nanog mailing list archives
Re: "Tactical" /24 announcements
From: Amir Herzberg <amir.lists () gmail com>
Date: Thu, 12 Aug 2021 13:38:48 -0400
On Thu, Aug 12, 2021 at 1:22 PM William Herrin <bill () herrin us> wrote:
On Thu, Aug 12, 2021 at 9:41 AM Hank Nussbacher <hank () interall co il> wrote:On 12/08/2021 17:59, William Herrin wrote:If you prune the routes from the Routing Information Base instead, for any widely accepted size (i.e. /24 or shorter netmask) you break the Internet.How does this break the Internet? I would think it would just result in sub-optimal routing (provided there is a covering larger prefix) but everything should continue to work. Clue me in, please.A originates 10.0.0.0/16 to paid transit C B originates 10.0.1.0/24 also to paid transit C C offers both routes to D. D discards 10.0.1.0/24 from the RIB based on same-next-hop You peer with A and D. You receive only 10.0.0.0/16 since A doesn't originate 10.0.1.0/24 and D has discarded it. You send packets for 10.0.1.0/24 to A (the shortest path for 10.0.0.0/16), stealing A's paid transit to C to get to B.
Unless A filters C-bound packets purportedly from 10.0.1.0/24. B
doesn't currently transit for A so from B's perspective that's not an allowed path. In which case, your path to 10.0.1.0/24 is black holed.
Bill, I beg to respectfully differ, knowing that I'm just a researcher and working `for real' like you guys, so pls take no offence. I don't think A would be right to filter these packets to 10.0.1.0/24; A has announced 10.0.0.0/16 so should route to that (entire) prefix, or A is misleading its peers. If A doesn't, though, then B receives a packet from A to 10.0.1.0/24. Unless B is filtering based on the specific IP prefixes of A - which seems to me unlikely - then B has no way to know that this packet is from `you' rather than from A itself (or a customer of A). So B will carry this traffic, imho. So A is just paying for the traffic since it announced the prefix. Such situations, to best of my knowledge, actually happen on the Internet when a subprefix is filtered for different reasons. We observed it happens with ROV , in our ROV++ simulations, but I'll refrain from attaching the URL again so not to be `plugging' that paper (and since I'm lazy to look it up hhh) have great day and I'll be happy to learn if I'm wrong. Amir
Current thread:
- Re: "Tactical" /24 announcements, (continued)
- Re: "Tactical" /24 announcements Tom Hill (Aug 11)
- Re: "Tactical" /24 announcements Lukas Tribus (Aug 11)
- Re: "Tactical" /24 announcements Jon Lewis (Aug 11)
- Re: "Tactical" /24 announcements Tom Hill (Aug 12)
- Re: "Tactical" /24 announcements William Herrin (Aug 12)
- Re: "Tactical" /24 announcements Hank Nussbacher (Aug 12)
- Re: "Tactical" /24 announcements Amir Herzberg (Aug 12)
- Re: "Tactical" /24 announcements Mark Tinka (Aug 13)
- Re: "Tactical" /24 announcements William Herrin (Aug 12)
- Re: "Tactical" /24 announcements William Herrin (Aug 12)
- Re: "Tactical" /24 announcements Amir Herzberg (Aug 12)
- Re: "Tactical" /24 announcements William Herrin (Aug 12)
- Re: "Tactical" /24 announcements Baldur Norddahl (Aug 12)
- Re: "Tactical" /24 announcements Amir Herzberg (Aug 12)
- Re: "Tactical" /24 announcements Baldur Norddahl (Aug 13)
- Re: "Tactical" /24 announcements William Herrin (Aug 13)
- Re: "Tactical" /24 announcements Amir Herzberg (Aug 13)
- Re: "Tactical" /24 announcements Tom Beecher (Aug 13)
- Re: "Tactical" /24 announcements Amir Herzberg (Aug 13)
- Re: "Tactical" /24 announcements Masataka Ohta (Aug 14)
- Re: "Tactical" /24 announcements Tom Hill (Aug 11)
- Re: "Tactical" /24 announcements Baldur Norddahl (Aug 13)