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G729 G.729 G 729, AT&T is stating a new SIP reqmt for G729 2

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TrentGreenawalt

Technical User
Jan 18, 2002
159
US
We have two 3300 controllers, running on the IP Flex network of AT&T. We chose to go with SIP connections at both sites due to a huge cost savings over a traditional PRI. We have 12 SIP channels at our main branch and 6 SIP at our branch office. We are connected to each other via 1.5 MPLS, and we have a 3.0meg internet/voice connection at corporate, and a single T-1 voice/data at the branch. As far as I “know” we have and still are running G711 for all voice/fax/VM/auto-attendant/MOH traffic.

We went live Aug/Sept of last year 2010. At the time, we did not purchase the DSP modules or G729 compression licenses, and our installation went smooth (for the most part). I assume we didn’t need them, nor had I even heard of this G729 except in passing. Sure we had our issues here and there, but sooner or later they were mostly resolved except for one. We were never able to get MOH (Music on Hold) to broadcast outbound, on an outside call transferred back outbound. Example: Owner calls in on cell, receptionist can't find who he is looking for, so he asked to be transferred to (Joe's Cell), when the owner is placed on hold while the receptionist is transferring to Joe's cell, he hears dead air, then when the phone is ringing (even after release by receptionist) he hears nothing until Joe picks up.

We went round and round with AT&T and Mitel and neither wanted to own up to it. During the troubleshooting of this case (note: it has been 9 months now), an additional MOH problem came to light.

Enter the gorilla in the room, we lost any/all music on hold (MOH) outbound in any scenario, now according to AT&T they are supposedly REQUIRING G729 in order for the 3300 to communicate with AT&T routers (IP FLEX) network. I am not sure on the "AT&T corporate statement" on this, but this is what we got from a tier 3 tech on a conference call with about 8 other AT&T brass.

Furthermore, it was "implied" that if we didn't buy the G729 licenses and DSP card from Mitel that we could potentially lose outbound VM access, auto-attendant, and a few other voice type items. From what I understand, the only reason our 3300 is working with IP Flex SIP right now is due to the phones we use 5320-5330-5340 which natively compress voice to the G729 codec by default.

So I know this is a lot to digest, but we are sitting here with a $5k bill to "upgrade" just to get our MOH music on hold to work, and potentially stop a serious outage down the road. According to the AT&T tech, AT&T will be putting in protection mechanisms into their routers to will stop all G711 "voice" content. The only reason AT&T allows some form of G711 is for Fax use, when the user don’t use T38 for faxes, and the "loop hole" they "fixed" (broke in my case), was they were allowing our MOH to go out thinking it was a fax transmission. They now deep inspect the packets and have stopped this ability.

What do we do? What would you do? If this is in fact true, it will have a HUGE impact on both Mitel customers and AT&T as well. I personally think that Mitel should be making this baseline if this is fact the case. We did work with a vendor, but I don’t think it is their “fault” either.

Thanks for the help,
Trent Greenawalt


Best Regards,

Trent Greenawalt
IT Manager
Milwaukee, WI
 
Interesting.. Did they give any reason why they require G729 compression?

The single biggest problem with communications is the illusion that it has taken place.
 
No not yet. I have requested documentation a few times. Has anyone else ran into this problem?

Best Regards,

Trent Greenawalt
IT Manager
Milwaukee, WI
 
Doesn't make a lot of sense. Although the bandwidth is less for the 729, the header info eats it up. You should be able to force your codec in the sip peer profile.

NO GOOD DEED GOES UNPUNISHED!
 
not related to your G729 issue but does
SIP Peer Profile
SDP Options
Avoid Signaling Hold to the Peer
(added in later MCD versions)
make any difference to music on hold during transfers?
we had to do this, to get MoH from the Mitel to work (otherwise the SIP provider was playing their own music on hold)

the no sound/MoH during transfer of external call to external call sounds a bit like an 'answer supervision' issue (but not sure what control you have over that in a SIP scenario)

Neil
 
Not encoutered but not in US. No issues with uncompressed SIP trunks on any site I have encountered them on. Thats why I was curious about the reasoning for AT&T wanting compressed.

The single biggest problem with communications is the illusion that it has taken place.
 
We have a similar setup but we have a lot of simultaneous calls so we went with G729 out of the gate to help reduce bandwidth issues due to inbound call volume. i thought you could tell carrier to deliver G729 and set the SIP peer profile the same. i know if u put call on hold or vmail it would then uncompress the call but that rarely happens in our case
 
So a small update to this is that I have "confirmation" verbally, but nothing on paper/pdf that AT&T is requiring G729 right now for all users of their SIP IP Flex service. I still find this hard to believe and like I stated above have yet to receive a formal "requirement".

So basically we are going to have to spend another $5k, 8 months after install just to make our phone systems work 100% again. I find this rediculous and would like some answers. The problem is I shook too many trees and now the big wigs have gotten involved and I am out of the loop from the technology side of things.

Best Regards,

Trent Greenawalt
IT Manager
Milwaukee, WI
 
We bit the bullet and bought the DSP card and 8 compression licenses for each site. It is expense, but a necessary evil. On the flip side we technically doubled our bandwidth..since all calls should be half the size from now on right?



Best Regards,

Trent Greenawalt
IT Manager
Milwaukee, WI
 
Each call will require less bandwidth when compressed so yes you are using less. So your 12 SIP trunks will use less bandwidth which is a great help to the carrier but don't know if it does you any good. Wonder if compression will effect calls like fax?

The single biggest problem with communications is the illusion that it has taken place.
 
Just wondering out loud here...
What would happen if an Asterisk box was set up between ATT and the 3300. The Asterisk could compress to the carrier and g711 to the PBX.
Aside from being a pain and having another point of failure I'm thinking this might work and I don't think the server would have to be that hefty.

Dry Aquaman

 
Loopy, you bring up a good point that I will address with the VAR. I am hoping that they will still be able to push out faxes on G711, since AT&T still allows G711 for faxes. Otherwise, I assume I will need to go T38 route which I assume are additional licenses as well. Thanks for the heads up. I will let you know how it goes.

I like your comment on how it helps the carrier, but not us...Nice!

Aquaman - asterisk, that is another phone system correct? Open source I believe right. So basically you are talking about compressing the calls after the 3300 and before it hits AT&T right. That would be entirely over my head, so though I am sure it is a great idea and most likely "free", I think we will stick with doing everything in the 3300. Thanks for the idea though.

Trent Greenawalt

Best Regards,

Trent Greenawalt
IT Manager
Milwaukee, WI
 
According to them they will put the fax lines into zones so the calls don't get compressed is their work around for that. Sounds good to me. I am just pissed we have to pay $5k for MOH to work!

I still don't get why my MOH works outbound, my auto-attendants work, and my outbound VM works...No one has an answer for me at AT&T, and I don't want to ruffle feathers or they will figure out why and shut us down!

Best Regards,

Trent Greenawalt
IT Manager
Milwaukee, WI
 
Hmmm,we have Paetec in our area I think. Perhaps AT&T will foot the bill since it is them demanding the service. Unfortunately, is it the fact that we know someone at AT&T and that is why this is a problem. I bet the person hear that knows the person their is getting their $5k back in some sort or fashion..ie perks....:)

I just hate that we are all in the dark on this G.729 requirement and still have yet to see the requirement.

Best Regards,

Trent Greenawalt
IT Manager
Milwaukee, WI
 
Don't know why they need G.729. You bought 12 SIP trunks and after compression you still only get 12 SIP trunks ( at poorer audio quality ) but the carrier gets to use a smaller date service to deliver them. Hmm who wins there. Plus if its a fax they acutally will deliver it uncompressed so why the need for G.729 again?

Have you met my friend Ben Dover?

The single biggest problem with communications is the illusion that it has taken place.
 
I have met him numerous times while dealing with AT&T. Go figure...

Best Regards,

Trent Greenawalt
IT Manager
Milwaukee, WI
 
Grab a wireshark trace of the SIP session and you'll see what they are doing.

My guess is that they will offer G711 and G729 initially, with G729 preferred. If you select G711, then it will allow it until it can inspect the payload to look for the CNG tone (fax indication). If it doesn't see it within a timeout, it would re-invite to G729 only.

Getting a SIP trace will quite easily determine who is enforcing what.
 
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