Symptoms
After you install Cumulative Update 1 (CU1) for Microsoft BizTalk Server 2013 R2, the Minimal Lower Layer Protocol (MLLP) adapter 2-way send ports do not suspend if they time out while waiting on the downstream system to return an acknowledgement. Instead, the send port instance completes without publishing back any response message.
Orchestration instances waiting for a response message or an exception will remain dehydrated. Even if Order Delivery is turned on, the send port may continue to send subsequent messages instead of queuing all messages while waiting for the ACK.
This issue occurs when one of the standard set of ACK codes is selected from the Acceptable ACK Codes property.
Additionally, you may receive the following error message:
MLLP Send adapter timed out while receiving the ACK.
Cause
This issue occurs after CU1 for BizTalk Server 2013 R2 is installed. CU1 adds support for handling custom ACK codes, and it unintentionally changes the behavior for handling standard ACK codes if a timely ACK is not received from the downstream system.
Resolution
Cumulative update information
For BizTalk Server 2013 R2
The fix that resolves this issue is included in Cumulative Update 5 for BizTalk Server 2013 R2.
Note The fix restores the correct behavior for standard ACK codes to be consistent with the release version of BizTalk Server 2013 R2.
Workaround
To work around this issue, select CUSTOM and then type the ACK codes in the textbox. For example, type AA, CA, AE, CE instead of selecting AA, CA, AE and CE from the dropdown menu.
Status
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.
References
Learn about service pack and cumulative update list for BizTalk Server.
Learn about BizTalk Server hotfixes and cumulative update support.
