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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