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Transmission Control Protocol (TCP) Configurations
TCP configurations for a Citrix ADC appliance can be specified in an entity called a TCP profile, which is a collection of TCP settings. The TCP profile can then be associated with services or virtual servers that want to use these TCP configurations.
A default TCP profile can be configured to set the TCP configurations by default, globally to all services and virtual servers.
When a TCP parameter has different values for service, virtual server, and globally, the value of the most-specific entity (the service) is given the highest precedence. The Citrix ADC appliance also provides other approaches for configuring TCP. Read on for more information.
The Citrix ADC appliance supports the following TCP capabilities:
Defending TCP against spoofing attacks
The Citrix ADC implementation of window attenuation is RFC 4953 compliant.
Explicit Congestion Notification (ECN)
The appliance sends notification of the network congestion status to the sender of the data and takes corrective measures for data congestion or data corruption. The Citrix ADC implementation of ECN is RFC 3168 compliant.
Round trip time measurement (RTTM) using the timestamp option
For the TimeStamp option to work, at least one side of the connection (client or server) must support it. The Citrix ADC implementation of the TimeStamp option is RFC 1323 compliant.
Detection of spurious retransmissions
This can be done using TCP duplicate selective acknowledgment (D-SACK) and forward RTO-Recovery (F-RTO). If there are spurious retransmissions, the congestion control configurations are reverted to their original state. The Citrix ADC implementation of D-SACK is RFC 2883 compliant, and F-RTO is RFC 5682 compliant.
This functionality use New-Reno, BIC, CUBIC, Nile, and TCP Westwood algorithms.
The TCP receive window size increases beyond its maximum value of 65,535 bytes.
Points to consider before you configure window scaling
- You do not set a high value for the scale factor, because this can have adverse effects on the appliance and the network.
- You do not configure window scaling unless you clearly know why you want to change the window size.
- Both hosts in the TCP connection send a window scale option during connection establishment. If only one side of a connection sets this option, window scaling is not used for the connection.
- Each connection for the same session is an independent window scaling session. For example, when a client’s request and the server’s response flow through the appliance, it is possible to have window scaling between the client and the appliance without window scaling between the appliance and the server.
TCP maximum congestion window
The window size is a user configurable one. The default value is 8190 bytes.
Selective acknowledgment (SACK)
This uses the data receiver (either a Citrix ADC appliance or a client) notifies the sender about all the segments that have been received successfully.
Forward acknowledgment (FACK)
This functionality avoids TCP congestion by explicitly measuring the total number of data bytes outstanding in the network, and helping the sender (either a Citrix ADC or a client) control the amount of data injected into the network during retransmission timeouts.
TCP connection multiplexing
This functionality enables reuse of existing TCP connections. The Citrix ADC appliance stores established TCP connections to the reuse pool. Whenever a client request is received, the appliance checks for an available connection in the reuse pool and serves the new client if the connection is available. If it is unavailable, the appliance creates a connection for the client request and stores the connection to the reuse pool. Citrix ADC supports connection multiplexing for HTTP, SSL, and DataStream connection types.
Dynamic receive buffering
This allows the receive buffer to be adjusted dynamically based on memory and network conditions.
MPTCP connections between client and Citrix ADC. MPTCP connections are not supported between Citrix ADC and the back-end server. The Citrix ADC implementation of MPTCP is RFC 6824 compliant.
You can view MPTCP statistics such as active MPTCP connections and active subflow connections by using the command line interface.
At the command prompt, type one of the following commands to display a summary or detailed summary of MPTCP statistics, or to clear the statistics display:
Stat mptcp –detail
To establish an MPTCP connection, both the client and the Citrix ADC appliance must support the same MPTCP version. If you use the Citrix ADC appliance as an MPTCP gateway for your servers, the servers do not have to support MPTCP. When the client starts a new MPTCP connection, the appliance identifies the client’s MPTPC version from the
MP_CAPABALEoption in the SYN packet. If the client’s version is higher than the one supported on the appliance, the appliance indicates its highest version in the
MP_CAPABALEoption of the SYN-ACK packet. The client then falls back to a lower version and sends the version number in the
MP_CAPABALEoption of the ACK packet. If that version is supportable, the appliance continues the MPTCP connection. Otherwise, the appliance falls back to a regular TCP. The Citrix ADC appliance does not initiate subflows (MP_JOIN’s). The appliance expects the client to initiate subflows.
Extracting the TCP/IP path overlay option and inserting the client-IP HTTP header
Extracting TCP/IP path overlay and inserting client-IP HTTP header. Data transport through overlay networks often uses connection termination or Network Address Translation (NAT), in which the IP address of the source client is lost. To avoid this, the Citrix ADC appliance extracts the TCP/IP path overlay option and inserts the source client’s IP address into the HTTP header. With the IP address in the header, the web server can identify the source client that made the connection. The extracted data is valid for a lifetime of the TCP connection and therefore, this prevents the next hop host from having to interpret the option again. This option is applicable only for web services that have the client-IP insertion option enabled.
TCP segmentation offload
Offloads TCP segmentation to the NIC. If you set the option as “AUTOMATIC”, TCP segmentation is offloaded to the NIC, if NIC is supported.
Synchronizing cookie for TCP handshake with clients
This is used for resisting SYN flood attacks. You can enable or disable the
SYNCOOKIE mechanism for TCP handshake with clients. Disabling
SYNCOOKIE prevents SYN attack protection on the Citrix ADC appliance.
Learning MSS to enable MSS learning for all the virtual servers configured on the appliance
The following table provides a list of TCP parameters and its default value configured on a Citrix ADC appliance.
|TCP Delayed-ACK Timer||100 millisec||Timeout for TCP delayed ACK, in milliseconds.|
|TCP minimum Retransmission Timeout(RTO) in millisec||1000 millisec||Minimum retransmission timeout, in milliseconds, specified in 10-millisecond increments (value must yield a whole number if divided by 10)|
|Connection idle time before starting keep-alive probes||900 seconds||Silently drop TCP established connections on idle timeoutcp established connections on idle timeout|
|TCP Timestamp Option||DISABLED||The timestamp option allows for accurate RTT measurement. Enable or Disable TCP Timestamp option.|
|Multipath TCP session timeout||0 seconds||MPTCP session timeout in seconds. If this value is not set, idle. MPTCP sessions are flushed after the virtual server’s client idle timeout.|
|Silently Drop HalfClosed connections on idle timeout||0 seconds||Silently drop TCP half closed connections on idle timeout.|
|Silently Drop Established connections on idle timeout||DISABLED||Silently drop TCP established connections on idle timeout|
|TCP Buffer Size||131072 bytes||TCP buffer size is the receive buffer size on the Citrix ADC. This buffer size is advertised to clients and servers from Citrix ADC and it controls their ability to send data to Citrix ADC. The default buffer size is 8K and usually it is safe to increment this when talking to internal server farms. The buffer size is also impact by the actual application layer in Citrix ADC like for SSL endpoint cases it is set to 40 K and for Compression it is set to 96 K.|
|Note: The buffer size argument must be set for dynamic adjustments to take place.|
|TCP Send Buffer Size||8190 bytes||TCP Send Buffer Size|
|TCP Dynamic Receive Buffering||DISABLED||Enable or disable dynamic receive buffering. When enabled, it allows the receive buffer to be adjusted dynamically based on memory and network conditions. Note: The buffer size argument must be set for dynamic adjustments to take place|
|TCP Max congestion window(CWND)||524288 bytes||TCP Maximum Congestion Window|
|Window Scaling status||ENALBED||Enable or disable window scaling.|
|Window Scaling factor||8||Factor used to calculate the new window size. This argument is needed only when window scaling is enabled.|
|Keep-alive probes||DISABLED||Send periodic TCP keep-alive (KA) probes to check if peer is still up.|
|Connection idle time before starting keep-alive probes||900 seconds||Duration, in seconds, for the connection to be idle, before sending a keep-alive (KA) probe.|
|Keep-alive probe interval||75 seconds||Time interval, in seconds, before the next keep-alive (KA) probe, if the peer does not respond.|
|Maximum keep-alive probes to be missed before dropping connection.||3||Number of keep-alive (KA) probes to be sent when not acknowledged, before assuming the peer to be down.|
|RST window attenuation (spoof protection).||DISABLED||Enable or disable RST window attenuation to protect against spoofing. When enabled, will reply with corrective ACK when a sequence number is invalid.|
|Accept RST with last acknowledged sequence number.||ENABLED|
|Immediate ACK on PUSH packet||ENABLED||Send immediate positive acknowledgment (ACK) on receipt of TCP packets with PUSH flag.|
|Maximum packets per MSS||0||Maximum number of octets to allow in a TCP data segment|
|Nagle’s Algorithm||DISABLED||Nagle’s Algorithm fights with the problem of small packets in TCP transmission. Applications like Telnet and other real time engines which require every key stroke to be passed to the other side often create small packets. With Nagle’s algorithm Citrix ADC can buffer such small packets and sends them together to increase on the connection efficiency. This algorithm needs to work along with other TCP optimization techniques in the Citrix ADC.|
|Maximum TCP segments allowed in a burst||10 MSS||Maximum number of TCP segments allowed in a burst|
|Maximum out-of-order packets to queue||300||Maximum size of out-of-order packets queue. A value of 0 means no limit|
|Initial congestion window(cwnd) setting||4 MSS||Initial maximum upper limit on the number of TCP packets that can be outstanding on the TCP link to the server|
|TCP Explicit Congestion Notification(ECN)||DISABLED||Explicit Congestion Notification (ECN) provides end to end notification of network congestion without dropping packets.|
|TCP Max congestion window(CWND)||524288 bytes||TCP maintains a congestion window (CWND), limiting the total number of unacknowledged packets that may be in transit end-to-end. In TCP, the congestion window is one of the factors that determines the number of bytes that can be outstanding at any time. The congestion window is a means of stopping a link between the sender and the receiver from becoming overloaded with too much traffic. It is calculated by estimating how much congestion there is on the link.|
|TCP Hybrid Start (HYSTART)||8 bytes|
|TCP minimum Retransmission Timeout(RTO) in millisec||1000||Minimum retransmission timeout, in milliseconds, specified in 10-millisecond increments (value must yield a whole number if divided by 10).|
|TCP dupack threshold||DISABLED|
|Burst Rate Control||3||TCP Burst Rate Control DISABLED/FIXED/DYNAMIC. FIXED requires a TCP rate to be set|
|TCP Rate||DISABLED||TCP connection payload send rate in Kb/s|
|TCP Rate Maximum Queue||0||Maximum connection queue size in bytes, when BurstRateControl is used.|
|Multipath TCP||DISABLED||Multipath TCP (MPTCP) is a set of extensions to regular TCP to provide a Multipath TCP service, which enables a transport connection to operate across multiple paths simultaneously.|
|Multipath TCP drop data on pre-established subflow||DISABLED||Enable or disable silently dropping the data on Pre-Established subflow. When enabled, DSS data packets are dropped silently instead of dropping the connection when data is received on pre established subflow.|
|Multipath TCP fastopen||DISABLED||Enable or disable Multipath TCP fastopen. When enabled, DSS data packets are accepted before receiving the third ack of SYN handshake.|
|Multipath TCP session timeout||0 seconds||MPTCP session timeout in seconds. If this value is not set, idle MPTCP sessions are flushed after virtual server’s client idle timeout.|
|SYN spoof protection||DISABLED||Enable or disable drop of invalid SYN packets to protect against spoofing. When disabled, established connections are reset when a SYN packet is received.|
|TCP Syncookie||DISABLED||This is used for resisting SYN flood attacks. Enable or disable the SYNCOOKIE mechanism for TCP handshake with clients. Disabling SYNCOOKIE prevents SYN attack protection on the Citrix ADC appliance.|
|Loss Detection and Recovery|
|Duplicate Selective Acknowledgment (DSACK)||ENABLED||A Citrix ADC appliance uses Duplicate Selective Acknowledgment (DSACK) to determine if a retransmission was sent in error.|
|Forward RTO recovery (FRTO)||ENABLED||Detects spurious TCP retransmission timeouts. After retransmitting the first unacknowledged segment triggered by a timeout, the algorithm of the TCP sender monitors the incoming acknowledgments to determine whether the timeout was spurious. It then decides whether to send new segments or retransmit unacknowledged segments. The algorithm effectively helps to avoid additional unnecessary retransmissions and thereby improves TCP performance in the case of a spurious timeout.|
|TCP Forward Acknowledgment (FACK)||ENABLED||Enable or disable FACK (Forward ACK).|
|Selective Acknowledgement(SACK) status||ENABLED||TCP SACK addresses the problem of multiple packet loss which reduces the overall throughput capacity. With selective acknowledgment the receiver can inform the sender about all the segments which are received successfully, enabling the sender to only retransmit the segments which were lost. This technique helps Citrix ADC improve overall throughput and reduce the connection latency.|
|Maximum packets per retransmission||1||Allows Citrix ADC to control how many packets to be retransmitted in one attempt. When Citrix ADC receives a partial ACK and it has to do retransmission then this setting is considered. This does not impact the RTO based retransmissions.|
|TCP Delayed-ACK Timer||100 millisec||Timeout for TCP delayed ACK, in milliseconds|
|TCP Optimization mode||TRANSPARENT||TCP Optimization modes TRANSPARENT/ENDPOINT|
|Apply adaptive TCP optimizations||DISABLED||Apply Adaptive TCP optimizations|
|TCP Segmentation Offload||AUTOMATIC||Offload TCP segmentation to the NIC. If set to AUTOMATIC, TCP segmentation is offloaded to the NIC, if the NIC supports it.|
|ACK Aggregation||DISABLED||Enable or disable ACK Aggregation|
The Citrix ADC appliance allows you to specify values for TCP parameters that are applicable to all Citrix ADC services and virtual servers. This can be done using:
- Default TCP profile
- Global TCP command
- TCP buffering feature
The recvBuffSize parameter of the set ns tcpParam command is deprecated from release 9.2 onwards. In later releases, set the buffer size by using the bufferSize parameter of the set ns tcpProfile command. If you upgrade to a release where the recvBuffSize parameter is deprecated, the bufferSize parameter is set to its default value.
Default TCP profile
A TCP profile, named as
nstcp_default_profile, is used to specify TCP configurations that will used if no TCP configurations are provided at the service or virtual server level.
Not all TCP parameters can be configured through the default TCP profile. Some settings have to be performed by using the global TCP command. The default profile does not have to be explicitly bound to a service or virtual server.
To configure the default TCP profile
- Using the command line interface, at the command prompt enter:
set ns tcpProfile nstcp_default_profile … <!--NeedCopy-->
- On the GUI, navigate to System > Profiles, click TCP Profiles and update nstcp_default_profile.
Global TCP command
Another approach you can use to configure global TCP parameters is the global TCP command. In addition to some unique parameters, this command duplicates some parameters that can be set by using a TCP profile. Any update made to these duplicate parameters is reflected in the corresponding parameter in the default TCP profile.
For example, if the SACK parameter is updated using this approach, the value is reflected in the SACK parameter of the default TCP profile (nstcp_default_profile).
Citrix recommends that you use this approach only for TCP parameters that are not available in the default TCP profile.
To configure the global TCP command
Using the command line interface, at the command prompt enter:
set ns tcpParam …
On the GUI, navigate to System > Settings, click Change TCP parameters, and update the required TCP parameters.
TCP buffering feature
Citrix ADC provides a feature called TCP buffering that you can use to specify the TCP buffer size. The feature can be enabled globally or at service level.
Note. The buffer size can also be configured in the default TCP profile. If the buffer size has different values in the TCP buffering feature and the default TCP profile, the greater value is applied.
To configure the TCP buffering feature globally
At the command prompt enter:
enable ns mode TCPB
set ns tcpbufParam -size <positiveInteger> -memLimit <positiveInteger>
On the GUI, navigate to System > Settings, click Configure Modes, and select TCP Buffering.
And, navigate to System > Settings, click Change TCP parameters, and specify the values for Buffer size and Memory usage limit.
Setting Service or Virtual Server Specific TCP Parameters
Using TCP profiles, you can specify TCP parameters for services and virtual servers. You must define a TCP profile (or use a built-in TCP profile) and associate the profile with the appropriate service and virtual server.
You can also modify the TCP parameters of default profiles as per your requirements. You can specify the TCP buffer size at service level using the parameters specified by the TCP buffering feature.
To specify service or virtual server level TCP configurations by using the command line interface
At the command prompt, perform the following:
Configure the TCP profile.
set ns tcpProfile <profile-name>...
Bind the TCP profile to the service or virtual server.
set service <name> ....
> set service service1 -tcpProfileName profile1 <!--NeedCopy-->
To bind the TCP profile to the virtual server:
set lb vserver <name> .... <!--NeedCopy-->
> set lb vserver lbvserver1 -tcpProfileName profile1` <!--NeedCopy-->
To specify service or virtual server level TCP configurations by using the GUI
At the GUI, perform the following:
Configure the TCP profile.
Navigate to System > Profiles > TCP Profiles, and create the TCP profile.
Bind the TCP profile to the service or virtual server.
Navigate to Traffic Management > Load Balancing > Services/Virtual Servers, and create the TCP profile, which should be bound to the service or virtual server.
For convenience of configuration, the Citrix ADC provides some built-in TCP profiles. Review the built-in profiles listed below and select a profile and use it as it is or modify it to meet your requirements. You can bind these profiles to your required services or virtual servers.
|nstcp_default_profile||Represents the default global TCP settings on the appliance.|
|nstcp_default_tcp_lan||Useful for back-end server connections, where these servers reside on the same LAN as the appliance.|
|nstcp_default_WAN||useful for WAN deployments.|
|nstcp_default_tcp_lan_thin_stream||Similar to the nstcp_default_tcp_lan profile. However, the settings are tuned to small size packet flows.|
|nstcp_default_tcp_interactive_stream||Similar to the nstcp_default_tcp_lan profile. However, it has a reduced delayed ACK timer and ACK on PUSH packet settings.|
|nstcp_default_tcp_lfp||Useful for long fat pipe networks (WAN) on the client side. Long fat pipe networks have long delay, high bandwidth lines with minimal packet drops.|
|nstcp_default_tcp_lfp_thin_stream||Similar to the nstcp_default_tcp_lfp profile. However, the settings are tuned for small size packet flows.|
|nstcp_default_tcp_lnp||Useful for long narrow pipe networks (WAN) on the client side. Long narrow pipe networks have considerable packet loss occasionally.|
|nstcp_default_tcp_lnp_thin_stream||Similar to the nstcp_default_tcp_lnp profile. However, the settings are tuned for small size packet flows.|
|nstcp_internal_apps||Useful for internal applications on the appliance (for example, GSLB site syncing). This contains tuned window scaling and SACK options for the desired applications. This profile should not be bound to applications other than internal applications.|
|nstcp_default_Mobile_profile||Useful for mobile devices.|
|nstcp_default_XA_XD_profile||Useful for a XenApp or XenDesktop deployment.|
Sample command line interface examples for configuring the following:
Defending TCP against spoofing attacks
Enable the Citrix ADC to defend TCP against spoof attacks. By default the “rstWindowAttenuation” parameter is disabled. This parameter is enabled to protect the appliance against spoofing. If you enable, it replies with corrective acknowledgment (ACK) for an invalid sequence number. Possible values are Enabled, Disabled.
RST window attenuate parameter protects the appliance against spoofing. When enabled, will reply with corrective ACK when a sequence number is invalid.
set ns tcpProfile profile1 -rstWindowAttenuate ENABLED -spoofSynDrop ENABLED Done set lb vserver lbvserver1 -tcpProfileName profile1 Done <!--NeedCopy-->
Explicit Congestion Notification (ECN)
Enable ECN on the required TCP profile
set ns tcpProfile profile1 -ECN ENABLED Done set lb vserver lbvserver1 -tcpProfileName profile1 Done <!--NeedCopy-->
Selective Acknowledgment (SACK)
Enable SACK on the required TCP profile.
> set ns tcpProfile profile1 -SACK ENABLED Done > set lb vserver lbvserver1 -tcpProfileName profile1 Done <!--NeedCopy-->
Forward Acknowledgment (FACK)
Enable FACK on the required TCP profile.
set ns tcpProfile profile1 -FACK ENABLED Done set lb vserver lbvserver1 -tcpProfileName profile1 Done <!--NeedCopy-->
Window Scaling (WS)
Enable window scaling and set the window scaling factor on the required TCP profile.
set ns tcpProfile profile1 –WS ENABLED –WSVal 9 Done set lb vserver lbvserver1 -tcpProfileName profile1 Done <!--NeedCopy-->
Maximum Segment Size (MSS)
Update the MSS related configurations.
set ns tcpProfile profile1 –mss 1460 - maxPktPerMss 512 Done set lb vserver lbvserver1 -tcpProfileName profile1 Done <!--NeedCopy-->
Citrix ADC to learn the MSS of a virtual server
Enable the Citrix ADC to learn the VSS and update other related configurations.
set ns tcpParam -learnVsvrMSS ENABLED –mssLearnInterval 180 -mssLearnDelay 3600 Done <!--NeedCopy-->
Enable TCP keep-alive and update other related configurations.
> set ns tcpProfile profile1 –KA ENABLED –KaprobeUpdateLastactivity ENABLED -KAconnIdleTime 900 -KAmaxProbes 3 -KaprobeInterval 75 Done > set lb vserver lbvserver1 -tcpProfileName profile1 Done <!--NeedCopy-->
Buffer size - using TCP profile
Specify the buffer size.
> set ns tcpProfile profile1 –bufferSize 8190 Done > set lb vserver lbvserver1 -tcpProfileName profile1 Done <!--NeedCopy-->
Buffer size - using TCP buffering feature
Enable the TCP buffering feature (globally or for a service) and then specify the buffer size and the memory limit.
> enable ns feature TCPB Done > set ns tcpbufParam -size 64 -memLimit 64 Done <!--NeedCopy-->
Enable MPTCP and then set the optional MPTCP configurations.
> set ns tcpProfile profile1 -mptcp ENABLED Done > set ns tcpProfile profile1 -mptcpDropDataOnPreEstSF ENABLED -mptcpFastOpen ENABLED -mptcpSessionTimeout 7200 Done > set ns tcpparam -mptcpConCloseOnPassiveSF ENABLED -mptcpChecksum ENABLED -mptcpSFtimeout 0 -mptcpSFReplaceTimeout 10 -mptcpMaxSF 4 -mptcpMaxPendingSF 4 -mptcpPendingJoinThreshold 0 -mptcpRTOsToSwitchSF 2 -mptcpUseBackupOnDSS ENABLED Done <!--NeedCopy-->
Set the required TCP congestion control algorithm.
> set ns tcpProfile profile1 -flavor Westwood Done > set lb vserver lbvserver1 -tcpProfileName profile1 Done <!--NeedCopy-->
Dynamic receive buffering
Enable dynamic receive buffering on the required TCP profile.
> set ns tcpProfile profile1 -dynamicReceiveBuffering ENABLED Done > set lb vserver lbvserver1 -tcpProfileName profile1 Done <!--NeedCopy-->
Support for TCP Fast Open (TFO) in Multipath TCP (MPTCP)
A Citrix ADC appliance now supports TCP Fast Open (TFO) mechanism for establishing Multipath TCP (MPTCP) connections and speed up data transfers. The mechanism allows subflow data to be carried during the initial MPTCP connection handshake in SYN and SYN-ACK packets and also enables data to be consumed by the receiving node during the MPTCP connection establishment.
For more information, see TCP Fast Open topic.
Support for Variable TFO Cookie Size for MPTCP
A Citrix ADC appliance now enables you to configure a variable length TCP Fast Open (TFO) cookie of a minimum size of 4 bytes and a maximum size of 16 bytes in a TCP profile. By doing this, the appliance can respond with the configured TFO cookie size in the SYN-ACK packet to the client.
To configure TCP Fast Open (TFO) cookie in a TCP profile by using the command line interface
At the command prompt, type:
set tcpProfile nstcp_default_profile -tcpFastOpenCookieSize <positive_integer>
set tcpProfile nstcp_default_profile -tcpFastOpenCookieSize 8
To configure TCP Fast Open (TFO) cookie in a TCP profile by using GUI
- Navigate to Configuration > System > Profiles.
- In the details pane, go to TCP Profiles tab and select a TCP profile.
- In the Configure TCP Profile page, set the TCP Fast Open cookie size.
- Click OK and Done.
SYN-Cookie timeout interval
TCPSyncookie parameter is enabled by default in TCP profiles to provide robust (RFC 4987) based protection against SYN Attacks. If you need to accommodate custom TCP clients that are not compatible with this protection but still want to ensure a fallback in attack, the
synAttackDetection handles this for you by automatically activating the
SYNCookie behavior internally for time determined by the
To configure the maximum SYN ACK retransmission threshold by using the command line interface:
At the command prompt, type:
set ns tcpparam [-maxSynAckRetx <positive_integer>] set ns tcpparam [-maxSynAckRetx 150] <!--NeedCopy-->
To configure auto SYN cookie timeout interval by using the command line interface
At the command prompt, type:
set ns tcpparam [-autosyncookietimeout <positive_integer>] set ns tcpparam [-autosyncookietimeout <!--NeedCopy-->
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