讲解course project、辅导python, C/C++程序语言、讲解Packet Re-ordering

Regarding the course project, I prefer that you could come out of some project topics that

you feel are interesting and suitable for simulation study. The simulation project could be

in any application domain, such as simulation of hospital emergency, simulation of

service requests to data centers, simulation of the charging/discharging of electrical

vehicles, simulation of vehicle traffic in a city, and so on. Please send me your proposed

topic, if any, by Nov. 5.

If you do not have anything in mind, the following is a project topic that you can work

on.

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Project: Priority Queueing to Alleviate Packet Re-ordering Problem

Background: In the Internet, data packets from a source node (e.g., a web server) to a

destination (e.g., a client computer) may experience different delay, resulting in out-oforder

packet arrivals at the destination. A common solution is to buffer out-of-order

packets at the destination and re-order the packets into correct order before sending them

to the application layer. This project is to investigate the benefit of using priority

queueing in the intermediate routers to alleviate the packet re-ordering problem.

Simulation Setup: We assume that the network includes a source node, a router, and a

destination. Data packets are transmitted from the source to the router and then to the

destination. The source node generates Poisson traffic, with average rate of 20 packets

per second. The transmission speed of the source node is 10 Mbps. Each packet has a

unique sequence number and all data packets have the fixed length of 1000 Bytes (1 Byte

= 8 bits). From the source to the router, packets experience a random delay which follows

a normal distribution with the mean of x seconds and the standard deviation of y seconds.

From the router to the destination, packets experience a fixed delay of 50 ms.

The router has two queues, one having a higher priority than the other. It also keeps track

the largest sequence number it has seen so far, called currentSeq. If the sequence number

of the incoming packet is larger than currentSeq, we call the incoming packet an in-order

packet and update the currentSeq as the same as the sequence number of the incoming

packet. Otherwise, the incoming packet is considered out-of-order. When a packet

arrives, if the router is idle, the router transmits the packet immediately. Otherwise, the

packet will be put into the low priority queue if it is an in-order packet and will be put

into the high priority queue if it is an out-of-order packet. We assume non-preemptive

scheduling (i.e., when the router starts transmission a lower-priority packet, the

transmission cannot be interrupted even if a higher-priority packet arrivals.) and work

conserving (i.e., the router cannot be idle if there are packets waiting in the queues).

Nevertheless, when the router finishes transmission of a packet, it always serves the high

priority queue first if there are packets in that queue. The transmission speed of the router

is 15 Mbps.

Set the sizes of both queues in the router as 10M Bytes. When an incoming packet finds

its corresponding queue is full, the incoming packet will be dropped.

Requirement: Simulate the above Priority Queueing model. You can re-use and modify

the sample code provided in Assignment 1. The following performance metrics should be

evaluated:

(a) Packet out-of-order rate: It is defined as the ratio of the total number of out-of-order

packets over the total number of packets.

(b) Average packet delay: It is defined as sum of the end-to-end delay of all packets

divided by the total number of packets.

(c) Average packet loss rate: It is defined as the ratio of total number of packets dropped

by the router over the total number of packets.

(d) Compare the results if the router is modelled as a single FIFO queue, single server

system. What is your conclusion?

Quick Guideline for Running Simulation

Make sure you run the simulations long enough producing enough data

Run the simulations with different combinations of x and y values.

For each combination (scenario), run the simulations with at least five different

seeds

For each run, collect the stats (e.g., the packet out-of-order rate and average

packet delay if your project is to study the benefit of using priority Queueing to

solve packet re-ordering problem)

? Compute confidence intervals for each of the metrics, with confidence level set

as 95%.

Quick Guideline for Writing Report

Write the report in the following format:

–Brief problem (Project) Description

–The simulation model (e.g., the problem mapping to an equivalent priority

queueing model)

–Simulation goals and Simulation parameters

–Methodology:

How is your simulation built? (e.g., why is your simulator valid for the

simulation model?)

How did you setup the simulations?

How did you collect the stats?

–Analysis

For each run, report the collected statistics

For each scenario, find the average stats across five different runs using

different initial seeds

–Conclusion: What conclusion can be drawn from your simulation study with

respect to the problem under investigation?