If WDS multicast deployment is creeping VERY slowy, you probably have switches that are not able to fragment packets the way Microsoft expects.
To change WDS so it does not send fragmented packets do the following
Windows Server 2008R2
Set the following registry key and restart the WDSService
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\WDSServer\Providers\WDSMC\Protocol
Name: ApBlockSize
Value type: REG_DWORD
Value data: 1385 decimal
Windows Server 2008
Windows Server 2008 uses network profiles to control the setttings. Do the following to configure it to not send fragmented packets
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\WDSServer\Providers\WDSMC\Profiles\Custom
Name: ApBlockSize
Value type: REG_DWORD
Value data: 1385 decimal
If this allows the multicast transmission to complete you can then modify the TpCacheSize registry key below to increase the performance. If you decrease ApBlockSize without increasing TpCacheSize then overall performance will decrease. Basically ApBlockSize * TpCacheSize = the maximum bandwidth that can be achieved. Increase it from 1190.
Windows Server 2008 R2
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\WDSServer\Providers\WDSMC\Protocol
Name: TpCacheSize
Value type: REG_DWORD
Value data: 3145 decimal
Windows Server 2008
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\WDSServer\Providers\WDSMC\Profiles\Custom
Name: TpCacheSize
Value type: REG_DWORD
Value data: 3145 decimal
Restart the WDSServer service after setting this registry key. After setting this run a deployment to verify it completes and take note of the time to download the image. Then increase this value in increments until it fails or reaches 7550.
If you have to disable IP fragmentation to get multicast working then this may be indicative of low-end switching/routing hardware that perhaps does not support fragmentation efficiently or does not support multicast efficiently (IGMP/MLD snooping etc.). Multicast can be demanding on a network so it can expose problems or issues in network infrastructure that were unknown until multicast was setup.
References
http://support.microsoft.com/kb/2582106
To change WDS so it does not send fragmented packets do the following
Windows Server 2008R2
Set the following registry key and restart the WDSService
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\WDSServer\Providers\WDSMC\Protocol
Name: ApBlockSize
Value type: REG_DWORD
Value data: 1385 decimal
Windows Server 2008
Windows Server 2008 uses network profiles to control the setttings. Do the following to configure it to not send fragmented packets
- Click Start, Run, WdsMgmt.msc
- Right click the WDS server and choose properties
- Choose the network settings tab
- Change the network profile to custom
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\WDSServer\Providers\WDSMC\Profiles\Custom
Name: ApBlockSize
Value type: REG_DWORD
Value data: 1385 decimal
If this allows the multicast transmission to complete you can then modify the TpCacheSize registry key below to increase the performance. If you decrease ApBlockSize without increasing TpCacheSize then overall performance will decrease. Basically ApBlockSize * TpCacheSize = the maximum bandwidth that can be achieved. Increase it from 1190.
Windows Server 2008 R2
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\WDSServer\Providers\WDSMC\Protocol
Name: TpCacheSize
Value type: REG_DWORD
Value data: 3145 decimal
Windows Server 2008
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\WDSServer\Providers\WDSMC\Profiles\Custom
Name: TpCacheSize
Value type: REG_DWORD
Value data: 3145 decimal
Restart the WDSServer service after setting this registry key. After setting this run a deployment to verify it completes and take note of the time to download the image. Then increase this value in increments until it fails or reaches 7550.
If you have to disable IP fragmentation to get multicast working then this may be indicative of low-end switching/routing hardware that perhaps does not support fragmentation efficiently or does not support multicast efficiently (IGMP/MLD snooping etc.). Multicast can be demanding on a network so it can expose problems or issues in network infrastructure that were unknown until multicast was setup.
References
http://support.microsoft.com/kb/2582106
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