EXHIBIT 99.3
 
                                                              September 15, 1997
 
Robert P. Madonna, President
Excel Switching Corporation
255 Independence Drive
Hyannis, MA 02601
 
Dear Mr. Madonna:
 
  I hereby consent to be named as a nominee for election as a director of Excel
Switching Corporation in its Registration Statement on Form S-1 (and in the
Prospectus forming a part hereof) and in any and all amendments thereto.
 
                                          Very truly yours,
 
                                          /s/ John Loughlin
 
                                          John Loughlin
 
Dated: September 15, 1997