On Mon, 2005-12-05 at 17:41 +0530, [EMAIL PROTECTED] wrote: > If proxy sends the response Too Many Hops (483) for the Loop problem. Then > UAC will again try the same request with the different value in the > Max-Forwards header.
It would be foolish to set a value in Max-Forwards that is higher than the standard value (70, see section 8.1.1.6 of RFC 3261). Loop detection is a difficult problem. If your goal is to avoid rejecting a request as a loop that might be a legitimate spiral, it is very hard for the proxy to accomplish this, even statefully, because the proxy isn't aware of which fields might be significant to the UA, or to other proxies in the path. On the other hand, if all the proxies properly implement Max-Forwards, all loops will eventually be detected as "too many hops". Because of these problems, some proxies do not do loop detection. They seem to work OK in practice. As Marc noted, it would also be desirable to solve the "branching loop" problem. Current loop-detection algorithms can detect some of those cases, but one can construct realistic scenarios where they do not. A full solution needs to be along the lines of http://www.ietf.org/internet-drafts/draft-lawrence-maxforward- problems-00.txt Dale _______________________________________________ Sip-implementors mailing list [email protected] http://lists.cs.columbia.edu/mailman/listinfo/sip-implementors
