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第 4 章 局域网. 基本内容 介绍局域网的基本概念、拓朴结构、常用的局域网传输媒体,局域网的共享媒体技术,传统以太网的工作原理及连接方法、 CSMA/CD 协议、碰撞退避算法、 MAC 地址、 MAC 帧,局域网的扩展,高速以太网技术。 重点掌握 局域网的拓朴结构 以太网的工作原理、 CSMA/CD 协议、 MAC 帧 以太网的连接方法 局域网的扩展技术 高速以太网技术. 4.1 局域网概述. - PowerPoint PPT Presentation
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4 CSMA/CDMACMAC CSMA/CDMAC
4.1 (LAN) ()
Topology
1-,
2,
3()
4.2 10Mbps100Mbps1Gbps10Gbps 4.2.1 4.2.2 4.2.3
4.2.1 1. DIX Ethernet V2 IEEE 802.3 DIX Ethernet V2 IEEE 802.3 802.3 DIX Ethernet V2
802 LLC (Logical Link Control) MAC (Medium Access Control) TCP/IP DIX Ethernet V2 802.3 802 LLC 802.2
4.2.1 2. (adapter) NIC (Network Interface Card) / IP
CPUI/O
4.2.1 3. CSMA/CD B D C D A EB D B
B D D A, C E
4.2.1 CSMA/CDCarrier Sense Multiple Access with Collision Detection /
A B B B A B ( B A ) A
AB1km1km5 s
4.2.1 4. 2 2
2 k k 10 k = Min[, 10] [0,1,, (2k 1)] r r 16
51.2 s 10 Mb/s 512 bit 64 64
64 64 64 64
ABt
4.2.2
BNC T MAUMDIDB-15BNC RJ-45
250 m750 m 1 2 3
1RJ-45EthernetPROM 2Hub8101224310BASE2RJ-45
RJ45RJ45
10BASE2 5 mm ( 50 W) MAU MDI AUI BNC T BNC
10BASE2BNCBNC
CSMA/CD
10BASE-T (hub)100
CSMA/CD
4.2.3 N p 2 L (bit) C (b/s) L/C = T0 (s)
4.2.3 Smax
N a a Smax
a =1 ABABt = T0ABABt = 3T0t = 4T0t = 2T0ABt = 5T0 a = 4
a = 0.01 a = 0.01 ABABt = t = 0.5ABt = 100ABt = 100.5
4.3 MACIEEE802
MAC MACLLC MAC LLC()
4.3.1 MAC MACROM648 IEEE63125024224=16777216
100110101 01111011 00010010 00000000 00000000 00000001 OUI EUI-48 AC-DE-48-00-00-80 EUI-48 1 6 I/G I/G 2 3 4 5 6 1 2 3 4 5 610101100 11011110 01001000 00000000 00000000 10000000802.5802.6802.3802.4
1A-24-F6-54-1B-0E00-00-A2-A4-2C-0220-60-8C-C7-75-2A08-00-20-47-1F-E420-60-8C-11-D2-F6
MAC MAC MAC MAC . unicast broadcast multicast
4.3.2 MAC MAC DIX Ethernet V2 IEEE 802.3 MAC V2
V2 MAC MAC MAC IP 6 6
V2 MAC MAC MAC IP 2 MAC
V2 MAC MAC MAC IP = 64 18 46 MAC 64 46 ~ 1500 FCS 4
V2 MAC MAC MAC IP 8 7 MAC MAC
MAC FCS 46 ~ 1500 MAC 64 ~ 1518 MAC
9.6 s 96 bit 9.6 s
4.4
4.4.2 MAC MAC
1 2 B A1112MAC1MAC3MAC52MAC2MAC42MAC6AB
MAC 10 Mb/s 100 Mb/s
MAC MACMAC ()
Bridge MAC Bridge Bridge MAC
IPMAC 1IPMAC 2 1 2ABIP-HMAC-HMAC-TDL-HDL-T DLRMACDLRLANLAN
CSMA/CD
(transparent bridge)
(1) x () MAC (2) MAC d(3)(5)(3) MAC d = x() d (4) (6)(5) x (6) MAC (8)(7)(7) (8) (1)
B1B2LAN1LAN2LAN3LAN4 AB AH HLAN3AH B1B2 AH
LANLANLAN
MAC MAC MAC MAC x A x A
() ()
ABCDEFHIJG123456789123456789ABCDEFHJLanBridge
(source route)
LANLAN1LAN1241
1990 (switching hub)(switch)
132456
10 Mb/s N (10 Mb/s) N 10 Mb/s N N10 Mb/s
10BASE-T100 Mb/s100 Mb/s100 Mb/s
8881818881887
!MACMAC
4.5 VLAN VLAN VLAN
A4B1VLAN3C3B3VLAN1VLAN2C1A2A1A3C2B2 VLAN1, VLAN2 VLAN3
A4B1VLAN3C3B3VLAN1VLAN2C1A2A1A3C2B2 B1 VLAN2 B2 B3
A4B1VLAN3C3B3VLAN1VLAN2C1A2A1A3C2B2B1 A1, A2 C1 B1 ()
4 VLAN (tag) 802.3MAC 66246 ~ 15004/ FCS/ = 802.1Q 1 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0 VID 2 2 4 VLAN 4CFI
4.6.1 100BASE-T 10BASE-T100BASE-T100BASE-T100Mb/s 100Mb/s10BASE-T100BASE-TMACIEEE802.3 CSMA/CDCSMA/CD
4.6.1 100BASE-T 100BASE-T CSMA/CD MAC 802.3 100 m 9.6 s 0.96 s
4.6.1 100BASE-T IEEE802.3u1100BASE-TX2UTP5STP2100BASE-FX23100BASE-T44UTP35
4.6.2 1 Gb/s 802.3 CSMA/CD CSMA/CD 10BASE-T 100BASE-T
4.6.2 11000BASE-X802.3z) 1000BASE-SX SX 1000BASE-LX LX 1000BASE-CX CX21000BASE-T 802.3ab) 4 5 UTP
(carrier extension) a a = C/L 100 m 64 512
MAC MAC 512 MAC 512 MAC FCSMAC = 64 MAC = 512
1500 #1 RRRRRRRR #2 RRRR #3 RRR #4 512 1500
1 Gb/s 100 Mb/s
4.6.3 10 MAC
4.6.3 10 10 10 Mb/s100 Mb/s 1 Gb/s 10 802.3 10 10 CSMA/CD
LAN PHY 10.000 Gb/s 10Gbps802.3MAC101G10Gbps10Gbps10/100/1000Mbps
WAN PHY9.95328Gb/s9.58464Gb/s 10GOC-19210GMAC Gb/s SONET/SDHOC-192/STM-64 10 OC-192/STM-64 9.95328 Gb/s
4.7 100VG-AnyLAN VGAny 100 Mb/s MAC
4.7 FDDI IEEE 802.5MAC100 Mb/s10002 km()100 km200 km4500
4.7 ABDCABDCFDDI
4.8 4.8.1 4.8.2 802.11 4.8.3 802.11 MAC
4.8.1 BSS ESS BSSAB AP AP DS
802.x
BSS BSS BSS BSS AP AP DS ESS ESS 802.11 A B
AP AEDCBF
4.8.2 802.11 802.11 FHSS DSSS IR 802.11a 5 GHz OFDM 6, 9, 12, 18, 24, 36, 48 56 Mb/s 802.11b 2.4 GHz 5.5 11 Mb/s
4.8.3 802.11 MAC CSMA/CD CSMA/CD
1ABCD A C B B
2 B A C D C D B A C D ADCB
CSMA/CA CSMA/CD CSMA CSMA Collision Avoidance 802.11 CSMA/CA CSMA/CA
802.11 MAC MAC BSS MAC DCF(Distributed Coordination Function)(CSMA/CA) PCF(Point Coordination Function)802.11b802.11aIEEE 802.11
802.11 MAC 802.11 MAC DCF CSMA PCF
IFS IFS (InterFrame Space)
SIFS(Short) 28 s SIFS ACK CTS MAC AP PCF AP
PIFS SIFS PCF PCF PIFS SIFS (slot) 50 s78 s
DIFS IFS DCF DIFS PIFS DIFS 128 s
SIFSPIFSDIFS 1 SIFSPIFSNAVDIFS ACKSIFS
CSMA/CA 802.11 MAC DIFS SIFS ACK ACK
(Virtual Carrier Sense) MAC
MAC NAV (Network Allocation Vector) NAV
DIFS 802.11
i 22 + i 1 8 ( 2 ) 2 16 ( 4 )
ACBDE A RTS (Request To Send)
CTSACBDECTS B CTS (Clear To Send) RTS CTS A CTS
ACBDECABCARTSCBCTSABCB
CTSACBDECTSDDARTSBCTSDBADABBAERTSCTSEDABE
BCARTSARTSACTSBCRTS
RTS CTS ACK DIFSRTSSIFSNAVRTSDIFSACK CTSSIFSSIFSNAVCTSNAV
P135 4-124-23