"Distance Learning and Networking Technologies" Assistant Prof. Dr.-Stelios Savaidis Department of Electronics, TEI Piraeus, Greece Tel:

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.

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 Server

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

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 !!!