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04-28-2007, 11:18 AM | #1 | ||
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Join Date: Mar 2006
Posts: 96
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Record-Route: header - is it really necessary?
The optional "Record-Route" header, as explained in RFC 3261, is inserted by SIP proxies that wish to remain in the signalling path for the duration of the dialogue:
Quote:
I do not understand why (apart from, perhaps collecting statistics on call minutes) it is useful for sipbroker.com to remain in the signalling path after the call is established. I am not aware of any "mid-call features" that the sipbroker.com proxy is providing. I had originally thought that the "Record-Route:" header was somewhat essential for "NAT traversal", however I now understand that that is taken care of with the "Via: " headers, and use of the "rport" parameter, etc. The problem with sipbroker.com adding the "Record-Route:" header is that it then requires sipbroker.com to add the loose-routing parameter: "lr", which causes incompatibilities: Quote:
Although RFC 3261 explains the "lr" parameter as just ";lr", in order to "make some broken UAs happy", sipbroker.com adds "=on" to the "lr" parameter: Code:
INVITE sip:050xxxxxxxx@xxx.xxx.xxx.xxx:5060 SIP/2.0 Record-Route: <sip:64.34.162.221;lr=on;ftag=as570b93cc> Via: SIP/2.0/UDP 64.34.162.221;branch=z9hG4bK3ade.c5e555e3.0 Via: SIP/2.0/UDP 64.34.173.199:5061;branch=z9hG4bK00a2f0d9;rport=5061 It would seem to me that, if sipbroker.com simply did away with inserting the "Record-Route:" header, thereby avoiding having to use the "lr" parameter, it would please everybody, improve compatibility (interoperability), and improve conformance to RFC 3261. |
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