XCON: Message Size Grows When Re-routing on Same Server

• Microsoft Exchange Japanese Server, versions 4.0, 5.0

SYMPTOMS

If there exist two or more possible routes between two Microsoft Exchange Server computers, and one of those servers goes down, messages will attempt to reroute between all the possible connections until their hop count is exceeded.

It is possible that before the hop count is exceeded, the server with the rerouting message may run out of disk space. This is caused by the successive rerouting process, which causes the header of the routed messages to grow in size.

When the disk space becomes low, the Exchange Administrator may see the following errors generated in the Windows NT Application log:

   Event ID: 9411
   Source:   MSExchangeMTA
   Type:     Error
   Category: Field Engineering
   Description:
   The MTA is terminating because the disk where MTADATA is located has
   less than 10 MB of space, or an error occurred while trying to check for
   free space on the disk. If disk space is low, free up some disk space
   and restart the MTA. NT Error code returned: 0(non-zero indicates an
   error while checking for free space)[BASE IL TIMER 3](16)

   Event ID: 9406
   Source: MSExchangeMTA
   Category: Resource
   There is not enough Performance Monitor memory to display the MTA
   Connections information. Stop attached Performance Monitors and
   re-start the MTA. [BASE TIMER 3] (14)

STATUS

Microsoft has confirmed this to be a problem in Microsoft Exchange Server versions 4.0 and 5.0. This problem has been corrected in Microsoft Exchange Server version 5.5.

MORE INFORMATION

If two Exchange Server computers are connected with two or more connections and one of those servers goes down, messages (addressed to the server that is down) on the server that is up will cycle through all possible routes between them.

A problem exists in Exchange versions 4.0 and 5.0 when, as the message passes through each turn at a connector, the P1 header grows in size to reflect the turn. This header, over time, can become quite large at the hop count for each connector is 512. So if there are two connectors between the two servers, the P1 header information will grow in size about 1,024 times.

This additional information is not needed for reroutes on a single server, So, in Exchange Server version 5.5, the additional header information is not added, and the message size remains the same.

Note that reroutes that span separate Exchange Server computers cause the P1 header to grow, because this is required when hopping between separate message transfer agents (MTAs).