Netscaler has the ability to use something called TCP profiles, which allows “non-TCP” experts to customize the Netscaler based upon what application is being used or what kind of network is be used or devices that are accessing the service.

TCP configurations for a NetScaler 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.

Now this might be the easiest performance tuning feature on the Netscaler.

The different profiles can be viewed under System –> Profiles –> TCP Profiles

Now by default when you create a service or virtual server it will automatically bind itself to the nstcp_default_profile so let’s take a look at it.

If we for instance setup a Netscaler Gateway solution for ICA access, we should use the nstcp_default_XA_XD_profile. Why you say? let’s take a look at it and compare the difference.

Not so much differences here. except a couple of things.

* Window Scaling * Nagle’s algorithm * Selective Ack (SACK) * Maximum Packets per MSS * Maximum Packts per Retransmission

Now all the differences here are within a key area. ICA is a “chatty” procotol, which might send out a lot of small packets. nstcp_xa_xd profile allows the Netscaler to send more packets inside a TCP segment. Window scaling and Selective Acknowledgement are also enabled for this profile for better experience over long pipes. Nagle’s algorithm increases the efficiency of a network application system by decreasing the number of packets that must be sent.

By choosing this profile for a NS gateway you gain a lower ICA RTT and less latency since packets will flow faster. And note you can attach a profile to a vServer by going into Advanced –> Profiles –> TCP profiles

Built-in TCP Profiles

For convenience of configuration, the NetScaler provides some built-in TCP profiles. For a list of built-in profiles, refer to Citrix Documentation - Built-in TCP Profiles.

For a list of options that are available for a TCP profile, refer to Citrix Documentation - ns tcpProfile. Note: These values can have serious impacts on network performance. Use these values carefully when adjusting them manually in existing profiles, or when creating new profiles.

Posted in msandbu