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
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