DigaReplicator / ReplicatorClient: Important security note - Potential network related issue

Situation: After updating Windows Server 2003 to Service Pack 2 it could happen that several servers like HP ProLiant DL380 G5 lose nearly 100 % of their network performance. Affected are embedded network interface adaptors like HP NC373i which are designed as ‘Multifunction adapter’. This problem was seen in complex switching environments based on Cisco switches and routers.

Symptom: In one case the network performance of DigaReplicator V was so bad that it was impossible transferring elements via WAN connections. The traffic of replication is quiet low and instable. Timeouts are possible which will lead to discontinued transfer. On the other hand Microsoft committed lots of different network related problems caused by this issue.

Source of problem: During setup of Service Pack 2 Microsoft installs a so called Scalable Network Package (SNP). SNP seems to be incompatible with several multifunction network components. SNP is a new feature which was not used in early versions of Windows Server 2003. The setup does not warn about the installation.

Detection: To detect the problem you should make a test of the transfer speed to any destination reachable through a WAN connection. Compare the result with tests made before setup of Service Pack 2. On the other hand you can establish a replication and watch the network performance and potential timeouts. Additional you should consider testing WAN performance with external network tools like Chariot. You will see an instable network performance instead of expected linear network speed.

Detecting affected hardware is mostly possible by opening the device manager and watching the properties of the network adaptors. The network adaptors should contain the phrase ‘Multifunction adaptor’. This is an indicator for the problem.

Solution: First of all you should check if there is any requirement having SNP installed in your network. We strongly recommend applying the patch provided by Microsoft which can be downloaded from this link: http://www.microsoft.com/downloads/details.aspx?FamilyId=062E954C-FDEC-45AF-A09C-5A05B8F010A5

The download points to a x86 (32 bit) installation of Windows Server 2003. There is also a patch for 64 bit systems but this is untested by DAVID Systems. See Microsoft’s Knowledge Base for further details about this topic: KB948496

In our tests applying the patch and restarting the server solved the problem immediately. There are additional steps recommended by Microsoft. Therefore we suggest applying all patches listed below:

1. Installation of KB948496 plus restarting the server
2. Editing the properties of any network interface card by open network configuration panel from the control panel, opening properties of a network card and changing to the advanced tab.
Disabling “Receive Side Scaling”
Disabling “TCP/IP Offload” if available
3. Repeating step 2 with all remaining network adaptors
4. Rebooting the server

Afterwards you should check the Windows Registry if all changes were applied:
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Tcpip\Parameters

- TCPChimney = 0
- EnableRSS = 0
- EnableTCPA = 0

Please note: This problem can also be solved by installing another network interface card. We tested Intel based desktop and server adaptor with PCIe interface before uninstalling SNP and they worked because the used technology is different to multi function adaptors.

Driver and Firmware compatibility for this patch: This patch was tested with current drivers and firmware provided by HP. In general updating the drivers and firmware cannot solve the problem because it is a Windows related problem. We recommend updating to current versions. During our tests we used the following versions:

- HP NC-Series Broadcom Online Fi

Customers also reported problems during a video replication which shown a good starting performance but suddenly stopped replication after a few seconds.

We found out that especially when working with video replication the following Registry keys must be set. A reboot is required after setting the values.

Please note that the TcpWindowSize depends on the bandwidth of the WAN connection and the round trip time. If you are starting your replication you should make extensive network performance tests.

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Tcpip\Parameters:

Tcp1323Opts (REG_DWORD) 0x00000003 (3)
TcpWindowSize (REG_DWORD) 0x0003FFFC (262140)
GlobalMaxTcpWindowSize (REG_DWORD) 0x0003FFFC (262140)

Also DigaReplicator AV has some optional parameters for supporting bigger TCP windows.

HKEY_LOCAL_MACHINE\SOFTWARE\DAVID\DigaReplicator\<ID>\Replicator:
AppLevelPacketSize (REG_DWORD) 0x0000FFFF (65535)
IPBufferSize (REG_DWORD) 0x0003FFFC (262140)
MaxIPBlockSize (REG_DWORD) 0x0000FFFF (65535)

Please shut down the DigaReplicator before adding these parameters. Afterwards DigaReplicator will use them. Newer versions of DigaReplicator AV will adjust the values afterwards automatically to a default value.

Customers who run a MUI version of Windows Server 2003 R2 need to download the native English version of the patch KB948496 even if they installed the German language packuage.