Re: [v6ops] [GROW] Deaggregation data (was: Deaggregation by large organizations)

[Iljitsch van Beijnum <[e-mail]>]

On 17 Oct 2014, at 11:11, Marc Binderberger <[e-mail]> wrote:

>> If all German cities inject a 
>> more specific, do you really need to hear those in Tokyo or Seattle? Just 
>> send the traffic to Europe as per the aggregate and let them figure it out 
>> there.

> ... it's likely that for an US ISP X, peering with European ISPs Y and Z who 
> carry the various deaggregate plus aggregate from Germany, all the European 
> prefixes have this peering router as next hop (let's say we have 
> next-hop-self).

> What about BGP on this peering router doing some auto-aggregation in such a 
> case?  Has this been discussed?  It would avoid geographic communities and 
> would simply follow the BGP topology: if the deaggregates result in the same 
> forwarding information than the aggregate just keep the aggregate.

Yes, this would be another way to address the issue. However, this introduces a new complication: the presence of prefix Y in the table depends on the presence of prefix X. Currently, that's taboo in BGP.

Note that filtering according to geographic communities could be done within an AS, removing the need for inter-AS coordination (beyond propagating the communities). So for instance a network that spans the US could carry European more specifics on the east coast and Asian more specifics on the west coast, if they feel that having both sets of more specifics everywhere would inflate their routing tables too much.

> (2) the problem of ever-growing routing tables and de-aggregation is not new. 
> After so many years I'm wondering if the answer is that this cannot be solved 
> with BGP/routing alone

Look at the work in the IRTF routing research group. There are possibilities to address this, but so far there's always been significant resistance against the tradeoffs such solutions would require.

Iljitsch