4.5 Network Protocol Design ~ Ilmu Tanpa Sempadan

Open Source, Delay Tolerant Network, Internet of Things

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Friday, December 12, 2014

4.5 Network Protocol Design

Figure 4.3 shows the flow of the email in the networking protocol. This email queue delay period was set by the email system administrator. It can be set to minimum value 0 and maximum value is 2147483647 due to maximum value for a 32-bit signed integer (int32) supported by a SQL database. This means that the email data can be kept in temporary storage for a maximum period of 2147483647 minutes equal to 4083 years. The user at the offline server will write and send an email at application stage where the email data will be stored in the offline mail server for a maximum period of 4083 years before it being discarded. If the offline or online email server computer was shutdown or restart, the pending email remains in the database and will eventually discard when the time delay exceeded. Once the offline mail server connected to infomediary device, the pending email data will move through TCP in Transport layer where the application use NetBIOS over TCP/IP (NBT) to request NetBIOS name server to send an IP address of the destination NetBIOS at infomediary device [20]. Link layer builds an ethernet frame and pass it to the network operating system to be sent to the NetBIOS name server. The NetBIOS name server sends back the NetBIOS name. After the TCP connection is established, the application transfers the file to the target host which is infomediary device.

Figure 4.3: Networking Protocol flow
On the other side, when infomediary device establishes a connection with an online mail server computer, the email data is transferred to the mail server database. The data are transferred packet by packet and when the last packet arrives, the files are reassembled and completed files passed to the application layer. Figure 4.4 shows the Store and forward operation between mail server A, infomediary device and mail server B. Each node contains storage to store the email data.

Figure 4.4: Store and Forward


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