Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Path: utzoo!watmath!clyde!burl!ulysses!allegra!mit-eddie!think!harvard!seismo!ut-sally!ico!dougm From: dougm@ico.UUCP (Doug McCallum) Newsgroups: net.lan,net.dcom,net.decus Subject: Re: What is "ISO"? Message-ID: <102@ico.UUCP> Date: Sun, 6-Apr-86 15:07:56 EST Article-I.D.: ico.102 Posted: Sun Apr 6 15:07:56 1986 Date-Received: Wed, 9-Apr-86 22:20:44 EST References: <424@gould9.UUCP> <319@ptsfd.UUCP> Organization: Interactive Systems Corp., Boulder CO Lines: 57 Xref: watmath net.lan:1404 net.dcom:1794 net.decus:297 > /* Written 7:04 pm Apr 3, 1986 by djo@ptsfd.UUCP in ico:net.dcom */ > It means that they will be using some or all of the hundreds (literally) of > protocols ISO and/or CCITT are suggesting now or have in the past six to ten > years. It also means that they want you to buy their product. Partially true, but misleading. There are indeed a number of protocols definede, but they are at a number of different levels of the reference model. > Find out what they mean. A good default is (layer 1) rs-232-c/v.35; (layer > 2) LAP B; (layer 3) X.25. They may also support such things as X.75 but don't > bet on it. Layers 4 and up will be their own protocols. Some good advice. Anyone buying or implementing ANY protocol should find out what they mean. You really need to know what the standards are for each layer. This is true for protocols such as TCP/IP as well (just because two vendors support TCP/IP doesn't mean that they support the same physical media). As far as layer 1 is concerned, ISO has already adopted the IEEE 802.{3,4} families. There are standards at Layers 1-5 and Draft International Standards at layers 6 and 7. To be a real ISO network, you must support the standards at all layers. Some vendors will have their own protocols at the higher layers for services specific to that vendor. There are also "national" guidelines for the implementation of the various protocols to ensure conformance between the various vendors. For example, the National Bureau of Standards will soon issue an X.400 product description which specifies which options are mandator/optional/etc. for a US implementation of X.400. Similar specifications exist for other protocols such as transport. In essence, it will be possible to build an ISO-OSI product that will work with other vendors implementations. The MAP and TOP specifications are just such a set of guidelines. TOP specifies such things as IEEE 802.3 as the physical layer, IEEE 802.2 as the link layer, ISO connectionless network protocol at the network layer, ISO transport class 4 (NBS spec) for the transport layer, ISO session (specific subsets) at the session layer, ISO ASN.1 at the presentation layer and ISO FTAM and CASE at the application layer. There is more to it than just those, but this list specifies a full ISO protocol suite at all layers. By implementing to the specifications, compatible implementations can be made. The vendors are also working together to pass conformance tests on their products. > >What does it mean, "DECNET will conform to ISO?" > It means DEC wants you to buy DECNET. It also means that DEC will provide ISO transport protocols on DECNET. They will probably provide some of the higher level protocols as well. They have announced availability of ISO transport class 4 already. > No. The standards for layers 4 and up are WAY up in the middle of the air (see > that wheel inside that other wheel?> ) Not true! Standard protocols exist for layers 4 and 5. Layers 6 and 7 have gone to DIS form (Draft International Standard) and are supposed to go for 6 month ballot in June. There should be International Standards at all 7 layers by the end of 1986. Standards DIS level are also stable enough for an initial implementation. Transport has been a standard for quite some time. Session a little less, but it has been about a year.