Dell VoIP Products Analysis
Of course, you can get OCS to work with Fonality, an Asterisk-based PBX as well. As I wrote previously, unfortunately, Asterisk-based PBXs only supports SIP over UDP and OCS 2007 & Exchange 2007 Unified Messaging (UM) requires SIP over TCP. There is one unsupported patch to enable SIP over TCP on Asterisk, however. Another workaround is to use sipX, an open-source SIP proxy which handles both SIP/TCP and SIP/UDP and acts as a gateway between Asterisk and Exchange UM. You can use OpenSER as a SIP UDP to SIP TCP gateway as well. Can't really blame Microsoft for this lack of Asterisk integration since usually SIP uses TCP and only the RTP audio stream uses UDP. In fact, according to the voip-info wiki, "Making TCP mandatory for the UA is a substantial change from RFC 2543. It has arisen out of the need to handle larger messages, which MUST use TCP."
So like I've said before, the Asterisk community needs to get on the ball and add SIP over TCP functionality.
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Comments to Dell VoIP Products Analysis
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Jonas B. :
January 25, 2008 6:57 AMUsing TCP for SIP is not common at all, I've never ever seen it in the field. It runs over UDP since it that was how it was designed, for some very good reasons (you don't want three way handshakes for real time signalling such as answering a call if you can avoid it), but you have to switch if your messages get too large (which they don't when running "normal" telephony but may do when there is other stuff involved).
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JP :
January 24, 2008 1:48 AM
"Can't really blame Microsoft for this lack of Asterisk integration since usually SIP uses TCP and only the RTP audio stream uses UDP. "
Really? If "usually" means about .01% of SIP calls, then maybe.
The fact it is not normal is pretty clear by your next sentences:
'In fact, according to the voip-info wiki, "Making TCP mandatory for the UA is a substantial change from RFC 2543. It has arisen out of the need to handle larger messages, which MUST use TCP."'
Not saying it is a bad idea to go to TCP, but your contention that TCP is something common, let alone normal, is a huge stretch.