[Asterisk-Dev] Petition for IAX firmware

[Steve Kann]

Greg Hill wrote:

> On Wed, 6 Apr 2005, Paul wrote:
>
>> Steve Kann wrote:
>>
>>>
>>> I have two points to make:
>>>
>>> 1) If I were a vendor, and there was documentation on the IAX2 
>>> protocol (not even an RFC, but at least some kind of semi-official 
>>> documentation), I'd be a lot more likely to implement it.
>>>
>>> 2) The idea of an IAX2 trunk-aggregator is interesting. This is 
>>> probably something that doesn't need a whole x86 linux box -- taking 
>>> multiple IAX2 streams and putting them into trunks is trivial in 
>>> terms of computational requirements.. A small microcontroller or an 
>>> ARM chip is more than enough for this, and would be a neat idea of 
>>> virtual PBX deployments..
>>>
>>> -SteveK
>>
>>
> (snip)
>
>> But I still don't know the answer to my question about SIP vs. IAX2. 
>> Suppose the remote site has a mix of SIP and IAX2 devices. Does the 
>> presence of SIP devices increase the computational requirements much? 
>> My thinking is that any SIP ata's or phones at the remote site are 
>> going to be extensions of the master * pbx. Hopefully that makes it 
>> easier on the trunk-aggregator cpu. Also I expect that in most 
>> situations where this was deployed a codec other than g.711 would be 
>> used since there is a motivation to conserve bandwidth. So we have 
>> SIP traffic from a provider to the master server, IAX2 trunking to 
>> the remote slave server and back to SIP over the LAN to somebody's 
>> deskset. Will that conversion back to SIP to reach the deskset 
>> degrade the call quality?
>
>
> SIP and IAX are control protocols. They don't deal with audio coding. 
> Converting a call between SIP and IAX protocols should require minimal 
> (no?) re-writing of the audio packets if the same codec is used on 
> each side. So it seems (to me) that a translation between SIP and IAX 
> wouldn't be a computationally expensive task.

I'm quite aware of what SIP and IAX are :)

If you're trying to say that SIP and IAX both use RTP for the media 
stream, that's wrong. For SIP (and h.323 and others), the media is 
carried in a separate RTP stream. For IAX2, the media is carried in IAX2 
packets. But, taking the media from one format to another, while 
computationally simple, still requires unpacking and repacking the 
individual packets, translating metadata (timestamps, etc).



-SteveK