On 17 Nov 2003, at 13:07, Vijay K. Gurbani wrote:
This behavior is what you will get and is correct under the current implementation of the protocol. The default transport for SIP is UDP (see Table 1, rfc3261) and most implementations support UDP more readily than they do TCP. Thus, absence any 'transport=tcp' guidelines, they will revert to UDP.
FranzGober writes:
Is this behaviour correct if each message indicates TCP in the VIA field ?
Vijay continues:
Note that the Via field is used to route >>responses<<, not requests. The Contact field is used to route subsequent requests within the dialog. Thus, the initial INVITE/200 OK can happen over TCP, but subsequent requests like ACK or BYE will degenerate to UDP if the 'transport=tcp' is omitted.
Not only is this the 'specified' behaviour, but I will point out that I have observed this (pedantically) correct behaviour in many UAs that I have tested with at the SIPit events. The general consensus is that the 'transport=tcp' parameter on the contact URI is something that gets overlooked frequently. The emergent behaviour described above is what results. It can be somewhat unexpected.
Alan Hawrylyshen a l a n a t j a s o m i d o t c o m http://www.jasomi.com/
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