>So IS-IS does NOT comply with the OSI model? ;->
It's perfectly compliant with the OSI Routeing Framework (yes, it's
spelled that way) and the Internal Organization of the Network Layer.
Unfortunately, the World According to Cisco Training stopped OSI at
the Reference Model proper (ISO 7498), not any of the annexes to it
or the supplementary architectural documents.
Apropos of a question Priscilla avoided, ARP, in formal OSI terms, is
a subnetwork dependent convergence facility, which again is a part of
the Internal Organization of the Network Layer. In the B-ISDN
reference model, ARP is a control plane protocol.
And before anyone asks, these ISO documents are not available online,
or at least free.
>
>Seriously, Howard, when you say that IS-IS operates at the MAC layer, what
>do you mean?
ISIS does not encapsulate its routing packet in any layer 3 routed
protocol (i.e., IP or CLNP).
>When I do a debug isis adjacency on a Cisco router, is what I
>am seeing ( is-is "hello" packets of various sorts, depending on the
>configuration ) evidence of MAC layer activity as opposed to the broadcast
>activity of RIP or the multicast activity of OSPF?
Right. Mind you, there is little practical difference between direct
data link and OSPF's IP packets with TTL=1. (Pause for usual
mystification on why someone wants routing protocols to pass through
a firewall, a fairly frequent question).
>
>Chuck
Message Posted at:
http://www.groupstudy.com/form/read.php?f=7&i=190&t=132
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