Specifications

Introduction 2-3
Ethernet Features
Transmission Medium
Ethernet transmits data frames over a physical medium of coaxial, fiber
optic, or twisted pair cable. The coaxial and fiber optic cable typically
represents the backbone of an Ethernet LAN while twisted pair is used as
a low cost connection from the backbone to the desktop.
Ethernet LANs have the following media restrictions in order to adhere to
IEEE standards:
• Bus Length: The maximum bus length for an Ethernet LAN for all
media types is the following:
- 500 m for 10BASE5 coaxial cable
- 185 m for 10BASE2 coaxial cable
- 2,000 m for multimode fiber optic (10BASE-F) cable (5,000 m for
single mode)
- 100 m for twisted pair (10BASE-T) cable.
• AUI Length: The maximum Attachment Unit Interface (AUI) cable
length is 50 m for connections from a transceiver to an Ethernet device
and 16.5 m for office AUI.
• Number of Stations per Network: IEEE standards specify that the
maximum allowable number of stations per un-bridged network is
1,024, regardless of media type. 10BASE5 networks are allowed 100
taps per segment while 10BASE2 networks are allowed 30 taps per
segment with a maximum of 64 devices per tap each (Fiber optic and
twisted pair cable are point-to-point media which do not allow taps or
branches).
• Maximum Signal Path: The maximum allowable signal path is 4
repeaters, 5 segments (with at least 2 segments being unpopulated
Inter-Repeater Links), and 7 bridges for all media types.
These media lengths are not precise values. Actual maximum cable
lengths are strongly dependent on the physical cable characteristics.
NOTE
If it becomes necessary to extend the network beyond the IEEE limit of
1,024 devices, a bridge can be used to connect another full specification
Ethernet network.
NOTE