[asterisk-biz] SIP , SIP-I and SIP-T

[Alex Balashov]

Trixter aka Bret McDanel wrote:
> On Fri, 2008-05-23 at 06:36 -0400, Alex Balashov wrote:
>> Dome Charoenyost wrote:
>>
>>> Can someone explain about SIP,SIP-T and SIP-T ?
>>> and Asterisk support SIP-I,SIP-T or not ?
>> It is a way to map and/or encapsulate some values particular to PSTN 
>> signaling protocols (such as ISUP) back into SIP so that SIP can serve 
>> as a minimally viable transport between two nodes that speak those 
>> protocols, i.e.
>>
>>     ISUP ----> SIP/ISUP gateway ----> IP ----> SIP/ISUP gateway ---> ISUP
>>
>> Asterisk does not really support these because it is a back-to-back user 
>> agent, so it does not need to follow RFC rules regarding conservation of 
>> special headers or data elements in a transaction the way that a proxy 
>> does.  Asterisk can and will regenerate new call legs scoped to the 
>> interface technologies it actually supports and cares about.
>>
> 
> Supporting them has nothing to do with being a B2BUA, PBX or softswitch.
> They are variants of SIP, and as such they would require a proper
> protocol stack to support.  More at the end on this.

I think I misspoke.  What I meant was that because Asterisk does not 
have a protocol stack for these, it will not "support" them in the sense 
that it will neither (1) take advantage of their features or provide any 
features specific to those implementations, or (2) pass / tunnel those 
protocols passively.  In the latter case, being a B2BUA does have a lot 
to do with that.

-- 
Alex Balashov
Evariste Systems
Web    : http://www.evaristesys.com/
Tel    : (+1) (678) 954-0670
Direct : (+1) (678) 954-0671
Mobile : (+1) (706) 338-8599