Understanding Virtual Servers in Citrix NetScaler
A vserver represents one or more applications in a server farm. The vserver is a named NetScaler entity that external clients can use to access applications hosted on the servers. It is represented by an alphanumeric name, virtual IP address(VIP), port, and protocol. The name of the vserver is only of local significanceand is designed to make the vserver easier to identify.
When a client attempts toaccess applications on a server, it sends a request to the VIP instead of the IPaddress of the physical server. When the NetScaler receives a request on the VIP,it terminates the connection at the vserver and uses its own connection with the server on behalf of the client. The port and protocol settings of the vserver determine the applications that the vserver represents.
For example, a Web server can be represented by a vserver and a service whose port and protocol are set to 80 and HTTP, respectively. Multiple vservers can use the same VIP but different protocols and ports.Vservers are points for delivering features. Most features, like compression,caching, and SSL offload, are normally enabled on a vserver. When the NetScaler receives a request on a VIP, it chooses the appropriate vserver by the port onwhich the request was received and its protocol. The NetScaler then processes therequest as appropriate for the features configured on the vserver. In most cases, vservers work in tandem with services. You can bind multiple services to a vserver. These services represent the applications running on physical servers in a server farm. After the NetScaler processes requests receivedon a VIP, it forwards them to the servers as determined by the load balancingalgorithm configured on the vserver.
Vservers can be grouped into the following categories:
â€¢ Load balancing vserver. Receives and redirects requests to an appropriateserver. Choice of the appropriate server is based on which of various loadbalancing methods the user configures.
â€¢ Cache redirection virtual server. Redirects client requests for dynamic content to origin servers and static content to cache servers. Cache redirection vservers often work in conjunction with load balancing vservers.
â€¢ Content switching virtual server. Directs traffic to a server on the basis ofthe content that the client has requested. For example, you can create acontent switching vserver that directs all client requests for images to aserver that serves images only. Content switching vservers often work inconjunction with load balancing vservers.
â€¢ Virtual private network (VPN) virtual server. Decrypts tunneled trafficand sends it to intranet applications.