Subject: [SIP] Discussion

From: james jack <[email-masked]>
Date: Wed, 1 Nov 2000 21:40:38 -0800 (PST)

Dear All:
    I have one question to discuss. In order to 
detect loop, RFC2543bis02 page 81 says"A request has
been looped if the server finds its own address in the
Via header field and the hash computation over the
fields enumerated in Section 6.46.6 yields the same
value as the hash part of the ¡°branch¡± parameter in
the Via entry containing the proxy server¡¯s
address.",
Page 59"In order to be able to both detect
loops and associate responses with the corresponding
request, the parameter SHOULD consist of two parts
separable by the implementation. One part, used for
loop detection (Section 12.3.1), MAY be computed
as a cryptographic hash of the To, From, Call-ID
header fields, the Request-URI of the request received
(before translation) and the sequence number from the
CSeq header field. The algorithm used to compute the
hash is implementation-dependent, but MD5 [38],
expressed in hexadecimal, is a reasonable choice.".
According to my knowledge, it is necessary to detect
the Via to find whether loop or not, why use these
parameters to detect loop, Is the hash is easy to
implement? Could anyone give me advice on this?
   Thanks a lot!
   Best regards!
                        Yours: James

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