Re: [renum] New Version Notification for draft-jiang-6renum-enterprise-01.txt

[Teco Boot <[e-mail]>]

>> Page 11:
>>>>      - Border filtering
>>>>      In a multihomed site, an egress router to ISP A could normally
>>>>      filter packets with source addresses from other ISPs. The egress
>>>>      router connecting to ISP A should be notified if the egress router
>>>>      connecting to ISP B initiates a renumbering event in order to
>>>>      properly update its filter function.
>> 
>> I don't get this. Isn't ingress filtering recommended? Do ISP A and B coordinate? IMHO an ISP should block packets with other ISPs PA addresses.
>> So the network has to forward packets with ISP_A source addresses to ISP_A, not ISP_B. And forward packets with ISP_B source addresses to ISP_B, not ISP_A.
>> 
> 
> I think the text you quote is confused; it is not the enterprise's egress
> routers that do the filtering, but the ISPs' ingress routers.
> 
> Then there's another discussion. A large enterprise running multiple PA prefixes
> would surely tell *all* its ISPs about those prefixes, and expect them to
> relax their ingress filters accordingly. A small enterprise probably couldn't
> do that, so needs two things:
> 
> 1. Address pair selection in the hosts that avoids this problem.
> 2. Egress router selection based on source address.
> 
> In any case the renumbering issue is how to inform all your ISPs of the
> new prefix to be allowed in their ingress filters, and the old prefix
> that is now to be blocked.

I don't see ISPs relax the PA ingress filters. I say routing shall better support multi-homing, it is needed for small enterprises (point 2 above). Large enterprises may have many PA prefixes, so needed there also.

RFC 3704 section 4.3 describes some options for directing packets to the correct ISP. It says "This is not a complicated procedure", but the approach looks clumsy to me. The problem should be tackled at the root, a fix in routing. Get this into gap-analysis document?

PS1: On solutions, not to mention BRDP-based routing: check draft-baker-fun-routing-class.
PS2: I understand it will take some time before this is fixed. But that is no excuse to postpone.

Teco.