What is a LAN l A LAN is

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What is a LAN ? l A LAN is a data communication system allowing

What is a LAN ? l A LAN is a data communication system allowing a number of independent devices to communicate directly with each other, within a moderately sized geographic area over a physical communications channel of moderate data rates. l Thus – Communicate Directly – Moderately Sized Geographic Area – Moderate Data Rate

Basic Requirements of a LAN l Data rate of 1 to 100 Mbps l

Basic Requirements of a LAN l Data rate of 1 to 100 Mbps l Geographic distances spanning at most 1 -5 km l Ability to support several hundred independent devices l Simplicity, or use of the simplest mechanisms that have the required functionality and performance l Reliability and good error characteristics

Basic Requirements of a LAN l Minimal dependence on any centralized components or control

Basic Requirements of a LAN l Minimal dependence on any centralized components or control l Efficient use of shared resources, including the network channel l Stability under high load l Fair access (bandwidth, delay) to the network by all devices l Easy installation l Ease of reconfiguration and maintenance l Low cost

Network Topologies C A E Star C F Bus E D Dual Ring A

Network Topologies C A E Star C F Bus E D Dual Ring A D B A E D Ring D C A D E B B C E Tree A B C F Dual Bus

Network Topologies B A A A B C D C B E C Dual

Network Topologies B A A A B C D C B E C Dual Bus B Mesh C A D H E G D F F Snowflake

Network Topologies G B C A E H F 橋接器 J D 橋接器 I

Network Topologies G B C A E H F 橋接器 J D 橋接器 I 橋接器 L A H B M K O 集線器 或 中樞器 N Bridged Ring Networks D . . . F G C E Hub or Concentrator

Rules of Using Repeaters Maximum 5 sections q Maximum 4 repeaters q Maximum 3

Rules of Using Repeaters Maximum 5 sections q Maximum 4 repeaters q Maximum 3 sections can have hosts q Within a whole collision domain q Reason: Propagation round trip latency < 51. 2 ms 8

CSMA/CD listen before talk q listen while talking q wait before talk again q

CSMA/CD listen before talk q listen while talking q wait before talk again q BEBA Algorithm： n : (n <= 16) collision times, more than 16 would give error message. k : Min (n, 10) k=n when n<=10，k=10 when n>10 r : (unit: slot time) 0 <= r < 2 k random waiting factor Slot time = 51. 2 ms. 9

IEEE Project 802 Standards l IEEE 802. 1 High Level Interface – IEEE 802.

IEEE Project 802 Standards l IEEE 802. 1 High Level Interface – IEEE 802. 1 D Local Bridge (Spanning Tree Algorithm) – IEEE 802. 1 G Remote Bridge l IEEE 802. 2 LLC (Logical Link Control) l IEEE 802. 3 CSMA/CD (Carrier Sense Multiple Access with Collision Detection l IEEE 802. 4 Token-Bus l IEEE 802. 5 Token-Ring l IEEE 802. 6 DQDB (Distributed Queue Dual Bus)

IEEE Project 802 Standards l IEEE 802. 7 Broadband Technical Advisory Group l IEEE

IEEE Project 802 Standards l IEEE 802. 7 Broadband Technical Advisory Group l IEEE 802. 8 Fiber Optic Technical Advisory Group l IEEE 802. 9 Integrated Voice and Data LAN Working Group l IEEE 802. 10 LAN Security Working Group l IEEE 802. 11 Wireless LAN l IEEE 802. 12 Demand-Priority (100 VG-Any. LAN) l IEEE 802. 14 CATV Networks

IEEE Project 802 Standards 802. 1 網路連結技術 LLC 802. 2 LLC 802. 3 802.

IEEE Project 802 Standards 802. 1 網路連結技術 LLC 802. 2 LLC 802. 3 802. 4 802. 5 802. 6 802. 9 802. 11 802. 12 CSMA/CD Token-Bus Token-Ring DQDB Isochronous Wireless Ethernet LAN 100 VGAny. LAN AX 3 T 9. 5 MAC FDDI Physical