Internet networks for o level students

2. • A computer network is simply a group of
computers that are so connected that resources
can be shared and information can be
exchanged.
• exchange information
• share resource
• wired & wireless

3. • Resource sharing
• Reliability
• Financial benefits
• Better communication medium
• Access to remote database

4. • Local Area Network (LAN)
• Metropolitan Area Network (MAN)
• Wide Area Network (WAN)
• Value-Added Network (VAN)
• Backbone
• Campus Area Network (CAN)
• Home Area Network (HAN)
• Wireless/Mobile Networks

5. • within a room/floor/building/organization
• usually less than 1 km in diameter

6. • sharing of expensive resources such as color laser printers
• high-speed exchange of essential information between key
people in an organization
• increase the range of potential applications
• increase productivity and profitability

7. • financial cost of networking hardware
• requires memory space in each computer
• complex
• lack of control
• security system must be implemented in order to protect
confidential data
• memory intensive programs(RDBMS) are particularly
vulnerable to networking because of memory requirement

8. • restricted geographical area
• relatively high speed than WAN
• private networks
• e.g. Computer Lab

9. • larger than LAN but smaller than WAN
• e.g. cable TV networks

10. • 5-50 KM
• generally not owned by a single organization (biz. purpose)
• large companies/universities with multiple buildings
• acts as a high-speed network to allow sharing of regional
resources

11. • nationwide or worldwide (public network)
• it may also enable LANs to communicate with each other

12. • ensure high-quality, reliable service for end users
• separate each user’s session
• use public transmission media such as telephone lines,
microwave link and satellite links

13. • Remote data entry
• Centralizing information
• Facilitating communications

14. • Hierarchical Networks : configure computers in a hierarchy
(client-server)
• Distributed Data-processing Networks : peer-to-peer

15. • A node is any device connected to a computer network.
• Nodes can be computers, personal digital assistants (PDAs),
cell phones, or various other network appliances.

16. • The most powerful type of computer on the network, that does
all the processing for the user.

17. • It is a personal computers on network that is operated by
network users.
• Each workstation process its own files using its own operating
system.

18. • refers to the difference between the highest and lowest
frequencies of a transmission channel
• In networking, bandwidth or throughput defines the net bit
rate (bit/s, kbit/s, Mbit/s, Gbit/s, etc.)

19. •Bandwidth can be divided into channels thus channel is simply
a portion of bandwidth that can be used for transmitting
data.two ways of allocating the capacity of bounded
transmission media are:Baseband & Broadband.
•Transmission use entire bandwidth for single channel.
• Allow the division of bandwidth into multiple channels.

20. • Network Interoperability is the continuous ability to send and
receive data between interconnected networks providing the
level of quality expected by the end user customer.

21. • an individual that is responsible for the maintenance
of computer hardware and software systems that make up
a computer network
• generally mid-level support staff within an organization and
do not typically get involved directly with users

22. • Initial network planning
• Frequency allocation, predetermined traffic routing to support
load balancing
• Cryptographic key distribution authorization
• Configuration management
• Fault management
• Security management
• Performance management
• Bandwidth management
• Accounting management

23. • a service that employs a variety of tools, applications and
devices to assist human network managers in monitoring and
maintaining networks
• There exist a wide variety of software and hardware products
that help in managing a network by sending them alerts when
they recognize problems.
• Upon receiving these alerts, management entities are
programmed to react by executing operator notification, event
logging, system shutdown and/or automatic attempts at system
repair
• Simple Network Management Protocol (SNMP)

24. • Physical Security Holes : unauthorized physical access
• Software Security Holes : privileged software
• Inconsistent Usage Holes : When a system administrator
assembles ineffective hardware and software such that the
system is seriously flawed from a security point of view

25. • Authorization : access only those resources they are authorized
• Authentication : username & password
• Encrypted Smart Cards : Punch card
• Biometric Systems : Thumb impression, retina eyes
• Firewall : Protection Layer
1. Packet Filter
2. Application Gateway
3. Circuit-level Gateway
4. Proxy Server

26. Chassis

27. Repeater
 Regenerates and propagates all electrical transmissions between 2
or more LAN segments
 Allows extension of a network beyond physical length limitations
 Layer 1 of the “OSI model”
Higher
Layers
Physical
Higher
Layers
PhysicalPhysical
Repeater
Network A Network B

28. Repeater

29. Bridge/Hub/Switch
 Connects 2 or more LAN segments and uses data link layer
addresses (e.g.MAC addresses) to make data forwarding decisions
 Copies frames from one network to the other
 Layer 2 of the “OSI model”
Bridge/Hub/Switch
Physical 1 Physical 2
Data Link Data Link
Higher
Layers
Physical
Higher
Layers
Physical
Data Link
23-01-88-A8-77-45
Data Link
53-F1-A4-AB-67-4F
Node in Network A Node in Network B

30. Switch & Router

31. Router
 Connects 2 or more networks and uses network layer addresses
(like IP address) to make data forwarding decisions
 Layer 3 of the “OSI model”
Router
A node in Network B
Higher
Layers
Physical
Higher
Layers
PhysicalPhysical 1
Data Link
Physical 2
Data Link Data Link
A node in Network A
Data Link
Network
145.65.23.102
Network
137.22.144.6 Network Network

32. Gateway/Tunnel
 Connects 2 or more networks that can be of different types and
provides protocol conversion so that end devices with dissimilar
protocol architectures can interoperate
Gateway
137.22.144.6
145.65.23.102
Netware
TCP/IP

33. Gateway

34. • Remote Network MONitoring : to monitor the LAN

35. • Router Switch Module(RSM): A router installed as a card in a switch
to perform routing between VLANs
• Terminal Server: A specialized system that connects terminals to a
network

36. • A Digital Field Meter(DFM) monitors logical devices to diagnose
power supply, resource and temperature exceptions.
• Fan
• Temperature Sensor
• Processor
• Memory
• Power Supply
• Voltage Sensor

37. • A logical or physical component of a network device that connects
the device to a network.
• Port: A port has a MAC address but no IP address
• Interface: It may have a MAC address, an IP address, or both.

38. • VLANs are logical links
managed by DFM.
• VLAN is a logical
subgroup within LAN that
is created by software
rather than by manually
moving cables in the
wiring closet.

39. • Two parts: Client & Server

40. • A client is a single-user workstation running front-end software
that knows how to communicate with the server.
• A server is one or more multi-user processors with shared memory.
• Clients rely on servers for services.

41. • It facilitates the use of graphical user interface(GUI) available on
powerful workstations.
• It allows the acceptance of open systems because of the fact that
clients and servers can be running on different hardware and
software platforms.

42. • If a significant portion of application logic is moved to a server, the
server may become a bottleneck in the processing and distribution of
data to the clients.
• The server’s limited resources will be in ever-increasing demand by
the increasing number of resource consumers.

43. • Novel’s NetWare Operating System: supports TCP/IP protocol
• Windows NT 4.0: supports TCP/IP, IPX, also includes Internet
Information Server (IIS). IIS includes both a web server and an FTP
server.
• Windows 2000 Server: supports IP, IPX, AppleTalk
• IBM OS/2 Warp: It does not include an Internet server, but it does
have a built-in web browser and FTP client.

44. • In this model, the application and the data reside on the file server.
• When a network user needs access the application and data, both
are loaded over network onto that user’s workstation.
• Sending the application and data from the server to the workstation
puts load on the network.

46. • There are several types of physical channels through which data can
be sent from one point to another in a LAN.
• Bounded/Guided Media (Wired)
• Unbounded/Unguided Media (Wireless)
• Media differ in the capability for the following reasons:
1. Noise absorption: Susceptibility to external noise
2. Radiation: Leakage of signal
3. Attenuation: decline of magnitude of signal with distance
4. Bandwidth: transmission speed

47. • Wired media
1. Twisted-pair wire : LAN
2. Coaxial cabling : Cable TV
3. Fiber-optic cabling : Broadband

48. • two insulated copper wires (1 mm thick)
• The purpose of twisting the wires is to ensure that each wire is
equally exposed to any external electrical magnetic field that could
induce unwanted noise.
• commonly used in local telephone communication and for digital
data transmission over short distances up to 1 km. (9600 bps)

49. Insulator (Teflon in Cat 5)

50. • being the oldest method, trained manpower is easily available
• In a telephone system, signals can travel several kilometers without
amplification
• can be used for both analog and digital data transmission
• least expensive
• if a portion of a twisted-pair cable is damaged, the entire network is
not shutdown

51. • easily picks up noise signals
• thin (break easily)

52. • Category 3 : 4 pairs
• Category 5 : 4 pairs but more twisted with Teflon insulation
• Category 6 : Gigabyte Ethernet

53. • stiff (rigid) copper wire surrounded by an insulating material
• The insulator is encased within a cylindrical conductor (braided
mesh)
• The signal is transmitted by the inner copper wire

54. • Two types:
1. 50-ohm : digital transmission
2. 75-ohm : analog transmission (Cable TV)

55. Terms Implementation
10Base2 Thin Ethernet (RG-58), 10MBPS, 185m cable segment
10Base5 Thick Ethernet, 10MBPS, 500m cable segment(bus)
10BaseF Fiber-optic cable
10BaseT UTP, uses RJ-45 connectors, Star Topology, 100m length
Thick
Ethernet
0.4 inch thick, 1006m
Thin
Ethernet
0.2 inch thick, 165m, normally used for office
installation

56. • better shielding against EMI(Electromagnetic interference) than
twisted-pair cable
• can be used for both analog and digital
• higher bandwidth (noise immunity)
• more expensive than TP but easy to handle
• capable of carrying over 50 std 6MHz color TV channels

57. • Cables that employ copper conductors can easily be breached by
listening equipment.
• If the main consideration is security, then fiber cable is the only
choice to avoid espionage.

58. • newest form of bounded media
• superior in data handling and security
• transmits light signals rather than electric signals
• each fiber has an inner core of glass/plastic that conducts light

59. • total internal reflection

60. • Two light sources:
1. LEDs (Light Emitting Diodes)
2. LASERs(Light Amplification by Stimulated Emission Radiation)
Photoelectric
diodes
LED/Laser

61. • Two types:
1. Single-mode fiber (8-10µ (microns) core)
2. Multimode fiber (50µ microns core) 1µ = 10-6 m
Laser
LED

62. • Cost: more expensive than copper cable (associated equipments)
• Installation: difficult to install
• Bandwidth capacity: provides data rates from 100MBPS to 2GBPS
• Node capacity: 75 nodes
• Attenuation: much lower attenuation but has a different problem,
namely, chromatic dispersion
• EMI: immune to eavesdropping
• Mode of transmission: half duplex

64. • handle much higher bandwidth with low attenuation
• not affected by power surges, EMI or power failures
• lighter than copper cable
• do not leak light and are quite difficult to tap (excellent security)

65. • unfamiliar technology requiring skills
• Being unidirectional, two-way communication requires either two
fiber cables or two frequency bands on one fiber
• higher cost

66. Factor UTP STP Coaxial Fiber-optic
Cost Lowest Moderate Moderate Highest
Installation Easy Fairly easy Fairly easy Difficult
Bandwidth 1-155 Mbps 1-155 Mbps 100 Mbps 2 Gbps
Attenuation High (few hundred
meter)
High (few
hundred meter)
Lower (few
kilometer)
Lowest (tens of
kilometer)
EMI Most vulnerable to
EMI and
eavesdropping
Less vulnerable
than UTP
Less vulnerable
than UTP
Not affected by
EMI or
eavesdropping

67. • signals are not guided through a solid medium (Air)
• Radio wave (including VHF and microwave links)
• Satellite links
• VSATs(Very Small Aperture Terminals)
• Infrared and millimeter waves

68. • frequencies between 10 KHz and 1 GHz
• broadcast omnidirectionally or unidirectionally
• The power of the Radio Frequency (RF) signal is determined by the
antenna and trans-receiver.

69. • easy to generate
• travel long distances
• penetrate buildings easily
• omnidirectional
• At low frequency, radio waves pass through obstacles easily, but the
power falls off sharply with distance from source.
• At high frequency, radio waves tend to travel in straight lines and
bounce off obstacles.
• absorbed by rain

70. • Above 100 MHz, the waves travel in straight lines and can,
therefore, be narrowly focused.
• Concentrating all the energy into a small beam using a parabolic
antenna gives a much higher signal to noise ratio, but the
transmitting and receiving antennas must be accurately aligned with
each other.
• uses repeaters at intervals of about 25-30 km to amplify weak signal

71. • do not pass through buildings well
• Multipath Fading (delayed waves may arrive out of phase)
• The higher the towers are, the further apart they can be.

72. • transmission depends on weather and frequency. (10GHz)
• widely used for long-distance telephone communication, cellular
telephones, television distribution
• inexpensive as compared to fiber-optic system (congested area)
• 16 Gbps

73. • Two Types:
1. Terrestrial
2. Satellite

74. • use directional parabolic antennas to send and receive signals
• Relay towers and repeaters are used to extend signals
• used whenever cabling is cost-prohibitive such as in hilly areas or
crossing rivers etc.

75. • Frequency range : 4-6 GHz and 21-23 GHz
• Cost : inexpensive for short distance but expensive for long distance
• Installation: difficult due to Line-of-sight requirements
• Bandwidth capacity: 1-10 Mbps
• Attenuation: affected by atmospheric conditions (rain and fog)
• EMI: vulnerable to EMI, jamming and eavesdropping

76. • one antenna is on the satellite in geo-synchronous orbit about
36,000 km above the equator (can reach the most remote places)
• the transmitted frequency is different from the receiving frequency
to avoid interference

77. • Frequency range: 4-6 GHz and 11-14 GHz
• Cost: The cost of building and launching a satellite is extremely
high
• Installation: extremely technical and difficult
• Bandwidth capacity: 1-10 Mbps
• Attenuation: depends on frequency, power, antenna size and
atmospheric conditions. Higher frequency microwaves are more
affected by rain and fog

78. • visible from any point
• transmission and reception costs are independent of the distance
• a transmission station can receive its own transmission (testing)
• cost of placing the satellite
• a signal sent to a satellite is broadcast to all receivers within the
range (security measures need to be taken)

79. • Very Small Aperture Terminals (1m wide antennas)
• the micro-stations do not have enough power to communicate
directly with one another, hence
• a special ground station, the hub, with a large high-gain antenna is
needed to relay traffic between VSATs

80. • connect two LANs in two buildings via lasers mounted on their
roof-tops
• Coherent optical signaling using lasers is inherently unidirectional.
So, each buildings needs its own Laser and photo detector

81. • Advantages:
1. bandwidth is very high at very low cost
2. easy to install
3. does not require any license
• Disadvantages:
1. cannot penetrate rain or thick fog
2. heat from sun causes convection currents

82. • used for short-range communication (remote control in TV)
• directional, cheap and easy to build but do not pass through solid
objects
• Security if Infrared systems against eavesdropping is better than
that of radio systems
• No government license is needed (radio systems must be licensed)

83. Factor LED Laser
Data rate Low High
Mode Multimode Multimode or single-mode
Operating distance 3 Km 30 Km
Lifetime Long life Short life
Temperature sensitivity Minor Substantial
Cost Low Substantial
• Light Source: LED/Laser
• Transmission medium: Fiber-optic cable
• Detector: converter

84. • Client/Server Computer Network
• Peer-to-peer (P2P) Computer Network

85. • Two-tier architecture
• Server accepts client requests, process them and return the
requested information to the client.

86. • Characteristics of Client:
1. Activates Master Computer
2. Initiates requests
3. Waits for and receive replies
4. Connects to one or more number of servers at one time
5. Typically interacts directly with end-users using a GUI
• Characteristics of Server:
1. It waits for requests from clients
2. Upon receipt of requests, it process them and then offers replies
3. It usually accepts connections from a larger number of clients.
4. It does not interact directly with end-users.

87. Direct system exchange of resources between linked peers in
network
The most used in the world
Basically different from the Client-server architecture
• e.g. Telephony Traffic

88. Peer to peer is a type of network infrastructure where each computer is both server
and client. In this case, the computers connected to the network share their resources .
• Distributed Architecture • Decentralized architecture
88

89. In a typical peer-to-peer, there is no administrator .So, each
user manages his own post. On the other hand all users can
share their resources as they wish. If we consider one of the
posts as a server, it is intended to share resources, if not it
consumes resources from other posts
89

90. • three categories:
1. Collaborative/Distributed computing: Science and Biotech org.
2. Instant messaging: MSN Messenger or AOL (real-time chat)
3. Affinity communities: search other user’s computers for
information and files like Napster
4. Napster was the name given to two music-focused online services.
It was originally founded as a pioneering peer-to-peer file sharing
Internet service that emphasized sharing audio files, typically
music, encoded in MP3 format.

91. • each computer typically runs both client and server software
• Once you have downloas and install P2P client, you can log into a
Central Indexing Server (indexes all users who are connected to the
server means who are online)
• P2P client will contain an area where you can search for a specific
file.
• The utility queries the index server to find other connected users
with the requested file.
• Once the file download is complete, the connection will be broken.

92. • Each device in a network must have a unique address to be
identified.
• two types of addressing schemes:
1. IP (Internet Protocol) addressing : 192.168.10.51
2. DNS (Domain Name System) addressing : www.google.com

93. • two version of IP Address:
1. IPv4 : 32-bit address
2. IPv6 : 128-bit address
0-255 0-255 0-255 0-255
Octet (4) Period (3)
• two types of IP Address:
1. Static IP
2. Dynamic IP : DHCP

94. IPv4 Classes
 A, B, C : Mostly used classes
 D : Multicast
 E : Broadcast
Class Leftmost bits Start address Finish address
A 0XXX 0.0.0.0 127.255.255.255
B 10XX 128.0.0.0 191.255.255.255
C 110X 192.0.0.0 223.255.255.255
D 1110 224.0.0.0 239.255.255.255
E 1111 240.0.0.0 255.255.255.255

95. • purpose of DNS is to translate domain names into IP addresses

96. • domain name space (tree) is divided into three different sections:
1. Generic domains
2. Country domains
3. Inverse domains

97. • define registered hosts according to their generic behavior (3 chr)
Label Description
com Commercial organization
edu Educational institutions
gov Government institutions
int International organizations
mil Military groups
net Network support centers
org Nonprofit organizations

98. • 2 character country abbreviations
Label Description
us USA
in India
uk UK
ca Canada
au Australia
fr France

99. • used to map an address to a name (rDNS)

100. • HOSTS.txt was used earlier (managed by Stanford Research
Institute International (SRI)
• In 1983, Paul Mockapetris introduce the concept of DNS
• The root of DNS database on the Internet is managed by the
Internet’s Network Information Center (InterNIC).
• The top-level domains were assigned organization wise, and by
country.

101. • Workgroup (P2P) , Domain (Client/Server)
• In a domain, user accounts are defined & managed in a central
database (Security Accounts Manager)
• By default, each domain is a separate entity and do not share
information and resources.
• To allow users to access resources in another domain, you need to
establish a trust between the two domains.

102. • Topology is the method in which networks are physically connected
together.
• It determines the complexity and cost.
• Bus
• Ring
• Star
• Mesh

103. • simplest & oldest used LAN design (passive topology)
• e.g. Ethernet 10Base2 (thinnet)
• can be found in Client/Server system

104. • Advantages:
1. simple, reliable, easy to use (small-sized LANs)
2. requires least amount of cable (less expensive)
3. it is easy to extend a bus (connector)
• Disadvantages:
1. spend a lot of its bandwidth with the computers interrupting
each other instead of communicating
2. difficult to troubleshoot

105. • 1973 by Bob Metacalfe (IEEE standard called 802.3 CSMA/CD)

106. • a section of a network where data packets can collide with one
another when being sent on a shared medium
• the larger the collision domain, the more likely it is that collision
will occur

107. • Carrier Sense Multiple Access with Collision Detection

108. • a data link protocol built into the Macintosh (Apple computer)
• it forms a part of the AppleTalk protocol suite (provide file and
printer sharing services)
• AppleTalk  Network Layer

109. • active network, no termination, each node act as a repeater
• can be found in P2P networks
Nearest Active
Upstream Neighbor
Nearest Active
Downstream
Neighbor

110. • Advantages:
1. every computer is given equal access to the token
2. continues to function in a slower manner rather than fail
completely
• Disadvantages:
1. Failure of one computer affects the whole network
2. difficult to troubleshoot
3. Adding or removing computers disrupts the network

111. • IBM created IEEE 802.5 standard known as Token Ring
• it uses a special packet known as Token
• Multi-station Access Unit (MSAU)

112. • another ring-based network but implemented without hubs
• uses multimode fiber-optic cables to implement very fast, reliable
networks

113. • used as a backbone to connect LANs and computers

114. • The possessor of the token is allowed to put a new token onto the
ring as soon as it finished transmitting its frames.
Wrapping

115. • Hybrid hub can accommodate several types of cable (Hybrid Star)
• e.g. Ethernet 10BaseT
• Active Hub(regenerates & require power) and Passive Hub (not req.)

116. • Advantages:
1. easier to modify or add new computers
2. easy to troubleshoot
3. robust
4. use several types of cable
• Disadvantages:
1. if the central hub fails, the whole network fails to operate
2. cabling cost

117. • newest topology, can carry voice & data over network wire or fiber
• transmits all packets as 53-byte cells
• Quality of Service (QoS)
• extremely high-speed
(25-622Mbps or 2.488Gbps)

118. • ATM communicates with cells rather than transmitting frames.
• Instead of specifying the source and destination addresses of the
stations communicating, an ATM cell indicates the path the data will
flow through.
• every station is always transmitting (empty cells)

119. • most often used in large backbone networks in which failure of a
single switch or router can result in a large portion of a network going
down (expensive)

120. • a network that connects the computer and networks within an
organization by using the hardware and software that is used on the
Internet (TCP/IP protocol)
• secure & can have thousands of users
Intranet
(HCL)
Intranet
(Wipro)Internet
Extranet