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Hub, repeater, switch, router, gateway, bridge

HUB Hub is a controller that controls the traffic on the network.  The following important properties of hub are:  1) It amplify signals. 2) It propagates signals through the network. 3) It does not require filtering. 4) It does not require path determination for switching. 5) It is used as network concentration points. Hubs are basically two types: 1) Active hub 2) Passive hub Active hub: A ctive hub works as repeater which is a hardware device that regenerates the received bit pattern before sending them out . Passive hub : A passive hub is a simple hardware device which provide a simple physical connection between the attached devices. Advantages of hub: It cannot filter the traffic full stop feeling generally refers to a process or device that screens network traffic for certain characteristics such as source address and destination address and protocol. Disadvantages of hub: On a hub, more than one user may try to send data on the network at sam
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Scheduling: preemptive scheduling

Preemptive Scheduling : In contrast to non preemptive scheduling, a scheduling decision can be made even while the job is executing whereas in non preemptive scheduling, a scheduling decision is made only after job completes its execution. Therefor preemptive scheduling may force a job in execution to release the processor, so that the execution of some other job can be undertaken, in order to improve throughput considerably. Types of preemptive scheduling: 1) Round Robin scheduling algorithm : the round Robin scheduling is designed for time sharing systems. The primary objective of round Robin scheduling are interactive use, good response time and sharing the resources equitable among processes. It is similar to FCFS, but preemption is added to switch between processes. The processes are alocated a small unit of time. Known as time Quantum or time slice is in rotation until the completion of processes. To implement round Robin scheduling, a FIFO(first in first out) queue
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Scheduling: Non-Preemptive Scheduling

Scheduling : In multi-programmed computer, multiple processes competing for the CPU at the same time. This situation occurs whenever two or more processes are simultaneously in the ready state. If only one CPU is available. Then we need a system that decide which process run first and then next and this will be done by the scheduler. Scheduler : scheduler is an operating system module that she loves an axe top to be admitted into the system and then the next process to run. Scheduling is of two type: 1) Pre-emptive 2) Non pre-emptive Non Pre-emptive Scheduling : In batch non Pre-emptive scheduling implies that, once scheduled, selected job runs to completion. In other words, the running process not forced to relinquish ownership of the processor when a higher priority process becomes ready for execution. The scheduling techniques which use non preemptive scheduling are: 1) first come first serve (FCFS) scheduling 2) shortest job next (SJN) scheduling 3) dea
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