[Serusers] Loadbalancing / high availability

[Matt Schulte]

I'm curious what brand load balancer you would use, would it be IP
based. We tried out a Cisco SLB and had no luck, mainly because it would
NAT to the servers (more trouble than it's worth?). We were thinking of
using a heartbeat type failover, similar to what you would do for MySQL:

http://linux-ha.org/download/

Has anyone tried this method? We're more concerned about the high
availability than anything.

-----Original Message-----
From: E. Versaevel [mailto:erik at infopact.nl] 
Sent: Wednesday, December 01, 2004 7:24 AM
To: serusers at lists.iptel.org
Subject: [Serusers] Loadbalancing / high availability


Hello,

I was wondering if it is necessary for a SIP packet from a specific call
to always go through the same server?

For instance, if you have a load balancer distributing requests over a
few servers, it is possible that an INVITE ends up on 1 server while the
following INVITE with the credentials ends up on another, would this be
a problem (ie, break the authorization) or should you use a SIP aware
loadbalancer for this (who looks at the callid for example)? Assuming
the ser servers are setup to use the same userdatabase (and t_replicate
to eachother) the picture would be something like this:

			 |
		  --------------
	        |loadbalancer|
		  --------------
	             |
	             |
	    --------------------
	    |	       |         |
	-------   -------   -------
	|     |   |     |   |     |
	| ser1|   | ser2|   | ser3|
	|     |   |     |   |     |   
	-------   -------   -------

If you setup the servers with the same IP as the load balancer and stop
them from replying to ARP requests for that IP, replying back thru a NAT
should not be a problem.

Just thinking out loud, I could use SER for the load balancing and
t_relay the packets, however that would require some tampering with the
VIA records (and I should use a reply to via in that case to the
original IP the SIP request came from, eg not the load balancer) this
way outgoing SIP traffic would not have to go thru the ser loadbalancer
again to get out, hmm, it might even be possible to use a route-record
header to get the packets back at the correct server...


Kind regards,

E. Versaevel

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