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.
