THE GREEK SCHOOL NETWORK

Structure, Design Principles and Services Offered

Nikolaos Xypolitos, Michael Paraskevas, Emmanouel Varvarigos

Research Academic Computer Technology Institute, University of Patras, Greece

Keywords: Internet services, School Networks.

Abstract: The Greek School Network (GSN) is a closed educational network that offers advanced telematic and

networking services to all units of primary and secondary education schools and administration offices in

Greece. The main objective of GSN is the implementation of a network infrastructure for the

interconnection of the school laboratories and the provision of a wide range of network and telematic

services to students and teachers. The GSN separates its telematic services to two major groups: the

centralized services and the end-user services. The purpose of this paper is to describe the GSN structure,

the services it provides, and its design and operational principles.

1 INTRODUCTION: THE GREEK

SCHOOL NETWORK

The Greek School Network – GSN (Greek School

Network, 1998), described in this report, is the

educational intranet of the Ministry of Education and

Religious Affairs, which interlinks all Greek schools

and educational administration offices, and provides

basic and advanced telematic services to students,

teachers, and administration personnel. It also

contributes to the creation of new educational

communities that use Informatics and

Communication Technologies in the educational

procedure. The telematic services of the GSN are

based on Open Source technologies that are

modified in their source to fit exactly the needs of

the Greek educational community.

The GSN offers a large number of services to

more than 15.000 schools and administrative units,

and over 50.000 teachers in Greece, across all the 51

prefectures of Greece. The services are offered

over the network that GSN has developed and

maintained since 1998. The network is hierarchically

structured into three layers in order to manage the

complexity that comes with the large number of sites

that are covered:

• Core Network: The Greek Schools

Network interconnects with the Greek

Research and Technology Network

(GRNET, 1995) in seven main points,

using it as its core network.

• Distribution Network: The distribution

network provides for the interconnection of

the schools and educational administrative

units to the core network, and consists of 51

nodes. The GSN has installed in the capital

of each prefecture, network and

computational equipment, to ensure optimal

access of the prefecture‘s schools to the

network and its services, and is further

separated into two distinct layers:

• Access network: It is used to directly and

efficiently interconnect the schools to the

prefecture‘s access point. The

telecommunication junctions used to

interconnect each school are selected on the

basis of financial and technical criteria from

an array of available options: Digital ISDN

circuit (bandwidth: 64 - 128 kbps), Analog

leased line (0,128 – 2 Mbps), Wireless link

(10 Mbps), ADSL circuit (384/128 Kbps,

512/128 Kbps, 1024/256 Kbps), VDSL

circuit (10 - 15 Mbps), Public Switched

Telephone Network circuit (56 kbps)

In order to achieve the objectives of e-Europe

2005 regarding the provision of broadband access to

all schools, the Greek Schools Network is upgrading

its distribution network by increasing its installation

283

Xypolitos N., Paraskevas M. and Varvarigos E. (2006).

THE GREEK SCHOOL NETWORK - Structure, Design Principles and Services Offered.

In Proceedings of the International Conference on e-Business, pages 283-288

DOI: 10.5220/0001425302830288

 SciTePress

of broadband connections (ADSL connections and

10 Mbps wireless links). Regarding the wireless

links, 13 distinct wireless networks are in operation.

The wireless networks allow for the provision of

advanced, high-quality telecommunication and

informatics services to the units connected, and

significantly decreases the telecommunication

operational costs.

2 THE GSN CENTRALIZED

SERVICES

The Greek Schools Network offers a broad package

of services to its units and users that can be

separated into two main categories: the centralized

services and the end-user services. The centralized

services are supporting many of the end-user

services and also offer GSN administrators the

ability to globally monitor the correct operation of

the services. The GSN’s centralized services are the

Directory Service, the Content Filtering service

which controls the access to the Internet, prohibiting

access to web sites with harmful content for

children, and the Web Hosting for static and

dynamic pages

2.1 The LDAP Directory Service

The main centralized service of the GSN network is

the LDAP directory service. The LDAP directory

holds all the teacher and school accounts and is used

to authenticate the users in all services that require a

have been adjusted for every user in order to suit the

needs of the services offered. The directory service

is supported by an array of four servers, three of

which are exclusively dedicated to supporting the

directory service. The main server is the write

master, where all additions and updates to the

directory information store take place. The

remaining servers store a copy of this information,

which is continually synchronized with the main

server (online replicas). The online replicas

constantly answer to queries of other services

supporting the delivery of email messages, the

dialup access to the network, and the

authentication/authorization operations for the other

services. It is worth noting that in addition to the

typical multimaster replication model, alternative

servers may assume the role of the main write

master, allowing for the smooth and continuous

operation of the directory in case of malfunctioning

of the write master server.

2.2 Controlled Access to the Internet

The GSN has restrictive policies for the sites that

can be accessed by the students. A schema with the

appropriate proxy servers is used to control the

access of GSN users to the Internet. The access is

prohibited to categories like porn, drugs, violence,

gambling etc. There are three ways for the GSN

system to control the access of its users to the

Internet. The first is to examine for words that

identify an illegal category in the URL or in the

metadata of every requested site. The second way is

to communicate with international black list

databases and deny access to the sites listed in these

databases. The third way to control the access to the

Internet is more customized to the GSN needs. The

GSN has built an extra database to explicitly record

sites not allowed to be accessed and sites allowed to

be accessed. The first database helps restrict access

to sites that are not globally black listed but whose

content is not consistent with the GSN terms of use.

A user has the right to suggest a site that must be

blacklisted, and the administrator of the service

examines the site and includes it in the custom black

list database, if its content is found to be ineligible.

A similar database is used to record sites whose

content is not offensive, but which have been

blacklisted for some reason. A user may suggest, by

sending an e-mail to the administrator of the service,

a site that is currently prohibited to become

accessible. The administrator then examines the

content of the site, and if it is found to be

appropriate records it in the while list database so

that GSN users can access it.

2.3 Web Hosting

The Web Hosting service provides space for web

pages and web applications using the GSN Web

servers. The service is provided to the schools and

teachers community to create their own web sites.

The web sites are separated to schools’ web sites and

administration units and teachers’ web sites

Each school or administration unit connected to the

GSN has its own Domain Name (DNS) under the

sch.gr domain. This DNS is the address of a virtual

web hosting server for this unit. If a unit has more

than one accounts, each of them has an independent

web site accessible under the address <unit DNS

>/xxxx.

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The service allows the users to publish static

HTML pages or dynamic pages using PHP and

MySQL. The GSN offers to its users a web based

database administration interface accessible under

the Web Portal. Each school or administration unit is

allowed 100 MB of web space, and each individual

teacher is allowed 50 MB of web space. The GSN

offers four different tools for building web pages.

Two of them focus on building static web pages and

the other two tools focus on building dynamic web

pages. The tools were all developed by the GSN

team and they can be accessed by registered users

through the web portal. In addition to the web page

building tools, GSN users have FTP access to their

web space, so that they can simply upload a site they

have already built elsewhere.

The schools and teachers sites are shown in the

web portal in a special area dedicated to the users’

sites. The sites are grouped according to their

thematic area in a thematic catalogue that is

available to the visitors of the web portal. A rating

mechanism is also available, and the sites with the

highest rates are shown in the first page of the web

portal. Through the web portal, users can add web

sites to their favourite preferences, which are shown

in a special area of the portal. The portal also

provides a search mechanism for the teacher and

school web sites through a graphical interface (a

map of Greece), allowing searches by author, name,

and geographical area.

3 THE GSN END-USER SERVICE

The end-user services offered by GSN are:

• Web Portal (Greek School Network, 1998),

offering news services and personalized

access to all GSN telecommunication and

informatics services under a single login

method.

• Ε-mail, accessible through the POP3 and

IMAP protocols, as well as the world wide

web and E-mail lists

• News service, forum discussions and

electronic magazine

• Wizards for automatic webpage creation

• Asynchronous distance learning, for

hosting and distributing digitized courses

• High end multimedia services such as

Teleconference, Video On Demand for

delivering streaming educational

multimedia material and Live Web Casting

of various educational events

• Automated registration procedure for

educational staff and students

• Remote network access (dialup)

All the end user telematic services are implemented

in the GSN Web Portal.

3.1 The Web Portal

The framework used for the implementation of the

GSN Web Portal has been mainly based on the

Jetspeed Portal of the Apache Software Foundation.

The framework used offers a programming

context oriented towards the implementation of web

portals that have a large number of users. At this

moment, Jetspeed is actively being developed and its

feature set is constantly being expanded. The GSN

developing team is further expanding the

functionality of the framework engine to develop a

portal environment that suits the needs of the GSN

users.

The Web Portal Design adheres to the following

general specifications:

• The portal permits the execution of micro-

applications that are integrated in it as

portlets. This specification allows for the

natural separation of the application and the

presentation layer, by offering virtually

unlimited potential regarding the

presentation location and format of the

output of each portlet. The output of all

portlets is well defined on the basis of

XML/DTD schemas.

• A number of services are currently being

implemented as Web Services. This will

dramatically increase the re-utilization of

these services as well as their distribution to

the end users. Public access may be offered

to Web Services (through UDDI) separately

from the web portal; for instance such

services may be incorporated in the users’

pages (e.g. services that deliver maps based

on the G.I.S.).

• The usage of Jetspeed as the underlying

framework offers clear advantages, since

issues related to security, user

authentication and authorization, content

display mechanisms in a customized

THE GREEK SCHOOL NETWORK - Structure, Design Principles, and Services Offered

285

environment, separation from the portlet

implementation programming language,

velocity engine template support for

content display and integration with other

Open Source applications have already

been solved.

The GSN has developed further the Open Source

portal to support LDAP authentication over secure

password encryption (encrypted with the Unix

Encryption algorithm according to the SUN ONE

LDAP Server), to support personalized pages for

every registered user and to make the login

procedure easier by keeping the navigation of an

anonymous user when he/she decides to login to the

portal. Furthermore, the appropriate modules have

been created so that all the available portlets of the

Jetspeed portal can support LDAP authentication. A

single sign-on system has been implemented which

allows all GSN members to use all services

requiring login after they have logged-in once in the

GSN web portal. The web portal has more than

50.000 users who have their own customized views

of the web portal.

To support a higher number of concurrent users

we have implemented a load balancing technique.

The Apache httpd server (Apache Server Project,

1996) is the main web server in use, combined with

at least one application server, which offers the

execution environment for Servlets and JSP pages.

The Apache web server handles all incoming

requests, forwarding them to the application servers

using the mod_jk module. Each application server

hosts an identical version of the Web Portal.

3.2 E-mail and E-mail Lists

This service is used by the Greek educational

community and by the Vocational Training

personnel. The accounts for the service are separated

in the following user groups: a) Accounts for

Schools and Administrative units, b) Accounts for

Teachers, c) Accounts for Students.

The service has all the standard characteristics of

an e-mail service, plus some additional

characteristics we have developed in order to

provide a more flexible and secure service to the

educational community. The extra features provided

include, virus protection using the Sophos antivirus

software that is installed in all GSN mail servers and

spam protection with new anti-spamming filters.

Spam protection is activated only upon user

request (through a corresponding checkbox in the

web portal), and when it is activated a new folder,

named “spam”, appears in the users mailbox. When

a message is tagged as “spam” (in the GSN mail

server, when the message has been sent more than a

predefined number of times and the sender does not

have the right to send multiple messages), it is

automatically placed in the spam folder. The user

may also choose to categorize as spam all the e-

mails arriving from known spam sources that are in

GSN's rbl lists.

The mailing list service enables the development

and maintenance of mailing lists that can be used to

deliver a large number of messages to large numbers

of GSN users. There are two main categories of

mailing lists currently active in GSN: lists with

dynamic subscription of members, and lists with

static subscription of members. In the lists that allow

dynamic subscription, the members are coming from

the LDAP directory Server of the GSN. The list mail

address may, for example, look like dim@sch.gr,

where the above list may identify all the first grade

schools of Greece. In the lists with static

subscription, the list administrator can enlist one or

more users, or the users themselves can become

members of the lists of their choice, by filling in

their e-mail and some personal data in the

appropriate web form.

To prevent the members of the lists from

accessing material that is inconsistent with the GSN

is responsible for the material that is distributed

through the lists. Some lists are completely open, but

these are a minority. The use of a moderator is

mandatory in most cases, because the educational

community is a very special community of people

and messages that contain spam, viruses,

pornography and other related content must not be

allowed in the users’ mailboxes.

3.3 News Service, Forum

Discussions and Electronic

Magazine

The news service allows registered users, such as

schools and teachers, to post announcements. The

announcements are hierarchically grouped, based on

their content to different categories and topics. Each

announcement has a certain scope: it may apply to

the users of a specific educational unit, a prefecture,

the group of all registered units, etc. The GSN portal

also offers to its members a forum discussion board

which allows the users to create new posts, reply to

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messages in a particular post and create new

discussions.

The electronic magazine of GSN is a classic

newsletter service used to inform GSN users of

educational news and new services introduced. The

service was built from scratch, and gives the

opportunity in all schools to construct their own

newsletter. An archive system keeps all the versions

of the newsletter and every newsletter can be

accessed as a web page through the GSN portal.

3.4 Asynchronous Distance

Learning

The software used for this service is Moodle

(Moodle, 2002), which is a software package for the

production of online courses and web pages,

offering a complete set of internet education

services. GSN users can subscribe to an available

course and also, following a particular procedure,

become trainers in a course. The e-learning service

is accessed through the GSN web portal. The e-

learning environment is fully translated into Greek

together with all the modules of the platform, and a

great deal of content has already been developed and

organized in various thematic areas.

3.5 Teleconference Service

The teleconference service of GSN enables a

conference between two or more participants located

at different sites by using the IP network of GSN to

transmit audio, video and text (chat) data in real

time. A teleconference also offers the possibility of

having a presentation from one participant to the

others (e.g., a PowerPoint presentation) or sharing

an application. There are two different categories of

teleconference services, a point-to-point (two-

person) conferencing system and a multipoint

conferencing (point to multipoint), which allows

three or more participants to sit in a virtual

conference room and communicate as if they were

sitting right next to each.

The teleconference service is integrated with the

instant messaging service. The teleconference

system has been tested under various use scenarios,

including synchronous teleconferences among a

number of schools all over Greece and the central

offices of the Greek Ministry of Education. Users

participating in the teleconference can see each other

(the screen is separated to show the input from the

web cameras of all participating users), and when a

user is speaking he is shown in the central screen, so

that all the others can see and understand who is the

speaker at any time.

4 CONCLUSIONS

All European countries have developed or are in the

process of developing telematic services that focus

on the needs of their respective educational

communities. The Greek School Network has

developed a number of services for the educational

community in Greece, using state of the art

technology. The online services offered to the

educational communities must include a variety of

tools for helping in the communication between their

members and in the introduction of new educational

methods. The needs of the educational communities

around the world for online services and educational

material are growing rapidly, making it necessary

for all countries to try to find ways to meet these

demands. One parameter that must be always kept in

mind during this effort is the cost of the services

offered, since these services must be provided to the

students and teachers free of charge. This makes

Open Source solutions preferable to commercial

options. Since the educational communities and

especially the pupils must be protected from

ineligible material, extra care must be taken

regarding content delivery and security. A great deal

of research has taken place in recent years on new

methods and e-learning environments, new ways of

approaching e-learning, and new tools that people

can use. The GSN participates in these efforts by

providing an asynchronous e-learning environment

and a variety of online services to the educational

community of Greece.

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