4. • Sharing hardware or software
• E.g. print document
• Centralize administration and support
• E.g. Internet-based, so everyone can access the same
administrative or support application from their PCs
4
5. How many kinds of Networks?
• Depending on one’s perspective, we can classify
networks in different ways
• Based on transmission media: Wired (UTP, coaxial
cables, fiber-optic cables) and Wireless
• Based on network size: LAN and WAN (and MAN)
• Based on management method: Peer-to-peer and
Client/Server
• Based on topology (connectivity): Bus, Star, Ring,Mesh
5
6. Transmission Media
Two main categories:
Guided ― wires, cables
Unguided ― wireless transmission, e.g. radio,
microwave, infrared, sound, sonar
We will concentrate on guided media here:
Twisted-Pair cables:
Unshielded Twisted-Pair (UTP) cables
Shielded Twisted-Pair (STP) cables
Coaxial cables
Fiber-optic cables
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7. Twisted-Pair Cables
If the pair of wires are not twisted, electromagnetic
noises from, e.g., motors, will affect the closer wire
more than the further one, thereby causing errors
7
8. Unshielded Twisted-Pair (UTP)
Typically wrapped inside a plastic cover (for mechanical
protection)
A sample UTP cable with 5 unshielded twisted pairs of
wires
Insulator Metal
8
9. Shielded Twisted-Pair (STP)
STP cables are similar to UTP cables, except there is a
metal foil or braided-metal-mesh cover that encases
each pair of insulated wires
9
10. Fiber-Optic Cables
Light travels at 3108 ms-1 in free space and is the fastest
possible speed in the Universe
Light slows down in denser media, e.g. glass
Refraction occurs at interface, with light bending away
from the normal when it enters a less dense medium
Beyond the critical angle total internal reflection
10
11. Advantages and Disadvantages
Noise resistance ― external light is blocked by outer
jacket
Less signal attenuation ― a signal can run for miles
without regeneration (currently, the lowest measured loss
is about ~4% or 0.16dB per km)
Higher bandwidth ― currently, limits on data rates come
from the signal generation/reception technology, not the
fiber itself
Cost ― Optical fibers are expensive
Installation/maintenance ― any crack in the core will
degrade the signal, and all connections must be perfectly
aligned
11
12. LAN and WAN
• Local Area Network (LAN)
• Small network, short distance
• A room, a floor, a building
• Limited by no. of computers and distance covered
• Usually one kind of technology throughout the
LAN
• Serve a department within an organization
• Examples:
• Network inside the Student Computer Room
• Network inside CF502
• Network inside your home
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13. Wide Area Network (WAN)
• A network that uses long-range telecommunication links
to connect 2 or more LANs/computers housed in
different places far apart.
• Towns, states, countries
• Examples:
• Network of our Campus Your home
• Internet
WAN USA
Student
Computer
Centre 13
14. Peer-to-Peer Networks
• Peer-to-peer network is also called workgroup
• No hierarchy among computers all are equal
• No administrator responsible for the network
Peer-to-peer
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15. • Advantages of peer-to-peer networks:
• Low cost
• Simple to configure
• User has full accessibility of the computer
• Disadvantages of peer-to-peer networks:
• May have duplication in resources
• Difficult to uphold security policy
• Difficult to handle uneven loading
• Where peer-to-peer network is appropriate:
• 10 or less users
• No specialized services required
• Security is not an issue
• Only limited growth in the foreseeable future
15
16. Clients and Servers
• Network Clients (Workstation)
• Computers that request network resources or services
• Network Servers
• Computers that manage and provide network
resources and services to clients
• Usually have more processing power, memory and
hard disk space than clients
• Run Network Operating System that can manage
not only data, but also users, groups, security, and
applications on the network
• Servers often have a more stringent requirement
on its performance and reliability
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17. • Advantages of client/server networks
• Facilitate resource sharing – centrally administrate
and control
• Facilitate system backup and improve fault tolerance
• Enhance security – only administrator can have access
to Server
• Support more users – difficult to achieve with peer-to-
peer networks
• Disadvantages of client/server networks
• High cost for Servers
• Need expert to configure the network
• Introduce a single point of failure to the system
17
18. Topology ― 3 basic types
• How so many computers are connected
together?
Bus Topology Ring
Topology
Star Topology
Hub
18
19. • Bus Topology
• Simple and low-cost
• A single cable called a trunk (backbone, segment)
• Only one computer can send messages at a time
• Passive topology - computer only listen for, not
regenerate data
• Star Topology
• Each computer has a cable connected to a single
point
• More cabling, hence higher cost
• All signals transmission through the hub; if down,
entire network down
• Depending on the intelligence of hub, two or more
computers may send message at the same time
19
20. • Ring Topology
• Every computer serves as
a repeater to boost signals
• Typical way to send data: Ack T T
• Token passing T
• only the computer who T data T data
gets the token can send
data T
T
• Disadvantages T Ack T data
Ack
• Difficult to add computers
T
• More expensive
T Ack
• If one computer fails, whole network fails
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21. What is VOIP ????
VoIP (Voice over Internet Protocol) is a quite recent
advancement in telephony systems. It uses a packet
switched network, like the internet, to pass digitized
voice data from one point to another. This allows
telecommunications companies to squeeze more
conversations in the same amount of bandwidth.
Even home users can use VoIP handsets, or through
computers via software, to call other people who are
online for free.
Other terms commonly associated with VoIP are IP
telephony, Internet telephony, voice over
broadband (VoBB), broadband telephony,
IP communications, and broadband phone.
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22. Internet telephony refers to communications services —
voice, fax, SMS, and/or voice-messaging applications—
that are transported via the Internet, rather than
the public switched telephone network (PSTN).
The steps involved in originating a VoIP telephone call
are signaling and media channel setup, digitization of
the analog voice signal, encoding, packetization, and
transmission as Internet Protocol (IP) packets over
a packet-switched network. On the receiving side,
similar steps (usually in the reverse order) such as
reception of the IP packets, decoding of the packets and
digital-to-analog conversion reproduce the original
voice stream
22
23. Even though IP Telephony and VoIP are terms that
are used interchangeably, they are actually different;
IP telephony has to do with digital telephony systems
that use IP protocols for voice communication, while
VoIP is actually a subset of IP Telephony. VoIP is a
technology used by IP telephony as a means of
transporting phone calls.
23
24. PBX (Public Branch Exchange) is a miniature telephone
network that is set to work within a company while
providing several lines to an external phone company
where calls can go in or out. Companies utilize a PBX in
order to minimize cost. Instead of having a single telephone
line for every office or department which are only used for
a fraction of the time, the company can reduce this to a few
lines with the use of PBX while still having a telephone unit
in each office. All internal calls are routed internally while
calls to the outside take any of the available outside lines.
Most PBX systems are not equipped to handle VoIP calls
because they were created and perfected before the advent
of VoIP. But the advantages of implementing VoIP services
in a PBX system has motivated companies and
manufacturers to develop IP PBX systems.
24
25. Advantages of
Because of the bandwidth efficiency and low costs
that VoIP technology can provide, businesses are
migrating from traditional copper-wire telephone
systems to VoIP systems to reduce their monthly
phone costs.
Routing phone calls over existing data networks to
avoid the need for separate voice and data networks.
The ability to transmit more than one telephone call
over a single broadband connection.
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26. Secure calls using standardized protocols . Most of
the difficulties of creating a secure
telephone connection over traditional phone lines,
such as digitizing and digital transmission, are
already in place with VoIP. It is only necessary
to encrypt and authenticate the existing data stream.
26
27. Li-Fi
It is the term some have used to label the fast and cheap wireless-communication
system, which is the optical version of Wi-Fi. Li-Fi has the advantage of being able to
be used in sensitive areas such as in aircraft without causing interference. 27
28. The Session Initiation Protocol (SIP)
It is an signaling protocol widely used for controlling communication sessions such as voice and
video calls over Internet Protocol (IP). The protocol can be used for creating, modifying and
terminating two-party (unicast) or multiparty (multicast) sessions. Sessions may consist of one or
several media streams. Other SIP applications include video conferencing, streaming multimedia
distribution, instant messaging, presence information, file transfer and online games. 28
29. Wimax (Worldwide Interoperability for Microwave Access)
Wireless metropolitan networks (MAN) such as WiMAX provide high-speed Internet access
at much greater distances than wireless LANs can. A MAN requires a transmitting tower and
a receiver and is typically operated by a government entity. It is a wireless communications
standard designed to provide 30 to 40 megabit-per-second data rates, with the 2011 update
providing up to 1 Gbit/s for fixed stations. WiMAX can be descriped as "a standards-based
technology enabling the delivery of last mile wireless broadband access as an alternative to 29
30. 4G Services
Networks today are increasingly becoming more mobile, so you don't have to be at home or
at work to get connected. For example, most mobile broadband services simply require the
use of a card that allows users to access the Internet.
30
31. Virtual Network Computing (VNC)
It stands for Virtual Network Computing. It is, in essence, a remote display system which allows
you to view a computing 'desktop' environment not only on the machine where it is running, but
from anywhere on the Internet and from a wide variety of machine architectures.
31
32. It is the use of computing resources (hardware and software) that are delivered as a
service over a network (typically the Internet). The name comes from the use of a
cloud-shaped symbol as an abstraction for the complex infrastructure it contains in
system diagrams. Cloud computing entrusts remote services with a user's data, software
32
and computation.
