The Background of IEEE Ethernet

The Background of IEEE Ethernet
In 1980, the Digital Equipment Corporation, Intel, and Xerox (DIX) consortium created the
original Ethernet. Predictably, Ethernet_II followed and was released in 1984. The standardssetting
organization, the Institute of Electrical and Electronics Engineers (IEEE), termed this the
802.
x
project. The 802.
x
project was initially divided into three groups:

The High Level Interface (HILI) group became the 802.1 committee and was responsible
for high-level internetworking protocols and management.

The Logical Link Control (LLC) group became the 802.2 committee and focused on endto-
end link connectivity and the interface between the higher layers and the medium-accessdependent
layers.

The Data Link and Medium Access Control (DLMAC) group became responsible for the
medium-access protocols. The DLMAC ended up splitting into three committees:

802.3 for Ethernet

802.4 for Token Bus

802.5 for Token Ring
DEC, Intel, and Xerox pushed Ethernet, while Burroughs, Concord Data Systems,
Honeywell, Western Digital—and later, General Motors and Boeing—pushed 802.4. IBM
took on 802.5.
The IEEE then created the 802.3 subcommittee, which came up with an Ethernet standard
that happens to be almost identical to the earlier Ethernet_II version of the protocol. The two
differ only in their descriptions of the Data Link layer. Ethernet_II has a Type field, whereas
802.3 has a Length field. Even so, they’re both common in their Physical layer specifications,
MAC addressing, and understanding of the LLC layer’s responsibilities.
See
CCNA: Cisco Certified Network Associate Study Guide,
4th edition
, by
Todd Lammle (Sybex, 2004) for a detailed explanation of Ethernet frame types.
Ethernet_II and 802.3 both define a bus-topology LAN at 10Mbps, and the cabling defined
in these standards is identical:
10Base2/Thinnet
Segments up to 185 meters using RG58 coax at 50 ohms.
10Base5/Thicknet
Segments up to 500 meters using RG8 or RG11 at 50 ohms.
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Chapter 13 
Connecting the Switch Block
10BaseT/UTP
All hosts connect by using unshielded twisted-pair (UTP) cable with a central
device (a hub or switch). Category 3 UTP is specified to support up to 10Mbps, Category 5 to
100Mbps, Category 5e to 1000Mbps, and Category 6 to 1000Mbps.
Category 5e and Category 6 cables are relatively new. While both are
designed to support data running at up to 1000 Mbits/second, the quality
of the cables differs in that Category 5e still has performance specified at
100MHz and Category 6 has the performance specified at speeds of up to
250MHz. Category 6, if installed to the correct standard, provides better
quality signal transfer.