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Chapter 13
Wired LANs: Ethernet

13.1 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

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.

Topics discussed in this section:
Data Link Layer
Physical Layer

13.2

Figure 13.1 IEEE standard for LANs

13.3

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

13.4

Figure 13.3 Ethernet evolution through four generations

13.5

Figure 13.4 802.3 MAC frame

13.6

Figure 13.5 Minimum and maximum lengths

13.7

Note

Frame length:
Minimum: 64 bytes (512 bits)
Maximum: 1518 bytes (12,144 bits)

13.8

Figure 13.6 Example of an Ethernet address in hexadecimal notation

13.9

Figure 13.7 Unicast and multicast addresses

13.10

Note

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.

13.11

Note

The broadcast destination address is a
special case of the multicast address in
which all bits are 1s.

13.12

Example 13.1

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 binary is 1010.
b. This is a multicast address because 7 in binary is 0111.
c. This is a broadcast address because all digits are F’s.
13.13

Example 13.2

Show how the address 47:20:1B:2E:08:EE is sent out on
line.

Solution
The address is sent left-to-right, byte by byte; for each
byte, it is sent right-to-left, bit by bit, as shown below:

13.14

Figure 13.8 Categories of Standard Ethernet

13.15

Figure 13.9 Encoding in a Standard Ethernet implementation

13.16

Figure 13.10 10Base5 implementation

13.17

Figure 13.11 10Base2 implementation

13.18

13-4 FAST ETHERNET

Fast Ethernet was designed to compete with LAN
protocols such as FDDI or Fiber Channel. IEEE
created Fast Ethernet under the name 802.3u. Fast
Ethernet is backward-compatible with Standard
Ethernet, but it can transmit data 10 times faster at a
rate of 100 Mbps.

MAC Sublayer
Physical Layer

13.19

13-5 GIGABIT ETHERNET

The need for an even higher data rate resulted in the
design of the Gigabit Ethernet protocol (1000 Mbps).
The IEEE committee calls the standard 802.3z.

MAC Sublayer
Physical Layer
Ten-Gigabit Ethernet

13.20

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