North American Network Operators Group

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Re: [nsp] IS-IS over IP?

  • From: Howard C. Berkowitz
  • Date: Tue Apr 04 11:22:40 2000

The ISIS WG in the IETF is (/was) working on an "ISIS over IPv4"
specification, though it's value has become somewhat questionable.

Initially, I beleive there were a few drivers such as removing the
requirement for the OSI CLNP support, and the need for more efficient
"ISIS over [something] over ATM" so that AAL5 SNAP could be replaced
with AAL5 MUX or the like to alleviate overhead required for protocol

However, workarounds have been provided for the ATM overhead issue and
the "ISIS over IPv4" specification itself seems to have become more of
an academic exercise.

A few good things did come out of the WG, however.  See

for current working group information.


I wasn't in Adelaide, but in earlier meetings, I had the impression that there were at least some implementations using IPv4 as a workaround both to lower layer specific problems (e.g., AAL SNAP/MUX) as well as the hard MTU size limit due to lack of fragmentation capability at the data link layer.

Disclaimer: I'm developing requirements for Nortel's carrier routing products.

 > ISIS is a routing protocol that runs over ISO/clns - so what is your
 > question ?
 > /Jesper
 > --
 > Jesper Skriver, jesper(at)skriver(dot)dk  -  CCIE #5456
 > Work:    Network manager @ AS3292 (Tele Danmark DataNetworks)
 > Private: Geek            @ AS2109 (A much smaller network ;-)
 > One Unix to rule them all, One Resolver to find them,
 > One IP to bring them all and in the zone to bind them.