Switching Techniques - In large networks there might be multiple paths linking sender and receiver. Information may be switched as it travels through various communication channels. There are four typical switching techniques available for digital traffic.
Conceived in the 1960's, packet switching is a more recent technology than circuit switching which addresses a disadvantage of circuit switching: the need to allocate resources for a circuit, thus incurring link capacity wastes when no data flows on a circuit.
Time space switching:- A time space (ts) switch takes the outputs of several time-division switches, for example, TSI switches and connects them as inputs as a space division switch. The effect of this paired arrangement is that packets can be swapped between different output lines.
Circuit switching is a switching method in which a dedicated communication path in physical form between two stations within a network is established, maintained and terminated for each communication session. It has basically three phases as circuit establishment, data transfer and circuit disconnect.
The majority of people, not having lines (cable or Ethernet) linked directly to the Internet, must use telephone lines (the most widely used network) to connect to the Internet. The connection is made using a modem, a device capable of converting digital data from the computer into analogue signals (that can circulate on telephone lines by amplitude or frequency modulation, in the same way as voice when you use the telephone).
Cell switching is associated with Asynchronous Transmission Mode (ATM) which is considered to be a high speed switching technology that attempted to overcome the speed problems faced by the shared media like Ethernet and FDDI. Cell switching uses a connection-oriented packet-switched network.
A circuit is a path between two or more points along which an electrical current flows. In data communication, we may consider a circuit as a specific path between two or more points along which signals can be carried. The signals may be analog, binary or digital. It has been shown in the Figures, wherein the link between PC and modem, link between modem and CTO and so on constitutes a circuit.
Datagram is better if numbers of packets are not very large. As it is a connectionless service there is no need to prior call set up. Therefore, It is more flexible and provides alternate route to avoid the congested part of the network.
Virtual Circuit (VC) - In this type connection, DTE selects the links to be used before communication to connect a receiver just as in the case of telephone network. In other words, we may say that a pre-planned route established before any packets are sent. A communications arrangement in which data from a source user may be passed to a destination user over various real circuit configurations during a single period of communication and the Information about the routing of packets is stored in all nodes throughout the set-up phase. Virtual circuits generally set up on a per connection basis and are disconnected when the connection is terminated and after that, the information in the network is erased. However, a permanent virtual circuit can be established as an option to provide a dedicated link between two facilities.
The purpose of ATM is to provide high speed, low-delay multiplexing and switching networks to support any type of user traffic, such as voice, data or video applications. This is specifically designed as single technology for voice, video, and data.
Fiber optic technology is considered to meet the ever-increasing demand of bandwidth for the exchange of information and WDM provides solutions for the ever-increasing demand of bandwidth through optical networks. In optical communication" the analog of FDM is referred to as wavelength-division multiplexing (WDM).
Cell relay is data transmission service that uses transmission technology referred to as Asynchronous Transfer Mode (ATM). As the name suggests, the data transmission unit is a fixed length of data known as a cell. High-speed transmission compared to other services like frame relay is possible with the cell relay method. The cell relay is considered by most to be the transport service of the future.
Because the Layer 2 protocols depend heavily on the features originally specified for PPP, it is worth examining this protocol more closely. PPP was designed to send data across dial-up or dedicated point to- point connections. PPP encapsulates IP, IPX, and NetBEUI packets within PPP frames, and then transmits the PPP-encapsulated packets across a point-to-point link. PPP is used between a dial-up client and an NAS.
The terminal connected to the packet switched network can communicate with multiple terminals at the same time using a single physical line. This makes it possible to set multiple logical paths called logical channels on a single physical line.