Page 64 - M. Abrahim Thesis

Chapter (3) Networking Media and Data Link Layers Protocols

802.11g provides the same throughout as 802.11a but with backwards compatibility for 802.11g
devices using Orthogonal Frequency Division Multiplexing (OFDM) modulation technology. Cisco
has developed an access point that permits 802.11b and 802.11a devices to coexist on the same
WLAN. The access point supplies gateway services allowing these otherwise incompatible
devices to communicate.
https://www.youtube.com/watch?v=hhks5xSpM-0
3.6 LAN Physical Layer

Ethernet is the most widely used LAN technology. Ethernet was first implemented by a
group called DIX (Digital, Intel, and Xerox). DIX created and implemented the first Ethernet
LAN specification, which was used as the basis for the Institute of Electrical and Electronics
Engineer (IEEE) 802.3 specification released in 1980. Later, the IEEE extended the 802.3
committee to three new committees known as 802.3u (Fast Ethernet), 802.3z (Gigabit Ethernet
over Fiber), and 802.3ab (Gigabit Ethernet over UTP). The cabling aspect of the LAN exists at
Layer 1 of the Open System Interconnection (OSI) reference model. Many topologies support
LANs, as well as different physical media. Figure 3-12 shows a subset of physical layer
implementations that you can deploy to support Ethernet.

Figure 3-12 shown a LAN Physical Layer Implementation

The basic functions of media are to carry a flow of information, in the form of bits and
bytes, through a LAN. Other than wireless LANs (that use the atmosphere, or space, as the
medium), networking media confines network signals to a wire, cable, or fiber. Networking
media are considered Layer 1 components of LANs. Computer networks can be built with many
different media types. Each media has advantages and disadvantages. What is an advantage for
one media (CAT 5 cost) might be a disadvantage for another (fiber-optic cost).

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