Computer Network Tutorial

Introduction of Computer Network Types of Computer Network Network Topology Computer Networking Architecture Transmission Modes (Data Flow) Basic Networking Devices Integrate Services Digital Network (ISDN)

Model

OSI Model TCP/IP Model

Physical Layer

Digital Transmission Analog Transmission Transmission Media Switching

Data Link Layer

Error detection and Error correction Data Link Control Multiple Access Aloha

Network Layer

Network Layer - Logical Address Address Mapping Unicast Routing Protocol

Transport Layer

Process to Process Delivery User Datagram Protocol Transmission Control Protocol Stream Control Transmission Protocol Session Layer and Presentation Layer

Application Layer

Domain Name System Application Protocol E-mail Cryptography

Misc

Classes of Routing Protocols Classification of Routing Algorithms Controlled Access Protocols in Computer Networks Differences between IPv4 and IPv6 Fixed and Flooding Routing Algorithms Advantages and Disadvantages of Fibre Optics Cable APIPA Difference between Active and Passive FTP Fiber Optics and its Types Method of Joining and Fusion of Fiber Optic Cable Define Framing in Computer Network Disadvantages of Computer Network Mesh Topology Diagram in Computer Network Ring Topology in Computer Network Star Topology in Computer Networks 4G Mobile Communication Technology Advantages and Disadvantages of LAN Advantages and Disadvantages of MAN Advantages and Disadvantages of WAN Application Layer in OSI Model Cyclic Redundancy Check Example Data link layer in OSI model Difference between Transport and Network Layer Hamming Code Example Network Layer in OSI Model Session Layer in OSI Model Transport Layer in OSI Model Two Port Network in Computer Networks Uses of Computer Networks What is Computer Network What is Framing in a Computer Network Advantages and Disadvantages of Bus Topology Difference between Star Topology and Bus Topology Subnetting in Computer Network Subnetting Questions and Answers What is Bus Topology What is Network Topology and Types in Computer Networks Access Control in Networking Basic Characteristics of Computer Network Benefits of SOCKS5 Proxy in Computer Networks Computer Network viva Questions Difference between BOOTP and RARP Difference Between Network Topologies and Network Protocols Difference between NFC and RFID Difference Between Point-to-Point Link and star Topology Network Differences Between MSS and MTU Differences Between Trunk Port and Access Port Different Modes of Communication in Computer Networks MIME Protocol in Computer Networks Modes of Communication in Computer Networks Network Attack in Computer Network Port Address in Networking Simplest Protocol in Computer Network Sliding Window Protocol in Computer Network Stop And Wait Protocol in Computer Networks TCP 3-Way Handshake Process in Computer Networks What is a Proxy Server What is APPN What is ICMP Protocol What is Point-to-Point Protocol What is Port Address in Networking What is the HDLC Protocol What is VRRP Protocol Difference Between Analog and Digital Signals Difference Between Hub and Repeater Difference between Repeater and Switch Difference Between Transparent Bridge and Source Routing Bridge Source Routing Bridge in Computer Networks Transparent Bridge in Computer Networks Transport Protocol in Computer Networks Types of CSMA in Computer Networks What is Wired and Wireless Networking Network Security in Computer Network Disadvantages of Extranet Difference Between TELNET and FTP Define Protocol in Computer Networks Guided Transmission Media in Computer Network What is a Gateway in a Computer Network IGMP in Computer Networks LAN Protocols in Computer Networks MAN Meaning in Computer Modulation Techniques in Computer Networks Switching in DCN TCP/IP Applications What is IGMP? What is Modem in Networking What is Non-Persistent CSMA Difference between Cell Splitting and Cell Sectoring Forouzen Computer Network Open Loop and Closed Loop Congestion Control Types of Cluster Computing WAP-Wireless Access Point What are the elements of the Transport Protocol Difference between Gateway and Switch Flow Control in Data Link Layer Body Area Network Flooding in Computer Network Token Ring in Computer Networks VoIP in Computer Networks What is Infrared Transmission Congestion Control Techniques Forward Error Correction (FEC) Switching Techniques What is Telnet in Computer Network What are the Types of IPv4 Addresses IEEE 802.6 (DQDB) IEEE 802.15.4 Technology What is HDLC (High-level Data Link Control)? What is SMS Hubbing in Telecom? Circuit Switching in Computer Networks Communication Satellites in Computer Networks Features of HTTP Protocol IMAP4 (Internet Message Access Protocol) Internet Services How to Set up a Wireless Router Internetwork Routing in Computer Networks Distributed Computing System Features of GSM The 802.11 MAC Sublayer Protocol What is IEEE 802.3? What are Hubs and Switches in Computer Networks? What is Modem in a Computer Network? What is multicasting in Computer Networks? GSM -The Mobile Station What is Network Server? Slotted Aloha in Computer Network What is Ethernet in Computer Networks What is Arpanet? Radio Access Network (RAN) TCP 3-Way Handshake Process PING SWEEP (ICMP SWEEP) Print Server Private IP Address Security Services in Computer Networks Protocol Data Unit (PDU) CSMA with Collision Avoidance (CSMA/CA) What is Gateway in Computer Network? Advantages of Networking Data Link Layer Design Issues DHCP in Computer Networks Internet Security Association and Key Management Protocol (ISAKMP) What is Switch Hub? Telnet Full form in Networking Multimedia Systems Quality of Service in Computer Networks What is Carrier Sense Multiple Access (CSMA)? What is Circuit Switching What is Duplex Network? What is Web Protocol Network LAN Technologies Classes in Computer Network Low-Density Parity Check (LDPC) Wireless Internet Service Providers(Wisps) What is Handshaking? Cache Server What Is WSN Network? Check Sum Error Detection Linear Bus Topology Functions of the Transport Layer Infrared Transmission in Computer Networks Digital Signal in Computer Network Digital Data Transmission in Computer Networks Define Checksum with Example Computer Network Security Requirements Brust Errors in Computer Network Back Side Bus (BSB) 2-Dimension Parity Check in Computer Network Router and Brouter Microwave Transmission in Computer Networks Magnetic Media in Computer Network A One-Bit Sliding Window Protocol CDMA-Near-Far Problem Reference Models in Computer Networks Uni-cast, Broadcast, and Multicast in Computer Networks Uses Of Bridges in Computer Networks What are Gateways in Computer Network?

Data Link Control

Data-link control is the main function of the data link layer. It deals with the configuration and coordination for connection between two neighboring nodes: node-to-node communication. The task of the data link layer includes error-control, software-implemented protocols, flow-control, and framing that provide efficient and smooth transmission of frames between nodes.

Framing

The data link layer separates the bit-stream obtained from the network layer into usable data units called frames.

Data Link Control

Flow control

Flow control is one of the essential duties of the data link layer. It manages the amount of data that can be sent before obtaining confirmation. Flow control is a set of methods that tell the sender how much data it can transmit before the receiver is overloaded. Any receiving device has limited speed and limited memory for the process of incoming data and storage of the incoming data.

Data Link Control

 Error control

Error control includes both methods of error detection and error correction. The error control helps the receiver to notify the sender of any lost frames or damaged frames during the transmission. It allows to retransmission of those frames by the sender. At the data link layer, error control is often easily implemented: whenever an error is detected at the frames, those frames are re-transmitted.

Protocols

The protocols usually use one of the common programming languages to execute the software. Protocols are divided into two categories: Noiseless channel and Noisy channel. The diagram of protocols structure is shown below.

Data Link Control

Noiseless channel

The noiseless channel is divided into two sub-categories: Simplest protocol and Stop-and-Wait protocol. The first protocol of this channel does not use flow control, but the second protocol uses flow control.

Simplest Protocol

In this protocol, it doesn't use the flow and error control. It is a unidirectional protocol where data frames only travel from sender to receiver in one direction. The design of the simplest protocol with no flow control or error control is shown below.

Data Link Control

Algorithm

Sender-site algorithm for the simplest protocol

while(true)           // Repeat forever
{
WaitForEvent();       // Sleep until an event occurs  
If (Event (RequestToSend))   // There is a packet to send
{   
 GetData();  
 MakeFrame();   
 SendFrame();       // Send the frame}}

Receiver-site algorithm for the simplest protocol

while(true)             // Repeat forever
{
WaitForEvent();        // Sleep until an event occurs 
If (Event (ArrivalNotification))            // Data frame arrived
{          
ReceiveFrame();         
ExtractData();          
DeliverData();          // Deliver data to network layer}}

For example: The simplest protocol is very simple. The sender sends frames in the sequence without really knowing about the receiver. In this protocol to send three frames, there are three events at the sender and three events at the receiver. These events are shown below in the figure.

Stop-and-Wait Protocol

The sender sends a frame in the Stop-and-Wait protocol, and it stops until when the receiver receives the data and then sends the next frame. In this protocol, adds the flow control. This protocol is a unidirectional protocol for data frames, but auxiliary ACK (Acknowledgment) frames travel from other directions. The design of the Stop-and-Wait protocol is shown below.

Data Link Control

Algorithm

Sender-site algorithm for the simplest protocol

while (true)              // Repeat forever
canSend = true           // Allow the first frame to go 
{      
WaitForEvent ( );             // Sleep until an event occurs    
If (Event (RequestToSend) AND canSend)          
  {            
GetData ( );          
MakeFrame ( );          
SendFrame ( );                   // Sleep the data frame       
canSend = false;                // Cannot send until ACK arrives            
 }
WaitForEvent ( );               // Sleep until an event occurs  
    if (Event (ArrivalNotification))              // An ACK has arrived           
 {             
    ReceiveFrame ( );  
       // Receive the ACK frame           
      canSend = true;      
      }
}

Receiver-site algorithm for the simplest protocol

while (true)                  // Repeat forever{                                
 WaitForEvent ( );         // Sleep until an event occurs     
 If (Event (ArrivalNotification))      // Data frame arrives  
   {   
ReceiveFrame ( );    
ExtractData ( );        
Deliver (data);         // Deliver data to network layer           
SendFrame ( );        // Send an ACK frame   
   }
}

For example: The stop-and-wait protocol is very simple. The sender transmits a frame and wait for the receiver response. The sender transmits the next frame after arrives the ACK of the previous frame.

Note that sending three frames in this example involves the sender in six events and the receiver in three events. These events are shown below in the figure.

Data Link Control

Noisy Channels

The noisy channel is divided into three sub-categories:

  1. Stop-and-Wait automatic repeat request
  2. Go-back-N automatic repeat request
  3. Selective repeat automatic repeat request

Stop-and-Wait Automatic Repeat Request

Stop-and-wait automatic repeat request is a protocol that is used in tele-communications to transfer the data between two connected systems. 

In the stop-and-wait automatic repeat request protocol, the sender sends one frame at a time. The sender transmits a frame and waits for the receiver response. The sender transmits the next frame after it arrives acknowledgment (ACK) signal of the previous frame. When the acknowledgment (ACK) does not reach the sender within a specified time, the sender sends the same frame again.   

At the end of each frame, the sender adds redundancy bits. At the receiver-end, these redundancy bits are used to check the damage of the frames.

In this protocol, we need a sequence number for the frames. The design of the Stop-and-Wait ARQ protocol is shown below.

Data Link Control

Algorithm

Sender-site algorithm for the Stop-and-wait ARQ protocol

Sn = 0;            //Frame 0 should be sent first    
canSend = true;     // Allow the first request to go 
while (true)         // Repeat forever
{    
 WaitForEvent ();       // Sleep until an event occurs     
  if (Event  (RequestToSend) AND canSend)      
 {             GetData (); 
    MakeFrame (Sn);                 // The seqNo is Sn           
  StoreFrame (Sn);              // Keep copy             
 SendFrame (Sn);           
  StartTimer ();            
 Sn = Sn + 1 ;           
 canSend = false ;      
 }    
 WaitForEvent ();                // Sleep        
 if (Event  (ArrivalNotification) )      // An ACK has arrived       
{             
ReceiveFrame (ackNo) ;         // Receive the ACK frame            
 if (not corrupted AND ackNo == Sn)    // valid ACK                   
{            
  Stoptimer ();          
 PurgeFrame ( Sn-1 ) ;            // copy is not needed                           
canSend = true ;                   
 }         
}        
if ( Event (TimerOut))            // The timer expired        
 {              
 StartTimer () ;              
 ResendFrame (Sn-1) ;         
 }
}                             

Receiver-site algorithm for the Stop-and-Wait ARQ protocol

Rn = 0 ;             // Frame 0 expected to arrive 
firstwhile ( true )
 {       
 WaitForEvent() ;       // Sleep until an event occurs       
 if ( Event (ArrivalNotification) )   // Data frame arrives        
   {         ReceiveFrame () ;    
  if (corrupted (frame) );      
      Sleep () ;          
 if ( seqNo == Rn )        // Valid data frame                  
  {           
  ExtractData () ;        
   DeliverData () ;            // Deliver data             
     Rn = R +  1 ;                 
    }       SendFrame (Rn) ;     // Send an ACK           
  }
}          

 The example of Stop-and-Wait ARQ is shown below in the figure.

Data Link Control

Go-Back-N ARQ

Go-Back-N ARQ protocol is also known as Go-Back-N Automatic Repeat Request. It is a data link layer protocol that uses a sliding window method. In this, if any frame is corrupted or lost, all subsequent frames have to be sent again.

The size of the sender window is N in this protocol. For example, Go-Back-8, the size of the sender window, will be 8. The receiver window size is always 1.

If the receiver receives a corrupted frame, it cancels it. The receiver does not accept a corrupted frame. When the timer expires, the sender sends the correct frame again. The design of the Go-Back-N ARQ protocol is shown below.

Data Link Control

The example of Go-Back-N ARQ is shown below in the figure.

Data Link Control

Selective Repeat ARQ

Selective Repeat ARQ is also known as the Selective Repeat Automatic Repeat Request. It is a data link layer protocol that uses a sliding window method. The Go-back-N ARQ protocol works well if it has fewer errors. But if there is a lot of error in the frame, lots of bandwidth loss in sending the frames again. So, we use the Selective Repeat ARQ protocol. In this protocol, the size of the sender window is always equal to the size of the receiver window. The size of the sliding window is always greater than 1.

If the receiver receives a corrupt frame, it does not directly discard it. It sends a negative acknowledgment to the sender. The sender sends that frame again as soon as on the receiving negative acknowledgment. There is no waiting for any time-out to send that frame. The design of the Selective Repeat ARQ protocol is shown below.

Data Link Control

The example of the Selective Repeat ARQ protocol is shown below in the figure.

Data Link Control

Piggybacking

It is used to increase the performance of the bidirectional protocols. In piggybacking, if node A sends a data to node B, it can also give the node-A information about the frame coming (or lost) from node B. if node B sends a data to node A, it can also give the node B information about the frame coming from node A.