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Module 15: Network Structures.• Background.• Motivation.• Topology.• Network Types.• Communication.• Design Strategies. 15.1 Silberschatz and Galvin 1999 Node Types.• Mainframes (IBM3090, etc.). – example applications:. airline reservations. banking systems. – many large attached disks.• Workstations (Sun, Apollo, Microvax, RISC6000, etc.). – example applications:. computer-aided design. office-information systems. private databases. – zero, one or two medium size disks. 15.2 Silberschatz and Galvin 1999 Nodes Types (Cont.).• Personal Computers. – example applications:. office information systems. small private databases. – zero or one small disk. 15.3 Silberschatz and Galvin 1999 A Distributed System. 15.4 Silberschatz and Galvin 1999 Motivation.• Resource sharing. – sharing and printing files at remote sites. – processing information in a distributed database. – using remote specialized hardware devices.• Computation speedup – load sharing.• Reliability – detect and recover from site failure, function transfer,. reintegrate failed site.• Communication – message passing. 15.5 Silberschatz and Galvin 1999 Topology.• Sites in the system can be physically connected in a variety of. ways; they are compared with respect to the following criteria:. – Basic cost. How expensive is it to link the various sites in. the system?. – Communication cost. How long does it take to send a. message from site A to site B?. – Reliability. If a link or a site in the system fails, can the. remaining sites still communicate with each other?.• The various topologies are depicted as graphs whose nodes. correspond to sites. An edge from node A to node B. corresponds to a direct connection between the two sites• The following six items depict various network topologies 15.6 Silberschatz and Galvin 1999 • Fully connected network.• Partially connected network. 15.7 Silberschatz and Galvin 1999 • Tree-structured network.• Star network. 15.8 Silberschatz and Galvin 1999 • Ring networks: (a) Single links. (b) Double links. 15.9 Silberschatz and Galvin 1999 • Bus network: (a) Linear bus. (b) Ring bus 15.10 Silberschatz and Galvin 1999 Network Types.• :Local-Area Network (LAN) – designed to cover small. geographical area – Multiaccess bus, ring, or star network – Speed 10 megabits/second, or higher – Broadcast is fast and cheap – Nodes:. usually workstations and/or personal computers. a few (usually one or two) mainframes 15.11 Silberschatz and Galvin 1999 Network Types (Cont.)• Depiction of typical LAN:. 15.12 Silberschatz and Galvin 1999 Network Types (Cont.).• Wide-Area Network (WAN) – links geographically separated. sites – Point-to-point connections over long-haul lines (often leased. from a phone company) – Speed 100 kilobits/second – Broadcast usually requires multiple messages – Nodes:. usually a high percentage of mainframes. 15.13
