AS FILED WITH THE SECURITIES AND EXCHANGE COMMISSION ON MAY 24, 1999
                                                   REGISTRATION NO. 333-____

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

                       SECURITIES AND EXCHANGE COMMISSION
                             WASHINGTON, D.C. 20549

                                    FORM S-8

                          REGISTRATION STATEMENT UNDER
                           THE SECURITIES ACT OF 1933

                           EXCEL SWITCHING CORPORATION
             (Exact Name of Registrant as Specified in Its Charter)

          MASSACHUSETTS                                 04-2992806
(State or Other Jurisdiction of             (I.R.S. Employer Identification No.)
 Incorporation or Organization)

                             255 INDEPENDENCE DRIVE
                                HYANNIS, MA 02601
               (Address of Principal Executive Offices) (Zip Code)
                              --------------------

                          RASCOM, INC. 1996 STOCK PLAN
                            (Full Title of the Plan)
                              --------------------

                           CHRISTOPHER STAVROS, ESQ.
                        VICE PRESIDENT & GENERAL COUNSEL
                           EXCEL SWITCHING CORPORATION
                             255 INDEPENDENCE DRIVE
                          HYANNIS, MASSACHUSETTS 02601
                     (Name and Address of Agent For Service)

                                 (508) 862-3000
          (Telephone Number, Including Area Code, of Agent For Service)
                         ------------------------------

                                    Copy to:
    Christopher Stavros, Esq.                        John Hession, Esq.
   Excel SWITCHING Corporation                 TESTA, HURWITZ & THIBEAULT, LLP
      255 Independence Drive                  High Street Tower, 125 High Street
   Hyannis, Massachusetts 02601                  Boston, Massachusetts 02110
        (508) 862-3000                                  (617) 248-7000

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

<PAGE>
<TABLE>
<CAPTION>
                                               CALCULATION OF REGISTRATION FEE

===========================================================================================================================
                                                                                         PROPOSED
                                                                  PROPOSED MAXIMUM       MAXIMUM
                                                  AMOUNT TO BE     OFFERING PRICE       AGGREGATE          AMOUNT OF
     TITLE OF SECURITIES TO BE REGISTERED          REGISTERED       PER SHARE (1)     OFFERING PRICE  REGISTRATION FEE (2)
     ------------------------------------          ----------       -------------     --------------  --------------------

STOCK OPTION PROGRAM
<S>                                                     <C>           <C>            <C>                <C>
Common Stock (Par Value $.01 Per Share)                  8,901        $    2.25      $      20,027      $       5.57
Common Stock (Par Value $.01 Per Share)                  3,481        $    2.55      $       8,876      $       2.47
Common Stock (Par Value $.01 Per Share)                  1,112        $    3.04      $       3,380      $       0.94
Common Stock (Par Value $.01 Per Share)                  2,670        $    3.08      $       8,223      $       2.29
Common Stock (Par Value $.01 Per Share)                  2,715        $    3.14      $       8,525      $       2.37
Common Stock (Par Value $.01 Per Share)                  1,424        $    3.38      $       4,813      $       1.34
Common Stock (Par Value $.01 Per Share)                  1,068        $    3.41      $       3,641      $       1.01
Common Stock (Par Value $.01 Per Share)                    934        $    3.47      $       3,240      $       0.90
Common Stock (Par Value $.01 Per Share)                    715        $    3.60      $       2,574      $       0.72
Common Stock (Par Value $.01 Per Share)                    416        $    3.89      $       1,618      $       0.45
Common Stock (Par Value $.01 Per Share)                  4,895        $    4.09      $      20,020      $       5.57
Common Stock (Par Value $.01 Per Share)                    667        $    4.14      $       2,761      $       0.77
Common Stock (Par Value $.01 Per Share)                    890        $    4.16      $       3,702      $       1.03
Common Stock (Par Value $.01 Per Share)                    667        $    4.20      $       2,801      $       0.78
Common Stock (Par Value $.01 Per Share)                    890        $    4.22      $       3,755      $       1.04
Common Stock (Par Value $.01 Per Share)                  4,613        $    4.24      $      19,559      $       5.44
Common Stock (Par Value $.01 Per Share)                  3,063        $    4.27      $      13,079      $       3.64
Common Stock (Par Value $.01 Per Share)                  1,446        $    4.33      $       6,261      $       1.74
Common Stock (Par Value $.01 Per Share)                  9,551        $    4.50      $      42,979      $      11.95
Common Stock (Par Value $.01 Per Share)                  3,338        $    4.95      $      16,523      $       4.59
Common Stock (Par Value $.01 Per Share)                 11,254        $    6.75      $      75,964      $      21.12

TOTAL:                                                  64,710                                          $      75.73
-------------------------------------------
</TABLE>

(1)    Such shares are issuable upon exercise of outstanding options with fixed
       exercise prices. Pursuant to Rule 457(h), the aggregate offering price
       and the fee have been computed upon the basis of the price at which the
       options may be exercised. The offering price per share set forth for such
       shares is the exercise price per share at which such options are
       exercisable.

(2) Calculated pursuant to Section 6(b) of the Securities Act of 1933.

                                       2
<PAGE>



                                     PART I

              INFORMATION REQUIRED IN THE SECTION 10(A) PROSPECTUS

ITEM 1.  PLAN INFORMATION.

         The documents containing the information specified in this Item 1 will
be sent or given to employees, directors and others as specified by Rule
428(b)(1). In accordance with the rules and regulations of the Securities and
Exchange Commission (the "Commission") and the instructions to Form S-8, such
documents are not being filed with the Commission either as part of this
Registration Statement or as prospectuses or prospectus supplements pursuant to
Rule 424.

ITEM 2.  REGISTRANT INFORMATION AND EMPLOYEE PLAN ANNUAL INFORMATION.

         The documents containing the information specified in this Item 2 will
be sent or given to employees, directors or others as specified by Rule
428(b)(1). In accordance with the rules and regulations of the Commission and
the instructions to Form S-8, such documents are not being filed with the
Commission either as part of this Registration Statement or as prospectuses or
prospectus supplements pursuant to Rule 424.

                                     PART II

               INFORMATION REQUIRED IN THE REGISTRATION STATEMENT

ITEM 3.  INCORPORATION OF DOCUMENTS BY REFERENCE.

         The following documents filed by the Registrant with the Commission
pursuant to the Securities Exchange Act of 1934, as amended (the "Exchange Act")
are incorporated by reference in this Registration Statement:

         (a)   The Registrant's Annual Report on Form 10-K for the fiscal year
               ended December 31, 1998, filed pursuant to the Exchange Act which
               contains audited financial statements for the fiscal year ended
               December 31, 1998.

         (b)   The Registrant's Current Report on Form 8-K filed on April 23,
               1999 pursuant to the Exchange Act.

         (c)   The Registrant's Quarterly Report on Form 10-Q for the fiscal
               quarter ended March 31, 1999, filed on May 18, 1999 pursuant to
               the Exchange Act.

         (d)   The section entitled "Description of Registrant's Securities to
               be Registered," contained in the Registrant's Registration
               Statement on Form 8-A, filed on October 23, 1997 pursuant to
               Section 12 of the Exchange Act.

         All documents subsequently filed with the Commission by the Registrant
pursuant to Sections 13(a), 13(c), 14 and 15(d) of the Exchange Act, prior to
the filing of a post-effective amendment which indicates that all securities
offered herein have been sold or which deregisters all securities then remaining
unsold, shall be deemed to be incorporated by reference in this Registration
Statement and to be a part hereof from the date of filing of such documents.




                                       3
<PAGE>

ITEM 4.  DESCRIPTION OF SECURITIES.

         Not applicable.

ITEM 5.  INTEREST OF NAMED EXPERTS AND COUNSEL.

         Not applicable.

ITEM 6.  INDEMNIFICATION OF DIRECTORS AND OFFICERS.

         The Registrant is required by its Restated By-laws and the Restated
Articles of Incorporation generally to indemnify any director, officer or
employee against all expenses and liabilities reasonably incurred by or imposed
upon such person in connection with any legal action in which such person is
involved by reason of such person's position with the Registrant unless such
person shall have been finally adjudicated in any action, suit or proceeding not
to have acted in good faith in the reasonable belief that such person's action
was in the best interests of the Registrant. The Registrant may pay expenses
incurred by any such person in defending a civil or criminal action or
proceeding in advance of the final disposition of such action upon the
Registrant's receipt of the undertaking of such person to repay such amount if
such person shall be adjudicated not to be entitled to indemnification.

         The Registrant's Restated Articles of Incorporation include a provision
limiting the personal liability of a director of the Registrant to its
stockholders for monetary damages for breaches of their fiduciary duty except
(i) for any breach of the director's duty of loyalty to the Registrant or its
stockholders, (ii) for acts or omissions not in good faith or which involve
intentional misconduct or a knowing violation of law, (iii) under section
sixty-one or sixty-two of Chapter 156B of the Massachusetts General Laws, or
(iv) for any transaction from which the director derived an improper benefit.

         The Registrant maintains directors and officers liability insurance for
the benefit of its directors and certain of its officers.

ITEM 7.  EXEMPTION FROM REGISTRATION CLAIMED.

         Not applicable.

ITEM 8.  EXHIBITS.

Exhibit No.       Description of Exhibit
-----------       ----------------------

   4.1            Restated Articles of Incorporation of the Registrant (filed as
                  Exhibit 3.1 to the Registrant's Annual Report on Form 10-K on
                  March 31, 1999 and incorporated herein by reference).

   4.2            Restated By-Laws of the Registrant (filed as Exhibit 3.2 to
                  the Registrant's Annual Report filed on Form 10-K on March 31,
                  1999 and incorporated herein by reference).

   4.3            RAScom 1996 Stock Plan

   5.1            Opinion of Testa, Hurwitz & Thibeault, LLP

   23.1           Consent of Arthur Andersen LLP

   23.2           Consent of Testa, Hurwitz & Thibeault, LLP (included in
                  Exhibit 5.1)



                                       4
<PAGE>

   24.1           Power of Attorney (included as part of the signature page to
                  this Registration Statement)

ITEM 9.  UNDERTAKINGS.

         (a)      The undersigned Registrant hereby undertakes:

                  (1) To file, during any period in which offers or sales are
                  being made, a post-effective amendment to this registration
                  statement:

                      (i) To include any prospectus required by Section 10(a)(3)
                      of the Securities Act of 1933;

                      (ii) To reflect in the prospectus any facts or events
                      arising after the effective date of the registration
                      statement (or the most recent post-effective amendment
                      thereof) which, individually or in the aggregate,
                      represent a fundamental change in the information set
                      forth in the registration statement. Notwithstanding the
                      foregoing, any increase or decrease in volume of
                      securities offered (if the total dollar value of
                      securities offered would not exceed that which was
                      registered) and any deviation from the low or high end of
                      the estimated maximum offering range may be reflected in
                      the form of prospectus filed with the Commission pursuant
                      to Rule 424(b) if, in the aggregate, the changes in volume
                      and price represent no more than a 20 percent change in
                      the maximum aggregate offering price set forth in the
                      "Calculation of Registration Fee" table in the effective
                      registration statement;

                      (iii) To include any material information with respect to
                      the plan of distribution not previously disclosed in the
                      registration statement or any material change to such
                      information in the registration statement;

                  (2) That, for the purpose of determining any liability under
                  the Securities Act of 1933, each such post-effective amendment
                  shall be deemed to be a new registration statement relating to
                  the securities offered therein, and the offering of such
                  securities at that time shall be deemed to be the initial bona
                  fide offering thereof;

                  (3) To remove from registration by means of a post-effective
                  amendment any of the securities being registered which remain
                  unsold at the termination of the offering.

                  (4) If the registrant is a foreign private issuer, to file a
                  post-effective amendment to the registration statement to
                  include any financial statements required by Rule 3-19 of this
                  chapter at the start of any delayed offering or throughout a
                  continuous offering. Financial statements and information
                  otherwise required by Section 10(a)(3) of the Act need not be
                  furnished, provided, that the registrant includes in the
                  prospectus, by means of a post-effective amendment, financial
                  statements required pursuant to this paragraph (a)(4) and
                  other information necessary to ensure that all other
                  information in the prospectus is at least as current as the
                  date of those financial statements. Notwithstanding the
                  foregoing, with respect to registration statements on Form
                  F-3, a post-effective amendment need not be filed to include
                  financial statements and information required by Section
                  10(a)(3) of the Act or Rule 3-19 of this chapter if such
                  financial statements and information are contained in periodic
                  reports filed with or furnished to the Commission by the
                  registrant pursuant to Section 13 or Section 15(d) of the
                  Securities Exchange Act of 1934 that are incorporated by
                  reference in the Form F-3.



                                       5
<PAGE>

         (b) The undersigned Registrant hereby undertakes that, for purposes of
         determining any liability under the Securities Act of 1933, each filing
         of the Registrant's annual report pursuant to Section 13(a) or Section
         15(d) of the Securities Exchange Act of 1934 (and, where applicable,
         each filing of an employee benefit plan's annual report pursuant to
         Section 15(d) of the Securities Exchange Act of 1934) that is
         incorporated by reference in the registration statement shall be deemed
         to be a new registration statement relating to the securities offered
         therein, and the offering of such securities at that time shall be
         deemed to be the initial bona fide offering thereof.

         (c) Insofar as indemnification for liabilities arising under the
         Securities Act of 1933 may be permitted to directors, officers and
         controlling persons of the Registrant pursuant to the foregoing
         provisions, or otherwise, the Registrant has been advised that in the
         opinion of the Securities and Exchange Commission such indemnification
         is against public policy as expressed in the Act and is, therefore,
         unenforceable. In the event that a claim for indemnification against
         such liabilities (other than the payment by the Registrant of expenses
         incurred or paid by a director, officer or controlling person of the
         Registrant in the successful defense of any action, suit or proceeding)
         is asserted by such director, officer or controlling person in
         connection with the securities being registered, the Registrant will,
         unless in the opinion of its counsel the matter has been settled by
         controlling precedent, submit to a court of appropriate jurisdiction
         the question whether such indemnification by it is against public
         policy as expressed in the Act and will be governed by the final
         adjudication of such issue.





                                       6
<PAGE>

                                   SIGNATURES

      Pursuant to the requirements of the Securities Act of 1933, the Registrant
certifies that it has reasonable grounds to believe that it meets all of the
requirements for filing on Form S-8 and has duly caused this Registration
Statement to be signed on its behalf by the undersigned, thereunto duly
authorized, in the City of Hyannis, Commonwealth of Massachusetts, on the 24th
day of May, 1999.

                                    EXCEL SWITCHING CORPORATION

                                    By:  /s/ Robert P. Madonna
                                         ---------------------------------
                                         Robert P. Madonna
                                         President, Chief Executive Officer
                                         and Chairman of the Board of Directors

                        POWER OF ATTORNEY AND SIGNATURES

      We, the undersigned officers and directors of Excel Switching Corporation,
hereby severally constitute and appoint Christopher Stavros and Stephen S.
Galliker and each of them, with full power to act without the other, his true
and lawful attorney-in-fact and agent, with full power of substitution and
resubstitution, for him and in his name, place and stead in any and all
capacities (until revoked in writing) to sign all amendments (including
post-effective amendments) to this Registration Statement on Form S-8 of Excel
Switching Corporation, and to file the same, with all exhibits thereto and other
documents in connection therewith, with the Securities and Exchange Commission,
granting unto said attorneys-in-fact and agents, and each of them, full power
and authority to do and perform each and every act and thing requisite and
necessary fully to all intents and purposes as he might or could do in person
thereby ratifying and confirming all that said attorneys-in-fact and agents or
any of them, or their or his substitute, may lawfully do or cause to be done by
virtue hereof.

      Pursuant to the requirements of the Securities Act of 1933, this
Registration Statement has been signed below by the following persons in the
capacities and on the dates indicated.

<TABLE>
<CAPTION>
      Signature                               Title(s)                                      Date
<S>                                           <C>                                           <C>
/s/ Robert P. Madonna                         President, Chief Executive Officer            May 24, 1999
------------------------------------          and Chairman of the Board of Directors
Robert P. Madonna                             (Principal Executive Officer)

/s/ Stephen S. Galliker                       Vice President Finance and                    May 24, 1999
------------------------------------          Administration and Chief Financial
Stephen S. Galliker                           Officer
                                              (Principal Financial and Accounting Officer)

/s/ Christopher Stavros                       Director, Vice President, General             May 24, 1999
------------------------------------          Counsel and Clerk
Christopher Stavros

/s/ Edward L. Breslow                         Director                                      May 24, 1999
------------------------------------
Edward L. Breslow

/s/ John Loughlin                             Director                                      May 24, 1999
------------------------------------
John Loughlin

</TABLE>

                                       7
<PAGE>

                                  EXHIBIT INDEX



Exhibit No.       Description
-----------       -----------

   4.1            Restated Articles of Incorporation of the Registrant (filed as
                  Exhibit 3.1 to the Registrant's Annual Report on Form 10-K on
                  March 31, 1999 and incorporated herein by reference).

   4.2            Restated By-Laws of the Registrant (filed as Exhibit 3.2 to
                  the Registrant's Annual Report filed on Form 10-K on March 31,
                  1999 and incorporated herein by reference).

   4.3            RAScom 1996 Stock Plan

   5.1            Opinion of Testa, Hurwitz & Thibeault, LLP

   23.1           Consent of Arthur Andersen LLP

   23.2           Consent of Testa, Hurwitz & Thibeault, LLP (included in
                  Exhibit 5.1)

   24.1           Power of Attorney (included as part of the signature page to
                  this Registration Statement)
[{"type": "S-8", "sequence": "1", "description": "FORM S-8", "secsgml_size_bytes": 23011}]
{"company-data": {"conformed-name": "EXCEL SWITCHING CORP", "cik": "0001036261", "assigned-sic": "3669", "irs-number": "042992806", "state-of-incorporation": "MA", "fiscal-year-end": "1231"}, "filing-values": {"form-type": "S-8", "act": "33", "file-number": "333-79197", "film-number": "99633421"}, "business-address": {"street1": "255 INDEPENDENCE DR", "city": "HYANNIS", "state": "MA", "zip": "02601", "phone": "5088623000"}, "mail-address": {"street1": "255 INDEPENDENCE DR", "city": "HYANNIS", "state": "MA", "zip": "02601"}, "former-company": {"former-conformed-name": "EXCEL INC", "date-changed": "19970325"}}
AS FILED WITH THE SECURITIES AND EXCHANGE COMMISSION ON MAY 24, 1999
                                                   REGISTRATION NO. 333-____

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

                       SECURITIES AND EXCHANGE COMMISSION
                             WASHINGTON, D.C. 20549

                                    FORM S-8

                          REGISTRATION STATEMENT UNDER
                           THE SECURITIES ACT OF 1933

                           EXCEL SWITCHING CORPORATION
             (Exact Name of Registrant as Specified in Its Charter)

          MASSACHUSETTS                                 04-2992806
(State or Other Jurisdiction of             (I.R.S. Employer Identification No.)
 Incorporation or Organization)

                             255 INDEPENDENCE DRIVE
                                HYANNIS, MA 02601
               (Address of Principal Executive Offices) (Zip Code)
                              --------------------

                          RASCOM, INC. 1996 STOCK PLAN
                            (Full Title of the Plan)
                              --------------------

                           CHRISTOPHER STAVROS, ESQ.
                        VICE PRESIDENT & GENERAL COUNSEL
                           EXCEL SWITCHING CORPORATION
                             255 INDEPENDENCE DRIVE
                          HYANNIS, MASSACHUSETTS 02601
                     (Name and Address of Agent For Service)

                                 (508) 862-3000
          (Telephone Number, Including Area Code, of Agent For Service)
                         ------------------------------

                                    Copy to:
    Christopher Stavros, Esq.                        John Hession, Esq.
   Excel SWITCHING Corporation                 TESTA, HURWITZ & THIBEAULT, LLP
      255 Independence Drive                  High Street Tower, 125 High Street
   Hyannis, Massachusetts 02601                  Boston, Massachusetts 02110
        (508) 862-3000                                  (617) 248-7000

================================================================================
CALCULATION OF REGISTRATION FEE

===========================================================================================================================
                                                                                         PROPOSED
                                                                  PROPOSED MAXIMUM       MAXIMUM
                                                  AMOUNT TO BE     OFFERING PRICE       AGGREGATE          AMOUNT OF
     TITLE OF SECURITIES TO BE REGISTERED          REGISTERED       PER SHARE (1)     OFFERING PRICE  REGISTRATION FEE (2)
     ------------------------------------          ----------       -------------     --------------  --------------------

STOCK OPTION PROGRAM
Common Stock (Par Value $.01 Per Share)                  8,901        $    2.25      $      20,027      $       5.57
Common Stock (Par Value $.01 Per Share)                  3,481        $    2.55      $       8,876      $       2.47
Common Stock (Par Value $.01 Per Share)                  1,112        $    3.04      $       3,380      $       0.94
Common Stock (Par Value $.01 Per Share)                  2,670        $    3.08      $       8,223      $       2.29
Common Stock (Par Value $.01 Per Share)                  2,715        $    3.14      $       8,525      $       2.37
Common Stock (Par Value $.01 Per Share)                  1,424        $    3.38      $       4,813      $       1.34
Common Stock (Par Value $.01 Per Share)                  1,068        $    3.41      $       3,641      $       1.01
Common Stock (Par Value $.01 Per Share)                    934        $    3.47      $       3,240      $       0.90
Common Stock (Par Value $.01 Per Share)                    715        $    3.60      $       2,574      $       0.72
Common Stock (Par Value $.01 Per Share)                    416        $    3.89      $       1,618      $       0.45
Common Stock (Par Value $.01 Per Share)                  4,895        $    4.09      $      20,020      $       5.57
Common Stock (Par Value $.01 Per Share)                    667        $    4.14      $       2,761      $       0.77
Common Stock (Par Value $.01 Per Share)                    890        $    4.16      $       3,702      $       1.03
Common Stock (Par Value $.01 Per Share)                    667        $    4.20      $       2,801      $       0.78
Common Stock (Par Value $.01 Per Share)                    890        $    4.22      $       3,755      $       1.04
Common Stock (Par Value $.01 Per Share)                  4,613        $    4.24      $      19,559      $       5.44
Common Stock (Par Value $.01 Per Share)                  3,063        $    4.27      $      13,079      $       3.64
Common Stock (Par Value $.01 Per Share)                  1,446        $    4.33      $       6,261      $       1.74
Common Stock (Par Value $.01 Per Share)                  9,551        $    4.50      $      42,979      $      11.95
Common Stock (Par Value $.01 Per Share)                  3,338        $    4.95      $      16,523      $       4.59
Common Stock (Par Value $.01 Per Share)                 11,254        $    6.75      $      75,964      $      21.12

TOTAL:                                                  64,710                                          $      75.73
-------------------------------------------
(1)    Such shares are issuable upon exercise of outstanding options with fixed
       exercise prices. Pursuant to Rule 457(h), the aggregate offering price
       and the fee have been computed upon the basis of the price at which the
       options may be exercised. The offering price per share set forth for such
       shares is the exercise price per share at which such options are
       exercisable.

(2) Calculated pursuant to Section 6(b) of the Securities Act of 1933.

                                       2
PART I

              INFORMATION REQUIRED IN THE SECTION 10(A) PROSPECTUS

ITEM 1.  PLAN INFORMATION.

         The documents containing the information specified in this Item 1 will
be sent or given to employees, directors and others as specified by Rule
428(b)(1). In accordance with the rules and regulations of the Securities and
Exchange Commission (the "Commission") and the instructions to Form S-8, such
documents are not being filed with the Commission either as part of this
Registration Statement or as prospectuses or prospectus supplements pursuant to
Rule 424.

ITEM 2.  REGISTRANT INFORMATION AND EMPLOYEE PLAN ANNUAL INFORMATION.

         The documents containing the information specified in this Item 2 will
be sent or given to employees, directors or others as specified by Rule
428(b)(1). In accordance with the rules and regulations of the Commission and
the instructions to Form S-8, such documents are not being filed with the
Commission either as part of this Registration Statement or as prospectuses or
prospectus supplements pursuant to Rule 424.

                                     PART II

               INFORMATION REQUIRED IN THE REGISTRATION STATEMENT

ITEM 3.  INCORPORATION OF DOCUMENTS BY REFERENCE.

         The following documents filed by the Registrant with the Commission
pursuant to the Securities Exchange Act of 1934, as amended (the "Exchange Act")
are incorporated by reference in this Registration Statement:

         (a)   The Registrant's Annual Report on Form 10-K for the fiscal year
               ended December 31, 1998, filed pursuant to the Exchange Act which
               contains audited financial statements for the fiscal year ended
               December 31, 1998.

         (b)   The Registrant's Current Report on Form 8-K filed on April 23,
               1999 pursuant to the Exchange Act.

         (c)   The Registrant's Quarterly Report on Form 10-Q for the fiscal
               quarter ended March 31, 1999, filed on May 18, 1999 pursuant to
               the Exchange Act.

         (d)   The section entitled "Description of Registrant's Securities to
               be Registered," contained in the Registrant's Registration
               Statement on Form 8-A, filed on October 23, 1997 pursuant to
               Section 12 of the Exchange Act.

         All documents subsequently filed with the Commission by the Registrant
pursuant to Sections 13(a), 13(c), 14 and 15(d) of the Exchange Act, prior to
the filing of a post-effective amendment which indicates that all securities
offered herein have been sold or which deregisters all securities then remaining
unsold, shall be deemed to be incorporated by reference in this Registration
Statement and to be a part hereof from the date of filing of such documents.

                                       3
ITEM 4.  DESCRIPTION OF SECURITIES.

         Not applicable.

ITEM 5.  INTEREST OF NAMED EXPERTS AND COUNSEL.

         Not applicable.

ITEM 6.  INDEMNIFICATION OF DIRECTORS AND OFFICERS.

         The Registrant is required by its Restated By-laws and the Restated
Articles of Incorporation generally to indemnify any director, officer or
employee against all expenses and liabilities reasonably incurred by or imposed
upon such person in connection with any legal action in which such person is
involved by reason of such person's position with the Registrant unless such
person shall have been finally adjudicated in any action, suit or proceeding not
to have acted in good faith in the reasonable belief that such person's action
was in the best interests of the Registrant. The Registrant may pay expenses
incurred by any such person in defending a civil or criminal action or
proceeding in advance of the final disposition of such action upon the
Registrant's receipt of the undertaking of such person to repay such amount if
such person shall be adjudicated not to be entitled to indemnification.

         The Registrant's Restated Articles of Incorporation include a provision
limiting the personal liability of a director of the Registrant to its
stockholders for monetary damages for breaches of their fiduciary duty except
(i) for any breach of the director's duty of loyalty to the Registrant or its
stockholders, (ii) for acts or omissions not in good faith or which involve
intentional misconduct or a knowing violation of law, (iii) under section
sixty-one or sixty-two of Chapter 156B of the Massachusetts General Laws, or
(iv) for any transaction from which the director derived an improper benefit.

         The Registrant maintains directors and officers liability insurance for
the benefit of its directors and certain of its officers.

ITEM 7.  EXEMPTION FROM REGISTRATION CLAIMED.

         Not applicable.

ITEM 8.  EXHIBITS.

Exhibit No.       Description of Exhibit
-----------       ----------------------

   4.1            Restated Articles of Incorporation of the Registrant (filed as
                  Exhibit 3.1 to the Registrant's Annual Report on Form 10-K on
                  March 31, 1999 and incorporated herein by reference).

   4.2            Restated By-Laws of the Registrant (filed as Exhibit 3.2 to
                  the Registrant's Annual Report filed on Form 10-K on March 31,
                  1999 and incorporated herein by reference).

   4.3            RAScom 1996 Stock Plan

   5.1            Opinion of Testa, Hurwitz & Thibeault, LLP

   23.1           Consent of Arthur Andersen LLP

   23.2           Consent of Testa, Hurwitz & Thibeault, LLP (included in
                  Exhibit 5.1)

                                       4
24.1           Power of Attorney (included as part of the signature page to
                  this Registration Statement)

ITEM 9.  UNDERTAKINGS.

         (a)      The undersigned Registrant hereby undertakes:

                  (1) To file, during any period in which offers or sales are
                  being made, a post-effective amendment to this registration
                  statement:

                      (i) To include any prospectus required by Section 10(a)(3)
                      of the Securities Act of 1933;

                      (ii) To reflect in the prospectus any facts or events
                      arising after the effective date of the registration
                      statement (or the most recent post-effective amendment
                      thereof) which, individually or in the aggregate,
                      represent a fundamental change in the information set
                      forth in the registration statement. Notwithstanding the
                      foregoing, any increase or decrease in volume of
                      securities offered (if the total dollar value of
                      securities offered would not exceed that which was
                      registered) and any deviation from the low or high end of
                      the estimated maximum offering range may be reflected in
                      the form of prospectus filed with the Commission pursuant
                      to Rule 424(b) if, in the aggregate, the changes in volume
                      and price represent no more than a 20 percent change in
                      the maximum aggregate offering price set forth in the
                      "Calculation of Registration Fee" table in the effective
                      registration statement;

                      (iii) To include any material information with respect to
                      the plan of distribution not previously disclosed in the
                      registration statement or any material change to such
                      information in the registration statement;

                  (2) That, for the purpose of determining any liability under
                  the Securities Act of 1933, each such post-effective amendment
                  shall be deemed to be a new registration statement relating to
                  the securities offered therein, and the offering of such
                  securities at that time shall be deemed to be the initial bona
                  fide offering thereof;

                  (3) To remove from registration by means of a post-effective
                  amendment any of the securities being registered which remain
                  unsold at the termination of the offering.

                  (4) If the registrant is a foreign private issuer, to file a
                  post-effective amendment to the registration statement to
                  include any financial statements required by Rule 3-19 of this
                  chapter at the start of any delayed offering or throughout a
                  continuous offering. Financial statements and information
                  otherwise required by Section 10(a)(3) of the Act need not be
                  furnished, provided, that the registrant includes in the
                  prospectus, by means of a post-effective amendment, financial
                  statements required pursuant to this paragraph (a)(4) and
                  other information necessary to ensure that all other
                  information in the prospectus is at least as current as the
                  date of those financial statements. Notwithstanding the
                  foregoing, with respect to registration statements on Form
                  F-3, a post-effective amendment need not be filed to include
                  financial statements and information required by Section
                  10(a)(3) of the Act or Rule 3-19 of this chapter if such
                  financial statements and information are contained in periodic
                  reports filed with or furnished to the Commission by the
                  registrant pursuant to Section 13 or Section 15(d) of the
                  Securities Exchange Act of 1934 that are incorporated by
                  reference in the Form F-3.

                                       5
(b) The undersigned Registrant hereby undertakes that, for purposes of
         determining any liability under the Securities Act of 1933, each filing
         of the Registrant's annual report pursuant to Section 13(a) or Section
         15(d) of the Securities Exchange Act of 1934 (and, where applicable,
         each filing of an employee benefit plan's annual report pursuant to
         Section 15(d) of the Securities Exchange Act of 1934) that is
         incorporated by reference in the registration statement shall be deemed
         to be a new registration statement relating to the securities offered
         therein, and the offering of such securities at that time shall be
         deemed to be the initial bona fide offering thereof.

         (c) Insofar as indemnification for liabilities arising under the
         Securities Act of 1933 may be permitted to directors, officers and
         controlling persons of the Registrant pursuant to the foregoing
         provisions, or otherwise, the Registrant has been advised that in the
         opinion of the Securities and Exchange Commission such indemnification
         is against public policy as expressed in the Act and is, therefore,
         unenforceable. In the event that a claim for indemnification against
         such liabilities (other than the payment by the Registrant of expenses
         incurred or paid by a director, officer or controlling person of the
         Registrant in the successful defense of any action, suit or proceeding)
         is asserted by such director, officer or controlling person in
         connection with the securities being registered, the Registrant will,
         unless in the opinion of its counsel the matter has been settled by
         controlling precedent, submit to a court of appropriate jurisdiction
         the question whether such indemnification by it is against public
         policy as expressed in the Act and will be governed by the final
         adjudication of such issue.

                                       6
SIGNATURES

      Pursuant to the requirements of the Securities Act of 1933, the Registrant
certifies that it has reasonable grounds to believe that it meets all of the
requirements for filing on Form S-8 and has duly caused this Registration
Statement to be signed on its behalf by the undersigned, thereunto duly
authorized, in the City of Hyannis, Commonwealth of Massachusetts, on the 24th
day of May, 1999.

                                    EXCEL SWITCHING CORPORATION

                                    By:  /s/ Robert P. Madonna
                                         ---------------------------------
                                         Robert P. Madonna
                                         President, Chief Executive Officer
                                         and Chairman of the Board of Directors

                        POWER OF ATTORNEY AND SIGNATURES

      We, the undersigned officers and directors of Excel Switching Corporation,
hereby severally constitute and appoint Christopher Stavros and Stephen S.
Galliker and each of them, with full power to act without the other, his true
and lawful attorney-in-fact and agent, with full power of substitution and
resubstitution, for him and in his name, place and stead in any and all
capacities (until revoked in writing) to sign all amendments (including
post-effective amendments) to this Registration Statement on Form S-8 of Excel
Switching Corporation, and to file the same, with all exhibits thereto and other
documents in connection therewith, with the Securities and Exchange Commission,
granting unto said attorneys-in-fact and agents, and each of them, full power
and authority to do and perform each and every act and thing requisite and
necessary fully to all intents and purposes as he might or could do in person
thereby ratifying and confirming all that said attorneys-in-fact and agents or
any of them, or their or his substitute, may lawfully do or cause to be done by
virtue hereof.

      Pursuant to the requirements of the Securities Act of 1933, this
Registration Statement has been signed below by the following persons in the
capacities and on the dates indicated.
Signature                               Title(s)                                      Date
/s/ Robert P. Madonna                         President, Chief Executive Officer            May 24, 1999
------------------------------------          and Chairman of the Board of Directors
Robert P. Madonna                             (Principal Executive Officer)

/s/ Stephen S. Galliker                       Vice President Finance and                    May 24, 1999
------------------------------------          Administration and Chief Financial
Stephen S. Galliker                           Officer
                                              (Principal Financial and Accounting Officer)

/s/ Christopher Stavros                       Director, Vice President, General             May 24, 1999
------------------------------------          Counsel and Clerk
Christopher Stavros

/s/ Edward L. Breslow                         Director                                      May 24, 1999
------------------------------------
Edward L. Breslow

/s/ John Loughlin                             Director                                      May 24, 1999
------------------------------------
John Loughlin
7
EXHIBIT INDEX

Exhibit No.       Description
-----------       -----------

   4.1            Restated Articles of Incorporation of the Registrant (filed as
                  Exhibit 3.1 to the Registrant's Annual Report on Form 10-K on
                  March 31, 1999 and incorporated herein by reference).

   4.2            Restated By-Laws of the Registrant (filed as Exhibit 3.2 to
                  the Registrant's Annual Report filed on Form 10-K on March 31,
                  1999 and incorporated herein by reference).

   4.3            RAScom 1996 Stock Plan

   5.1            Opinion of Testa, Hurwitz & Thibeault, LLP

   23.1           Consent of Arthur Andersen LLP

   23.2           Consent of Testa, Hurwitz & Thibeault, LLP (included in
                  Exhibit 5.1)

   24.1           Power of Attorney (included as part of the signature page to
                  this Registration Statement)