> On Nov 25, 2014, at 10:56 AM, Bill Woodcock <wo...@pch.net> wrote: > > > On Nov 25, 2014, at 10:47 AM, Colton Conor <colton.co...@gmail.com> wrote: >> I know typically peering exchanges are made for peering traffic between >> providers, but can you buy IP transit from a provider on an exchange? An >> example, buy a 10G port on an exchange, peer 5Gbps of traffic with multiple >> providers on the exchange, and buy 5Gbps of IP transit from others on the >> exchange? > > Some IXPs have a rule that explicitly disallows this, others encourage it, > most don’t care. I don’t know of any that have a mechanism to enforce a rule > prohibiting it. > > PCH’s guidance in the IXP formation process is to avoid creating rules which > are, practically, unenforceable. So we generally counsel IXPs against having > a rule precluding transit across the switch fabric. That said, a > crossconnect is a _much better idea_. > >> Some might ask why not get a cross connect to the provider. It is cheaper >> to buy an port on the exchange (which includes the cross connect to the >> exchange) than buy multiple cross connects. Plus we are planning on getting >> a wave to the exchange, and not having any physical routers or switches at >> the datacenter where the exchange/wave terminates at. Is this possible? > > Yes, it’s possible, but what you describe is a pretty fragile setup. Lots of > common points of failure between peering and transit; places where screwing > one up would screw both up. If all of this is really tangential to whatever > you’re doing, and you don’t mind looking a little out-of-step with best > practices, and you don’t mind it all being down at once, any time anything > breaks, then it may be a reasonable economy. If you’re planning on actually > depending on it, you need to do better engineering, and either spend more > money, or allocate your money more conservatively. > > Doing everything the cheapest possible way, regardless of the fragility or > complexity, is very short-sighted, and is unlikely to be an economy in the > long run. > > -Bill > > > >
I’d say that depends… If it’s an equal cost choice, for example, between getting waves to multiple exchanges and peering with multiple providers at each exchange that way vs. putting a router at one exchange and getting cross-connects there, then I would argue that the former is actually more robust. Owen