[OpenSER-Devel] Possible bug in the tm module in the presence of packet loss/branches

[Dan Pascu]

On Thursday 06 March 2008, Maxim Sobolev wrote:
> The issue at hand has lead me to discovering the problem, which is hard
> to observe, but the problem itself IMHO is important one and by no
> means non-existing in the real world. As I said in the other message,
> I've seen this issue many times before in normal conditions, but
> attributed it to some kind of CPE failure. This could also happen not
> only due to network problems but due to UDP packets loss when server is
> loaded. Run "netstat -su" on the any more or less loaded Linux server
> running OpenSER and see how many UDP packets are getting dropped every
> second ("packet receive errors" item).

Udp:
    219469376 packets received
    154 packets to unknown port received.
    16936 packet receive errors
    261877247 packets sent

This is from a box which is loaded close to the limit of the number of 
users a single box can handle. Yet the packet loss is only 0.0077%, which 
is insignificant and can be dealt with by the retransmission mechanism.

My issue with what you're proposing is that it tries to modify the SIP 
callflow to something no specified in the RFC, to solve a non-SIP 
problem. I also do not like the idea that the proxy would keep 
retransmitting on a branch after the originator has canceled the call.

-- 
Dan