2.4 access control controlled access methods2.4 access control controlled access methods

1. Communication
Networks
Access Control
in datalink layer
[Controlled Access Methods]

2. Overview of Module - 2
• Framing
• What is Framing
• Types of Framing
• Methods for identifying the
boundaries
• Flow Control
• What is flow control
• Types of flow control
• Access Control
• What is access control
• Types of access control
• Ethernet – IEEE 802.3
• Evolution of Ethernet
• Frame Format of Ethernet
• Access Control for Ethernet
• Performance Evaluation of Ethernet
• WLAN – IEEE 802.11
• Architecture
• Bluetooth
• WIFI
• Zigbee
• 6LowPan
• Network Layer Services
• IPv4
• Packet switching
• Network Layer Protocols
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3. Classification of Access Control Mechanism
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4. 2.A - Reservation
• This method is similar to the passenger reserving a seat in
bus or train to travel from one place to another
• In the reservation method, a station needs to make a reservation
before sending data. Time is divided into intervals. In each interval, a
reservation frame precedes the data frames sent in that interval.
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5. 2.B - Polling
This method is similar to MASTER – SLAVE concept. Server acts as
MASTER and Clients acts as SLAVE.
• Polling works with topologies in which
one device is designated as a primary
station and the other devices are
secondary stations.
• All data exchanges must be made through
the primary device.
• Select function and Poll functions are used
to send and receive frames.
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6. 2.C – Token Passing
• In the token-passing method, the stations in
a network are organized in a logical ring.
• In other words, for each station, there is a
predecessor and a successor.
• The current station is the one that is
accessing the channel now. The right to this
access has been passed from the predecessor
to the current station.
• The right will be passed to the successor
when the current station has no more data to
send.
This method is similar to passing a MIC among the audience attending the seminar.
The mic will be circulating among the audience continuously, if a person has to raise a
question, he should wait until the mic reached him. Once he finished asking questions,
he can pass on the mic to next person.
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7. Session Summary
• Controlled Access Methods [Following a systematic
approach]
• Reservation – Similar to Reserving the seats in Bus or
train
• Polling – Similar to Master Slave Concept
• Token Passing – Similar to passing a Mic among the
audience in seminar
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8. References:
• Behrouz A. Forouzan, ―Data communication and Networking, Fifth
Edition, Tata McGraw – Hill, 2013
• Larry L. Peterson, Bruce S. Davie, ―Computer Networks: A Systems
Approach, Fifth Edition, Morgan Kaufmann Publishers, 2011.
• Few online References (Will be Mentioned in the description Section)
Thank You…