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Goeller on Telecom Traffic

Introduction

My first article in Business Communications Review was an enormous two-parter in the Nov-Dec 1975 and Jan-Feb 1976 issues called "The Effective Use of WATS Lines." In those days, WATS, or Wide Area Telecommunications Service, was a business offering by the telephone company to provide phone calls less expensively than regular long distance, and more flexibly than FX (Foreign eXchange) lines or inter-PBX tie-trunks.

WATS lines were just regular CO trunks, but with special billing. Full business day WATS lines were flat rate, all you could eat for a fixed monthly fee, while measured WATS lines cost about one eighth as much for 10 hours, with a reduced cost for additional hours. The trick was how to pack calls into the WATS lines in such a way that the cost per minute of actual use saved money by being less than regular long distance, and callers did not keep getting all-trunks-busy tone with dial-up access, or wait in queue for the PBX operator to call them back when it was their turn to use WATS.

AT&T, long experienced in such optimizations, made custom designs for large customers, saving them considerable sums and, incidentally, discouraging them from putting up private microwave networks of their own which had become possible under the then new Carterfone Decision or later going to the new "competitive" long distance carriers such as MCI and Sprint. Indeed, WATS lines were so effective in reducing business telephone costs that the FCC was forced to eliminate them to make a window in which "competitive" carriers could exist. (Even that didn't do much good. All the long distance carriers of 80s and 90s, including AT&T, went broke and had to merge with local telephone companies to continue to exist.)

Initially, attendants at manual switchboards selected circuits, and/or held calls in queue until a suitable circuit came free, and recorded the call information on "mark-sense" IBM cards for processing and cost allocation. But almost immediately, a whole industry sprang up to do automatic call routing and data recording on a separate piece of equipment, allowing the customer to retain the reliability of the phone company while taking advantage of new interconnected technology where it would pay off. See "Routers, Restrictors, and Recorders--Built In or Add On? in "Voice Communications in Business, Vol. I" elsewhere in this web site. (Eventually, the makers of PBXs, telco and interconnect alike, condescended to include advanced routing, queuing and data recording internally.)

However, a tape full of raw data about phone calls wasn't immediately useful, so I wrote "Do It Yourself Programming for Call Detail Recorders," also in Voice Com in Biz-I," which was not about traffic, but how you could convert raw traffic data into something useful.

Looking back from 30 years later, there seems little point in reproducing my early WATS-related articles here. But some of my shorter, and more general, traffic articles may still be of interest. Thus my introduction to a book of traffic tables by Ted Frankel (ultimately published by ABC Teletraining), a friend from my RCA days, gives a very brief survey of what classical telephone traffic is all about.

But traffic tables, like tables for logarithms and trigonometry, make the subject unduly difficult by never quite having what you need. You always have to "interpolate" between two values in some table or other, and that is much harder than it looks. As soon as I got my first computer, in 1978, I realized that others, similarly equipped, could use some programs I had already developed to generate just the traffic values they needed. BCR published my "Programs for Traffic Calculation" in the May-June 79 issue, and many people have been using them ever since.

As telephone competition grew in the 1980s, more and more people realized they needed to learn something about traffic theory and practice. So I combined material from my several articles into a book which BCR published in 1983: "A First Course in Telephone Traffic Engineering." So far as I know, it is the first book to include a floppy disk with all my traffic programs, somewhat expanded for general use, included. I wrote the book to work with the programs, and the programs to work with the book. The text of the book is included here, without the disk and some of the material generated by programs in BASIC rather than a word processor. If we can figure how to handle the software, we may add them later.

Note that I am NOT a mathematician, and I didn't invent any of the concepts involved. What I have tried to do, as a non-mathematician, is to explain to others like me what I have finally learned the hard way. I did invent the term "Swooping Gull Diagram" for my graphic which shows how the cost per item comes down as a high start-up cost is spread over more and more items, and I recognized that, with a computer to do the work, one could use "carried" traffic, easy to measure, to replace "offered" traffic, required by most of the classical mathematics but almost impossible to really know.

I wrote three other traffic-related articles later: "Tackling the Non-Blocking Issue." "Calls, Attempts and Completions: Which Should you Specify?" and "AOL Folks at Home," each illustrating a particular problem in traffic which continues to turn up in practical experience. But now that the Internet has taken over the world, and its traffic requirements differ considerably from those of voice networks, I can safely leave the field to others. I like being retired.

Traffic-related articles by Lee Goeller

“Erlang B Tables and How to Use Them.” Telecommunications, Nov., 1975.

“Effective Use of WATS Lines.” Business Communications Review, Nov-Dec 1975 and Jan-Feb 1976.

“Introduction.” Ted Frankel, Tables for Traffic Management and Design, ABC of the Telephone, 1976.

“Do It Yourself Programming for Call Detail Recorders.” Business Communications Review, Jan-Feb 1978.

“Fun with Fax and the Worth of WATS.” Business Communications Review, Jan-Feb 1979.

“To Queue or not to Queue.” Business Communications Review, Mar-Apl 1979.

“Programs for Traffic Calculation.” Business Communications Review, May-Jun 1979.

“How Many Business Hours? Communication News, Mar 1980.

“Hourly Traffic vs. Monthly Data.” Business Communications Review, Jul-Aug 1980.

“Restrictors, Recorders & Routers--Built In or Add On? Business Communications Review, Nov-Dec 1980.

“Effective Use of the New WATS.” Business Communications Review, Jul-Aug 1981.

“At War With the CCS.” Teleconnect, Aug 1983.

“A First Course in Telephone Traffic Engineering.” BCR Publishing, Nov 1983.

“Tackling the Non-blocking Issue.” Business Communications Review, Feb 1989.

“Calls, Attempts, Completions.” Business Communications Review, Nov. 1989.

“AOL Folks at Home.” Business Communications Review, Mar 1997.

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