Data and communication

GECE 586 / ECE 493 – Computer Communication Networks 19/FA

Project #1: Throughput Evaluation of Link Layer Flow Control Date assigned: Tues., 10/8/19 Due date: Tues., 10/22/19 (2 weeks from the date assigned) Max points: 100 pts. Problem Statement: In the following diagram, link-layer frames are generated at node A and sent to node C through node B. In computer simulation implemented in OMNeT++, determine the average throughput of the overall link between nodes A and C for the situation described below:

 At node A, frames are constantly generated at a data rate of 100 kbps but transmitted

with probability Tx .P Any frames that are determined not to be transmitted are

discarded immediately but the next frame is generated at the given data rate, i.e., after the frame time.

 The propagation delay is 5 µs/km for both links.  There are full duplex links between the nodes.  All data frames are 1000 bits long; ACK frames are separate frames of negligible

length.  Between nodes A and B, a sliding window protocol with a window size of 7 is used.  Between nodes B and C, the stop-and-wait protocol is used.  Assume NO frame errors in both links.  There is an infinite-length buffer at node A and also at node B for the link direction of

A to B. No buffer is placed for the link direction of C to B as ACK frames are assumed to be transmitted immediately.

Simulation to be performed: 1. Assume that data rate at nodes B and C is 50 kbps. 2. Vary TxP from 0.1 to 1.0 with a step size of 0.1.

3. For each value of Tx ,P run simulation with a sufficient number of frames transmitted

to get good statistical averaging for the link throughput. 4. Complete the summary table (in the next page) and plot Throughput vs. Tx .P

5. Change the data rate at nodes B and C (from 50 kbps) to 150 kbps and repeat steps 2~4.

GECE 586 / ECE 493 – Computer Communication Networks 19/FA

Table 1. End-to-end throughput Transmission Probability TxP

End-to-end throughput

Data rate at B & C = 50 kbps Data rate at B & C = 150 kbps 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0

Items for submission: 1. A brief report containing the throughput table (above) and plot(s) as well as a

maximum ONE-page (not counting space for figures) narrative discussion of the results, and description of any additional assumptions you made in your simulation.

2. Source code of your OMNeT++ simulation that was used to generate the results. Make sure to put reasonable inline comments within your code so that one with reasonable knowledge can understand what is happening there when reading your code.

How to submit: Upload onto EvalTools a SINGLE ZIP file containing ALL items requested above. For the full credit, your OMNeT++ code must run when downloaded and executed.