Citrix Systems CITRIX NETSCALER 9.3 Configuring Selective Acknowledgment, SACK status, Enabled

Chapter 5 Advanced Configurations

To configure window scaling by using the configuration utility

1.In the navigation pane, expand System, and then click Settings.

2.In the details pane, under Settings, click Configure TCP Parameters.

3.In the Configure TCP Parameters dialog box, under TCP, select the Windows Scaling check box to enable window scaling.

4.In the Factor text box, type a windows scaling factor (for example, 6). For possible values, see “Parameters for configuring window scaling.”

5.Click OK.

A message appears in the status bar, stating that window scaling has been configured successfully.

Configuring Selective Acknowledgment

NetScaler appliances support Selective Acknowledgment (SACK), as defined in RFC 2018. Using SACK, the data receiver (either a NetScaler or a client) notifies the sender about all the segments that have been received successfully. As a result, the sender (either a NetScaler or a client) needs to retransmit only those segments that were lost during transmission. This improves the performance of data transmission. SACK is important in long fat networks (LFNs). By default, SACK is disabled.

To enable Selective Acknowledgment (SACK) by using the NetScaler command line

At the NetScaler command prompt, type the following commands to enable Selective Acknowledgment (SACK) and verify the configuration:

wset ns tcpParam [-SACK ( ENABLED DISABLED )]

wshow ns tcpParam

Example

>set ns tcpParam -SACK ENABLED Done

>show ns tcpParam

TCP Parameters
Window Scaling status	: ENABLED
Window Scaling factor	: 4
SACK status	: ENABLED
MaxBurst setting	: 6	MSS
Initial cwnd setting	: 4	MSS
TCP Receive Buffer	: 8190 bytes
TCP Delayed-ACK Timer	: 200 millisec

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