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North American Network Operators Group

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Re: The Great Exchange

  • From: Michael Shields
  • Date: Mon Jun 01 02:29:22 1998

> Neither ASNs nor network prefixes (particularly aggregated prefixes)
> correspond to geographical locales.  To evaluate cost of end-to-end
> transmission one has to collect information about state of the things
> along the path.  That information is typically totally unavailable
> to end-nodes and only partially available to backbones.

I understand your point.  However, I didn't claim that my analysis
method was based on a perfect understanding of the path each
individual packet took, which I agree is infeasible.  Instead, it
simply tries to determine the cost to deliver an average byte to
prefix P.

If for some reason traffic to prefix P took a different path under
conditions that might be correlated with a customer's usage patterns,
the cost might be higher or lower than the average.  An example of
this might be if there were an "overflow path" such that when line L1
was full, any additional packets were sent over line L2 instead; this
would be load-dependent and therefore in practice time-dependent, and
if a customer mostly sent data to P in the dead of night, their data
would never transit L2, and therefore would cost less to deliver; but
this cannot be accounted for in my model.

Current routing protocols don't work that way, since they will not
reroute traffic in the absence of a fault.  However L1 and L2 might be
not seperate lines balanced by a routing protocol but rather seperate
pricing models on a single line, for example flat-rate up to X usage
and then metered.  The cost allocation is probably not worth doing.

Having thought about it some more, I'd be willing to accept that this
problem is intractible for a network large enough to be considering
such a pricing model.
Shields, CrossLink.

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