Michael
--Original Message Text---
From: Lonnie Abelbeck
Date: Fri, 15 Sep 2006 14:51:12 -0500
Gary,
My experience has shown SIP better voice quality than IAX, as well.
I use Teliax.com for almost all my VoIP and have switched from IAX to SIP a year or so ago. Partially recommended by the Teliax people. (and they have IAX in their name!)
The exact reason is harder to quantify, and transcoding (and the lack of it with SIP when using a SIP phone) is surely a part of it.
IAX's aggregation and de-aggregation seems to add jitter that is very hard to remove. It is a good idea to keep all IAX <=> IAX trunks using the same version of asterisk, this has been a problem in the past. If you have an IAX third-party-provider this might be hard to do.
Granted that SIP can be a pain with firewalls, it can be done, and is worth the one time pain for better voice quality.
My 2 cents.
Lonine
On Sep 15, 2006, at 11:59 AM, Gary G. Hendershot wrote:
Scenario:
Two Astlinux servers, main office/branch office. Calls come in via PSTN (ZAP) or SIP VoIP provider always at the main office. Inbound call will ring a number of extensions at main office and one phone located at a branch office site. Calls are routed to the branch office via IAX with a simple "DIAL(${LocalExtensions},IAX/${BranchOffice}/[EMAIL PROTECTED])".
Problem:
Calls answered in the main office are clear as a bell regardless of source (ZAP/SIP). However, calls answered at branch office tend to be "choppy" and seem to be "simplex" instead of "duplex". It is almost as if a large percentage of packets are being lost in the transfer. And when both parties speak, its a toss up which voice actually makes it. Have also noted that ZAP calls tend to have significant echo at the branch office while at the main office this is not the case.
Notes:
I noticed early on when I was experimenting with various Asterisk configurations and VoIP service providers, that the quality of sound wtih SIP seemed to be much better than with IAX. When I finally settled on a VoIP provider for production use, I went with SIP because it seemed to provide better quality.
For my "branch office trunking" needs, I am once again trying to get IAX to work mainly because of the superior NAT firewall traversal. But am once again confounded by poor quality voice. I have played around with "jitter buffers" related to IAX quite a bit and never really seemed able to resolve the sound quality issues with IAX. But I am not an expert and may have missed some simple setting that might have cleared up the problem.
The internet connection between the main and branch offices is quite good. Suspect it is superior to what most folks would use to do this task. The hardware in play is also superior to what most folks might use with more than enough CPU & memory to do the job. I cannot imagine the problem could be related to transcoding issues as the CPU utilitization on both Astlinux machines is but a blip on the radar while calls are active.
I have tried the scenario with/without VPN and have gotten same results.
Problem is also present on outbound calls made from the branch office which are routed to the main office for completion.
Questions:
Have others noticed this? Has anyone figured out a way to beat it? Should I consider just switching my branch office trunk to SIP and be done with it or can IAX be tweaked to properly do this job? Anyone out there have any tips for me on how to tweak IAX better?
Regards
G.Hendershot
_______________________________________________
Astlinux-users mailing list
[email protected]
http://lists.kriscompanies.com/mailman/listinfo/astlinux-users
Donations to support AstLinux are graciously accepted via PayPal to [EMAIL PROTECTED].
Michael Graves [EMAIL PROTECTED]
Sr. Product Specialist www.pixelpower.com
Pixel Power Inc. [EMAIL PROTECTED]
o713-861-4005
o800-905-6412
c713-201-1262
skye mjgraves
fwd 54245
_______________________________________________ Astlinux-users mailing list [email protected] http://lists.kriscompanies.com/mailman/listinfo/astlinux-users
Donations to support AstLinux are graciously accepted via PayPal to [EMAIL PROTECTED]
