guided media

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Jun 10, 2022 Data Link Layer Guided Media Media that provide a conduit from one device to another. Signals travelling along any of these media is directed and contained by the physical limits of the medium. Examples are: Twisted-pair cable Coaxial cable Fiber-optic cable

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Guided Media. Media that provide a conduit from one device to another. Signals travelling along any of these media is directed and contained by the physical limits of the medium. Examples are: Twisted-pair cable Coaxial cable Fiber-optic cable. Twisted-Pair Cable. - PowerPoint PPT Presentation

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Page 1: Guided Media

Apr 22, 2023 Data Link Layer

Guided Media

Media that provide a conduit from one device to another.

Signals travelling along any of these media is directed and contained by the physical limits of the medium.

Examples are: Twisted-pair cable Coaxial cable Fiber-optic cable

Page 2: Guided Media

Apr 22, 2023 Data Link Layer

Twisted-Pair Cable

Uses two metallic (copper) conductors with individual plastic insulator each.

Accepts and transports signals in the form of electric current.

One wire is used to carry signals to the receiver and the other is used as a ground reference.

The receiver uses the difference between the two signal levels in the wires.

Noise or crosstalk effect is balanced by twisting the wires.

Page 3: Guided Media

Figure 7.3 Twisted-pair cable

Page 4: Guided Media

Apr 22, 2023 Data Link Layer

Twisted-Pair (Continued…)

Twisted-pair cable can be divided into: Unshielded (UTP) – The most common

twisted-pair cable used in data communication.

Shielded (STP) – IBM’s version for its use. It has a metal foil of braided-mesh covering encasing each pair of the insulated conductors. It improves the quality of the cable, but it is bulkier.

Page 5: Guided Media

Figure 7.4 UTP and STP

Page 6: Guided Media

Apr 22, 2023 Data Link Layer

Twisted-Pair (Continued…)

Standards: The Electronic Industries Association

(EIA) has developed standards to classify UTP cable into seven categories based on their quality.

Category 1 is the lowest in quality and category 7 is the highest.

Connectors: The most common is RJ45, which is a

keyed connector.

Page 7: Guided Media

Table 7.1 Categories of unshielded twisted-pair cablesTable 7.1 Categories of unshielded twisted-pair cables

Category Bandwidth Data Rate Digital/Analog Use

1 very low < 100 kbps Analog Telephone

2 < 2 MHz 2 Mbps Analog/digital T-1 lines

3 16 MHz 10 Mbps Digital LANs

4 20 MHz 20 Mbps Digital LANs

5 100 MHz 100 Mbps Digital LANs

6 (draft) 200 MHz 200 Mbps Digital LANs

7 (draft) 600 MHz 600 Mbps Digital LANs

Page 8: Guided Media

Figure 7.5 UTP connector

Page 9: Guided Media

Apr 22, 2023 Data Link Layer

Twisted-Pair (Continued…)

Performance: A twisted-pair cable can pass a wide

range of frequencies. However, the attenuation (dB/mi) sharply increases with frequencies above 100KHz.

Applications: Voice and data channels in telephone

lines. High data rate connections in DSL lines. 10Base-T and 100Base-T LANs.

Page 10: Guided Media

Figure 7.6 UTP performance

Page 11: Guided Media

Apr 22, 2023 Data Link Layer

Coaxial Cable

Uses central core conductor of solid or stranded copper wire enclosed in an insulating sheath.

The insulating sheath is then encased in an outer conductor of metal foil, braid or a combination of the two.

The metallic wrapping serves both as a shield against noise and as a second conductor that completes the circuit.

This outer conductor is also enclosed in another insulating sheath and the whole thing is protected by a plastic cover.

Page 12: Guided Media

Figure 7.7 Coaxial cable

Page 13: Guided Media

Apr 22, 2023 Data Link Layer

Coaxial Cable (Continued…)

Standards: Categorised by their radio government

(RG) ratings with each number denotes a unique set of physical specifications.

Category Impedance Use

RG-59RG-59 75 Cable TV

RG-58RG-58 50 Thin Ethernet

RG-11RG-11 50 Thick Ethernet

Page 14: Guided Media

Apr 22, 2023 Data Link Layer

Coaxial Cable (Continued…)

Connectors: The most commonly used connectors

are the Bayone-Neill-Concelman (BNC) connectors.

The three popular types of BNC are: BNC – used to connect the end of the cable

to a device, such as TV set. BNC T – used in Ethernet networks to branch

out a cable for connection to a computer or other devices.

BNC terminator – used at the end of the cable to prevent the signal reflection.

Page 15: Guided Media

Figure 7.8 BNC connectors

Page 16: Guided Media

Apr 22, 2023 Data Link Layer

Coaxial Cable (Continued…)

Performance: Coaxial cable has a much higher

bandwidth compared to the twisted-pair cable. However, the signal weakens rapidly and it requires frequent use of repeaters.

Applications: Analogue and digital telephone

networks. Cable TV. Traditional Ethernet LANs.

Page 17: Guided Media

Figure 7.9 Coaxial cable performance

Page 18: Guided Media

Apr 22, 2023 Data Link Layer

Fiber-Optic Cable

Made of glass or plastic and transmits signals in the form of light.

Making use of the property of light that changes direction when travelling through substances of differing density.

A glass or plastic core is surrounded by a cladding of less dense glass or plastic.

The difference in density of the two materials must be such that a beam of light moving through the core is reflected off the cladding instead of being refracted into it.

Page 19: Guided Media

Figure 7.14 Fiber construction

Page 20: Guided Media

Figure 7.10 Bending of light ray

Page 21: Guided Media

Figure 7.11 Optical fiber

Page 22: Guided Media

Apr 22, 2023 Data Link Layer

Fiber-Optic Cable (Continued…)

Sizes: Defined by the ratio of the diameter of

their core to the diameter of their cladding, both expressed in micrometers.

7/1257/125

100/125100/125

62.5/12562.5/125

50/12550/125

Type

7

100

62.5

50

Core

125

125

125

125

Cladding

Page 23: Guided Media

Apr 22, 2023 Data Link Layer

Fiber-Optic (Continued…)

Connectors: Uses three types of connectors:

Subscriber channel (SC) – uses push/pull locking system.

Straight-tip (ST) – uses bayonet locking system and more reliable than SC.

MT-RJ – a new connector with the same size as RJ45.

Performance: Attenuation is flatter than in the case of

TP and coaxial cables. Therefore, less repeater is needed for fiber-optic cable.

Page 24: Guided Media

Figure 7.15 Fiber-optic cable connectors

Page 25: Guided Media

Figure 7.16 Optical fiber performance

Page 26: Guided Media

Apr 22, 2023 Data Link Layer

Fiber-Optic (Continued…)

Applications: Used often in the backbone networks. Used in hybrid cable TV network as the

backbone. Used in 100Base-FX and 1000Base-X

LANs