Using NAT for best-exit routing

John Milburn jem at
Sat Aug 29 07:09:27 UTC 1998

"Brian Dickson" <briand at> writes:

>The idea is basically this: the web farm provider uses a NAT device
>(or configures NAT on a router) for every peering point with a given peer
>who wants best-exit. Separate address pools (in private address space)
>are used for each such NAT (and distinct such pool sets amongst multiple
>such peer networks). Ingress traffic to the web farm provider has it's
>*source* address NAT'd, and internal routing points return traffic to
>the *same* NAT through which the request traffic came.
>Thus, return (data) traffic is best-exit.

Using a transparant cache for ingress traffic has the same effect as
a NAT device, and scales with the number of concurrent flows.

A cache farm is more expensive to provision and deploy than a simple NAT,
but has the advantage of allowing for logging of source/destURL pairs,
which may be important to some content providers. Caching can also can
be a significant performance improvement in many cases, such as paths
with high latency*BW links or congested long haul circuits.

     John Milburn                           jem at
     Director - BoraNet                     jem at
     Cell +82 19-220-7035             Tel +82 2-220-7035
     Dacom Corporation, Seoul, Korea  Fax +82 2-220-0751

The reasonable man adapts himself to the world; the unreasonable one
persists in trying to adapt the world to himself.  Therefore all
progress depends on the unreasonable man.      -- George Bernard Shaw

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