I support this draft. Countering Nick's comments, the draft doesn't say AS path prepending is harmful; in fact, it's very clear that AS prepending, when used judiciously, can be a useful tool for the right situations. Meaning that 1, 2, or 3 AS prepends can be useful in some situations. But if that doesn't have the desired effect, adding even more AS prepends is unlikely to improve things; in fact, too many prepends create their own problems.
Given the prevalence of seemingly excessive numbers of AS prepends on the Internet, this guidance seems appropriate. On Wed, Apr 15, 2026 at 10:38 AM Nick Hilliard <[email protected]> wrote: > Hi Mike, authors, > > the root problem here remains prefix hijacking. I'm not convinced that > the IETF should publish an opinion about AS path prepending, as it's not > intrinsically harmful in itself, even if it can be an aggravating factor in > some situations. > > Nick > > Doug Madory wrote on 15/04/2026 03:58: > > Thanks for all of your work on this draft over the years, Mike. > > This effort was inspired by a talk I gave about excessive prepending at > NANOG almost six years ago; that's how I became one of the authors. > > That said, I'm not sure there is industry consensus on the specifics of > prepending to the point that it requires an RFC. If the other authors wish > to move forward without me, that is fine. I just worry about taking up the > volunteer staff's time wordsmithing a document of questionable value. > > > > > On Tue, Apr 14, 2026 at 10:01 PM Michael McBride < > [email protected]> wrote: > >> Hi all, >> >> In this update we included some, much appreciated, wglc comments from >> Randy Bush: >> >> Made clear that the steering applies only to inbound traffic. >> Expanded acronyms on first use. >> Clarified a couple sentences and Figure 1. >> Fixed spelling. >> >> mike >> >> >> >> -----Original Message----- >> From: [email protected] <[email protected]> >> Sent: Tuesday, April 14, 2026 6:51 PM >> To: [email protected] >> Cc: [email protected] >> Subject: [GROW] I-D Action: draft-ietf-grow-as-path-prepending-19.txt >> >> Internet-Draft draft-ietf-grow-as-path-prepending-19.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-19.txt >> Pages: 12 >> Dates: 2026-04-14 >> >> 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-19 >> >> A diff from the previous version is available at: >> >> https://author-tools.ietf.org/iddiff?url2=draft-ietf-grow-as-path-prepending-19 >> >> 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] >> >> _______________________________________________ >> GROW mailing list -- [email protected] >> To unsubscribe send an email to [email protected] >> > > > _______________________________________________ > GROW mailing list -- [email protected] > To unsubscribe send an email to [email protected] > > > _______________________________________________ > GROW mailing list -- [email protected] > To unsubscribe send an email to [email protected] > -- Thank you / Ho Pidamayado / Miigwech =============================================== David Farmer Email:[email protected] Networking & Telecommunication Services Office of Information Technology University of Minnesota 2829 University Ave SE Phone: 612-626-0815 Minneapolis, MN 55414 Cell: 612-812-9952 ===============================================
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