PMTUD and DF bit propagation for EDT over NetScaler Gateway
The NetScaler Gateway appliance supports Don’t Fragment (DF) bit enforcement for the EDT Path Maximum Transmission Unit Discovery (PMTUD). PMTUD helps in dynamically determining the maximum transmission unit (MTU) when establishing a session. From release 14.1 build 34.42 and later, the PMTU rediscovery mechanism identifies the loss of packets due to changes in path MTU of the established connection and initiates the PMTU rediscovery. The DF bit enforcement prevents EDT fragmentation that might result in performance degradation or failure to establish a session during PMTUD and PMTU rediscovery.
Starting from release 14.1 build 38.53, the DF bit persistence feature preserves the original DF bit value of packets throughout the entire session. The DF bit persistence feature offers the following benefits:
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Ensures correct communication: By preserving the sender's original DF bit setting, NetScaler Gateway prevents miscommunication or incorrect behavior that might result from intermediate devices changing the DF bit.
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Avoids unintended fragmentation: NetScaler Gateway prevents intermediate network devices from unintentionally fragmenting packets that the sender intended to not be fragmented, or vice versa.
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Respects sender's intent: NetScaler Gateway ensures the sender's intent (whether to allow fragmentation or not) is respected throughout the network path.
For more details, see Enlightened Data Transport.
Enable the PMTUD support in NetScaler Gateway
Using the CLI:
At the command prompt, type;
set ica parameter [-EnableSRonHAFailover ( YES | NO )] [-HDXInsightNonNSAP ( YES | NO )] [-EDTPmtudDF ( ENABLED | DISABLED )] [-EDTPmtudDFTimeout <positive_integer>] [-L7LatencyFrequency <positive_integer>]
Example:
set ica parameter -EnableSRonHAFailover YES -EDTPmtudDF ENABLED -EDTPmtudDFTimeout 100
Note:
From release 13.1 build 42.x and later, the EDTPmtudDF parameter is enabled by default. Previously, this option was disabled by default.
Using the GUI:
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Navigate to System > Settings > Change ICA® Parameters.
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In EDT PMTUD DF Enforce duration, enter the time-out in seconds for the PMTUD DF enforcement.
Note:
From release 13.1 build 42.x and later, the Enforce DF for EDT PMTUD option is enabled by default. Previously, this option was disabled by default.
Enable the PMTU rediscovery support in NetScaler Gateway
Using the CLI:
At the command prompt, type;
set ica parameter -EDTPmtudRediscovery ENABLED | DISABLED
This option is disabled by default.
Using the GUI:
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Navigate to System > Settings > Change ICA Parameters.
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Select the EDT PMTUD Rediscovery checkbox.
Enable the DF bit persistence support in NetScaler Gateway
Using the CLI:
At the command prompt, type;
set ica parameter -DFPersistence ENABLED | DISABLED
This option is disabled by default.
Using the GUI:
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Navigate to System > Settings > Change ICA Parameters.
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Select the DF Persistence checkbox.
