1、What is a LAN ?,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.ThusCommunicate DirectlyModerately Sized Geographic AreaModer
2、ate Data Rate,Basic Requirements of a LAN,Data rate of 1 to 100 MbpsGeographic distances spanning at most 1-5 kmAbility to support several hundred independent devicesSimplicity, or use of the simplest mechanisms that have the required functionality and performanceReliability and good error character
3、istics,Basic Requirements of a LAN,Minimal dependence on any centralized components or controlEfficient use of shared resources, including the network channelStability under high loadFair access (bandwidth, delay) to the network by all devicesEasy installationEase of reconfiguration and maintenanceL
4、ow cost,LAN Extension,Network Topologies,A,C,E,A,E,B,D,B,D,F,A,E,B,D,A,E,B,D,C,E,B,D,F,A,A,B,C,C,C,C,Star Ring Dual Ring,Bus Tree Dual Bus,Network Topologies,A,B,C,A,B,C,D,A,C,E,B,D,F,Dual Bus Dual Bus Mesh,A,G,B,E,D,F,C,H,Snowflake,Network Topologies,A,E,B,D,C,F,J,G,I,H,K,O,L,N,M,橋接器,橋接器,橋接器,Bridge
5、d Ring Networks,C,A,B,F,D,E,G,H,集線器 或 中樞器,.,Hub or Concentrator,8,Rules of Using Repeaters,Maximum 5 sections Maximum 4 repeaters Maximum 3 sections can have hosts Within a whole collision domain Reason: Propagation round trip latency 51.2 ms,9,CSMA/CD,listen before talk listen while talking wait be
6、fore talk againBEBA Algorithm： n : (n 10 r : (unit: slot time) 0 = r 2k random waiting factor Slot time = 51.2 ms.,Calculation of Slot time,元件,編碼器0.1 ms0.1 ms552.0 ms收發器電纜5.13ns/公尺0300公尺300公尺3.08 ms收發器（傳送路徑）0.05 ms0.3 m 332.10 ms收發器（接收路徑）0.05 ms0.6us301.95 ms收發器（衝撞路徑）00.9 m 032.70 ms同軸電纜4.33ns/公尺015
7、00公尺1500公尺12.99 ms半訊號增益器間電纜5.13ns/公尺01000公尺1000公尺10.26 ms電纜驅動器0.1 ms0220.40 ms電纜接收器0.1 ms0220.40 ms 訊號增益器（增益路徑）0.2 ms0.4 ms201.20 ms訊號增益器（衝撞路徑）0.2 ms0.2 ms020.80 ms載波感測00.2 ms501.00 ms衝撞偵測00.2 ms051.00 ms 訊號上升時間00.1 ms300.30 ms（至 70% 於500公尺處） 訊號上升時間（由 50%02.0 ms036.00 ms至 94% 於 500公尺處）衝撞分割00.2 ms010
8、.20 ms,元件 穩定延遲,元件 啟動延遲,前進路徑 元件數,整體延遲,回程路徑 元件數,訊號來回傳遞最長延遲 46.38 ms,IEEE Project 802 Standards,IEEE 802.1 High Level InterfaceIEEE 802.1D Local Bridge (Spanning Tree Algorithm)IEEE 802.1G Remote BridgeIEEE 802.2 LLC (Logical Link Control)IEEE 802.3 CSMA/CD (Carrier Sense Multiple Access with Collision
9、 DetectionIEEE 802.4 Token-BusIEEE 802.5 Token-RingIEEE 802.6 DQDB (Distributed Queue Dual Bus),IEEE Project 802 Standards,IEEE 802.7 Broadband Technical Advisory GroupIEEE 802.8 Fiber Optic Technical Advisory GroupIEEE 802.9 Integrated Voice and Data LAN Working GroupIEEE 802.10 LAN Security Workin
10、g GroupIEEE 802.11 Wireless LANIEEE 802.12 Demand-Priority (100VG-AnyLAN)IEEE 802.14 CATV Networks,802.3,CSMA/CD,802.4,Token-Bus,802.5,Token-Ring,802.6,DQDB,802.9,Isochronous,802.11,Wireless,802.12,100VG-AnyLAN,Ethernet,LAN,AX3T9.5,FDDI,802.2 LLC,802.1 網路連結技術,Physical,MAC,LLC,IEEE Project 802 Standards,
