Q: What is the connection multiplexing feature of the NetScaler appliance?

A: The connection multiplexing feature is the core of the NetScaler appliance functionality. This feature required minimal configuration for use. It is one of the acceleration techniques available in the NetScaler appliance. Connection multiplexing is a method of reusing the connections and avoiding the overhead of establishing the TCP connections for the data transfer after the connection established is no longer in use.

Connection multiplexing has a positive impact on the performance of the server as well as the client-side, as explained in the following sections.

Impact on the Server-Side Performance

On the server-side, the NetScaler appliance helps in reducing the server setup and expenses. Additionally, the server-side leverages the fast TCOP options of the appliance designed to accelerate the communication among the well connected hosts. The NetScaler appliance ensures this by keeping the connections warm and suppressing the tear down messages. The NetScaler appliance forwards the tear down message to the client. However, to keep the connection open, the NetScaler appliance flips the two binary digit fields. Flipping the digits ensures that the client accepts the response as a valid one but does not understand that it is meant to tear down the connection. As a result, the connection remains open.

The server-side connections are not used to transfer data simultaneously but sequentially. This ensures that the connection available is reused. You can verify this by the difference between the number of connections on the client-side and the server-side of the NetScaler appliance.
When the connection multiplexing is performed on the server-side, the session is transparent to the client and they are not aware of any data manipulation.

Impact on the Client-Side Performance

On the client-side, the NetScaler appliance enables the clients to keep the connection open. It improves the performance between the client and the NetScaler appliance. This is achieved by translating and manipulating the client request. The request is terminated at the appliance and translated to the NetScaler IP address. Then the NetScaler appliance forwards the request to the existing TCP connection to the target server. The request from the clients are sequentially forwarded through a small number of persistent connections to the server.

You can use two modes of connectivity to accomplish connection multiplexing, Connection Proxy or Gateway.
Gateway mode has the complete traffic optimization and security features, such as IP address and port mapping, attack prevention, and content filtering. By default, the NetScaler appliance is configured in Gateway mode.

Q: How to disable connection multiplexing feature on the NetScaler appliance?

A: Refer to CTX124713 for information on disabling connection multiplexing feature.

Additional Resources

Citrix Documentation - Connection Multiplexing in NetScaler