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Re: ISIS versus OSPF as IGP

  • From: Daniel Jackson <daniel@cplane.com>
  • Date: Tue, 13 Aug 2002 14:29:10 -0700
  • Resent-Date: Tue, 13 Aug 2002 18:35:58 -0400
  • To: mpls-ops@mplsrc.com

fraanro writes:
 > > 
 > > what is the recommended IGP for an MPLS TE using RSVP? ISIS or OSPF?
 > > 
 > The only difference is that for TE updates, ISIS uses different 
 > different TLVs for each update, whereas OSPF may include more info in a 
 > single TLV object. 

ISIS is somewhat more efficient in the way it uses the space in the
packet - multiple TLVs of different types can be put into the same
packet.  With OSPF, in general, each different LSA type uses a
separate packet.

ISIS also has partial recomputations of the topology for certain types
of minor failuers.  OSPF must do a full recalculation of the topology.

ISIS appears to be a bit more scalable than OSPF.  There's at least
one ISIS deployment with over 1000 routers in the domain.  The largest
OSPF deployments seem to max out at roughly half that.

I don't think it matters all that much which protocol is used.

Daniel

--------
Daniel Jackson
Network Engineer
CPLANE, Inc.
daniel@cplane.com

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