Re: Still not sure how this works...

gtoal@vt.com writes:

>> >Here's the situation I have: I want to be able to set up cacheing
>> >such that B clients always get their pages on link B except when
>> >link B is down, in which case they'll switch to link A.
>>
>> This is hard. How does cache B know link B is down?
>
>It doesn't, but it does know that it is getting timeouts when it requests
>pages from that link. And I'll rephrase that a little: "when link B is not
>supplying pages, for whatever reason"

How do you decide "when link B is not supplying pages?" If I make a request
for foo.com, and it travels across link B, and foo.com is down so I get
connection timeout, or connection refused, did *link B* not supply the page?

One thing to do, which would be pretty easy, is to configure Squid to
ICMP ping the far side of link B for every request. This is basically
what ICP does. It "ICP pings" the parent cache before every request.
If your parent cache is right at the other end of link B then you can,
with some confidence, interpret a missing ICP reply as a link B
failure, but it might also be congestion.

Duane W.
Received on Thu Apr 10 1997 - 21:47:39 MDT