PRI Headache!

[MDTV]

Hi all, I am an admitted novice when it comes to all things telco, but I'm learning quickly!

I have a single PRI terminating in a Tandberg MPS 200 (MCU/Gateway.) Our service provider is a local/regional carrier (Citynet.) We arranged to have our LD calls routed through AT&T.
Local calls set up as we want them to...inbound and outbound. LD calls connect on one channel, but then fail after a few seconds. There appears to be no attempt to dial the remaining 5 channels (for 384kbps.) Calls designated as "Telephone" calls are made and received without issues.

I initially thought this was a bonding issue, but attempting to connect on a single channel (64kbps - NOT designated as "telephone") fail in the same way the higher bandwidth calls do. Would this indicate that this is not a bonding issue?

I don't have very many test numbers to dial, but I'm pretty sure the devices I'm attempting to reach are served by Verizon. I'm wondering if the Verizon network is blocking the calls...even though calls dialed as "telephone" work fine.

Any ideas? And does anyone know of a test number served by AT&T?

[Joe Vallender]

There should be no reason for Verizon at the far end to be blocking your calls, only your LD provider if you're not authorized. Both Tandberg and Polycom have video test numbers on their web sites. Have you tried 56K restricted rate calls? You may need to open a ticket with your local provider to capture your D-channel setup message(s). What about any logs on the MPS200?

[11B-33T]

Sounds like his LD carrier is not configured for data grade (64k) calls. Joe is right about trying Nx56k calls to see if those work. Can you receive LD in-bound Nx64k calls? (I see you wrote 'telephone' calls work)...

[Sean Lessman]

Calls designated as "Telephone" calls are made and received without issues.

Yes, sounds like you don't have the right bearer capability. Lines may be set up for voice only with no data (video). This can be seen if you do an ISDN trace in the MPS and get a friendly TANDBERG techie to interpret for you, unless of course you speak Q.931 :)

Sean

[MDTV]

Well, I found out that our DID numbers have not been loaded into AT&T's system yet for LD. I suppose any issues I have are moot until that happens.

Regarding Nx56k calls...I don't see any way to force 56k calls through the MPS. My understanding is that the default setup [Restrict (56k) UNCHECKED] will allow downspeeding to 56k if necessary. With the box checked, it will not allow 56k at all...correct?

[Sean Lessman]

Regarding Nx56k calls...I don't see any way to force 56k calls through the MPS. My understanding is that the default setup [Restrict (56k) UNCHECKED] will allow downspeeding to 56k if necessary. With the box checked, it will not allow 56k at all...correct?

Its not so much the 56k vs 64k as it is the bearer capabilities. In ISDN you have the ability to request services of the ISDN line (there are quite a few services available for ISDN), some common ones are below:

88 90 data, 64 kbps
80 90 speech, 64 kbps

If your service is not configured for both voice and data, when you request a service from the terminal, the network will not allow the call, or possibly drop you down to the service you do have. In other words, you request data but only get voice.

You can see the interaction with the ISDN switch in the ISDN trace from the MPS, if you know what you are looking for.

Sean

[MDTV]

Here is an ISDN trace from our MPS for a failed 384k video call:

00:02.61 0 1 TE: sapi=0 cr=0 tei=0 I ns=35 nr=110 pf=0
pd=8 (Q.931) cref=29 (hex=001D,f=0)
SETUP
Bearer cap: 88 90
ITU-T, Unrestricted digital information, 64k circuit
Channel id: a9 83 97
PRI, Exclusive, not D-ch., as indicated
ITU-T, B-channel number 23
Clin numbr:
Number type : Subscriber
Number plan : Unknown
Calling number: 304*******
Cled numbr:
Number type : National
Number plan : Unknown
Called number : 1703*******
00:02.62 0 1 NT: sapi=0 cr=0 tei=0 RR nr=36 pf=0
00:02.70 0 1 NT: sapi=0 cr=1 tei=0 I ns=110 nr=36 pf=0
pd=8 (Q.931) cref=29 (hex=001D,f=1)
CALL PROCEEDING
Channel id: a9 83 97
PRI, Exclusive, not D-ch., as indicated
ITU-T, B-channel number 23
00:02.70 0 1 TE: sapi=0 cr=1 tei=0 RR nr=111 pf=0
00:03.75 0 1 NT: sapi=0 cr=1 tei=0 I ns=111 nr=36 pf=0
pd=8 (Q.931) cref=29 (hex=001D,f=1)
DISCONNECT
Cause: 83 90
ITU-T Q.931, Transit network
Normal clearing (16)
00:03.75 0 1 TE: sapi=0 cr=1 tei=0 RR nr=112 pf=0
00:03.87 0 1 TE: sapi=0 cr=0 tei=0 I ns=36 nr=112 pf=0
pd=8 (Q.931) cref=29 (hex=001D,f=0)
RELEASE
00:03.88 0 1 NT: sapi=0 cr=0 tei=0 RR nr=37 pf=0
00:03.88 0 1 NT: sapi=0 cr=1 tei=0 I ns=112 nr=37 pf=0
pd=8 (Q.931) cref=29 (hex=001D,f=1)
RELEASE COMPLETE

[Sean Lessman]

Bearer cap: 88 90
ITU-T, Unrestricted digital information, 64k circuit

Your local switch supports the bearer cap 88 90 (data 64k unrestricted)

Calling number: 304*******

Ahhhh West Virginia :)

CALL PROCEEDING
Channel id: a9 83 97
PRI, Exclusive, not D-ch., as indicated
ITU-T, B-channel number 23
00:02.70 0 1 TE: sapi=0 cr=1 tei=0 RR nr=111 pf=0
00:03.75 0 1 NT: sapi=0 cr=1 tei=0 I ns=111 nr=36 pf=0
pd=8 (Q.931) cref=29 (hex=001D,f=1)
DISCONNECT
Cause: 83 90
ITU-T Q.931, Transit network
Normal clearing (16)

Looks like the local switch is ok, and at the same time it is sending you a Call Proceeding, it is also trying to talk to the next switch up the line (could be AT&T long distance). Something goes wrong and the local switch hangs up. You know it is Network and not the Terminal (codec) because the Disconnect was issued by the 'NT'.

My guess is the next switch up the line rejected the call for whatever reason (lines not configured properly, no service etc). Knowing AT&T, a common place to look is to make sure your Calling Number (304*******) is loaded into their global ISDN database. If your 'callerID' isn't in the database, they will allow voice calls, but no data (video). We see this all the time...

Just a FYI, the 703 number you were dialing is on an AT&T circuit here in Reston.

Sean

[MDTV]

Ahhhh West Virginia :)

Go Mountaineers!


Knowing AT&T, a common place to look is to make sure your Calling Number (304*******) is loaded into their global ISDN database. If your 'callerID' isn't in the database, they will allow voice calls, but no data (video). We see this all the time...

Yep, that's what they're working on right now.

Just a FYI, the 703 number you were dialing is on an AT&T circuit here in Reston.

I got that number from a Tandberg tech I was on the phone with for about 2 hours yesterday (with my local provider.)

Thank you, this is very helpful. Hopefully I'll follow this up with good news shortly (though I'm not optimistic :happy: )

[MDTV]

Success!...sort of.

I can now dial out through the AT&T network. I tried a bunch of numbers (including international) and none of them failed.

The bad news is, I can't receive calls...a tech at Tandberg tried calling me and got a "resource unavailable" error.

My local provider says he doesn't even show any calls attempted to my numbers. Any ideas where to start with this one?

[11B-33T]

The bad news is, I can't receive calls...a tech at Tandberg tried calling me and got a "resource unavailable" error.

My local provider says he doesn't even show any calls attempted to my numbers. Any ideas where to start with this one?

If the LEC never sees it traver in, then it would not be the first time AT&T gave a site LD (national & international) ISDN with no 'in-bound' provisioning capabilities. Have them (AT&T) check it for you...

[MDTV]

If the LEC never sees it traver in, then it would not be the first time AT&T gave a site LD (national & international) ISDN with no 'in-bound' provisioning capabilities. Have them (AT&T) check it for you...


But would this even have anything to do with AT&T? I was assuming that inbound calls should come straight to my local provider's switch.

[11B-33T]

True, in-bound calls come to your LEC and are routed to you. You said earlier that you can initiate/receive local calls and you had issues with LD calls outbound failing after one channel connects. You said LD outbound issues have been resolved, but now you can't receive in-bound LD calls from tech support at Tandberg correct?

[MDTV]

That is all correct.

[11B-33T]

OK, now the LEC never sees the call come in their circuit that's routed to you so I'm inclined to think that where the 'hand-off' of in-bound LD (could be at the MUX in the LEC facility) is supposed to occur is failing due to possible routing or class of service permissions for your PRI lines. Suggest you open a trouble ticket to have it checked. Have you had any other LD sites attempt to dial-in as well?

(BTW, I'm not the TDM switch guru in these here parts but I did pass by a Holiday Inn Express on the way to work! :p- )

[MDTV]

I'm up and running now, inbound and outbound.

Thanks everyone for your help and input. This is a great resource. I only hope that I have the opportunity to "give back" at some point.

[11B-33T]

:confused: So what was the issue and how did they resolve it?

[MDTV]

Well, I still don't know why the Tandberg tech couldn't dial me. From talking to my LEC, it seems that the Tandberg local switch in Reston, VA won't recognize numbers from my provider...they apparently need to be notified so they can load the info. Either that, or the tech wasn't dialing it correctly.

Either way, I was able to receive calls from several other units around the country using different carriers. That's good enough for me (for now.)

[Sean Lessman]

it seems that the Tandberg local switch in Reston, VA won't recognize numbers from my provider...they apparently need to be notified so they can load the info.

If you pull the other leg it plays jingle bells :)

He is basically implying that your number needs to be uploaded to every switch in the world for you to be able to make calls. Hmmm.

I would believe there is some sort of AT&T database config problem that prevents you from dialing a specific number. Maybe that is what he meant ;)

Either way, I was able to receive calls from several other units around the country using different carriers. That's good enough for me (for now.)

Excellent! Congrats!

Sean

[MDTV]

He is basically implying that your number needs to be uploaded to every switch in the world for you to be able to make calls. Hmmm.

I would believe there is some sort of AT&T database config problem that prevents you from dialing a specific number. Maybe that is what he meant ;)

Sean

Actually, this is just for receiving calls. I can make calls to your Reston office just fine. For some reason you guys can't call me from there.

[flo]

It is nonsense to replace the number with *******

lin numbr: c0 33 30 34 35 35 34 30 30 35 31
Number type : Subscriber
Number plan : Unknown
Calling number: 304*******
Cled numbr: a0 31 37 30 33 34 33 37 36 39 39 34
Number type : National
Number plan : Unknown
Called number : 1703*******

actually, it is easy to be decoded from the log enclosed.

Calling number is 3045540051
Called number is 17034376994

right?

[Sean Lessman]

actually, it is easy to be decoded from the log enclosed.

Calling number is 3045540051
Called number is 17034376994

right?

Yep, I think he was trying to hide the number in the public forum :)

Sean

[MDTV]

It is nonsense to replace the number with *******


right?


Uhh, yeah. I realize it can easily be figured out, but it doesn't exactly jump out at you as a phone number in long form, does it?

An edit would be appreciated.

[Unclefester]

I installed an MPS 200 as a gateway only and one PRI. We had issues receiving calls. It turns out we didn't add a dialing rule for the inbound calls i.e ISDN to H323. Once we got that set up everything worked fine. This problem went on for a while and even product support from TB was called in. It's one of those simple things that can bite you in the butt if you don't pay attention.

[LAJones]

We recently replaced a Polycom unit with a Tandberg 6000 MXP Codec. We have a full T1 ISDN-PRI. After the install, we were not able to receive any incoming long distance calls. It would try to connect to one channel and hang at "64kbps, please wait" and then drop the call. After lots and lots of lost hours, we finally found the solution to our problem.

We cleared the second set of numbers from the "number range" block under ISDN/External/Leased E1/T1, ISDN-PRI settings. You only enter a number in the second block if you have Cascading Tandberg Codecs, which we don't, we just have one single unit. Once we cleared that second "number range" block, we are able to receive incoming long-distance calls all the way up to the full 1472kbps. Yay!

[robertk]

We cleared the second set of numbers from the "number range" block under ISDN/External/Leased E1/T1, ISDN-PRI settings. You only enter a number in the second block if you have Cascading Tandberg Codecs, which we don't, we just have one single unit.


Can you cascade 2 MXP codecs??? I belive that this function was on the TANDBERG CLASSIC 6000 but was never implemented on the 6000 MXP codec.

Have I missed something in a release note :)

Sean, maybe you can answer this one?

//Robert

[Sean Lessman]

Can you cascade 2 MXP codecs??? I belive that this function was on the TANDBERG CLASSIC 6000 but was never implemented on the 6000 MXP codec.

Have I missed something in a release note :)

Sean, maybe you can answer this one?

//Robert

correct, the 2nd PRI port on the MXP is not live today.

Sean

[MDTV]

I'm resurrecting this old thread to try to figure out my problems receiving calls. As stated earlier in the thread, my outbound calling works fine.

After dealing with our circuit for a while now, I find that only 1 in 5 (if that) external callers is able to dial into my MPS, so I always have to initiate (and thus pay for) the calls.

Can someone give me an idea of a starting point when I reinitiate the dialogue about the issue with my LEC?

[Joe Vallender]

If the calls are not being presented to your PRI from your LEC then they need to set up traps to see if the calls are hitting them and what they are doing with them. Could it be that calls from specific LD carriers to the LEC are failing? Do you have a test number to dial? I could place some test calls to see where they go and if successful.

[MDTV]

Thanks, Joe. I'll send you a message with a dial-in number.

And yes, I do believe that it is a matter of specific carriers. I haven't figured out which ones yet. The PRI can receive telephone calls from anywhere in the U.S., internationally...wherever. Incoming video calls have spotty (at best) success.