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INTRODUCTION TO COMPUTER NETWORKS

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Title: INTRODUCTION TO COMPUTER NETWORKS


1
INTRODUCTION TOCOMPUTER NETWORKS
Computer Centre Indian Institute of Technology
Kanpur Kanpur INDIA
2
Course Content
Course Content
  • Lecture 1 Overview of the Course and Network
    Fundamentals 2 Hour
  • Lecture 2 OSI Model TCP/IP Model 2 Hour
  • Lecture 3 Physical Media (Copper, Fiber Optic
    and Wireless) 2 Hour
  • Lab 1 IIT Kanpur Datacenter Visit 2 Hour
  • Lecture 4 UTP Fiber Cabling 2 Hour
  • Lecture 5 LAN Technologies (Ethernet, Fast
    Ethernet, Gigabit Ethernet, Wireless LAN) 2
    Hour
  • Lab 2 Demo and Practice of UTP Fiber Cabling
    2 Hour
  • Lecture 6 LAN Technologies (contd.) 2 Hour

3
Course Content
Course Content
  • Lecture 7 WAN Technologies (Dialup, Leased Line,
    ISDN, ADSL, Cable Modem, VSAT) 2 Hour
  • Lab 3 Demo and Practice of Ethernet Wireless
    LAN Setup 2 Hour
  • Lecture 8 WAN Technologies (contd.) 2 Hour
  • Lecture 9 Internet Protocol (IP) and IP
    Addressing 2 Hour
  • Lab 4 Demo and Practice of Setting up Subnets
    and IP Address Assignment 2 Hour
  • Lecture 10 Routing, VLAN, TCP and UDP 2 Hour
  • Lecture 11 SNMP, Natting, Firewall and VPN 2
    Hour
  • Lecture 12 Internet and Internet Applications
    (DNS, Email, Web..) 2 Hour

4
Course Content
Course Content
  • Lecture 13 Cisco Basics 2 Hour
  • Lecture 14 Cisco Switch and Router Configuration
    2 Hour
  • Lab 5 Demo and Practice of Cisco Switch
    Configuration 2 Hour
  • Lab 6 Demo and Practice of Cisco Router
    Configuration 2 Hour
  • Lecture 15 DNS Web Server Setup on Linux 2
    Hour
  • Lab 7 Demo and Practice of DNS and Web Server
    Setup 2 Hour
  • Lecture 16 Enterprise Network Implementation 2
    Hour

5
Course Content
Course Content
  • Lecture 17 Mail Server, Proxy Server Firewall
    Setup on Linux 2 Hour
  • Lab 8 Demo and Practice of Mail Server , Proxy
    Server and Firewall Setup 2 Hour

6
References
Books
  • Andrew S. Tanenbaum, Computer Network,
    Prentice-Hall
  • Doughlas E. Comer, Computer Networks and Internet
  • http//www.cisco.com/public/support/tac/documentat
    ion.html
  • http//www.redhat.com/docs
  • http//home.iitk.ac.in/navi/sidbinetworkcourse

7
Grading Guidelines
Grading
  • Two Exams 40 each
  • Lab Assignments 20
  • Minimum 80 attendance and minimum 60 marks are
    necessary to clear the course.

8
Introduction to Computer Networks
  • INTRODUCTION TO COMPUTER NETWORKS

9
Computer Networks
Introduction to Computer Networks
  • Computer network connects two or more autonomous
    computers.
  • The computers can be geographically located
    anywhere.

10
LAN, MAN WAN
Introduction to Computer Networks
  • Network in small geographical Area (Room,
    Building or a Campus) is called LAN (Local Area
    Network)
  • Network in a City is call MAN (Metropolitan Area
    Network)
  • Network spread geographically (Country or across
    Globe) is called WAN (Wide Area Network)

11
Applications of Networks
Introduction to Computer Networks
  • Resource Sharing
  • Hardware (computing resources, disks, printers)
  • Software (application software)
  • Information Sharing
  • Easy accessibility from anywhere (files,
    databases)
  • Search Capability (WWW)
  • Communication
  • Email
  • Message broadcast
  • Remote computing
  • Distributed processing (GRID Computing)

12
Network Topology
Introduction to Computer Networks
  • The network topology defines the way in which
    computers, printers, and other devices are
    connected. A network topology describes the
    layout of the wire and devices as well as the
    paths used by data transmissions.

13
Bus Topology
Introduction to Computer Networks
  • Commonly referred to as a linear bus, all the
    devices on a bus topology are connected by one
    single cable.

14
Star Tree Topology
Introduction to Computer Networks
  • The star topology is the most commonly used
    architecture in Ethernet LANs.
  • When installed, the star topology resembles
    spokes in a bicycle wheel.
  • Larger networks use the extended star topology
    also called tree topology. When used with network
    devices that filter frames or packets, like
    bridges, switches, and routers, this topology
    significantly reduces the traffic on the wires by
    sending packets only to the wires of the
    destination host.

15
Ring Topology
Introduction to Computer Networks
  • A frame travels around the ring, stopping at each
    node. If a node wants to transmit data, it adds
    the data as well as the destination address to
    the frame.
  • The frame then continues around the ring until it
    finds the destination node, which takes the data
    out of the frame.
  • Single ring All the devices on the network
    share a single cable
  • Dual ring The dual ring topology allows data to
    be sent in both directions.

16
Mesh Topology
Introduction to Computer Networks
  • The mesh topology connects all devices (nodes) to
    each other for redundancy and fault tolerance.
  • It is used in WANs to interconnect LANs and for
    mission critical networks like those used by
    banks and financial institutions.
  • Implementing the mesh topology is expensive and
    difficult.

17
Network Components
Introduction to Computer Networks
  • Physical Media
  • Interconnecting Devices
  • Computers
  • Networking Software
  • Applications

18
Networking Media
Introduction to Computer Networks
  • Networking media can be defined simply as the
    means by which signals (data) are sent from one
    computer to another (either by cable or wireless
    means).

19
Networking Devices
Introduction to Computer Networks
  • HUB, Switches, Routers, Wireless Access Points,
    Modems etc.

20
Computers Clients and Servers
Introduction to Computer Networks
  • In a client/server network arrangement, network
    services are located in a dedicated computer
    whose only function is to respond to the requests
    of clients.
  • The server contains the file, print, application,
    security, and other services in a central
    computer that is continuously available to
    respond to client requests.

21
Networking Protocol TCP/IP
Introduction to Computer Networks
22
Applications
Introduction to Computer Networks
  • E-mail
  • Searchable Data (Web Sites)
  • E-Commerce
  • News Groups
  • Internet Telephony (VoIP)
  • Video Conferencing
  • Chat Groups
  • Instant Messengers
  • Internet Radio

23
OSI Model
  • OSI MODEL

24
Communication Architecture
OSI Model
  • Strategy for connecting host computers and other
    communicating equipment.
  • Defines necessary elements for data communication
    between devices.
  • A communication architecture, therefore, defines
    a standard for the communicating hosts.
  • A programmer formats data in a manner defined by
    the communication architecture and passes it on
    to the communication software.
  • Separating communication functions adds
    flexibility, for example, we do not need to
    modify the entire host software to include more
    communication devices.

25
Layer Architecture
OSI Model
  • Layer architecture simplifies the network design.
  • It is easy to debug network applications in a
    layered architecture network.
  • The network management is easier due to the
    layered architecture.
  • Network layers follow a set of rules, called
    protocol.
  • The protocol defines the format of the data being
    exchanged, and the control and timing for the
    handshake between layers.

26
Open Systems Interconnection (OSI) Model
OSI Model
  • International standard organization (ISO)
    established a committee in 1977 to develop an
    architecture for computer communication.
  • Open Systems Interconnection (OSI) reference
    model is the result of this effort.
  • In 1984, the Open Systems Interconnection (OSI)
    reference model was approved as an international
    standard for communications architecture.
  • Term open denotes the ability to connect any
    two systems which conform to the reference model
    and associated standards.

27
OSI Reference Model
OSI Model
  • The OSI model is now considered the primary
    Architectural model for inter-computer
    communications.
  • The OSI model describes how information or data
    makes its way from application programmes (such
    as spreadsheets) through a network medium (such
    as wire) to another application programme located
    on another network.
  • The OSI reference model divides the problem of
    moving information between computers over a
    network medium into SEVEN smaller and more
    manageable problems .
  • This separation into smaller more manageable
    functions is known as layering.

28
OSI Reference Model 7 Layers
OSI Model
29
OSI A Layered Network Model
OSI Model
  • The process of breaking up the functions or tasks
    of networking into layers reduces complexity.
  • Each layer provides a service to the layer above
    it in the protocol specification.
  • Each layer communicates with the same layers
    software or hardware on other computers.
  • The lower 4 layers (transport, network, data link
    and physical Layers 4, 3, 2, and 1) are
    concerned with the flow of data from end to end
    through the network.
  • The upper four layers of the OSI model
    (application, presentation and sessionLayers 7,
    6 and 5) are orientated more toward services to
    the applications.
  • Data is Encapsulated with the necessary protocol
    information as it moves down the layers before
    network transit.

30
Physical Layer
OSI Model
  • Provides physical interface for transmission of
    information.
  • Defines rules by which bits are passed from one
    system to another on a physical communication
    medium.
  • Covers all - mechanical, electrical, functional
    and procedural - aspects for physical
    communication.
  • Such characteristics as voltage levels, timing of
    voltage changes, physical data rates, maximum
    transmission distances, physical connectors, and
    other similar attributes are defined by physical
    layer specifications.

31
Data Link Layer
OSI Model
  • Data link layer attempts to provide reliable
    communication over the physical layer interface.
  • Breaks the outgoing data into frames and
    reassemble the received frames.
  • Create and detect frame boundaries.
  • Handle errors by implementing an acknowledgement
    and retransmission scheme.
  • Implement flow control.
  • Supports points-to-point as well as broadcast
    communication.
  • Supports simplex, half-duplex or full-duplex
    communication.

32
Network Layer
OSI Model
  • Implements routing of frames (packets) through
    the network.
  • Defines the most optimum path the packet should
    take from the source to the destination
  • Defines logical addressing so that any endpoint
    can be identified.
  • Handles congestion in the network.
  • Facilitates interconnection between heterogeneous
    networks (Internetworking).
  • The network layer also defines how to fragment a
    packet into smaller packets to accommodate
    different media.

33
Transport Layer
OSI Model
  • Purpose of this layer is to provide a reliable
    mechanism for the exchange of data between two
    processes in different computers.
  • Ensures that the data units are delivered error
    free.
  • Ensures that data units are delivered in
    sequence.
  • Ensures that there is no loss or duplication of
    data units.
  • Provides connectionless or connection oriented
    service.
  • Provides for the connection management.
  • Multiplex multiple connection over a single
    channel.

34
Session Layer
OSI Model
  • Session layer provides mechanism for controlling
    the dialogue between the two end systems. It
    defines how to start, control and end
    conversations (called sessions) between
    applications.
  • This layer requests for a logical connection to
    be established on an end-users request.
  • Any necessary log-on or password validation is
    also handled by this layer.
  • Session layer is also responsible for terminating
    the connection.
  • This layer provides services like dialogue
    discipline which can be full duplex or half
    duplex.
  • Session layer can also provide check-pointing
    mechanism such that if a failure of some sort
    occurs between checkpoints, all data can be
    retransmitted from the last checkpoint.

35
Presentation Layer
OSI Model
  • Presentation layer defines the format in which
    the data is to be exchanged between the two
    communicating entities.
  • Also handles data compression and data encryption
    (cryptography).

36
Application Layer
OSI Model
  • Application layer interacts with application
    programs and is the highest level of OSI model.
  • Application layer contains management functions
    to support distributed applications.
  • Examples of application layer are applications
    such as file transfer, electronic mail, remote
    login etc.

37
OSI in Action
OSI Model
  • A message begins at the top application layer and
    moves down the OSI layers to the bottom physical
    layer.
  • As the message descends, each successive OSI
    model layer adds a header to it.
  • A header is layer-specific information that
    basically explains what functions the layer
    carried out.
  • Conversely, at the receiving end, headers are
    striped from the message as it travels up the
    corresponding layers.

38
TCP/IP Model
  • TCP/IP MODEL

39
OSI TCP/IP Models
TCP/IP Model
40
TCP/IP Model
TCP/IP Model
Application Layer Application programs using the
network
Transport Layer (TCP/UDP) Management of
end-to-end message transmission, error detection
and error correction
Network Layer (IP) Handling of datagrams
routing and congestion
Data Link Layer Management of cost effective and
reliable data delivery, access to physical
networks
Physical Layer Physical Media
41
Physical Media
  • PHYSICAL MEDIA

42
Physical Media
Physical Media
43
Physical Media
Physical Media
  • Copper
  • Coaxial Cable - Thick or Thin
  • Unshielded Twisted Pair - CAT 3,4,5,5e6
  • Optical Fiber
  • Multimode
  • Singlemode
  • Wireless
  • Short Range
  • Medium Range (Line of Sight)
  • Satellite

44
Copper Media Coaxial Cable
Physical Media
  • Coaxial cable is a copper-cored cable surrounded
    by a heavy shielding and is used to connect
    computers in a network.
  • Outer conductor shields the inner conductor from
    picking up stray signal from the air.
  • High bandwidth but lossy channel.
  • Repeater is used to regenerate the weakened
    signals.

Category Impedance Use
RG-59 75 W Cable TV
RG-58 50 W Thin Ethernet
RG-11 50 W Thick Ethernet
45
Copper Media Twisted Pair
Physical Media
  • 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).

46
Shielded Twisted Pair (STP)
Physical Media
47
Unshielded Twisted Pair (UTP)
Physical Media
48
Unshielded Twisted Pair (UTP)
Physical Media
  • 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.

49
Categories of UTP
Physical Media
  • 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.

50
Categories of UTP CAT 3
Physical Media
  • Bandwidth 16 Mhz
  • 11.5 dB Attenuation
  • 100 ohms Impedance
  • Used in voice applications and 10baseT (10Mbps)
    Ethernet

51
Categories of UTP CAT 4
Physical Media
  • 20 MHz Bandwidth
  • 7.5 dB Attenuation
  • 100 ohms Impedance
  • Used in 10baseT (10Mbps) Ethernet

52
Categories of UTP CAT 5
Physical Media
  • 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)

53
Categories of UTP CAT 5e
Physical Media
  • 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

54
Categories of UTP CAT 6
Physical Media
  • 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)

55
Fiber Media
Physical Media
  • Optical fibers use light to send information
    through the optical medium.
  • It uses the principal of total internal
    reflection.
  • Modulated light transmissions are used to
    transmit the signal.

56
Total Internal Reflection
Physical Media
57
Fiber Media
Physical Media
  • Light travels through the optical media by the
    way of total internal reflection.
  • Modulation scheme used is intensity modulation.
  • Two types of Fiber media
  • Multimode
  • Singlemode
  • Multimode Fiber can support less bandwidth than
    Singlemode Fiber.
  • Singlemode Fiber has a very small core and carry
    only one beam of light. It can support Gbps data
    rates over gt 100 Km without using repeaters.

58
Single and Multimode Fiber
Physical Media
  • Single-mode fiber
  • Carries light pulses along single path
  • Uses Laser Light Source
  • Multimode fiber
  • Many pulses of light generated by LED travel at
    different angles

59
Fiber Media
Physical Media
  • The bandwidth of the fiber is limited due to the
    dispersion effect.
  • Distance Bandwidth product of a fiber is almost a
    constant.
  • Fiber optic cables consist of multiple fibers
    packed inside protective covering.
  • 62.5/125 µm (850/1310 nm) multimode fiber
  • 50/125 µm (850/1310 nm) multimode fiber
  • 10 µm (1310 nm) single-mode fiber

60
Fiber-Optic Cable
Physical Media
  • Contains one or several glass fibers at its core
  • Surrounding the fibers is a layer called cladding

61
Fiber Optic Cable
Physical Media
  • FO Cable may have 1 to over 1000 fibers

62
Wireless Media
Physical Media
  • Very useful in difficult terrain where cable
    laying is not possible.
  • Provides mobility to communication nodes.
  • Right of way and cable laying costs can be
    reduced.
  • Susceptible to rain, atmospheric variations and
    Objects in transmission path.

63
Wireless Media
Physical Media
  • Indoor 10 50m BlueTooth, WLAN
  • Short range Outdoor 50 200m WLAN
  • Mid Range Outdoor 200m 5 Km GSM, CDMA, WLAN
    Point-to-Point, Wi-Max
  • Long Range Outdoor 5 Km 100 Km Microwave
    Point-to-Point
  • Long Distance Communication Across Continents
    Satellite Communication

64
Frequency Bands
Physical Media
Band Range Propagation Application
VLF 330 KHz Ground Long-range radio navigation
LF 30300 KHz Ground Radio beacons andnavigational locators
MF 300 KHz3 MHz Sky AM radio
HF 330 MHz Sky Citizens band (CB),ship/aircraft communication
VHF 30300 MHz Sky andline-of-sight VHF TV, FM radio
UHF 300 MHz3 GHz Line-of-sight UHF TV, cellular phones, paging, satellite
SHF 330 GHz Line-of-sight Satellite communication
EHF 30300 GHz Line-of-sight Long-range radio navigation
65
Wireless LAN
Physical Media
PC
Access Point

Internet
Router
Switch
PC
Access Point
66
Terrestrial Microwave
Physical Media
  • Microwaves do not follow the curvature of earth
  • Line-of-Sight transmission
  • Height allows the signal to travel farther
  • Two frequencies for two way communication
  • Repeater is used to increase the distance
    Hop-by-Hop

67
Satellite Communication
Physical Media
68
Cabling
  • UTP AND FIBER CABLING

69
Structured Cabling Infrastructure
Cabling
  • Mounted and permanent
  • Allows patching
  • Comfort that infrastructure is OK
  • Components
  • Information Outlet with Face Plate
  • Patch Panel
  • UTP Cable
  • Patch Cord

70
I/O Faceplates
Cabling
  • Faceplate mounts on or in wall or in raceway
  • Single or Dual Information Outlet (I/O)
  • Provide network connectivity to the Hosts through
    a Patch Cord

71
Patch Panel
Cabling
  • Termination punchdown in back
  • Patch cord plugin in front

72
Patch Cord UTP Connectors
Cabling
73
Color Codes
Cabling
  • Data Tx 1 2
  • Data Rx 3 6
  • Crossover
  • 1 ? 3
  • 2 ? 6
  • PoE VDC 4 5
  • PoE -VDC 7 8

74
Cutting, Striping Crimping Tools
Cabling
  • Make your own patch cords
  • Cuts and strips pairs
  • RJ45 end crimped onto ends of wire

75
Punching Tool
Cabling
  • Terminates wires to back of patch panels and in
    Information Outlets

76
Making Cables
Cabling
77
Wire Testing Equipment
Cabling
  • Test wire for correct termination of 8 wires
  • Test for speed capabilities

78
Cabling Rules
Cabling
  • Try to avoid running cables parallel to power
    cables.
  • Do not bend cables to less than four times the
    diameter of the cable.
  • If you bundle a group of cables together with
    cable ties (zip ties), do not over-cinch
    them. You should be able to turn the tie with
    fingers.
  • Keep cables away from devices which can introduce
    noise into them. Here's a short list copy
    machines, electric heaters, speakers, printers,
    TV sets, fluorescent lights, copiers, welding
    machines, microwave ovens, telephones, fans,
    elevators, motors, electric ovens, dryers,
    washing machines, and shop equipment.
  • Avoid stretching UTP cables (tension when pulling
    cables should not exceed 25 LBS).
  • Do not run UTP cable outside of a building.  It
    presents a very dangerous lightning hazard!
  • Do not use a stapler to secure UTP cables.  Use
    telephone wire/RJ6 coaxial wire hangers which are
    available at most hardware stores.

79
Fiber Optic Cabling Infrastructure
Cabling
  • Components
  • Fiber Cable
  • Fiber Pigtail
  • Fiber Connectors
  • LIU
  • Coupler
  • Fiber Patch Cord

80
Fiber Optic Connectors
Cabling
  • Terminates the fibers
  • Connects to other fibers or transmission
    equipment

81
Fiber Patch Cords Pigtails
Cabling
  • Ends are typically either SC or ST
  • Pigtails have connectors on only one side and
    Patch Cords have it on both sides.
  • Pigtails are spliced to the fiber to terminate
    the fiber
  • Patch Cord connects switches to the Fiber cable

82
LIU Couplers
Cabling
83
Fiber Optic Installation Outside Plant
Cabling
84
Fiber Optic Installation Outside Plant
Cabling
  • Fiber is blown in HDPE Pipes, 1 m deep.
  • The HDPE pipes is covered with sand and brick
    lining
  • Fiber Roles are typically 2 Km. Fiber cables are
    spliced using Jointers
  • Faults like fiber cut are located using OTDR
    (Optical Time Domain Reflectometer)

85
LAN Technologies
  • LAN TECHNOLOGIES

86
Technology Options
LAN Technologies
  • Ethernet
  • Fast Ethernet
  • Gigabit Ethernet
  • 10 Gig Ethernet
  • WLAN

87
Media Access
LAN Technologies
  • Ethernet and Wi-Fi are both multi-access
    technologies
  • Broadcast medium, shared by many hosts
  • Simultaneous transmissions will result in
    collisions
  • Media Access Control (MAC) protocol required
  • Rules on how to share medium
  • The Data Link Layer is divided into two Part MAC
    Media Access Control) Sublayer and LLC (Logic
    Link Control) Sublayer

88
802.3 Ethernet
LAN Technologies
  • Carrier-sense multiple access with collision
    detection (CSMA/CD).
  • CS carrier sense
  • MA multiple access
  • CD collision detection
  • Base Ethernet standard is 10 Mbps.
  • 100Mbps, 1Gbps, 10Gbps standards came later

89
Ethernet CSMA/CD
LAN Technologies
  • CSMA/CD (carrier sense multiple access with
    collision detection) media access protocol is
    used.
  • Data is transmitted in the form of packets.
  • Sense channel prior to actual packet
    transmission.
  • Transmit packet only if channel is sensed idle
    else, defer the transmission until channel
    becomes idle.
  • After packet transmission is started, the node
    monitors its own transmission to see if the
    packet has experienced a collision.
  • If the packet is observed to be undergoing a
    collision, the transmission is aborted and the
    packet is retransmitted after a random interval
    of time using Binary Exponential Backoff
    algorithm.

90
Ethernet Address
LAN Technologies
  • End nodes are identified by their Ethernet
    Addresses (MAC Address or Hardware Address) which
    is a unique 6 Byte address.
  • MAC Address is represented in Hexa Decimal format
    e.g 00055DFE100A
  • The first 3 bytes identify a vendor (also called
    prefix) and the last 3 bytes are unique for every
    host or device

91
Ethernet Frame Structure
LAN Technologies
  • Preamble
  • 7 bytes with pattern 10101010 followed by one
    byte with pattern 10101011
  • Used to synchronize receiver, sender clock rates
  • Addresses 6 bytes, frame is received by all
    adapters on a LAN and dropped if address does not
    match
  • Length 2 bytes, length of Data field
  • CRC 4 bytes generated using CR-32, checked at
    receiver, if error is detected, the frame is
    simply dropped
  • Data Payload Maximum 1500 bytes, minimum 46
    bytes
  • If data is less than 46 bytes, pad with zeros to
    46 bytes

Length
92
Ethernet
LAN Technologies
  • 10 Base 5 (Thicknet) (Bus Topology)
  • 10 Base 2 (Thinnet) (Bus Topology)
  • 10 Base T (UTP) (Star/Tree Topology)
  • 10 Base FL (Fiber) (Star/Tree Topology)

93
Ethernet BUS Topology
LAN Technologies
Repeater
94
Ethernet STAR Topology
LAN Technologies
Hub
95
Ethernet
LAN Technologies
  • Physical Media -
  • 10 Base5 - Thick Co-axial Cable with Bus
    Topology
  • 10 Base2 - Thin Co-axial Cable with Bus
    Topology
  • 10 BaseT - UTP Cat 3/5 with Tree Topology
  • 10 BaseFL - Multimode/Singlemode Fiber with
    Tree
  • Topology
  • Maximum Segment Length
  • 10 Base5 - 500 m with at most 4 repeaters
    (Use Bridge to extend
    the network)
  • 10 Base2 - 185 m with at most 4 repeaters
    (Use Bridge to extend
    the network)
  • 10 BaseT - 100 m with at most 4 hubs (Use
    Switch to extend the
    network)

96
Fast Ethernet
LAN Technologies
  • 100 Mbps bandwidth
  • Uses same CSMA/CD media access protocol and
    packet format as in Ethernet.
  • 100BaseTX (UTP) and 100BaseFX (Fiber) standards
  • Physical media -
  • 100 BaseTX - UTP Cat 5e
  • 100 BaseFX - Multimode / Singlemode Fiber
  • Full Duplex/Half Duplex operations.

97
Fast Ethernet
LAN Technologies
  • Provision for Auto-Negotiation of media speed
    10 Mbps or 100Mbps (popularly available for
    copper media only).
  • Maximum Segment Length
  • 100 Base TX - 100 m
  • 100 Base FX - 2 Km (Multimode Fiber)
  • 100 Base FX - 20 km (Singlemode Fiber)

98
Gigabit Ethernet
LAN Technologies
  • 1 Gbps bandwidth.
  • Uses same CSMA/CD media access protocol as in
    Ethernet and is backward compatible (10/100/100
    modules are available).
  • 1000BaseT (UTP), 1000BaseSX (Multimode Fiber) and
    1000BaseLX (Multimode/Singlemode Fiber)
    standards.
  • Maximum Segment Length
  • 1000 Base T - 100m (Cat 5e/6)
  • 1000 Base SX - 275 m (Multimode Fiber)
  • 1000 Base LX - 512 m (Multimode Fiber)
  • 1000 Base LX - 20 Km (Singlemode Fiber)
  • 1000 Base LH - 80 Km (Singlemode Fiber)

99
10 Gig Ethernet
LAN Technologies
  • 10 Gbps bandwidth.
  • Uses same CSMA/CD media access protocol as in
    Ethernet.
  • Propositioned for Metro-Ethernet
  • Maximum Segment Length
  • 1000 Base-T - Not available
  • 10GBase-LR - 10 Km (Singlemode Fiber)
  • 10GBase-ER - 40 Km (Singlemode Fiber)

100
802.11 Wireless LAN
LAN Technologies
  • Provides network connectivity over wireless media
  • An Access Point (AP) is installed to act as
    Bridge between Wireless and Wired Network
  • The AP is connected to wired network and is
    equipped with antennae to provide wireless
    connectivity

Desktop with PCI 802.11 LAN card
Network connectivity to the legacy wired LAN
Laptop with PCMCIA 802.11 LAN card
Access Point
101
802.11 Wireless LAN
LAN Technologies
  • Range ( Distance between Access Point and WLAN
    client) depends on structural hindrances and RF
    gain of the antenna at the Access Point
  • To service larger areas, multiple APs may be
    installed with a 20-30 overlap
  • A client is always associated with one AP and
    when the client moves closer to another AP, it
    associates with the new AP (Hand-Off)
  • Three flavors
  • 802.11b
  • 802.11a
  • 802.11g

102
Multiple Access with Collision Avoidance (MACA)
LAN Technologies
  • Before every data transmission
  • Sender sends a Request to Send (RTS) frame
    containing the length of the transmission
  • Receiver respond with a Clear to Send (CTS) frame
  • Sender sends data
  • Receiver sends an ACK now another sender can
    send data
  • When sender doesnt get a CTS back, it assumes
    collision

other node in senders range
other node in receivers range
sender
receiver
RTS
CTS
data
ACK
103
WLAN 802.11b
LAN Technologies
  • The most popular 802.11 standard currently in
    deployment.
  • Supports 1, 2, 5.5 and 11 Mbps data rates in the
    2.4 GHz ISM (Industrial-Scientific-Medical) band

104
WLAN 802.11a
LAN Technologies
  • Operates in the 5 GHz UNII (Unlicensed National
    Information Infrastructure) band
  • Incompatible with devices operating in 2.4GHz
  • Supports Data rates up to 54 Mbps.

105
WLAN 802.11g
LAN Technologies
  • Supports data rates as high as 54 Mbps on the 2.4
    GHz band
  • Provides backward compatibility with 802.11b
    equipment

106
Repeater, HUB, Bridge Switch
  • REPEATER, HUB, BRIDGE AND SWITCH

107
Repeater
Repeater, Hub, Bridge Switch
  • A repeater receives a signal, regenerates it, and
    passes it on.
  • It can regenerate and retime network signals at
    the bit level to allow them to travel a longer
    distance on the media.
  • It operates at Physical Layer of OSI
  • The Four Repeater Rule for 10-Mbps Ethernet
    should be used as a standard when extending LAN
    segments.
  • This rule states that no more than four repeaters
    can be used between hosts on a LAN.
  • This rule is used to limit latency added to frame
    travel by each repeater.

108
Hub
Repeater, Hub, Bridge Switch
  • Hubs are used to connect multiple nodes to a
    single physical device, which connects to the
    network.
  • Hubs are actually multiport repeaters.
  • Using a hub changes the network topology from a
    linear bus, to a star.
  • With hubs, data arriving over the cables to a hub
    port is electrically repeated on all the other
    ports connected to the same network segment,
    except for the port on which the data was sent.

109
Bridge
Repeater, Hub, Bridge Switch
  • Bridges are used to logically separate network
    segments within the same network.
  • They operate at the OSI data link layer (Layer 2)
    and are independent of higher-layer protocols.
  • The function of the bridge is to make intelligent
    decisions about whether or not to pass signals on
    to the next segment of a network.
  • When a bridge receives a frame on the network,
    the destination MAC address is looked up in the
    bridge table to determine whether to filter,
    flood, or copy the frame onto another segment
  • Broadcast Packets are forwarded

110
Switch
Repeater, Hub, Bridge Switch
  • Switches are Multiport Bridges.
  • Switches provide a unique network segment on each
    port, thereby separating collision domains.
  • Today, network designers are replacing hubs in
    their wiring closets with switches to increase
    their network performance and bandwidth while
    protecting their existing wiring investments.
  • Like bridges, switches learn certain information
    about the data packets that are received from
    various computers on the network.
  • Switches use this information to build forwarding
    tables to determine the destination of data being
    sent by one computer to another computer on the
    network.

111
Switches Dedicated Access
Repeater, Hub, Bridge Switch
A
  • Hosts have direct connection to switch
  • Full Duplex No collisions
  • Switching A-to-A and B-to-B simultaneously, no
    collisions
  • Switches can be cascaded to expand the network

C
B
switch
C
B
A
112
WAN Technologies
  • WAN TECHNOLOGIES

113
Technology Options
WAN Technologies
  • Dial-up
  • Leased Line
  • ISDN
  • X.25
  • Frame Relay
  • ATM
  • DSL
  • Cable Modem
  • Microwave Point-to-Point Link
  • VSAT

114
Dial-up
WAN Technologies
  • Uses POTS (Plain Old Telephone System)
  • Provides a low cost need based access.
  • Bandwidth 33.6 /56 Kbps.
  • On the Customer End Modem is connected to a
    Telephone Line
  • On the Service Provider End Remote Access Server
    (RAS) is connected to Telephone Lines (33.6 Kbps
    connectivity) or E1/R2 Line (56 Kbps
    connectivity)
  • RAS provide dialin connectivity, authentication
    and metering.
  • Achievable bandwidth depends on the line quality.

115
Dial-up
WAN Technologies
116
Dial-up
WAN Technologies
RAS
117
Dial-up
WAN Technologies
33.6 Kbps
Analog line
Telephone switch
Telephone switch
?
Modem
Modem
56 Kbps
Access server
Modem
E1
118
Leased Line
WAN Technologies
  • Used to provide point-to-point dedicated network
    connectivity.
  • Analog leased line can provide maximum bandwidth
    of 9.6 Kbps.
  • Digital leased lines can provide bandwidths 64
    Kbps, 2 Mbps (E1), 8 Mbps (E2), 34 Mbps (E3) ...

119
Leased Line Internet Connectivity
WAN Technologies
ISP Broadband Internet Connectivity
ISP Router
PSTN
Interface Converter
LL Modem G.703
LL Modem V.35
Router
ISP PREMISES
CUSTOMER PREMISES
120
ISDN
WAN Technologies
  • Another alternative to using analog telephones
    lines to establish a connection is ISDN.
  • Speed is one advantage ISDN has over telephone
    line connections.
  • ISDN network is a switched digital network
    consisting of ISDN Switches.
  • Each node in the network is identified by
    hierarchical ISDN address which is of 15 digits.
  • ISDN user accesses network through a set of
    standard interfaces provided by ISDN User
    Interfaces.

121
ISDN
WAN Technologies
  • Two types of user access are defined
  • Basic Access - Consists of two 64Kbps user
    channels (B channel) and one 16Kbps signally
    channel (D channel) providing service at 144
    Kbps.
  • Primary access - Consists of thirty 64Kbps user
    channels (B channels) and a 64 Kbps signally
    channel (D channel) providing service at
    2.048Mbps (One 64 Kbps channel is used for
    Framing and Synchronization).

B B D
Information 128 Kbps (Voice Data) Signaling
16Kbps
Basic
B B D
Information 1920 Kbps Voice Data Signaling 64
Kbps
Primary
122
ISDN
WAN Technologies
ISDN devices
TE1
2W
4W
NT1
S/T interface
U interface
TE2
TA
Devices NT1 - Interface Converter TE1 - ISDN
devices TE2 Non ISDN Devices (need TA) TA -
Terminal Adapter (ISDN Modem)
123
X.25
WAN Technologies
  • Packet switched Network consisting of X.25
    switches.
  • X.25 is a connection oriented protocol (Virtual
    Circuits).
  • End nodes are identified by an X .25 address.
  • Typical bandwidth offered is 2.4/9.6 kbps.
  • IP networks interface with X .25 through IP- X.25
    routers.

124
X.25 and Virtual Circuits
WAN Technologies
125
Frame Relay
WAN Technologies
  • Designed to be more efficient than X.25
  • Developed before ATM
  • Call control carried in separate logical
    connection
  • No hop by hop error or flow control
  • End to end flow and error control (if used) are
    done by higher layer
  • Single user data frame sent from source to
    destination and ACK (from higher layer) sent back
  • Two type of Virtual Circuits defined
  • Permanent virtual circuits (PVCs)
  • Switched virtual circuits (SVCs)

126
ATM
WAN Technologies
  • Small fixed size packets of 53 bytes, called
    cells, are used for transferring information.
  • Each cell has 5 bytes of header and 48 bytes of
    payload for user information.
  • Connection oriented protocol.
  • A virtual Circuit is established between the
    communicating nodes before data transfer takes
    place.
  • Can be seamlessly used in LANs and WANs.
  • Almost unlimited scalability.
  • Provides quality of service guaranties.

127
Digital Subscriber Line (DSL)
WAN Technologies
  • Digital Subscriber Line (DSL) uses the Ordinary
    Telephone line and is an always-on technology.
    This means there is no need to dial up each time
    to connect to the Internet.
  • Because DSL is highly dependent upon noise
    levels, a subscriber cannot be any more than 5.5
    kilometers (2-3 miles) from the DSL Exchange
  • Service can be symmetric, in which downstream and
    upstream speeds are identical, or asymmetric in
    which downstream speed is faster than upstream
    speed.
  • DSL comes in several varieties
  • Asymmetric DSL (ADSL)
  • High Data Rate DSL (HDSL)
  • Symmetric DSL (SDSL)
  • Very High Data Rate DSL (VDSL)

128
ADSL
WAN Technologies
129
Cable Modems
WAN Technologies
  • The cable modem connects a computer to the cable
    company network through the same coaxial cabling
    that feeds cable TV (CATV) signals to a
    television set.
  • Uses Cable Modem at Home End and CMTS (Cable
    Modem Termination System) at Head End.
  • Characteristics
  • Shared bandwidth technology
  • 10 Mbps to 30 Mbps downstream
  • 128Kbps-3 Mbps upstream
  • Maximum Distance from provider to customer site
    30 miles

130
Cable Modems
WAN Technologies
131
Point-to-Point Microwave Link
WAN Technologies
MICROWAVE LINK
Network
RFModem
Router
RFModem
Router
ISP Network
CUSTOMER PREMISES
ISP PREMISES
132
Point-to-Point Microwave Link
WAN Technologies
  • Typically 80-100 MHz Band or 5 GHz Radio Link
    band
  • 2.4 GHz WiFi links are becoming popular
  • Requires Line of Sight

133
VSAT
WAN Technologies
  • Very Small Aperture Terminal (VSAT) provide
    communication between two nodes through a
    powerful Earth station called a Hub.
  • If two terminals want to communicate, they send
    their messages to the satellite, which sends it
    to the Hub and the Hub then broadcasts the
    message through the satellite.
  • Typical Bandwidth offered is 9.6/19.2/32/64/128/25
    6/512 Kbps.
  • Operating modes are TDM/TDMA, SCPC PAMA DAMA

134
VSAT
WAN Technologies
  • Each satellite sends and receives over two bands
  • Uplink From the earth to the satellite
  • Downlink From the satellite to the earth
  • Satellite frequency bands
  • Band Downlink Uplink
  • C 3.7-4.2 GHz 5.925-6.425 GHz
  • Ku 11.7-12.2 GHz 14-14.5 GHz
  • Ku-band based networks, are used primarily in
    Europe and North America and utilize the smaller
    sizes of VSAT antennas.
  • C-band, used extensively in Asia, Africa and
    Latin America, require larger antenna.

135
Internet Protocol
  • INTERNET PROTOCOL

136
IP as a Routed Protocol
Internet Protocol
  • IP is a connectionless, unreliable, best-effort
    delivery protocol.
  • IP accepts whatever data is passed down to it
    from the upper layers and forwards the data in
    the form of IP Packets.
  • All the nodes are identified using an IP address.
  • Packets are delivered from the source to the
    destination using IP address

137
Packet Propagation
Internet Protocol
138
IP Address
Internet Protocol
  • IP address is for the INTERFACE of a host.
    Multiple interfaces mean multiple IP addresses,
    i.e., routers.
  • 32 bit IP address in dotted-decimal notation for
    ease of reading, i.e., 193.140.195.66
  • Address 0.0.0.0, 127.0.0.1 and 255.255.255.255
    carries special meaning.
  • IP address is divided into a network number and a
    host number.
  • Also bits in Network or Host Address cannot be
    all 0 or 1.

139
IP Address
Internet Protocol
140
IP Address
Internet Protocol
141
IP Address
Internet Protocol
  • Class A Address begins with bit 0. It has 8 bit
    network number (range 0.0.0.0-to-127.255.255.255),
    24 bit host number.
  • Class B Address begins with bits 10. It has 16
    bit network number (range 128.0.0.0-to-191.255.255
    .255), 16 bit host number.
  • Class C Address begins with bits 110. It has 24
    bit network number (range 192.0.0.0-to-223.255.255
    .255), 8 bit host number.
  • Class D Begins with 1110, multicast addresses
    (224.0.0.0-to-239.255.255.255)
  • Class E Begins with 11110, unused

142
Subnet Mask
Internet Protocol
  • Consider IP address 192.168.2.25
  • First few bits (left to right) identify
    network/subnet
  • Remaining bits identify host/interface
  • Number of subnet bits is called subnet mask, e.g.
  • Subnet IP Address range is 192.168.2.0
    192.168.2.255 or Mask 255.255.255.0
  • Subnet IP Address range is 192.168.2.0
    192.168.2.15 or Mask 255.255.255.240

143
IP Address, Subnet Mask and Gateway
Internet Protocol
  • IP Address and Subnet Mask define the Subnet
  • For Example IP address 172.31.1.0 and Subnet Mask
    of 255.255.240.0 means that the subnet address
    ranges from 172.31.0.0 to 172.31.15.255
  • Another notation is 172.31.1.0/28
  • The first Address is the Network Address and the
    last Address is the Broadcast Address. They are
    reserved and cannot be assigned to any node.
  • The Gateway Address is the Address of the router
    where the packet should be sent in case the
    destination host does not belong to the same
    subnet

144
IP Configuration of an Interface
Internet Protocol
Static
DHCP
145
ARP
Internet Protocol
  • ARP (Address Resolution Protocol) is used in
    Ethernet Networks to find the MAC address of a
    node given its IP address.
  • Source node (say 192.168.2.32) sends broadcast
    message (ARP Request) on its subnet asking Who
    is 192.168.2.33.
  • All computers on subnet receive this request
  • Destination responds (ARP Reply) since it has
    192.168.2.33
  • Provides its MAC address in response

146
IPv6
Internet Protocol
  • Internet Protocol Version 4 is the most popular
    protocol in use today, although there are some
    questions about its capability to serve the
    Internet community much longer.
  • IPv4 was finished in the 1970s and has started to
    show its age.
  • The main issue surrounding IPv4 is addressingor,
    the lack of addressingbecause many experts
    believe that we are nearly out of the four
    billion addresses available in IPv4.
  • Although this seems like a very large number of
    addresses, multiple large blocks are given to
    government agencies and large organizations.
  • IPv6 could be the solution to many problems posed
    by IPv4

147
IPv6
Internet Protocol
  • IPv6 uses 128 bit address instead of 32 bit
    address.
  • The IPv6 addresses are being distributed and are
    supposed to be used based on geographical
    location.

148
Routing
  • ROUTING

149
Router
Routing
  • A router is a device that determines the next
    network point to which a packet should be
    forwarded toward its destination
  • Allow different networks to communicate with each
    other
  • A router creates and maintain a table of the
    available routes and their conditions and uses
    this information to determine the best route for
    a given packet.
  • A packet will travel through a number of network
    points with routers before arriving at its
    destination.
  • There can be multiple routes defined. The route
    with a lower weight/metric will be tried first.

150
Routing
Routing
151
Routing Protocols
Routing
  • Static Routing
  • Dynamic Routing
  • IGP (Interior Gateway Protocol) Route data
    within an Autonomous System
  • RIP (Routing Information Protocol)
  • RIP-2 (RIP Version 2)
  • OSPF (Open Shortest Path First)
  • IGRP (Interior Gateway Routing Protocol)
  • EIGRP (Enhanced Interior Gateway Routing
    Protocol)
  • IS-IS
  • EGP (Exterior Gateway Protocol) Route data
    between Autonomous Systems
  • BGP (Border Gateway Protocol)

152
Internetworking Devices
Internetworking Devices
Device Description
Hub Hubs are used to connect multiple users to a single physical device, which connects to the network. Hubs and concentrators act as repeaters by regenerating the signal as it passes through them.
Bridge Bridges are used to logically separate network segments within the same network. They operate at the OSI data link layer (Layer 2) and are independent of higher-layer protocols.
Switch Switches are similar to bridges but usually have more ports. Switches provide a unique network segment on each port, thereby separating collision domains. Today, network designers are replacing hubs in their wiring closets with switches to increase their network performance and bandwidth while protecting their existing wiring investments.
Router Routers separate broadcast domains and are used to connect different networks. Routers direct network traffic based on the destination network layer address (Layer 3) rather than the workstation data link layer or MAC address.
153
VLAN
  • VLAN

154
VLANs
VLAN
  • VLANs (Virtual LAN) enable network managers to
    group users logically (based on functions,
    project teams or applications) rather than by
    physical location.
  • Traffic can only be routed between VLANs.
  • VLANs provide the segmentation traditionally
    provided by physical routers in LAN configuration.

155
VLANs and Inter VLAN Routing
VLAN
156
Advantages of Using VLANs
VLAN
  • Broadcast Control Just as switches physically
    isolate collision domains for attached hosts and
    only forward traffic out a particular port, VLANs
    provide logical bridging domains that confine
    broadcast and multicast traffic to the VLANs.
  • Security If you do not allow routing in a VLAN,
    no users outside of that VLAN can communicate
    with the users in the VLAN and vice versa. This
    extreme level of security can be highly desirable
    for certain projects and applications.
  • Performance You can assign users that require
    high-performance or isolated networking to
    separate VLANs.

157
TCP/UDP
  • TCP/UDP

158
TCP/UDP
TCP/UDP
  • Transport Layer Protocol
  • TCP is connection Oriented (uses checksum and
    acknowledgment)
  • UDP is Connectionless
  • Both use the concept of Connection Port Number
    (16 Bit Source Port Number and Destination Port
    Number)
  • Standard Applications have standard Port Numbers
    (Email 25, Telnet 23, FTP 20 21, SSH 22)

159
Natting
  • NATTING

160
Private vs Public IP Addresses
Natting
  • Whatever connects directly into Internet must
    have public (globally unique) IP address
  • There is a shortage of public IPv4 address
  • So Private IP addresses can be used within a
    private network
  • Three address ranges are reserved for private
    usage
  • 10.0.0.0/8
  • 172.16.0.0/16 to 172.31.0.0/16
  • 192.168.0.0/24 to 192.168.255.0/24
  • A private IP is mapped to a Public IP, when the
    machine has to access the Internet

161
NAT
Natting
  • NAT (Network Address Translation) Maps Private
    IPs to Public IPs
  • It is required because of shortage of IPv4 Address

162
NAT
Natting
  • Static NAT Maps unique Private IP to unique
    Public IP
  • Dynamic NAT Maps Multiple Private IP to a Pool
    of Public IPs (Port Address Translation Maps a
    Public IP and Port Number to a service in Private
    IP)

163
SNMP
  • SNMP

164
Simple Network Management Protocol
SNMP
  • SNMP is a framework that provides facilities for
    managing and monitoring network resources on the
    Internet.
  • Components of SNMP
  • SNMP agents
  • SNMP managers
  • Management Information Bases (MIBs)
  • SNMP protocol itself

165
SNMP
SNMP
  • SNMP is based on the manager/agent model
    consisting of a manager, an agent, a database of
    management information, called as MIB.
  • The manager provides the interface between the
    human network manager and the management system.
  • The agent provides the interface between the
    manager and the physical device(s) being managed.

166
SNMP
SNMP
  • SNMP uses five basic messages (GET, GET-NEXT,
    GET-RESPONSE, SET, and TRAP) to communicate
    between the manager and the agent.
  • The GET and GET-NEXT messages allow the manager
    to request information for a specific variable.
    The agent, upon receiving a GET or GET-NEXT
    message, will issue a GET-RESPONSE message to the
    manager with either the information requested or
    an error indication as to why the request cannot
    be processed.
  • A SET message allows the manager to request a
    change be made to the value of a specific
    variable in the case of an alarm remote that will
    operate a relay. The agent will then respond with
    a GET-RESPONSE message indicating the change has
    been made or an error indication as to why the
    change cannot be made.
  • The TRAP message allows the agent to
    spontaneously inform the manager of an
    important event.

167
VPN
  • VPN

168
VPN
VPN
  • VPN is a private connection between two systems
    or networks over a shared or public network
    (typically Internet).
  • VPN technology lets an organization securely
    extend its network services over the Internet to
    remote users, branch offices, and partner
    companies.
  • In other words, VPN turns the Internet into a
    simulated private WAN.
  • VPN is very appealing since the Internet has a
    global presence, and its use is now standard
    practice for most users and organizations.

169
VPN
VPN
170
How VPN Works
VPN
  • To use the Internet as a private Wide Area
    Network, organizations may have to address two
    issues
  • First, networks often communicate using a variety
    of protocols, such as IPX and NetBEUI, but the
    Internet can only handle TCP/IP traffic. So VPN
    may need to provide a way to pass non-TCP/IP
    protocols from one network to another.
  • Second data packets traveling the Internet are
    transported in clear text. Therefore, anyone who
    can see Internet traffic can also read the data
    contained in the packets. This is a problem if
    companies want to use the Internet to pass
    important, confidential business information.

171
How VPN Works
VPN
  • VPN overcome these obstacles by using a strategy
    called Tunneling. Instead of packets crossing the
    Internet out in the open, data packets are fist
    encrypted for security, and then encapsulated in
    an IP packet by the VPN and tunneled through the
    Internet.
  • The VPN tunnel initiator on the source network
    communicates with a VPN tunnel terminator on the
    destination network. The two agree upon an
    encryption scheme, and the tunnel initiator
    encrypts the packet for security.

172
Advantages of Using VPN
VPN
  • VPN technology provides many benefits. Perhaps
    the biggest selling point for VPN is cost
    savings. One can avoid having to purchase
    expensive leased lines to branch offices or
    partner companies. On another cost-related note,
    you can evade having to invest in additional WAN
    equipment and instead leverage your existing
    Internet instal
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