>Stephen Skinner wrote, let me see if i have this correct...
>
>routing protocols do the following
>
>manage links
>exchange data
>route packet
>update each other
I'd agree with exchange data and update each other. Try approaching
this from a different direction. Can we agree that the endpoints of
an application layer communication are identified with application
layer identifiers (e.g., TCP port plus application-specific
information such as email user names), transport layer communications
have transport layer endpoint identifiers (address plus port), etc.?
The routers don't have application or transport identifiers (yes, I
know about BGP). Routing protocols control devices at the network
layer. The endpoints of communication between routers are IP
addresses, even if higher-layer mechanisms such as TCP are used for
actual information transfer.
One of the problems in understanding real-world protocols is that
they may do things in an indirect manner. Think of tunneling, where
you have to do a recursive lookup of two headers to determine the
real next hop. BGP is a network layer control/management protocol
that uses TCP for its transfer.
In contrast, SNMP does work at the application layer. Its endpoints
are identified by the combination of an IP address, a UDP port, and a
MIB identifier.
>
>what his instructor is saying is that some of these functions work
>at different "layers" of the OSI model...YES i know i shouldn`t be
>using that as a reference but for this argument i will...sorry...
>so tell me OSPF....what "layers" would the above function be compared to
>
>please .....i have a major headache now as i thought i knew it
>
>>From: "Howard C. Berkowitz" <[EMAIL PROTECTED]>
>> vs Tcp/ip model
>>Date: Sat, 11 Nov 2000 08:11:34 -0500
>>
>>Your instructor is one of the all-too-large group of people who try
>>to coerce things into a simplistic OSI model. Priscilla calls this
>>coercing protocols into OSI layers. It's really not the fault of OSI,
>>because there are documents that supplement the original model, such
>>as the Rout(e)ing Framework, Internal Organization of the Network
>>Layer, Management Annex, etc.
>>
>>The OSI stack principally was drawn to show how standard
>>communications service user applications, which run on top of the
>>service interface to the application layer. Management was something
>>of an afterthought, and what is called system management -- think
>>SNMP, or the OSI rough equivalent, CMIP -- does indeed involve an
>>application layer protocol and a management application above it.
>>
>>Routing, error notification, etc., are considered layer management.
>>There is nothing "above" them; they are part of the infrastructure
>>for a given layer. So,all of them are logically layer 3.
>>
>>The issue of the mechanism they use to transfer information between
>>them is independent of the layer they manage. In Chuck's table
>>below, EIGRP and OSPF do have transport functions that are part of
>>their own design--which have a TCP-like flavor. For that matter, ISIS
>>runs directly over data link.
>>
>>>Recently an instructor in a class I was taking said something I found
>>>interesting. I hope I can do justice to his words.
>>>
>>>Network layer: IP IP IP
>>>Transport layer: TCP UDP
>>>Application layer: BGP RIP EIGRP, OSPF, IGRP
>>>
>>>In other words, he suggested that routing protocols are application layer,
>>>and use the chosen transport or network layer protocols to communicate.
>>>Other reading I have done kinda says this in other ways. RIP uses UDP port
>>>500. BGP, as we all know, uses TCP.
>>>
>>>Does this make sense?
>>>
>>>Chuck
>>
>>A post I made yesterday might help:
>>At 4:16 PM -0500 11/10/2000, Howard C. Berkowitz wrote:
>>>At 12:22 PM -0800 11/10/2000, Julian Eccli wrote:
>>>>Does anyone know the definition of Control Plane from a generic
>>>>routing protocol
>>>>standpoint? Is it the same definition as in ATM? I have heard
>>>>references to
>>>>control planes in various talks but they were not specific to ATM.
>>>>
>>>
>>>Unfortunately, it isn't as well-specified in IP routing as in the
>>>B-ISDN/ATM architecture. Many IP discussions merge what that
>>>architecture calls the control and management plane.
>>>
>>>Personally, I think merging the two is rather unfortunate. In IP
>>>networks, I consider control plane protocols those that are used for
>>>signaling between hosts and ingress/egress routers. Examples: ARP,
>>>IGMP. Another way to think about them is that they serve a
>>>user-to-network role.
>>>
>>>I consider pure management plane protocols to those used between
>>>routers: BGP, OSPF, EIGRP, RIP, etc. Arguably, these have a
>>>network-to-network role.
>>>
>>>There are protocols that don't neatly fit, such as RSVP and ICMP. I
>>>suppose they are control plane when host initiated and management
>>>plane when router initiated, but that doesn't always work and is
>>>ugly anyway.
--
"What Problem are you trying to solve?"
***send Cisco questions to the list, so all can benefit -- not
directly to me***
Howard C. Berkowitz [EMAIL PROTECTED]
Technical Director, CertificationZone.com
Senior Product Manager, Carrier Packet Solutions, NortelNetworks (for ID only)
but Cisco stockholder!
"retired" Certified Cisco Systems Instructor (CID) #93005
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