LANs : Local Area Networks
• Typically connects computer in a single building or campus.
• Developed in 1970s.
• Medium : optical fibres, coaxial cables, twisted pair, wireless.
• Low latency (except in high traffic periods).
• High speed networks (0.2 to 100 Mb/sec).
• Speeds adequate for most distributed systems
• Problems : Multi media based applications
• Typically buses or rings.
• Ethernet, Token Ring

Network Type Ethernet FDDI Token Ring Apple LocalTalk Wireless

Data Transfer Rate 10 (up to 100) Mbits/s 100 Mbits/s 4 or 16 Mbits/s 0.23 Mbits/s 1-3 Mbits/s

MANs : Metropolitan Area Networks
• Generally covers towns and cities (50 kms)
• Developed in 1980s.
• Medium : optical fibres, cables.
• Data rates adequate for distributed computing applications.
• A typical standard is DQDB (Distributed Queue Dual Bus).
• Typical latencies : < 1 msec.
• Message routing is fast.

WANs : Wide Area Networks
• Developed in 1960s.
• Generally covers large distances (states, countries, continents).
• Medium : communication circuits connected by routers.
• Routers forwards packets from one to another following a route from the sender to the receiver. Store-and-Forward
• Hosts are typically connected (or close to) the routers.
• Typical latencies : 100ms - 500ms.
• Problems with delays if using satellites.
• Typical speed : 20 - 2000 Kbits/s.
• Not (yet) suitable for distributed computing.
• New standards are changing the landscape.