[Serusers] Loadbalancing / high availability

[E. Versaevel]

To bad not every UA supports _SRV lookups, so round robin is not exactly
what I'm looking for.
NAT Traversal is a bit of a problem with multiple IP addresses, however, if
you use direct routing (and have all the boxes in the cluster reply from the
same IP) there shouldn't be a problem.

Spreading the contacts can be done with t_replicate (and flushing the
database often enough) so that if a ser hosts goes down the contacts are
already in the database, which is loaded at a restart.

This could actually work I think, I may have a test environment available
today so I might test this :)

Kind regards,

E. Versaevel

-----Oorspronkelijk bericht-----
Van: Klaus Darilion [mailto:klaus.mailinglists at pernau.at] 
Verzonden: woensdag 1 december 2004 21:32
Aan: E. Versaevel
CC: serusers at lists.iptel.org
Onderwerp: Re: [Serusers] Loadbalancing / high availability

Hi Erik!

Another easy way for loadblancing ist the usage of SRV records for the 
SIP domain.

And there are a lot of other problems:
- caching of the contacts of the registered clients (use t_replicate)
- NAT traversal: doesn't work that easy with multiple proxies with 
multiple IP addresses.
- ...

search in the mailinglist archive - there are already several threads on 
this topic.

regards,
klaus

E. Versaevel wrote:

> 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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