FIX: An HTTP Protocol Violation Occurs When BizTalk Server Communicates with an HTTP 1.0 Server (320370)

SYMPTOMS

When you configure BizTalk Server to communicate to an HTTP 1.0 server, the BizTalk HTTP client does not honor the protocol requirements that are specified in the published HTTP RFCs with regard to persistent connections behavior.

Specifically, the BizTalk HTTP client attempts to reuse a connection even though the HTTP 1.0 server has not indicated that it supports this option by including the Connection: Keep-Alive header in its initial response.

If simultaneous POST requests are transmitted to the HTTP 1.0 Web server, to be in accordance with the HTTP RFCs, after the first request is processed, the Web server sets the FIN flag on the TCP/IP connection to request closure.

The BizTalk HTTP client does not correctly recognize that the connection should be considered closed and attempts to send another POST request on the same connection.

The semantics of BizTalk Messaging determine that requests may be placed in the Retry Queue and that the underlying TCP/IP transport protocol enter a TCP reset exchange that occurs between the BizTalk client and HTTP 1.0 Web server.

The following text is an example of the initial messages headers that are exchanged, which should determine that there are no persistent connections to be used:

BTS Client Request
POST /a/b/c HTTP/1.1
Host: nnn.nnn.nnn.nnn:pppp
Connection: Keep-Alive
Content-Length: nnn
Content-Type: text/plain; charset="utf-8" Accept: */*....

HTTP 1.0 Server Response
HTTP/1.0 200 OK
Content-Type: text/xml
Servlet-Engine: ...

In extreme situations, transmission of BizTalk messages may fail and result in messages being placed in the Suspended Queue.

RESOLUTION

Service Pack Information

To resolve this problem, obtain the latest service pack for Microsoft BizTalk Server 2002. For additional information, click the following article number to view the article in the Microsoft Knowledge Base:

815781 How to Obtain the Latest BizTalk Server 2002 Service Pack

Hotfix Information

A supported fix is now available from Microsoft, but it is only intended to correct the problem that is described in this article. Apply it only to computers that are experiencing this specific problem. This fix may receive additional testing. Therefore, if you are not severely affected by this problem, Microsoft recommends that you wait for the next that contains this hotfix.

To resolve this problem immediately, contact Microsoft Product Support Services to obtain the fix. For a complete list of Microsoft Product Support Services phone numbers and information about support costs, visit the following Microsoft Web site:

http://support.microsoft.com/contactus/?ws=support

NOTE: In special cases, charges that are ordinarily incurred for support calls may be canceled if a Microsoft Support Professional determines that a specific update will resolve your problem. The typical support costs will apply to additional support questions and issues that do not qualify for the specific update in question.

REFERENCES

The following text is from IETF RFC 2616:

Section 8.1.2.1:

Clients and servers SHOULD NOT assume that a persistent connection is maintained for HTTP versions less than 1.1 unless it is explicitly signaled.

Section 19.6:

And we would expect HTTP/1.1 clients to:
* recognize the format of the Status-Line for HTTP/1.0 and 1.1 responses;
* understand any valid response in the format of HTTP/0.9, 1.0, or 1.1.

For most implementations of HTTP/1.0, each connection is established by the client prior to the request and closed by the server after sending the response. Some implementations implement the Keep-Alive version of persistent connections described in section 19.7.1 of RFC 2068 [33].

In RFC 1945, Connection: Keep-Alive is a "common extension" to a 1.0 implementation. Closing the connection after the response is also the expected behavior in the absence of other signaling.