SYSTEM ADMINISTRATION
Chapter 3
IEEE Specifications and their
Characteristics
Understanding Project 802
Standards
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Project 802 addresses aspects of networking
technology.
Whenever a new technology, such as wireless
communications, is introduced, a committee is
formed to investigate and make recommendations
on that technology.
Their results are often published as standards.
These standards are written to address how
networking should occur between devices that are
using that particular technology.
A Brief Introduction to the OSI
Model
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The OSI Model provides a framework for the rules
that network devices will use to talk with each
other.
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There are seven layers to the OSI Model.
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This chapter is concerned only with the Data Link
layer.
802.2: Logical Link Control
• The Data Link layer of the OSI Model is divided into
two separate sublayers:
–Media Access Control (MAC) layer
–Logical Link Control (LLC) layer.
• The 802.2 standard defines how network
communications should take place within the LLC
sublayer.
• The LLC communicates upward to the Network layer
using either connectionless or connection-oriented
modes.
• The LLC also monitors the flow of data between
nodes and conducts error checking through the use
of cyclical redundancy checks (CRC).
802.3: Carrier Sense Multiple
Access with Collision Detection
(CSMA/CD)
• Defines Ethernet networking standards.
• Also called the “DIX” standard.
• Provides rules concerning how stations
communicate while sharing a common cabling
system.
• Uses a bus topology.
(continued)
CSMA/CD
(continued)
Uses the following media:
• Thinnet (10Base2):
– Support data transfer speeds of 10 Mbps.
– Segments are limited to 185 meters (approximately 607
feet). If additional length is needed, a repeater is required.
• Thicknet (10Base5):
– Supports data transfer speeds of 10 Mbps.
– Segments can extend 500 meters (approximately 1,640
feet). If additional length is needed, a repeater is required.
• Twisted pair wiring (10BaseT):
– Shielded or unshielded twisted pair cable (STP or UTP).
– Supports a data transfer rate up to 100 Mbps.
– Segment between network devices (when wired as a star)
can extend 100 meters (approximately 328 feet).
802.5: Token Ring
• Token Ring or token passing networks use a token
that travels around the ring, from computer to
computer.
• Since there is only one token, there are no
collisions.
• Uses a ring topology.
• Supports a data transfer rate up to 16 Mbps.
• Commonly uses UTP, STP or fiber-optic cable.
802.11: Wireless LANS
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Provide network access for computing devices
without regard for where they are physically
located.
Devices use radio waves rather than network
cabling.
The 802.11 standard addresses transmission
requirements at both the Physical and Media
Access Control layers of the OSI Model.
The Physical layer handles the actual data
transmission duties between devices.
(continued)
802.11: Wireless LANS
(continued)
• The Media Access Control layer controls the
network access method.
• Use the Carrier Sense Multiple Access with
Collision Avoidance (CSMA/CA) access method.
• The 802.11b standard boosted wireless network
speeds to 11Mbps.
• 802.11g raises transmission rates to 54 Mbps
provided short distances are used.