Page 65 - M. Abrahim Thesis

Computer Network 2021

The primary advantage and disadvantage comparison categories are as follows:

• Cable length

• Cost

• Ease of installation Coaxial cable, optical fiber, and even free space can carry network
signals.
However, the principal medium that is studied is called Category 5 unshielded
twistedpair cable (CAT 5 UTP)
https://www.youtube.com/watch?v=a5SMTyhn0U8 .

3.7 Ethernet Fundamentals

Ethernet, in its various forms, is the most widely used local-area network (LAN)
technology. Ethernet was designed to fill the middle ground between long-distance, low-speed
networks and specialized, computer-room networks carrying data at high speeds for very limited
distance. Ethernet is well suited to applications in which a local communication medium must
carry sporadic, occasionally heavy traffic at high-pack data rates. It was designed to enable
sharing resources on a local workgroup level. Design goals include simplicity, low cost,
compatibility, fairness, low delay, and high speed. In this chapter, you learn about the history of
Ethernet and IEEE Ethernet standards. This Section discusses the operation of Ethernet, Ethernet
framing, and error handling, as well as the different types of the collisions on Ethernet networks.
In addition, this section introduces collision domains and broadcast domains. Finally, this section
describes function of STP protocol.

3.7.1 IEEE 802.3/Ethernet and the OSI Model

LAN standards define the physical media and the connectors used to connect devices to
media at the physical layer of the OSI reference model. LAN standards also define the way
devices communicate at the data link layer. In addition, LAN standards define how to
encapsulate protocol-specific traffic in such as way that traffic going to different upper-layer
protocols can use the same channel that passes though that layers of the OSI model. To provide
these functions, the IEEE Ethernet data link layer has two sublayers:

• Media Access Control (MAC) (802.3)—As the name implies, the MAC sublayer defines
how to transmit frames on the physical wire. It handles physical addressing
associated with each device, network topology definition, and line discipline.
• Logical Link Control (LLC) (802.2)—As the name implies, the LLC sublayer is
responsible for logically identifying different protocol types and then encapsulating
them. A type code or a service access point (SAP) identifier performs the logical
identification. The type of LLC frame used by an end station depends on what
identifier the upper-layer protocol (such as IP) expects.

Although IEEE 802.2 represents one standard type of frame encapsulation, there are
others, such as Ethernet II (used primarily with TCP/IP–based Ethernet LANS.

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