Hi,
RFC 3261 says that
Loop: A request that arrives at a proxy, is forwarded, and later
arrives back at the same proxy.When it arrives the second
time, its Request-URI is identical to the first time,
and other header fields that affect proxy operation are
unchanged, so that the proxy would make the same
processing decision on the request it made the first time.
Spiral: A spiral is a SIP request that is routed to a proxy,
forwarded onwards,and arrives once again at that proxy,but
this time differs in a way that will result in a
different processing decision than the original request.
Typically, this means that the request's Request-URI
differs from its previous arrival.
In the point 8 of Request Forwarding section 16.6 says that second part of
the branch parameter calculation should include the To tag, From tag, Call-ID
header field, the Request-URI of the request received (before translation), the
topmost Via header, and the sequence number from the CSeq header field, in
addition to any Proxy-Require and Proxy-Authorization header fields that may be
present.
But if the request is either looped back / spiralled back then the To tag,
From tag, Call-ID header field,the sequence number from the CSeq header field,
Proxy-Require and Proxy-Authorization header fields will be identical. So why
should we include all these header fields in the calculation of the branch
parameter. We could only take the Request-URI and the topmost Via header since
these parameters can be changed and it inflenzes the routing logic.
can any one clarify me in this regards.
Thnx,
Mannan.
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