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On 11/29/2010 06:03 AM, Eric Hiller wrote:
<blockquote cite="mid:BLU112-W153A820E2B72810401DA9EDB240@phx.gbl"
type="cite">
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all for the second question of the night as I go through working out
bugs in my setup. I want to use SRV records to loadbalance across
hosts. This works great, when all the hosts listed in the SRV are up.
However, I want kamailio to use the next host if the current hosts
fails. I tried just setting up a new branch, but kamailio keeps using
the same SRV entry over and over on that transaction, only a new
transaction seems to give kamailio a chance to use a different SRV
entry. Any ideas as to how I can force kamailio to try the next SRV
entry if the first one fails?
<div><br>
</div>
<div>For example I t_relay to 2.domain.com which has a
_sip._udp.2.domain.com entry for hostA and hostB. If hostB is down, but
kamialio decides to send to hostB it just keeps doing so even though
hostA is perfectly up it doesn't try for it. Is there a way to remove
hostB from the kamailio try list? Or as an alternative to do a manual
SRV lookup on 2.domain.com and then put then in a variable and go
through them one by one manually?</div>
<div><br>
</div>
<div>Ideas? Thanks</div>
<div>-Eric</div>
</blockquote>
Hello,<br>
<br>
Kamailio does not use ICMP replies to check if a host is reachable on a
UDP sendto(). This means that ICMP port unreachable errors are not
handled by K and so the same host is retried on TM retransmits. Host
selection of both A records and SRV records is done based on weights
returned from the DNS query(so it is balanced)<br>
<br>
For a INVITE you can use fr_timer to very low values (5 seconds) and
fr_inv_timer to larger value. If no 100 is received than the fr_timer
kicks in and depending on the disable_dns_failover core parameter
another host is tried. The order of retry is this: Regardless of
disable_dns_failover param, other A records are tried (if no 0x4 flag
is given to t_relay (at least in K1.5)), then , is dns_failover is
active, other SRV records, then NAPTR.<br>
<br>
Check the TM documentation for more info.<br>
<br>
Marius<br>
<br>
P.S. This is on K 1.5 . I hope 3.0/3.1 still has this . I think dns
caching has changed so you need to recheck the parameters I gave. <br>
<br>
<br>
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