Hi,
2006/5/9, Cseke Tamas cseke.tamas@eworldcom.hu:
That means, if one proxy dies during the session, the UA'll make a DNS SRV lookup, find the other proxy, and send the BYE to it instead of the proxy, which served the INVITE?
not quite - all sequential request (within the dialog) are routed based on the route set (the Record Route hdr added by the proxies on the path). The headers contains IP addresses, so basically no DNS lookup is done for sequential requests. An alternative will be to configure your proxy to put DNS name instead of IP in the RR hdr.
I 'd like the UAs to make only DNS lookup, when one proxy fails, if the proxy put domain name in The RR header, the UA must do a DNS lookup in every request, isn't it?
It should be (that's why it's always recommended to use FQDNs instead of IPs in SIP headers).....but I bet thousands of beers that many UAs won't do SRV lookup for every message.
First of all thanks the replies! Problem is the same, i wanna send a transaction to another proxy if one dies. But a RR header for the whole dialog is valid, i've got a suggestion to use FQDNs... I quess this way it should work, please someone take a look, if i missunderstood something...
In the scenario there is 4 outbound proxy, the message will be send in the so called SIP trapezoid (UAC->Outbound proxy -> Inbound proxy -> UAS) The INVITE transaction is sent successfully to one outbound proxy, but this proxy goes down, and the BYE transaction should go to another proxy in the same dialog.
DNS SRV for failover and load balancing
_sip._udp IN SRV 0 6 proxy1.outboundproxydomain.com _sip._udp IN SRV 0 4 proxy2.outboundproxydomain.com _sip._udp IN SRV 1 6 proxy3.outboundproxydomain.com _sip._udp IN SRV 1 4 proxy4.outboundproxydomain.com
Address records
outboundproxydomain.com A 217.xxx.xxx.195 outboundproxydomain.com A 217.xxx.xxx.196 outboundproxydomain.com A 217.xxx.xxx.197 outboundproxydomain.com A 217.xxx.xxx.198
proxy1.outboundproxydomain.com A 217.xxx.xxx.195 proxy2.outboundproxydomain.com A 217.xxx.xxx.196 proxy3.outboundproxydomain.com A 217.xxx.xxx.197 proxy4.outboundproxydomain.com A 217.xxx.xxx.198
INVITE ______
UAC INVITE sip:callee@domain.com SIP/2.0 Contact: sip:caller@domain.com
DNS lookup for outbound proxy (dig -t SRV _sip._udp.outboundproxydomain.com) Choose proxy1.outboundproxydomain.com dig -t A proxy1.outboundproxydomain.com -> 217.xxx.xxx.195 Send message to 217.xxx.xxx.195
Outbound proxy(217.xxx.xxx.195)
INVITE sip:callee@domain.com SIP/2.0 Record-Route: sip:outboundproxydomain.com;lr Contact: sip:caller@domain.com
Record-route ONLY its domain name. Lookup inbound proxy, send message to it.
Inbound proxy
INVITE sip:callee@domain.com SIP/2.0 Record-Route: <sip:proxy.domain.com Record-Route: sip:outboundproxydomain.com;lr Contact: sip:caller@domain.com
UAS
INVITE sip:callee@domain.com SIP/2.0 Record-Route: <sip:proxy.domain.com Record-Route: sip:outboundproxydomain.com;lr Contact: sip:caller@domain.com
....
BYE ___
UAC BYE sip:callee@domain.com SIP/2.0 Route: sip:outboundproxydomain.com;lr Route: sip:proxy.domain.com;lr Contact: sip:caller@domain.com
Most important part!!! lookup proxy (dig -t A outboundproxydomain.com) 217.xxx.xxx.195 failed send message 217.xxx.xxx.196 (proxy2.outboundproxydomain.com)
Outbound proxy (217.xxx.xxx.196):
BYE sip:callee@domain.com SIP/2.0 Route: sip:proxy.domain.com;lr Contact: sip:caller@domain.com
Inbound proxy:
BYE sip:callee@domain.com SIP/2.0 Contact: sip:caller@domain.com
UAS
BYE sip:callee@domain.com SIP/2.0 Contact: sip:caller@domain.com
Thanks in advance, Tamas