[squid-users] Exchange ActiveSync HTTP 413

Greetings! We have a Squid 3.1.10 (installed via yum on 64b CentOS6) that
we are using as reverse proxy for Exchange. OWA, EWS, and RPC-over-HTTPS
seem to be operating without incident, but we have run into "request too
large" HTTP 413 errors with certain "large" ActiveSync POST messages from
mobile phones. iPhone and Android, equal opportunity.

To be correct, these large messages really aren't that large - we're
talking kilobytes not mega. But they generate a 413 error and stay stuck in
the phone's outbox. Other (smaller) messages sent after will sidestep the
blockage and are sent thru.

Our Exchange 2010 is dual Client Access Server DAG fronted by a hardware-
based network load balancer. Squid points to the HLB, the HLB to the DAG,
and ultimately to the active CAS. If we run the same tests internally (ie,
injecting the message at the HLB) everything goes thru fine. This would
seem to indicate that the source of the 413 is the proxy itself. But per
the squid config (below) we should be running at "unlimited" request size,
so I'm not sure why 413 would be thrown.

The log snippet below should show a sync transaction from an iPhone
followed by a failed "large" message send attempt. This is followed by a
successful send of a smaller message - so we know a POST works - and again,
a failed retry of the one that still remains queued.

I tried to correlate to cache.log running as "-k debug" but it is difficult
with all the traffic.

Any ideas?

--bill

visible_hostname mail.verance.com
via off
redirect_rewrites_host_header off
forwarded_for transparent
ignore_expect_100 on
ssl_unclean_shutdown on
request_body_max_size 0
#client_request_buffer_max_size 5 MB
maximum_object_size_in_memory 128 KB
cache_mem 32 MB

1376678951.412 1259 IP.IP.IP.IP TCP_MISS/000 0 POST
https://mail.verance.com/Microsoft-Server-ActiveSync? -
FIRST_UP_PARENT/EXCH-Mail -
1376678951.562 169 IP.IP.IP.IP TCP_MISS/200 446 POST
https://mail.verance.com/Microsoft-Server-ActiveSync? -
FIRST_UP_PARENT/EXCH-Mail application/vnd.ms-sync.wbxml
1376679016.869 940 IP.IP.IP.IP TCP_MISS/413 349 POST
https://mail.verance.com/Microsoft-Server-ActiveSync? -
FIRST_UP_PARENT/EXCH-Mail text/html
1376679037.864 806 IP.IP.IP.IP TCP_MISS/200 184 POST
https://mail.verance.com/Microsoft-Server-ActiveSync? -
FIRST_UP_PARENT/EXCH-Mail -
1376679038.409 84897 IP.IP.IP.IP TCP_MISS/000 0 POST
https://mail.verance.com/Microsoft-Server-ActiveSync? -
FIRST_UP_PARENT/EXCH-Mail -
1376679038.623 214 IP.IP.IP.IP TCP_MISS/200 497 POST
https://mail.verance.com/Microsoft-Server-ActiveSync? -
FIRST_UP_PARENT/EXCH-Mail application/vnd.ms-sync.wbxml
1376679039.514 766 IP.IP.IP.IP TCP_MISS/413 349 POST
https://mail.verance.com/Microsoft-Server-ActiveSync? -
FIRST_UP_PARENT/EXCH-Mail text/html
Received on Sat Aug 17 2013 - 18:06:17 MDT