Chapter 3: IEEE Specifications and Their Characteristics
Chapter Outline
1. On the Test
a. Specify the main features of 802.2 (Logical Link Control), 802.3 (Ethernet), 802.5 (token ring), 802.11b
(wireless), and FDDI network technologies, including: speed, access, method, topology, media.
2. Understanding Project 802 Standards
a. Project 802 addresses aspects of networking technology.
b. Whenever a new technology, such as wireless communications, is introduced, a committee is formed to
investigate and make recommendations on that technology.
c. Their results are often published as standards.
d. These standards are written to address how networking should occur between devices that are using that
particular technology.
3. A Brief Introduction to the OSI Model
a. The OSI Model provides a framework for the rules that network devices will use to talk with each other.
b. There are seven layers to the OSI Model.
c. This chapter focuses only on the Data Link Layer.
4. 802.2: Logical Link Control (LLC)
a. The Data Link layer of the OSI Model is divided into two separate sublayers:
i. Media Access Control (MAC) layer
ii. Logical Link Control (LLC) layer. The LLC acts as an interface between the MAC sublayer and
the Network layer by managing the frames.
b. The 802.2 standard defines how network communications should take place within the LLC sublayer.
c. The LLC communicates upward to the Network layer using either connectionless or connection-oriented
modes.
i. Connectionless mode: The LLC simply sends out packets of information. There is no error
checking or controls so communication tends to be fast. It is also known as a Type 1 operation.
ii. Connection-oriented mode: The receiving node sends a message to the sending node,
acknowledging that it received the information. This mode is slower but more reliable. It is also
known as Type 2 Operation.
d. The LLC also monitors the flow of data between nodes and conducts error checking through the use of
cyclical redundancy checks (CRC).
5. 802.3: Carrier Sense Multiple Access with Collision Detection (CSMA/CD)
a. Defines Ethernet networking standards
b. Also called the “DIX” standard
c. Provides rules concerning how stations communicate while sharing a common cabling system
d. Uses a bus topology
e. Uses the following media:
i. Thinnet (10Base2): Thinnet coaxial cable can support data transfer speeds of 10Mbps. Thinnet
segments are limited to 185 meters (approximately 607 feet). If additional length is needed, a
repeater is required.
ii. Thicknet (10Base5): Thicknet coaxial cable can support data transfer speeds of 10Mbps.
Thicknet segments can extend 500 meters (approximately 1,640 feet). If additional length is
needed, a repeater is required.
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iii. Twisted pair wiring (10BaseT): Shielded or unshielded twisted pair cable (STP or UTP) supports
a data transfer rate up to 100Mbps. The segment between network devices (when wired as a star)
can extend 100 meters (approximately 328 feet).
6. 802.5: Token Ring
a. Token Ring or token passing networks use a token that travels around the ring, from computer to
computer.
b. Since there is only one token, there are no collisions.
c. Uses a ring topology
d. Supports a data transfer rate up to 16Mbps
e. Commonly uses UTP, STP, or fiber-optic cable
7. Fiber Optic (FDDI) LANS and MANS
a. A type of token-passing technology.
b. A pair of fiber optic rings connects each device. Each ring contains a single token and the tokens travel
in opposite directions between the devices.
c. If a break or other problem occurs in the primary ring, the secondary ring acts as a backup, assuring that
data continues to move on the network.
d. Since FDDI networks are fault tolerant and support high data transmission speeds, they are commonly
used as network backbones.
e. Uses single-mode or multimode fiber-optic cabling.
f. Supports speed up to 100Mbps
g. Can extend to distances up to 60 miles
h. Much more expensive to implement than wire-(UTP/STP/Coaxial) based networks.
i. Development of 100BaseTX Ethernet is taking the place of FDDI.
8. 802.11: Wireless LANS
a. Provides network access for computing devices without regard for where they are physically located.
b. Devices use radio waves rather than network cabling.
c. The 802.11 standard addresses transmission requirements at both the Physical and MAC layers of the
OSI Model.
d. The Physical layer handles the actual data transmission duties between devices.
e. The MAC layer controls the network access method.
f. Use the Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA) access method.
g. The 802.11b standard boosted wireless network speeds to 11Mbps.
h. 802.11g raises transmission rates to 54Mbps provided short distances are used.
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