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 Layer Design Issues

Introduction

Data Link Layer Design Issues/>
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<p>The International Organization for Standardization (ISO) established the OSI (Open Systems Interconnection) Model in 1984, marking a watershed moment in the evolution of networked systems and services. In particular, the OSI Model provides a conceptual framework for describing the key components and functionality of networked systems. It contributes to the development of network protocols and enhances interoperability across heterogeneous networks.</p>
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<p>The paradigm defines seven abstract layers of networked functionality: <strong>the Physical Layer, Data Link Layer, Network Layer, Transport Layer, Session Layer, Presentation Layer, & Application Layer.</strong> Each layer applies functionality to the sent data, which means it sends and processes networked communication data using the proper hardware, software, and middleware implementations.</p>
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<p>Over time, various networked devices and systems have been built and developed using the OSI paradigm. As a result, network designers, network service providers, & network operators were able to offer feedback on the practical implementation and application of functions across the aforementioned layers. In this context, some layers are seen more important and frequently used than others. Some layers are required for any network system, whereas others (such as the Presentation layer) are rarely used. One of the most important layers is the Data Link Layer (layer 2), which is commonly deployed and used.</p>
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<h2 class=Data Link Layer Design Issues
  1. Service Provided to Network Layer
  2. Framing
  3. Error Control
  4. Flow Control
  5. Media Access Control

1. Service Provided to Network Layer

In the OSI model, the Data Link layer is between the physical and network layers. As a result, it gets bits from the physical layer & ensures that they are delivered to the network layer in the right format. When sending data, messages use network layer services first, then data link layer services, and finally convey data through the physical layer. At the receiving end, the reverse process is taken: bits from the physical layer are transmitted to the data link layer, which then forwards the message to the network layer. Thus, the data link layer acts as an intermediary between the physical and network layers, ensuring the dependability of delivery by organizing the data into well-defined frames.

The data link layer ensures that the network layer receives the sender's data without loss. It can also create a logical communication channel among the sender and receiver of a message by monitoring a virtual link between them. The Data Link Layer manages virtual connections. In this perspective, the data link layer offers the network layer the following sorts of services:

Unacknowledged Connectionless Service:

In this case, the source machine sends data frames to the destination machine without anticipating acknowledgement from them. The most common example of an unacknowledged connectionless service is Ethernet.

In Ethernet, no logical link is established between the sender and recipient. Neither receiver acknowledges the received frames. The sender makes no attempt to detect or recover any missing frames.

Note: This type of connection is useful where the channel's error rate is low.

Acknowledged Connectionless Service:

Similar to the preceding service, this service does not establish or maintain any virtual connection among sender and receiver. Nevertheless, unlike the prior service, the receiver confirms packet delivery. As a result, the sender knows whether the data it transmitted was received elegantly and safely. Because there is no virtual connection between sender and recipient, each frame is acknowledged independently.  If no acknowledgement is received within a set time interval, the sender resends the data frame. In this way, this service outperforms the unacknowledged connectionless service in terms of reliability. Acknowledged connectionless services are frequently employed over unstable physical channels, such as larger Wi-Fi networks.

Acknowledged connection-oriented service:

This service creates a logical connection among the server & the receiver. The establishment occurs prior to the transport of any data. As a result, data is transmitted over the established logical link. Furthermore, as part of this service, frames are tagged with suitable numbers to ensure that each frame is only received once, while also certifying their proper order & sequence.

2. Framing

Framing is one of the design difficulties with the data link layer. We previously described how the data link layer divides the stream of bits from the network layer into individual frames. But do you understand why it does this?

Data Link Layer Design Issues/>
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<p><strong>Need for Framing</strong></p>
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<p>We know that the data link layer makes use of the physical layer's resources. The physical layer simply accepts the raw bit stream and sends it to its destination. It is possible that the physical layer, such as cable or wireless networks, is noisy, increasing the bit error rate.</p>
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<p>To lower bit error rates, the physical layer adds redundancy to the signals. However, this does not guarantee that the bit stream received at the destination data connection layer is devoid of errors. As a result, the detection and correction of mistakes falls to the data link layer.</p>
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<p>Framing is used to detect and correct mistakes in the bitstream data connection layer. While framing, the data connection layer divides the bit stream into discrete frames and calculates the checksum for each.</p>
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<p>When the data connection layer transmits the frame to the destination, it adds this checksum. When the frame reaches at its destination, the receiver recalculates the checksum, and if it differs, it indicates that the incoming frame included mistakes.</p>
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<p>These frames can now be classified into two types: <strong>fixed size & variable size frames.</strong></p>
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<p><strong>Types of frames</strong></p>
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<p>1. <strong>Fixed Length Frame</strong></p>
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    Fixed-size frames do not require any borders because their size serves as a delimiter.

    2. Variable Length Frame.

    With a variable-length frame, we must define the frame borders, i.e. the end of one frame and the start of the next. We have two ways for establishing the bounds of a variable length frame, which are explained below:

    Character-oriented Approach

    The character-oriented method was popular when the data link layer exchanged text information. In this manner, the data exchanged was 8 bits, and the information in the header and trailer should be a multiple of 8.

    To indicate the start and end of the frame, the sender's data connection layer adds an 8-bit flag. This flag could represent any charter that is not part of text communication.

    It is no longer limited to text-based communication. We're trading graphs, audio, and videos. The character chosen for the flag could be part of the data sent. So, we devised a new strategy: byte stuffing.

    Byte Stuffing

    We also refer to byte stuffing as "character stuffing." If a character in the data section matches the flag's pattern, the data link layer adds an extra byte to that part of the data section. We call this extra byte an escape character. The escape character uses a preset bit pattern.

    When this escape character is encountered at the receiver end, it will simply be removed, and the next character treated as data. Until it meets the last delimiter, i.e. flag.

    However, this solution had a drawback: what if the data section contained a character with the escape pattern? To resolve this issue, the character with the escape pattern is indicated with another escape character.

    Data Link Layer Design Issues/>
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<p>However, the character-oriented approach is losing ground on framing principles, as the universal coding scheme now supports 16-bit or 32-bit characters. That's why we need to adopt a bit-oriented approach.</p>
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<p><strong>Bit-oriented approach</strong></p>
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<p>In the character-oriented technique, we use a complete byte (8-bit flag plus escape character) to indicate the beginning and end of the frame. However, with the bit-oriented technique, we just stuff one bit. To avoid a portion of data from appearing as a flag, we use the bit-oriented strategy of stuffing a single bit 0 after 5 consecutive 1s.</p>
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<img src=

      The receiver enables the sender to convey additional data or, at the very least, keeps the sender updated on the receiver's performance.

      2. Rate-Based Flow Control

      This approach restricts the pace at which the transmitter can give data, ensuring that the receivers are not inundated with frames.

      So, these are the data link layer design issues that network designers must consider when developing the data connection layer. The data link layer is responsible for providing services to the network layer, such as framing, error correction, & flow control.

      5. Media Access Control

      Data link layer implementations for broadcast networks must also consider how various senders access the common channel. This is a common concern in Ethernet and other types of wireless networks. To solve this issue, several data link layer solutions include a specialized sublayer called the Medium Access Control (MAC) sublayer. The MAC implements techniques to control access to the shared physical medium.