Computer Networks - 21CS52 - VTU Notes - Module 1

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Department ofInformation Science Engineering
Computer Networks Module 1
Dr Loganathan D Professor
www.cambridge.edu.in
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21CS32 - Computer Networks -Course Outcomes
(Course Skill Set)
At the end of the course the student will be able
to CO 1. Learn the basic needs of
communication system. CO 2. Interpret the
communication challenges and its solution. CO 3.
Identify and organize the communication system
network components CO 4. Design communication
networks for user requirements
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21CS32 - Computer Networks - Syllabus
Module 1 Introduction to networks Network
hardware, Network software, Reference models.
Physical Layer Guided transmission media,
Wireless transmission. Module 2 The Data link
layer Design issues of DLL, Error detection and
correction, Elementary data link protocols,
Sliding window protocols. The medium access
control sublayer The channel allocation problem,
Multiple access protocols.
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21CS32 - Computer Networks - Syllabus
Module 3 The Network Layer Network Layer Design
Issues, Routing Algorithms, Congestion Control
Algorithms, QoS. Module 4 The Transport Layer
The Transport Service, Elements of transport
protocols, Congestion control, The internet
transport protocols. Module 5 Application
Layer Principles of Network Applications, The
Web and HTTP, Electronic Mail in the Internet,
DNSThe Internets Directory Service.
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21CS32 - Computer Networks

• Laboratory Component
• Implement three nodes point to point network
  with duplex links between them for different
  topologies. Set the queue size, vary the
  bandwidth, and find the number of packets dropped
  for various iterations.
• Implement simple ESS and with transmitting nodes
  in wire-less LAN by simulation and determine the
  throughput with respect to transmission of
  packets.
• Write a program for error detecting code using
  CRC-CCITT (16- bits).
• Implement transmission of ping messages/trace
  route over a network topology consisting of 6
  nodes and find the number of packets dropped due
  to congestion in the network.
• Write a program to find the shortest path between
  vertices using bellman-ford algorithm.
• Implement an Ethernet LAN using n nodes and set
  multiple traffic nodes and plot congestion window
  for different source / destination.
• Write a program for congestion control using
  leaky bucket algorithm.

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21CS32 - Computer Networks - Books
Textbooks 1. Computer-Networks- Andrew S.
Tanenbaum and David J. Wetherall, Pearson
Education, 5th-Edition. (www.pearsonhighered.com/t
anenbaum) 2. Computer Networking A Top-Down
Approach -James F. Kurose and Keith W.
RossPearson Education 7th Edition. Reference
Books 1. Behrouz A Forouzan, Data and
Communications and Networking, Fifth Edition,
McGraw Hill,Indian Edition 2. Larry L Peterson
and Brusce S Davie, Computer Networks, fifth
edition, ELSEVIER
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21CS32 - Computer Networks - Syllabus

• Module 1
• Introduction to networks
• Network hardware, Network software,
• Reference models.
• Physical Layer
• Guided transmission media,
• Wireless transmission.

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21CS32 - Computer Networks
Networks hardware

• Computer network refers to interconnected
  computing devices that can exchange data and
  share resources with each other. These networked
  devices use a system of rules, called
  communications protocols, to transmit information
  over physical/wired or wireless technologies.

Wired Communication
Wireless
Communication
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Module 1 - Introduction to networks
Networks hardware

• Computer networks components comprise both
  physical parts as well as the software required
  for installing computer networks, both at
  organizations and at home.
• The hardware components are, the server, client,
  peer, transmission medium, and connecting
  devices.
• A server is a computer program or device that
  provides a service to another computer program
  and its user, also known as the client. The
  network operating system is typically installed
  in the server and so they give user accesses to
  the network resources.
• Clients are computers that request and receive
  service from the servers to access and use the
  network resources.
• A peer is any device that participates in a
  network and has the same functionality as one or
  more devices in the network.

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Module 1 - Introduction to networks
Networks hardware

• Transmission media is basically divided into two
  categories of Transmission Technology  
• 1.Broadcast Link and 2. Point-to-Point Link.
• Broadcast Link  Broadcast networks are also
  known as terrestrial networks. It is basically a
  group of radio stations, television stations, or
  any other electronic media outlets that simply
  generate agreement to air, or broadcast, content
  generally from a centralized source.
• Broadcasting is simply a method of transferring
  messages to all the recipients simultaneously.

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Module 1 - Introduction to networks
Networks hardware

• Transmission media is basically divided into two
  categories  
• 1.Broadcast Links, 2. Point-to-Point Link.
• Point-to-Point Link In Point-to-Point
  configuration, there is a line (link) that is
  fully dedicated to carrying the data between two
  devices.
• Direct serial wired connections or wireless
  connections(infrared) between two computers.
• Communication can be full-duplex or half-duplex.

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Module 1 - Introduction to networks
Networks hardware
Casting in computer networks

• Casting in computer networks means transmitting
  data (stream of packets) over a network.
• There are 3 types of casting in data
  transmission.
• 1. Unicast transmission
• 2. Multicast transmission
• 3. Broadcast transmission
• Unicast, Multicast, Broadcast happen at layer 2
  (Data Link Layer Using MAC address) and layer 3
  (Network layer Using IP Address).

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Module 1 - Introduction to networks
Networks hardware
Unicast Transmission (One-to-One) In Unicast
transmission, the data is transferred from a
single sender (or a single source host) to a
single receiver (or a single destination host).
Data is sent to a single recipient. Email, file
transfer.
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Module 1 - Introduction to networks
Networks hardware
Multicast A communication where a message is
sent from one sender to a group of receivers.
Data is sent to a group of recipients. Video
streaming, online gaming.
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Module 1 - Introduction to networks
Networks hardware
Broadcast A communication where a message is
sent from one sender to all receivers. Data is
sent to all recipients in a network. DHCP
requests, ARP (Address Resolution Request)
requests.
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Module 1 - Introduction to networks
Networks hardware
Connection-oriented service and Connection-less
service

• Both Connection-oriented service and
  Connection-less service are used for the
  connection establishment between two or more two
  devices. These types of services are offered by
  the network layer. Connection-oriented service is
  related to the telephone system.
• It includes connection establishment and
  connection termination. In a connection-oriented
  service, the Handshake method is used to
  establish the connection between sender and
  receiver. 

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Module 1 - Introduction to networks
Networks hardware
Connection-oriented service and Connection-less
service

• Connection-less service is related to the postal
  system. It does not include any connection
  establishment and connection termination.
  Connection-less Service does not give a guarantee
  of reliability. In this, Packets do not follow
  the same path to reach their destination. 

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Module 1 - Introduction to networks
Networks hardware
Transmission medium

• Transmission medium is a communication channel
  that carries the information from the sender to
  the receiver. Data is transmitted through the
  electromagnetic signals.
• The main functionality of the transmission media
  is to carry the information in the form of bits
  through LAN(Local Area Network).
• Connecting devices
• Repeater  A repeater operates at the physical
  layer. Its job is to regenerate the signal over
  the same network before the signal becomes too
  weak.
• A hub is a basically multi-port repeater. A hub
  connects multiple wires coming from different
  computers. 
• A bridge operates at the data link layer. It is
  also a repeater, with add on the functionality of
  filtering content by reading the MAC addresses of
  the source and destination. It is also used for
  interconnecting two LANs working on the same
  protocol.

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Module 1 - Introduction to networks
Networks hardware
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Module 1 - Introduction to networks
Networks hardware

• The Network allows computers to connect and
  communicate with different computers via any
  medium or Network hardware with classic Ethernet
  cables.
• There are several types of Computer Networks.
• LAN (Local Area Network)
• MAN (Metropolitan Area Network)
• WAN (Wide Area Network)
• PAN (Personal Area Network)
• SAN (Storage Area Network)
• EPN (Enterprise Private Network)
• VPN (Virtual Private Network)

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Module 1 - Introduction to networks
Networks hardware

• LAN (Local Area Network)
• Local Area Network is a group of computers
  connected to each other in a small area such as
  building, office.
• LAN is used for connecting two or more personal
  computers through a communication medium such as
  twisted pair, coaxial cable, etc.
• The data is transferred at an extremely faster
  rate in Local Area Network.
• Local Area Network provides higher security.
• Early LANs had data rates in the 4 to 16 Mbps
  range. Nowadays, speeds are normally 100 or 1000
  Mbps.

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Module 1 - Introduction to networks
Networks hardware

• MAN (Metropolitan Area Network)
• A metropolitan area network is a network that
  covers a larger geographic area by
  interconnecting a different LAN to form a larger
  network.
• In MAN, various LANs are connected to each other
  through a telephone exchange line.
• The most widely used protocols in MAN are RS-232,
  Frame Relay, Asynchronous Transfer Mode(ATM),
  Integrated Services Digital Network (ISDN), OC-3
  (Optical Carrier 3. The '3' refers to the speed
  an OC3 line is three times as fast as an OC1
  line), Asymmetric Digital Subscriber Line (ADSL),
  etc.
• It has a higher range than Local Area
  Network(LAN).

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Module 1 - Introduction to networks
Networks hardware

• WAN (Wide Area Network)
• A Wide Area Network is a network that extends
  over a large geographical area such as states or
  countries.
• A Wide Area Network is quite bigger network than
  the LAN.
• A Wide Area Network is not limited to a single
  location, but it spans over a large geographical
  area through a telephone line, fibre optic cable
  or satellite links.
• The internet is one of the biggest WAN in the
  world.
• There are two types of WAN Switched WAN and
  Point-to-Point WAN. WAN is difficult to design
  and maintain

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Module 1 - Introduction to networks
Networks hardware

• PAN (Personal Area Network)
• Personal Area Network is a network arranged
  within an individual person, typically within a
  range of 10 meters or 30 feet range.
• Personal Area Network is used for connecting the
  computer devices of personal use is known as
  Personal Area Network.
• Thomas Zimmerman was the first research scientist
  to bring the idea of the Personal Area Network.
• The personal area network are the laptop, mobile
  phones, media player and play stations which
  connected for personal use.

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Module 1 - Introduction to networks
Networks hardware

• SAN (Storage Area Network)
• A Storage Area Network is a specialized,
  high-speed network that provides network access
  to storage devices.
• SANs are typically composed of hosts, switches,
  storage elements, and storage devices that are
  interconnected using a variety of technologies,
  topologies, and protocols.
• A SAN presents storage devices to a host such
  that the storage appears to be locally attached.
  This simplified presentation of storage to a host
  is accomplished through the use of different
  types of virtualization.

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Module 1 - Introduction to networks
Networks hardware

• EPN (Enterprise Private Network)
• Enterprise networking refers to the creation and
  management of a group of interconnected computer
  systems that serve the needs of a large business.
  
• It involves the use of local area networks (LANs)
  that connect to wide area networks (WANs) and the
  cloud to facilitate data exchange, business
  processes, and analysis of network activity.
• In an enterprise environment, various components,
  including data centers, branch offices, public
  and private clouds, Internet of Things (IoT)
  devices, and employees, require reliable network
  connections.

PSTN Public Switched Telephone Network Telco -
Telecommunication networks
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Module 1 - Networking
Networks hardware

• VPN (Virtual Private Network)
• A virtual private network, or VPN, is an
  encrypted connection over the Internet from a
  device to a network.
• The encrypted connection helps ensure that
  sensitive data is safely transmitted.
• It prevents unauthorized people from
  eavesdropping on the traffic and allows the user
  to conduct work remotely.  
• VPN technology is widely used in corporate
  environments.

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Module 2 - Networking
Networks hardware

• Internetworks
• The maximum size of a message that the networks
  can transmit.
• This leads to mechanisms for disassembling,
  transmitting, and then reassembling messages.
• Networks with each router makes the decision as
  to where to
• send a packet next is called the forwarding
  algorithm.
• Many such forwarding algorithm designed as
  routing algorithm and exist.
• This overall function is called internetworking
  or Internetworks or Internet

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Module 1 - Networking
Networks hardware

• The Internet
• The Internet is not really a network at all, but
  a vast collection of different
• networks that use certain common protocols and
  provide certain common services.
• Internet Service Provider, or simply ISP, from
  who the user purchases Internet access or
  connectivity.
• This lets the computer exchange packets.
• The ARPANET - Advanced Research Projects Agency
  Network US Defence
• NSFNET - National Science Foundation Network US
• ANSNET (Advanced Networks and Services Network)

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Module 1 - Introduction to networks

• A switch is a multiport bridge with a buffer and
  a design that can boost its and performance. A
  switch is a data link layer device. 
• A router is a device like a switch that routes
  data packets based on their IP addresses. The
  router is mainly a Network Layer device. Routers
  normally connect LANs and WANs and have a
  dynamically updating routing table based on which
  they make decisions on routing the data packets. 
• A gateway, as the name suggests, is a passage to
  connect two networks that may work upon different
  networking models.
• NIC or network interface card is a network
  adapter that is used to connect the computer to
  the network. It is installed in the computer to
  establish a LAN. 

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Module 1 - Networking
Networks hardware
Internet overall view
DSL - Digital Subscriber Line/Loop IXP -
Internet exchange point FTTH - Fiber to the
Home CMTS Cable Modem Termination System DSLAM
- Digital Subscriber Line Access Multiplexer How
two different networks can be connected? The
general name for a machine that makes a
connection between two or more networks and
provides the necessary translation, both in terms
of hardware and software, is a gateway.
Gateways are distinguished by the layer at which
they operate in the protocol hierarchy.
gateway
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Module 2 - Networking
Network Software

• Network software
• Network software is now highly structured. In the
  following sections we examine the software
  structuring technique in some detail.
• Protocol Hierarchies
• To reduce their design complexity, most networks
  are organized as a stack of
• layers or levels, each one built upon the
  one below it.
• The number of layers, the name of each layer, the
  contents of each layer, and the function of each
  layer differ from network to network.
• When layer n on one machine carries on a
  conversation with layer n on another machine, the
  rules and conventions used in this conversation
  are collectively known as the layer n protocol.
• Basically, a protocol is an agreement between the
  communicating parties on how communication is to
  proceed.

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layer 1 is the physical medium through which
actual communication occurs. virtual
communication is shown by dotted lines (Protocol)
and physical communication by solid lines
(Interface). Between each pair of adjacent
layers is an interface.
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M- Message H Header T Transmission Line
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Module 1 - Introduction to networks
Network Software

• Design Issues for the Layers
• A set of layers and protocols is called a network
  architecture.
• A list of the protocols used by a certain system,
  one protocol per layer, is called a protocol
  stack.
• What are the Design Issues
• Error Detection Correction, Routing, Protocol
  layering, Addressing and naming, Internetworking,
  Flow control, Congestion, Real time transmission,
  Quality of Service and data integrity

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Module 1 - Introduction to networks
Network Software

• Design Issues for the Layers
• One mechanism for finding errors in received
  information uses codes for error detection until
  it is received correctly.
• More powerful codes allow for error correction,
  where the correct message is
• recovered from the possibly incorrect bits
  that were originally received.
• One of the important issue is finding a path
  through a network. The network should
  automatically make this decision to route/path
  the packets called routing.
• A second design issue concerns the evolution of
  the network and its required protocol layering
  for interface with each other protocols.

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Module 1 - Introduction to networks
Network Software

• Design Issues for the Layers
• Since there are many computers on the network,
  every layer needs a mechanism for identifying the
  senders and receivers that are involved in a
  particular message.
• This mechanism is called addressing or naming, in
  the low and high layers,
• respectively.
• Another example is differences in the maximum
  size of a message that the networks can transmit.
  This leads to mechanisms for disassembling,
  transmitting, and then reassembling messages.
  This overall topic is called internetworking.

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Module 1 - Introduction to networks
Network Software

• Design Issues for the Layers
• A third design issue is resource allocation.
  Networks provide a service to
• hosts from their underlying resources, such
  as the capacity of transmission
• lines.
• Sharing the resources via the design is called
  statistical multiplexing, meaning sharing based
  on the statistics of demand like bandwidth
  sharing.
• An allocation problem that occurs at every level
  is how to keep a fast sender
• from swamping a slow receiver with data.
• Feedback from the receiver to the sender is often
  used. This subject is called flow control.

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Module 1 - Introduction to networks
Network Software

• Sometimes the problem is that the network is
  oversubscribed because too many computers want to
  send too much traffic, and the network cannot
  deliver it all.
• This overloading of the network is called
  congestion.
• Real-time delivery at the same time is important.
• Quality of service is also important with respect
  to network throughput.
• The last major design issue is to secure the
  network by defending it against
• different kinds of threats.
• Data integrity no manipulation on data while
  transmission - provide confidentiality defend
  against any threats. Mechanisms for
  authentication prevent someone from imitating
  someone else.

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Module 1 - Introduction to networks
Network Software
Connection-Oriented Versus Connectionless Service
request-reply service With Acknowledged Datagram
connectionless service is often called datagram
service
Six different types of service.
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Module 1 - Introduction to networks
Network Software
Connection-Oriented Versus Connectionless Service

• Connection oriented Services
• Requires the establishment of a connection before
  data transfer.
• TCP (Transmission Control Protocol) is a
  prominent example of a connection-oriented
  protocol.
• Implements flow control mechanisms to manage the
  rate of data transmission.
• Offers a reliable communication channel with
  error checking and correction mechanisms.
• Connectionless Oriented Services
• Does not require a pre-established connection
  before data transmission.
• UDP (User Datagram Protocol) is a common
  connectionless protocol.
• Provides no guarantee of reliable data delivery.
• Error checking may be minimal or absent.

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Module 1 - Introduction to networks
Network Software
Connection-Oriented Versus Connectionless Service

• Service is formally specified by a set of
  primitives (operations) available to
• user processes to access the service.

Service Primitives
Six Service Primitives
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Module 1 - Introduction to networks
Network Software
Connection-Oriented Versus Connectionless Service
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Module 1 - Introduction to networks
Network Software

• The Relationship of Services to Protocols
• Service
• A service is a set of primitives (operations)
  that a layer provides to the layer above it. A
  service relates to an interface between two
  layers, with the lower layer being the service
  provider and the upper layer being the service
  user.
• Protocol
• A protocol, in contrast, is a set of rules
  governing the format and meaning of
• the packets, or messages that are exchanged
  by the peer entities within a
• layer. Entities use protocols to implement
  their service definitions.

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Module 1 - Introduction to networks
Network Software

• Services to Protocols - Implementations
• A service is like an abstract data type or an
  object in an object-oriented language.
• It defines operations that can be performed on an
  object but does not specify how these operations
  are implemented.
• In contrast, a protocol relates to the
  implementation of the service and as such is not
  visible to the user of the service.

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Module 1 - Introduction to networks
Network Software
Services and protocols are distinct concepts.

• The service defines what operations the layer is
  prepared to perform on behalf of its users.
• A protocol, in contrast, is a set of rules
  governing the format and meaning of the packets,
  or messages that are exchanged by the peer
  entities within a layer. 

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Module 1 - Introduction to networks
Reference Models
Protocol Stock OSI Model and TCP/IP Model
Required protocols supports for Service to
communicate the data
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Module 1 - Introduction to networks
Reference Models

• The software components are operating system and
  protocols.
• Networking Operating System - It is typically
  installed in the server and facilitate
  workstations in a network to share files,
  database, applications, printers etc.
• Protocol Suite - A protocol is a rule or
  guideline followed by each computer for data
  communication. The two popular protocol suites
  are -              
• a. OSI Model ( Open System Interconnections)
• b. TCP / IP Model.
• We will discuss two important network
  architectures the OSI reference model and the
  TCP/IP reference model.

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Module 1 - Introduction to networks
Reference Models

• OSI or Open System Interconnection model was
  developed by International Standards Organization
  (ISO).
• It is a reference model that describes how
  information from a software application in one
  computer moves through a physical medium to the
  software application in another computer.
• It gives a layered networking framework that
  conceptualizes how communication should be done
  between heterogeneous systems. It has seven
  interconnected layers.
• The seven layers of the OSI Model are,
• a physical layer, data link layer, network layer,
  transport layer, session layer, presentation
  layer, and application layer.
• The hierarchy is depicted in the given figure

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Module 1 - Introduction to networks
Reference Models
OSI Model APS in TN DP
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Module 1 - Introduction to networks
Reference Models
The upper layer mainly deals with the application
related issues, and they are implemented only in
the software. 
The lower layer of the OSI model deals with the
data transport issues.
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Reference Models
Three concepts are central to the OSI model 1.
Services/functions 2. Interfaces. 3. Protocols.
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Module 1 - Introduction to networks
Reference Models
The upper layer mainly deals with the application
related issues, and they are implemented only in
the software. 
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Module 1 - Introduction to networks
Reference Models
RJ45, stands for Registered Jack-45. The term
RJ45 has also come to refer to a range of
connectors for Ethernet jacks
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Module 1 - Introduction to networks
Reference Models
1. Functions of Physical Layer
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Module 1 - Introduction to networks
Reference Models
1. Functions of Physical Layer
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Module 1 - Introduction to networks
Reference Models
Functions of a Physical layer Line
Configuration It defines the way how two or more
devices can be connected physically. Data
Transmission It defines the transmission mode
whether it is simplex, half-duplex or full-duplex
mode between the two devices on the
network. Topology It defines the way how network
devices are arranged. Signals It determines the
type of the signal used for transmitting the
information.
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Module 1 - Introduction to networks
Reference Models
2. Functions of Data Link Layer
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Module 1 - Introduction to networks
Reference Models
2. Functions of Data Link Layer
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Basics of Computer Networks
Reference Models
IP address and MAC Address
When a computer joins a network, the network
assigns a special number called an IP address to
the computer. Without an IP address, the computer
will not be able to use the network. An IPv4
address looks like this 192.168.1.14 A MAC
address is a 48 or 64 bit number and is used by a
network to identify the computer. Every time a
computer needs to send or receive data, the MAC
address is used to direct the traffic. MAC
addresses are linked to the hardware
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Module 1 - Introduction to networks
Reference Models
2. Functions of Data Link Layer
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Module 1 - Introduction to networks
Reference Models
2. Functions of Data Link Layer a) Access
Media and b)data is placed
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Module 1 - Introduction to networks
Reference Models
2. Functions of Data Link Layer
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Module 1 - Introduction to networks
Reference Models
Functions of a Data Link Layer Framing The data
link layer translates the physical's raw bit
stream into packets known as Frames. The Data
link layer adds the header and trailer to the
frame. The header which is added to the frame
contains the hardware destination and source
address. Physical Addressing The Data link layer
adds a header to the frame that contains a
destination address. The frame is transmitted to
the destination address mentioned in the header.
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Module 1 - Introduction to networks
Reference Models
Flow Control Flow control is the main
functionality of the Data-link layer. It is the
technique through which the constant data rate is
maintained on both the sides so that no data get
corrupted. It ensures that the transmitting
station such as a server with higher processing
speed does not exceed the receiving station, with
lower processing speed. Error Control Error
control is achieved by adding a calculated value
CRC (Cyclic Redundancy Check) that is placed to
the Data link layer's trailer which is added to
the message frame before it is sent to the
physical layer. If any error seems to occur, then
the receiver sends the acknowledgment for the
retransmission of the corrupted frames. Access
Control When two or more devices are connected
to the same communication channel, then the data
link layer protocols are used to determine which
device has control over the link at a given time.
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3. Functions of Network Layer
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Functions of Network Layer Internetworking An
internetworking is the main responsibility of the
network layer. It provides a logical connection
between different devices. Addressing A Network
layer adds the source and destination address to
the header of the frame. Addressing is used to
identify the device on the internet. Routing
Routing is the major component of the network
layer, and it determines the best optimal path
out of the multiple paths from source to the
destination. Packetizing A Network Layer
receives the packets from the upper layer and
converts them into packets. This process is known
as Packetizing. It is achieved by internet
protocol (IP).
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3. Functions of Network Layer
A subnet mask defines the range of IP addresses
that can be used within a network or subnet. 
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3. Functions of Network Layer
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3. Functions of Network Layer
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4. Functions of Transport Layer
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Functions of Transport Layer Service-point
addressing Computers run several programs
simultaneously due to this reason, the
transmission of data from source to the
destination not only from one computer to another
computer but also from one process to another
process. The transport layer adds the header that
contains the address known as a service-point
address or port address. The responsibility of
the network layer is to transmit the data from
one computer to another computer. The
responsibility of the transport layer is to
transmit the message to the correct process.
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Segmentation and reassembly When the transport
layer receives the message from the upper layer,
it divides the message into multiple segments,
and each segment is assigned with a sequence
number that uniquely identifies each segment.
Connection control Transport layer provides two
services Connection-oriented service and
connectionless service. A connectionless service
treats each segment as an individual packet, and
they all travel in different routes to reach the
destination. In connection-oriented service, all
the packets travel in the single route.
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Flow control The transport layer also
responsible for flow control but it is performed
end-to-end rather than across a single
link. Error control The transport layer is also
responsible for Error control. Error control is
performed end-to-end rather than across the
single link. The sender transport layer ensures
that message reach at the destination without any
error.
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4. Functions of Transport Layer - Flow control
and error control
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4. Functions of Transport Layer - Flow control
and error control
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5. Functions of Session Layer
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Functions of Session layer Dialog control
Session layer acts as a dialog controller that
creates a dialog between two processes or we can
say that it allows the communication between two
processes which can be either half-duplex or
full-duplex. Synchronization Session layer adds
some checkpoints when transmitting the data in a
sequence. If some error occurs in the middle of
the transmission of data, then the transmission
will take place again from the checkpoint. This
process is known as Synchronization and
recovery. Authentication, Authorization and
Session Management of Text and contain image file
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5. Functions of Session Layer
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6. Functions of Presentation layer
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Functions of Presentation layer Translation The
processes in two systems exchange the information
in the form of character strings, numbers and so
on. Different computers use different encoding
methods, the presentation layer handles the
interoperability between the different encoding
methods. It converts the data from
sender-dependent format into a common format and
changes the common format into receiver-dependent
format at the receiving end. Encryption
Encryption is needed to maintain privacy.
Compression Data compression is a process of
compressing the data. Data compression is very
important in multimedia such as text, audio,
video.
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6. Functions of Presentation layer
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7. Functions of Application layer
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Functions of Application layer File transfer,
access, and management (FTAM) An application
layer allows a user to access the files in a
remote computer, to retrieve the files from a
computer and to manage the files in a remote
computer. Mail services An application layer
provides the facility for email forwarding and
storage. Directory services An application
provides the distributed database sources and is
used to provide that global information about
various objects.
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Protocols used in Application layer
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• TCP / IP PROTOCOL SUITE
• TCP stands for Transmission Control Protocol,
  while IP stands for Internet Protocol.
• It is a suite of protocols for communication
  structured in four layers. It can be used for
  communication over the internet as well as for
  private networks.
• The four layers are Application layer, Transport
  layer, Internet layer and Network access layer or
  Link layer, as depicted in the following diagram 

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Comparison of OSI and TCP/IP Models
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• What is the TCP/IP Model?
• Protocols Applied
• Layers of the TCP/IP Model
• Advantages of TCP/IP Model
• OSI Model VS TCP/IP Model

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Types of network protocol 1.Transmission Control
Protocol (TCP) TCP stands for Transmission
Control Protocol a communications standard that
enables application programs and computing
devices to exchange messages over a
network. 2.Internet Protocol (IP) Internet
Protocol (IP) is the method or protocol by which
data is sent from one computer to another on the
internet. 3.User Datagram Protocol (UDP) What is
UDP protocol used for?User Datagram Protocol
(UDP) refers to a protocol used for communication
throughout the internet.
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4.Post office Protocol (POP) POP3 is designed
for receiving incoming E-mails. 5.Simple mail
transport Protocol (SMTP) SMTP is designed to
send and distribute outgoing E-Mail. 6.File
Transfer Protocol (FTP) FTP allows users to
transfer files from one machine to
another. 7.Hyper Text Transfer Protocol (HTTP)
Through the HTTP protocol, resources are
exchanged between client devices and servers over
the internet. 8.Hyper Text Transfer Protocol
Secure (HTTPS) Hypertext Transfer Protocol
Secure (HTTPS) is a protocol that secures
communication and data transfer between a user's
web browser and a website.
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9. RTP (Real-Time Transport Protocol) It carries
the media streams. 10. ICMP (Internet Control
Message Protocol) is used for reporting errors
and performing network diagnostics. 11. DNS
(Domain Name System) translates human readable
domain names (for example, www.amazon.com) to
machine readable IP addresses (for example,
192.0.2.44) 12. DSL (Digital Subscriber Line)
DSL, networking technology that provides
broadband (high-speed) Internet connections over
conventional telephone lines. 13.SONET
(Synchronous Optical Network) It can transmits
and multiplexes multiple data streams across a
fiber optic cable.
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A network protocol is an established set of rules
that determine how data is transmitted between
different devices in the same network.
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Between two person understand the language in
format
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Between two system in format
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Between two computers understand the message
in format
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Protocols
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Protocols support for Networks communications
Communication
Network
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TCP/IP
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TCP/IP vs OSI
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TCP/IP Layers
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• TCP IP model layers functions
• 1. Functions of Link Layer
• The link layer is the first layer of the TCP IP
  model. The link layer is the combination of the
  Physical layer and the data link layer of the OSI
  model.
• The link layer is responsible for sending data
  bits over the communication medium or media.
• The link layer is responsible for communication
  among devices of the same network.
• The link layer uses WiFi as well as an Ethernet
  protocol to allow network devices of the same
  network to communicate with each other.

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Link Layer
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Link Layer function
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Link Layer function
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Link Layer function
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Link Layer function
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Logical Link Control
Link Layer function
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• 2. Functions of Internet Layer (IP and ICMP)
• The Internet layer is the middle layer between
  the Transport layer and link layer. The Internet
  layer is similar to network layer of OSI model.
• Internet Layer converts received segment into
  packets.
• Internet Layer Adds Source and destination IP
  address to each packet.
• Internet Layer Responsible for routing of
  packets.
• Handles network traffic i.e network conjunction.
• Internet Layer adds sequence number to each
  packet.
• Internet Layer Protocols IP, ICMP, IGMP, IPsec.

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Routing, Path Determination
Network Layer function
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Routing, Path Determination
Network Layer function
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Address Resolution Protocol (ARP) is a protocol
or procedure that connects an ever-changing
Internet Protocol (IP) address to a fixed
physical machine address, also known as a media
access control (MAC) address, in a local-area
network (LAN). MAC address will change in every
hop
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OSPF - Open Shortest Path First) protocol BGP -
Border Gateway Protocol ISIS - Intermediate
System to Intermediate System
Network layer function
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Delivery of data will take care by transport layer
Network layer function
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• 3. Functions of Transport layer
• The transport layer is the middle layer between
  the Application layer and the Internet layer. It
  receives data or information from the Application
  Layer.
• If we send entire data or information together
  and if we lose that data while sending then we
  will lose the entire data or information.
• So it is better to divide that data or
  information into small parts or units and then
  send it.
• This job of dividing data or information into
  small parts or units is done by Transport Layer.
  This process of dividing data or information into
  small parts or units is called Segmentation.
• Transport layer protocols TCP, UDP, etc.

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Delivery of data will take care by transport
layer
Transport layer function
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1
2
3
Simple Network Management Protocol (SNMP) Routing
Information Protocol (RIP) 
Transport layer function
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1
2
Transport layer function
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3
Transport layer function
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Sequence Number
Transport layer function
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Not received ACK from receiver
Transport layer function
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Same Segment number identify and remove
Transport layer function
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If ACK missed
Transport layer function
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• 4. Functions of Application layer
• The application layer is responsible for
  receiving webpage request from user or client
  using the most widely used protocol namely HTTP
  protocol and displaying response back in the
  browser.
• Application layer also responsible for sending
  data or files from one place to another place.
• Application layer is used to send Emails.
• Application is responsible for converting a
  domain name i.e website name into IP address i.e
  DNS.
• Application layer also acts as a data translator.
• Application layer is also responsible for data
  encryption or decryption, compression, and
  decompression.
• The Application layer is responsible for creating
  a session between client and server.

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Application layer function
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Internet Message Access Protocol, or IMAP IRC
(Internet Relay Chat) is a protocol for real-time
text messaging between internet-connected
computers 
Application layer function
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• The main advantages of TCP/IP are as follows -
• It is a broadly accepted model which can deploy
  effectively in all the practical networking
  issues.
• TCP / IP can also enable cross-platform
  communications among the heterogeneous networks.
• It supports connection-oriented reliable service.
  It defines that it maintains the transfer of data
  packets.
• If the data packet is missing across the web,
  thus the TCP will retransmit the lost packets.

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Heterogeneous Networks
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• It supports error disclosure by using checksum
  and error control by using Go Back or ARP
  protocol.
• Disadvantages
• The TCP/IP model is not shared and appropriated
  to represent any protocol stack other than
  TCP/IP.
• The TCP/IP model does not determine the physical
  and data link layers.
• It can improve a considerable overhead as every
  structure obtains its TCP header. Therefore,
  fragmentation through the router improves the
  overhead.

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• The Model Used in This Book with 5 Layers
• Due to the strength of the TCP/IP reference model
  is the protocols, which have been widely used for
  many years.
• This model has five layers, running from the
  physical layer up through the link layer, network
  layer and transport layers to the application
  layer.

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• A Comparison of the OSI and TCP/IP Reference
  Models
• It is important to note that we are comparing the
  reference models here, not the corresponding
  protocol stacks.
• Three concepts are central to the OSI model
• 1. Services.
• 2. Interfaces.
• 3. Protocols.
• Each layer performs some services for the layer
  above it. A layers interface tells the processes
  above it how to access it. It specifies what the
  parameters are and what results to expect.
  Finally, the peer protocols used in a layer are
  the layers own business. It can use any
  protocols it wants to, as long as it gets the job
  done

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• A Comparison of the OSI and TCP/IP Reference
  Models
• The TCP/IP model did not originally clearly
  distinguish between services, interfaces, and
  protocols, although people have tried to retrofit
  it after the fact to make it more OSI-like. For
  example, the only real services offered by the
  internet layer are SEND IP PACKET and RECEIVE IP
  PACKET.
• The OSI reference model was devised before the
  corresponding protocols were invented. This
  ordering meant that the model was not biased
  toward one particular set of protocols, a fact
  that made it quite general.

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• A Comparison of the OSI and TCP/IP Reference
  Models
• When people started to build real networks using
  the OSI model and existing protocols, it was
  discovered that these networks did not match the
  required service specifications, so convergence
  sublayers had to be grafted onto the model to
  provide a place for papering over the
  differences.
• Finally, the committee originally expected that
  each country would have one network, run by the
  government and using the OSI protocols, so no
  thought was given to internetworking.

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• A Comparison of the OSI and TCP/IP Reference
  Models
• With TCP/IP the reverse was true the protocols
  came first, and the model was really just a
  description of the existing protocols. There was
  no problem with the protocols fittin