The future of NAPs & IXPs

William B. Norton wbn at
Mon Apr 19 22:40:24 UTC 1999

At 11:18 AM 4/19/99 -0700, Vadim Antonov wrote:
>All is well but you missed one of the most critical issues with the current
>IXPs:  lack of scalability.  The private point-to-point interconnects
>are at least as fast as backbones.  Fixing IXP scalability issues requires
>somewhat radical departure from the current router architecture; such
>as being done by terabit router vendors.

In both the direct circuit interconnection model and the exchange based
interconnection model, point-to-point interconnection can be accomplished
with at least equal scalability.  Private cross connects (a piece of fiber)
within an exchange can be driven at the same speed as a piece of fiber that
travels across many miles under the ground.

(I think you inferred that there was a switch involved in the model...If
so, I agree, there are alternative ways to interconnect within an exchange
(i.e. switch vs. terabit routing technology, etc.) that each have different
characteristics and scalability issues. I'm comparing interconnection
environments apples to apples. )

----- snip -----

>(BTW, O(5) can be an arbitrarily large fixed number, simply speaking :)

OK - I'll restate; about, ~, roughly, and in the neighborhood of 5 ;-)

>William B. Norton <wbn at>  wrote:
>>For what it's worth...I just finished a paper that highlights the trade
>>offs between the direct circuit interconnect model and the exchange point
>>interconnection model for ISPs. The paper discusses the operations and
>financial models (taking into account the circuit costs, cost of exchange
>participation, cost of dark fiber, etc.) and the implications of these
>strategies across the # of interconnection participants and bandwidth
>utilization between the participants. 
>To cut to the chase, the major points from the paper:
>>1) For ISP interconnection, direct circuit interconnection is financially
>>attractive for low #s of connections (O(5)) of relatively low bandwidth
>>2) As the bandwidth and # of interconnections grow, the exchange point
>>interconnection model proves much more scalable for two reasons:  First, as
>>bandwidth grows between participants, ISPs are able to aggregate
>>interconnection traffic over increasingly large pipe back to their cloud,
>>yielding potentially significant economies of scale. The direct circuit
>>interconnection does not provide for this aggregation since the pipes are
>>destined to different plances.
William B. Norton	<wbn at>     +1 650.298.0400 x2225 
Equinix Director of Business Development

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