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ACCESS METHOD - Coggle Diagram
ACCESS METHOD
RANDOM ACCESS
Each station has right to medium without being controlled by any other station
Each station can transmit when it desires
METHOD
Carrier Sense Multiple Access
(CSMA)
developed because-minimize the chance of collision -Increase the performance
reduced the possibility of collision but
cannot eliminate it
method
Nonpersistent
line is idle, the station send immediately. If not, the station waits a random period of time and sense the line again
1-Persistent
station find the idle line, the station send it frame immediately
p-Persistent
station finds the line idle, the station may or may not send
Multiple Access
(MA)
Carrier Sense Multiple Access/Collision Detection (CSMA/CD)
Carrier Sense Multiple Access/Collision Avoidance (CSMA/CA)
CONTROLLED ACCESS PROTOCOL
DEFINITION
stations consult one another to find which station has the right to send A station cannot send unless it has been authorized by other stations
3 METHOD
Reservation
Polling
designated as a primary station and other secondary
primary device control the link, secondary follow
instructions
If primary want to receive data, it asks the secondaries if they have anything to send >> polling
If primary want to send data, it tell secondary target to ready receive >> selecting
Token passing
organized in a logical ring
Each station has a predecessor and a successor
Predecessor is the station which is logically before
the station in the ring
Successor is the station which is after the station in
the ring
The current station is the one that is accessing the
channel now
station is authorized to send data when it receives a special frame called token
Token management is needed because
Stations must be limited in the time they can have
possession of the token
The token must be monitored to ensure it has not been
lost or destroyed
To assign priorities to the stations and to the types of
data being transmitted
To make low-priority stations release the token to
high-priority stations
Logical Ring
stations do not have to be physically connected in a ring, the ring can be a logical one
Four different physical topologies that can create a
logical ring:
Physical ring topology
Dual ring topology
Bus ring topology
Star ring topology
INTRODUCTION
multiple-access method that using multiple-access protocol is needed to coordinate access to the link
