"Distance Learning and Networking Technologies"

Assistant Prof. Dr.-Stelios Savaidis

Department of Electronics,

TEI Piraeus, Greece

Email: ssavaid@teipir.gr

Tel:+30 210 5381181

Distance Learning and Network Performance

Distance Learning relies on the existing network infrastructure PSTN/ISDN, LANs/WLANs, MANs/WMANs, WANs.

Network Performance Issues can severely restrict the efficiency of Distance Learning Applications QoS issues e.g. throughput, delay etc.

Network Resource Requirements vary depending on the type of the Distance Learning Applications HTTP (best effort), FTP (Variable Rate), Video Streaming (Real Time

Variable Rate) etc.

Distance Learning and Network Performance

A global approach of Distance Learning should take into account Network Performance Issues Degraded Network Performance results to a low QoS from user’s point of

view e.g. slow response to user’s actions.

An Accurate Network Performance Analysis Provides Proper Network Dimensioning Decisions that ensure Distance Learning Efficiency at a minimum technical and/or economical cost.

Prediction of Network Performance is a rather complicated task but can be carried out, even for complicated networks, with Network Simulation Software Packages

OPNET Network Simulator

OPNET is a powerful event based Network simulator Produces numerous random traffic events and collects network performance

measurements.

OPNET Simulations of both Commercial and Generic Network nodes are available. Several industrial telecommunication nodes (routers, switches, modems from Cisco,

3 Com etc) are included in OPNET’s library. Several generic telecommunication nodes can be configured offering customized

solutions.

OPNET Simulations of Typical Network Links are available ISDN, ADSL, E1/T1, Ethernet, SDH etc.

Different Types of Applications are available and can be configured accordingly HTTP, FTP, Mail, Voice etc.

Stochastic Models can be used in order to simulate user’s behavior in terms of traffic generation Uniform, Exponential, Poisson etc.

Distance Learning Study Case

Study Case Input Data

Web based Distance Learning Environment.

Users from a complex

of 6 high schools.

HTTP and FTP are the typically supported applications.

5th Technical School 4th Technical School

3nd Technical School

2nd Technical School

1st Technical School

AdministratoreLearning Web Server

High School

The Internet

Distance Learning Study Case

Possible Output Data

Maximum number of users for a given network infra-structure.

Possible Network Upgra-

des for a given network infrastructure e.g.

what kind of LAN what type of DSL to/from

each school. what kind of fractional E1

line to/from the Web Server.

What kind of Web Server5th Technical School 4th Technical School

3nd Technical School

2nd Technical School

1st Technical School

AdministratoreLearning Web Server

High School

The Internet

OPNET Simulation of the Distance Learning Study Case

An Ethernet LAN repre-sents each school

The number of users is variable

FTP/HTTP traffic is genera-ted randomly.

FTP file and HTTP page attributes are also random

Different types of ADSL link can be used i.e. with different upload/download rates

Fractional E1 can be used to/from Web Server

Profile Configuration

Application Configuration

FTP Configuration

HTTP Configuration

HTTP Page Properties

Web Server Configuration

Web Services

Access to/from Web Server over a 2 Mbps E1 line

FTP and HTTP Services suported

Access to/from User’s Site

User’s Profile

Network Performance Results: Response Time

(ADSL 384/128)FTP Response Time (sec) HTTP Page Response Time (sec)

Reasonable Performance ???

(ADSL 512/128 Kbps) FTP Response Time - HTTP Page Response Time

Network Performance Results: Response Time

Reasonable Performance ???

(ADSL 1,024/256 Kbps)FTP Response Time – HTTP Page Rasponse Time

Network Performance Results: Response Time

Reasonable Performance ???

Network Performance Results: Throughput at User’s Site

ADSL 384/128 Kbps Throughput

ADSL 512/128 Kbps Throughput (bits/sec)

Network Performance Results: Throughput at User’s Site

ADSL 1,024/256 Kbps Throughput (bits/sec)

Network Performance Results: Throughput at User’s Site

ADSL 384/256 Kbps Utilization

Network Performance Results: Utilization at User’s Site

ADSL 512/128 Kbps Utilization

Network Performance Results: Utilization at User’s Site

Network Performance Results: Utilization at User’s Site

ADSL 1024/128 Kbps Utilization

E1 2,048/2,048 Kbps Throughput (eLearning Server to IP Cloud Communication Link)

Network Performance Results: Web Server Throughput

E1 2,048/2,048 Kbps Utilization (eLearning Server to IP Cloud Communication Link)

Network Performance Results: Web Server Utilization

Network Performance Results: Study Case Overview

Obviously, ADSL with higher data rates increase the number of eLearning users.

QoS measurements (e.g. FTP Response Time and HTTP Response Time) must be counted in order to evaluate network resources vs number of users.

Considering HTTP Response Time as the QoS threshold we may conclude to the following statements 384/128 Kbps ADSL line can offers an acceptable QoS for 30 users. 512/128 Kbps ADSL Line increase the number of users to 40 (in

terms of QoS). 1024/256 ADSL line can offer acceptable QoS to less then 50 and

more than 40 users.Web Server E1 link, seems to be an unreasonable choice. A

fractional E1, which is much more affordable for the schools’ budget, should be used.

"Distance Learning and Networking Technologies"

Thank you for your attention !!!