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

Joe,

I found a good information in the RFC draft of WCCPv1, below.

"If the router does not receive a valid WCCP_HERE_I_AM for 3 *
HERE_I_AM_T seconds it will no longer consider a web-cache to be
useable. In this case the web-cache is no longer advertised in the
WCCP_I_SEE_YOU packet and all buckets previously assigned to the
web-cache in the router's Redirection Hash Table are marked as
unassigned."

It means, if router did not get a valid WCCP_HERE_I_AM with in 30 seconds
(3 * 10 secs), router will "erase" the CacheEngine from it's bucket. And
there is no Cache Engine anymore (I only have 1 Squid box). In my case,
router kept the CacheEngine in it's bucket although it was more than 30
seconds.

So, I can assume that although I did not see "HERE_I_AM / I_SEE_YOU" packet
in my router console, a good communication between Router & Squid was
establish. Am I right?

Do you mean the tcpdump stuff that I can find at
ftp.ee.lbl.gov/tcpdump-3.4.tar.z ?

Thx & rgds,

Awie

----- Original Message -----
From: "Awie" <awie@eksadata.com>
To: "Joe Cooper" <joe@swelltech.com>
Cc: <squid-users@squid-cache.org>
Sent: Sunday, March 18, 2001 1:59 PM
Subject: Re: [squid-users] How does WCCP work ?

> Joe,
>
> Many thanks (again) for your answer & explanation that makes me clearer.
> Please find my lines <AW> in between.
>
> Thx & rgds,
>
> Awie
>
> ----- Original Message -----
> From: "Joe Cooper" <joe@swelltech.com>
> To: "Awie" <awie@eksadata.com>
> Cc: <squid-users@squid-cache.org>
> 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:
> >
> > http://www.wrec.org/Drafts/draft-ietf-wrec-web-pro-00.txt
>
> <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> O.....ow.....it 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 <joe@swelltech.com>
> > Affordable Web Caching Proxy Appliances
> > http://www.swelltech.com
> >
>
Received on Sun Mar 18 2001 - 05:15:28 MST