Types of links • Broadcast links: -Single communication channel is shared by all machines. -Packets [messages/contexts] sent by any machine received by all. -Packet [Address field] : Specifies intended recipient. -Receiver checks address field. • Point-to-point links: -localized networks use broadcasting, larger use point-to-point. -packets from source are transferred via intermediate machines to destination. [finding best route is important]. Categories of Networks • Local Area Networks • Metropolitan Area Networks • Wide Area Networks • Internetworks Broadcast Networks • Classification of interconnected processors by scale. Local Area Networks – privately owned and links the devices in a single office, building, or campus. - Limited to few kilometers. - Allow resources (both h/w & s/w) to be shared. Eg: Server-large capacity disk drive (provide service to clients). LAN can be distinguished by the parameters: 1.size 2.transmission media ---which? 3.topology (bus, ring, star) - Data Rate: 4 to 16 Mbps – earlier 100 0r 1000 Mbps - nowadays - Hub: A central device in a star topology that provides a common connection among the nodes. An isolated LAN connecting 12 computers to a hub in a closet Metropolitan Area Networks • Size between a LAN and a WAN. • Designed for customers, - who need a high speed connectivity net - have endpoints over a city • Eg: - Telephone company network - Cable TV network Metropolitan Area Networks • Television signals & internet being fed into headend for distribution to homes. Wide Area Networks • Long-distance transmission of data, image, audio & video over large geographical area. [country, continent] • Two types of WAN: - Switched WAN - Point-to-Point WAN • Switched WAN: - connects end systems comprise a router (internet-working connecting device) that connects to another LAN or WAN. • Point-to-Point WAN: - connects home computer or a small LAN to an ISP. WANs: a switched WAN and a point-to-point WAN Wide Area Networks • Relation between hosts on LANs and the subnet. • Subnet : carry messages from host to host. • Subnet: 1.Transmission lines (move bits b/w m/cs, made of wires, fibres etc) 2. Switching elements (routers) - computers connect one or more transmission lines. - choose outgoing line to forward data. Wide Area Networks • Sending host cuts messages into packets, then packets are injected into n/w. • Stream of packets are transported from sender to receiver. • Packet is routed via ACE instead of ABDE, ACDE. • Routing decision is made by router A based on algorithm. Internetwork:connection of two or more networks. A heterogeneous network made of four WANs and two LANs THE INTERNET •The Internet is a communication system that has brought a wealth of information to our fingertips and organized it for our use. •A network is a group of connected communicating devices such as computers and printers. •An internet is two or more networks that can communicate with each other.