What is proxy server

A proxy server seats between the client browser and the servers behind it, it intercepts the client request and then connects to the backend server using its own connection pool, forwards clients request to the server, gets response back from the back end server and then returns that response back to the client. A proxy server performs the same basic duties as a web server and in addition to that they perform following things

• Proxy: Accepts requrest from the client, forwards that request to backend, gets response back and forwards that response to client. In doing so it hides the actual back end server information from the client


• Content filtering: They are often used to filter access to internet. The proxy can be configured with rules to reject access to sites that contain objectionable material, preventing users from gaining access to those sites


• Caching: Proxy servers can cache the results of common user requests and next time they get request for that resource, they can server the response from cache instead of sending to the actual backend server


• Security: They terminate the user connection inside the DMZ, they hide server identities by providing thier own domain names in the URL instead of backend server name. Combined with authentication proxy such as TAM, proxies can authenticate the user before forwarding the request to backend

Application Server component

WebSphere Application Server relies on following server components to provide enterprise level environment

• Web Browser: The end user uses a Web browser to interact with the deployed applications. The administrator makes use of browser to access the WebSphere Application Server Administration Console



• IP Sprayer: IP sprayer is normally a hardware unit that seats in front of your web server and distributes user requests among different HTTP server. If you dont use IP sprayer instead point the application URL to HTTP Server then that server becomes single point of failure also if you have a big user load then you might want to distribute users requests among different HTTP server which in turn would distribute user requests to different WAS server. The IP sprayer can either randomly distribute requests between different HTTP Servers or they can be sophisticated things like if the user request particular application then forward that request to high performance/ powerful server



• Load balance: The end user of WAS, normally points to the load balance, which takes care of distributing the user requests between different HTTP servers. The load balancer makes sure that no individual server is overwhelemed with the requests while other servers are idel.



• HTTP Server and Web Server Plugin: THe HTTP server is used for two things first is to server static content and in addition to that it also makes use of WebSPhere Plugin to distribute requests among different servers where the application is configured (Usually different servers in cluster). The HTTP server is normally configured to use either weighted round robin scheduling algorith, where the first request is distributed to a random application server, which servers as a starting point and then the subsequent requests are distributed according to the assigned weights of the application server. You can also configure plugin to use random system in which case the server weightage is not taken into consideration and the requests are distributed randomly. The HTTP server also takes care of session affinity, which makes sure that the request from the client goes to same server which served last request for that client



• Firewall: A firewall is a hardware and software system that manages the flow of information between the Internet and your companies network. It takes care of things like blocking user access to only few predefined ports, it can block virus and denial of service attacks.



• Database server: Most of the enterprise applications use RDBMS for data storage and retrieval functionality. The Application developers decide what database to use, there structure,.. The WebSPhere application server does not store any configuration data in db, that data is stored in .xml files on the file system



• Websphere MQ: WebSPhere MQ is messaging backbone that is used for exchanging point-to-point message and publish-and-subscribe messaegs with applications that reside a WebSphere MQ network.