Telegraph switching V-Data communication over the telephone network X-Data networks and open system communication Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies. All rights reserved. Any use is subject to the Terms of Use as given at the website. First Things First First Things First Y-Global information infrastructure and Internet protocol aspects Z-Languages and general software aspects for telecommunication systems Within each letter designator can be found specific, numbered recom- mendations. For example, recommendation number 25 in the "X" book contains the specifications for transporting packet-based data across a public network operating in packet mode. This, of course, is the now famous X.25 packet-switching standard. Similarly, Q.931 provides the standard for signaling in integrated services digital networks (ISDN) networks, and so on. The documents are remarkably easy to read and contain vast amounts of information. I am always surprised to discover how many people who work in telecommunications have never read the ITU standards. Take this, then, as my recommendation: Find some of them and flip through them. They can be very useful. I remember very well an experience I had years ago with the ITU standards. My family was visiting friends in California, but because of work commitments I was in Vermont preparing to travel. It was a dark, snowy January night and I was sitting in front of a roaring fire, drinking a warm brandy and reading Q.931. The worst part was that I was really into it, enjoying the fact that I was understanding the technojargon. And then it hit me: I had become one of them. I was a propellerhead. I spent some time writing about the ITU and its standards activities simply to explain the vagaries of the process (one of my favorite telecomm jokes goes like this: "There are two things you never want to watch being made. One of them is sausage; the other is standards.") and the role of these bodies. Th