[Asterisk-Dev] OT: R&D Loadbalancer SIP Questions

[Darren Sessions]

F5 Networks Big IP product line.

One set of boxes can load balance all sorts of applications - including SIP.



On 3/24/05 5:52 PM, "asterisk-dev-request at lists.digium.com"
<asterisk-dev-request at lists.digium.com> wrote:

> Message: 6
> Date: Thu, 24 Mar 2005 15:32:27 -0600
> From: "Matthew Boehm" <mboehm at cytelcom.com>
> Subject: [Asterisk-Dev] OT: R&D Loadbalancer SIP Questions
> To: <asterisk-dev at lists.digium.com>
> Message-ID: <01fd01c530b9$0bdfda70$3400000a at cytelcom.com>
> Content-Type: text/plain; charset="iso-8859-1"
> 
> I'm posting this here as the -dev people are most likely more intimate with
> the SIP packet structure than -users are.
> 
> I've been trying to find a pure SIP load balancer. We will soon be doing
> some major traffic and I feel that easiest growth is stacking * boxes behind
> a load balancer. All calls will be SIP<->SIP or SIP -> PSTN; no PSTN->SIP
> 
> Yes, I could use SER, but that is just another computer that could fail.
> 
> I sent an email to Cisco. No response.
> I emailed Tasman Networks and they said to contact Kemp Tech.
> 
> Just got off the phone with a technician at Kemp and he had the following
> questions for handling SIP load:
> 
>     1. Which SIP header would be best to become the "session id"? He gave
> examples of Via header, callid header and From header. The header needs to
> be persistant across all packets per call and be unique between calls. (not
> purely unique, meaning that the LB doesn't store id's past the termination
> of the call.)
> 
>     2. Is the "session id" chosen in #1 also present in the audio payload
> packets?
> 
>     3. I was under the impression that SIP over TCP was not yet an RFC
> standard but the tech seemed to think so. So his question was "at any time
> during a call, are there both tcp and udp packets refering to that same
> call? and with the same id as #1?"
> 
>     4. Finally, he wanted to know what could he do to "query" each server to
> determine if it should be in the pool of servers. For example, when doing
> HTTP requests, the LB examines the packet and if it finds any thing in the
> error 500 range, that server is marked as "down".  He said that he could
> send an INVITE to each server and as long as he recieved code XXX that that
> server would remain in the pool. If no response recieved after XXms, or the
> incorrect response code recieved, then the server is marked down and email
> fired off.
> 
> Thoughts, questions, concerns are welcome.
> 
> Thanks,
> Matthew
> 
> -- 
> Matthew Boehm
>   There is no air in space.
>   If there was, we couldn't call it space.
>   It would be called atmosphere.