Data link layer of osi reference model studytonight. In ieee 802 lanman standards, the medium access control mac, also called media access control sublayer is the layer that controls the hardware responsible for interaction with the wired, optical or wireless transmission medium. It adds a header and trailer to form an osi layer 2 pdu. The mac sublayer provides addressing and channel access control mechanisms that make it possible for. The data link layers first sublayer is the media access control mac layer. Provides synchronization between source and target nodes. Mac sublayer rgpv june 2011 in the sevenlayer osi model of computer networking, media access control mac data communication protocol is a sublayer of the data link layer layer 2. The mac layer provides addressing and channel access control mechanisms that make it possible for several terminals or network nodes to communicate within a multipoint network, typically a local area network lan or.
Was ist layer 2 data link layer, sicherungsschicht. It also shows how the data link layer divided into the llc and mac sublayers. The nic driver is a program that interacts directly with the hardware on the nic to pass the data between the mac sublayer and the physical media. Provides synchronization between source and target. The physical layer moves bits from one end of a cable to the other end.
The llc communicates with the network layer while the mac sublayer allows various network access technologies. The llc sublayer can then talk to a number of ieee 802 mac sublayers, which control access to the physical media for transport. Which layer does wireless communication rely heavily upon. The mac sublayer acts as an interface between the logical. The data link layer is actually divided into two sublayers. Physical addressing for network connections exists at the data link layer. Which two functions or operations are performed by the mac. Data link layer features deploying licensefree wireless.
The data link layer is the second layer in the osi open systems interconnection sevenlayer reference model. Mac may refer to the sublayer that determines who is allowed to access the media at any one time e. Logical link media access control mac link sublayers. At the data link layer, ethernet specifies what the data should look like, including the header and trailer. The mac sublayer is the interface between the physical layer and the llc sublayer. This post gives a brief overview of the two sublayers of the data link layer, namely llc logical link control and mac media access control. The llc communicates with the network layer while the mac sublayer allows. Then, it sends each frame bitbybit on the hardware. The mac sublayer and the logical link control llc sublayer together make up the data link layer.
What differs the llc sublayer from the mac sublayer. The figure above lists common ieee ethernet standards. In all cases, the primary purpose of the mac sublayer is to provide reliable data delivery over the inherently noisy and collisionprone wireless medium. The media access control mac data communication networks protocol sub layer, also known as the medium access control, is a sub layer of the data link layer specified in the sevenlayer osi model. The medium access layer was made necessary by systems that share a common communications medium. The mac sublayer is especially important in lans, nearly all of which use a multiaccess or broadcast channel as the basis of their networks.
Both of these two sublayers are responsible for different functions for the. Media access control mac is a sublayer of the data link layer dll in the sevenlayer osi network reference model. Mac address is used by media access control mac sublayer of datalink layer. This lower sublayer defines the media access processes performed by the hardware. Logical link control llc vs medium access control mac. The llc sublayer adds a header and a trailer to the data the data link layer uses llc to communicate with the upper layers of the protocol suite the llc sublayer is responsible for the placement and retrieval of frames on and off of the. An ethernet mac sublayer receives 42 bytes of data from the llc sublayer.
It responds to service requests from the network layer above it and issues service requests to the physical layer below it the data link layer is responsible for encoding bits into packets prior to transmission and then decoding the packets back into bits at the destination. Mac is responsible for the transmission of data packets to and from the networkinterface card, and to and from another remotely shared channel. The data link layer layer 2 of the osi model actually consists of two sublayers. The media access control layer is one of two sublayers that make up the data link layer of the osi model. It allows the upper layers to access the media and controls how data is placed and received on the media. It controls the transmission of data packets via remotely shared channels.
The two primary functions of the mac sublayer are to encapsulate the data from the upper layer protocols and to. Data link layer is divided into two sublayers, llc logical link control and mac media access. This is defined in the standard sevenlayer osi model as layer 2. The data link layer is divided into two sublayer by the 802 standards. The data link layer receives the stream of bits from the network layer divides into manageable data units called frames.
In layer 2 of a network, the media access control mac sublayer provides addressing and channel access control mechanisms that enable several terminals or network nodes to communicate in a network. A special sublayer of the data link layer, the medium. Functions of llc and mac sublayers of data link layer. Logical link control is implemented in software logical link control is specified in the ieee 802. The llc sublayer deals with addressing and multiplexing. Channel arbitration together with mac, line code, analog stuff etc is all physical layer. The data link layer is used for the encoding, decoding and logical organization of data bits. This layer takes the pdu which is packet of the network layer and encapsulates it with a header and trailer to be called a frame which is the pdu of the data link layer.
Data link layer does many tasks on behalf of upper layer. The data link layer functionality is usually split it into logical sub layers, the upper sublayer, termed as llc, that interacts with the network layer above and the lower sublayer, termed as mac, that interacts with the physical layer below, as. The medium access control mac, the sub layer of the data link layer deals with this problem. The first sublayer called logical link control llc sublayer and the second sublayer called media access control mac sublayer. The data link layer functionality is usually split it into logical sublayers, the upper sub layer, termed as llc, that interacts with the network layer above and the lower sub layer, termed as mac, that interacts with the physical layer below, as.
Mac features can be either standardsbased or proprietary. The modem features a packetbased physical layer and an alohabased data link layer. Within the data link layer, the llc provides flow control and. Network layer passes the data to the data link layer for transmission over the physical layer.
The channel allocation problem the mac medium access control sublayer is between the physical layer and the data link layer. Network topologies like ethernet exist at the data link layer. The mac layer is responsible for moving data packets to and from one network interface card nic to another across a shared channel see a breakdown of the seven osi layers in the quick reference section of webopedia the mac sublayer uses mac protocols to ensure that signals sent. Os hardening sec340 chapter 6, 7 flashcards quizlet.
One of the newly discovered algorithmsprotocols for allocating a multiple access channel is aloha. Ethernet relies on the two separate sublayers of the data link layer to operate. Datalink layer generally consists of two sublayers the upper of which is called logical link control llc sublayer and the lower, medium access control mac sublayer. The data link layer creates frames by adding the necessary checks and controls around the network layer data. The data link layer is divided into two sub layers, namely logical link control llc and media access control mac. To intermediate the communication between the media and the cpu, the datalink layer is divided into two sublayers. This topic provides an introduction to the mac sublayer of the data link layer layer 2.
Functions of data link layer in the osi model computer. Implements a trailer to detect transmission errors. Data link layer 2 physical layer 1 the data link layer is responsible for the exchange of frames between nodes over a physical network media. Datalink layer takes packets from network layer and encapsulates them into frames.
It provides data link layer addressing and delimiting of data according to the physical signaling requirements of the medium and the type of data link layer protocol in use. The driver software of computer nic and be considered as llc. It is responsible for flow control and multiplexing for transmission medium. Now looking into the sublayers of data link layer, i. The data link layer is layer 2 in the open systems interconnect osi model for a set of telecommunication protocols. Llc forms a frame from the network layer pdu into a format that conforms to the requirements of the network interface and media. In ieee 802 standard, data link layer is divided into two sublayers logical link controlllc sublayer. Broadcast networks have an additional issue in the data link layer. The llc sublayer software at the sending computer is responsible for transmitting the network layer protocol data unit pdu with. The data link layer is the protocol layer in a program that handles the moving of data in and out across a physical link in a network. Uint32 inserts the specified layer into the receivers list of sublayers at the specified index. The data link layer performs the main functions and is divided into two sub layers. This upper sublayer defines the software processes.
Mac address is word wide unique, since millions of network devices exists and we need to uniquely identify each. The tcpip network access layer is the equivalent of the osi. Specific functions of the data link layer include the following, framing. At the top, we have the logical link control llc layer, which is the one communicating with the cpu, while at the bottom we have the media access control mac layer, the one putting signals on the cable and reading them from it. The mac layer is a sublayer of the data link layer layer 2 in the osi reference model. Data packets are framed and addressed by this layer, which has two sublayers. Data link layer is divided into two sublayers, llc logical link control and mac media access control. Logical link control llc conceptually, the llc sublayer sits on top of the mac sublayer. This upper sublayer defines the software processes that provide services to the network layer protocols.