Re: [Linux-decnet-user] protocols
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From: Paul K. <pk...@eq...> - 2002-04-28 20:17:26
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Excerpt of message (sent 28 April 2002) by Brendan Minchin: > Can you please tell me the layers of the DECnet protocol and compare > them to the OSI seven layer model? Also can you tell me where to get > info about each layer in the DECnet? I meant to answer that first question too... Decnet phase 4 predates the OSI model. Phase 5 had a number of its layer names changed so they wouldn't be as confusing to someone who reads the OSI model. Apart from that, the two have basically the same layering: Osi Phase4 Phase5 7 apps apps 6 - - 5 (NSP) Session Ctl 4 NSP Transport 3 Transport Routing 2 Data Link Data Link 1 (data link) Physical So there's a pretty close match with two or three exceptions. Phase 4 does not have a separate physical layer nor a separate transport layer; you can see the functions of these two as part of the data link and transport layers, respectively. There is no layer 6 -- but then again, I don't think there has ever been a layer 6 in recorded history. Finally, the names are different, which isn't all that bad except for layer 3, which confusingly is called "transport" in Phase 4. (Layer 4 is "NSP" which if you expand it also becomes confusing: "Network services protocol". So just keep it as "NSP"!) paul |