Re: Networks ignoring prepends?

["Patrick W. Gilmore" <patrick () ianai net>]

> The Internet is lying to itself, and that’s not a situation that can persist forever.

I am not sure I agree.

First, prepends are a suggestion. Perhaps a request. It has never (or at least not for the 3 decades I’ve been doing 
this) been a guarantee. In the situation below, perhaps the 5K mile backup path is through a provider who pays 
Centurylink (Lumen?). Standard practice is to localpref your customers up, which makes prepends irrelevant. Why would 
anyone expect different behavior?

As for hiding hops, that is not lying. What happens inside my network is my business. If I give the world some info, 
say with in-addrs on hops, that’s fine. If I do not, I am not “lying”. This is perfectly sustainable, nothing will 
break (IMHO). In fact, I would argue without tools like MPLS, the Internet would have broken a long time ago.

-- 
TTFN,
patrick

> On Jan 22, 2024, at 08:13, Mel Beckman <mel () beckman org> wrote:
>
> Prepend contraction is becoming more common. You can’t really stop providers from doing it, and it reduces BGP table 
> size, which I’ve heard as a secondary rationale. I’d love to see the statistics on that though.
>
> BGP Communities seem to be the only alternative, and that limits your engineering reach to mostly immediate peers.
>
> Another problem is providers that hide multiple router hops inside MPLS, which appears as a single ip hop in 
> traceroutes, making it impossible to know the truth path geographically. 
>
> The Internet is lying to itself, and that’s not a situation that can persist forever.
>
> -mel via cell
>
> > On Jan 22, 2024, at 4:52 AM, William Herrin <bill () herrin us> wrote:
> >
> > Howdy,
> >
> > Does anyone have suggestions for dealing with networks who ignore my
> > BGP route prepends?
> >
> > I have a primary ingress with no prepends and then several distant
> > backups with multiple prepends of my own AS number. My intention, of
> > course, is that folks take the short path to me whenever it's
> > reachable.
> >
> > A few years ago, Comcast decided it would prefer the 5000 mile,
> > five-prepend loop to the short 10 mile path. I was able to cure that
> > with a community telling my ISP along that path to not advertise my
> > route to Comcast. Today it's Centurylink. Same story; they'd rather
> > send the packets 5000 miles to the other coast and back than 10 miles
> > across town. I know they have the correct route because when I
> > withdraw the distant ones entirely, they see and use it. But this time
> > it's not just one path; they prefer any other path except the one I
> > want them to use. And Centurylink is not a peer of those ISPs, so
> > there doesn't appear to be any community I can use to tell them not to
> > use the route.
> >
> > I hate to litter the table with a batch of more-specifics that only
> > originate from the short, preferred link but I'm at a loss as to what
> > else to do.
> >
> > Advice would be most welcome.
> >
> > Regards,
> > Bill Herrin
> >
> > --
> > William Herrin
> > bill () herrin us
> > https://bill.herrin.us/