\begin{thebibliography}{1}

\bibitem{draft-ietf-iptel-tgrep}
M.~B. et. al, \htmladdnormallink{``A telephony gateway {REgistration} protocol
  {(TGREP)},''}{http://www.ietf.org/internet-drafts/draft-ietf-iptel-tgrep-01.%
txt} internet draft, Internet Engineering Task Force, Mar. 2003.
\newblock Work in progress.

\bibitem{draft-zhao-iptel-gwloc-slp}
W.~Zhao and H.~Schulzrinne, \htmladdnormallink{``Locating {IP-to-Public}
  switched telephone network {(PSTN)} telephony gateways via
  {SLP},''}{http://www.ietf.org/internet-drafts/draft-zhao-iptel-gwloc-slp-05.%
txt} internet draft, Internet Engineering Task Force, Aug. 2002.
\newblock Work in progress.

\bibitem{draft-ietf-sip-session-timer}
S.~Donovan and J.~Rosenberg, \htmladdnormallink{``Session initiation protocol
  extension for session
  timer,''}{http://www.ietf.org/internet-drafts/draft-ietf-sip-session-timer-1%
0.txt} internet draft, Internet Engineering Task Force, Nov. 2002.
\newblock Work in progress.

\bibitem{draft-ietf-sipping-overlap}
G.~Camarillo {\em et~al.}, \htmladdnormallink{``Mapping of of integrated
  services digital network {(ISUP)} overlap signalling to the session
  initiation
  protocol,''}{http://www.ietf.org/internet-drafts/draft-ietf-sipping-overlap-%
04.txt} internet draft, Internet Engineering Task Force, Feb. 2003.
\newblock Work in progress.

\end{thebibliography}
