Re: link avoidance

[Scott Whyte <swhyte () gmail com>]

On 5/6/15 15:56, Randy Bush wrote:
> a fellow researcher wants
>
>      > to make the case that in some scenarios it is very important for a
>      > network operator to be able to specify that traffic should *not*
>      > traverse a certain switch/link/group of switches/group of links
>      > (that's true right?). Could you give some examples? Perhaps point
>      > me to relevant references?
>
> if so, why? security?  congestion?  other?  but is it common?  and, if
> so, how do you do it?

My experience has been with MPLS overlays.

Availability: During maintenance windows, moving high-value traffic away 
from potential outages while keeping the tunnels full of BE; manually 
manipulating MPLS tunnel affinities (though this could be automated 
fairly easily).

Congestion: Whenever traffic load spikes past a threshold; 
diffserv-aware TE to prevent certain classes of traffic from routing 
over links with limited bandwidth, handled automatically via auto-bw.

Preventing non-optimal tunnel paths.  No transoceanic trombones, 
please; MPLS link affinities designed into the network.

-Scott