3.      METHODOLOGY

      This offline email system development is using an iterative approach as illustrated in Figure 3.1.

Figure 3.1: Iterative Approach

In step 1, the information from various sources was gathered to define the problem and understand how to actually make the email based on delay tolerant networking. Major findings are listed below:

i)                    RFC5050 is a standard for delay networking define by the DTN Research Group (DTNRG).

ii)                  CafNet is a Carry and Forward delay tolerant network. It implements a delay-tolerant network stack that allows applications to send messages to other network nodes when no end-to-end connectivity is present. CafNet delay-tolerant network stack consists of a CafNet Transport Layer, CafNet Network Layer and one or more Mule Adaptation Layers. Each node connected through link mechanisms where the data is physically carried on a USB key. CafNet prioritizes messages such that data with a higher priority is sent during short bursts of connectivity.

iii)                The Architecture of Email [11] and protocols such as TCP/IP, delay tolerant network (DTN) [10], simple mail transfer protocol (SMTP) [12] and internet message access protocol (IMAP) [13].

In step 2, the development approach of this offline email system is selected and related information is identified. CafNet concept is used in this offline email system where the data is physically carried on a USB Key. The difference is this system data is carried and transferred automatically when it reaches the terminal location through a wireless local area network and database synchronization. The standard for delay networking defines by DTN Research Group (DTNRG) concept applied on data mule and data bundling for its store and forward operation. There are several possible ways to implement the systems including:

i)                                Implementation from scratch by following the native DTN protocol

ii)                              Implementation from scratch by using TCP/IP mail system works as a DTN mail system

iii)                            Implementation using existing application to fulfill requirement of TCP/IP mail system working as a DTN mail system.

The third approach is selected because of the design effort is fairly follows the TCP/IP thus adding some new design to make it working as DTN, a free and open source software is used and adaptation of standard email usage to the end user.

In step 3, the system is designed closely as standard TCP/IP email architecture except for the infomediary device and emails data synchronization implemented to make a connection between separate terminal locations. Step 4, step 5 and step 6 which is implementation, system testing and result analysis progressed simultaneously starting from setting up a local server computer, home server accessible to the internet implementation, mail server, mail client and infomediary device which includes the database synchronization. This is to ensure every part of the implementation is working accordingly and produced the expected result.

Finally in step 7, documentations were recorded including the system requirement, design, implementation, testing and result. The documentation progress simultaneously from the beginning of the project until completed and then finalize at the end. In the next chapter system design architecture is discussed.