Re: Requirements for IP Multihoming Architectures

[Joe Abley <jabley-ietf@automagic.org>]

On Wed, Mar 21, 2001 at 04:04:58AM +1100, Geoff Huston wrote:
> >  + path or prefix bloat (the prefixes announced by the multi-homing
> >    site can be aggregated by the single provider)
> 
> path bloat is bad becuase?
> 
> I'm not sure I understand why path bloat is evil in and of itsxelf.

My understanding was:

  The larger the number of paths per prefix, the more expensive it is
  to walk the tree and do path selection. This impacts convergence time
  when processing updates and withdrawals (or, conversely, places greater
  demands on router hardware to manage acceptable convergance).

This is based on the assumptions that:

 + walking the tree is expensive,

 + walking a larger tree is more expensive,

 + network-wide convergence time increases with the time taken
   for individual nodes to process changes, and

 + the time taken to converge following changes needs to be controlled
   (within the observed period of oscillation of changes received from
   other networks, perhaps).


Joe