What Is A Proxy Server
What Is A Proxy Server?
Proxy is a server that serves requests passing customer data forward. A user (client) connects to a proxy server, requesting some service, such as a file, connection, website or other resource available on another server.
A proxy server may optionally alter the client request or server response and sometimes can provide this feature without even connecting to the specified server. It can also act as a server that stores data in a form of cache in computer networks. They are installed on machines with connections typically greater than the clients and high power storage.
These servers have a variety of uses, such as content filtering, providing anonymity, among others.
An HTTP caching proxy, for example, allows the client requests a document on the World Wide Web and the proxy looks for the document in its cache. If found, the document is returned immediately. Otherwise, the proxy fetches the document on the remote server, delivers it to the client and saves a copy in its cache. This allows a reduction in latency, since the proxy server, not the original server is accessed, providing a further reduction in bandwidth usage.
Emergence
The proxy server from the need to connect a LAN to the Internet via a computer network that shares its connection with other machines. That is, if we consider that the local network is a network “internal” and the Internet is a network of “external” we can say that the proxy is that it allows other machines have external access.
Generally, internal network machines do not have valid addresses on the Internet and therefore have a direct connection to the Internet. Thus, every connection request from a machine on the LAN to an Internet host is routed to the proxy, this, in turn, makes contact with the desired host, forwarding the response to the request to the local network machine. For this reason, we use the proxy for this type of service, which is translated to an intermediary or proxy. It is common to have the proxy with direct connection to the Internet.
Web proxy
A popular application proxy is caching web proxy, web proxy used with a cache. This provides a cache of Web pages and files available on remote servers from the Internet, allowing customers to a local area network (LAN) access them more quickly and feasible.
When it receives a request to access a Web resource (specified by a URL), which uses a proxy cache search results for this URL into your local cache. If the resource is found, it is returned immediately. Otherwise, it loads the resource from the remote server, returning it to the requestor and stores a copy of this in your cache. The cache usually uses an expiry algorithm to remove documents according to their age, size and access history. Two simple algorithms are Least Recently Used (LRU) and Least Frequently Used (LFU). LRU removes the documents that have spent more time without being used, while LFU removes the least frequently used documents.
The proxy is also used to browse anonymously, or is made to replace a proxy for another in order to circumvent protections offered by the original proxy.
The privacy of public proxy servers has been questioned recently after an American teenager of thirteen years to discover, by examining the source code of a site, that a famous site for anonymous surfing, generated logs with actual data from your users and sent them to police the U.S.
Many people use the Proxy, as said before, to circumvent protection systems, ie, informally speaking, would like him to play the blame to another person by IP.
Transparency
A transparent proxy is a way to force users of a network to use the proxy. Besides features of conventional caching proxies, these policies may impose or collect usage statistics, among others. Transparency is achieved by intercepting HTTP traffic (for example) and forwards it to the proxy through a technique or a variation of port forwarding. Thus, regardless of the settings user’s explicit, its use is always subject to the policies of network utilization. RFC 3040 defines this method as a proxy interceptor.
Why? Because the transparent proxy does not work well with certain web browsers. With most browsers it works fine, but if even a quarter of its users are using browsers badly-behaved, you can expect the help desk costs exceed any benefits you may gain from the transparent proxy. Unfortunately, these browsers are widely used.
These browsers behave differently if they know there is a proxy, all other browsers follow the standard, and the only change they make a proxy is to direct requests to a different machine and port. Browsers that do not behave well leave some HTTP headers out of the request, and only add them if they know there is a proxy. Without those headers, user commands like “reload” does not work if there’s a proxy between the user and the source.
The transparent proxy also adds a layer of complexity, which can complicate transactions that would otherwise be simple. For example, web-based applications that require an active server can not take the test server making a connection, they will be connected to the proxy server instead.
Open Proxy
An open proxy is a proxy server that is accessible by a user. Generally, a proxy server allows users of a network group to store and forward internet services such as DNS or web pages to reduce and control the bandwidth used by the group. With an open proxy, but any Internet user is able to use this service routing.
Anonymous Proxy
An anonymous proxy is a tool that strives to do activities on the Internet without a trace. Access the Internet for the user, protecting personal information by hiding the information identifying the source computer.
The operator of the proxy can still relate the information to the users’ page views, and information sent or received.
Who does not want to depend on only one operator uses a proxy chain of different proxies.
If a chain of proxies do not collaborate with others and do not store users’ information, it becomes impossible to identify users by IP number.
There are also networks of computers that act each as a proxy, thus forming chains of proxies seeking free traffic automatically routes. Networks are as I2P – Anonymous Network. Also has measures against traffic analysis.
You can send anonymous e-mail and visit web pages anonymously. There is also a simple anonymous messenger, IRC, and file exchange.
Software
- Squid
- Microsoft Internet Security and Acceleration Server (ISA Server)
- WinProxy
- Winconnection
- BlueCoat
- Sonicwall
- Polipo
Study: From Wikipedia, the free encyclopedia. The text is available under the Creative Commons.
