William, Exactly! An example below is where operators/orgs do not have the funds for a full table router deployment and gather top talkers from sFlow, which says what routes are to be installed in TCAM, instead of hitting a default route. https://blog.sflow.com/2015/07/sdn-router-using-merchant-silicon-top.html https://blog.sflow.com/2015/10/active-route-manager.html https://blog.sflow.com/2016/07/internet-router-using-merchant-silicon.html Maybe instead of sFlow, it's FIB compression for switches that can only handle 512K IPv4 routes, or routers that are showing their age with 1M IPv4 route capacity. Ryan Hamel ________________________________ From: NANOG <nanog-bounces+ryan=rkhtech.org@nanog.org> on behalf of William Herrin <bill@herrin.us> Sent: Friday, December 6, 2024 9:01 AM To: Nick Hilliard <nick@foobar.org> Cc: nanog@nanog.org <nanog@nanog.org> Subject: Re: Route optimization using GPUs? Caution: This is an external email and may be malicious. Please take care when clicking links or opening attachments. On Fri, Dec 6, 2024 at 8:34 AM Nick Hilliard <nick@foobar.org> wrote:
BGP ensures loop-free interdomain path computation by inspecting the AS path of each NLRI. If a routing optimiser rewrites all the AS paths for all the NLRIs it receives, then it's just pooped all over the primary component of BGP that's designed to ensure that interdomain BGP actually works in the way that it's supposed to do in the first place, which also acts as an intrinsic safety guard against dfz hijacking.
As an industry, we should be well beyond the point of having to tell people that this is a poor idea,
Hi Nick, Have you ever filtered routes from the BGP table and replaced them with a default route? Perhaps the TCAM was too full and you weren't ready to upgrade yet? There's nothing inherently wrong with filtering BGP routes and replacing them in local routes of your own selection. Nor is there anything wrong with using a complicated and detailed local selection process. The error lies in allowing those local routes to accidentally escape your AS. Since people being people, they make mistakes, I thought a little standards work in the area might head off some of those escapes. Regards, Bill Herrin -- William Herrin bill@herrin.us https://nam12.safelinks.protection.outlook.com/?url=https%3A%2F%2Fbill.herrin.us%2F&data=05%7C02%7Cryan%40rkhtech.org%7C3cda590fc71545a0ec5808dd1617f0d6%7C81c24bb4f9ec4739ba4d25c42594d996%7C0%7C0%7C638691014279933365%7CUnknown%7CTWFpbGZsb3d8eyJFbXB0eU1hcGkiOnRydWUsIlYiOiIwLjAuMDAwMCIsIlAiOiJXaW4zMiIsIkFOIjoiTWFpbCIsIldUIjoyfQ%3D%3D%7C0%7C%7C%7C&sdata=Ti5JOFv4rHSeqA9KCG%2BXcwfp%2BqUQ1ujsiu6pd8TZ7bc%3D&reserved=0<https://bill.herrin.us/>