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Re: (ASCEND) Problems with T1<->PRI and Max4004

At 11:19 AM 3/12/98 -0500, Wes Morgan wrote:
>
>[ This message is long - you have been warned.  ]
>[ Ticket opened with Ascend, but I've been wai- ]
>[ ting way too long for a callback.             ]

Ticket number?

>Equipment:
>	Max 4004 w/DM-12,BRI,Host/Dual cards, T1<->PRI installed (5.0Ap42)
>	Meridian PBX (connected to Max via T1, D4/AMI)
>	USR Total Control modem bank connected via PBX
>	PRI circuit inbound from telco (ISDN signal, AT&T switch ESF/B8ZS)
>
>Symptoms:
>
>1) Calls to the USR Total Control modems (through the Ascend to the PBX)
>   experience a pattern of delays.  This delay occurs if the T1<->PRI link
>   is traversed, either inbound, outbound or both.  Pattern includes two
>   delays of up to 14-16 seconds, as tested with ping(1); no packets are
>   lost, but seem to be buffered.

What is at each end of the call in this case? Are voice calls to stations on
the PBX experiencing any strangeness like this? These are after all just
voice calls as far as the MAX is concerned, it has no way to know the
difference
between a station-to-station call versus a modem-to-modem call.

>2) Pattern is not present when calling DM-12 modems via the PRI.  Pattern
>   is not present when dialing USR Total Control via DID trunks (bypassing
>   the Ascend).  Pattern is not present when dialing USR via PBX (i.e. 
>   dialing local 3-digit extension to reach modem bank)

Is the delay 100% repeatable? Does it occur during a session, or is this a
session setup delay?

>3) We have two Pipelines making ISDN calls to the Max via the telco PRI.
>   They do not show this behavior.
>
>Attempted Resolutions:
>
>1) Installed new Max 4004 per RMA.
>2) Modified characteristics of Win95 DUN. (1.2b)
>3) Upgraded to 5.0Ap42 (from 5.0Ap24)
>
>Other problems:
>
>1) Channels on the T1 between the Max 4004 and the PBX occasionally hang
>   in "calling" state.  (i.e. status display is 'c')  The only way to clear
>   these is to remove the T1 from the Max for a few seconds, and then re-
>   connect it.  (These build up over time; I went 6 days without one, but
>   have seen 6 channels hang in the last 24 hours.)

"c" is 'clearing'. It means that the PBX and MAX disagree on the state of
a specific channel. This is often caused by mismatch in signaling options
and/or wink timing.

>2) DM-12 modems (v.34) cannot maintain a connection in the absence of data.

Always? Since this is a very common configuration, I would suspect a 
problem with configuration somewhere. Are you using RADIUS on the MAX?
What is configured at the client side?

>   If I *immediately* start some sort of traffic generation (i.e. FTP ses-
>   sion or 1000-ping barrage), the connection will stay up until the data
>   ends; once the data stops, the connection is dropped within 10-30 seconds.
>   (I have disabled all idle timers)

How? What disconnect code is generated?

>Supposition on delays:
>
>The T1 connection is D4/AMI, which the telco informs me is 56K data and
>8K signaling.  This is being converted to a 64K PRI data stream; the re-
>verse is taking place on inbound data.  Is it possible that this signal-
>ling change is dropping bits?  

NO. The PRI only uses 56K of the bandwidth for 56K data and voice calls.

> Is this translation particularly slow, cau-
>sing (perhaps) these delays every 30 seconds or so?  The fact that these
>delays do not occur when calling the DM-12 modems would seem to indicate
>that the telco PRI is basically healthy.

Are the delays during a session then? Maybe the modems are re-training.

>Supposition on T1 channels "hanging":
>
>I have no clue.

Signaling mismatch would be my guess. You need to get information from the
PBX on the wink setup and wink timing.

>Supposition on DM-12 modem performance:
>
>I'm at a loss on this one.  I've disabled every timeout I can find, and
>they just won't hold a connection.  I read in the 6.0 Release Notes that
>Ascend "has problems with IPX," but I see the same behavior on IP-only
>PPP calls.  I've upgraded to the latest Win95 DUN (1.2b), also per the
>6.0 Release Notes.  

Since this is not a common problem, I would still have to suspect a config
setting somewhere. Alternatively a bad modem card....did they get RMAd with
the 4004?


Kevin


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