Protocols define rules for communication including data format, meaning, and timing. Key elements are syntax, semantics, and timing. Standards provide guidelines and are categorized as de facto or de jure. Standard bodies include ISO, ITU-T, ANSI, IEEE, EIA, and IETF. Transmission media are guided (wired) or unguided (wireless) and include coaxial cable, fiber optic cable, and radio waves.

1. Protocols and Standards
Protocols:
set of rules that governs data communications.
A protocol defines what is communicated, how it is
communicated and when it is communicated.
Key elements:
Syntax: it refers to the structure or format of data.
Semantics: it refers to the meaning of each section of bits
Eg. Address used to identify the route to the destination
Timing: It refers to two characteristics; when and how
much to send.

2. Standards
Standards:
• Provide guidelines to manufacturers.
Types of Standards:
• de facto [by fact]-Not approved by an organization but
spreaded widely for use.
• de jure [by law]-Approved by an organization.

3. Standard organizations
• International Organization for Standardization (ISO)
• International Telecommunication Union-
Telecommunication Standards (ITU-T)
• American National Standards Institute (ANSI)
• Institute of Electrical and Electronics Engineers
(IEEE)
• Electronic Industries Association (EIA)
• International Engineering Task Force (IETF)

4. Standard organizations(contd.,)
• Internet Standards
• Thoroughly tested specification
• Strict procedure and must be followed.
• Internet draft
• Working document with no official status
• 6-month life time.

5. Transmission medium
Transmission medium:
• physical path between transmitter and receiver.
• Carry the information from source to destination

6. Types of Transmission medium

7. Types of Transmission medium
2 Types of transmission medium are:
• Guided media(wired) :
 provide a service from one device to another
 waves are guided along a physical path
 Eg., twisted pair, coaxial cable and optical fiber
• Unguided media(wireless):
 Transport electromagnetic waves without Physical
medium
 Eg., Radio waves, Microwave and Infra red

8. Guided media-Coaxial cable
• Inner conductor –Central core
of solid or wire(copper)
surrounded by insulating
sheath-
• Outer conductor-Made up of
metal foil or braid or
combination of both
 Acts as a shield for noise and
completes the circuit.
 Enclosed in an insulting sheath
• Whole cable is protected by
plastic cover

9. Coaxial cable standards
• Categorized by their radio government (RG) ratings
• RG-Denotes the unique set of physical specifications
 Wire gauge of inner conductor
 Thickness and type of inner insulator
 Construction of shield
 Size and type of outer casting

10. Coaxial cable connectors
• For connecting coaxial cables to devices
• Commonly used connector-BNC(Bayone-Neill-Concelman)
• Three types of connectors are:
 BNC connector
 BNC T Connector
 BNC terminator

11. Types
• BNC connector-Connect the end of the cable to the devices.
Eg.TV set
• BNC T Connector-To branch out to a connection to a
computer or other device. Eg. Ethernet networks.
• BNC Terminator-Used at the end of the cable to prevent the
reflection of signal.

12. Performance
• Attenuation is higher
• Higher bandwidth
• Signal weakens rapidly and requires frequent use of
repeaters.

13. Applications
• Used in Analog telephone networks-Carry 10,000 voice
signals.
• In digital telephone networks-Carry digital data upto
600Mbps.
• Cable TV networks.
• Traditional Ethernet LANs
• Used in thin and thick Ethernet.
 10Base-2(Thin Ethernet)-Uses RG-58
 10BAse5(Thick Ethernet-Uses RG-11

14. Fibre optic cable
• Fiber-optic cable transmit signals in the form of light.
• Made up of Glass or Plastic
• Optical fibre uses reflection to guide light through a channel
• Glass or Plastic core is surrounded by Cladding(Dense Glass or
Plastic)

15. Bending of light rays
• I-Angle the ray makes with the line perpendicular to the
interface between 2 substances
• If the angle of incidence I is less than the critical angle, the ray
refracts and moves closer to the surface.
• If the angle of incidence is equal to the critical angle, the light
bends along the interface.
• If the angle is greater than the critical angle, the ray reflects
and travels again in the denser substance.

16. Propagation modes

17. Types of Multimode
Multimode step-index fiber
• Density of the core remains constant from the center to the edges.
• Beam of light moves in a straight line -Reaches the interface of the
core and the cladding.
• Light beam changes the direction at the interface between the core
and cladding
•Step index -suddenness of this change, which contributes to the
distortion of the signal
Multimode graded-index fiber
• Core Density decreases with distance from the center
• Results in carving of light beams.

18. Multimode fibres

19. Single mode fibre
• Uses step index fibre
• Carries light pulses along single path
 Fibre types

20. Cable Composition
• Outer Jacket- Either PVC or Teflon
• Inner Jacket-Kevlar Strands(To strengthen the cables)
• Kevlar-Strong material used in refraction of bulletproof
• Plastic coating- To cushion the fibre
• Fibre-Center of the cable(Consists of Cladding and core)

21. Fibre optic cable connectors
• Three types of connectors:
 SC connector(Subscriber channel)-Uses push/pull
locking system. Eg. Cable TV
 ST connector(Straight-Tip)-Used for connecting cables to
Networking devices. More reliable than SC
 MT-RJ connector-Same as coaxial cable connector.

22. Performance
• Attenuation is flatter than coaxial cable
• Need fewer repeaters.

23. Applications
• Often found in backbone networks
• cost-effective.
• With wavelength-division multiplexing (WDM), we can
transfer data at a rate of 1600 Gbps.

24. Advantages and Disadvantages
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.