"distance learning and networking technologies" assistant prof. dr.-stelios savaidis...
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"Distance Learning and Networking Technologies"
Assistant Prof. Dr.-Stelios Savaidis
Department of Electronics,
TEI Piraeus, Greece
Email: [email protected]
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
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 ???
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.