This chapter devoted to access control, the duties of the data link layer that are related to the use of the physical layer. The main contents of this chapter include all of the following: Random access, controlled access, channelization. | Chapter 13 Wired LANs: Ethernet Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 13. 13-1 IEEE STANDARDS In 1985, the Computer Society of the IEEE started a project, called Project 802, to set standards to enable intercommunication among equipment from a variety of manufacturers. Project 802 is a way of specifying functions of the physical layer and the data link layer of major LAN protocols. Data Link Layer Physical Layer Topics discussed in this section: 13. Figure IEEE standard for LANs 13. Figure HDLC frame compared with LLC and MAC frames 13. 13-2 STANDARD ETHERNET The original Ethernet was created in 1976 at Xerox’s Palo Alto Research Center (PARC). Since then, it has gone through four generations. We briefly discuss the Standard (or traditional) Ethernet in this section. MAC Sublayer Physical Layer Topics discussed in this section: 13. Figure Ethernet evolution through four generations 13. Figure MAC frame 13. Figure Minimum and maximum lengths 13. Frame length: Minimum: 64 bytes (512 bits) Maximum: 1518 bytes (12,144 bits) Note 13. Figure Example of an Ethernet address in hexadecimal notation 13. Figure Unicast and multicast addresses 13. The least significant bit of the first byte defines the type of address. If the bit is 0, the address is unicast; otherwise, it is multicast. Note 13. The broadcast destination address is a special case of the multicast address in which all bits are 1s. Note 13. Define the type of the following destination addresses: a. 4A:30:10:21:10:1A b. 47:20:1B:2E:08:EE c. FF:FF:FF:FF:FF:FF Solution To find the type of the address, we need to look at the second hexadecimal digit from the left. If it is even, the address is unicast. If it is odd, the address is multicast. If all digits are F’s, the address is broadcast. Therefore, we have the following: a. This is a unicast address because A in . | Chapter 13 Wired LANs: Ethernet Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 13. 13-1 IEEE STANDARDS In 1985, the Computer Society of the IEEE started a project, called Project 802, to set standards to enable intercommunication among equipment from a variety of manufacturers. Project 802 is a way of specifying functions of the physical layer and the data link layer of major LAN protocols. Data Link Layer Physical Layer Topics discussed in this section: 13. Figure IEEE standard for LANs 13. Figure HDLC frame compared with LLC and MAC frames 13. 13-2 STANDARD ETHERNET The original Ethernet was created in 1976 at Xerox’s Palo Alto Research Center (PARC). Since then, it has gone through four generations. We briefly discuss the Standard (or traditional) Ethernet in this section. MAC Sublayer Physical Layer Topics discussed in this section: 13. Figure Ethernet evolution through four generations 13. .
