-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA512 Hi all,
I'm reading v16 of this document. Section 5 - Best Practices. """ Use of local-preference inbound on preferred paths between service providers to help mitigate the adverse effects of prepending """ The statement right before this makes it clear that AS path prepending might not work if the neighbouring network is using i.e. Local Pref: """ The neighbor, to which prepending is used, may have an unconditional preference for customer routes and prepending doesn't work. It is helpful to check with neighbors to see if they will honor the prepend to avoid wasting effort and potentially causing further vulnerabilities. """ This is exactly why Local Pref shouldn't be used for TE (in my opinion). There are a bunch of problems with Local Pref and it should be avoided. I think that any best practice recommendations should come with justifications for why they make good practice. If Local Pref is going to be provided as a best practice recommendation, there needs to be a justification here. Otherwise this is a statement which hasn't been justified. Cheers, James. On Monday, July 7th, 2025 at 21:42, [email protected] <[email protected]> wrote: > > > Internet-Draft draft-ietf-grow-as-path-prepending-16.txt is now available. It > is a work item of the Global Routing Operations (GROW) WG of the IETF. > > Title: AS Path Prepending > Authors: Mike McBride > Doug Madory > Jeff Tantsura > Robert Raszuk > Hongwei Li > Jakob Heitz > Gyan Mishra > Name: draft-ietf-grow-as-path-prepending-16.txt > Pages: 13 > Dates: 2025-07-07 > > Abstract: > > Autonomous System (AS) path prepending is a tool to manipulate the > BGP AS_PATH attribute through prepending one or more Autonomous > System Numbers (ASNs). AS path prepending is used to deprioritize a > route in the presence of a route with a shorter AS_PATH. By > prepending a local ASN multiple times, ASes can make advertised AS > paths appear artificially longer. However, excessive AS path > prepending has caused routing issues in the Internet. This document > provides guidance for the use of AS path prepending, including > alternative solutions, in order to avoid negatively affecting the > Internet. > > The IETF datatracker status page for this Internet-Draft is: > https://datatracker.ietf.org/doc/draft-ietf-grow-as-path-prepending/ > > There is also an HTMLized version available at: > https://datatracker.ietf.org/doc/html/draft-ietf-grow-as-path-prepending-16 > > A diff from the previous version is available at: > https://author-tools.ietf.org/iddiff?url2=draft-ietf-grow-as-path-prepending-16 > > Internet-Drafts are also available by rsync at: > rsync.ietf.org::internet-drafts > > > _______________________________________________ > GROW mailing list -- [email protected] > To unsubscribe send an email to [email protected] -----BEGIN PGP SIGNATURE----- Version: ProtonMail wsG5BAEBCgBtBYJodhihCZCoEx+igX+A+0UUAAAAAAAcACBzYWx0QG5vdGF0 aW9ucy5vcGVucGdwanMub3JnsR9UKAORZltG3eHjbt5Tt9nLLY8kGJlbzH7d FD8UySAWIQQ+k2NZBObfK8Tl7sKoEx+igX+A+wAAlOYP/2WEMgwOfhT2ELOQ T2p9zF6qi9lm2kG/TAhOkYIaryCyk8C5qgN4ZV+50C9HpI8o7ZKRZ7rvTAQS uUkhT114/sRPrZ4JFiKUhGTX8egrAgUS4yU4pfxEYQlVsDeULD1rNr0zUJ6D h8HMu8wmqVYHqMJrZWzz2+wTZxDorc2J5rwEaNTqaOU2RQ5Aj1yETJccL18A SBQk3G24C4vQ/4l9Y/hHODNcul06Gsf1J0BeC0WxICZMPnPvrQ8n1ur8px56 laN1WqVOGMkaHOsBooE2AEQDTgy4XHHy7lJdoJW3BYOQqPK79p9NSLFkqDA7 TnY6Lf7FoIEebMx9YWzqeONf5U2qZmhR4ropu3tHtBnCYgEbQurtNfycp7z8 D70OYMUSL6JTny00QYeSGL0A1t/FkqVgkw0tnlTioNGkVU6sdjl+ot12n2rV tBsJldsjWpqGhY2vvObZGoLh7t8FadB2zfPU5nShUkFeKdL1ZjxIR9J+PCv/ iY4cGFg/dblDoegZqR2ve3KZ+DqwhP2bsftdtgk0KInJsAj6ddZHn+Rgvrxj 0X+1UK6am8X4XW7ScpKRQa/sPtWI9vOEmI8aw/1PDxxBzSlyLsbz7Dsv23IF ScZVMRpBXiaPcuxS9LeNfs1SWdTdA7PS0kweX9rqIJ+LQalOSANxj/of8hRF aKb0ATJv =6wjD -----END PGP SIGNATURE-----
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