Re: WCCP and Transparent Proxy Support in SquidNT

On Sat, 8 Jan 2005, Serassio Guido wrote:

>> I was wondering why this is the case. As far as I understand GRE is
>> supported under Windows Server OSes.
>
> Not exactly: Windows PPTP is based on GRE encapsulation, but there isn't any
> documented API about.

And in addition the WCCP GRE encapsulation is a bit odd. So using a
standard GRE implementation without modification won't work for WCCP.

WCCPv1 is sort of like plain IP GRE encapsulation without any options,
except that the payload protocol number is different. Why Cisco did this I
beats me, probably they just wanted to make it harder for other cache
vendors to interoperate with their routers as it requires a GRE
implementation aware of WCCPv1.

WCCPv2 is a GRE protocol of it's own with it's own header and options. In
normal HTTP Interception setups this whole header can be ignored (and is
what both ip_wccp and the GRE module in Linux does), but the GRE
implementation used on the cache server must know how to deal with it if
not it won't make any sense of the packets received.

Regards
Henrik
Received on Sat Jan 08 2005 - 15:34:52 MST