switches, bridges, routers...can any one tell me their diffrences in terms of their applications?

Answer 1

A hub connects computers, but sends all traffic to all ports which results in network collisions.

A switch is like a hub, but smarter. It keeps track of which computer asks for which piece of data and has far less collisions, if any. Switches that are for home users are only slightly more expensive than hubs.

A router is like a switch, but also can assign ip addresses, forward network traffic coming in on a certain port to a certain ip address, block certain ports, etc.

A network bridge merges, for lack of a better word, two network connections on a computer. Honestly I haven't ever needed a network bridge so I can't say much about them.

Answer 2

A switch or HUB simply passes network traffic transparently on a network segment. This can be used to extend the quantity of physical network ports on a network segment.

A bridge connects two networks together. It is a switch that moves packets an between entire network. A Bridge is good for joining two networks together.

A router forwards data packets to a network segment by examining the destination and a self-contained routing table. A Router is useful for controlling the destination network segment of the packet.

Answer 3

I'll try to describe application-wise and not so technically:

Switch: a device that lets you connect several devices to a local network segment through wires (one per device). It has the property to "learn" where particular machine addresses are. So if one computer initiates a "conversation" with another, the switch directs data between the two without sending it to other computers, making the network more efficient.

Bridge: a device that lets you join two local area networks (LANs) or two segments of the same LAN. Often the two segments/LANs are made of different media, ie. cable Ethernet and wireless (WiFi). Bridges also "learn" machine addresses of the computers connected on their side, so they are also useful to isolate traffic: you may use them to prevent the Accounting deptartment's traffic to go to the Engineering Dept.

Router: a computer that can be programmed to redirect or "route" data from one network to one or more networks. For example, your home router is used to interconnect two different networks: the ISP's DSL network and your Ethernet-based and/or WiFi home network(s). Sofware can be running in the router to hide your PCs behind a firewall. This implies modifying data somehow as they traverse the device. They often have software that manages the LAN's IP addresses, known as DHCP (Dynamic Host Configuration Protocol) server. A router can be a hardware and software combination running on a PC, or be a special-purpose computer, usually in a case that doesn't look like a computer.

For all these devices, machine addresses are not IP addresses, but a unique number that is assigned to the hardware of each active device in the network. When a PC requests and gets an IP address from the DHCP server (running in the router), it gets associated to its own machine address. The Internet uses IP (Internet Protocol) addresses, thus this process is what gives you access to the WWW.