As my understanding, A should not do DNS query without any exception, such as 408 timeout.
So you should define the condition for DNS query in order to avoid the case you describe. Derrick -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Brett Tate Sent: 2008年5月20日 20:42 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). ________________________________ From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of ??? Sent: Tuesday, May 20, 2008 7:11 AM To: [email protected]; IETF Sipping List Subject: [Sip] SIP one DNS domain much IP Hi Guys: I have a question about DNS it is that one DNS domain has much IP Addrs , eg: as.test.net=>(192.168.2.1/192.168.2.2) and "as.test.net: is B2B server 1) A INVITE B , A resolves the DNS "as.test.net" 192.168.2.1,then A sends INVITE request to 192.168.2.1 2) A receives 200 response with contact "as.test.net" and no record route 3)A resolves the DNS "as.test.net" again, it gets 192.16.2.2 and sends ACK to 192.168.2.2 now the 192.16.2.1 can't recieve the ACK request , so the session can't be created Anyone can give me any advice, or some RFC/draft about it Thanks in advance Samman 2008-5-20 _______________________________________________ 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 _______________________________________________ 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
