Chabot College
ELEC 99.05
Ethernet & 802.3
CISCO NETWORKING ACADEMY
Network Technologies
A network technology is a “set of rules”
that describes Layer 1 & 2.
Network Layer
Data Link Layer
How do I access the
wire (media)?
Physical Layer
What kind of wire
(media) do I use?
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Common LAN technologies
Ethernet is the
simplest, cheapest,
and (therefore) most
popular LAN
technology.
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Ethernet and TCP/IP
Ethernet & TCP/IP are the most pervasive
LAN protocols, and are often used together.
Application Layer
Presentation Layer
Session Layer
TCP/IP
Transport Layer
Network Layer
Data Link Layer
Physical Layer
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Ethernet
Origins of Ethernet
• developed at Xerox Palo Alto
Research Center (PARC) in the early
1970s .
• first standardized in 1980 by Digital,
Intel, and Xerox (“DIX”).
– DIX Ethernet version 1.0 or,
– Ethernet I
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Origins of Ethernet
• DIX released their second and final
standard in 1982.
– DIX Ethernet Version 2.0 or,
– Ethernet II
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Meanwhile...
The IEEE maintains a committee that
is concerned with Networking
Standards.
The committee, made up of working
groups, is called 802.
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The Working Groups
802.1 Networking Overview and Architecture
802.2 Logical Link Control
802.3 Ethernet
802.4 Token Bus
802.5 Token Ring
802.6 MANs
802.7 Broadband
802.8 Fiber Optic
802.9 Isochronous LAN
...and more!
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The 802.3 Working Group
• released first standard in 1983
– 10Base5
• released thinnet standard in 1985
– 10Base2
• released twisted pair standard in 1990
– 10Base-T
– revolutionized networking
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The 802.3 Working Group
• released Fast Ethernet standard in
1995
– 100Base-X
• released full-duplex standard in 1997
– no collisions
• released Gigabit standard in 1998
– 1000Base-X
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Ethernet and 802.3
• Ethernet and 802.3 are often thought
of as the same thing.
• Technically, they aren’t.
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Ethernet & 802.3 Similarities
• At Layer 2, both standards describe:
– CSMA/CD Media Access Method
– logical “bus” topology
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Ethernet & 802.3 Similarities
• At the physical layer, both standards
allow:
– coaxial cable
– physical “bus” topology
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Ethernet & 802.3 Differences
• 802.3 not only specifies coaxial cable,
but twisted pair and fiber as well.
• 802.3 also specifies physical star
topology.
• IEEE Layer-1 specs, include:
–
–
–
–
10Base-T (twisted pair, physical star)
10Base2 (thinnet coax, physical bus)
10Base5 (thicknet coax, physical bus)
10Base-F (fiber, physical bus)
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Ethernet & 802.3 Differences
• At Layer 2, these standards describe
different ways of organizing the frame
header:
Ethernet II (DIX standard)
64 bits
Preamble
48 bits
DA
48 bits
SA
16 bits
Type
Ethernet 802.3 frame with LLC
64 bits
Preamble
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48 bits
DA
48 bits
SA
16 bits
Length
Ethernet & 802.3 Compared
• Ethernet II (DIX Ethernet)
– old spec
– CSMA/CD, simple frame format
– coax bus only
• 802.3
–
–
–
–
constant new specs
CSMA/CD, more complex frame format
coax, fiber, twisted pair
star and bus
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The Last Word
• Most of the time, the term “Ethernet” is
used to mean IEEE 802.3
• For the most part, Ethernet and 802.3
are used interchangeably, even though
they are not really the same thing.
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