Re: WCCP - cache only , no proxy

At 01:06 20/04/00, fooler wrote:
>if i understand you correctly what you mean here, to avoid ip
>fragmentation in a
>transparent environment, im using a cisco switch using _store_and_forward_ in
>switching mode to solve this problem.

it is less of an issue on (say) a L2 ethernet switch, given there's no
reason to fragment at layer-2.
(when did you last use an ethernet switch that forced you to a MTU of 576
bytes? :-) )

the issue is more one of (say) dial-up users whose IP stacks have set a MTU
of 576 on a dial connection.

the absolute 'recommended' configuration would be to run WCCP on that
access-edge.

ie.
  a typical PoP would look something like this:

                     ...............
                     : core router :
                     :.............:
                            | (switched {fast}ethernet)
       -------------------------------------------------------
            | (fastethernet) | |
  .................... ................. ....................
  :dial access-server: :DSL aggregation: ... :cable/wireless agg:
  :..................: :...............: :..................:
   | (ppp) | | | (atm) | | | (ppp) | |
   | | | | | | | | |
  dial dial isdn DSL DSL DSL HFC wireless
  user user user user user user user users

our recommendation would be to _always_ run WCCP on the access-servers
themselves (dial, DSL, cable, leased-line, ...) -- and thus any
'fragmentation' is limited to the per-hop link between the customer and the
interception/redirection point.

any potential IP fragmentation issues will be taken care of automatically,
since TCP MSS negotiation will be taking into account the path MTU.

of course, there is still the potential for problems if those end-users are
actually a network, and are using a lower MTU in their own network cloud,
but i'm yet to see a 'problem' case yet.

cheers,

lincoln.

--
   Lincoln Dale           Content Switching
   ltd@cisco.com          Cisco Systems Inc.        |         |
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