Buying IP Bandwidth Across a Peering Exchange

Bob Evans bob at
Tue Nov 25 21:03:16 UTC 2014

I agree with Bill...going it on the cheap is risky. DOn't consider it for
primary. It may be good for backup. I have sold small amounts of transit
to non-ISP companies on exchanges (100-200 meg). It's a good extra backup
for ISPs, if you setup your local pref, MED and then prepend your AS an
extra time or two to the prefixes you transmit. Then if you ever need to
use it, it's sitting there waiting to send and receive traffic. I let ISPs
customers do that with us for real low cost backup fees.
Bob Evans

> On Nov 25, 2014, at 10:47 AM, Colton Conor <colton.conor at> 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

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