packet switching

overview,switched infrastructure network,switched nodes,circuit switched properties,packet switching principles,basic operations,use of packets,packet switching technique,datagram,virtual circuit,conclusion

1. PAPER NAME : COMPUTER NETWORKS STAFF NAME : MISS.S.MANIMOZHI MCA,M.Phil,PHD., CLASS : III BCA A SEMESTER : VI UNIT : III TOPIC : PACKET SWITCHING

2. PACKET SWICHING

3. Overview Networks are used to interconnect many devices. We have checked with Local Area Networks. Now, wide area networks Since the invention of the telephone, circuit switching has been the dominant technology for voice communications. Since 1970, packet switching has evolved substantially for digital data communications. It was designed to provide a more efficient facility than circuit switching for bursty data traffic. Two types of packet switching: Datagram (such as today’s Internet) Virtual circuit (such as Frame Relay, ATM)

4. Switch ed infrastructure Networks Long detachment broadcast between stations (called “end campaign”) is usually done over a set of connections of switch ing nodes . Switching n odes do not concern with satisfied of information . Their rationale is to have the resources for a switching flair that will move the data from node to nodule during they accomplish their goal(the end device. A gathering of nodes and relatives forms a communications network. In a switched infrastructure set of connections report inward bound the network from a station are running scared to the goal by being switched from node to node .

5. Switch Nodes Nodes may attach to additional nodes, or to some stations . set of connections is frequently partly connected However, several neglected relatives are enviable for reliability. Two unlike switching technologies Circuit switch Packet switch

6. Circuit Switching Properties Incompetence Direct capacity is dedicated for the whole duration of a correlation If no data, capacity is wasted Delay Long initial delay: circuit establishment takes time Low data delay: after the circuit institution in sequence is transmit at a fixed data rate with no setback other than the transmission delay. The delay at each node is insignificant. Residential for voice traffic (public phone network) but can also applied to information traffic. For voice connections, the resulting circuit will enjoy a elevated percentage of operation because most of the time one party or the other is talking.

7. Subscribers : the campaign that attach to the network. Subscriber loop: the link between the subscriber and the network interactions: the switching centers in the report mill. End office: the switching center that directly wires subscribers. Trunks : the undergrowth between exchanges. They carry several voice-regularity circuits using either FDM or synchronous TDM.

8. Packet Switching Principles Predicament of course switching designed for voice overhaul Resources dedicated to a finicky call For information communication, m uch of the occasion the connection is idle (say, web browsing) information rate is preset Both ends must operate at the same rate during the total stage of relation. Packet switching is intended to tackle these troubles.

9. Basic Operation information are transmit in short packets classically at the order of 1000 bytes Longer messages are split into sequence of packets Each packet contain a segment of user information plus some control info Control info contain at least Routing (addressing) info , so as to be routed to the planned objective. Recall the content of an IP subtitle! store and forward On each switching node, packets are received, stored momentarily (buffered) and agreed on to the next node.

10. Use of Packets

11. Packet Switching Technique A s tation break long communication into packet. Packets are sent out to the system successively, one at a occasion How will the system switch this torrent of packet as it challenge to direction them through the network and transport them to the intended objective? Two approach Datagram approach Virtual circuit approach

12. Datagram every one packet is treated discretely with no position to packet that have departed before. Each node choose the next node on a packet’s path. Packets can take any potential direction. Packets may land at the receiver out of order. packet may go missing. It is u p to the head put to rearrange packets and accept up from missing carton Example: Internet

13. Virtual Circuit In practical route, a p replanned route is established before any packets are sent, then all packets follow the same route. Each packet contains a practical route identifier in its place of objective attend to and each node on the pre conventional route knows where to forward such packets. The node need not make a navigation decision for each pack. Example: X.25, Frame Relay, ATM 14

14. Virtual Circuits v Datagram implicit circuit System can provide sequencing (packets arrive at the same order) and error control (retransmission between two nodes). Packets are frontward more speedily Based on the virtual circuit identifier No navigation decisions to make Less unswerving If a node fails, all fundamental circuits that pass through that node fail. Datagram No call complex phase Good for burs T v data, such as Web application More plastic If a node fails, packet may find an interchange route Routing can be used to avoid congested parts of the system 16

15. CONCLUSION A router in fact is a switch that create association between an participation and production port and an electrical switch connect the input to the production to the liveliness flow .