Hi,
I have a very basic doubt w.r.t. the Via branch
computation by a stateless proxy (SLP). Consider the
following setup:
stateful ----> stateless ----> stateful
entity(A) proxy(SLP) entity(B)
In this setup, let the stateful entity (A) be a pre-bis-05
compliant device (it could be a UA or a proxy). Hence it
does not insert the magic cookie in the Via branch that
it inserts.
Now, for every request that the SLP proxies, it would
insert a Via header with a branch computed as described
in Section 16.11 :
"......the first component of the branch ID is
computed as a hash of the topmost Via, the tag in the
To header field, the tag in the From header field, the
Call-ID header field, the CSeq number (but not method),
and the Request-URI from the received request."
How will the above work in the case of an INVITE-4xx-ACK
scenario ? The initial INVITE will not contain a To-tag
whereas the ACK to the non-2xx will contain a To-tag.
If the SLP uses the above stated algorithm, it will end
up generating a different Via branch for the INVITE and
the ACK thus botching up the transaction matching logic
at the next stateful entity (B).
I know i'm missing something trivial, but what ???!!!
Subhash Nayak
Hughes Software Systems
http://www.hssworld.com
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