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Classification of MAC Protocols
In ISO OSI layers there are seven layers, and each layer has its characteristics and its protocols. The most important second layer from the bottom is the data link layer. In this data link layer consists of two different layers and MAC is one important layer. MAC is the Medium Access Control layer. MAC layer helps to reduce the collision while transmitting the data. The main functionality of the MAC layer will act as a medium to access the shared resources in the network. So it has the control accessibility of nodes when they are in a shared medium.
MAC (Medium Access Control) Layer
MAC layers are above the physical layer, it transmits the frames over the medium and transmits the data by resolving if any issues occur regarding the source and destination address. It will specify the channel through which the frames will travel or access the resources, it supports more than one frame at a time. Collision-free transmission has happened here when in any situation collision occurs then it will retransmit the frame again to the destination. It also prevents transmission errors while transmitting the data and for every frame, it checks for the sequence to maintain the correct sequent order so that the users will receive the correct information. It will transfer frames over NIC. The reachability of remote channels which are sharable is restricted. It also assures the flow control mechanism.
Classification of MAC Protocols
The MAC protocols specify the influence of different protocols on nodes to access the remote channels.
MAC protocols have been divided into 4 types −
Contention-based MAC protocol
Channel polling-based MAC protocol
Scheduling-based MAC protocol
Hybrid MAC protocol
The description of four types of MAC protocols is listed below −
1. Contention-based MAC Protocol
It is used for accessibility purposes. To transmit the data from one node to another node, before initiation it will check for the nearest nodes and their positions and also examine the carrier status. The accessibility of the channel is specified by the carrier status. If the value is ideal, then it can start the transmission of data. If it is not then the node has to wait for a while. This mechanism will reduce the collision and simultaneous accessing of resources. It is flexible even the network grows or shrinks. There is no guarantee of transmission of data and it is solely dependent on the sender. Under contention-based, there are sender-based and receiver-based sender-based transmissions that can start by the sender. The receiver initiates the Connection.
2. Channel polling-based MAC Protocol
Under channel polling-based MAC protocol, there is the keyword “preamble sampling”. Like the above before transmission, the sender will check for the receiver’s availability by sending a preamble. A preamble is a byte that is added with the data packet prefix value. It will help the sender to activate the receiver when it is in sleep mode. If the receiver is active then it will take the packet otherwise this preamble will be in sleep mode. The receiver is in sleep mode until no more activation signals are sent by the sender. This happens on an interval basis. For this scheduling is not needed. All nodes are synchronized. This channel polling is also represented as LPL in BMAC protocol.
3. Scheduling-Based MAC Protocol
In scheduling-based protocol, there will be a schedule followed by the nodes while transmitting the data, all nodes must follow certain time slots. As it is scheduled one packet will transfer as per the schedule only so there is no collision occurs while transmitting the data. Nodes don’t check for the availability or status of other nodes because they have their time slots. So before going to access the channel first they should get the timeslot. It has advantages like reduction of collision, and avoiding the checking of the status of the receiver randomly. It is also associated with the drawbacks like traffic, less throughput, reduce scalability, etc… as it follows a scheduling mechanism there is a guarantee of packet reachability while transmitting the data.
4. Hybrid MAC protocol
It is the combination of MAC Protocols. It supports both synchronous and asynchronous. As it is the combination of MAC protocols under this it has the advantage of remaining protocols. It will be like a new approach as it includes more than one MAC protocol. An example of a hybrid MAC protocol is Z-MAC i.e; Zebra MAC.
Conclusion
While transmitting data over remote channels security is the key element. The transmission should be collision-free then only the packet will reach the destination safely. The MAC layer protocol which is associated with the data link layer will provide the accessibility of the resources over remote channels with an assurance of data flow, and collision-free transmission and also provides security.
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