Networks connect computers and devices to enable sharing of resources and communication between users. They come in various topologies like bus, star, ring and hybrid and use different media like coaxial cable, twisted pair, fiber optic or wireless. Common networking technologies include Ethernet, Token Ring, WiFi and FDDI, each with their own standards and characteristics. Understanding networks involves knowledge of topologies, media, technologies and how they work together to transmit and receive signals that represent digital data.

1. Unit01:
Understanding Networking

2. Overview
• Network
• Types of Network
• Topologies
• Media Types
• Networking Technologies and
Characteristics

3. What is Network ?
• A group of computers and other devices that are
connected by some type of transmission media.
– Small as two computers connected by a cable in a home, office
– Large as several thousand computers connected by cable,
satellite or phone line.

4. Why use Network ?
• Manage or Administer resources on multiple computers
from a central location
• Enable multiple users to share devices and resources
such as:
– Printers
– Faxes
– Programs and Files
• Word Processing
• Data Base

5. Types of Network
• Peer-to-peer Networks
• Client/Server Networks

6. Peer to Peer
• Simple to configure
• Don’t need much technical expertise
• Typically less expensive to setup
• Not very flexible

7. Client/Server Networks
• Servers facilitate communication and resource sharing
between clients.
• Computers on a client/server
network act as a client.

8. Advantages of Client/Server
• User login accounts and passwords for anyone on a
server-based network can be assigned in one place
• Access to multiple shared resources can be centrally
granted to a single user or groups of users
• Problems on the network can be tracked, diagnosed,
and often fixed from one location.
• Servers are optimized to handle heavy processing loads
and dedicated to handling requests from clients.
• Servers can connect more than a handful of computers
on a network

9. LAN , MAN and WAN
• LAN – Local Area Network
• MAN – Metropolitan Area Network
• WAN – Wide Are Network

10. Local Area Network
• A network of computers and other devices that is
confined to a relatively small space, such as one building
or even one office
• Interconnected and rely on several servers running many
different applications and managing resources other than
data.
• Example : A School Network.

11. Local area Network

12. Metropolitan Area Network
• A network that is larger than a LAN and connects clients
and servers from multiple buildings
• A MAN may use different transmission technology and
media than a LAN because of the distance it covers
• Example : 2 or more Buildings is Connected

13. Metropolitan Area network

14. Wide area Network
• A network that connects two or more geographically
distinct LANs or MAN
• WAN carry data over longer distances than LAN
• WANs require slightly different transmission methods
and media and often use a greater variety of
technologies than LAN
• Most MAN can also be described as WAN
• WAN commonly connect separate offices in the same
organization, whether they are across town or across the
world from each other

15. Wide Area Network

16. Topologies
• Physical layout of computer network
– Bus
– Star
– Ring
– Hybrid

17. Bus Topology
• Consists of a single cable connecting all nodes on a
network without intervening connectivity devices
• The single cable is called bus and can only support one
channel for communication
• Uses coaxial cable
• 50 ohm Resistor know as
Terminator

18. Star Topology
• Every node on the network is connected through a
central device, such as hub , switch etc..
• Uses twisted-pair or fiber-optic cabling
C li e n t
S e r v e r

19. Ring Topology
• In a ring topology, each node is connected to the two
nearest nodes so that the entire network forms a circle
• Data is transmitted clockwise, in one direction
(unidirectional), around the ring
• The fact that all workstations participate in delivery
makes the ring topology an active topology
• A ring topology also differs in that it has no “ends” and
data stops at its destination and, twisted-pair or fiber-
optic cabling is used as the physical medium

20. Ring Topology
S e r v e r
C lie n t

21. Hybrid
• The hybrid topology uses the physical layout of a star in
conjunction with the ring topology’s data transmission
method
• Data is sent around the star in a circular pattern
• This hybrid topology benefits from the fault tolerance of
the star topology
• In a hybrid topology, groups of workstations are star-
connected to hubs and then networked via a single bus
• With this design, you can cover longer distances and
easily interconnect or isolate different network segments

22. Hybrid Topology

23. Communication
Media and Transmission

24. What is a signal ?
• Data is communicated by means of a signal, and a
signal is a change in voltage over time
• Distortion of the signal is known as interference
• Networks are generally not resilient to signal interference
• NICs, hubs and other devices generate signals which
travel along the network media
• The signals are converted to data as they travel through
the OSI layers
• Cable testers can be used to check signal quality and
strength

25. Measuring Signals
-1
-0.8
-0.6
-0.4
-0.2
0
0.2
0.4
0.6
0.8
1
1 22 43 64 85 106 127 148 169 190 211 232 253 274 295 316 337 358 379 400 421 442 463 484 505 526 547 568 589 610 631 652 673 694 715
Frequency
Amplitude

26. Definitions
• Voltage – the force which moves an electrical current against
resistance
• Waveform – the shape of the signal (previous slide is a sine wave)
derived from its amplitude and frequency over a fixed time (other
waveform is the square wave)
• Amplitude – the maximum value of a signal, measured from its
average state
• Frequency (pitch) – the number of cycles produced in a second –
Hertz (Hz). Relate this to the speed of a processor eg 1.4GigaHertz
or 1.4 billion cycles per second

27. Analogue Signals vs Digital signals
• Analogue Signals
– Human Voice – best
example
– Ear recognises sounds
20KHz or less
– AM Radio – 535KHz to
1605KHz
– FM Radio – 88MHz to
108MHz
• Digital signals
– Represented by Square
Wave
– All data represented by
binary values
– Single Binary Digit – Bit
– Transmission of contiguous
group of bits is a bit stream
– Not all decimal values can
be represented by binary

28. Amplitude Modulation vs
Frequency Modulation
AM- same
frequency,
different
amplitudes
FM- Different
frequencies

29. Digital Signals
1 0 1 0 1 0 1 0

30. Analogue vs Digital (Advan)
• Analogue Advantages
– Best suited for audio
and video
– Consume less
bandwidth
– Available world wide
– Less susceptible to
noise
• Digital Advantages
– Best for computer data
– Can be easily
compressed
– Can be encrypted
– Equipment is more
common and less
expensive
– Can provide better
clarity

31. Asynchronous Transmission
• Uses start and stop bits to delineate pieces of data,
usually characters when used with modems
– Less efficient than synchronous (overhead of bits)
– Best suited for short bursts, such as Internet use
– Less resistant to disruption

32. Synchronous Transmission
• Does not use stop/start bits – instead devices agree
timing
– Faster than asynchronous (no overheads)
– Transmission is in blocks, not single characters
– Can be slow on poor quality media

33. How transmissions flow over media
• Simplex – only in one direction
• Half-Duplex – Travels in either direction, but not both
directions at the same time
• Full-Duplex – can travel in either direction simultaneously

34. Baseband vs Broadband
Transmission
• In baseband transmission, digital signals are sent
through direct current (DC) pulses applied to the wire
• In broadband transmission, signals are modulated as
radio frequency (RF) analog pulses that use different
frequency ranges

35. Networking Media

36. Networking Media
• Electrical Cable
– Coaxial Cable
• Single copper conductor in the center surrounded
by a plastic layer for insulation and a braided metal
outer shield.
– Twisted pair
• Four pairs of wires twisted to certain specifications.
• Available in shielded and unshielded versions.

37. Networking Media
• Fiber-optic
– A cable, consisting of a center glass core surrounded
by layers of plastic, that transmits data using light
rather than electricity.
• Atmosphere/Wireless
– Uses Electromagnetic waves. whose frequency range
is above that of microwaves, but below that of the
visible spectrum.

38. Coaxial Cable
• First type of networking
media used
• Available in different
types :
– RG-6 – Cable TV,
– RG58/U – Thin Ethernet,
– RG8 – Thick Ethernet
• Largely replaced by
twisted pair for networks

39. Coaxial Cable
• Advantages of
Coaxial
– Easy to Install
– Small in diameter
– Shielded to reduce
EMI and RFI
interference
• Disadvantages of
Coaxial
– Must be grounded to
prevent interference
– More expensive than
twisted pair
– Does not support high
speed transmissions
– Its base band
transmissions does
not allow for integrated
video and voice

40. Unshielded Twisted Pair

41. Unshielded Twisted Pair
• Advantages
– Inexpensive
– Widely used
– Supports many
network types
• Disadvantages
– Susceptible to
interference
– Prone to damage
during installation
– Distance limitations

42. Categories of UTP
Category Pair's Transmission Usage
Category 1 2 Pairs Voice Grade Used by telecoms, but not for data
Category 2 2 Pairs 4 Mbps Can be used for data, no longer
recognised
Category 3 4 Pairs 10 Mbps Used for 10BASE-T and voice
Category 4 4 Pairs 16 Mbps Used in IBM Token Ring
Category 5 4 Pairs 100 Mbps + Ethernet and 100BASE-X

43. Fiber Optic
• Fiber-Optic Cable
– Contains one or
several glass fibers at
its core
– Cladding is the glass
shield around the core

44. Fiber Optic Mode
• Single-Mode Fiber
– Carries single
frequency of light to
transmit data
• Multimode Fiber
– Carries many
frequencies of light
over a single or many
fibers

45. Fiber Optic
• Advantages
– Can be installed over
long distances
– Provides large
amounts of bandwidth
– Not susceptible to EMI
RFI
– Can not be easily
tapped (secure)
• Disadvantages
– Most expensive media
to purchase and install
– Rigorous guidelines
for installation

46. Wireless
• Radio transmits at 10KHz to 1KHz
• Microwaves transmit at 1GHz to
500GHz
• Infrared transmits at 500GHz to
1THz
• Radio transmission may include:
– Narrow band
– High-powered
– Frequency hopping spread
spectrum (the hop is controlled by
accurate timing)
– Direct-sequence-modulation
spread spectrum (uses multiple
frequencies at the same time,
transmitting data in ‘chips’ at high
speed)

47. Connectors
Fibre Optic
Thicknet
RJ45
T-Piece

48. Connectors
• RJ-11
– common telephone connection interface
• RJ-45
– common type of media connector for Ethernet 10BaseT, 100BaseT, and
1000BaseT networks running on UTP
• AUI
– Used for both ThickNet and ThinNet coaxial cables
• BNC
– connect devices to a ThinNet 10Base2 Ethernet network
• ST
– fiber optic connector used for duplex communications
• SC
– Fiber optic used for simplex communications
• RS-232
– This is the serial interface with either 9 or 25 pins found on every PC

49. Network Technologies

50. Ethernet (802.3)
• Ethernet is the most widely used local area network
(LAN) technology.
• An Ethernet LAN may use coaxial cable, special grades
of twisted pair wiring, or fiber optic cable. "Bus" and
"Star" wiring configurations are supported.
• Ethernet devices compete for access to the network
using a protocol called Carrier Sense Multiple Access
with Collision Detection (CSMA/CD).

51. Ethernet Implementations
• Particularly important Ethernet implementations include:
– Fast Ethernet (e.g. 100BaseT and 100BaseFX)
• The IEEE 802.3u specification covers Fast
Ethernet
– Gigabit Ethernet (e.g. 1000BaseT, 1000BaseSX, and
1000BaseLX)
• The IEEE 802.3z specification addresses Gigabit
Ethernet
– Iso-Ethernet enables Ethernet LANs at different
geographic locations to be connected over ISDN

52. Ethernet Standards

53. Token Ring (802.5)
• Physically, token ring LANs resemble star topologies, but
technically they are rings
– Ring is physically implemented in MAUs
– UTP is the most common cabling
• Speed is typically 16 mbps, however, 4 mbps and 100
mbps token ring networks exist

54. Wireless (802.11x)
• Wireless protocols are described under IEEE 802.11
• Transmit data to the WAP that acts as a hub
• Infrastructure mode
• Ad-hoc mode
• Data throughput of up to 11 Mbps
• The 802.11b protocol runs half-duplex
• 2.4 GHz range

55. FDDI
• A network technology whose standard was originally
specified by ANSI in the mid-1980s and later refined by
ISO
• FDDI (pronounced “fiddy”) uses a double ring of
multimode or single mode fiber to transmit data at
speeds of 100 Mbps
• FDDI is more reliable and more secure than
transmission methods that depend on copper wiring
• FDDI technology has a high cost relative to Fast
Ethernet

56. Summary
• By understanding how networks are shaped, or their
physical topologies, you will be able to better understand
the installation and configuration of a network
• Networking Media and Connectors
• Networking Technologies and Standards