Chapter 13
Wired LANs: Ethernet
IEEE Project 802
- In 1985, the IEEE started a project, called
Project 802, to set standards to enable
intercommunication among equipment from a
variety of manufacturers.
- It is a way of specifying functions of the
physical layer and the data-link layer of major
LAN protocols.
13.2
IEEE standard for LANs
13.3
Ethernet Evolution
- The Ethernet LAN was developed in the 1970s.
- Since then, it has gone through four generations:
Standard Ethernet (10 Mbps)
Fast Ethernet (100 Mbps)
Gigabit Ethernet (1 Gbps, 10 Gbps)
13.4
Ethernet frame
13.5
Example 13.1
Show how the address 47:20:1B:2E:08:EE is sent out
online.
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:
13.6
Addressing
- Each station on an Ethernet network (such as a
PC, workstation, or printer) has its own
network interface card (NIC).
- The NIC fits inside the station and provides the
station with a link-layer address.
- The Ethernet address is 6 bytes (48 bits),
normally written in hexadecimal notation, with
a colon between the bytes. For example, the
following shows an Ethernet MAC address:
13.7
Unicast and multicast addresses
13.8
Example 13.2
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 Fs, the address is broadcast.
13.9
Example 13.2 (continued)
a. This is a unicast address because A in binary is 1010
(even).
b. This is a multicast address because 7 in binary is 0111
(odd).
c. This is a broadcast address because all digits are Fs in
hexadecimal.
13.10
Implementation of standard Ethernet
13.11
Access Method
- Since the network that uses the standard
Ethernet protocol is a broadcast network
- We need to use an access method to control
access to the sharing medium.
- The standard Ethernet chose CSMA/CD with
1-persistent method,
13.12
Summary of Standard Ethernet implementations
13.13
Encoding in a Standard Ethernet
13.14
10Base5 implementation
13.15
10Base2 implementation
13.16
10Base-T implementation
13.17
10Base-F implementation
13.18
Changes in the Standard
Before we discuss higher-rate Ethernet protocols,
we need to discuss the changes that occurred to the
10-Mbps Standard Ethernet. These changes
actually opened the road to the evolution of the
Ethernet to become compatible with other high-
data-rate LANs.
13.19
Sharing bandwidth
13.20
A network with and without bridging
13.21
Collision domains
13.22
Switched Ethernet
13.23
Full – duplex switched Ethernet
13.24
FAST ETHERNET
- In the 1990s, Ethernet made a big jump by
increasing the transmission rate to 100 Mbps,
and the new generation was called the Fast
Ethernet.
- The designers of the Fast Ethernet needed to
make it compatible with the Standard Ethernet.
- The MAC sublayer was left unchanged. But the
features of the Standard Ethernet that depend
on the transmission rate, had to be changed.
13.25
Access Method
- The proper operation of the CSMA/CD
depends on the transmission rate, the minimum
size of the frame, and the maximum network
length.
- If we want to keep the minimum size of the
frame, the maximum length of the network
should be changed.
- In other words, if the minimum frame size is
still 512 bits, and it is transmitted 10 times
faster, the collision needs to be detected 10
times sooner, which means the maximum length
of the network should be 10 times shorter (the
propagation speed does not change).
13.26
Physical Layer
To be able to handle a 100 Mbps data rate, several
changes need to be made at the physical layer.
13.27
Encoding for fast Ethernet
13.28
Summary of Fast Ethernet implementations
13.29
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 it the Standard
802.3z.
- The goals of the Gigabit Ethernet were to
upgrade the data rate to 1 Gbps, but keep the
address length, the frame format, and the
maximum and minimum frame length the same.
13.30
MAC Sublayer
- A main consideration in the evolution of
Ethernet was to keep the MAC sublayer
untouched.
- However, to achieve a data rate of 1 Gbps, this
was no longer possible.
- Gigabit Ethernet has two distinctive
approaches for medium access: half-duplex and
full-duplex. Almost all implementations of
Gigabit Ethernet follow the full-duplex
approach, so we mostly ignore the half-duplex
mode.
13.31
Physical Layer
The physical layer in Gigabit Ethernet is more
complicated than that in Standard or Fast
Ethernet.
13.32
Encoding in Gigabit Ethernet
13.33
Summary of Gigabit Ethernet implementations
13.34
10-GIGABIT EHTERNET
- The Ethernet for use in metropolitan areas.
- The idea is to extend the technology, the data
rate, and the coverage distance so that the
Ethernet can be used as LAN and MAN
(metropolitan area network).
- The IEEE committee created 10 Gigabit
Ethernet and called it Standard 802.3ae.
13.35
Implementation
- 10 Gigabit Ethernet operates only in full-duplex
mode, which means there is no need for
contention;
- CSMA/CD is not used in 10 Gigabit Ethernet.
- Four implementations are the most common:
10GBase-SR, 10GBase-LR, 10GBase-EW, and
10GBase-X4.
13.36
Summary of 10-Gigabit Ethernet implementations
13.37
