[c-nsp] WCCP performance problem on a 7600

[Charles Glass]

On Mon, Apr 14, 2008 at 11:40 AM, Mark Pace Balzan <mpb at melitacable.com> wrote:
>
>  >
>  > On Sat, Apr 12, 2008 at 2:53 PM, Dean Smith
>  > <dean at eatworms.org.uk> wrote:
>  > > I cant what Cache's you're using ?
>  >
>  > I am using Netcaches with version 6.0.3.
>  > >
>
>
>  Netcache have the most weried way of doing WCCP MASK - and its nowhere
>  near how it should be.
>  You actually have to enter many lines of config on the netcache CLI.
>  Ive had many discussions with netcache about this, and it's the only way
>  (im not saying the correct way) they do it.
>
The netcache method of configuring mask assignment using the CLI is
rather strange. In particular I found that configuring the same mask
value set on every cache to be somewhat counter intuitive.

Using 5 caches I was not able to configure more than 3 mask values per
cache without caches dropping out of the service group.

Using only 2 caches I was able to configure 18 mask values per cache.

I suspected an mtu issue due to the large datagrams used by WCCP.

I followed the guidlines in 'Choosing the optimum WCCP request
distribution method' to configure mask assignment. The link is
unfortunately only available to registered customers.

Interestingly the same document states that the limitation of 64 mask
values is due to the maximum datagram size that can be processed on
the Netcache being 4000 bytes.

Testing with Squid (2 caches) and mask assignment I was able to get 32
mask values per cache. The weight attribute did not appear to have any
effect on distribution of the mask values as it does with hash
assignment.

I would like to use mask assignment for obvious reasons but having
only 3 mask values per cache is not feasible.

Thanks for the info on this it is greatly appreciated.

>  Yes it is, and even more so when combined with spoofing on the cache,
>  since outbound would become quite a nightmare, causing many potential
>  redirect loops
>
>  Also the later SXF versions of IOS fixed many WCCP issues present in
>  older versions
>