[NANOG] Re: question about peering relationships

[Matthew Petach via NANOG <nanog () lists nanog org>]

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.
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