Lecture 4(BCM VI)

What Is the Purpose of a Proxy Server?

 

A proxy server is a special type of network node that alters packets that pass through it, masking their IP addresses and making it seem that the packets originated at the proxy system. Proxy servers may be a natural part of your network architecture, or they may be third-party servers that provide anonymity to their users. Using a proxy can help mask your activities online from prying eyes, but it can also open up your business's computer network to a host of security threats.

Networking

In some cases, a proxy server may be required due to your networking configuration. If you have multiple PCs in your home, the router provided by your Internet service provider serves as a sort of proxy for your system. All outgoing traffic first travels to the router, which serves as your connection to the outside world. From the perspective of the Internet, all your traffic seems to come from a single IP address, no matter how many machines you connect on your side of the router.

Access Control

In some cases, a proxy may serve as a central node for logging or filtering Internet traffic. A company may route all traffic through an internal proxy in order to prevent users from accessing sites that are not work related and many even contain inappropriate content, as well as to record the activities of its users online. A proxy may also require a username and password for Internet access, preventing unauthorized users from spending time online on non-company business. A proxy server can also cache commonly accessed resources, reducing the amount of network traffic and improving response times for users.

Anonymity

Since all traffic routed through a proxy appears to originate from that proxy, some users take advantage of this system for anonymity purposes. Using an external proxy can make it difficult for a third party to track your activities online. It is important to note, however, that the owner of a proxy can easily monitor activity that passes through it, so using an insecure proxy may open you up to many security risks. In addition, since your Web traffic must travel to the proxy server before it can navigate to the target server, this setup can introduce considerable amounts of latency and slow down your browsing session.

International Proxies

Proxies are also useful when you're dealing with international restrictions. Some websites alter the content they provide based on the user’s home country, and using an international proxy that masks your country of origin can help bypass those restrictions. In extreme cases, users in countries that censor the Internet can use international proxies to access banned content, and free-speech advocates and activists can use the anonymity provided by proxies to share information freely with other users.

What Is a Proxy Server?

A proxy server (usually known as a “proxy” or “application-level gateway”) is a server (either a computer or an application) that acts a gateway between a local network and a large-scale network.

An example of that would be a server acting as an intermediary between your computer and the Internet.

Proxy servers can usually be categorized as being:

·         Forward – The standard proxy category, Forward proxies are the intermediary between a computer and a wider network.

·         Reverse – Reverse proxies are intermediaries between the web and a smaller group of servers. For instance, a Reverse proxy could act as a gateway between the Internet and a corporate LAN network.

·         Open – Open proxies (also called “public proxies”) can be accessed by any online user. They are usually offered to the public free of charge.

 How Does a Proxy Server Work?

Basically, a proxy server will act as an intermediary between a client and the server from which the client is requesting a certain service. It will take the client’s request, and perform it on their behalf.

Here’s a basic example: Say you want to use a proxy server to access a certain web page. The proxy will receive your request, and will do one of the following things:

·         It will analyze its local cache to see if it can find that particular web page. If it finds it, it will return it to you without having to forward your request to the Internet.

·         If the proxy doesn’t locate the web page in its local cache, will request that web page from the web. However, it will not use your IP to do it. Instead, the proxy will act as the client on your behalf, and use one of its own IP addresses. Once it gets the page, it will relate it to your original request, and forward the page back to you.