[c-nsp] ospf auto-cost reference-bandwidth on modern gigabit networks

[Mark Tinka]

On 30/Apr/20 10:33, James Bensley wrote:

> Role based and metric based IGP costs are a good idea in theory. They
> are a lot more difficult in practice. Another problem with role based
> IGP costs is “who has more capacity between a pair of PEs than those
> PEs have to their upstream P nodes”? If you find yourself in that
> scenario, it isn’t role based IGP costs you need, it’s a long hard
> look in the mirror.

I disagree here.

I've built - across 3 networks on 2 continents - role-based, bandwidth
and latency-linked metrics in IS-IS since 2007.

Each of these networks was differently sized, with the latest being the
largest one, spanning several countries and 3 continents. So it does
work in practice, but it's a concept that took me about a year to
design, for each network.

And yes, I have found myself in situations where "longer" links were
required for service alongside "shorter" links due to some reason or
another, e.g., backbone failure on the path, urgent need for more
tactical capacity, e.t.c. That is okay. Networks are living things - you
have to be able to react to situations even though you have fundamentals
in place.

Mark.