RE: Geo pros and cons

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

Tony Li wrote:
> Iljitsch,
> 
> |    Now obviously it is possible to lease a circuit to a 
> |    remote location 
> |    and connect to "the internet" in that location rather than 
> |    close to 
> |    home. But should we consider this a feature we must 
> |    support, or is it 
> |    an exceptional situation that we can safely ignore?
> 
> 
> Since this happens all too frequently, we must deal with it.  
> The Internet is not a centrally run function.  Instead it 
> grows organically by the needs of the users.  In other words, 
> the links only show up where they make economic sense.  And 
> those are the links that users will use, ignoring the consequences.
> 
>     
> |    Since the scalability of geographical aggregation depends 
> |    on the number 
> |    of internet users and the size of the aggregation areas, 
> |    where each 
> |    aggregation area needs at least two interconnects, it 
> |    would seem that 
> |    the scalability of geographical multihoming isn't a 
> problem: more 
> |    multihomers means more routes in an area, but since more 
> end-users 
> |    means more interconnects, the areas shrink. So the number 
> |    of routes per 
> |    area should remain fairly constant.
> 
> 
> If the routes are proportional to the number of areas and the 
> areas are growing, then you again have a rapidly growing 
> routing table.
> 
> As we concluded many years ago: for addressing to scale, it 
> has to match the topology.  If addressing does not match the 
> topology, then additional information in the form of longer 
> prefixes must be advertised into the routing subsystem.  
> Ergo, if one chooses geographic address, one must force only 
> geographically based links.  Anything else destroys the 
> aggregatability of the address assignment.  Since we, as IETF 
> members, cannot decree where folks will connect, geo 
> addressing is a nice theorectical goal which is unimplementable.
> 
Only if you insist on the absolute minimum size routing table. As you
said above, economics drive the decisions of network managers. There is
a balance somewhere here between circuit costs for random interconnects,
and the cost of the routing table to support that. All we need to do is
provide a mechanism that allows for rational decisions about system cost
to be made. A mechanism that results in lower costs for those that
choose to multihome in a small geographic region will win out.

Tony