Question about the To-tag in a 408 response initiated on a stateful proxy.A
stateful proxy forwards INVITE to terminating client, who respondes with 180
(with To-tag). The UA is then is unplugged (network isolated) such that he can
not send a final response back to the proxy. Later, (~3min) proxy Timer-C
expires and now (acting like UAS) sends the 408 response, but uses a *new*
To-tag.Should this to-tag be the same as from the 180 ringing, or can it be a
new one?I read through the passage below, and it looks to like it can be a new
to-tag since1. hop-by-hop2. 408 is not being forwarded from the terminating
side.Am I wrong here?http://tools.ietf.org/html/rfc3261#section-16.7<<SNIP form
3261 16.7>> 3-6xx responses are delivered hop-by-hop. When issuing a
3-6xx response, the element is effectively acting as a UAS, issuing
its own response, usually based on the responses received from
downstream elements. An element SHOULD preserve the To tag when simply
forwarding a 3-6xx response to a request that did not contain a To tag.
A proxy MUST NOT modify the To tag in any forwarded response to
a request that contains a To tag.Rosenberg, et. al. Standards Track
[Page 111] RFC 3261 SIP: Session Initiation Protocol
June 2002 While it makes no difference to the upstream
elements if the proxy replaced the To tag in a forwarded 3-6xx
response, preserving the original tag may assist with debugging.
When the proxy is aggregating information from several responses,
choosing a To tag from among them is arbitrary, and generating a new To
tag may make debugging easier.<<END>> thanks,Will
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