[squid-users] WCCP and Web Cache Packet Return

From: Bin Liu <binliu.lqbn_at_gmail.com>
Date: Fri, 7 Nov 2008 14:18:27 +0800


Just read the WCCPv2 document from
It seems that WCCPv2 support web caches tunneling back the packets
they do not service to the same router from where they are received.
Once a router has received a formerly redirected packet, it knows not
to redirect it again. Here is the details:

Web Cache Packet Return

WCCP v2 filters packets to determine which redirected packets have
been returned from the cache engine and which ones have not. It does
not redirect the ones that have been returned because the cache engine
has determined that the packets should not be cached. WCCP v2 returns
packets that the cache engine does not service to the same router from
which they were transmitted.

So can current version of squid support the following features:

1. Sending the packets squid can not service back to router via GRE
tunnel or Layer 2. There are many applications just "borrow" the port
80 and send their own formatted data, they are not HTTP requests at
all. Currently squid will only report a "clientTryParseRequest: FD 41
(x.x.x.x:xxxx) Invalid Request" error in cache_log when receiving
these packets.

2. Sending packets back according to the ACLs defined in squid.conf.
So when customers access some domains or URLs, the request packets can
be returned back and then go out directly. A bit like the
redirect-list defined on router, but we can't write domains or URLs in
router's access-list.

I've noticed that there are some keywords like "wccp2_return_method"
in squid configuration directives. Is this just to be compatible with
WCCPv2 communication protocol or can be fully functional?


Received on Fri Nov 07 2008 - 06:18:31 MST

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