Chapter 5_ part2-2008 - PART 2: 5.3: WIRED LANS 1 5.3 WIRED...

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1 PART 2: PART 2: 5.3: WIRED LANS 5.3: WIRED LANS
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2 5.3 WIRED LANS: ETHERNET In 1985, the Computer Society of the IEEE In 1985, the Computer Society of the IEEE started a project, called Project 802, to set started a project, called Project 802, to set standards to enable intercommunication among standards to enable intercommunication among equipment from a variety of manufacturers. equipment from a variety of manufacturers. Project 802 is a way of specifying functions of Project 802 is a way of specifying functions of the physical layer and the data link layer of the physical layer and the data link layer of major LAN protocols. major LAN protocols.
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3 The original Ethernet was created in 1976 at Xerox’s Palo Alto Research Center (PARC). Since then, it has gone through four generations. Ethernet evolution through four generations
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4 802.3 MAC frame Preamble DA SA Length/ Type LLC data FCS S F D P a d 7 octets 1 6 6 2 ³ 0 ³ 0 4 46 to 1500 octets Preamble A 7-octet pattern of 10101010 for bit synchronization SFD [Start frame delimiter ] The sequence 10101011, indicating the start of the frame  DA [Destination address] Destination MAC address SA [Source address] Source MAC address Length/Type Length of LLC data field in octets, the maximum frame size,  excluding the Preamble and SFD, is 1518 octets LLC data Data unit supplied by LLC Pad Octets added to ensure that the frame is long enough for proper  CD operation FCS [Frame check sequence] A 32-bit cyclic redundancy check, based on all fields excepts  preamble, SFD and FCS
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5 Example of an Ethernet address in hexadecimal notation MAC address global address assigned centrally by IEEE to ensure that no two stations anyway in the world have the same global address Vendor code=24 Serial number=24
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Unicast and multicast addresses The least significant bit of the first byte defines the type of address. If the bit is
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Chapter 5_ part2-2008 - PART 2: 5.3: WIRED LANS 1 5.3 WIRED...

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