Local Area Network (LAN)
Local Area Network (LAN), a privately owned networks within a single building or campus-sized to several kilometers. LAN is often used to connect personal computers and workstations in a corporate office or factories to put together resources (resouce, such as printers) and exchange information.
LANs often use a single cable transmission technology. Traditional LANs operate at speeds ranging from 10 to 100 Mbps (mega bits / sec) with low delay (tens of micro-second) and has a small error factor. Modern LANs can operate at higher speeds, up to hundreds of megabits / sec.
 
 
Figure II.1 Two types of broadcast networks. (A) Bus. (B) Ring
There are several kinds of topologies that can be used on a LAN broadcast. Figure 1.1 illustrates two of the existing topologies. In the bus network (ie cable liner), at one time a machine acts as the master and is allowed to send packets. Other machinery necessary to refrain from sending any. So to prevent conflict, when two or more machines want to transmit simultaneously, the regulatory mechanism is required. Regulatory mechanism can be centralized or distributed form. IEEE 802.3 Ethernet is popularly called a bus broadcast network with decentralized controllers that operate at speeds of 10 to 100 Mbps. The computers on the Ethernet can send whenever they want, when two or more packets collide, each computer then just wait a random waiting time before shipment to repeat again.
Another broadcast system is the ring, on the topology of each bit is transmitted to the surrounding area without waiting for the complete package is received. Usually every bit around the ring in the time required to transmit a few bits, often before the complete package shipped. Like the other broadcast system, some rules have to be met simultaneously to control access to the ring. IEEE 802.5 (token ring) is a popular ring LAN that operates at speeds between 4 to 16 Mbps.
Based on the channel allocations, broadcast networks can be divided into two, namely static and dynamic. Type of static allocation can be divided based on discrete time intervals and the round robin algorithm, which allows each machine to perform a broadcast slot only when the time is acceptable. Static allocation is often a waste of channel capacity when a machine does not have to be done at LGI time slot allocations received. Therefore the system tends to allocate most of its channel dynamically (ie based on need).
Dynamic allocation method for a channel can be centralized or decentralized. In the centralized channel allocation method, there is a single entity, such as a bus controller unit, which determines who the next turn. Delivery of this package can be made upon receipt of a turn and make decisions related to an internal algorithm. In the decentralized channel aloksi method, there is no central entity, each machine must be able to determine themselves whether or not to send any.


reference: http://ilmu27.blogspot.com/2012/08/makalah-jaringan-komputer.html