Re: wccp v2 witn TOS ACL

WCCP has nothing to do with ACLs. Squid 'supports' WCCP only in the
sense that it notifies the router of the caches existence. This
notification is wholly separate from all of the other functions of
Squid. In other words, WCCP is just like packet redirection at the OS
level (because it /is/ packet redirection at the OS level as far as
Squid is concerned).

Let me see if I can explain this more clearly:

When WCCP is enabled in Squid, an 'event' is added to the list of things
Squid does periodically. The event simply triggers a message exchange
between the router and Squid. The message exchange is sideband
communication--it does not happen via the normal HTTP traffic path, it
is a communication on port 2048 using a simple messaging protocol. The
event is just another housekeeping task that Squid does, like updating
counters, or doing a garbage collection crawl on the disk. It does not
impact the request path within Squid at all.

HTTP traffic from the router has a special type of GRE encapsulation,
but this is not handled by Squid. In fact Squid doesn't even see the
GRE packets. It is decapsulated at the OS level, and so what reaches
Squid looks just like the traffic that would come to Squid via
traditional OS level packet redirection. Squid doesn't deal with "WCCP"
web traffic.

Now...That's not to say you won't have problems with ToS when using WCCP
that you might not have otherwise. The router might treat requests
differently if you are sending them out of different IPs based on the
ToS mark (since the router only knows to automatically bypass WCCP
redirection for the caches in the WCCP cache pool--every other IP will
be redirected by default, leading to a loop). This could be worked
around. This is an issue to be dealt with at the router. Most WCCP
issues are, in fact.

Also worth noting is that WCCP v2 is no different than v1 as far as
Squid is concerned. Again, it is sideband communication that has no
impact on the HTTP request path. And as for version 1, the message
exchange is simply an event that is triggered periodically as a normal
housekeeping task...There is no new 'compatability' that v2 will
provide, and only a couple of very minor new features (none of the more
complicated features of WCCP v2 are yet supported by the Squid WCCP v2
patches). In other words, expect no magic. If you can't make it work
with v1, you won't make it work with v2.

BTW-Don't forget to turn off HTML email when sending to mailing lists.

Edward Millington wrote:
> Hi there!
>
> Do anyone know if wccp v2 will support TOS ACL?
>
> Thank you very much.

-- 
Joe Cooper <joe@swelltech.com>
Web caching appliances and support.
http://www.swelltech.com