Re: SIP Proxy Experiences

[Andrew Rutherford <>]

At 6:02 AM -0400 12/8/03, Tyler Miller Johnson wrote:

> I am curious what SIP proxies folks are using and their experiences. 
> I am looking for a highly standards compliant proxy, especially one 
> that is geared toward generic SIP support as opposed to being 
> targetted as a telephony server. It should have some sort of API so 
> I can develop custom interfaces.

ser (http://www.iptel.org/ser/) is very good, for example the 
INOC-DBA project (http://www.pch.net/inoc-dba/) used ser to replace 
Cisco's SIP Proxy with good effect,and also meets your stated 
requirements.

Asterisk is probably a bit too telephony-focused given your 
requirements, and also it has an internal telephony format that gets 
mapped to SIP which also probably doesn't fit your requirements.


We use some software we wrote in-house and have been selling 
commercially [1] called Slipper, written in Perl, runs on just about 
anything, and has a plug-in module architecture that allows you to 
either manage each SIP message individually, or just push values into 
the internal data format in response to the first request and let 
Slipper handle the rest of the transaction.

It's based on a ruleset model (think sendmail, but the rulesets don't 
need to be anywhere near as complex), with modules invoked in the 
order you want as defined by the rulesets. PDF documentation is 
available from 
http://www.iagu.net/software/slipper/slipper-current.pdf


As to actual experience - yes, we use it for telephony (or office has 
run on it for around a year and a half), and we have multi-site 
installs of 40+ devices at each site. However, it's not telephony 
focused, we have ISP customers using it as an instant messaging 
service and nothing else. No-one was more surprised than us when we 
found we didn't have to change anything to handle Microsoft's XP 
Instant Messenger client. [2] :-)

We even have one group experimenting with a mail server that saves 
messages received via SMTP into a web server data store and the use 
SIP NOTIFY's to alert the client the message has arrived. Yes, 
they're dealing with low-end set-top boxes that already have a web 
client and they'd rather not have to fit in an IMAP client in as 
well, or use anything that involves frequent polling (scaling 
issues), so this fits the bill. They just tuned some variables in 
Slipper regarding exponential backoff and retry to get unacknowledged 
notifications spread over a 36 hour period.


[1] ObApology: Apologies for saying commercial stuff on this list.

Cost is fairly low compared to other commercial products - AUD 2000 
(currently around USD 1300) gets you a one-year license for unlimited 
copies of the server with maintenance & upgrades. Subsequent years 
are 25% off. 30-day free trials are easy to arrange, but you have to 
sign something saying you're not going to give the code away. :-)

[2] Well, OK, we did find we had to use RFC2543 strict routing 
instead of RFC3261 loose routing when setting up phone calls, or XP 
Instant Messenger would claim that the method "INVITE" was 
unsupported. :-)

--
Andrew Rutherford      
sip:
      244 Pirie Street
Iagu Networks          tel:+61-8-8425-2255       Adelaide SA 5000
http://www.iagu.net/   
mailto:
   Australia

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