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1. By: Muhammad Naveed Shaikh
INSTRUCTED BY
MUHAMMAD NAVEED SHAIKH
Telecom Systems & Networks
Lecture 1

2. By: Muhammad Naveed Shaikh
Computer Networking
• What do you mean by Networking?

3. By: Muhammad Naveed Shaikh
Networking
• The art and science of connecting
computers with each other in order to share
data and resources is termed as Networking.

4. By: Muhammad Naveed Shaikh
Advantages & Disadvantages of Networks
Let we discuss the advantages and
disadvantages of computer networks..

5. By: Muhammad Naveed Shaikh
ADVANTAGES OF NETWORKS
• Security / Encapsulation
• Distributed Databases
• Faster Problem Solving
• Centralized Management
• Security through Redundancy
• Shared Processing

6. By: Muhammad Naveed Shaikh
DISADVANTAGES OF NETWORK
• Server faults stop applications being available (SPOF)
• Network faults can cause loss of data.
• Network fault could lead to loss of resources
• User work dependent upon network
• System open to hackers
• Decisions tend to become centralized
• Could become inefficient
• Could degrade in performance
• Resources could be located too far from users
• Network management can become difficult

7. By: Muhammad Naveed Shaikh
Network Criteria
Network Criteria
Performance Reliability Security

8. By: Muhammad Naveed Shaikh
Applications of Netoworks
Some of the network applications in different fields are the following:
• Marketing & Sales
• Financial and Banking Services
• Enterprise Resource Planning
• Electronic Messaging
• Database Sharing
• Information Services
• Electronic Data Interchange (EDI)
• Teleconferencing
• Cellular Telephone
• Cable Television
• Intenet

9. By: Muhammad Naveed Shaikh
Physical & Logical Networks
• What is the main difference
between physical and logical
networks?

10. By: Muhammad Naveed Shaikh
Physical Networks
• Network must be connected physically with
wire or wireless medium.
• However even if the computers are
connected physically can’t communicate
with each other until and unless they are
logically connected as well.

11. By: Muhammad Naveed Shaikh
Logical Networks
• Network must be connected logically to
establish communication among them.
• Logical means there must be some address
assign to the node to communicate.
• The most famous addressing is IP
addressing scheme like 10.56.0.1

12. By: Muhammad Naveed Shaikh 12
Modes of Transmission
• A communications channel is classified as one of
three types:
(depending on the direction of transfer)
– Simplex:
– Full-Duplex:
– Half-Duplex:

13. By: Muhammad Naveed Shaikh
SIMPLEX
A simplex mechanism can only
transfer data in a single direction
• It is analogous to broadcast radio or
television

14. By: Muhammad Naveed Shaikh
Half duplex
– A half-duplex mechanism involves a shared
transmission medium
– The shared medium can be used for communication in
each direction but the communication cannot proceed
simultaneously
– It is analogous to using walkie-talkies where only
one side can transmit at a time

15. By: Muhammad Naveed Shaikh
Full duplex
– Allows transmission in two directions
simultaneously
• It is analogous to a voice telephone
conversation
–in which a participant can speak even if
they are able to hear at the other end

16. By: Muhammad Naveed Shaikh
Simplex, Half-Duplex, and Full-Duplex
Transmission
16

17. By: Muhammad Naveed Shaikh
COS & NOS
• What is the difference between client
operating system and Network operating
system?

18. By: Muhammad Naveed Shaikh
Client Operating System (COS)
• The Operating System which has the ability to be a client
in the network is known as Client Operating System.
• COS can not administrate the network.
• Client operating system can not be a domain administrator.
• Examples are:
• Windows 98, XP, Windows ME, Vista, DOS etc

19. By: Muhammad Naveed Shaikh
Network Operating System (NOS)
• The Operating System which has the ability to be a server inside the
network is known as Network Operating System.
• NOS can administrate the network.
• It must be a server edition like windows 2003 server
• Server operating system can be a domain administrator.
• Examples are:
• Windows 2000 server, Windows 2003 server etc

20. By: Muhammad Naveed Shaikh
Transmission Media
• Wired
• Wireless

21. By: Muhammad Naveed Shaikh
Coaxial Cable
Originally, Ethernet ran
over thicknet coaxial
cabling. This has, for
the most part, gone by
the wayside today.

22. By: Muhammad Naveed Shaikh
Twisted Pair Cabling
1. Shielded Twisted Pair Cabling (STP)
2. Unshielded Twisted Pair Cabling (UTP)

23. By: Muhammad Naveed Shaikh
Shielded Twisted Pair
Shielded twisted pair is a special kind of copper
telephone wiring used in some business
installations. An outer covering or shield is added
to the ordinary twisted pair. STP cable is also
used for Data Networks. Its shielding allows
greater tolerances for protection from EMI
interference, such as from flourescent light
fixtures and electric motors.

24. By: Muhammad Naveed Shaikh
Unshielded Twisted Pair
Unshielded twisted pair (UTP) cable is used for both LANs
and telephone systems. UTP cables are composed of four
color-coded pairs of copper conductors twisted around each
other. An outer jacket provides protection and keeps the pairs
in alignment. UTP cable connects to devices via 8 pin modular
connectors called RJ-45 plugs. All LAN protocols can operate
over UTP. Most modern LAN devices are equipped with RJ-
45 jacks.

25. By: Muhammad Naveed Shaikh
RJ-45 connectors
This is the
Connector
This is the
Jack

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Cross Over cable – pin
assignments

27. By: Muhammad Naveed Shaikh
Fiber Optics Cables
Fast Ethernet and
Gigabit Ethernet can
also be run over glass
optical fibers. This can
occur in two different
ways:
• Single mode fiber
(SMF)
• Multi mode fiber
(MMF)

28. By: Muhammad Naveed Shaikh
Single Mode Fiber (SMF)
• Single Mode Fiber transmits data by means of a
laser through the optical fiber medium. This laser
is projected in a straight line through the medium
due to the laser's high speed and continuity. It is
capable of higher bandwidth and greater cable run
distances than multimode fiber. SMF connections
spanning up to 2 kilometers

29. By: Muhammad Naveed Shaikh
Multi Mode Fiber (MMF)
• MMF uses LED to transmit light by
bouncing it off reflective surfaces within the
cable walls. These modes of light can travel
different distances, depending on the angle
they enter the cable. This means that they
will arrive at different times. (This
phenomenon is called modal dispersion.)

30. By: Muhammad Naveed Shaikh
Optical Fibre with ST Connector• Optical fibre is a glass fibre which can reflect light along a central
tube.
• Specify fibre as multimode or single mode; multimode is much
cheaper to use but typically limited to 500m runs (single mode
~200km).
Many different connectors, eg ST, SC, LC, MRTJ.
ST and SC connectors ST connector
Optic fibre basics

31. By: Muhammad Naveed Shaikh
A Wiring Closet
Optic fibre terminations
Copper terminations
Managed ethernet
switches

32. By: Muhammad Naveed Shaikh
A Busier Wiring Closet!
•Colour coordinated cables;
• Order of panels:
• Optic fibre at top,
• then copper RJ45,
• then switches,
• then media convertors.

33. By: Muhammad Naveed Shaikh
Transmission
Broadcasting
Ethernet is a broadcast-based
environment. In this
environment, all stations see all
frames placed on the network.
Following any transmission,
each station must examine
every frame to determine
whether that frame was meant
for it. Frames identified as
intended for a given station are
passed to a higher-layer
protocol.

34. By: Muhammad Naveed Shaikh
Media Access
The Ethernet media access uses the following process:
• Any station on a LAN can access the network at any time.
• Before sending data, stations listen for traffic on the
network.
• A station waits until it detects no traffic before it transmits
data.

35. By: Muhammad Naveed Shaikh
Collision handling
• Ethernet is a "first come, first serve" environment. In fact,
it was developed on a foundation known as Carrier Sense
Multiple Access with Collision Detection or CSMA / CD.
In such an environment, any station on the network can
transmit whenever the network is quiet. A collision occurs
when two stations listen for traffic, hear none, and then
transmit data at the same time. Both transmissions are
damaged, and the stations must retransmit at a later time.
Backoff algorithms determine when the colliding stations
should retransmit. These algorithms assign a random order
number for each collision-involved station to retransmit
the data.

36. By: Muhammad Naveed Shaikh
Copper: Cat5e UTP with RJ45 Connectors
• Cat5 is a basic cable standard – how many
strands, how thick, what twisting, how to
insulate. Cat3 is used for analogue telephone
lines; Cat5 is for basic ethernet, Cat5e is better.
Some people are using Cat6 or Cat7 now.
• UTP: Unshielded Twisted Pair. 8 individual
wires are twisted into 4 pairs and encased in a
sheath. A superior (but expensive) alternative is
STP: shielded twisted pair, where the pairs are
wrapped in metal foil which is connected to earth
at one end.
• RJ45: a standard design of plug, a little like a
large telephone plug.