On Wed, Apr 9, 2025 at 12:03 PM William Herrin <bill@herrin.us> wrote:
On Wed, Apr 9, 2025 at 10:17 AM Matthew Petach <mpetach@netflight.com> wrote:
On Wed, Apr 9, 2025 at 8:31 AM William Herrin via NANOG < nanog@lists.nanog.org> wrote:
On Mon, Apr 7, 2025 at 8:10 AM Elmar K. Bins via NANOG <nanog@lists.nanog.org> wrote:
Yes, and it's very often a mess traffic-engineering wise...
Now, if one of the networks is playing local pref games, which they shouldn't be doing, then they may misroute packets the long way around the planet. But that's their fault for playing local pref games.
Bill--can you clarify why you feel setting localpref values for peers differently from customers is something ISPs "shouldn't be doing?"
Hi Matt,
Because, as Elmar alluded to, it makes a mess traffic engineering wise. Like the one where I ended up having to announce both a covering and disaggregates to overcome a provider of a provider localprefing my routes on a grand tour of the continental United States when they had a peeing route to me five miles down the road. https://mailman.nanog.org/pipermail/nanog/2024-January/224628.html
Is it your assertion that as an ISP, as a provider of services to my customers, I should leave it up to tie-breaking heuristics further and further down the BGP decision tree as to whether I can earn money by carrying traffic or not?
Not all hamburger joints are in the business of selling quality beef. Is yours?
I might posit that all hamburger joints should be in the business of deterministically selling hamburgers, at the very least. If I sell connectivity to a customer, the customer is likely to want some level of assurance that their traffic will indeed deterministically pass across that link, modulo any overriding traffic engineering they apply. I would be an unhappy customer if I discovered that my network provider believed that Heisenberg and Schrodinger were the patron saints of packet flows[0]; indeed, it's likely I would quickly find myself a new provider, where a bit more certainty about traffic patterns could be expected. Reiterating my question again, and this time hoping for a clearer answer than a muddy analogy to the quality of beef at a hamburger joint: Is it your assertion that ISPs should leave routing decisions purely to the default BGP path selection algorithm, with no hints, nudges, or fingers on the scale to steer traffic flows? Is "oldest path" really what we should let be the deciding factor in where traffic goes, all else being equal between paths learned from downstream customers and paths learned from peers? Meanwhile, all this talk of hamburger has made me hungry. I'm going to go make some lunch while I await your explanation of how you think ISPs should provide some determinism in their traffic flows. :) Thanks! Matt [0] it's highly uncertain where the traffic may go, and we won't know where it went until we go to look at it.