Re: nested prefixes in Internet

[Owen DeLong <owen () delong com>]

> On Oct 10, 2016, at 14:59 , Baldur Norddahl <baldur.norddahl () gmail com> wrote:
>
>
>
> Den 10/10/2016 kl. 22.27 skrev Owen DeLong:
> > Not true… There are myriad reasons that the /24 might not reach a network peered with ISP-A, including the 
> > possibility of being a downstream customer of a network peered with or buying transit from ISP-A. In the latter 
> > case, not an issue, since it’s paid transit, but in the former (peered, not transit), again, ISP-A is probably not 
> > super excited to carry traffic that someone isn’t paying them to carry.
>
> But ISP-A is in fact being paid to carry the traffic. Supposedly ISP-B has a paid transit relation to ISP-A. In the 
> case the transit link is down ISP-A might have to transport the traffic through a less profitable link however.

Which isn’t really in the agreement between ISP-B and ISP-A unless it was specifically (and unusually) negotiated.

Also, you’re assuming that the leased space came with a transit agreement. In many cases, address leases don’t, so 
consider the additional scenario where ISP-B leases addresses from ISP-A, but has transit contracts with ISP-C and 
ISP-D but no connection at all to ISP-A.

> I know that if ISP-A was my network I would be making money even with the transit link down. Yes I might have to 
> transport something out of my network through one of my transits, but outbound traffic is in fact free for us because 
> we are heavy inbound loaded.

Yes, but it doesn’t help if it also came in on a transit link. Any traffic you both receive and transmit on transit 
costs you money pretty much no matter who you are.


Owen