Data Link Control

Data Link Control. FramingParts of A FrameTypes of FramingIn the Physical layer data transmission means moving bits are in the form of a signal from the source to the destination The Physical layer also provides synchronization that mainly ensures that the sender and the receiver use the same bit durations and timings The bits are packed into the frames by the data link layer so that each frame is distinguishable from another frame TheFraming in the data link layer separates a message from one source to a destination orfrom other messages to other destinations just by adding a sender address and destination address where the destination address specifies where the packet has to go and the sender address helps the recipient to acknowledge the receipt Frames can be either of fixed size or of variable size By using frames the data can be easily get broken up into recoverable chunks and in order to check the corruption in transmission these chunks can be checked easily Different parts of a frame are as follows 1 Flag A flag is used to mark the beginning and end of the frame 2Header The frame header mainly contains the address of the source and the destination of the frame 3Trailer The frame trailer mainly contains the error detection and error correction bits 4Payload Field This field contains the message to be delivered Framing is mainly categorized into two parts 1 Fixedsize Framing 2 Variablesize Framing Let us cover the above given two types onebyone.

Data Link Control is the service provided by the Data Link Layer to provide reliable data transfer over the physical medium For example In the halfduplex transmission mode one device can only transmit the data at a time If both the devices at the end of the links transmit the data simultaneously they will collide and leads to the loss of the information The Data link layer provides the.

Computer Network Data Link Controls javatpoint

DLC (data link control) is the service provided by the Data Link layer of function defined in the Open Systems Interconnection ( OSI) model for network communication The Data Link layer is responsible for providing reliable data transfer across one physical link (or telecommunications path) within the network.

Datalink Control & Protocols Tutorialspoint

FramingFlow ControlError ControlProtocolsNoiseless ChannelSimplest ProtocolStopAndWait ProtocolNoisy ChannelsStopAndWait Automatic Repeat RequestGoBackN ArqThe data link layer separates the bitstream obtained from the network layer into usable data units called frames 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 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 retransmitted 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 The noiseless channel is divided into two subcategories Simplest protocol and StopandWait protocol The first protocol of this channel does not use flow control but the second protocol uses flow control 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 Algorithm Sendersite algorithm for the simplest protocol Receiversite algorithm for the simplest protocol 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 The sender sends a frame in the StopandWait 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 StopandWait protocol is shown below Algorithm Sendersite algorithm for the simplest protocol Receiversite algorithm for the simplest protocol For example The stopandwait 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 The noisy channel is divided into three subcategories 1 StopandWait automatic repeat request 2 GobackN automatic repeat request 3 Selective repeat automatic repeat request Stopandwait automatic repeat request is a protocol that is used in telecommunications to transfer the data between two connected systems In the stopandwait 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 receiverend 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 StopandWait ARQ protocol is shown below Algorithm Sendersite algorithm for the Stopandwait ARQ protocol Receiversite algorithm for the StopandWait ARQ protocol The example of StopandWait ARQ is shown below in the figure GoBackN ARQ protocol is also known as GoBackN 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 GoBack8 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 GoBackN ARQ protocol is shown below The example of GoBackN ARQ is shown below in the figure.