\begin{thebibliography}{1}

\bibitem{rfc2119}
S.~Bradner, ``Key words for use in {RFCs} to indicate requirement levels,''
  Request for Comments 2119, Internet Engineering Task Force, Mar. 1997.

\bibitem{rfc2543}
M.~Handley, H.~Schulzrinne, E.~Schooler, and J.~Rosenberg, ``{SIP:} session
  initiation protocol,'' Request for Comments 2543, Internet Engineering Task
  Force, Mar. 1999.

\bibitem{rfc2326}
H.~Schulzrinne, A.~Rao, and R.~Lanphier, ``Real time streaming protocol
  {(RTSP)},'' Request for Comments 2326, Internet Engineering Task Force, Apr.
  1998.

\bibitem{rfc2617}
J.~Franks, P.~Hallam-Baker, J.~Hostetler, S.~Lawrence, P.~Leach, A.~Luotonen,
  and L.~Stewart, ``{HTTP} authentication: Basic and digest access
  authentication,'' Request for Comments 2617, Internet Engineering Task Force,
  June 1999.

\bibitem{draft-lennox-sip-cgi}
J.~Lennox, J.~Rosenberg, and H.~Schulzrinne, ``Common gateway interface for
  {SIP},'' {Internet Draft}, Internet Engineering Task Force, May 1999.
\newblock Work in progress.

\bibitem{draft-ietf-iptel-cpl}
J.~Lennox and H.~Schulzrinne, ``{CPL:} a language for user control of internet
  telephony services,'' {Internet Draft}, Internet Engineering Task Force, Mar.
  1999.
\newblock Work in progress.

\end{thebibliography}
