1、第三章,Copyright ?1998, Cisco Systems, Inc.,ICRC_revision_11.3,物理層和數(shù)據(jù)鏈路層,物理層和數(shù)據(jù)鏈路層標準,Physical (bits, signals, clocking),LAN,WAN,Data Link (frames),E t h e r n e t,8 0 2 . 3,8 0 2 . 5,F D D I,802.2 LLC,X.25 Link Frame Relay,ISDN PPP,EIA-530 V.35,Dial on Demand,SDLC,HDLC,V.24,HSSI,G.703,EIA/TIA-232,EIA/T

2、IA-449,局域網(wǎng)數(shù)據(jù)鏈路子層,LLC完成上半層的軟件功能 MAC完成下半層的硬件功能,Media Access Control（介質(zhì)訪問控制）,Logical Link Control （邏輯鏈路控制）,Network,Data Link,Physical,LLC,MAC,MAC Frame,802.3 LLC,Packet or Datagram,物理層和邏輯地址,0000.0c12.3456,MAC地址,MAC地址被燒進網(wǎng)絡(luò)接口卡的ROM芯片中,24 bits,24 bits,0000.0c12. 3456,制造商代碼,序列號,ROM,RAM,MAC地址判定,Host Y,Host Z

3、,Query,Response,Example 1: Destination local,Router A,Example 2: Destination not local,Host Z,Broadcast,Host Z MAC ?,Host Z,Host Y MAC,Host Z MAC,Host Y,Query,Broadcast,Host Z MAC ?,Host Z,Response,Host Y MAC,Router A MAC,Routing Table: Net for Host Z,練習: MAC地址判定,Host A 0000.0c12.1111,Host B 0000.0c

4、12.2222,Host D 0000.0c12.4444,Router C 0000.0c12.3333,Router C 0000.0c12.5555,Network Y,Network X,局域網(wǎng)技術(shù),Copyright ?1998, Cisco Systems, Inc.,ICRC_revision_11.3,Ethernet Token Ring FDDI,LAN 技術(shù)概覽,FDDI Dual Ring,Ethernet和IEEE 802.3,Ethernet是一種共享介質(zhì)的技術(shù)，它允許多臺設(shè)備同時連接、交替使用同一傳輸介質(zhì)。,Ethernet/802.3的物理層,Host,10Ba

5、seT雙絞線,10Base2以太網(wǎng)細纜 10Base5以太網(wǎng)粗纜,PC,Mac,Sun,Host,Hub,MAC,Ethernet/802.3接口,Cisco路由器的Ethernet/802.3的接口名字使用字母E加一個數(shù)字(例如： E0),0800.2006.1a56,0000.0c12. 7c4d,E0,E1,0800.890c.34d5,0000.0c12. 83e2,Ethernet/802.3工作原理,A,B,C,D,Ethernet/802.3工作原理,A,B,C,D,Ethernet/802.3工作原理,A,B,C,D,D,Ethernet/802.3工作原理,A,B,C,D,D

6、,B and C,Ethernet/802.3 廣播,D,C,B,A,Application,Presentation,Session,Transport,Network,Data Link,Physical,A,B,C,D,Ethernet/802.3 的沖突檢測,Ethernet/802.3的沖突檢測,C,D,Ethernet/802.3的沖突檢測,C,D,Collision,Ethernet/802.3的沖突檢測,Collision,A,B,C,D,C,D,Ethernet/802.3的沖突檢測,A,B,C,D,Collision,A,B,C,D,JAM,JAM,JAM,JAM,JAM,

7、JAM,Ethernet/802.3的沖突檢測,A,B,C,D,Collision,A,B,C,D,JAM,JAM,JAM,JAM,JAM,JAM,廣域網(wǎng)技術(shù),Copyright ?1998, Cisco Systems, Inc.,ICRC_revision_11.3,WAN 技術(shù)概覽,SDLC,HDLC LAPB PPP,X.25 Frame Relay ISDN,WAN的物理層協(xié)議,(Modem),Data Terminal Equipment （與數(shù)據(jù)通信網(wǎng)相連的用戶設(shè)備）,DTE,Data Circuit-Terminating Equipment （數(shù)據(jù)通信網(wǎng)末端設(shè)備） CSU信道服務(wù)單元 DSU數(shù)據(jù)服務(wù)單元,DCE,EIA/TIA-232 V.35 X.21 HSSI Others,CSU/DSU,WAN接口電纜,Data Link Layer: WAN Protocols,SDLCSynchronous Data Link Control HDLCHigh-Level Data Link Control LAPBLink Access Procedure, Balanced Frame RelaySimplified v