Protocols come in family trees. They are the result of a marriage of often many different organisations, firms, state bureaus etc.
My own version of the ASN.1 origins: In the mid- to late 1980'ies the big challenge was how to transfer communication from "snail mail" to electronic mail, or more generally how to transfer files via telecomms networks. The Americans had come up with the Internet which had both email and ftp functionality. The UN body of countries - in CCITT (now ITU) wanted - or the majority of them agreed to - come up with a more state controlled - i.e. a more hieracically divided model for communication between data processing nodes - So this union of interestes came up with the X series of protocols. That included the OSI 7-layer model for communication, X.400 electronic mail, FTAM for file transfer, plus a lot of other standards. Out of the work with X.400 grew ASN.1. While working on the Blue book version from 1988 of CCITT (ITU) protocols ITU formed a "union of interests" with ISO - these two bodies formed the "Joint-CCITT-ISO-working-group" (called something in the vicinity of this) so standardisation was now taking a rather big step towards this X family of protocols. However the internet had advantages that the X-series of protocols did not posess. Not at that time at least. And the internet kept growing while the international community was working on the X series of protocols. The internet protocol has this wonderful ability of automatic configuration. Network philosophers can probably write a whole book on this. And have done so. It has a wonderful simplicity about it. A simplicity won by the fact - in my opinion - that it grew out of a single mind - or a few minds -instead of being the result of a great compromise between thousands of minds, like the case of the X series of protocols. If this is completely wrong then please correct me... So now to your question: Protocols in the family tree of X.400 have inherited ASN.1. ASN.1 was also by marriage of interests inherited into the Q series where it got adopted for ISDN, UMTS, and so on. -------------------------------------------------------- Then you might ask: Why do we still need to consider ASN.1 when designing new protocols ? ASN.1 replaces the old-fashioned way of designing protocols by drawing little boxes with bits and bytes. These little drawings had the disadvantage that every now and then some standardisation group would interpret the reading direction in an new manner: From left to right, right to left, from top to bottom, bottom-and-up and so on. While in a protocol analyser firm I had the pleasure of trying to figure out what was meant by thousands of these little drawings. At some point you get fed up and say: "Why cant someone make a general rule of specifying bits and bytes on the line instead of this confusion" ? Now - in approx 1990 when I had reached that state - I was asked to implement the Mobile Application Part (MAP) of GSM prase 1 for a protocol analyser. (ETP71 if anyone on this list still should remember it...) And there was the answer of all my dreams.... A language that once and for all would stop this never-ending discussion about how to specify reading directions for procotol elements i.e. the *semantic* aspect of protocol specification seemed to have a solution. I reckon there is no time for protocol history left when designing a new protocol. So a design group should choose the language that they think will bring them closest to their goal in the most efficient way. (i.e. fastest and safest) Finally I'd say: Go for ASN.1. Its implementation can be changed very fast through choice of encoding rules (BER DER CER XER PER...)to suit various needs. Use as few language elements as possible to get there. Don't go for anything fancy. ASN.1 got too inclusive underway but that is explainable. read through the brief history above and realise how many minds the spec has been through. So many different needs, speculation on future needs etc.. So cut it down. make it simple. get there fast and safe. regards Steen Oluf Karlsen Søholtvej 6 Vester Vandet DK-7700 Thisted Danmark Tel +45 97 97 72 72 email [EMAIL PROTECTED] -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] Behalf Of ajay singh Sent: 27. september 2003 11:41 To: [EMAIL PROTECTED] Subject: [ASN.1] why ASN.1 is used in some protocols and not in others Hi All, I have been asked this question many times. Why ASN.1 is used in certain protocols only and why not in others? Are there any criteria to use ASN.1 ? Ajay ______________________________________________________________________ __ Yahoo! India Matrimony: Find your partner online. Go to http://yahoo.shaadi.com
