[VoiceOps] Load balancing

Simon Woodhead simon.woodhead at simwood.com
Sat Nov 7 03:36:44 EST 2009


> I have pretty much ruled out OpenSER/OpenSIPS/Kamilio because it isn't
> stateful in HA failover. Passing it through an Acme is ridiculously costly
> for the need i have, and most hardware based load balancers I am finding
> just aren't sip-aware, so I don't see them doing much better than OpenSER in
> a fail-over scenario, it would just be a different kind of ugliness.

I'd suggest you revisit that decision and reconsider what you actually need.

SIP is state*less* at the signalling load-balancer level. For
load-balancing you'd use the Dispatcher module which load-balances
based on the hash of various fields in the header. Those fields are
consistent throughout the dialog so a single proxy will naturally send
an entire dialogue to a single gateway without state. Equally, a
second proxy configured the same would do exactly the same. All you
need to deal with is the VRRP side for which there are numerous superb

RTP failover is a different story and different vendors do it
different ways. JT, I don't agree with you (for once!) that there is a
massive amount of data to sync; all a slave system needs to know is
the RTP ports on which it can expect to receive traffic and bridge
details. The commercial solutions we've looked at work on mac address
assumption (not IP address) and a slave can be a slave for many
masters as it is not actually handling full RTP for the master. It
isn't in FreeSwitch but I wouldn't expect it to be the challenge it is
perceived as being if someone has the motivation to tackle it. I agree
though, the VM based FT solutions are packet-by-packet mirrors so
there would be a lot to sync but who would run media on a VM anyway?!

All the best,
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