>>This is what I don't understand - under what condition is it desired that >>the 2xx ACK goes to a different destination than the original INVITE?
In an attempt to answer my own question... I guess it's OK provided that the all servers of the DNS SRV group resolve the ACK's URI to the same SIP endpoint. I think I am confusing SIP servers and SIP UAs - the UA requires the ACK to come back to it but the server does not. -----Original Message----- From: Attila Sipos Sent: 20 May 2008 15:16 To: 'Brett Tate'; 孙永光; [email protected] Subject: RE: [Sip] SIP one DNS domain much IP Hi Brett, Thanks for your response - to me it highlights something that I don't understand in RFC 3263: Because the ACK request for 2xx responses to INVITE constitutes a different transaction, there is no requirement that it be delivered to the same server that received the original request (indeed, if that server did not record-route, it will not get the ACK). So if it doesn't get the ACK, the 2xx response will be retransmitted over and over - won't it? This is what I don't understand - under what condition is it desired that the 2xx ACK goes to a different destination than the original INVITE? Cheers, Attila -----Original Message----- From: Brett Tate [mailto:[EMAIL PROTECTED] Sent: 20 May 2008 14:34 To: Attila Sipos; 孙永光; [email protected] Subject: RE: [Sip] SIP one DNS domain much IP > > If SRV records not supported, the Contact should reflect a single AS > > Did you mean that if SRV records ARE supported? Hi Attila, Nope. If SRV supported and being used, the SRV records allow the desired order to be clearly indicated. > Isn't the problem that the Contact in the 2xx didn't contain something > that maps to a single device? Depends upon intent. I assume that the person configuring the Contact had reason to supply a Contact able to resolve to more than 1 location. I assume the reason is that the alternative location can occasionally (obviously not always because question posted) be able to handle the in-dialog requests. If the alternative location can never handle the in-dialog requests, I agree that it would be an inappropriate configuration. Cheers, Brett > -----Original Message----- > From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of > Brett Tate > Sent: 20 May 2008 13:42 > To: 孙永光; [email protected] > Subject: Re: [Sip] SIP one DNS domain much IP > > Because of potential load-balancing (as you are observing), solely > using A records within primary/secondary configurations should be > avoided unless additional agreements or configuration has been made to > avoid the situation you are describing concerning in dialog requests. > The additional agreements override typical rfc3263 behavior by > applying local policy (potentially non compliant) to remain stateful > within dialog. The potential additional configuration (to avoid the > mentioned override) is to have DNS control to avoid automatic > load-balancing/iterating concerning A records so that the A record > query/handling can always result in the same ordered list. > > RFC 3263 discusses using DNS SRV records to more clearly indicate > prioritization and load-balancing. If SRV records not supported, the > Contact should reflect a single AS unless the alternative locations > can accommodate the situation (or additional agreements or > configuration has been made to avoid trying the alternative locations > first). > . _______________________________________________ Sip mailing list https://www.ietf.org/mailman/listinfo/sip This list is for NEW development of the core SIP Protocol Use [EMAIL PROTECTED] for questions on current sip Use [EMAIL PROTECTED] for new developments on the application of sip
