NETWORK SWITCHES vs. ROUTERS

Switches and Routers are just but two of the active components that make up a network setup. Before we go to the differentiation of switches to routers we should first then give meaning to the active components. Active components ; in an electrical, computer or storage system, active components are those that require electrical power to operate. This could include the power supply, fans, storage device, transistors, diodes and other integrated circuits but would exclude system components such as the chassis, capacitors or enclosures that do not require electrical power to operate (called passive components).

NETWORK SWITCH

On an Ethernet local area network (LAN), a switch determines from the physical device (Media Access Control or MAC) address in each incoming message frame which output port to forward it to and out of. In a wide area packet-switched network such as the Internet, a switch determines from the IP address in each packet which output port to use for the next part of its trip to the intended destination. In the simplest networks, a switch is not required for messages that are sent and received within the network. For example, a local area network may be organized in a Token Ring or bus arrangement in which each possible destination inspects each message and reads any message with its address.

Circuit-Switching versus Packet-Switching

A network's paths can be used exclusively for a certain duration by two or more parties and then switched for use to another set of parties. This type of "switching" is known as circuit-switching and is really a dedicated and continuously connected path for its duration. Today, an ordinary voice phone call generally uses circuit-switching.

Most data today is sent, using digital signals, over networks that use packet-switching. Using packet-switching, all network users can share the same paths at the same time and the particular route a data unit travels can be varied as conditions change. In packet-switching, a message is divided into packets, which are units of a certain number of bytes. The network addresses of the sender and of the destination are added to the packet. Each network point looks at the packet to see where to send it next. Packets in the same message may travel different routes and may not arrive in the same order that they were sent. At the destination, the packets in a message are collected and reassembled into the original message.

ROUTERS

In packet-switched networks such as the Internet, a router is a device or, in some cases, software in a computer, that determines the next network point to which a packet should be forwarded toward its destination. The router is connected to at least two networks and decides which way to send each information packet based on its current understanding of the state of the networks it is connected to. A router is located at any gateway (where one network meets another), including each point-of-presence on the Internet. A router is often included as part of a network switch.

A router may create or maintain a table of the available routes and their conditions and use this information along with distance and cost algorithms to determine the best route for a given packet. Typically, a packet may travel through a number of network points with routers before arriving at its destination. Routing is a function associated with the Network layer (layer 3) in the standard model of network programming, the Open Systems Interconnection (OSI) model. A layer-3 switch is a switch that can perform routing functions.


CONCLUSION:

A traditional Layer 2 switch is dealing with Ethernet frame data -- specifically, MAC addresses. A switch has a CAM (content addressable memory) table that is used to hold MAC addresses and then make a decision as to what switch port to forward to. Routers are Layer 3 devices and are concerned with routing protocols, such as OSPF, and routable protocols such as IP. Another distinction is that while switches look at physical frames, routers deal with routable addresses like 12.16.1.1.