DCN 5th ed. slides

1. PART II: PHYSICAL LAYER
TRANSMISSION MEDIA
Subject: Computer Networks
Tutor: Bilal Munir Mughal
1
Ch-7

2. Content Outline
 INTRODUCTION
 GUIDED MEDIA
 Twisted-Pair Cable
 Coaxial Cable
 Fiber-Optic Cable
 UNGUIDED MEDIA: WIRELESS
 Radio Waves
 Microwaves
 Infrared
2

3. Network/Transmission medium
 A transmission medium can be broadly defined as anything that
can carry information from a source to a destination.
 Transmission media are actually located below the physical layer
and are directly controlled by the physical layer.

4. CHOOSING NETWORK MEDIA
To choose the best type of media for your network, you
should know how each medium reacts to the following
factors
 Cost
 Installation
 Capacity (Bandwidth & Node)
 Attenuation
 Immunity to Electromagnetic Interference (EMI)
/noise

5. Classes of transmission media

6. GUIDED/WIRED/CABLE MEDIA
Guided media, which are those that
provide a conduit from one device to
another, include:
Twisted-pair cable,
Coaxial cable,
and Fiber-optic cable.

7. Twisted-pair cable

8. UTP and STP cables

9. CAT 7 SSTP

10. Categories of unshielded twisted-pair cables
Name
Typical
construction
Bandwidth Applications Notes
Level 1 0.4 MHz Telephone and modem lines
Not described in EIA/TIA recommendations.
Unsuitable for modern systems.
Level 2 4 MHz Older terminal systems, e.g. IBM 3270 -do-
Cat.3 UTP 16 MHz 10BASE-T and 100BASE-T4 Ethernet
Described in EIA/TIA-568. Unsuitable for speeds
above 16 Mbit/s. Now mainly for telephone cables
Cat.4 UTP 20 MHz 16 Mbit/s,Token Ring Not commonly used
Cat.5 UTP 100 MHz 100BASE-TX & 1000BASE-T Ethernet Common in most current LANs
Cat.5e UTP 100 MHz 100BASE-TX & 1000BASE-T Ethernet
Enhanced Cat5. Same as Cat5, but with better
testing standards.
Cat.6 UTP 250 MHz 10GBASE-T Ethernet SFS-EN 50173-1
Cat.6a U/FTP, F/UTP 500 MHz 10GBASE-T Ethernet
Adds cable shielding. ISO/IEC 11801:2002
Amendment 2.
Cat.7 F/FTP, S/FTP 600 MHz
Telephone, CCTV, 1000BASE-TX in the
same cable. 10GBASE-T Ethernet.
Fully shielded cable. ISO/IEC 11801 2nd Ed.
Cat.7a F/FTP, S/FTP 1000 MHz
Telephone, CATV, 1000BASE-TX in the
same cable. 10GBASE-T Ethernet.
Uses all four pairs. ISO/IEC 11801 2nd Ed.Am. 2.
Cat.8.1 U/FTP, F/UTP
1600-
2000 MHz
Telephone, CATV, 1000BASE-TX in the
same cable. 40GBASE-T Ethernet.
In development.
Cat.8.2 F/FTP, S/FTP
1600-
2000 MHz
Telephone, CATV, 1000BASE-TX in the
same cable. 40GBASE-T Ethernet.
In development.

12. Ethernet Classes & UTP Cable Types
Ethernet Class Maximum Data Rate Cable Type
10Base - T 10 Mbps UTP Cat-3 or Cat-5
100Base - T 100 Mbps UTP Cat-5, Cat-5e, Cat-6 or Fiber
1000Base - T 1 Gbps UTP Cat-5, Cat-5e, Cat-6 or Fiber
10 GbE 10 Gbps UTP Cat-5e, Cat-6, Cat-7 or Fiber

13. UTP connector

15. UTP performance

16. Coaxial cable

17. BNC connectors

18. Categories of coaxial cables

19. Coaxial cable performance

20. Optical fiber

21. Bending of light ray

22. Propagation modes

23. Modes

24. Fiber types

25. Fiber construction

26. Fiber-optic cable connectors

27. Advantages and Disadvantages of Optical Fiber
 Advantages
 Higher bandwidth
 Less signal attenuation
 Immunity to electromagnetic interference
 Resistance to corrosive materials
 Light weight
 Greater immunity to tapping
 Disadvantages
 Installation and maintenance
 Unidirectional light propagation
 Cost
27

28. ! PVC and Plenum Cable !
PVC (PolyVinyl Chloride ):
• It is a flexible and inexpensive plastic well suited for use as insulation and
cable jacketing
•Gives off poisonous gasses when burned
•Thus PVC cables are mostly used in the exposed areas of an office
Plenum-grade cable:
•It is certified to be fire resistant and to produce minimum amount of smoke
•More expensive and less flexible than PVC
Note: Plenum is the space between the false sealing and the floor above. Usually,
the air in plenum circulates with the air in rest of the building, and there are
strict fire codes about what can be placed in a plenum environment

29. UNGUIDED MEDIA: WIRELESS
Unguided media transport electromagnetic waves
without using a physical conductor. This type of
communication is often referred to as wireless
communication.
 Radio Waves
 Microwaves
 Infrared

30. Electromagnetic spectrum for wireless communication

31. EMS - Communication

32. Propagation methods

33. Radio and Microwave Bands

34. Wireless transmission waves

35. Radio waves are used for multicast communications, such as radio and
television, and paging systems.
Microwaves are used for unicast communication such as cellular
telephones, satellite networks, and wireless LANs. Microwave propagation
is line-of-sight.
Infrared signals can be used for short-range communication in a closed
area using line-of-sight propagation.

36. Omnidirectional antenna

37. Unidirectional antennas

38. 38
Questions?