[Asterisk-Dev] Henning G. Schulzrinne quote on IAX2 from vonmagazine

[Derek Smithies]

Hi,

On Sun, 14 Aug 2005, Tilghman Lesher wrote:
> Actually, all you'd need to do, then, is to raise the priority with
> which the iax2 monitoring thread runs.  If it's not getting enough
> CPU time, raise the priority and it will get what it needs.
 Not really a good idea to raise the priority of one thread as opposed to 
another. Weird things start to happen..

The iax2 impliementation I wrote, which is now part of the OPAL cvs at 
www.sourceforge.net/projects/openh323
and announced at cluecon,
http://www.geekchix.org/rss/Asterisk_VoIP_News/2005/08/
uses lots of threads.

There is one thread which just reads packets in, and then passes them on.
and then reads the next, and then passes it on

There is another thread for transmission, which just transmits each packet 
as one becomes available for transmission. 

The reading/transmitting threads do no processing - they just pass packets 
on.

This architecture is scalable, and will work on machines with many cpus.

==========================================================

Advertising aside, what is missing from this discussion is NAT/firewall 
traversal.

There are many places where users have 2 or more firewalls between them 
and the public internet.
The NAT traversal techniques devised for SIP and H.323 are going to 
struggle/fail in this environment.

Also missing is an acknowledgement of the brokenness of many 
NAT/firewalls. Some claim to support upnp. Some don't support upnp. Some 
claim to support upnp, but do not do it correctly. Some have h.323/sip 
proxies in them. The proxies work for some sip/h.323 clients, but not 
all. In this environment, sip/h.323 will struggle.

However, IAX2 will work fine here.

Now, NAT traversal is important for the individual user, but totally 
irrelevant to the telcos. Telcos do seemingly weird things, where the 
media and control streams are sent on different paths to the final 
endpoint.
To a telco, iax2 is just weird...
For an individual user, iax2 is just fine..

Derek.

-- 
Derek Smithies Ph.D.                         
IndraNet Technologies Ltd.                
Email: derek at indranet.co.nz         
ph +64 3 365 6485                          
Web: http://www.indranet-technologies.com/