This document discusses access control methods in data link layer communication networks. It describes reservation, polling, and token passing as the three main types of access control. Reservation requires stations to reserve time intervals before transmitting data. Polling uses a primary station that polls secondary stations for data exchanges. Token passing organizes stations in a logical ring, passing a token from one station to the next to determine which has access to transmit.

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…