Cisco Wireless LAN Controller Configuration Guide, Release 7.4
Configuring the TCP MSS
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Configuring the TCP MSS

Configuring the TCP MSS

Information About Configuring the TCP MSS

If the client’s maximum segment size (MSS) in a Transmission Control Protocol (TCP) three-way handshake is greater than the maximum transmission unit can handle, the client might experience reduced throughput and the fragmentation of packets. To avoid this problem in controller software release 6.0 or later releases, you can specify the MSS for all access points that are joined to the controller or for a specific access point.

When you enable this feature, the access point selects the MSS for TCP packets to and from wireless clients in its data path. If the MSS of these packets is greater than the value that you configured or greater than the default value for the CAPWAP tunnel, the access point changes the MSS to the new configured value.

TCP MSS is supported only on APs that are in local mode.

Configuring TCP MSS (GUI)


    Step 1   Choose WIRELESS > Access Points > Global Configuration to open the Global Configuration page.
    Step 2   Under TCP MSS, select the Global TCP Adjust MSS check box and set the MSS for all access points that are associated with the controller.
    Note    The valid range are:
    • For IPv4 TCP - between 536 and 1363 bytes.
    • For IPv6 TCP - between 1220 and 1331.

    MTU manually configured to 1363 (anything that does not apply to IPV6 ) will not be effective.


    Configuring TCP MSS (CLI)


      Step 1   Enable or disable the TCP MSS on a particular access point or on all access points by entering this command:

      config ap tcp-mss-adjust {enable | disable} {Cisco_AP | all} size

      where the size parameter is a value between 536 and 1363 bytes. The default value varies for different clients.

      Step 2   Save your changes by entering this command: save config
      Step 3   See the current TCP MSS setting for a particular access point or all access points by entering this command:

      show ap tcp-mss-adjust {Cisco_AP | all}

      Information similar to the following appears:

      
      AP Name              TCP State  MSS Size
      ------------------   --------   -------
      AP-1140 	 	 	 	    	 enabled   		 536
      AP-1240              disabled     	-
      AP-1130 			        	 disabled    	 -