Bucket assignment reversed by router in WCCP v2

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Bucket assignment reversed by router in WCCP v2

varadha tech
Hello,

I would like to know if any one has tried out running squid caches
as a cache cluster to leverage load balancing support in WCCPv2.

I am currently using a wccp daemon based on squid-2.5.STABLE10 - to
understand  the load balancing functionality - modified to send out
the Redirect_Assign by the lead cache that has the lowest IP. I see
that the router *always*
allocates buckets in the reverse order of the specified assignment;
for example, with two caches the lead cache specifies buckets 0-127 to
itself and 128-255 to the other; but the router assigns buckets 0-127
to the other cache and 128-255 to lead cache. Has any one experienced
this before?


(P.S:
Googling revealed another posting in the squid mail archives:
http://marc.info/?l=squid-users&m=97359430131458&w=2
which has the exact problem using WCCP v1.)

Routers that have this behavior:
Cisco 3600, IOS 12.3(1a); Cisco 2600  IOS 12.3(9a)
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Re: Bucket assignment reversed by router in WCCP v2

Adrian Chadd
On Fri, May 25, 2007, varadha tech wrote:

> Hello,
>
> I would like to know if any one has tried out running squid caches
> as a cache cluster to leverage load balancing support in WCCPv2.
>
> I am currently using a wccp daemon based on squid-2.5.STABLE10 - to
> understand  the load balancing functionality - modified to send out
> the Redirect_Assign by the lead cache that has the lowest IP. I see
> that the router *always*
> allocates buckets in the reverse order of the specified assignment;
> for example, with two caches the lead cache specifies buckets 0-127 to
> itself and 128-255 to the other; but the router assigns buckets 0-127
> to the other cache and 128-255 to lead cache. Has any one experienced
> this before?

Its entirely possible the spec (which Squid's WCCP1/2 implementations
implement the bare minimum of to function) and reality differ.
If you find it to be the case on more hardware then please, let us know,
and we'll sort out a commit to make things make sense.

(I've got kit here to test out WCCPv2 assignment stuff, I'm just
lacking time.)



adrian

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Re: Bucket assignment reversed by router in WCCP v2

Henrik Nordström
In reply to this post by varadha tech
fre 2007-05-25 klockan 17:28 -0400 skrev varadha tech:

> that the router *always*
> allocates buckets in the reverse order of the specified assignment;
> for example, with two caches the lead cache specifies buckets 0-127 to
> itself and 128-255 to the other; but the router assigns buckets 0-127
> to the other cache and 128-255 to lead cache. Has any one experienced
> this before?

Can you provide a packet capture showing the problem?

If the packet capture shows that the router assigns the buckets
differetly than ordered by the designated server then I'm afraid this is
an IOS bug, and you'll have to ask Cisco for an explanation.

Regards
Henrik

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