503 due to content-length error? microwave issue?

Alan Dixon alan.g.dixon at gmail.com
Wed Nov 10 16:07:47 CET 2010

Theoretically perhaps, but:

1. Adding varnish triggered the problem.
2. Changing the MTU solved the problem.
3. The system administrators of the ISP had seen a similar
problem/solution in the past.

My limited understanding is that varnish's role in the problem was
just being more demanding ("standards sensitive"), whereas Apache was
able to handle the bad data better.

  - Alan

On Wed, Nov 10, 2010 at 10:00 AM, Caunter, Stefan <scaunter at topscms.com> wrote:
> Irrelevant. Varnish (or any front end proxy) knows nothing about layer
> 2, 3 or 4 in the network stack. It's an application, handling requests
> and responses at layer 7 using the HTTP protocol.
> Stefan Caunter :: Senior Systems Administrator :: TOPS
> e: scaunter at topscms.com  ::  m: (416) 561-4871
> www.thestar.com www.topscms.com
> -----Original Message-----
> From: varnish-misc-bounces at varnish-cache.org
> [mailto:varnish-misc-bounces at varnish-cache.org] On Behalf Of Alan Dixon
> Sent: November-10-10 9:56 AM
> To: varnish-misc at varnish-cache.org
> Subject: Re: 503 due to content-length error? microwave issue?
> Okay, here's the answer: the problem was solved by the user's ISP:
> they just lowered the MTU.
> Conclusion: adding varnish can create subtle network problems [not
> unique to varnish - also true of any front end proxy or ssl].
> Not varnish's fault or problem, but good to know, and would be even
> better if it were easier to debug.
>  - Alan

Alan Dixon, Web Developer

Drupal and CiviCRM for Canadian nonprofits.

More information about the varnish-misc mailing list