Re: [squid-users] How does WCCP work ?

From: Awie <>
Date: Sun, 18 Mar 2001 13:59:00 +0800


Many thanks (again) for your answer & explanation that makes me clearer.
Please find my lines <AW> in between.

Thx & rgds,


----- Original Message -----
From: "Joe Cooper" <>
To: "Awie" <>
Cc: <>
Sent: Sunday, March 18, 2001 12:38 PM
Subject: Re: [squid-users] How does WCCP work ?

> Ok...Let's see if the problem can be isolated:
> What is your IOS version?
> If a version that supports both v1 and v2 of WCCP, have you switched it
> to v1?

<AW> My IOS is version 12.0(7)T. It support both WCCPv1 and v2, however I
set it to v1 already.

> I know that you are able to load the ip_wccp module, because we've
> already discussed that. Have you set up a network dump, using a tool
> such as tcpdump or ethereal, between the router and the Squid box to see
> if the Squid is actually sending out HERE_I_AM messages?

<AW> Yes, I think I need (and I will use) a network analyzer to make sure
the traffic between Squid and router.

> To answer your questions:
> For a complete description of the protocol, here is the specification
> for v1:

<AW> I downloaded it ! Thanks....!

> Short version:
> The protocol is pretty simple. Squid sends a packet to the router:
> "HERE_I_AM" on the WCCP port (2048), which contains the IP of the
> sending cache. The router sends a packet back, with an ID: "I_SEE_YOU".
> When the cache replies: "HERE_I_AM" again, it confirms two way
> connectivity by including the ID from the previous "I_SEE_YOU".
> There is no "WCCP channel", just port 2048, but those packets are not
> encapsulated. So, even without the ip_wccp module loaded, I think you
> will still be able to 'connect' the cache and the router, and see
> HERE_I_AM and I_SEE_YOU packets going back and forth. Redirected
> requests, however, will not work until one of the GRE modules is loaded.
> If you are not seeing this communication, then either your Squid is
> sending the WCCP messages, the messages are not reaching the router, or
> the router is ignoring them. You need to do some form of packet dump to
> see if those messages are coming and going at all.

<AW> seemed that I mis-assumed about the port. It is clearer
for me about WCCP.

Just to make sure, I assume that WCCP is a protocol like HDLC, PPP, etc. I
need my Squid and router have same (match) WCCP protocol and setting (??) to
make them able to "handshake" and encapsulate / decaptulate the packet each
another. Am I right?

If yes, does it mean WCCP captulation adding "frame" (layer 2 or layer 3 ?)
to each HTTP packet that redirected to Squid?

> Awie wrote:
> > Folks,
> >
> > I am beginning frustrated because not able to make WCCP running at our
> > Squid system.
> >
> > My Squid is known by Cisco as CacheEngine. But redirection progress was
> > not happen. I did not see "Here_I_AM / I_See_You" signal in my router
> > although I am in debug and terminal mode.
> >
> > I followed all of FAQ instruction and suggestion from some of you
> > (thanks for Joe Cooper, Jan Haluza, etc), PLUS Cisco staff. However, my
> > WCCP is still not running.
> >
> > Hope someone would explain me how actually Squid communicate with router
> > through WCCP channel.
> >
> > Please advise.
> >
> > Thx & rgds,
> >
> > Awie
> --
> Joe Cooper <>
> Affordable Web Caching Proxy Appliances
Received on Sat Mar 17 2001 - 22:52:49 MST

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