A computer network connects devices like computers and printers. It allows nodes to exchange data and communicate. There are different types of network topologies that describe how devices are physically connected, such as bus, star, ring, and hybrid configurations. Networks also use various transmission modes like simplex, half-duplex, and full-duplex to regulate data flow directions between nodes. Selection of the right transmission medium depends on considerations like transmission rate, cost, and distance between devices.

1. Computer N/W Basics

2. WHAT IS COMPUTER NETWORK?
• A set of devices often mentioned as nodes connected by media link is
called a Network. A node can be a device which is capable of sending
or receiving data generated by other nodes on the network like a
computer, printer etc.
• A network must be able to meet certain criteria, these are mentioned
below:
 Performance
 Reliability
 Scalability
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3. Basic Communication Model
• A Communication model is used to exchange data between two
parties.
• For example: communication between a computer, server and
telephone (through modem).
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4. Line Configuration in Computer
Networks
• A Network is nothing but a connection made through connection
links between two or more devices. Devices can be a computer,
printer or any other device that is capable to send and receive data.
There are two ways to connect the devices:
 Point-to-Point connection
 Multipoint connection
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5. Point-To-Point Connection
• It is a protocol which is used as a communication link between two
devices.
• It is simple to establish.
• The most common example for Point-to-Point connection (PPP) is a
computer connected by telephone line.
• We can connect the two devices by means of a pair of wires or using a
microwave or satellite link.
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6. MultiPoint Connection
• There are two kinds of Multipoint Connections :
 If the links are used simultaneously between many devices, then it is
spatially shared line configuration.
 If user takes turns while using the link, then it is time `shared (temporal)
line configuration
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7. BUS Topology
• Bus topology is a network type in which every computer and network
device is connected to single cable.
• When it has exactly two endpoints, then it is called Linear Bus
topology
Features of Bus Topology
• It transmits data only in one direction.
• Every device is connected to a single cable 7
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8. Advantages of Bus Topology
• It is cost effective.
• Cable required is least compared to other network topology.
• Used in small networks.
• It is easy to understand.
• Easy to expand joining two cables together.
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9. Disadvantages of Bus Topology
• Cables fails then whole network fails.
• If network traffic is heavy or nodes are more the performance of the
network decreases.
• Cable has a limited length.
• It is slower than the ring topology
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10. RING Topology
• It is called ring topology because it forms a ring as each computer is
connected to another computer, with the last one connected to the
first. Exactly two neighbors for each device.
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11. Features of Ring Topology
• A number of repeaters are used for Ring topology with large number of
nodes, because if someone wants to send some data to the last node in
the ring topology with 100 nodes, then the data will have to pass
through 99 nodes to reach the 100th node. Hence to prevent data loss
repeaters are used in the network.
• The transmission is unidirectional, but it can be made bidirectional by
having 2 connections between each Network Node, it is called Dual
Ring Topology.
• In Dual Ring Topology, two ring networks are formed, and data flow is
in opposite direction in them. Also, if one ring fails, the second ring can
act as a backup, to keep the network up.
• Data is transferred in a sequential manner that is bit by bit. Data
transmitted, has to pass through each node of the network, till the
destination node.
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12. Advantages and Disadvantages
• Advantages of Ring Topology
• Transmitting network is not affected by high traffic or by adding
more nodes, as only the nodes having tokens can transmit data.
• Cheap to install and expand
• Disadvantages of Ring Topology
• Troubleshooting is difficult in ring topology.
• Adding or deleting the computers disturbs the network activity.
• Failure of one computer disturbs the whole network
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13. STAR Topology
• In this type of topology all the
computers are connected to a single
hub through a cable. This hub is the
central node and all others nodes are
connected to the central node.
• Features of Star Topology
 Every node has its own dedicated
connection to the hub.
 Hub acts as a repeater for data flow.
 Can be used with twisted pair, Optical
Fibre or coaxial cable.
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14. Advantages and Drawbacks
Advantages of Star Topology
 Fast performance with few nodes and low network traffic.
 Hub can be upgraded easily.
 Easy to troubleshoot.
 Easy to setup and modify.
 Only that node is affected which has failed, rest of the nodes can work
smoothly.
Disadvantages of Star Topology
 Cost of installation is high.
 Expensive to use.
 If the hub fails then the whole network is stopped because all the nodes
depend on the hub.
 Performance is based on the hub that is it depends on its capacity
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15. MESH Topology
• It is a point-to-point connection to other nodes or devices. All the
network nodes are connected to each other. Mesh has n(n-
1)/2 physical channels to link n devices.
• Advantages of Mesh Topology
 Each connection can carry its own data load.
 It is robust.
 Fault is diagnosed easily.
 Provides security and privacy.
• Disadvantages of Mesh Topology
 Installation and configuration is difficult.
 Cabling cost is more.
 Bulk wiring is required.
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16. TREE Topology
• It has a root node and all other nodes are connected to it forming a
hierarchy. It is also called hierarchical topology. It should at least
have three levels to the hierarchy.
• Features of Tree Topology
 Ideal if workstations are located in groups.
 Used in Wide Area Network.
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17. Advantages & Drawbacks
Advantages of Tree Topology
 Extension of bus and star topologies.
 Expansion of nodes is possible and easy.
 Easily managed and maintained.
 Error detection is easily done.
Disadvantages of Tree Topology
 Heavily cabled.
 Costly.
 If more nodes are added maintenance is difficult.
 Central hub fails, network fails.
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18. HYBRID Topology
• It is two different types of topologies,
which is a mixture of two or more
topologies.
• For example if in an office in one
department ring topology is used and
in another star topology is used,
connecting these topologies will result
in Hybrid Topology (ring topology and
star topology).
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19. Advantage and Disadvantage
Advantages of Hybrid Topology
 Reliable as Error detecting and trouble shooting is easy.
 Effective.
 Scalable as size can be increased easily.
 Flexible.
Disadvantages of Hybrid Topology
 Complex in design.
 Costly.
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20. Transmission Modes in
Computer Networks
• Transmission mode refers to the
mechanism of transferring of
data between two devices
connected over a network.
• It is also called Communication
Mode.
• These modes direct the direction
of flow of information. There are
three types of transmission
modes. They are:
 Simplex Mode
 Half duplex Mode
 Full duplex Mode
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21. Simplex Mode
• In this type of transmission mode, data can be sent only in one
direction i.e. communication is unidirectional. We cannot send a
message back to the sender.
• Examples of simplex Mode are loudspeakers, television broadcasting,
television and remote, keyboard and monitor etc.
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22. HALF DUPLEX Mode
• Half-duplex data transmission means that data can be transmitted
in both directions on a signal carrier, but not at the same time.
• Example of half duplex is a walkie- talkie in which message is sent
one at a time but messages are sent in both the directions.
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23. FULL DUPLEX Mode
• In full duplex system we can send data in both the directions as it is
bidirectional at the same time in other words, data can be sent in
both directions simultaneously
• Example of Full Duplex is a Telephone Network in which there is
communication between two persons by a telephone line, using which
both can talk and listen at the same time.
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24. Transmission Mediums in Computer
Networks
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25. Factors to be considered while
selecting a Transmission Medium
• Transmission Rate
• Cost and Ease of Installation
• Resistance to Environmental Conditions
• Distances
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26. Types of Communication Networks
Types of Communication
Networks
1. Local Area Network (LAN)
2. Metropolitan Area Network
(MAN)
3. Wide Area Network (WAN)
4. Wireless
5. Inter Network (Internet)
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27. Synchronous, Asynchronous,
Isochronous. What does it mean?
• These are all methods used to transfer streams of data
• In Synchronous Transmission, data flows in a full duplex mode in the
form of blocks or frames. Synchronization between the sender and
receiver is necessary so that the sender know where the new byte starts
(since there is no gap between the data).
• Synchronous Transmission is efficient, reliable and is used for
transferring a large amount of data. It provides real-time
communication between connected devices
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28. Asynchronous Transmission
• In Asynchronous Transmission data flows in a half-duplex mode, 1
byte or a character at a time. It transmits the data in a continuous
stream of bytes. In general, the size of a character sent is 8 bits to
which a parity bit is added i.e. a start and a stop bit that gives the
total of 10 bits.
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29. Asynchronous
• It is simple, fast, economical and does not require a 2-way
communication. Letters, emails, forums, televisions and radios are
some of the examples of Asynchronous Transmission.
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30. Isochronous
• An isochronous data transfer system combines the features of an
asynchronous and synchronous data transfer system.
• An isochronous data transfer system sends blocks of data
asynchronously, in other words the data stream can be transferred at
random intervals.
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31. Key Differences Between Synchronous
and Asynchronous Transmission
Synchronus Asynchronous
Data is transferred in the form of frames Data is transmitted 1 byte at a time
requires a clock signal between the
sender and receiver
Transmission sender and receiver does
not require a clock signal
High data transfer rate Slow data transfer rate
Complex, Expensive Simple and ecomomical
Efficient and lower overhead Overheads are more
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32. Transmission Media
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33. Transmission Media
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34. Transmission Media
• Twisted-Pair Cable
• Coaxial Cable
• Fiber-Optic Cable
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35. Twisted Pair Cable
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36. Twisted Pair Cable
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37. Twisted Pair
• Twisted-pair is a type of cabling that is used for
telephone communications and most modern Ethernet
networks.
• A pair of wires forms a circuit that can transmit data.
• The pairs are twisted to provide protection against
crosstalk, the noise generated by adjacent pairs.
• There are two basic types, shielded twisted-pair (STP)
and unshielded twisted-pair (UTP).
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38. Twisted Pair
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39. Twisted Pair
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40. Effect of noise on parallel lines
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41. Effect of noise on twisted pair
lines
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42. Unshielded Twisted Pair
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43. Unshielded Twisted Pair
• Consists of 4 pairs (8 wires) of
insulated copper wires typically about
1 mm thick.
• The wires are twisted together in a
helical form.
• Twisting reduces the interference
between pairs of wires.
• High bandwidth and High attenuation
channel.
• Flexible and cheap cable.
• Category rating based on number of
twists per inch and the material used
• CAT 3, CAT 4, CAT 5, Enhanced CAT 5
and now CAT 6.
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44. UTP Categories
• UTP comes in several categories that are based on the
number of twists in the wires, the diameter of the wires
and the material used in the wires.
• Category 3 is the wiring used primarily for telephone
connections.
• Category 5e and Category 6 are currently the most common
Ethernet cables used.
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45. Categories of UTP : CAT3
• Bandwidth 16 Mhz
• 11.5 dB Attenuation
• 100 ohms Impedance
• Used in voice applications and 10baseT (10Mbps)
Ethernet
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46. Categories of UTP: CAT 4
• 20 MHz Bandwidth
• 7.5 dB Attenuation
• 100 ohms Impedance
• Used in 10baseT (10Mbps) Ethernet
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47. Categories of UTP: CAT 5
• 100 MHz Bandwidth
• 24.0 dB Attenuation
• 100 ohms Impedance
• Used for high-speed data transmission
• Used in 10BaseT (10 Mbps) Ethernet & Fast Ethernet (100
Mbps)
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48. Categories of UTP: CAT 5e
• 150 MHz Bandwidth
• 24.0 dB Attenuation
• 100 ohms Impedance
• Transmits high-speed data
• Used in Fast Ethernet (100 Mbps), Gigabit Ethernet (1000
Mbps) & 155 Mbps ATM
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49. Categories of UTP: CAT 6
• 250 MHz Bandwidth
• 19.8 dB Attenuation
• 100 ohms Impedance
• Transmits high-speed data
• Used in Gigabit Ethernet (1000 Mbps) & 10 Gig Ethernet
(10000 Mbps)
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50. Shielded Twisted Pair (STP)
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51. 51
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52. Shielded Twisted Pair
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53. Coaxial Cable
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54. Coaxial Cable
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55. Categories of Coaxial Cable
Category Impedance Use
RG-59 75 W Cable TV
RG-58 50 W Thin Ethernet
RG-11 50 W Thick Ethernet
Radio Government (RG) rating
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56. 56
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57. BNC Connectors
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58. Fiber Optic Cable
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59. Fiber Optics
Glass or Plastic
125 um
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60. Fiber Optics
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61. Propagation Modes
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62. Modes
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63. Fiber Types
Type Core Cladding Mode
50/125 50 125 Multimode, graded-index
62.5/125 62.5 125 Multimode, graded-index
100/125 100 125 Multimode, graded-index
7/125 7 125 Single-mode
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64. Fiber Construction
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65. Fiber-optic Connectors
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66. Fiber Optic Connectors
FC connector
SC connector
ST connector
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67. Internet ??

68. What is Internet ?
• Internet is worldwide collection of computer network
• It provides access to communication services and access to
information resources to the millions of users around the globe
• Internet covers globe and include large international network as well
as many smaller local area networks owned by any individual
company or country
• M/C or computer on one network can communicate with M/C or
computer on other network and send data file and other information
back and forth, for this work M/C on network must have to agree to
speak same language
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69. Evolution of Internet:
• 1960 US Department of defence started packet switched network
ARPANET (Advanced Research Project Agency)
• WAN now known as DARPA (Defence Advanced Research Project
Agency)
• Idea was to connect different geographical areas network and allow
the transmission in the form of packets
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70. Challenges faced by ARPA
• Interconnectivity: It deals with transportation of information and
for this software protocol is needed that could package and route the
information between multiple site and
 For this internet protocol is evolved ie TCP/IP
• Interpretability deals with application-to-application
communication, its challengeous because applications are running
vastly on different hardware platform with different operating
system & different file systems.
• Solution for this is to develop standard application protocol that
would enable application to application communication and be
independent of computer platform e.g. mainframe based email
program and PC based email program both are using same standard
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71. Tim Berners Lee WWW Creator
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72. What is WWW
• The World Wide Web (WWW) is combination of all resources and
users on the Internet that are using the Hypertext Transfer Protocol
(HTTP)
• "The World Wide Web is the universe of network-accessible
information
• Sir Tim Berners-Lee invented the World Wide Web in 1989.
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73. Evolution of WWW
• WWW is huge collection of hypertext pages on the Internet
• The first text-based prototype was opeConcept WWW is developed in
Switzerland by European laboratory for particle physics (known
CERN) in the year 1989
• rational in 1991, in the month of December 1991
• Tim Berners-Lee is the inventor of the Web and the director of the
W3C
• Berners-Lee developed hypertext, the method of instant cross-
referencing that supports communications on the Web, making it
easy to link content on one web page to content located elsewhere
• The World Wide Web has been widely available since 1991
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74. Difference between Internet & WWW
• Many people use the terms Internet and World Wide Web (aka. the
Web) interchangeably
• The Internet and the Web are two separate but related things
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75. Internet
• The internet is a massive network of networks, a networking
infrastructure. It connects millions of computers together globally
 It is a global network connecting millions of computers.
 The internet is decentralized.
 Each internet computer is independent.
 There are a variety of ways to access the internet.
 There are more than 3.5 billion internet users in the world
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76. WWW
• The World Wide Web, or simply web, is a way of accessing
information over the medium of the internet.
• It is an information-sharing model that is built on top of the internet.
• The web uses the HTTP protocol, only one of the languages spoken over
the internet, to transmit data.
• It is an information-sharing model that is built on top of the internet.
• The web uses the HTTP protocol, only one of the languages spoken over
the internet, to transmit data.
 Support specially formatted documents.
 Documents are formatted in a markup language that supports links to other
documents.
 You can jump from one document to another simply by clicking on hot spots
(hyperlinks).
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77. Webserver
• A Web server is a program that uses HTTP (Hypertext Transfer
Protocol)
• Serve the files that form Web pages to users, in response to their
requests, which are forwarded by their computers' HTTP clients.
• Dedicated computers and appliances may be referred to as Web
servers as well.
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78. What is Web Browser
• A web browser (commonly referred to as a browser) is a software
application for accessing information on the World Wide Web.
• Each individual web page, image, and video is identified by a
distinct URL, enabling browsers to retrieve and display them on
the user's device.
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79. Protocols, Building Web Sites
• The Internet relies on a number of protocols in order to function
properly.
• A protocol is simply a standard for enabling the connection,
communication, and data transfer between two places on a network.
• Here are some of the key protocols that are used for transferring
data across the Internet.
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80. HTTP
• HTTP stands for Hypertext Transfer Protocol.
• It is the standard protocol for transferring web pages (and their
content) across the Internet
• For browsing website url may preceded by http://
• It is telling browser to use HTTP to transfer data
• Most browser will default to HTTP if you don’t specify it e.g.
www.bitdurg.ac.in instead ( http://www.bitdurg.ac.in)
80
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81. HTTPS
• HTTPS stands for Hypertext Transfer Protocol over Secure Socket
Layer.
• Think of it as a secure version of HTTP.
• HTTPS is used primarily on web pages that ask you to provide
personal or sensitive information (such as a password or your credit
card details).
• When you browse a web page using HTTPS, you are using SSL
(Secure Sockets Layer).
• For a website to use HTTPS it needs to have an SSL
certificate installed on the server.
• These are usually issued by a trusted 3rd party, referred to as a
Certificate Authority (CA).
81
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82. FTP
• FTP stands for File Transfer Protocol. It is used to transfer files
across the Internet.
• FTP is commonly used by web developers to publish updates to a
website (i.e. to upload a new version of the website).
• HTTP is used for displaying the file in your browser, FTP is used
simply to transfer the file from one computer to a specified location
on another computer
• You can use FTP to transfer the files from your computer to a remote
computer (such as a web server), or to transfer from the remote
computer to your local computer.
82
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83. OSI
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83

84. OSI Reference Model
• OSI Reference Model - internationally standardised network
architecture.
• OSI = Open Systems Interconnection: deals with open systems, i.e.
systems open for communications with other systems.
• Specified in ISO 7498.
• Model has 7 layers.
84
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85. 7-layer OSI Reference Model
• Layers 1-4 relate to
communications
technology.
• Layers 5-7 relate to user
applications.
Layer 7
Layer 6
Layer 5
Layer 4
Layer 3
Layer 2
Layer 1
Application Layer
Presentation Layer
Session Layer
Transport Layer
Network Layer
Data Link Layer
Physical Layer
Communications subnet boundary
85
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86. Layer – 7 Application Layer
• Level at which applications access network
services.
 Represents services that directly support software
applications for file transfers, database access, and
electronic mail etc.
86
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87. Layer 6: Presentation Layer
• Related to representation of transmitted data
 Translates different data representations from the
Application layer into uniform standard format
• Providing services for secure efficient data
transmission
 e.g. data encryption, and data compression.
87
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88. Layer 5: Session Layer
• Allows two applications on different computers to
establish, use, and end a session.
 e.g. file transfer, remote login
• Establishes dialog control
 Regulates which side transmits, plus when and how
long it transmits.
• Performs token management and
synchronization.
88
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89. Layer 4: Transport Layer
• Manages transmission packets
 Repackages long messages when necessary into
small packets for transmission
 Reassembles packets in correct order to get the
original message.
• Handles error recognition and recovery.
 Transport layer at receiving acknowledges packet
delivery.
 Resends missing packets
89
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90. Layer 3: Network Layer
• Manages addressing/routing of data within the
subnet
 Addresses messages and translates logical addresses and
names into physical addresses.
 Determines the route from the source to the destination
computer
 Manages traffic problems, such as switching, routing, and
controlling the congestion of data packets.
• Routing can be:
 Based on static tables
 determined at start of each session
 Individually determined for each packet, reflecting the
current network load.
90
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91. Layer 2: Physical Layer
 Packages raw bits from the Physical layer into frames (logical,
structured packets for data).
 Provides reliable transmission of frames
 It waits for an acknowledgment from the receiving computer.
 Retransmits frames for which acknowledgement not received
91
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92. Layer 1: Physical Layer
• Transmits bits from one computer to another
• Regulates the transmission of a stream of bits over a
physical medium.
• Defines how the cable is attached to the network
adapter and what transmission technique is used to
send data over the cable. Deals with issues like
 The definition of 0 and 1, e.g. how many volts represents
a 1, and how long a bit lasts?
 Whether the channel is simplex or duplex?
 How many pins a connector has, and what the function
of each pin is?
92
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93. Internet Protocols vs OSI
• Explicit
Presentation and
session layers
missing in Internet
Protocols
• Data Link and
Network Layers
redesigned
Application
Presentation
Session
Transport
Network
Data Link
Physical
Application
TCP
IP
Network Interface
Hardware
93
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94. Services in the OSI Model
• In OSI model, each layer provide services to layer
above, and ‘consumes’ services provided by layer
below.
• Active elements in a layer called entities.
• Entities in same layer in different machines called
peer entities.
94
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95. Novell Network
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95

96. 96
IPX/SPX
• Novell Internetwork Packet Exchange (IPX) has been
around since 1980’s.
• Novell Netware was the most popular network
operating system in 1980’s.
• Currently, Novell uses TCP/IP as default network
protocol.
• If you're not running NetWare, you probably don't
need it, and should uninstall it so that it's not taking up
bandwidth with broadcasts ..
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97. Unit-1
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97
Basic Model
Application
Computer
(Transport)
Internet
TCP/IP
Internet
IPX/SPX
Internet (IPX)
Subnet
(OSI)
OSI
Application (7)
Presentation (6)
Session (5)
Transport (4)
Network (3):
Internet &
Subnet
Data Link (2)
Application Application
Transport:
TCP, etc.
Complex:
SPX, etc.
Physical (1)
Subnet
(OSI)
Subnet
(OSI)

98. 98
IPX/SPX Protocol Stack
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99. 99
IPX/SPX Protocol Stack
• Internetwork Packet Exchange (IPX)
 Connectionless, predominantly layer 3 protocol
 Responsible for finding the best path through a multipath
IPX network
• Sequenced Packet Exchange (SPX)
 Connection-oriented layer 4 protocol
 Provides guaranteed delivery services for the connectionless
IPX
• Service Advertisement Protocol (SAP)
 Operates at layers 5, 6, and 7
 Advertises services running on IPX/SPX servers
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100. 100
IPX/SPX Protocol Stack
• NetBIOS (Network Basic Input/Output System) is a program that
allows applications on different computers to communicate in LAN
• NetWare Core Protocol (NCP)
 Functions at layers 4, 5, 6, and 7 of the OSI model
 Facilitates client/server interaction on a NetWare network
• Routing Information Protocol (RIP)
 Distance-vector protocol built into the IPX/SPX protocol stack
 Operates at layer 3
 Uses ticks and hop counts as metrics
• NetWare Link Services Protocol (NLSP)
 Link state routing protocol designed by Novell
 Functions at layer 3
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101. 101
IPX/SPX Addressing
• 80-bit (10 bytes) addresses consisting of a 32-bit
(4 bytes) network portion and a 48-bit node
portion
 The network administrator arbitrarily assigns the
network portion
 No subnetting!
 No address classes!
 MAC address of the node makes up the node portion of
the address
 Addresses normally appear in hexadecimal format
 0000.7C80.0000.8609.33e9
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102. 102
Communication
Client-Server
 Novell Netware follows a strict client-server model.
 Every Netware server builds a service advertisement
table comprising all the network resources that it is
aware of.
 Clients use Get Nearest Server (GNS) request to locate
servers.
Server-Server
 Servers use SAP and RIP.
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103. Service Advertisement Protocol (SAP)
• SAP advertisements on an IPX/SPX network allow servers to
“advertise” running services to network clients
• NetWare servers take SAP broadcasts and build SAP tables.
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103

104. Unit-1
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104

105. Unit-1
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105

106. Advantages of Novell Netware
• Increases productivity – It can improve productivity and provide
more ways to communicate with other users, as well as sharing of
resources.
• Better security features- Netware server has a dedicated workstation
with an encrypted password and the administrator does not have access
to the password
• Messaging services
Novell NetWare is also equipped with a message handling feature. This
offers ease of data transmission between several fronted applications.
• Flexibility
The operating system also offers a great deal of flexibility, as it allows
users to share multiple printers.
• Usability and configurability
Novell netware comes with easy configuration, paper documentation, as
well as electronic form,
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106

107. Present Status
• NetWare is a discontinued computer network operating
system developed by Novell, Inc.
• It initially used cooperative multitasking to run various services on a
personal computer, using the IPX network protocol.
107
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108. Unit-1
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108
IPX/SPX Summary
Developer Novell, Inc.
Working state Discontinued
Source model Closed source
Initial release 1983
Latest release 6.5 SP8 (last) / May 6, 2009
Available in English
Platforms x86, MIPS, DEC
Alpha, SPARC, PowerPC
Kernel type Hybrid kernel
Default user interface Command-line interface, Text
user interface
License Proprietary
Official website www.novell.com

109. Baseband vs Broadband
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109

110. Unit-1
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110

111. Unit-1
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111
BASIS FOR COMPARISON
BASEBAND
TRANSMISSION
BROADBAND
TRANSMISSION
Type of signaling used Digital Analog
Application Work well with bus
topology.
Used with a bus as well as
tree topology.
Encoding Used Manchester and
Differential Manchester
encoding.
PSK encoding.
Transmission Bidirectional Unidirectional
Signal range Signals can be travelled
over short distances
Signals can be travelled
over long distances without
being attenuated.

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112
Key Differences Between Baseband and Broadband Transmission
1. Baseband transmission utilizes digital signalling while broadband transmission uses
analog signalling.
2. Bus and tree topologies, both work well with the broadband transmission. On the
other hand, for the baseband transmission bus topology is suitable.
3. Baseband involves Manchester and differential manchester encoding. In contrast,
broadband does not make use of any digital encoding instead it uses PSK (Phase shift
keying) encoding.
4. The signals can be travelled in both the direction in baseband transmission whereas
in broadband transmission the signals can travel in only one direction.
5. In baseband transmission, the signals cover shorter distances because at higher
frequencies the attenuation is most pronounced which make a signal to travel short
distances without reducing its power. As against, in broadband signals, the signals
can be travelled at longer distances

113. ISDN
Integrated Services Digital Network
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113

114. • ISDN is a set of standards which define an end to end Digital
Network
• WAN Technology
ISDN (Integrated Services Digital
Network)
114
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115. • Uses Digital Signal
• Uses Existing telephone wiring
• Charges are generally based on the duration of call (How long the
WAN link was used)
• Alternate to using leased lines
• Can transport many types of Network traffic (Voice, Data, Video,
Text, Graphics etc)
• Faster Data transfer rate than modems
• Faster Call setup than Modems
Features of ISDN
115
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116. Integrated Services Digital Network
116
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117. BRI (Basic Rate Interface)
117
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118. PRI (Primary Rate Interface)
118
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119. • Terminal Equipment type 1 (TE1)
 ISDN compatible device (Router with ISDN Interface)
 TE1s connect to the ISDN network through a four-wire, twisted-
pair digital link
• Terminal Equipment type 2 (TE2)
 ISDN Non-compatible devices.
 Will require a terminal adapter.
• Terminal Adapter (TA)
 Converts standard electrical signals into the form used by ISDN
 Needed for connection with TE2 devices
 The ISDN TA can be either a standalone device or a board inside
the TE2
ISDN Components
119
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120. Functional Grouping
120
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121. • Network termination type 1 (NT1)
 Network-termination devices that connect the four-wire
 Subscriber wiring to the conventional two-wire local loop
 Is a customer premises equipment (CPE) device
• Network termination type 2 (NT2)
 Intelligent device that performs switching & concentrating.
 Provides multiple ISDN interfaces on an ISDN line.
 The NT2 may be as simple as a bridging device connected to an NT1
unit or it may be as complicated as a PBX (Private Branch exchanges)
ISDN Components
121
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122. ISDN specifies a number of reference points that define logical
interfaces between functional groupings, such as TAs and NT1s.
ISDN reference points include the following:
• R---The reference point between non-ISDN equipment and a TA.
• S---The reference point between user terminals and the NT2.
• T---The reference point between NT1 and NT2 devices.
• U---The reference point between NT1 devices and line-termination
equipment in the carrier network.
• The U reference point is relevant only in North America, where the NT1
function is not provided by the carrier network
ISDN Reference Point
122
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123. Reference points are a series of specifications that define
the connection between specific devices, depending on their
function in the end-to-end connection
ISDN Reference Point
123
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124. Reference Points
124
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125. 125
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126. ISDN Layers
126
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127. ISDN Layers for B and D Channels
• Link Access Procedure, Balanced (LAPB) implements the data link layer as defined in the X.25 protocol suite.
• Link Access Procedures, D channel is part of the network's communications protocol which ensures that messages are
error free and executed in the right sequence. 127
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128. BRI Interfaces
S interface or S reference point, also known as S0, is a User–network interface reference point
for basic rate access in an Integrated Services Digital Network (ISDN)
U interface is the electrical interface for the single twisted pair wire connection from a local phone
company (the central office) to a home or business.
It is a User–network interface reference point that is characterized by a four-wire, 144 kbit/s
(2B+D) user rate.
128
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129. S Interface
129
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130. ISDN Services
130
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131. BRI (Basic Rate Interface)
• Connection from the ISDN office to the user location provides for
access to three channels.
• The channels are two 64Kb B-channels and one 16Kb D-
channel
• The B-channels and the D-channel provide the user with access
to the circuit switched network
ISDN Services
131
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132. PRI (Primary Rate Interface)
• ISDN Primary Rate Interface service provides digital access
via a T1 line.
• A T1 line provides a 1.544 bandwidth.
• This bandwidth is divided into 24 64Kb channels.
• The ISDN PRI service uses 23 B channel access and uses the
24th (D) channel for signaling purposes
• B- Channel (Bearer Channel)
• D-channel (Delta Channel) is the channel that carries control and
signaling information.
ISDN Services
132
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133. Advantages
• To the user : cost savings and flexibility
 Integration of voice/data means users do not have to buy
multiple services to meet multiple needs
 Single access line to all services
 Services tailored to diverse requirements (information
volume, traffic pattern, response time, interface types)
133
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134. Advantages
• To network providers
 Standard support universality and larger potential market for
services, drive down equipment costs
• To manufacturers
 Larger potential market, economies of scales standards decrease
risk of obsolescence
• To enhanced service providers
 Simplified user access
134
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135. ATM (Asynchronous Transfer Mode)
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135

136. ATM
• ATM stands for Asynchronous Transfer Mode.
• ATM is dedicated-connection oriented switching technology
• Organizes digital data into 53-byte cell :5 byte header and 48 byte payload.
• Transmits them over a physical medium using digital signal
• Speeds on ATM networks can reach 10 Gbps
• Uses time division multiplexing (TDM) for data communications.
• It encodes data into small fixed - size cells so that they are suitable for TDM
and transmits them over a physical medium.
• There are two different cell formats - user-network interface (UNI) and
network-network interface (NNI).
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136

137. ATM ..
• Multi-speed network environment that provides a variety of complex
network services
• Can carry voice, data, video separately or simultaneously
• Can be used in LANs, MANs, or WANs
• Allows multiple logical connections to be multiplexed
• Minimal error and flow control capabilities
• Connection-oriented virtual channel
• Fixed-length packets (cells)
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137

138. A/D AAL
Voice
s1 , s2 …
Digital voice samples
cells
AAL
Data
Bursty variable-length
packets
cells
A/D AAL
Video
… Compression
compressed
frames
picture
frames
cells
138
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139. MUX
`
Wasted bandwidth
ATM
TDM
4 3 2 1 4 3 2 1 4 3 2 1
4 3 1 3 2 2 1
Voice
Data packets
Images
Asynchronous Transfer Mode (ATM)
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139

140. Unit-1
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140
Fig. Asynchronous multiplexing of ATM
Fig. Normal TDM operation

141. ATM benefits / Advantages
• It provides the dynamic bandwidth that is particularly suited for bursty
traffic.
• Since all data are encoded into identical cells, data transmission is simple,
uniform and predictable.
• Uniform packet size ensures that mixed traffic is handled efficiently.
• Small sized header reduces packet overload, thus ensuring effective
bandwidth usage.
• ATM networks are scalable both in size and speed.
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141

142. 142
ATM Ref Model / Protocol Architect
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143. AAL
ATM
User
information
User
information
AAL
ATM
PHY
PHY
ATM
PHY
ATM
PHY
…
End system End system
Network
143
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144. Physical Layer:
• This layer corresponds to physical layer of OSI model.
• At this layer, the cells are converted into bit streams and
transmitted over the physical medium.
• This layer has two sub layers: PMD sub layer (Physical Medium
Dependent) and TC (Transmission Convergence) sub layer.
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144

145. ATM Layer:
• Similar to data link layer of OSI model.
• It accepts the 48 byte segments from the upper layer, adds a 5 byte
header to each segment and converts into 53 byte cells.
• This layer is responsible for routing of each cell, traffic management,
multiplexing and switching.
ATM Adaptation Layer (AAL):
• Similar to network layer of OSI model.
• It provides facilities to the existing packet switched networks to connect
to ATM network and use its services.
• It accepts the data and converts them into fixed sized segments.
• The transmissions can be of fixed or variable data rate.
• This layer has two sub layers: Convergence sub layer and Segmentation
and Reassembly sub layer.
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145

146. ATM endpoints:
• It contains ATM network interface adaptor.
• Examples of endpoints are workstations, routers, CODECs, LAN
switches, etc.
ATM switch :
• It transmits cells through the ATM networks.
• It accepts the incoming cells from ATM endpoints (UNI) or another
switch (NNI),
• updates cell header and retransmits cell towards destination
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146

147. ATM Routers & Switches
147
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148. 148
UNI/NNI Interface
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149. 149
ATM Cells
• Fixed size – 53 bytes
• 5 octet header
• 48 octet information field
• Small cells reduce queuing delay for high priority cells
• Small cells can be switched more efficiently
• Easier to implement switching of small cells in hardware
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D.
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Mishra
BITD

150. ATM Cell Format
150
Unit-1
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151. 151
Header Format
• Generic flow control
 Only at user to network interface
 Controls flow only at this point
• Virtual path identifier
• Virtual channel identifier
• Payload type
 e.g. user info or network management
• Cell loss priority
• Header error control
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152. 152
Generic Flow Control (GFC)
• Control traffic flow at user to network interface (UNI) to alleviate
short term overload
• Two sets of procedures
 Uncontrolled transmission
 Controlled transmission
• Every connection either subject to flow control or not
• Flow control is from subscriber to network
 Controlled by network side
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153. 153
Virtual Connections
• Virtual Channel Connection (VCC) – Full duplex virtual
circuit with logical connection between source and
destination
• Virtual Path Connection (VPC) – Semi-permanent (or
customer controlled or network controlled) connection
• VPC provides a logical collection of virtual channels that
have the same endpoint
• A single virtual path supports multiple virtual channels
(analogy – highway = VPC, lane = VCC)
Unit-1
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154. 154
VCI vs VPI
• VPI – Virtual Path Identifier – identified in cell’s header.
• Cannot establish a virtual channel before virtual path
• VCI – Virtual Channel Identifier – only have local
significance – different virtual paths
• Reuse VCIs (but VCIs on same path must be unique)
Unit-1
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BITD

155. 155
What is so special about a virtual
path?
• ATM is connection-oriented, so circuit must be
established before transmission
 As route established, VPIs and VCIs are assigned
• VPI and VCI info suffices for addressing info
• Simplified network architecture (based on VC or VP)
• Reduces processing and short connection setup time
Unit-1
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Prof.
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Mishra
BITD

156. 156
ATM Connection Relationships
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157. 157
Why is ATM so Efficient?
• Minimal error and flow control
 Reduces overhead of processing ATM cells
 Reduces number of required overhead bits
• Fixed size simplified processing at each ATM node (can be
switched more efficiently – more efficient use of router)
• Small cells reduce queuing delay
• Minimal addressing info on each cell
• Efficient traffic management
Unit-1
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BITD

158. 158
Review Questions
• Describe the basic characteristics of ATM
• Explain the relationship between UNI and NNI interfaces
• What is the difference between a virtual channel and a virtual path?
• What are the advantages of the use of virtual paths?
• What are the characteristics of a virtual channel connection?
• What are the characteristics of a virtual path connection?
• Define the following terms: QOS, COS, CBR, VBR, UBR, GFR, PCR, MCR
• Compare and contrast two methods of transmitting ATM cells.
• How does ATM differ from Frame Relay
• What are the relative advantages of ATM compared to frame relay?
• How does ATM differ for SONET?
• Discuss why ATM is so efficient.
Unit-1
Comp
Network
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Prof.
D.
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Mishra
BITD

159. Questions Appeared in
University Papers
Unit-1
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159

160. April May 2015
1. What is the maximum length allowed for a UTP cable ?
2. Compare Guided and unguided media
3. Give a brief description of PAN, LAN, HAN, SAN, CAN, MAN,
WAN, GAN
4. What are the different design goals of ATM
Unit-1
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160

161. April May 2016:
1. What is peer to peer communication ? What are the various
applications of computer networks ?
2. Explain the layered architecture of OSI model
3. What are the services of physical layer ? Also explain the
hardware protocol for computer network
4. Compare OSI and TCP model
Unit-1
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161

162. April May 2017
1. What is Topology ?
2. What is ISDN ? Explain with block diagram for broadband ISDN.
3. Explain ISO/OSI Reference model
4. What is switching ? Explain circuit switching, packet switching
and message switching
Unit-1
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162

163. April May 2018
1. Classify transmission media
2. Explain OSI Model
3. Compare LAN, MAN, WAN
4. Explain Novells' IPS/SPX protocol Stack
Unit-1
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163