what is difference between hub, switch and router?

Question

what is hub?
what is switch?
what is router?
and what is difference between them?

Answer 1

A hub is typically the least expensive, least intelligent, and least complicated of the three. Its job is very, very simple: anything that comes in one port is sent out to the others. That's it. Every computer connected to the hub "sees" everything that every other computer on the hub sees. The hub itself is blissfully ignorant of the data being transmitted. For years, simple hubs have been quick and easy ways to connect computers in small networks.

A switch does essentially what a hub does, but more efficiently. By paying attention to the traffic that comes across it, it can "learn" where particular addresses are. For example, if it sees traffic from machine A coming in on port 2, it now knows that machine A is connected to that port, and that traffic to machine A needs to only be sent to that port and not any of the others. The net result of using a switch over a hub is that most of the network traffic only goes where it needs to, rather than to every port. On busy networks, this can make the network significantly faster.

A router is the smartest, and most complicated of the bunch. Routers come in all shapes and sizes, from the small four-port broadband routers that are very popular right now, to the large industrial strength devices that drive the internet itself. A simple way to think of a router is as a computer that can be programmed to understand, possibly manipulate, and route the data its being asked to handle. For example, broadband routers include the ability to "hide" computers behind a type of firewall, which involves slightly modifying the packets of network traffic as they traverse the device. All routers include some kind of user interface for configuring how the router will treat traffic. The really large routers include the equivalent of a full-blown programming language to describe how they should operate, as well as the ability to communicate with other routers to describe or determine the best way to get network traffic from point A to point B.

Answer 2

hub n. In a network, a device joining communication lines at a central location, providing a common connection to all devices on the network. The term is an analogy to the hub of a wheel. See also active hub, switching hub. switch n. 4. In networking, a device capable of forwarding packets directly to the ports associated with particular network addresses. See also bridge, multilayer, router.

Answer 3

HUB:

An Ethernet hub or concentrator is a device for connecting multiple twisted pair or fiber optic Ethernet devices together, making them act as a single segment. Hubs work at the physical layer of the OSI model. Hubs are either active or passive. Active hubs repeat the signal received at one port out each of the other ports (but not the original one). The device is thus a form of multiport repeater. Ethernet hubs are also responsible for forwarding a jam signal to all ports if it detects a collision.

Hubs also often come with a BNC and/or AUI connector to allow connection to legacy 10BASE2 or 10BASE5 network segments. The availability of low-priced Ethernet switches has largely rendered hubs obsolete but they are still seen in older installations and more specialist applications.

SWITCH:

A network switch (or just switch) is a networking device that performs transparent bridging (connection of multiple network segments with forwarding based on MAC addresses) at up to the speed of the hardware. Common hardware includes switches, which can connect at 10,100, or 1000 megabits per second, at half or full duplex. Half duplex means that the device can only send or receive any given time, whereas full duplex can send and receive, at the same time. The use of specially designed expansion also makes it possible to have large numbers of connections utilizing different mediums of networking, including Ethernet, Fibre Channel, ATM, 802.11, to name frequently used technologies.

A switch can connect Ethernet, Token Ring, Fibre Channel or other types of packet switched network segments together to form a Internetwork.

If a network has only switches and no hubs then the collision domains are either reduced to a single link or, if both ends support full duplex, eliminated altogether. The principle of a fast hardware forwarding device with many ports can be extended to higher layers giving the multilayer switch.

A repeater is the simplest multi-port device in use. However, its technology has been considered outdated since a hub is a "dumb device", as it resends every datagram it receives to every port except the original incoming. With multiple computers, the speed quickly slows down, and collisions start occuring, making the connection even slower. However, with the advent of the network switch, this problem has been solved.

ROUTER:

A router (IPA pronunciation: [raʊtɚ] or [rutə(ɚ)]) is a computer networking device that forwards data packets across a network toward their destinations, through a process known as routing. Routing occurs at Layer 3 (the network layer i.e. Internet Protocol (IP)) of the OSI seven-layer protocol stack.

Answer 4

HUB: Operates on Layer 1, simply repeats on all ports, what is sent on one port.
SWITCH: Operates on Layer 2. Makes an intelligent decision where to send the frame based on Data-link Layer (or MAC) address.
ROUTER: Operates on Layer 3. Makes an intelligent decision where to send the packet - irrelevant of the datalink protocol being used. The Layer 3 address is network wide unique, so you can use it through an entire network composed of different technologies (Ethernet/ATM/Frame Relay/FDDI whatever you choose.

Answer 5

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