2014-10-26 ~ Ilmu Tanpa Sempadan

Open Source, Delay Tolerant Network, Internet of Things

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Saturday, November 1, 2014

2.1.1 Detailed explanation in each TCP/IP Layers

            Figure 2.2 shows details of TCP/IP Layers. Each layer stacks on top of each other to form the basic TCP/IP structure and functionality.

Figure 2.2: TCP/IP Layer
A)    Application Layer
      The top layer is an Application Layer. It is used by most applications for network communication such as Telnet, Hypertext Transfer Protocol (HTTP), File Transfer Protocol (FTP), Simple Mail Transfer Protocol (SMTP), Domain Name System (DNS), Routing Information Protocol (RIP) and Simple Network Management Protocol (SNMP). Figure 2.3 shows the interaction between user and HTTP Server. HTTP is used for viewing pages on the internet.

Figure 2.3: Hypertext Transfer Protocol (HTTP)
            Figure 2.4 shows the outbound mail and inbound mail through SMTP. SMTP is used for mail transfer from a mail server to a client computer.

Figure 2.4: Simple Mail Transfer Protocol (SMTP)
            DNS is a naming system for a computer that is connected to the internet. It finds the nearest DNS server and requests the IP address of the website before it is able to connect into that website. As an example; turns into This naming system used because is far easier to remember than
            RIP is used by router to exchange routing information with each other. This gives computers network information as to where to route the packets through. This gives a simple easy path for the data to go through, instead of the computer sending the packet to every other computer on the internet. SNMP enables user to manage server remotely from other devices in a network.

B)    Transport Layer
      The second layer is Host-to-Host Transport layer. Application layer will inform this layer that it has some data to be sent. There are two protocols which are Transmission Control Protocol (TCP) and User Datagram Protocol (UDP). TCP is a reliable one-to-one connection service. This connection oriented protocol ensures data transmitted accurately. This layer also manages errors such as packet loss, sequencing and acknowledgement of how many packets were sent. It negotiates and maintains a connection between two hosts. It uses the connection to ensure the receiver is ready to receive a packet. It acknowledges sender that it accepts the packet and retransmit a packet that is not acknowledged by the receiver. UDP is a one-to-one or one-to-many communication service. It is very unreliable and connectionless because UDP cannot guarantee delivery of packet data. UDP is used when the data want to be sent is very small (one packet) and do not a TCP connection or when the applications provide reliable delivery. It does not check if the receiver is ready when it sends a packet to a host. When it receives a packet, it does not acknowledge the delivery because it does not send a large number of messages. UDP required much less bandwidth than TCP. UDP is used by application layer protocol such as DNS to transmit short messages such as name query and response. UDP reject corrupted packet as much as TCP did. Streaming media also use UDP because it is low overhead. The media player will buffered enough of arriving data to be able to request a new copy of a bad packet from the sender and receive it before it was needed.

C)    Network layer
      The third layer is Network Layer or Internet Layer. This layer is accountable to handle addressing, packaging and routing functions. This layer has many protocols such as Internet Protocol (IP), Address Resolution Protocol (ARP), Internet Control Message Protocol (ICMP) and Internet Group Management Protocol (IGMP). IP is a main protocol of the Internet Layer. This is an unreliable, connectionless protocol for routing between hosts. This protocol makes its best effort to get the data to receiving host. If a piece of data does not get through, this protocol does not attempt to recover that piece of data. It manages the movement of packet between sending and receiving host. It was responsible for routing packet to their destination. Dividing them into a size that would fit through the router among their route and addressing packet. An IP address is a series of number that is assigned to the physical hardware address of the host. ARP resolves the Media Access Control (MAC) address which is a unique number given to every network capable device. It helps to deliver the packets to the receiving host by giving the packets a path to go through. It looks up physical address that link to an IP address. ICMP is the protocol that makes sure that all of the packets go through the network. If a packet is not delivered, or is lost during transmission, this protocol sends another request to send the packet. It carries error messages and provides the simple diagnostic capability. IGMP is used by router to track group membership on the subnet and manages groups of hosts such as computers, routers etc.

D)    Data Link Layer
      The fourth layer is the Data Link Layer or Network Access layer. This layer handles packet transmission. This is designed to give the layers that stack on top of this to be able to function normally across any network medium such as Ethernet or wireless LAN. The data link layer is divided into two sub layers which is logical link control (LLC) and media access control (MAC). LLC is a function required to establish and control of logical links between local devices on a network to allow different technologies to work seamlessly with the higher layers. MAC is a procedure to control device access to the network medium. Usually networks sharing a medium such as a single network cable or a series of cables that are electrically connected into a single virtual medium. Rules are needed for managing the medium to avoid conflicts. Example of a MAC is ethernet uses the CSMA/CD method while Token Ring uses token passing. Data Link Layer also responsible for Data Framing, Addressing and Error Detection and Handling.
E)    Physical Layer

      The bottom layer is Physical Layer. The physical layer of the network involves of hardware elements such as network interface cards, cables and repeaters. Ethernet is the most common protocol used at the physical layer. Ethernet network such as 10BaseT or 100BaseTX specifies the configuration of the hardware elements such as type of cables that can be used, the optimal topology such as star topology, bus topology etc. and the maximum length of cables.

Friday, October 31, 2014



In this chapter, the background to Transmission Control Protocol and Internet Protocol (TCP/IP) and delay and disruption tolerant networking (DTN) presented. The details begin by describing the TCP/IP layers, internet addressing and how TCP/IP works. Then continue by describing the basic problem when using internet protocols and outline the reason to use DTN. After that architecture of DTN is discussed and then the TCP/IP and DTN is compared.
The Transmission Control Protocol and Internet Protocol (TCP/IP) enable communications across a vast and heterogeneous collection of networks. Transmission Control Protocol (TCP) is a reliable data delivery and connection service protocol. TCP making sure the packet delivery is acknowledged and transmitted as needed.
The TCP/IP offers two basic communication services that operate on top of IP which is Transmission Control Protocol (TCP) and User Datagram Protocol (UDP). There are five main layers in TCP/IP which is Application Layer, Host-to-Host Transport Layer, Network/Internet Layer, Data link/Network Access Layer and Physical Layer [4]. Figure 2.1 shows a TCP/IP Architecture Layers compare against Open Systems Interconnection (OSI) Model Layers. In this comparison, the TCP/IP application layer includes the OSI application layer, presentation layer and session layer. Its Host-to-Host transport layer includes the some part of the OSI session layer and OSI transport layer. The Network/Internet Layer is a subset of the OSI network layer. The Data link/Network Access layer includes the OSI Data link Layer. Physical Layers in TCP/IP and OSI Model is on the same level. Mostly TCP/IP Physical Layer is included in Data link/Network Access layer and also called Network Interface Layer. 

Figure 2.1: TCP/IP Protocol Architecture

Wednesday, October 29, 2014

1.7 Summary of chapters

This chapter gives a brief introduction to the topic and objectives of this thesis. TCP/IP, the concept of delay-tolerant networking and its architecture discussed in more details in the next chapter. There is discussion of TCP/IP and DTN comparison along with how TCP/IP may work as DTN from the standpoint of an email system. In Chapter 3, the methodology being used is discussed. In chapter 4, the offline email system architecture was designed based on the input from chapter 2 and the approach proposed from chapter 3. In chapter 5, the design concepts from earlier chapters are implemented. The system test and the result discussed in chapter 6. Final chapter summarizes the thesis by reviewing what was done and pointing out potential directions for future development.

Monday, October 27, 2014

1st Prize 6th Sarawak Open Source Competition 2013 conducted by Sarawak Information Systems Sdn Bhd

An Offline Email Implementation Based on Delay Tolerant Network (DTN) which represent UNIMAS, win 1st Prize 6th Sarawak Open Source Competition 2013 conducted by Sarawak Information Systems Sdn Bhd. Award given on 21 October 2014 at Imperial Hotel Kuching during Sarawak Information Systems Sdn Bhd (Sains)’s Corporate Social Responsibility (CSR) cum Media Night with the Chief Minister.


1.6 System Advantages

There is only one mail server required to be connected to the internet and rural mail server can be extended to more than one. This offline email system is based on DTN fundamentals, store and forward operation by using TCP/IP. It is easy for implementation and system requirement is easy for maintenance. Finding of hardware malfunction replacement can be done easily. This system offers simplicity usage with a less complicated system and fulfills the typical user experience. User only need a web browser application to access the offline email system either from their personal computer, tablet PC or Smartphone. By using a windows based system, awkward environment can be avoided especially for inexperienced user and hence there is no need for special training if it was using Mac OS, Linux or other Unix system. There is no needs for the rural users to travel very far to the internet connected area to have the opportunity as equal as the people who live near to the internet connection. Only one user is moving instead of all users moving to the internet connected area. The system is affordable where there are no complicated requirements needed. There is the hardware cost needed for this offline email system implementation. Related software required is a free and open source. Estimated cost for this offline email system is RM6034.00 as shown in Table 1.1. This total cost consists of one offline mail server, one informediary device, one online mail server and one month internet subscription cost. The additional cost will be needed to support another rural area by providing another offline mail server which will cost RM2304 for offline mail server computer and wireless access point. Compared to other Wireless Service Provider such as Danawa Wireless Solution Provider, the cost is very high as shown in Table 1.2. Appendix A shows the details of the Danawa service. To use Danawa service, multiple Wi-Fi internet hotspots required for each rural area. And each Wi-Fi internet hotspot for 1 MBps which is one megabytes per second price is RM3000 monthly subscription and RM1000 for one time installation. By using DTN method, only one Wi-Fi internet hotspot required and can be extended to another rural area by providing offline mail server at each area where each area connected by infomediary device.
Cost (RM)
Offline mail server (Laptop Lenovo Z460)
Offline side wireless access point (D-Link DWL-2100AP)
Infomediary device(LG Optimus 3D P920)
Online server computer (Desktop Computer)
Online side wireless ADSL Modem (Riger DB 108-WL Wireless ADSL Modem 2/2+)
TM Streamyx Dynamic 1 MBps Internet Service Provider (ISP)
(Monthly Subscriptions)
Total Cost:
Table 1.1: Estimated Cost for Offline Email System based on DTN
The user interface is based on webmail where it can be accessed from a desktop computer, laptop or a mobile phone. The user can interact with the email application as it is a standard email and most users are familiar with it. It also uses the standard email address as an example: and webmail address as example for offline webmail and for online webmail File transfer was executed automatically from each mail server to infomediary device whenever they are connected. The disadvantage of using native DTN is due to the complexity of the system while offline email system offers simplicity and every part of the offline email system is easy to implement and maintain. It is much convenient for the users and the email system administrator.

Table 1.2: Cost for DANAWA Wi-Fi Hotspot implementation

Some of DTN email such as Bytewalla 5 did not offer email registration at user side where it only can be done on administrator side. While this offline email system enables user to register a new email account from online mail server side.

1.5 System Implications

At offline mail server, users have a local mail access. They can manage, read, send or receive email locally to another person in the local area network. Infomediary device allows email data to be sent from offline network to online network and vice versa. This extends the offline email system network by allowing user to read, send and receive email in an offline environment or in an online environment. At the online mail server, users also have a local mail access. Since the online mail server is connected to the internet, users able to send and receive email from other Internet Mail such as Gmail and Hotmail directly. With the help of infomediary device, online users can receive or send email to the rural users at the offline mail server. This offline email system is not using native DTN protocol but applies a DTN store and forward fundamentals in TCP/IP by using a database synchronization process.