Apache Tomcat

Apache Tomcat is a servlet container developed by the Apache Software Foundation (ASF). Tomcat implements the Java Servlet and the JavaServer Pages (JSP) specifications from Sun Microsystems, and provides a "pure Java" HTTP web server environment for Java code to run.

Tomcat should not be confused with the Apache web server, which is a C implementation of an HTTP web server; these two web servers are not bundled together. Apache Tomcat includes tools for configuration and management, but can also be configured by editing XML configuration files.

Components

Catalina

Catalina is Tomcat's servlet container. Catalina implements Sun Microsystems' specifications for servlet and JavaServer Pages (JSP).

Coyote

Coyote is Tomcat's HTTP Connector component that supports the HTTP 1.1 protocol for the web server or application container. Coyote listens for incoming connections on a specific TCP port on the server and forwards the request to the Tomcat Engine to process the request and send back a response to the requesting client.

Jasper

Jasper is Tomcat's JSP Engine. Tomcat 5.x uses Jasper 2, which is an implementation of the Sun Microsystems's JavaServer Pages 2.0 specification. Jasper parses JSP files to compile them into Java code as servlets (that can be handled by Catalina). At runtime, Jasper is able to automatically detect JSP file changes and recompile them.

Jasper 2

From Jasper to Jasper 2, important features were added :

* JSP Tag library Pooling - Each tag markup in JSP file is handled by a tag handler class. Tag handler class objects can be pooled and reused in the whole JSP servlet.
* Background JSP compilation - While recompiling modified JSP Java code, the older version is still available for server requests. The older JSP servlet is deleted once the new JSP servlet has been recompiled.
* Recompile JSP when included page changes - Pages can be inserted and included into a JSP at compile time. The JSP will not only be automatically recompiled with JSP file changes but also with included page changes.
* JDT Java compiler - Jasper 2 can use the Eclipse JDT Java compiler instead of Ant and javac.

How to install Apache on Win-Vista

http://www.thesitewizard.com/apache/install-apache-on-vista.shtml

What is the difference between Forward Proxy and Reverse Proxy?

First let’s review what a forward proxy or proxy is and how it works. A forward proxy acts a gateway for a client’s browser, sending HTTP requests on the client’s behalf to the Internet. The proxy protects your inside network by hiding the actual client’s IP address and using its own instead. When an outside HTTP server receives the request, it sees the requestor’s address as originating from the proxy server, not
from the actual client.

A Reverse Proxy proxies on behalf of the backend HTTP server not on behalf the
outside client’s request, hence the term reverse. It is an application proxy for servers using the HTTP protocol. It acts as a gateway to an HTTP server or HTTP server farm by acting as the final IP address for requests from the outside. The firewall works tightly with the Reverse Proxy to help ensure that only the Reverse Proxy can access the HTTP servers hidden behind it. From the outside client’s point of view, the Reverse Proxy is the actual HTTP server.

What is Reverse Proxy???

A reverse proxy or surrogate is a proxy server that is installed within the neighborhood of one or more servers. Typically, reverse proxies are used in front of Web servers. All connections coming from the Internet addressed to one of the Web servers are routed through the proxy server, which may either deal with the request itself or pass the request wholly or partially to the main web servers.

There are several reasons for installing reverse proxy servers:

1. Security: the proxy server may provide an additional layer of defense by separating or masquerading the type of server that is behind the reverse proxy. This configuration may protect the servers further up the chain.

2. Encryption / SSL acceleration: when secure websites are created, the SSL encryption is sometimes not done by the Web server itself, but by a reverse proxy that is equipped with SSL acceleration hardware.

3. Load distribution: the reverse proxy can distribute the load to several servers, each server serving its own application area.

4. Caching: A reverse proxy can offload the Web servers by caching static content, such as images, as well as dynamic content, such as a HTML-page rendered by a content management system.

5. Compression: the proxy server can optimize and compress the content to speed up the load time.

TERMS USED:

PROXY SERVER: a proxy server is a server (a computer system or an application program) that acts as a go-between for requests from clients seeking resources from other servers. A client connects to the proxy server, requesting some service, such as a file, connection, web page, or other resource, available from a different server. The proxy server evaluates the request according to its filtering rules. For example, it may filter traffic by IP address or protocol. If the request is validated by the filter, the proxy provides the resource by connecting to the relevant server and requesting the service on behalf of the client. A proxy server may optionally alter the client's request or the server's response, and sometimes it may serve the request without contacting the specified server. In this case, it 'caches' responses from the remote server, and returns subsequent requests for the same content directly.

SSL ACCERLERATION: SSL acceleration is a method of offloading the processor-intensive public key encryption algorithms involved in SSL transactions to a hardware accelerator. Typically, this is a separate card that plugs into a PCI slot in a computer that contains one or more co-processors able to handle much of the SSL processing.

Read more :

http://www.sans.org/reading_room/whitepapers/webservers/a_reverse_proxy_is_a_proxy_by_any_other_name_302?show=302.php&cat=webservers