Re: your mail

[Iljitsch van Beijnum <iljitsch@muada.com>]

On Wed, 18 Jul 2001, Daniel Senie wrote:

> Sites multi-home for reasons other than line outage recovery, but you don't 
> take those into account. It is common for sites to select a second upstream 
> provider for multihoming based on a business need for reliable 
> communications to a specific destination (business partner, for example). 
> I'm not convinced a multi-homing solution based solely on the notion of 
> disaster recovery is sufficient.

Here in The Netherlands many fairly small ISPs only have one transit
connection, but they connect to the Amsterdam Internet Exchange because
that way they save a bundle on transit costs.

The "real" multihomed networks I've worked with multihome for disaster
recovery reasons, but since multihoming is expensive, they also want to
balance traffic over both connections.

Just an idea I just thought of: a large transit network could have a
backup-network that announces the same routes as the primary network and uses
tunnels to send traffic over the second ISP of multihomed networks. Under
normal circumstances the primary network collects all incoming traffic
(better routes) and the backup network does nothing. When the primary network
goes down, other ISPs send the traffic to the backup network and the backup
network tunnels it to the customers. As long as the primary and backup
networks don't suffer from (much) shared fate, this could be a very resilient
solution with no routing impact.

As long as we're talking about tunnels: we should fix the path MTU discovery
problems they expose.

Iljitsch