http://knowledgewithoutlimitation.blogspot.com 2014-11-02 ~ Ilmu Tanpa Sempadan

Open Source, Delay Tolerant Network, Internet of Things

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Friday, November 7, 2014

Unhide hidden folders and files after infected by virus

There is occasional problem occurs when you plug in your USB Thumbdrive to somebody laptop or PC and then suddenly your files and folders was infected and hidden while being replace by nasty shorcuts.

First important steps is to install antivirus and virus definition updated, then scan whole infected computer. In this case, I always use AVG Free.

Then use ccleaner to clean up all the mess in the computer.

After that, we need to fix the hidden files and folders problem. This is the command line to fix the problem:

attrib -H -S G:\*.* /S /D

G: is my USB Pendrive path. Use yours.

cygnosis

Wednesday, November 5, 2014

Installing Wget on Windows

Wget is a linux downloading tools. Not all know that it also available on Windows.

Download wget installer for windows here

Setup path at Environment Variables to installation location.

usage: wget <url>

References: http://gnuwin32.sourceforge.net/packages/wget.htm

2.2 Delay Tolerant Network (DTN)


Delay and disruption tolerant networking (DTN) approach is to overcome the network connection problem when there is no end-to-end connectivity in Internet Transport Protocols. DTN is an approach to computer network architecture that seeks to address the technical issues in heterogeneous network that may lack continuous network connectivity. The DTN application must tolerate delay and disruption with acceptable performance in high loss or delay error environments.

Monday, November 3, 2014

2.1.3 TCP/IP Operation

Figure 2.7 shows TCP/IP operation of accessing a website. After a user click on the website link, the application uses DNS client software to request DNS Server to send an IP address of the destination host. The DNS client software uses UDP and IP to build a DNS name query message to request the IP address of the host that the user wants to connect to. Link layer builds an ethernet frame and pass it to the network operating system to be sent to the DNS Server. DNS Server sends back the DNS name query response message and a target host IP address. It comes in link layer, goes through IP layer where the address information is stripped off and goes back through UDP where the packet integrity is checked. Then it goes up to the DNS client software and passes the IP address to the application.

Figure 2.7: TCP/IP operation of accessing a website
The application then instructs TCP to create a connection. After a TCP connection is established, the application requests a file from the target host. The target host uses TCP to segment the file user wanted into packet and send it to the client. Each packet comes through link layer, through IP and passes it up to TCP which verify the segment integrity and hold until all files segments had arrived. It also acknowledges receiving of the packet to the sender. This cycle repeated until the whole files had been reassembled.

If the packet arrive does not pass the integrity check, TCP discarded it and not send acknowledgement to the sender. If the last packet was not acknowledged within a lot of time, the sender retransmit it. When the last packet arrives, the files are reassembled and acknowledged to the sender. The client then closed TCP connection. The completed files passed to the application where users can access it.

Running telegram CLI on Debian based Linux

Telegram already become my ultimate messenger applications. It is multiplatform. Based on cloud computing, no worries to transfer to other devices. It is all synchronize. Attachment like emails support. I love it. What's more it did support CLI.

git clone https://github.com/vysheng/tg.git && cd tg
sudo apt-get install libreadline-dev libconfig-dev libssl-dev lua5.2 liblua5.2-dev libevent-dev
./configure
make
bin/telegram-cli -k tg-server.pub

usage:
msg contact_name text

quit

Sunday, November 2, 2014

2.1.2 Internet Addressing

There are 32-bit number IP address known as Internet Protocol Version 4 (IPv4) and a new 128-bit number IP address known as Internet Protocol Version 6 (IPv6). An Internet Protocol Version 4 (IPv4) is used in this thesis project and will be discussed. An IP address is divided into two parts which is network part and host part. The part of a public IP address that identifies the network is internationally controlled by the Network Information Center (NIC) located in the Stanford Research Institute in California. The part that identifies the host is controlled locally at a network level. An Internet Address is four octets long. The first few bits in the network part of the address help to interpret the address. These bits indicate the class of the address. A system need to have a public address when it wants to communicate over the internet. There are five Internet Address classes which are Class A/B/C/D/E [5].

Address Class summariesshown  in Figure 2.5. A host ID that contains all 1s is meant to broadcast the packet to all hosts specified by the network. If the network ID also contains all 1s the packet is broadcast on the local network. A host ID that contains all 0s refers to the network specified by the network ID. A source may send all 0s in the source address while trying to find out the correct IP address. The machine is then identified by its MAC address.


Figure 2.5: Address Classes [5]
There are an IP address ranges reserved for private networks within organizations as shown in Table 2.1. These addresses will not be allocated by NIC as public IP addresses for the internet. When a packet goes outside the organization, the local IP address gets translated into the public IP address purchased by the organization to avoid clash problems [5].

Class A: 10.0.0.0 to 10.255.255.255 --------- 1 Class A network
Class B: 172.16.0.0 to 172.31.255.255 ------ 16 contiguous Class B networks
Class C: 192.168.0.0 to 192.168.255.255 --- 255 contiguous Class C networks
Table 2.1: Private addressing
Details of reserved IP address and available IP address shown in Table 2.2.

Class
Address or Range
Status
A
0.0.0.0
1.0.0.0 through 126.0.0.0
127.0.0.0
Reserved
Available
Reserved
B
128.0.0.0
128.1.0.0 through 191.254.0.0
191.255.0.0
Reserved
Available
Reserved
C
192.0.0.0
192.0.1.0 through 223.255.254
223.255.255.0
Reserved
Available
Reserved
D
224.0.0.0 through 239.255.255.255
Multicast group address
E
240.0.0.0 through 255.255.255.254
255.255.255.255
Reserved
Broadcast
Table 2.2: Reserved and available IP addresses [5]

Figure 2.6 shows the Subnet Address. Subnet Addressing is to add another hierarchical level called the subnet. The advantage of the subnet addressing is to allow each organization to have its own internet connection within the internet [6].

Figure 2.6: Subnet Address