System information

Ethernet and IEEE 802.3
Book Title
4-58
Physical Connections
IEEE 802.3 specifies several different physical layers, whereas Ethernet defines only one. Each
IEEE 802.3 physical layer protocol has a name that summarizes its characteristics. The coded
components of an IEEE 802.3 physical-layer name are shown in Figure 4-1.
Figure 4-1 IEEE 802.3 Physical Layer Name Components
A summary of Ethernet Version 2 and IEEE 802.3 characteristics appears in Table 4-1.
Table 4-1 Ethernet Version 2 and IEEE 802.3 Physical Characteristics
Ethernet is most similar to IEEE 802.3 10Base5. Both of these protocols specify a bus topology
network with a connecting cable between the end stations and the actual network medium. In the
case of Ethernet, that cable is called a transceiver cable. The transceiver cable connects to a
transceiver device attached to the physical network medium. The IEEE 802.3 configuration is much
the same, except that the connecting cable is referred to as an attachment unit interface (AUI), and
the transceiver is called a media attachment unit (MAU). In both cases, the connecting cable attaches
to an interface board (or interface circuitry) within the end station.
Frame Formats
Ethernet and IEEE 802.3 frame formats are shown in Figure 4-2.
Characteristic
Ethernet
Value IEEE 802.3 Values
10Base5 10Base2 1Base5 10BaseT 10Broad36
Data rate
(Mbps)
10 10 10 1 10 10
Signaling
method
Baseband Baseband Baseband Baseband Baseband Broadband
Maximum
segment
length (m)
500 500 185 250 100 1800
Media 50-ohm
coax (thick)
50-ohm
coax (thick)
50-ohm
coax (thin)
Unshielded
twisted-pair
wire
Unshielded
twisted-pair
wire
75-ohm
coax
Topology Bus Bus Bus Star Star Bus
10 Base 5
“Base” = baseband
“Broad” = broadband
LAN speed in Mbps LAN segment length,
in 100-meter multiples