Company shall pay theLender a 2.25% commitment fee on the entire amount of the Credit Facility (the “CommitmentFee”) and shall grant Lender a five (5) year warrant to purchase up to500,000 shares of the Company’s common stock at an exercise price equal to$1.50 per share (the “Warrant”; and such shares the “Warrant Shares”).The Warrant is attached hereto as Exhibit B. Lender may distributethe Warrant Shares to its Members on a pro rata basis based on each Member’spercentage interest in Lender.

 

**SECTION 3. **Payments. All outstanding principal and interest on theCredit Facility plus the Commitment Fee shall be due and payable on the earlierof (i) the six (6) month anniversary of the Effective Date (“MaturityDate”), or (ii) the closing of a Qualified Equity Financing (asdefined below); provided, that, in the event that a Qualified Equity Financingcloses prior to the Maturity Date, the Company shall pay the Lender an earlyrepayment fee equal to 2.25% of the total amount of the Credit Facility. Forpurposes of this Agreement, “Qualified Equity Financing” shall mean thesale of a minimum of $6,000,000 of equity securities of the Company.

 

**SECTION 4. **Term. This Agreementshall be effective from the date hereof and shall terminate on September 30,2006, unless terminated earlier pursuant to the default provisions of thisAgreement (the “Term”).

 

**SECTION 5. **Priority. The rightsof the Lender under the terms of this Agreement shall be junior to the Company’sexisting indebtedness.

 

**SECTION 6. **Personal Guaranty. Inorder to induce Lender to extend the Credit Facility to Borrower, the Company’sPresident, Mr. Rupert Galliers-Pratt absolutely and unconditionallyguarantees to Lender, to the fullest extent permitted by applicable law andpursuant to the terms of the Guaranty attached hereto as Exhibit C,the payment by the Company when due of all amounts owing under the CreditFacility and any and all other documents related thereto, including, withoutlimitation, all principal, interest, commitment fees, prepayment fees,expenses, professional fees and other amounts now or hereafter owing inconnection with the Credit Facility.

 

**SECTION 7. **Covenants of Borrower.The Borrower agrees and covenants as follows:

 

(a)                                  Paymentof Principal and Interest and Fees. The Borrower shall promptly pay whendue the principal of and interest on the indebtedness evidenced by the Noteissued under this Agreement, and all other sums secured by this Agreement,including but not limited to, the Commitment Fee.

 

(b)                                 CorporateExistence. The Borrower is a corporation duly organized and existing underthe laws of the State of Delaware and is duly qualified in every other state inwhich it is doing business except where the failure to be so qualifiedwould not have a Material Adverse 

 

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Effect on the Company. “MaterialAdverse Effect” means any circumstance, change in, or effect on the Companythat, individually or in the aggregate with any other similar circumstances,changes in, or effects on, the Company taken as a whole: (a) is, or isreasonably expected to be, materially adverse to the business, operations,assets, liabilities, employee relationships, customer or supplierrelationships, prospects, results of operations or the condition (financial orotherwise) of the Company taken as a whole or (b) is reasonably expectedto adversely affect the ability of the Company to operate or conduct theCompany’s business in the manner in which it is currently operated or conductedor proposed to be operated or conducted by the Company.

 

(c)                                  CorporateAuthority. The execution, delivery, and performance of this Agreement, andthe execution and payment of the Note issued pursuant to the terms hereof arewithin Borrower’s corporate powers, have been duly authorized, and are not incontravention of law or the terms of the Borrower’sarticles of incorporation and bylaws, or of any indenture, agreement, orundertaking to which the Borrower is a party or by which it is bound.

 

**SECTION 8**.** **NegativeCovenants. While loans are outstanding under this Agreement and the Note, theCompany shall not directly or indirectly:

 

(a)                                  Enter into any transaction not in theordinary and customary course of its business, including but not limited to thesale, lease, license, disposal, movement, relocation or transfer, whether bysale or otherwise, of any of its material assets other than sales of inventoryin the ordinary and customary course of its business, without the prior writtenconsent of Lender.

 

(b)                                 Make any distribution or pay any dividends(in cash or in stock) on, or purchase, acquire, redeem or retire any of itscapital stock, of any class, or other securities not held by Lender whether nowor hereafter outstanding.

 

**SECTION 9. **Taxes and Assessments.The Borrower will pay or cause to be paid promptly when due all taxes andassessments on this Agreement and the Note. The Borrower may, however, withholdpayment of any tax assessment or claim if a good faith dispute exists as to theobligation to pay.

 

**SECTION 10. **Application of Payments.Unless applicable law provides otherwise, all payments received by the Lenderfrom the Borrower under the Note and this Agreement shall be applied by theLender in the following order of priority: (i) interest payable on the Note in the manner provided therein; (ii) principalof the Note in the manner provided therein; and (iii) any other sumssecured by this Agreement in such order as the Lender, at the Lender’s option, may determine.

 

**SECTION 11. **Forbearance byLender Not a Waiver. Any forbearance by the Lender in exercising any rightor remedy hereunder, or otherwise afforded by applicable law, shall not be awaiver of or preclude the exercise of any right or remedy. The acceptance bythe Lender of payment of any sum secured by this Agreement after the due dateof such payment shall not be a waiver of the Lender’s right to either requireprompt payment when due of all other sums so secured or to declare a defaultfor failure to make prompt payment. The procurement of insurance or the paymentof taxes, rents or other liens or charges by the Lender shall not be a waiverof the 

 

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Lender’s right toaccelerate the maturity of the indebtedness secured by this Agreement, norshall the Lender’s receipt of any awards, proceeds or damages as provided inthis Agreement operate to cure or waive the Borrower’s default in payment ofsums secured by this Agreement.

 

**SECTION 12. **Events of Default. TheBorrower shall be in default under this Agreement when any of the followingevents or conditions occurs (each an “Event of Default”):

 

(a)                                  TheBorrower shall be in default under the Note beyond any applicable notice andcure period(s).

 

(b)                                 TheBorrower fails to comply with any term, obligation, covenant, or conditioncontained in this Agreement within ten (10) days after receipt of writtennotice from the Lender demanding such compliance.

 

(c)                                  Anywarranty, or representation made to the Lender by the Borrower under thisAgreement, proves to have been false in any material respect when made orfurnished.

 

(d)                                 Anyevent that results in acceleration of the maturity of any indebtedness ofBorrower in the outstanding principal amount of $10,000 or more, under anynote, indenture, contract, or agreement.

 

**SECTION 13. **Acceleration. At theoption of the Lender, upon an Event of Default, after any applicable noticeperiod, all principal and any unpaid interest due hereunder shall becomeimmediately due and payable.

 

**SECTION 14. **Borrower’s Insolvency.If the Borrower voluntarily files a petition under the federal Bankruptcy Act,as such Act may from time to time be amended, or under any similar orsuccessor federal statute relating to bankruptcy, insolvency, arrangements orreorganizations, or under any state bankruptcy or insolvency act, or files ananswer in an involuntary proceeding admitting insolvency or inability to paydebts, or if the Borrower is adjudged a bankrupt, or if a trustee or receiveris appointed for the Borrower’s property, or if the Borrower makes anassignment for the benefit of its creditors, or if there is an attachment,receivership, execution or other judicial seizure, then the Lender may, at theLender’s option, declare all of the sums secured by this Agreement to beimmediately due and payable without prior notice to the Borrower, and the Lendermay invoke any remedies permitted by this Agreement. Any attorneys’ feesand other expenses incurred by the Lender in connection with the Borrower’sbankruptcy or any of the other events described in this Section shall beadditional indebtedness of the Borrower secured by this Agreement.

 

**SECTION 15. **Waiver of Statute ofLimitations. Borrower hereby waives the right to assert any statute oflimitations as a bar to the enforcement of the lien of this Agreement or to anyaction brought to enforce the Note or any other obligation secured by thisAgreement.

 

**SECTION 16. **ExpenseReimbursement. The Company shallpay the reasonable fees and expenses of Indigo Ventures, LLC, the manager ofLender (the “Manager”), incurred in connection with this Credit Facilityincluding, but not limited to, all reasonable legal fees, all 

 

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expenses related to theformation of Indigo Investments I LLC and the filing of all necessary documentsand payment of all necessary fees (including local counsel fees) in connectionwith the Lender’s perfection of a first priority security interest pursuant tothe terms of the Guaranty.

 

**SECTION 17. **Remedies Cumulative.Each remedy provided in this Agreement is distinct and cumulative to all otherrights or remedies under this Agreement or afforded by law or equity, and may beexercised concurrently, independently, or successively, in any orderwhatsoever.

 

**SECTION 18. **Notices. Allnotices and other communications hereunder shall be in writing and shall bedeemed given if delivered personally, sent by overnight courier or telecopied(with a confirmatory copy sent by overnight courier) to the Parties at thefollowing addresses (or at such other address for a Party as shall be specifiedby like notice):

 

(a)                                  If to Borrower, to:

 

Vistula CommunicationsServices Inc.405 Park AvenueSuite 801New York, NY 10022Attention:Rupert Galliers-Pratt

 

witha copy to:

 

FoleyHoag LLP

155Seaport Boulevard

Boston,MA  02210

Attention:  Paul Bork, Esq.

 

(b)                                 If to Lender, to:

 

IndigoInvestments I LLC

c/o Indigo Ventures LLC

780Third Avenue

Suite 23B

New York, New York 10017

 

with a copy to:

 

Wollmuth Maher &Deutsch LLP

500 Fifth Avenue

New York, NY 10110

Attention: Rory M. Deutsch, Esq.

 

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**SECTION 19. **Interpretation.When a reference is made in this Agreement of a Section, such reference shallbe to a Section of this Agreement unless otherwise indicated, and thewords “hereof,” “herein” and “hereunder” and similar terms refer to thisAgreement as a whole and not to any particular provision of this Agreement,unless the context otherwise requires. The table of contents and headingscontained in this Agreement are for reference purposes only and shall notaffect in any way the meaning or interpretation of this Agreement. Whenever thewords “include,” “includes” or “including” are used in this Agreement, theyshall be deemed to be followed by the words “without limitation.”

 

**SECTION 20. **Counterparts. ThisAgreement may be executed in counterparts, each of which shall be deemed anoriginal agreement, but all of which together shall constitute one and the sameinstrument. Execution and delivery of this Agreement by facsimile transmission(including the delivery of documents in Adobe PDF format) shall constituteexecution and delivery of this Agreement for all purposes, with the same forceand effect as execution and delivery of an original manually signed copyhereof.

 

**SECTION 21. **Entire Agreement;No Third-Party Beneficiaries. This Agreement, the Subscription Agreement, theGuaranty and the Note, (i) constitutes the entire agreement between the Partieshereto and supersedes all prior agreements and****understandings,both written and oral, among the Parties with respect to the subject matterhereof and (ii) are not intended to confer upon any person other than the Partiesany rights or remedies hereunder.

 

**SECTION 22. **Governing Law. ThisAgreement shall be governed by, and construed in accordance with, the laws ofthe State of New York, regardless of the laws that might otherwise govern underapplicable principles of conflicts of laws thereof.

 

**SECTION 23. **Assignment. Neitherthis Agreement nor any of the rights, interests or obligations hereunder shallbe assigned by operation of law or otherwise by any of the Parties without theprior written consent of the other Party in its sole and absolute discretion,and any such purported assignment without the express prior written consent ofthe other Party shall be void ab initio. Subject to the preceding sentence,this Agreement shall be binding upon, inure to the benefit of, and beenforceable by, the Parties and their respective successors and assigns.

 

**SECTION 24. **Severability. Ifany term or other provision of this Agreement is invalid, illegal or incapableof being enforced by any rule of law, or public policy, all otherconditions and provisions of this Agreement shall nevertheless remain in fullforce and effect so long as the economic or legal substance of the transactionscontemplated hereby are not affected in any manner materially adverse to any Party.Upon such determination that any term or other provision is invalid, illegal orincapable of being enforced, the Parties shall negotiate in good faith tomodify this Agreement so as to effect he original intent of the Parties asclosely as possible in a mutually acceptable manner in order that thetransactions be consummated as originally contemplated to the fullest extentpossible.

 

**SECTION 25. **Consent toJurisdiction. In the event that any legal proceedings are commenced in anycourt with respect to any matter arising under this Agreement, the Partieshereto specifically consent and agree that the courts of the State of New Yorkand/or the Federal 

 

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Courts located in theState of New York shall have jurisdiction over each of the Parties hereto andover the subject matter of any such proceedings, and the venue of any suchaction shall be in New York County, New York and/or the U.S. District Court forthe Southern District of New York.

 

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IN WITNESS WHEREOF,Borrower and Lender have executed this Agreement as of the date first writtenabove.

 

 
|   | **INDIGO  INVESTMENTS I LLC**                   |
|--------|-------------------------------------------------|
|   |                                            |
|   | By: Indigo Ventures,  LLC, *as Manager*         |
|   |                                            |
|   | By:                                             |   | /s/ Eric Brachfeld |   |
|   | Name:                                           | Eric Brachfeld |   |
|   | Title:                                          | Managing Member |   |
|   |                                            |
|   | **VISTULA  COMMUNICATIONS SERVICES, INC.** |
|   |                                            |
|   | By:                                             |   | /s/ Rupert  Galliers-Pratt |   |
|   | Name:                                           | Rupert  Galliers-Pratt |   |
|   | Title:                                          | President &  Chief Executive Officer |   |

 

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