[176495] in North American Network Operators' Group
Re: Buying IP Bandwidth Across a Peering Exchange
daemon@ATHENA.MIT.EDU (Owen DeLong)
Tue Dec 2 18:43:10 2014
X-Original-To: nanog@nanog.org
From: Owen DeLong <owen@delong.com>
In-Reply-To: <C8827A15-A712-4D3A-A4BD-65E1C7B02F01@pch.net>
Date: Tue, 2 Dec 2014 15:42:08 -0800
To: Bill Woodcock <woody@pch.net>
Cc: NANOG <nanog@nanog.org>
Errors-To: nanog-bounces@nanog.org
> On Nov 25, 2014, at 10:56 AM, Bill Woodcock <woody@pch.net> wrote:
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> On Nov 25, 2014, at 10:47 AM, Colton Conor <colton.conor@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?
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> Some IXPs have a rule that explicitly disallows this, others encourage =
it, most don=92t care. I don=92t know of any that have a mechanism to =
enforce a rule prohibiting it.
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> PCH=92s 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_. =20
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>> 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?
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> Yes, it=92s 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=92re doing, and you don=92t mind looking a =
little out-of-step with best practices, and you don=92t mind it all =
being down at once, any time anything breaks, then it may be a =
reasonable economy. If you=92re planning on actually depending on it, =
you need to do better engineering, and either spend more money, or =
allocate your money more conservatively.
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> 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.
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> -Bill
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>=20
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I=92d say that depends=85
If it=92s 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
