Access control methods are required in a network to ensure that only one user of the network is able to transmit at any one time.
In ring-based local area networks (LANs), two commonly employed techniques are:
Contents
In this technique, a token i.e. a special bit pattern, is circulated. When a station wishes to transmit, it waits until it receives the token, and then transmits the data with the token attached to its end. Another station that wishes to transmit removes the token from the package of data and transmits its own data with the token attached to its end.
This technique involves empty slots being circulated. When a station wishes to transmit data it deposits it in the first empty slot that comes along.
In bus or tree networks a technique that is frequently employed is:
With CSMA/CD technique, stations have to listen for other transmissions before transmitting, with any station being able to gain control of the network and transmit, hence the term multiple access. If no activity is detected then transmission can occur. If there is an activity, then the system has to wait until it can detect no further activity. Even with this listening before transmitting, it is still possible for two or more systems to start to transmit at the same time. If such a condition is detected, both stations cease submitting and wait a random time before attempting to transmit again. This method is commonly associated with Ethernet LAN bus.
Related: Topological Network Structures used in Fieldbus Systems
Recommended: The Ultimate Guide to Electrical Maintenance
Image: Pexels The electric vehicle (EV) market is accelerating at an unprecedented pace, driven by…
Numerical control is a form of digital control that is employed on machine tools such…
Photo: Pexels Benefits of Installing Solar Panels in Your Home: Save Money and Your Planet…
Pneumatic control valve Control valve sizing refers to the procedure determining the correct size of…
The aim of a typical control system is to force a given set of process…
An object can be used to activate a switch directly, producing an ON or OFF…