计算机网络英文教材第四章(精品·公开课件).ppt

Review Chapter 4. The Medium Access Control Sublayer Chapter 4. The Medium Access Control Sublayer Chapter 4. The Medium Access Control Sublayer 4.1 The Channel Allocation Problem 4.2 Multiple Access Protocols 4.2.1 ALOHA 4.2.1 ALOHA 纯ALOHA冲突重发 4.2.1 ALOHA 4.2.1 ALOHA: slotted ALOHA 4.2.2 Carrier Sense Multiple Access Protocols Persistent and Nonpersistent CSMA CSMA with Collision Detection CSMA with Collision Detection 4.2.6 Wireless LAN Protocols 4.2.6 Wireless LAN Protocols 4.2.6 Wireless LAN Protocols 4.3 Ethernet 4.3 Ethernet 4.3.1 Ethernet Cabling 4.3.2 Manchester Encoding 4.3.3 The Ethernet MAC Sublayer Protocol 4.3.3 The Ethernet MAC Sublayer Protocol 为什么要限制最小帧的长度？ For a 10-Mbps LAN with a maximum length of 2500 meters and four repeaters (from the 802.3 specification), the round-trip time (including time to propagate through the four repeaters) has been determined to be nearly 50 μsec in the worst case, including the time to pass through the repeaters, which is most certainly not zero. Therefore, the minimum frame must take at least this long to transmit. At 10 Mbps, a bit takes 100 nsec, so 500 bits is the smallest frame that is guaranteed to work. To add some margin of safety, this number was rounded up to 512 bits or 64 bytes. Frames with fewer than 64 bytes are padded out to 64 bytes with the Pad field. 4.3.4 The Binary Exponential Backoff Algorithm CSMA/CD流程 4.3.6 Switched Ethernet 4.3.7 Fast Ethernet 4.3.7 Fast Ethernet 4.3.7 Fast Ethernet 4.3.8 Gigabit Ethernet 4.3.8 Gigabit Ethernet 4.3.8 Gigabit Ethernet 4.3.9 IEEE 802.2: Logical Link Control 4.4 Wireless LANs 4.4.1 The 802.11 Protocol Stack 4.4.2 The 802.11 Physical Layer 4.4.2 The 802.11 Physical Layer 4.4.3 The 802.11 MAC Sublayer Protocol 4.4.3 The 802.11 MAC Sublayer Protocol 4.4.3 The 802.11 MAC Sublayer Protocol 4.4.3 The 802.11 MAC Sublayer Protocol 4.4.4 The 802.11 Frame Structure 4.4.4 The 802.11 Frame Structure 4.4.4 The 802.11 Frame Structure 无线局域网连接方案 （一）独立无线局域网方案 1.无接入点独立对