Client Keep-Alive :46:26 UTC Citrix Systems, Inc. All rights reserved. Terms of Use Trademarks Privacy Statement

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1 Client Keep-Alive :46:26 UTC 2015 Citrix Systems, Inc. All rights reserved. Terms of Use Trademarks Privacy Statement

2 Contents Client Keep-Alive... 3 Client Keep-Alive... 5 Configuring Client Keep-Alive... 7 Enabling or Disabling Client Keep-Alive Globally... 9 Enabling or Disabling Client Keep-Alive for a Service Configuring Connection Options with HTTP Profiles

3 Client Keep-Alive The Citrix NetScaler appliance provides features such as client keep-alive to improve the performance of a transaction management environment. Performance of any transaction management environment depends on factors such as bandwidth usage, download time, speed of the server and the client networks, and time consumed to complete a transaction. Client keep-alive improves performance by reducing the time consumed in a transaction. Two other settings that affect connection management include the maximum number of HTTP connections retained in the connection reuse pool and whether or not connection multiplexing is enabled. These variables are configured with HTTP profiles. Client keep-alive enables multiple client requests to be sent on a single client connection. This feature helps in a transaction management environment where the server closes the client connection after serving the response to the client. The client has to open a new connection for each request to the server leading to a lot of time being consumed for a transaction. The client keep-alive feature of the appliance alleviates this problem by keeping the client-side connection open between the client and the appliance even after the server closes the client connection. This allows multiple client requests to be sent using a single connection. Keeping the client-side connection open saves the packet round trips associated with opening and closing a connection. This is most beneficial to SSL sessions because this eliminates unnecessary termination and open sequences, thus reducing the time taken for a transaction to occur. Client keep-alive is useful under either of the following conditions: When the server does not support client keep-alive. When the server supports client keep-alive but an application on the server does not support client keep-alive. Client keep-alive can be applied to all HTTP services globally, or to a specific service, such as HTTP or SSL. Note that client keep-alive applies only to HTTP and HTTPS services. The following figure illustrates a typical client keep-alive deployment. 3

4 Client Keep-Alive Figure 1. Client Keep-Alive Entity Model As shown in the figure, to configure client keep-alive, you need to define services and enable client keep-alive for those services. Services represent applications on physical servers. The traffic from the client is intercepted by the configured service and the client request is directed to the origin server. The server sends the response and closes the connection between the server and the appliance. If a Connection: Close header is sent, this header is corrupted in the client-side response, and the client-side connection is kept open. As a result, the client does not have to open a new connection for the next request; instead, the connection to the server is reopened. Note: If a server sends back two Connection: Close headers, only one is edited. This results in significant delays on the client rendering of the object because a client does not assume that the object has been delivered completely until the connection is actually closed. 4

5 Configuring Client Keep-Alive To configure the client keep-alive feature, you need to create a service and enable client keep-alive for that service. The service you configure enables the NetScaler appliance to keep the client-side connection open even after the server has closed the connection between the server and the appliance. Note that while configuring a service, if the client keep-alive option is not explicitly specified, the service uses the global setting for the client keep-alive connection. For more information, see Enabling or Disabling Client Keep-Alive Globally. To create a service with client keep-alive enabled by using the NetScaler command line At the NetScaler command prompt, type: add service ( <name> <IPaddress> ) <servicetype> <port> -CKA (YES NO) Example add service Service-HTTP HTTP 80 -CKA YES Parameters for creating a service with client keep-alive enabled name The name of the service. The service name must not exceed 31 characters. IPaddress The IP address of the origin server, which the service represents. port 5

6 Client Keep-Alive The port on which the service listens. The port number must be a positive number not greater than The minimum value is 1. servicetype CKA The type of service that is being added. This parameter determines the behavior of the service. The possible values are: HTTP, FTP, TCP, UDP, SSL, SSL_BRIDGE, SSL_TCP, NNTP, ANY, SIP_UDP. The state of the client keep-alive feature for the service. Possible values: YES, NO. To create a service with client keep-alive enabled by using the configuration utility 1. In the navigation pane, expand Load Balancing, and then click Services. 2. In the details pane, click Add. 3. In the Create Service dialog box, specify values for the following parameters, which correspond to parameters described in Parameters for creating a service with client keep-alive enabled as shown: Service Name* name (Cannot be changed for an existing service) Server* IPaddress Port* port Protocol* servicetype Client Keep-Alive name (See Advanced tab and select the Override Global check box.) *A required parameter 4. Click Create, and then click Close. 6

7 Configuring Client Keep-Alive To configure the client keep-alive feature, you need to create a service and enable client keep-alive for that service. The service you configure enables the NetScaler appliance to keep the client-side connection open even after the server has closed the connection between the server and the appliance. Note that while configuring a service, if the client keep-alive option is not explicitly specified, the service uses the global setting for the client keep-alive connection. For more information, see Enabling or Disabling Client Keep-Alive Globally. To create a service with client keep-alive enabled by using the NetScaler command line At the NetScaler command prompt, type: add service ( <name> <IPaddress> ) <servicetype> <port> -CKA (YES NO) Example add service Service-HTTP HTTP 80 -CKA YES Parameters for creating a service with client keep-alive enabled name The name of the service. The service name must not exceed 31 characters. IPaddress The IP address of the origin server, which the service represents. port 7

8 Configuring Client Keep-Alive The port on which the service listens. The port number must be a positive number not greater than The minimum value is 1. servicetype CKA The type of service that is being added. This parameter determines the behavior of the service. The possible values are: HTTP, FTP, TCP, UDP, SSL, SSL_BRIDGE, SSL_TCP, NNTP, ANY, SIP_UDP. The state of the client keep-alive feature for the service. Possible values: YES, NO. To create a service with client keep-alive enabled by using the configuration utility 1. In the navigation pane, expand Load Balancing, and then click Services. 2. In the details pane, click Add. 3. In the Create Service dialog box, specify values for the following parameters, which correspond to parameters described in Parameters for creating a service with client keep-alive enabled as shown: Service Name* name (Cannot be changed for an existing service) Server* IPaddress Port* port Protocol* servicetype Client Keep-Alive name (See Advanced tab and select the Override Global check box.) *A required parameter 4. Click Create, and then click Close. 8

9 Enabling or Disabling Client Keep-Alive Globally The client keep-alive feature is disabled on the system by default. If you enable client keep-alive globally, all new services inherit the global settings by default. The following procedure describes the steps to enable or disable client keep-alive globally. To enable or disable the client keep-alive mode globally by using the NetScaler command line At the NetScaler command prompt, type one of the following commands: enable mode cka disable mode cka To enable or disable the client keep-alive mode globally by using the configuration utility 1. In the navigation pane, expand System, and then click Settings. 2. In the details pane, under Modes and Features, click Configure modes. 3. In the Configure Modes dialog box, select or clear the Client Keep-Alive check box. 4. Click OK. 9

10 Enabling or Disabling Client Keep-Alive for a Service You can enable or disable client keep-alive at the service level. Note that the service level settings take precedence over the global settings. The following procedure describes the steps to enable or disable client keep-alive at the service level. To enable or disable the client keep-alive mode for a service by using the NetScaler command line At the NetScaler command prompt, type: set service ( <name> <IPaddress> ) -CKA (YES NO) Example set service Service-HTTP-1 -CKA YES To enable or disable the client keep-alive mode for a service by using the configuration utility 1. In the navigation pane, expand Load Balancing, and then click Services. 2. In the details pane, click the service for which you want to enable or disable client keep-alive, and then click Open. 3. In the Configure Service dialog box, on the Advanced tab, under Settings, select or clear the Client Keep-Alive check box. 4. Click OK. 10

11 Configuring Connection Options with HTTP Profiles An HTTP profile is a collection of configuration settings that is used to control HTTP requests to and responses from virtual servers on a NetScaler appliance. You can use HTTP profiles to configure the maximum number of HTTP connections retained in the connection reuse pool. You can also use HTTP profiles to enable connection multiplexing if you are not sure that it is already enabled ( By default, connection multiplexing is enabled.), and to enable Persistence ETag. For more information about HTTP profiles, see Configuring HTTP Profiles. To configure the number of connections in the reuse pool by using the NetScaler command line At the NetScaler command prompt, type: set ns httpprofile <profilename> -maxreusepool <value> To configure the number of connections in the reuse pool by using the configuration utility 1. In the navigation pane, expand System, and then click Profiles. 2. In the details pane, on the HTTP Profiles tab, select the HTTP profile for which you want to configure the number of connections, and then click Open. 3. In the Configure HTTP Profiles dialog box, in Max connections in reusepool, specify the maximum number of connections you want to allow in connection reuse pool. 4. Click OK. To enable connection multiplexing by using the NetScaler command line At the NetScaler command prompt, type: set ns httpprofile <profilename> -conmultiplex ENABLED 11

12 Configuring Connection Options with HTTP Profiles To enable connection multiplexing by using the configuration utility 1. In the navigation pane, expand System, and then click Profiles. 2. In the details pane, on the HTTP Profiles tab, select the HTTP profile for which you want to enable connection multiplexing, and then click Open. 3. In the Configure HTTP Profiles dialog box, select the Connection Multiplexing check box. Note that this check box is enabled by default. 4. Click OK. 12