Establishing Connections Networking Modes: When you are evaluating a network, you concentrate on circuit switching versus packet switching. But it's also very important to consider the networking mode, which can be either connection oriented or connectionless Connection-Oriented Networking As time-sensitive applications become more important, connection-oriented networks are becoming increasingly desirable. In a connection-oriented network, the connection setup is performed before information transfer occurs. all the subsequent information follows the same path to the destination. In a connection-oriented network, there can be some delay up front while the connection is being set up; but because the path is predetermined, there is no delay at intermediate nodes in this type of network after the connection is set up. The (PSTN, SONET) circuit switching and ATM, (Frame Relay) packet switching, use the connection-Oriented Networking.

Continue…….. Connectionless Networking In a connectionless network, no explicit connection setup is performed before data is transmitted. Instead, each data packet is routed to its destination based on information contained in the header. In other words, there is no preconceived path. Rather, each fragment (that is, packet) of the overall traffic stream is individually addressed and individually routed. In a connectionless network, the delay in the overall transit time is increased because each packet has to be individually routed at each intermediate node. Applications that are time sensitive would suffer on a connectionless network because the path is not guaranteed. All packet switched networks are connectionless Networking like internet

Continue…….. Switching Mode: There are two types of switching modes Circuit switching mode Packet switching mode Circuit switched Mode Circuit switching has been the basis of voice networks worldwide for many years. You can apply three terms to the nature of a circuit-switched call to help remember what this is: continuous, exclusive, and temporary. One of the key attributes of a circuit-switched connection is that it is a reserved network resource that is yours and only yours for the full duration of a conversation. But when that conversation is over, the connection is released. A circuit-switched environment requires that an end-to-end circuit be set up before a call can begin. A fixed share of network resources is reserved for the call, and no other call can use those resources until the original connection is closed. A call request signal must travel to the destination and be acknowledged before any transmission can actually begin.

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Continue….. Advantages of circuit switching Mode Reduce number of transmission lines Reduce routing processing calculation Speed up communication Suitable for voice communication Disadvantages of circuit switching Mode Circuit establishing time Not efficient use of transmission medium bandwidth

Continue…….. Packet Switching Mod The information divided into small pieces called packet These packet transmitted over network in different routes. Packet switching mode works on store-and-forward mechanism. The packets are of different size Each packet contain two very importants massages i.e. The distination address and the sequece number Routers need more routing calculation s. There is variation in processing time (delay) of packets, it is called jitter. There are two types of packet switching network, connection oriented packet switching and connectionless packet switching network. Advantages and disadvantages of packet switching Network Latencies occurs due to store-and-forward mechanism Packets are loss if there is heavy traffic over network. Packet switching network is suitable for the transmission of data which is not time sensitive like text data it is not suitable for the data transmission like audio and video

Internet versus PSTN PSTN Characteristics There would be no Internet without the PSTN. The communications links, or backbones, that ISPs run on are delivered over the PSTN, and the access lines for entry into the Internet are all subscriber lines that are part of the PSTN The PSTN basically includes telephones, fax machines, and circuit switches that set up continuous but temporary connections. In a PSTN environment, the circuit is established between two subscribers: The PSTN connects together two subscribers. But in the PSTN, a circuit is established between two subscribers and kept open for the duration of the call, including periods of silence. This provides guaranteed QoS and minimal latencies, and it means that the PSTN is optimized for voice and other real-time applications. It also means that the PSTN uses bandwidth inefficiently, making services more expensive

Continue…… Internet Characteristics The Internet basically includes clients, which are the user interface and the input/output device for information; the servers, which are the centralized repositories of wisdom that you are seeking; and the packet switches, which route and relay the packets of information between the clients and servers. Whereas the PSTN connects together two subscribers, the Internet connects together networks. As on the PSTN, messages on the Internet are routed to specific end devices. These messages take various forms, such as , instant messaging, and real-time audio/video communications. Unlike the PSTN, however, the Internet breaks down the messages into packets of data, which contain the routing information, which will then lead them to their destination. Individual packets may take different routes, but they'll be reassembled in the proper order at the destination.