Jakob Schlyter wrote:
>
> hi,
>
> it seems to me that the current sip draft is unclear whether tcp is
> mandatory for redirect servers. section 1.5.2 (protocol properties,
> lower-layer-protocol neutral) says ...
>
> "User agents SHOULD implement both UDP and TCP transport. Proxy,
> registrar, and redirect servers MUST implement both UDP and TCP
> transport."
>
> ... but section A.1 (minimal implementaion, transport protocol support)
> says ...
>
> "User agents and stateless proxies MUST support UDP and MAY support TCP or
> other transport protocols, stateful proxies MUST support both UDP and
> TCP."
Clearly, TCP support is mandatory in a proxy (the reason for this is so that
2 UAs, one using only TCP and the other only UDP can communicate at the
signaling layer using the proxy).
Now, since a redirect server, much like a proxy, is a logical function in
SIP, and since a proxy implements both TCP and UDP, it becomes easy enough
for the redirect server to use the same software routines as the proxy and
support TCP as well.
While section A.1 does not expilictly mention what other kinds of servers
(besides proxies, which it does mention explicitly) should support TCP, I
would presume that support for TCP in Redirect and Registrars is assumed.
More so for Registrars since (for whatever reason), a user may want to
upload a real long (> what can fit in a UDP datagram) CPL script during
registration.
Implementation-wise, the software can be architected in such a way as to
have a TCP request handler thread which listens for a connection, extracts
a SIP request (or response) and puts it in some processing queue for the
Proxy/Registrar/Redirect server to consume.
Best regards,
- vijay
--
Vijay K. Gurbani vkg@{lucent.com,research.bell-labs.com,acm.org}
Internet Software and eServices Group
Lucent Technologies/Bell Labs Innovations 263 Shuman Blvd., Rm 1A-413
Naperville, Illinois 60566 Voice: +1 630 224 0216 Fax: +1 630 713 0184
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