Elec3030 el336 computer networks s chen framing data link layer is responsible for making physical link reliable and, to do so, it breaks up network layer data stream into small blocks, a process called segmentation, and adds header and frame. Layered network architecture, arq retransmission strategies, delay models for data networks, multiaccess communication, routing, congestion control and addressing. Data communication and computer networks pdf notes dccn. It provides a way for a sender to transmit a set of bits that are meaningful to the.
The data communication and computer networks notes pdf dccn pdf notes book starts with the topics covering communications, multiplexing and spreading, block coding, backbone. The data link layer software checks to see if this is the frame expected, and if so, gives the packet contained in the payload field to the routing software. Frames are the result of the final layer of encapsulation before the data is transmitted over the physical layer. Which provision can resolve overcome the shortcomings associated with duplication or failure condition of stop and wait automatic repeat request protocol especially due to loss of data frames or nonreception of acknowledgement. The data link layer needs to pack bits into frames, so that each frame is. It is called segment at transport layer, packet at the network layer, and it is referred to as frame in the data link layer. First, the data link layer at a sends a frame to the data link layer at b a router. This is at once a very specific yet very extensive topic. Pdf implementation of data link control protocols in wired network.
Data link protocols provide communication between two devices. While the data link layer sorted out an error free link between two. To send data from a to f, three partial deliveries are made. The main functions and the design issues of this layer are.
Frames have headers that contain information such as errorchecking codes. Worlds best powerpoint templates crystalgraphics offers more powerpoint templates than anyone else in the world, with over 4 million to choose from. However, these bits must be framed into discernible blocks of information. It contains multiple choice questions and answers about physical layer, data link layer. Data link layer 48 network layer 49 transport layer 51 session layer 53 presentation layer 54. Data link physical the seven layers of the osi model cont. In connectionless data transfer, data are transferred from one entity to another. In the osi model of computer networking, a frame is the protocol data unit at the data link layer. The llc sublayer is responsible for reliable transfer of frames between two directly connected entities. Data communication networks lecture notes download book. Which one of the following task is not done by data link. Framing the data link layer, needs to pack bits into frames, so that each frame is distinguishable from another. Ethernet, token ring, frame relay, and other data link layer technologies have their own frame structures.
This presentation covers the datalink layer of the networks. Pdf data link layer is the protocol layer which transfers data between connected networks. Data after being character stuffed by the data link layer. Asynchronous transfer mode connection oriented, highspeed network. Lecture notes data communication networks electrical. Winner of the standing ovation award for best powerpoint templates from presentations magazine. Data link layer 2 the data link layer takes the packet from the network layer and breaks it into frames. Reliable data transfer service between two peer network layers. The network layer is interested in getting messages to the corresponding network layer module on an adjacent machine. Here you can download the free lecture notes of data communication and computer networks pdf notes dccn notes pdf materials with multiple file links to download. In these computer networks notes pdf, we will study the concepts of data communication and computer networks which comprises of the study of the standard models for the layered protocol architecture to communicate between autonomous.
When a packet reaches the data link layer, it is encapsulated with a header and a trailer which you will see later to be called a frame. The data link layer takes the data bits and frames, and creates packets of the data to guarantee reliable transmission. The transmission over layer 1 is not necessarily free of errors. Mcq questions and answers on data communication and computer networks or multiple choice questions with answers on data communication and networks from chapter communication network fundamentals. This note covers the following topics related to computer networks.
Data link layer protocols that are reliant on a specific physical layer may be limited to the transmission medium involved, but, in some cases e. Computer networks pdf notes free download cn notes. The remote network layer peer should receive the identical message generated by the sender e. Byte oriented protocols frame is a collection of bytes and not bit stream sentinel approach use a special byte to mark beginning and end of frame example. Character based framing frame syn syn stx header packet etx crc syn syn syn is synchronous idle stx is start text etx is end text standard character codes such as ascii and ebcdic contain special communication characters that cannot appear in data. Topics in our studying in our computer networks notes pdf.
The routing software then chooses the appropriate outgoing line and passes the packet back down to the data link layer software, which then transmits it. Computer networking and management lesson 5 the data. Csma protocols collisionfree protocols limitedcontention protocols wireless lans. The link layer protocoldefines the format of the units of data frames exchanged between the nodes at the ends of the link, as well as the actions taken by these nodes when sending and receiving. Data communications and networking second edition fm page i wednesday, february 23, 2000 2. The llc sublayer adds a header and a trailer to the data.
Encapsulation and deencapsulation process the encapsulation and deencapsulation of. Often called layer 2 protocols, data link protocols exist in the protocol layer just above the physical layer relative to the osi protocol model. Find materials for this course in the pages linked along the left. Framing is a pointtopoint connection between two computers or devices consists of a wire in which data is transmitted as a stream of bits. Lecture slides from the 3rdyear module on computer networks at the university of birmingham, uk. It is an important topic both within the context of data.
Datalink layer powerpoint presentation free to download id. Eytan modiano slide 4 character based framing standard character codes such as ascii and ebcdic contain special communication characters that cannot appear in data entire transmission is based on a character code frame syn syn stx header packet etx crc syn syn. Provides connectivity and path selection between two host systems routes data packets selects best path to deliver data the network layer prioritizes data known as quality of service qos. Example a b c dle stx a dle bdleetx dle stx a dle dle b dle etx dle stx a dle bdleetx. This lecture notes explores data link layer dlc which is responsible for reliable transmission of packets over a link 1. The header in this layer provides the source and destination mac addresses. As shown on the above representation of the frame, the header and trailer are added to the already formed pdu, which is packet that contains data coming from the application layer down to the network layer.
Second, the data link layer at b sends a new frame to the data link layer at e. This layer converts the raw transmission facility provided by the physical layer to a reliable and error free link. The ethernet data link layer switching and frame syntax. Data assumed error free by higher layers errors occur at lower layers physical job for llc layer extra redundant bits added to data. The data link layer prepares a packet for transport across the local media by encapsulating it with a header and a trailer to. Government of india certification in basic network support. The subject of interest in this book is premises data communications using fiber optic cable as the transmission medium. To achieve this, the standard is based on the open system interconnection o. The adobe flash plugin is needed to view this content. Bisync binary synchronous communication protocol developed by ibm character stuffing.
It is general enough to give a broad overview of todays technologies and trends, while detailed enough for you to see the inner workings of modern networking. Data link layer design issues services framing error control flow control. It provides a way for a sender to transmit a set of bits that are meaningful to the receiver. Elec3030 el336 computer networks s chen data link layer.
It is the data link layer that will convert the data into binary digits such as 1 and 0 and then prepare them for the physical layer. Osi model 7 layers explained pdf layers functions the open systems interconnection model osi model is a conceptual model that characterizes and standardizes the communication functions of a telecommunication or computing system without regard to their underlying internal structure and technology. The data link layer in the osi open system interconnections model, is in between the physical layer and the network layer. The data link layer uses llc to communicate with the upper layers of the protocol suite. A frame is the unit of transmission in a link layer protocol, and consists of a link layer header followed by a packet. The content focuses on local area networks and the technology for connecting them together. We said in the previous lessons that data has different names at different layers. Data link layer protocols the data link layer provides service to the network layer above it. Error control deliver frames without error, in the proper order to. Which one of the following task is not done by data link layer a framing b. Handle transmission errors error control noisy links becomes error free as. Theyll give your presentations a professional, memorable appearance the kind of sophisticated look that todays audiences expect.
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