[...Moved to SIP-IMPLEMENTORS...]
vishal wrote:
> Hi Bobby,
>
> you are correct if message size is less than MTU size then
> response must be over UDP .....
> some other problems are :
> when proxy forwards INVITE requests .It adds "Via:" field into it along
> with appropriate parametres ....if message is forwarded by many proxies
> then this message may become greater than MTU size in particular network
> ....how this case should be handled ?
> should next proxy establish TCP connection and then forward it OR
> reject this message?
Remember that proxies operate on a hop-by-hop basis. If a proxy gets
a request which is near to the path MTU (if known), it can use the
TCP transport (assuming that the next downstream server supports it)
over the particular hop between itself and the next downstream server.
It could be that the next downstream server does not support TCP (which
may be the case if it is a RFC2543-compliant UAS), then UDP will be
used. But I think that this case may be mitigated by the fact that
this maybe the last hop between an "inbound" proxy and the UAS, so it
will probably be within the same domain with a higher path MTU. Most
deployed proxies that I know of support both TCP and UDP; so for
inter-proxy routing, this is not an issue. In any case, as -09bis
percolates, support for TCP in UAS becomes mandatory.
> If proxy forwards this message using TCP and UAS receives INVITE over
> TCP then UAS response will be sent over TCP and UAC should be prepared
> to receive response over TCP or UDP for its previous INVITE over UDP
> request.
No, responses also follow the hop-by-hop basis. The UAS will use TCP
for its first hop only, not the remaining hops. The UAC will get the
response from its first downstream server; and if the UAC used UDP for
the original request to its first downstream server, the response will
also be over UDP.
Hope that helps.
- vijay
--
Vijay K. Gurbani vkg@{lucent.com,research.bell-labs.com,acm.org}
Wireless Networks Group/Internet Software and Services
Lucent Technologies/Bell Labs Innovations, 2000 Lucent Lane, Rm 6G-440
Naperville, Illinois 60566 Voice: +1 630 224 0216
_______________________________________________
Sip-implementors mailing list
[EMAIL PROTECTED]
http://lists.cs.columbia.edu/mailman/listinfo/sip-implementors
