Page 138 - DCAP406_DCAP_207_Computer Networks

Unit 8: Data Link Protocols

Selective Repeat is an improvement on Go Back N protocol and tries for more efficient use Notes
of bandwidth by reducing the number of retransmissions because it retransmits only one
frame instead of the entire series. Thus, Selective Repeat is considered a better choice.
Finite State Machine model is a technique to verify the correctness of the protocol. PPP and
HDLC are widely used data link protocols.

Wireless technology has helped to simplify networking by enabling multiple computer
users to simultaneously share resources in a home or business without additional or
intrusive wiring. These resources might include a broadband Internet connection, network
printers, data files, and even streaming audio and video. This kind of resource sharing has
become more prevalent as computer users have changed their habits from using single,
stand-alone computers to working on networks with multiple computers, each with
potentially different operating systems and varying peripheral hardware.

Bluetooth is a proprietary open wireless technology standard for exchanging data over
short distances (using short wavelength radio transmissions in the ISM band from 2400-
2480 MHz) from fixed and mobile devices, creating personal area networks (PANs) with
high levels of security.

8.11 Keywords

Bluetooth: Bluetooth is a proprietary open wireless technology standard for exchanging data
over short distances (using short wavelength radio transmissions in the ISM band from 2400-
2480 MHz) from fixed and mobile devices, creating personal area networks (PANs) with high
levels of security
Point-to-Point Protocol (PPP): It is a data link layer protocol and operates over a point-to-
point link that connects two communicating link-level peers at each end of the link.
Positive Acknowledgement with Retransmission Protocol (PAR): The protocol is able to handle
congestion, lost frames and damaged frames because frames are retransmitted until a positive
acknowledgement is received.
Protocol Verification: Protocols are verified either during the design phase before
implementation of the system or during the testing and simulation phase after implementation
of the system.
Selective Repeat: Provides buffers at source and destination hosts to enable the source node to
have more than one outstanding frame at a time and destination node to accept out of order
frames and store them in its window.
Simplex Stop and Wait: After transmission, the source node waits for an acknowledgement
from the destination node. After receiving, the acknowledgement, the loop starts over again.

8.12 Review Questions

1. What is the data link protocol?
2. What advantages does Selective Repeat sliding window protocol offer over Go Back N
protocol?
3. What is the purpose of flow control?
4. Describe how does finite state machine model carry out protocol verification.

5. What are different data link protocols available? Why does PPP have become popular?
6. How does the data link layer accomplish the transmission of data from the source network
layer to the destination network layer?

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