Data Link Layer Protocols PDF

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The second layer, after the Physical Layer, is the Data Link layer. It is responsible for the creation and interpretation of different frame types based on the actual physical network being used. For instance, Ethernet and Token-ring networks support different and numerous frame types,  and the Data link layer must understand the difference between them.

The layer is also responsible for interpreting what it receives from the physical layer, using low-level error detection and correction algorithms to determine when the information needs to be re-sent.

Network protocols including the TCP /IP protocol suite, don’t define physical standards at the physical or Data Link layer,  but instead are written to make use of any standards that may currently be in use.

This is an overview of the Data Link Layer Protocols PDF, if you want to read full article in pdf, we have provided download link below.

How the Data Link Layer works:

The physical layer ensures bit synchronization. It also places the received finery pattern into the buffer. It notifies the data link layer that a frame has been received after decoding the incoming signal into a bitstream. Thus, the physical layer helps in the transmission and delivery of a stream of bits across the medium.

Then comes the Data Link Layer; this layer examines the Frame Check Sequence (FCS) in the trailer to determine whether any errors have occurred in transmission (i.e. the process of error detection). If an error has occurred, the frame is discarded. (Some data link protocols perform error recovery, and some do not.) The data link address(es) are examined so that Host B can decide whether to process the data further. If the data is addressed to host B, the data between the Layer 2 header and trailer is given to the Layer 3 software. The data link has delivered the data across that link.

This is an overview of the Data Link Layer Protocols PDF, if you want to read full article in pdf, we have provided download link below.

The following are the basic functions of data-Link Layer:

  • Arbitration- Determines when it is appropriate to use a physical medium.
  • Physical Addressing- Ensures that the correct recipient(s) receives and processes the data that is being sent. This is ensured by adding the header to a frame so that the physical address of the sender or receiver of the frame is defined.
  • Error detection- Determines Whether the data made the trip across the medium successfully. This is achieved by adding a trailer at the end of the frame. Duplicated frames are also avoided using this mechanism. This layer adds such a mechanism to avoid duplicate frames.
  • Access control- This layer has certain protocols which help in determining which devices have control over the link at a point of time when two or more devices are connected to the same link.
  • Flow control- This mechanism designed to prevent the receiver from being overburdened or to avoid the traffic jams at the receiver’s end. Flow control avoids a fast transmitter from overrunning a slow receiver by buffering the extra bits being sent.

Like most other layers, the Data Link Layer adds its own set of ‘control information’ to the front of the data packet (header) and at the end of the data packet (trailer). This information may include a  source and destination address  (hardware or  MAC address),  frame length, the indication of protocols used by a higher layer,  frame check sequence (FCS), etc.

This is an overview of the Data Link Layer Protocols PDF, if you want to read full article in pdf, we have provided download link below.

The following network connectivity devices are normally associated with the OSI Data Link layer:

  • Bridges. Bridges connect two separate networks to form a logical one by operating at the data link layer of the OSI model. Bridges rely on MAC addresses for their operation. Unlike repeaters, bridges examine the packet’s destination address before forwarding it to other segments. It extends the maximum distance of your network by connecting separate network segments and selectively passes signals from one medium segment to another.
  • A switch is a big brother of the bridge. The switch is nothing but a large multiport bridge. The switch operates at layer 2 of the OSI model just like a bridge that MAC addresses to determine where to forward the packet.
  • Intelligent Hubs
  • Network interface boards.

The four functions  (mentioned above)  of the Data  Link layer are normally split between the following two sub-layers.

  1. Media Access Control (MAC). This sublayer controls the way transmitters share signal transmission channels. It includes Logical Topology, Media Access, and Addressing.

In the Physical Layer, we had physical connection topologies, such as Star, Bus, Mesh, etc. But a physical network topology will not reflect the way the network operates. The actual path which is a signal actually takes is called a logical topology.

This is an overview of the Data Link Layer Protocols PDF, if you want to read full article in pdf, we have provided download link below.

Logical topologies use specific rules which control things when network entities are allowed to transmit data signals. This control process is called Media Access.

Addressing: Computer network entities need some way  49  distinguish devices on the network. This is done through addressing. The Data Link Layer is only concerned with physical device addresses.

  1. Logical Link Control (LLC). This sub-layer of the Data Link Layer helps in establishing and maintaining the link for transmitting data frames from one device to the next. Transmission Synchronisation and Connection Services are the topics covered under this sub-layer.

The second layer of the Open Systems Interconnection (OSI) Model is the Data Link Layer. This layer works with the functions provided by the physical layer below it and provides the functions to be used by the Network layer. To know more about the Data Link Layer in the OSI Model in Networking, keep reading this article till the end.

It is basically a protocol layer designed for transferring data between network nodes that are adjacent to each other in both the Wide Area Network (WAN) and Local Area Network (LAN).

The physical layer has been given the responsibility of detecting and correcting errors that might occur in the process of the data transmission but just as a doctor can’t treat his own illness, the physical layer cannot detect and correct the error that may occur in the physical layer. So, the Data Link Layer detects and corrects the error in the Physical Layer.

The protocol data units, which is delivered by this layer is called Data Link Frames. The transmission of these units is done within a local network area (LAN) and the delivery of these frames is possible only between the nodes that are on the same level of the network.

The connection between the nodes can consist of more than one physical line. Some of the options of these physical lines are optical fiber cable, satellite channels, copper and wire cables, and microwave link.

Data link layer in osi model in networking

The two sub-layers of the Data Link Layer are Logical Link Control and Media Access Control. As suggested by the name itself, Media Access Control deals with the control of media and the previous sub-layer handles protocols, flow control and error control.

This is an overview of the Data Link Layer Protocols PDF, if you want to read full article in pdf, we have provided download link below.

Also, read…

The functions and services provided by the Data Link Layer are the following:

    1. The Data Link Frames are made from the data received from the Network Layer and the forming of the frame is achieved by breaking the data into small manageable units.
    2. Not only it receives data from Network Layer, but it also permits the transfer of data to it like a two-way road with a barricaded checking point.
    3. It is a reliable source as the delivery service data because of its’ errorless transmission service over the links.
    4. The buffer of the receiver can be overflowed with frames and as a result, a lot of frames can be lost. This layer provides the solution for that as well in the form of flow control in which it prevents the sending node from overwhelming the receiver node.
    5. Half Duplex and Full Duplex services are also provided by the Data Link.

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