Computer Networks

• A group of computers connected for the purpose of sharing their resources is called computer networks.
• First Computer Network:ARPANET
• ARPANET:Advanced Research Project Agency Network

Characteristics

• Resource Sharing
• Communication Speed
• Backup
• Scalability
• Reliability
• S/W & H/W sharing
• Security

Network Devices

• Modem
• HUB
• Switch
• Gateway
• BRIDEGE
• Router
• Repeater

Network Types

• PAN : Personal Area Network

  • Range: <10 M
  • Used for personal use
  • Home

    graph LR;
    A[Bluetooth]-->B[Computer]
    C[Laptop]-->B
    B-->D[Speaker]
    B-->E[Wifi]
    
    

• LAN : Local Area Network

  • Range <150 m
  • Use:Office Building

    graph LR;
    A[Computer 1]-->B[Computer 3]
    C[Computer 2]-->B
    D[Computer 4]-->gt;A
    E[Computer 5]-->gt;B
    E-->A
    D-->B
    C-->A
    

• MAN :Metropolitan Area Network

  • Range <50 km

  • Used within a city

  • EX:Connection of LAN

    graph TD;
    A[College LAN]-->F
    B[School Lan]-->F
    C[Hospital Lan]-->F
    D[Temple LAN]-->F
    E[HOME LAN]-->F
    F[MAN]
    

• WAN: Wide Area Network

  • Range not fixed
  • used for countries or all around the world

    graph TD;
    A[LAN 1]-->F
    B[MAN 1]-->F
    C[LAN 2]-->F
    D[LAN 3]-->F
    E[MAN 2]-->F
    F[WAN]
    

Advantages

• Open to everyone
• file sharing
• open to everyone
• security
• backup storage
• easy to add new device

Disadvantages

• N/W device required
• virus attack
• required handler
• high speed internet required
• server

Devices

• HUB

  • Network device that is used to connect multiple computers in a network
  • All the infomation send to HUB are sent to each port of every devices
  • less expensive ,less intelligence,less expensive
  • generlly used to connect computers in LAN
  • Advantages:
    • Can broadcast the message
    • less expensive so anyone can use it
    • easy installation
    • robust
  • Dis-Advantages:
    • On HUB failure entire network will fail
    • We can't send private/personal data through hub
    • HUB doesn't provide any security
    • can't support full duplex transmission
  • Tranmission mode of HUB is Half Duplex
  • Half Duplex:
    • One process at a time (receive or send)

  • graph LR;
    A[HUB:PORTS:A+B+C+D ]-->C[Computer 1]
    A-->B[Computer 2]
    D[Computer 3]-->A
    E[Computer 4]-->A
    

• SWITCH:

  • Connect multiple computers in a network
  • used to send private messages
  • no wastage of data (ie: no broadcasting)
  • Easily identify which device is connected with which port by using MAC Adrresss
  • By this it deliveres messages where we want to send
  • more intelligent than HUB
  • Advantages
    • Generally used to unicast the message
    • provides more security than HUB
    • Provides duplex transmssion mode
    • used to send data packet based on MAC aadress
    • If a node fails then total network will not get distuurbed
  • Disadvantages
    • If switch fails total network loss
    • expensive
    • Difficult setup

  • graph LR;
    A[SWITCH:G1,G2 ]
    X[G1:A]-->C[Computer 1]
    Y[G1:B]-->B[Computer 2]
    Z[G2:E]-->D[Computer 3]
    W[G2:H]-->E[Computer 4]
    T[G1:PORTS:A+B+C+D]-->X
    T-->Y
    U[G2:PORTS:E+F+G+H]-->Z
    U-->W
    A-->T
    A-->U
    

• ROUTER

  • Work as traffic controller
  • choose a congestion free path through which the data packet will travel
  • receive data packet from sender analyse it and forward data packet to receiver by choosing congestion free path.
  • Uses both LAN and WAN
  • Advantages
    • Provides connection b/w two diff devices
    • congestionless
    • transmission rate very high
    • provides both wire and wireless facility
  • Disadvantages
    • more expension compared to others
    • complex to maintain
    • security issue
    • only works with routable protocol

  • graph LR;
    C[Computer 1]-->A
    D[Computer 2]-->A
    A-->E[Computer 3]
    A[HUB]-->B[ROUTER]
    A-->F[Computer 4]
    B--Traffic:1:less-->AA[so go]-->G[Router]
    B--Traffic:1,2,3,4-->G
    B--Traffic:1,2,3,4,5-->G
    I-->H[Computer 1]
    G-->I[HUB]
    I-->J[Computer 2]
    I-->K[Computer 4]
    I-->L[Computer 5]
    

• REPEATER

  • Boostup the weeken signals
  • Used in wired and wireless both
  • Advantages
    • Used to regenerate the weak signals
    • Cheaper
    • ability to extend the length of signal
    • increase /maintain the signal performance
  • Disadvantages
    • No of repeater too much required for some distances
    • unable to connect dissimilar type of N/W(Analog/Digital)
    • Can't reduce network traffic

• BRIDGE

  • Used to separate LAN in to number of Sections
  • Oprates both physical as well as data link layer of OSI model
  • Advantages:
    • Network extending
    • broadcast the data of each node like HUB and REPEATER
    • Collisions can be reduced easily
    • more Intelligent
  • Disadvantages
    • Doesn't estabish connection b/w two diff devices
    • epensives
    • transmission rate less than repeater
    • Non reversible(message sent can't be stopped)

  • graph LR;
    A[HUB] --> B[BRIDGE] --> C[HUB]
        subgraph X[Noted Data by Bridge]
        AY[BRIDGE]-->AA
        AY-->BB
        AA[MAC Addr.]
        BB[PORT No.]
        AA-->AX[19.63.373.8]
        AA-->BX[19.63.373.85]
        BB-->3000
        BB-->80
    
        end
    

• GATEWAY

  • Used to connect two difference type of devices(n/w)
  • allow us to send and receive data through the internet even it is LAN network
  • working same as SWITCH
  • Advantages:
    • Connect two networks of different protocol
    • operates all 7 layers of OSI model
    • can't access internet without a gateway
    • security
  • Disadvantages
    • expensive
    • data transmission rate slower
    • difficult to maintain and complex to use
    • less intelligent
  • operates all 7 layer of OSI Model

    graph LR;
    A[WAN SERVER]--d1:Gateway-->B[GATEWAY/SWITCH]
    B--d1-->C[G1]
    B--d2:Switch-->D[G2]
    B-->E[G3]
    C-->P11
    C-->P21
    D--d2-->P12
    D--d2-->P22
    E-->P13
    E-->P23
    P11--need outside data d1:Gateway-->Computer1
    P21-->Computer2
    P12--need d2 from c4-->Computer3
    P22--d2-->Computer4
    P13-->Computer5
    P23-->Computer6
    

• NIC

  • NIC:Network Interface Card
  • without NIC impossible to connect device with network/internet
  • Two Types:
    • Internal NIC
    • External NIC
  • INIC:MotherBoard has a slot for n/w card where it can be inserted
  • RJ45 n/w cable required in INIC
  • ENIC:
    • Wireless
    • USB Cable

• MODEM

  • Modulator & Demodulator
  • Placed b/w computer and telephone line
  • Modulator : Digital(0,1) to Analog(curvy)
  • Allow computer to connect internet
  • DeModulator:Analog(curvy) to Digital(0,1)

    graph LR;
    Sender-->Modulator--d to a-->Demodulator--a to d-->Receiver
    

Network Topology

• Physical arrangement of of the computer system/node which is connected to each other via communiation medium

• BUS TOPOLOGY

• STAR TOPOLOGY

• RING TOPOLOGY

• MESH TOPOLOGY

• HYBRID TOPOLOGY

• TREE TOPOLOGY

• BUS TOPOLOGY:

  • One long wire act as single communcation channel for all PC
  • Advantages
    • Single wire
    • any malicious node can be detached
    • less expensive
    • broadcasting can be done
    • easy to maintain
  • Disadvantage
    • Cable fail cause all to disconnect
    • due to broadcasting messages are not secure
    • cable length limited
    • time consuming in communication
    • data transmission only in one direction

  • graph LR;
    C1-->Wire
    C2-->Wire
    Wire-Start-->Wire
    C3-->Wire
    C4-->Wire
    Wire-->C5
    Wire-->C6
    Wire-->Wire-End
    Wire-->C7
    Wire-->C8
    

• RING TOPOLOGY

  • Advatnages:
    • Strong connection
    • Broadcast
    • Bidirectional
    • transmission rate very high
  • Disadvantages
    • Very difficult to add new network
    • if we want to send data not to adjacent that will cause unnecessary data transmission
    • single point of failure cause complete loss
    • Can't send private message

  graph LR;
  C1-->C2-->C3-->C1
  

• STAR TOPOLOGY

  • All nodes are connected to a central device called HUB

  • Advantages:

    • Broadcast
    • less cable
    • less expensive
    • easy to connect new node without affecting any one
    • single point failure not affect other

  • Disadvantages

    • must require a n/w device like switch hub etc
    • if two networks want to share data then it only be possible via hub
    • can't send private data
    • if hub fail then total loss

    graph LR;
    C1-->HUB
    C2-->HUB
    HUB-->C3
    HUB-->C4
    

• MESH TOPOLOGY

  • Each computer is directly connected with each other
  • Advantages
    • Very good topology to send private messages
    • each connected with each other so point to point connection
    • single failure can't affect all
    • multiple devices can send and receive data simultaneously
  • Disadvantages
    • Very difficult to add new node
    • if any one fail then we will not able to send or receive to or from failed device

  • graph LR;
    A-->B 
    A-->C
    A-->D
    A-->E
    B-->C
    B-->D
    B-->E
    C-->D
    C-->E
    D-->E
    

• HYBRID TOPOLOGY

  graph LR;
  MESH-->A[Computer]
  RING-->A
  STAR-->A
  BUSH-->A
  

• TREE TOPOLOGY

  • Combination of STAR and BUS topology
  • all the nodes are connected to a central device called HUB
  • HUB is connected to another HUB via cable
  • all the nodes are connected like branch of a tree
  • Advantages
    • Easy to extend
    • Easy to maintain
    • Easy to detect fault
    • Easy to add new node
  • Disadvantages
    • If root fail then total network fail
    • If cable fail then total network fail
    • If hub fail then total network fail
    • If any node fail then total network fail

   graph LR;
   A[Computer]-->B[Computer]
   B--BUS-->C
   C--BUS-->D
   A-->C[Computer]
   A-->D[Computer]
   B-->E[Computer]
   B-->F[Computer]
   C-->G[Computer]
   C-->H[Computer]
   D-->I[Computer]
   D-->J[Computer]
   E-->K[Computer]
   E-->L[Computer]
   F-->M[Computer]
   F-->N[Computer]
   G-->O[Computer]
   G-->P[Computer]
   H-->Q[Computer]
   H-->R[Computer]
   I-->S[Computer]
   I-->T[Computer]
   J-->U[Computer]
   J-->V[Computer]
   K-->W[Computer]
   K-->X[Computer]
   L-->Y[Computer]
   L-->Z[Computer]
  

  graph LR;
  A[Computer]-->B[Computer]
  A-->C[Computer]
  A-->D[Computer]
  B-->E[Computer]
  B-->F[Computer]
  C-->G[Computer]
  C-->H[Computer]
  D-->I[Computer]
  D-->J[Computer]
  E-->K[Computer]
  E-->L[Computer]
  F-->M[Computer]
  F-->N[Computer]
  G-->O[Computer]
  G-->P[Computer]
  H-->Q[Computer]
  H-->R[Computer]
  I-->S[Computer]
  I-->T[Computer]
  J-->U[Computer]
  J-->V[Computer]
  K-->W[Computer]
  K-->X[Computer]
  L-->Y[Computer]
  L-->Z[Computer]