Date: Sat, 15 Aug 92 14:50:37 CDT
From: varney@ihlpf.att.com (Alan L Varney)
Newsgroups: comp.dcom.telecom
Subject: Re: Local Call Determination
Organization: AT&T Network Systems, Lisle, IL
X-Submissions-To: telecom@eecs.nwu.edu
X-Administrivia-To: telecom-request@eecs.nwu.edu
X-Telecom-Digest: Volume 12, Issue 632, Message 1 of 13

In article <telecom12.623.6@eecs.nwu.edu> Peter M. Weiss <PMW1@psuvm.
psu.edu> writes:

>> Randy Gellens randy%mpa15ab@trenga.tredydev.unisys.com writes:

>> In Telecom 12.599, booloo@framsparc.ocf.llnl.gov (Mark Boolootian)
>> writes:

>>> Additionally, can someone explain to me what distinguishes local calls
>>> from toll calls?  Are all calls within a LATA local?  ...

   The terms "local" and "toll" are not exact opposites.  Nor are they
consistently used even within the telecom community.  So let's just
assign some arbitrary meanings here:

Free call - one that costs you nothing
Local call - untimed, but may have an initial charge
Toll call - charge depends on duration
Intra-LATA - call with origination and destination within LATA
Inter-LATA - call with origination/destination in different LATAs
IC call - places InterExchange Carrier between orig. and dest.

   Charges for a call are a "tariff" matter, negotiated with State
PUCs and the FCC.  In general, distance is a factor, as is the class
of service and location of the originating line.  For "normal" calls,
the originating CO determines the type of AMA (billing) record by:

  + location - the collection of all lines that are considered to
    be at a single point for distance calculations is usually called
    a Rate Center (ideally, the Rate is set by distance from a
    Telco-determined Center point.)  A single CO can serve multiple
    Rate Centers; from a rate-setting perspective, each Center is
    (or could be) a different CO.

  + distance - this is expressed by having logically disjoint
    tables for each Rate Center, with the "called number" as
    the key.  The associated data will contain both Charging and
    Routing information -- sometimes called CHART information.
    Routing data indicates how to reach the "called number" --
    could indicate intra-CO line or a sequence of Trunk routes
    to use.
   
  + class of service - each originator has both a Rate Center and
    a class of service; let's call the latter a COS.  The COS
    reflects one of the categories the "tariff" used for rate-
    making purposes; for example, "1-party flat rate".  The COS
    is used to index the CHART information to derive a Charge
    Index and Call Code.  These together determine if an AMA
    record will be produced, whether the call is timed, and the
    content of the record.

   In theory, all of the charging information in a CO is also in
the tariff.  But the CO doesn't know about things like Night-time
discounts, volume discounts, directory assistance credits, etc.
That's the job of the Accounting Office, where the AMA data is
processed and turned into "bills".

   Now, to (finally!) get to the questions.  

>>> Additionally, can someone explain to me what distinguishes local calls
>>> from toll calls?  Are all calls within a LATA local?  Does physical
>>> proximity have anything to do with determining whether a call is local
>>> (i.e. is it always the case that calling a couple of blocks away will
>>> be a local call)?  Assuming physical proximity had something to do

>> It is mostly distance based.  Each prefix has a set of prefixes which
>> are local from it (out here, one prefix away is local, further away is
>> toll).

   The distance (fairly directly) between the originating Rate Center
and the Rate Center of the terminating line are a major basis for
rates of longer-distance calls.  Since most COs cannot associate an
Office Code (NXX, not a "prefix" - "1" and "10XXX" are prefixes) with
more than 1 Rate Center, one could say the rate is a function of the
distance between the originating or terminating NPA-NXXs.  But for
intra-LATA calls, that's only one of many factors involved in the rate
 -- after all, the inter-office circuit costs are a small part of the
total call cost when the distance is very short.

> It is my understanding that here in central PA (USA), that a call from
> the 814-383 (Zion) exchange to 814-238 (State College) is a local
> call, but vice versa is TOLL (intra-LATA).

   There are probably instances of this within every LATA.  It is
particularly common for Independent Telcos to have one rate for
calling another LEC's lines and another for the call in the other
direction.  After all, the costs that are bundled in the rate
calculation are going to be different for each company.  Maybe one
offers a large 'free' call area and recovers the cost partly from
higher 'toll' charges.  And since the COS of the callers could differ
(let's say one is a business line), it's even more common than you
might think.

   To justify my definitions, I tried to consider as "local" all the
single Message Unit areas, hotels that charge $50 for what would be a
"free" call, un-timed coin calls, etc.  They aren't "free", but they
aren't "toll" either.  Note that there are also areas where ICs handle
Intra-LATA traffic, where every call is timed, where LECs handle
Inter-LATA traffic, etc.  Add in FX and OPX lines, and it becomes very
difficult to say which calls are "local".


Al Varney - just MY opinion.