An organization usually uses LAN (Local Area Network) for the interconnection of computers and other equipments. Internal communication transmission capacity is greater in LAN compared to wide area network (WAN). LAN can be used for personal computers, backend networks, storage area networks and high speed office networks. The key elements of a LAN are topology, transmission medium, wiring access and medium access control. Topology indicates the nature of interconnection tool used for connecting end points. Commonly used topologies are bus, tree, ring and star. Transmission media which are employed here are twisted pair, baseband co-axial cable, broadband co-axial cable and optical fiber cable. LAN protocol architecture mainly consists of three layers- physical layer, medium access control layer (MAC) and logical link control layer (LLC). IEEE 802 is a reference model where physical layer performs the functions like encoding/decoding of signals, preamble generation/removal ( for synchronization) and bit transmission/reception. Medium access control layer (MAC) assembles data into a frame with address and error detection fields on transmission. On reception, it disassemble frame and performs address recognition and error detection. MAC also performs the duty of governing access to the LAN transmission medium. Logical link control layer (LLC) provides an interface to higher layers and performs flow and error control. MAC frame includes fields like MAC control, destination MAC address, source MAC address, LLC and CRC.
Subscribe to:
Post Comments (Atom)
No comments:
Post a Comment