Proxy (Computer Network)

network proxy

How The Network Proxy Works?

Schematic representation of a proxy (in the middle of the picture), which passes on the data transfer between the two outer computers.

A free web proxy (proxy representative “proxy”, from Latin proxus “next”) is a communication interface in a network. He works as a mediator who receives inquiries on the one hand, and then connects to the other via his own address.

If the proxy is used as a network component, on the one hand the actual address of a communication partner remains hidden from the other communication partner, which creates a certain anonymity.

On the other hand, as a (possible) link between different networks, it can realize a connection between communication partners even if their addresses are incompatible with each other and a direct connection is not possible.

In contrast to a simple address translation (NAT), a proxy server, also called a dedicated proxy, can manage and influence the communication itself, instead of passing the packets through unseen.

Specializing in a specific communication protocol, such as: As HTTP or FTP, he can analyze the data coherently, filter requests and make any adjustments if necessary, but also decide whether and in what form the response of the target to the actual client is passed.

Sometimes it serves to cache certain answers so that they can be retrieved more quickly in the case of recurring requests without having to request them again from the destination.

Working Method And Demarcation

Multiple Dedicated Proxies are often used in parallel on a single device to handle different protocols.

A generic proxy, also called circuit level proxy, is used as a protocol-independent filter on a firewall application.

He realizes there a port- and address-based filter module, which also supports a (possible) authentication for establishing a connection. In addition, it can be used for easy forwarding by listening on one port of a network adapter and passing the data to another network adapter and port.

He can neither see the communication nor lead nor influence the communication, because he does not know the communication protocol.

The Difference To A NAT Device

Technically, a typical proxy operates as a traffic intervening communication partner on the OSI layer 7, terminating the connections on both sides (thus being two separate connections) rather than simply passing the packets through like a NAT device.

Such a Dedicated Proxy is thus a utility for computer networks, which mediates in the traffic, and is therefore also called a proxy server: As an active mediator, it acts like a server to the requesting client and to a client, the other side, the target system,

However, there are overlaps with NAT in the generic Circuit Level Proxy operating on OSI layers 3 and 4, which may use the technique of simple address translation.

Nevertheless, NAT takes a barely noticed role among the proxies. Therefore, it is assumed in the following of the first-described variant, when in general of a (typical) proxy is mentioned.