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Can you predict which 1 is best linux Os

10:25:00 PM vikas 0 Comments Category : Computer World

Media Access Control Sub Layer

8:58:00 PM vikas 0 Comments Category : Computer World

Media Access Control Sub Layer

Round Robin Techniques

In Round Robin techniques, each and every node is given the chance to send or transmit by rotation. When a node gets its turn to send, it may either decline to send, if it has no data or may send if it has got data to send. After getting the opportunity to send, it must relinquish its turn after some maximum period of time. The right to send then passes to the next node based on a predetermined logical sequence. The right to send may be controlled in a centralized or distributed manner. Polling is an example of centralized control and token passing is an example of distributed control as discussed below.

Polling

The mechanism of polling is similar to the roll-call performed in a classroom. Just like the teacher, a controller sends a message to each node in turn. The message contains the address of the node being selected for granting access. Although all nodes receive the message, only the addressed node responds and then it sends data, if any. If there is no data, usually a “poll reject” message is sent back. In this way, each node is interrogated in a round-robin fashion, one after the other, for granting access to the medium. The first node is again polled when the controller finishes with the remaining codes.

The polling scheme has the flexibility of either giving equal access to all the nodes, or some nodes may be given higher priority than others. In other words, priority of access can be easily implemented.

Figure

Polling can be done using a central controller, which may use a frequency band to send outbound messages as shown in Fig. 5.2.2. Other stations share a different frequency to send inbound messages. The technique is called frequency-division duplex approach (FDD). Main drawbacks of the polling scheme are high overhead of the polling messages and high dependence on the reliability of the controller.

Polling can also be accomplished without a central controller. Here, all stations receive signals from other stations as shown in Fig. 5.2.3. Stations develop a polling order list, using some protocol.

TECH KNOW STUDY

Can you predict which 1 is best linux Os

Media Access Control Sub Layer

Media Access Control Sub Layer

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