5.4.1 Server Computer

5.4.1        Server Computer

            The offline server computer is connected to a wireless access point using ethernet cable CAT5. The IP address configured to 192.168.1.7, subnet mask to 255.255.255.0, default gateway to 192.168.1.1 and DNS Server to 192.168.1.1. While, the online server computer is connected to Wireless ADSL Modem using ethernet cable and the IP address also configured with the same address as the offline server computer. This similar configuration is needed for a success database synchronization process at both server computers.

5.4 Implementation Details

5.4  Implementation Details

This offline email system consists of the server computer to run a mail server for both offline and online side, web server application to deliver web access to the user, mail server, mail client, synchronization database application on the server computer, infomediary device as a data mule and a system control graphical user interface.

5.3 Requirements

5.3  Requirements

Table 5.2 shows the hardware requirements for this system which is consist of one offline server computer, offline side wireless access point, android phone as an infomediary device, one online server computer and online side Wireless ADSL Modem.

No	Items	Details
1.	Offline server computer (Details in Appendix B)	Laptop Lenovo Z460Intel Core i5-460M 2.53GHz RAM: 4GB RAM Storage: 500GB HD OS: Windows XP SP3 NIC: Realtek Semiconductor RTL8101 PCIe Fast Ethernet Adapter
2.	Online server computer	Desktop PC Intel i3 2.93GHz RAM: 4GB RAM Storage: 700GB HD Samsung HD754JJ OS: Windows XP SP3 NIC: Realtek Semiconductor RTL8101 PCIe Fast Ethernet Adapter
3.	Offline side Wireless Access Point (Details in Appendix C)	D-Link DWL-2100AP Data Transfer Rate: 54 Mbps Data Link Protocol: IEEE 802.11b, 802.11 Super G, IEEE 802.11g Interfaces: 1 x Network - Ethernet 10Base-T/100Base-TX - RJ-45
4.	Infomediary device (Details in Appendix D)	LG Optimus 3D P920 OS: Android 2.3.5 Storage: 8GB internal storage + 32GB MicroSD WLAN: Wi-Fi 802.11 b/g/n
5.	Online side Wireless ADSL Modem (Details in Appendix E)	Riger DB 108-WL Wireless ADSL Modem 2/2+ Data Transfer Rate: 54 Mbps Support IEEE 802.11b/g, ANSI T1.413 Issue 2, ITU G.992.1 (G.dmt) Annex A,C, ITU G.992.2 (G.lite), ITU G.992.3 ADSL2 (G.dmt.bis), ITU G.992.4 ADSL (G.lite.bis), ITU G.992.5, ADSL2+, Extended Reach(READSL2)

Table 5.2: Hardware Requirements

Table 5.3 shows the software needed for this system which is Uniform Server 7.1.4, hMailServer 4.4.4, Roundcubemail 0.7.2, FreeFilesync 4.6 and Samba File sharing build 111107m.

No.	Items	Details
1.	Uniform Server 7.1.4	Uniform Server is a WAMP package used to run a server on any MS Windows OS based computer. It is small and mobile to download or move around and can also be used or setup as a production or live server [21].
2.	hMailServer 4.4.4	HMailServer is a free mail server for Microsoft Windows. It supports the common e-mail protocols (IMAP, SMTP and POP3) and can easily be integrated with many existing web mail systems. It has a flexible score-based spam protection and can attach to virus scanner to scan all incoming and outgoing email [15].
3.	Roundcubemail 0.7.2	Roundcube webmail is a browser-based multilingual IMAP client with an application-like user interface. It provides full functionality of an e-mail client, including MIME support, address book, folder manipulation, message searching and spell checking [18].
4.	FreeFilesync 4.6	FreeFilesync is a free and open source folder and file synchronization program that features a beautiful, two pane user interface and a host of powerful options. It can compare files by their content or by file size and date, synchronize files and subfolders, process multiple pairs of folders at once, load/save folder comparison sessions, create batch jobs that can be run from the command line, and can handle cloned. It also offers UniCode and Network support and also a portable [22].
5.	Samba File sharing build 111107m	Enable access of android device storage over Wi-Fi as a Windows shared folder [23].

Table 5.3: Software Requirements

There are two additional requirements for this thesis which are TM Streamyx Dynamic 1 MBps Internet Service Provider (ISP) and DtDNS. 1 MBps internet connection provided by TMnet Internet Service Provider is sufficient for this offline email system. DtDNS service is a DNS hosting and DNS management services with a focus on dynamic DNS and dynamic IP address management [24]. DtDNS was used to solve the dynamic IP limitation of the internet connection to ensure accessibility of the system from the Internet.

5.2 Implementation Issues

5.2  Implementation Issues

            There are some implementation issues that limiting the design and operation of the offline email system as per below:

i)                    The offline email system accessibility is limited by the wireless local area network (WLAN) coverage range. The D-Link DWL-2100AP was used as a Wi-Fi access point at the offline mail server. Table 5.1 shows the effective range of D-Link DWL-2100AP. Details of D-Link DWL-2100AP shown in Appendix C. Riger DB 108-WL Wireless ADSL Modem 2/2+was used as a Wireless ADSL Modem at the online mail server with the same effective range of D-Link DWL-2100AP as shown in Table 5.1.

Indoors		Outdoors
Transfer Rate	Effective Range	Transfer Rate	Effective Range
54 Mbps	30 Meters	54 Mbps	95 Meters
48 Mbps	32 Meters	11 Mbps	290 Meters
36 Mbps	37 Meters	6 Mbps	420 Meters
24 Mbps	45 Meters
18 Mbps	60 Meters
12 Mbps	68 Meters
9 Mbps	77 Meters
6 Mbps	90 Meters

Table 5.1: D-Link DWL-2100AP indoors and outdoors coverage range

           

ii)                  The speed of database synchronization process limited by the network data transfer rate of the Wi-Fi access point at each server computers. The D-Link DWL-2100AP used as a Wi-Fi access point at the offline mail server has network data transfer rate up to 54 Mbps which is 54 megabits per second for Standards IEEE 802.11b/g. Riger DB 108-WL Wireless ADSL Modem 2/2+was used as a Wireless ADSL Modem at the online mail server. The network data transfer rate is up to 54 Mbps for Standards IEEE 802.11b/g. It is the same as shown in Table 5.1 for D-Link DWL-2100AP. The ADSL, ADSL2 and ADSL2+ network data transfer rate are up to 24 Mbps.

iii)                Infomediary device battery life is important to ensure the data can be moved from both offline and online side without interruption. LG Optimus 3D (P920) can offer up to 250 hours in standby mode as shown in Appendix D.

iv)                User only can register a new email account at online mail server side. This offline email system did not enable email registration page on the offline mail server because of conflict may occur with online mail server registration database or several other offline mail server registration databases. Since an offline mail server can be more than one and only one online mail server required, registration system only implemented on online mail server to avoid database conflict. Data conflict most likely happen when same username registered on several mail servers. This will cause database synchronization cannot be done when either data might be deleted or both.

5.1 System Platform and Environment

5.1  System Platform and Environment

            Operating system for server computer is Windows XP 32bit because of convenient development and maintenance. Infomediary device runs on android 2.3.5 to support interoperability with Windows XP 32bit. User can use any standard web browser from any platform such as Linux or MAC to access this offline email system. There are two types of networking environment involve in this offline email system which is offline networking and online networking. Offline networking is a local area network with no internet connectivity while online networking is a local area network with internet connectivity. Offline mail client, offline mail server and offline server computer are running on offline networking. Online mail client, online mail server and online server computer are running on online networking. Infomediary device is working in both offline and online networking environment.

5.      SYSTEM IMPLEMENTATION

This chapter started by explaining the system platform and environment. Then the issues arise during implementation and system requirement is discussed. This offline email system is implemented by using suitable existing application to fulfill requirement of TCP/IP mail system working as a DTN mail system. The details of this offline email system implementation are discussed starting from the server computer, web server application, external IP address solution, mail server, mail client, explanation of the database synchronization process, related data for synchronization, database synchronization application and System Control Graphical User Interface (GUI).

4.8 Summary

4.8  Summary

This system main requirement consists of a two mail servers, mail client at each mail server and an infomediary device. This offline email system architecture depends on data synchronization among DTN nodes for four primary purposes which are bundled and fragment identification, routing with scheduled and bundle expiration time computations. This design architecture can enable the email to be sent locally in an offline environment or online environment and a delay network connection between this two environment created by infomediary device. This system offers an advantage compare to conventional Wi-Fi Hotspot and native DTN implementation in term of simplicity, user experience and affordability. System implementation is discussed in the next chapter.

Tips Install Java on Ubuntu using Apt-Get command

1)Installing default JRE/JDK

This is the recommended and easiest option. This will install OpenJDK 6 on Ubuntu 12.04 and earlier and on 12.10+ it will install OpenJDK 7.

Installing Java with apt-get is easy. First, update the package index:

sudo apt-get update

Then, check if Java is not already installed:

java -version

If it returns "The program java can be found in the following packages", Java hasn't been installed yet, so execute the following command:

sudo apt-get install default-jre

This will install the Java Runtime Environment (JRE). If you instead need the Java Development Kit (JDK), which is usually needed to compile Java applications (for example Apache Ant, Apache Maven, Eclipse and IntelliJ IDEA execute the following command:

sudo apt-get install default-jdk

That is everything that is needed to install Java.

2)Setting the "JAVA_HOME" environment variable

To set the JAVA_HOME environment variable, which is needed for some programs, first find out the path of your Java installation:

sudo update-alternatives --config java

usually the path should be in /usr/lib/jvm/

Copy the path from your preferred installation and then edit the file /etc/environment:

sudo nano /etc/environment

In this file, add the following line (replacing YOUR_PATH by the just copied path):

JAVA_HOME="YOUR_PATH"

That should be enough to set the environment variable. Now reload this file:

source /etc/environment

Test it by executing:

echo $JAVA_HOME

4.7 Database Synchronization

4.7  Database Synchronization

Data synchronization is important in the DTN email system. This part of the system is to ensure the email data can be transferred from the email storage to the infomediary device and reach the destination storage. Data synchronization operates in the email server computer on both sides. When the email server computer receives an available connection of infomediary device, the data synchronization will begin where the mail server will grab the new data from infomediary device and transfer a new data from mail server to infomediary device at the same time. There are several options available for this purpose which is FreeFilesync, Synchronize It, Beyond Compare 3, rsync etc. FreeFilesync is a free Open Source software for Windows and able to compare and synchronize files and synchronize folders. It supports filters, file sizes greater than 4GB and creation of batch files for automated synchronization. Synchronize It is a commercial folders comparison and data synchronize for Windows. It also supports command line switches for unattended synchronization. Beyond Compare 3 is the commercial folders comparison and data synchronization for Windows. Rsync is a batch of folders and file synchronization tools for UNIX systems. Rsync can copy or display directory contents optionally using compression and recursion. FreeFilesync is suitable for this thesis project being it is a free Open Source for Windows and support for batch file for automated file synchronization.

Infomediary device is working as a data mule. It carries data storage between data communication link. It is able to automatically load and unload the data when arrives at its terminal location. In this thesis, infomediary device requires to establish network connection at the terminal location which is a mail server and Storage to store the email data. A laptop, Tablet PC or a Smartphone can be used for this purpose. An Android Smartphone is used in this thesis project because of its less power consumption and prolongs battery life. An Android Smartphone is smaller and easy to move in between terminal location and able to establish a connection through Wi-Fi. Samba File Sharing is used to provide network storage for the Terminal Location for data synchronization.