RFC 3261 clearly states that a failure of a transaction within a dialogue does not necessitate tear-down of the session. For example, if a re-INVITE fails, the session continues with the previously negotiated information. Only in the case of a 481 or a 408 should the dialogue be torn down.
Out of order requests (aside from not having a distinct error code for that) is a simple case to deal with. The _only_ reason I ever switch to TCP is if the patch between endpoints involves something that will fragment a large UDP packet and not re-assemble it. There are too many headaches with the TCP usage in SIP to use it for anything else. David On Sun, Sep 27, 2009 at 11:35:44PM +0530, Pranab Bohra wrote: > An example - An UAS will respond with 500 response when it receives > out of order requests. > This might result in session tear down. > TCP handles OOO packets in a better way and won't let such situation occur. > I think one would use TCP (i.e reliable L4 ) when SIP reliabilility > alone is not enough. > > Thanks, > Pranab > > > On Sat, Sep 26, 2009 at 4:23 PM, I?aki Baz Castillo <i...@aliax.net> wrote: > > El S?bado, 26 de Septiembre de 2009, Pranab Bohra escribi?: > >> As > >> Abhishek mentioned, reliability is the concern here. > > > > I don't understand it. You are speaking about *network* level reliability > > (level 4) but since we are talking about SIP what we need is *application* > > level reliability (level 5). And the fact is that SIP implements by itself > > reliability in the protocol (ACK, CSeq, retransmissions...). > > > > Of course that SIP over TCP simplifies the reliability mechanism (basically > > some transaction timers used in SIP UDP dissapear for SIP TCP) but from the > > point of view of the application protocol (SIP) reliability exist for both > > transport layers (reliable: TCP, and non reliable: UDP). > > > > Regards. > > > > -- > > I?aki Baz Castillo <i...@aliax.net> > > > > _______________________________________________ > > Sip-implementors mailing list > > Sip-implementors@lists.cs.columbia.edu > > https://lists.cs.columbia.edu/cucslists/listinfo/sip-implementors > > > > _______________________________________________ > Sip-implementors mailing list > Sip-implementors@lists.cs.columbia.edu > https://lists.cs.columbia.edu/cucslists/listinfo/sip-implementors > > !DSPAM:4abfa992127521958711902! > _______________________________________________ Sip-implementors mailing list Sip-implementors@lists.cs.columbia.edu https://lists.cs.columbia.edu/cucslists/listinfo/sip-implementors
