Hi,
2006/5/9, Cseke Tamas
<cseke.tamas(a)eworldcom.hu>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