RE: PI/metro/geo [Re: The state of IPv6 multihoming development]

["Tony Hain" <alh-ietf@tndh.net>]

Tony Li wrote:
> ...
> Exactly.  What we want to build is a routing architecture that is 
> never going to have to be replaced.  It's too difficult to 
> reach in and change it, so you'd like it to be done right the 
> first time.  

Unfortunately 'never' is a very long time, and we will continue to do
nothing while we wait for the answer. 

> Since scalability is key and the way to scale is 
> to keep the overhead low, a solution that has higher overhead 
> is sub-optimal and to be avoided.
> 
> Geographic aggregation is fine if the topology does indeed 
> provide a convenient aggregation boundary.  But in many 
> cases, there will be no 
> such convenient boundary.  What do you do?  You cannot make 
> an exception and flat route any enterprise that has such 
> links, because then their overhead dominates the cost of all 
> routing and you're not sufficiently scalable.

This point is arguable, because it is making a blanket statement about a
process with multiple causes. For the truly global enterprise with
multiple exposure points and global internal network that could handle a
route shift, why not? There are fewer than 11,000 toady as evidenced by
the number of AS's injecting prefixes into BGP. (I suspect the real
number is less than 2,000 that could deal with taking a full traffic
load at multiple points) The real problem is that there is no clear way
to say one organization can while another can't. For the case where an
enterprise is simply looking for better/cheaper service in a remote
region, we are into economic rather than technical arguments. These
organizations aren't concerned about their impact on routing, so the
only way to deal with them is to give them the level of service they
need while making it cheaper to constrain the topology than it is to
blow out the tables. 

Tony