In the ALOHA system, a node transmits whenever data is available to send.
A shared communication system like ALOHA requires a method of handling collisions that occur when two or more systems attempt to transmit on the channel at the same time. The original system used terrestrial radio broadcasting, but the system has been implemented in satellite communication systems. It was developed in the 1970s at the University of Hawaii. Media access control, including initiation of frame transmission and recovery from transmission failure.įollowing Protocols are used by Medium Access Layer :ĪLOHA : ALOHA is a system for coordinating and arbitrating access to a shared communication channel. The MAC sub-layer has two primary responsibilities:ĭata encapsulation, including frame assembly before transmission, and frame parsing/error detection during and after reception. In LAN nodes uses the same communication channel for transmission. Thanks to the LLC layer, it is possible to have at the same time, on the same network, multiple Layer 3 protocols. The header of a packet LLC indicates the type of layer 3 protocol in it: most of the time, it is IP protocol, but it could be another protocol, such as IPX ( Internet Packet Exchange) for example. All WiFi data packets so carry a pack LLC, which contains itself packets from the upper network layers. The LLC layer is standardized by the IEEE as the 802.2 since the beginning 1980 Its purpose is to allow level 3 network protocols (for eg IP) to be based on a single layer (the LLC layer) regardless underlying protocol used, including WiFi, Ethernet or Token Ring, for example. In fact, the IEEE divided this layer into two layers “above” is the control layer the logical connection (Logical Link Control, LLC) and “down” the control layer The medium access (MAC). The MAC layer is the “low” part of the second OSI layer, the layer of the “data link”. The medium access layer was made necessary by systems that share a common communications 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 seven-layer OSI model.
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