topological closeness....

Cacheing appears to be the only sane way to distribute
load. You always know where the closest cacheing server is.

not even this is the case - you can guess but that may not always

If I could _enforce_ caching by traffic interception then
I could construct vaguely logical cache structures as an ISP.

AS378 does exactly that. It blocks port 80 to abroad and forces everyone
to the Netscape proxy servers it runs (2 of them in a load balance fashion
with DNS set to point to only one if the other fails). AS378 is the
Israeli University academic network of 7 universities.

But relying on users to configure their end systems with the
identity of the closest cache server using some ill defined
"network metric" is always going to be an erratic affair at best.

Not unless you don't have a choice :slight_smile:

Go to:

There you will find their numbers for yesterday. Port 80 now consumes
54% of all traffic.