Thursday, 5 October 2017

what is a proxy server? Explained



What is proxy server?


A proxy server,s also called a "proxy" or "application-level gateway", is a computer that acts as a gateway between a local network (e.g., all of the computers at the same company or in 1 building) and a larger-scale system like the Internet. Proxy servers provide greater performance and security. Sometimes, they monitor employees' use of external resources.

All incoming data passes through one interface and can be forwarded to the rest of the network via a different interface. By blocking direct access between two networks, proxy servers make it far harder for hackers to find inner addresses and details of a personal network.

Some proxy servers are a group of servers or applications which block common Internet services. By way of example, an HTTP proxy intercepts net access, and an SMTP proxy intercepts email. A proxy server uses a network addressing scheme to present a single organization-wide IP address to the web. The server funnels all user requests to the net and returns answers to the proper users. In addition to restricting access from outside, this mechanism may stop inside users from reaching specific Internet resources (e.g., certain sites). A proxy server is also among the elements of a firewall.

Next time an internal user requests the same URL, the proxy can serve the local copy rather than retrieving the first across the community, improving performance.

Note: Don't confuse a proxy server using a NAT (Network Address Translation) device. A proxy server connects to, responds to, and receives visitors from the web, acting on behalf of their client computer, even though a NAT device transparently changes the origination address of visitors coming through it before passing it to the net.

For people who know the OSI (Open System Interconnection) model of media, the technical difference between a proxy and a NAT is that the proxy server functions on the transport layer (layer 4) or greater of the OSI model, whereas a NAT operates on the network layer (layer 3).