Re: [squid-users] Exchange ActiveSync HTTP 413

I still don't have my answer why it seemed to work internally but not
proxied. The extra debug in the 3.3 release (thanks Amos) was
certainly helpful, but not enlightening. Frankly, knowing what I now
know, I question the original test result. But getting a definitive
answer has become more of a scholastic exercise at this point, so I
can offer closure on the topic:

Exchange 2010 IIS sets a <requestLimit> maxRequestLength that is used
for /OWA and other virtual directories. Depending on where you look,
this could be anywhere from 30meg to "unlimited". Yet if RequestLength
is exceeded, a 403 is generated. But in the case of the /ActiveSync
virtual, the <serverRuntime> UploadReadAhead value seems to trump
this, and will generate a 413. UploadReadAhead is set to 48k by
default.

Increasing this value allowed successively larger EAS transactions to
occur. MS warns that changing this value is a potential DoS vector, so
they intentionally kept it low. While mobile users don't typically
*create* large messages that will hit this limit, it is not uncommon
to add to already-large discussions or forward a large attachment
originated by someone else, necessitating a bump.

--bill

On Aug 18, 2013, at 6:07 PM, Amos Jeffries <squid3_at_treenet.co.nz> wrote:

> On 19/08/2013 4:26 a.m., Bill Houle wrote:
>> Thanks Amos, perfectly targeted. Now I guess I'll be taking my troubles off the Squid list. The output clearly shows that it is IIS that is returning the 413. The HLB is not IIS, so obviously it is coming from the Exchange/CAS level. But if anyone can hazard a guess why the CAS might be inclined to behave when not proxied but reject under Squid, I'm all ears...
>
> Ar. Okay your Squid is too old to log the request headers being received and sent by Squid. Are you able to upgrade to the 3.3 RPM provided by Eliezer?
> http://wiki.squid-cache.org/KnowledgeBase/CentOS
>
> "debug_options 11,2" with that newer version will dump you out a full trace of the HTTP request and reply on both connections.
>
> Amos
>
Received on Thu Aug 22 2013 - 15:52:30 MDT