To Chuck, I do not agree that the OSI model is "crap". Sometimes it can add confusion, but for the most part it is fairly well defined. Also, no one ever said TCP/IP follows the OSI model 100%. The concept of layering is just very easy to see with the OSI model. TCP/IP generally has only layers such as the application, network, transport, and physical. You could throw in datalink in there I suppose. It certainly helps people understand networks. Without the OSI model, it seems like a lot of random musings. TCP/IP has a very clear transport and network and application layer.
Not sure if there was sarcasm or an attack on the "reputable source" that "UDP is an application layer" part. I am going to assume so, because it's spot as a transport is very clear. So, it is wrong for me to say that ftp clients and telnet clients use layer 7? (referencing user application vs service application)? Then where would it go? No where? (hence why you say the OSI model is crap?) To Jose, I feel they do not work at the network layer, and work at the application layer. If it uses protocols, (EIGRP and OSPF) it uses IP RAW which means it skipped the transport component, ultimately I still feel it is at the application layer. Perhaps it is just my roots that routing daemons are still just daemons, programs which run on a box. They dynamically insert information into a routing table. Unix machines still do it, a Cisco router is just an appliance version of a unix box with a routing daemon with multiple interfaces. (without extraneous baggage of course) At 10:57 PM 12/13/01 -0500, Chuck Larrieu wrote: >I once had an interesting, if heated argument with someone off list about >this. IIRC, I was told by that person that Cisco, in its current CCNP study >materials, is saying just that - that something operates at the OSI layer >above which it functions. I.e. if a routing protocol uses an IP protocol >number, then it is operating at transport layer. Since BGP uses TCP port >179, it is operating at the session layer, along with RIP, which uses UDP >port 520. ( BTW, I have also read in a reputable source that UDP is >application layer because it is not reliable, and therefore cannot be >transport layer, and there is no place else it really fits ) > >I recognize that Cisco just LOVES the OSI model in the lower level >certifications, but the fact is that in terms of how things work it is crap, >and tends to cause more confusion and add no value. > >Every vendor of content switches is calling them layer 4-7 switches. what >kind of crap is that? >I dare anyone to justify switching as a layer 5 or a layer 6 activity. Yet >there it is. Also, to judge from what content switches do, the marketers are >saying the OSI layer 7 is user application, not a service application, >something Howard takes great pain to differentiate in his writings on the >subject, again IIRC. > >TCP/IP is NOT OSI compliant, never has been, never will be. OSI is a >reference model, and not necessarily related to anything in real life. > >End of rant. > >Chuck > >-----Original Message----- >From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]]On Behalf Of >Jose Luis De Abreu >Sent: Thursday, December 13, 2001 12:25 PM >To: [EMAIL PROTECTED] >Subject: Routing protocols [7:29139] > > >Just an open question ? > >We read, learn and teach Routing protocols are at the >NETWORK layer of the famous OSI model... > >But they have PROTOCOLS NUMBERS - TRANSPORT LAYER(such >as IGRP protocol 9, EIGRP protocol 88 and OSPF >protocol 89)and APPLICATION PORTS values - APPLICATION >LAYER (RIP uses port 520 and BGP4 uses port 179) >indicating they work in the upper layers and not in >the network layer, although the result is shown int >the NETWORK layer... > >So may question is... > >Do they really operate at LAYER 3 ? > >Warm regards, > >Jose Luis De Abreu > >______________________________________________________ >Send your holiday cheer with http://greetings.yahoo.ca -Carroll Kong Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=29165&t=29139 -------------------------------------------------- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
