[20476] in North American Network Operators' Group
Re: IGPs in use
daemon@ATHENA.MIT.EDU (Henk Smit)
Wed Oct 14 13:02:18 1998
Date: Wed, 14 Oct 1998 08:28:21 -0700 (PDT)
From: Henk Smit <hsmit@cisco.com>
To: tli@juniper.net (Tony Li)
Cc: nanog@merit.edu
Tony Li wrote:
>From a theoretical perspective, they both scale exactly the same. To wit:
>a two level hierarchy, with SPF within each level. Given ideal conditions,
>one could reasonably build a 160,000 router network with either protocol
>today without too much difficulty (400 nodes per area).
>
>From a practical perspective, the implementation differences and topology
>issues dominate their practical applicability.
When one compares the complexity of the SPF calculation itself,
both OSPF and ISIS scale in a similar way.
The way routing information is packaged in LSAs and LSPs is different.
They way those LSAs and LSPs are flooded is different too.
I think these difference are more important when one compares scalability
between ISIS and OSPF.
Henk.
