You use an SNA application that communicates with an IBM host system through a connection on a Microsoft Host Integration Server-based system.
This system is configured to use an IP-DLC link service.
In this scenario, you may experience random degradation in SNA application response times. The increases in application response times are also random.
This problem is most likely to occur when the Host Integration Server system and the IBM host system are connected by using a high speed network connection.
The IP-DLC link service uses an 8-KB socket receive buffer to receive User Datagram Protocol (UDP) data from the remote IBM systems that it is communicating with. If the IP-DLC link service receives a large amount of data in a very short interval, it is possible that some UDP data will be dropped by the IP-DLC link service. When this occurs, the IP-DLC link service will report that a gap was detected in the data stream. When the remote system is notified that a gap was detected, it resends the data that was not acknowledged by the IP-DLC link service. The retransmission of data can result in decrease in performance.
Service pack information for Host Integration Server 2006
To resolve this problem, obtain the latest service pack for Host Integration Server 2006. For more information, click the following article number to view the article in the Microsoft Knowledge Base:
979497 How to obtain the latest Host Integration Server 2006 service pack
A supported hotfix is available from Microsoft. However, this hotfix is intended to correct only the problem that is described in this article. Apply this hotfix only to systems that are experiencing the problem described in this article. This hotfix might receive additional testing. Therefore, if you are not severely affected by this problem, we recommend that you wait for the next software update that contains this hotfix.
If the hotfix is available for download, there is a "Hotfix download available" section at the top of this Knowledge Base article. If this section does not appear, contact Microsoft Customer Service and Support to obtain the hotfix.
Note If additional issues occur or if any troubleshooting is required, you might have to create a separate service request. The usual support costs will apply to additional support questions and issues that do not qualify for this specific hotfix. For a complete list of Microsoft Customer Service and Support telephone numbers or to create a separate service request, visit the following Microsoft Web site:
Note The "Hotfix download available" form displays the languages for which the hotfix is available. If you do not see your language, it is because a hotfix is not available for that language.
To apply this hotfix, you must have Host Integration Server 2004 Service Pack 1 (SP1) installed.
You do not have to restart the computer after you apply this hotfix.
Hotfix Replacement Information
This hotfix does not replace any other hotfixes.
The English version of this hotfix has the file attributes (or later) that are listed in the following table. The dates and times for these files are listed in coordinated universal time (UTC). When you view the file information, it is converted to local time. To find the difference between UTC and local time, use the Time Zone tab in the Date and Time tool in Control Panel. Microsoft Host Integration Server 2004 SP1
Microsoft Host Integration Server 2006 A hotfix is currently not available for Microsoft Host Integration Server 2006. Microsoft Host Integration Server 2009 A hotfix is currently not available for Microsoft Host Integration Server 2009
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section of this article.
After you apply this hotfix, the IP-DLC link service will use a default UDP socket receive buffer size of 32768 bytes (32 KB). You can change the UDP socket receive buffer by adding the following registry parameter:
Click Start, click Run, type regedit, and then click OK.
Right-click ExtraParameters, point to New, and then click DWORD Value.
Type SocketReceiveBufferSize, and then press ENTER.
Double-click SocketReceiveBufferSize, enter the size of the socket receive buffer in bytes, and then click OK. The minimum value that you can use is 8192 bytes (8 KB). If you enter a value for the socket receive buffer that is not a multiple of 8 KB, the value is rounded down to the nearest 8 KB multiple.
Note The Base value is originally set to Hexadecimal when you edit a DWORD. Therefore, you may want to change Base to Decimal before you add the value.
Exit Registry Editor.
The IP-DLC link service must be restarted before the change takes effect. The easiest way to do this is to restart the SNA Server service or the SnaBase service. Restarting these services will disconnect any users who are currently connected to the Host Integration Server.
For more information about Advanced Peer-to-Peer Networking (APPN), about High Performance Routing (HPR), and about RTP (Rapid Transport Protocol) connections in APPN/HPR networks, see Inside APPN and HPR - The Essential Guide to New SNA at the following IBM Web site:
Microsoft provides third-party contact information to help you find technical support. This contact information may change without notice. Microsoft does not guarantee the accuracy of this third-party contact information.
Note RTP connections and the Status Segment parameter of the RTP Transport Header are discussed in Chapter 8 of Inside APPN and HPR - The Essential Guide to New SNA. The RTP Status Segment is used to report gaps (missing data) in the data stream and is also used to acknowledge data.
For additional information, click the following article number to view the article in the Microsoft Knowledge Base:
824684 Description of the standard terminology that is used to describe Microsoft software updates
Microsoft Host Integration Server 2004 Enterprise Edition, Microsoft Host Integration Server 2004 Standard Edition, Microsoft Host Integration Server 2004 Service Pack 1, Microsoft Host Integration Server 2006 Enterprise Edition, Microsoft Host Integration Server 2006, Microsoft Host Integration Server 2009