Date: Wed, 20 May 92 12:20:01 CDT
From: varney@ihlpf.att.com (Alan L Varney)
Subject: Re: On Getting Telco to Correct Routing Errors
Organization: AT&T Network Systems

In article <telecom12.401.1@eecs.nwu.edu> stevef@wrq.com (Steve
Forrette) writes:

> Well, Pat, welcome to the club!  I had a very similar experience about
> a month ago, but the villian in my case was AT&T.  Only with the help
> of my LEC (US West) was the problem solved.  This is interestingly
> just the opposite of your experience.  I guess I'll start from the
> beginning:

> I live in Seattle, and my home phone is served from US West's 206-527
> exchange.  I was trying to call a friend's cellular phone on 206-921,
> which is in Vancouver, WA, and in the Portland LATA, thus an
> inter-LATA call.  When I called, I got a "Your call cannot be
> completed as dialed.  Please check the number and try your call
> again." recording.  I did both, and got the same result. 

> The problem turned out to be in AT&T's 4ESS in Seattle.  It was
> mis-routing calls from this area that were bound for my particular
> called prefix in such a manner that they were handed off to US West,
> but such that US West couldn't complete the call.

   Let me formally apologize for the run-around you got with the AT&T
Operators.  They usually do far more than required, and are a good
reason to "Choose AT&T".  But out of the thousands of queries they get
every day (including some really off-the-wall cellular ones), some are
bound to go to the wrong place or get the wrong answer.  (Of course,
this isn't an OFFICIAL apology, 'cause I'm only giving you my opinion
on this ...)

> I commented on how it must be really nice to have all of the secret
> numbers to get a hold of the proper people directly.  She said "Yea, I
> don't think I'm really supposed to call those people, but it does come
> in handy in cases like these."

   For future reference, the official listed/advertised number for
AT&T Long Distance Repair Service is: 1-800-222-3000.  It's in almost
any telephone book under: "AT&T COMPANY, Maintenance & Repair, Long
Distance Services Repair". Note that some telephone books are not very
consistent in listing AT&T in the front of the 'A' section, with the
rest of the capitalized business listings -- sometimes its in the
alphabetical order as if it were "At&t".

> So once the right person was aware of the problem, it was solved
> immediately.  But it took a lot of persistance, and some luck, to get
> through to them.  Oh, by the way, someone from AT&T Long Lines Repair
> did call me two days later to inform me that they had checked my
> account, and that my bill had been paid on time, so I should not be
> having any problems.

   Your description sounds like the Seattle 4 ESS(tm) switch was
routing the cellular NXX to the wrong Point of Presence (POP), or to
the wrong switch.  When an incoming call arrives at the first switch
in the terminating LATA, the called number is checked to determine if
this switch is a "sub-tending switch" for that number.  This prevents
an IXC from delivering a call to one end of a LATA and forcing the LEC
to tandem the call across the entire LATA.

   The LEC tells the IXCs which NXXs can be delivered to specific
switches.  In the case of direct trunks to an CO, only the NXXs
defined in that CO should arrive there.  A tandem in the LATA will
usually serve as the first terminating switch for some group of COs
(the "sub-tending COs" for the tandem).  Cellular NXXs are usually
arbitrarily allocated to tandems, since the call has to switch back
out to the cellular switch.  But this isn't always the tandem that
gets other normal LEC calls; sometimes the LEC plays games by
assigning portions of the NXX to different switches, or changes the
"location" of the NXX.  I don't know what the problem was in Seattle,
but there are certainly occasional problems relating to cellular NXXs.

   That said, I must also say that the announcement you received,
"Your call cannot be completed as dialed.  Please check the number and
try your call again.", is not appropriate for the sub-tending
screening failure I described, or for any other terminating-LATA
failure I can imagine.  I know that's what Bellcore recommends for the
screening failure (No. 40 announcement), but (as you found out), it
makes finding the problem a real PAIN for the LEC and the IXC!
Bellcore required every switch vendor to provide for a special
announcement for this failure, but then they just recommend the same
old Vacant Code announcement!

   Since this announcement can also occur for any call to Vacant
Codes, but usually goes to AIS ("The number your have reached, N N X
 ..."), one could ASSUME the announcement these days means you have hit
a situation involving sub-tending screening.

   Note that it's also an announcement that is permitted for calls
that require 10XXX dialing (non-presubscribed lines) and for calls to
800 numbers from an area not allowed to call that number
(out-of-band).  But those are probably low-probability situations.
Successfully completing the call through another carrier doesn't
assure the IXC is at fault, but does indicate there is a mis-match
between the IXC and the LEC interface.

   Hope this clears up (rather than muddies) the issue.


Al Varney - not an Official spokesperson or apologist for AT&T.