Session 2 : The types of media access method (chapter 2)

The Media Access Method

The media access method determines whether or not a particular node can place data on the network at a given time.
Two categories of media access methods are:
-Contention-based or competitive media access
-Controlled or deterministic media access

The common media access methods are:
-Multiplexed Media Access
-Polling
-Token-Based Media Access
-Carrier Sense Multiple Access/ Collision Detection (CSMA/CD)
-Carrier Sense Multiple Access/ Collision Avoidance (CSMA/CA)
-Contention Domains

Multiplexed Media Access
Multiplexing is a controlled media access method in which a central device combines the signals from multiple nodes and transmits the combined signal across the medium.
The different methods of multiplexing are:
~Time-Division Multiplexing (TDM)
~Frequency-Division Multiplexing (FDM)
A central device called as multiplexer or mux is used to manage the multiplexing process.



Polling
Polling is a controlled media access method in which a central device contacts each node in turn to see whether it has data to transmit.
Demand priority is a polling technique in which nodes signal their state—either ready to transmit or idle—to a hub.




Let's  continued to next part, session 2,Chapter 2....