Telecommunication networks carry information signals among entities, which are geographically for apart. The communication switching system enables universal connectivity. Switches can be valuable asset to networking. Overall, they can increase the capacity and speed of our network. Every time in computer network we access the internet or another computer network outside our immediate location, our messages are sent through a maze of transmission media and connection devices. The mechanism for moving information between different computer network and network segment is called switching in computer network.
Figure 1: Switched network
Long distance transmission is typically done over a network of switched nodes. Nodes not concerned with content of data. A collection of nodes and connections is a communications network. Data routed by being switched from node to node. Nodes may connect to other nodes only, or to stations and other nodes. Node to node links usually multiplexed. However, switching should not be seen as a cure-all for network issues. There are two different switching technologies which are: 1) Circuit switching and 2) Packet switching.
1. Circuit Switching
Circuit switching was the first switching technique have been used in communication network. This is due to easy to carry analog signals. Circuit switching network establishes a fixed bandwidth channel between nodes before the users may communicate, as if the nodes were physically connected with an electrical circuit. The bit delay is constant during the connection, as opposed to packet switching, where packet queues may cause varying delay. In circuit switching, the transmission medium is typically divided into channels using Frequency Division Multiplexing (FDM), Time Division Multiplexing (TDM), or Code Division Multiplexing (CDM). A circuit is a string of concatenated channels from the source to the destination that carries an information flow. To establish the circuits, a signaling mechanism is used. This signaling only carriers control information, and it is considered an overhead. Since all decisions are taken by the signaling process, the signaling mechanism is the most complex part in circuit switching. Each circuit cannot be used by other callers until the circuit is released and a new connection is set up. Even if no communication is taking place in a dedicated circuit then, that channel still remains unavailable to other users. Channels that are available for new calls to be set up are said to be idle. Telephone network is example of circuit switching system. Virtual circuit switching is a packet switching technology that may emulate circuit switching, in the sense that the connection is established before any packets are transferred, and that packets are delivered in order. Unlike with packet switched networks, we cannot just send a ‘packet’ to the destination. We need to establish and later terminate the connection. We need to have some way of transmitting control information, we can either do this in band that the same channel we use for data or out of band which is on a seperate dedicated channel. Phone networks used in band signaling a while ago we could control switching and other functionality by playing tones into the telephone. Today in band signaling is considered unsecure and is not used except for compability with old systems. 2. Packet Switching
Packet switching is a communications paradigm in which packets are routed between nodes over data links shared with other traffic. In packet-based networks, the message gets broken into small data packets. These packets are sent out from the computer and they travel around the network seeking out the most efficient route to travel as circuit become available. This does not necessarily mean that they seek out the shortest route. Each packet may go different route from the others. Each packet contains a "header"...