poisoning) or by selectively dropping responses.
Another solution prohibits proxies from forwarding late responses.
Without this change, an attacker could easily forge messages which
appear to be late responses. All proxies compliant with RFC 3261 are
required to forward these responses, wasting bandwidth and CPU and
potentially overwhelming target User Agents (especially those with
low speed connections).
3. Acknowledgements
This document captures many conversations about non-INVITE issues.
Significant contributers include Ben Campbell, Gonzalo Camarillo,
Steve Donovan, Rohan Mahy, Dan Petrie, Adam Roach, Jonathan
Rosenberg, and Dean Willis.
4. Informative References
[1] Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston, A.,
Peterson, J., Sparks, R., Handley, M., and E. Schooler, "SIP:
Session Initiation Protocol", RFC 3261, June 2002.
[2] Rosenberg, J. and H. Schulzrinne, "Session Initiation Protocol
(SIP): Locating SIP Servers", RFC 3263, June 2002.
[3] Gulbrandsen, A., Vixie, P., and L. Esibov, "A DNS RR for
specifying the location of services (DNS SRV)", RFC 2782,
February 2000.
[4] Sparks, R., "Actions Addressing Identified Issues with the
Session Initiation Protocol’s (SIP) Non-INVITE Transaction", RFC
4320, January 2006.
Author’s Address
Robert J. Sparks
Estacado Systems
17210 Campbell Road
Suite 250
Dallas, TX 75252-4203
EMail: rjsparks@estacado.net
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