Re: Networks ignoring prepends?

[Alex Le Heux <alexlh () funk org>]

> On Jan 23, 2024, at 00:43, William Herrin <bill () herrin us> wrote:
>
> On Mon, Jan 22, 2024 at 3:34 PM Alex Le Heux <alexlh () funk org> wrote:
> > This is perfectly reasonable routing _if you're 3356_
> >
> > In this profit-driven world, expecting 3356 to do something that's unprofitable for them just because it happens to 
> > be convenient for you is, well, unreasonable.
>
> Every packet has two customers: the one sending it and the one
> receiving it. 3356 is providing a service to its customers. ALL of its
> customers. Not just 47787. Sending the packet an extra 5,000 miles
> harms every one of 3356's customers -except for- 47787.
>
> In this case, I am the customer on both ends. 3356's choice to route
> my packet via 47787 serves me poorly.

Packets don't have customers, ISPs do. And in this case you're not a customer of the ISP making the routing decision 
and 3356 is doing precisely what its customer tells it to do by adding (or not adding) specific communities to what is 
announced. In other words, 3356 is doing precisely what its customer pays it to do.

You can build a shorter backup path, deaggregate, get 53356 and 47787 to propagate your routes differently or change 
your transit mix. There aren't many other options. 

Fact is that all prepending does it provide a vague hint to other networks about what you would like them to do. And 
this is only one of the many things those networks take into account when formulating their routing policies. This is 
why many ASes build extensive community lists to set things like localpref and limit route propagation in other ways. 
Perhaps you can try adding 53356:47787 to your announcement although it's anyone's guess how that'll affect things.

Alex