1. Agenda Last class: Network Hardware Today: Network Protocols –How do computers talk to each other? –Needs? Same hardware Same rules (protocols) for encoding data “Standards of Interoperability”

2. Protocol for Data Encoding Sending data: flashing light in cable Light = 1No light = 0 Need same way to talk so all computers know 001001011110101010 101011100100100110 What does that mean?

3. Protocol for Data Encoding Ex: You want to send 0010010111101… from Shanghia to Beijing –What info do you need to include? 0010 0101 1110 1010 1010 1001 1110

4. Protocol for Data Encoding Ex: You want to send 0010010111101… from Shanghai to Beijing –What info do you need to include? Address (IP address) Where to start and end, other RULES to read it 0010 0101 1110 1010

5. TCP/IP TCP = transmission control protocol IP = Internet Protocol TCP/IP are communication rules so computers can understand each other 001001011110101010 101011100100100110 Using TCP/IP, I can read it! Coded with TCP/IP rules

6. TCP / IP and How Internet works Ex: You want to send an email from Shanghai to a friend in Beijing 1.The email is cut into small ~1kb packets (TCP) 2.Each packet has the (IP) address and goes there using any route 3.The packets are put together again (TCP)

7. Analogy Cut e-mail up Code it (address, order) Send it in many ways Decode it To Mr Z, Hi my name is Mr Y To Mr Z Hi my To Mr Z name is To Mr Z Mr Y Packet 1Packet 2 Packet 3 Internet 101011 101110 0011101 010110 1111100 010010 0011101 010110 101011 101110 1111100 010010 Packet 2 name is Packet 1 Hi my Packet 3 Mr Y Order Hi my name is Mr Y Internet

8. Assignment We are going to copy this process! I wrote an “email” to each student Then I cut it up into packets Then I coded it Then I send it many ways (to YOU) Your job: Find your message and decode it

9. TCP: What do the numbers mean??? 001001011110101010 101011100100100110 ??? 001001011110101010 101011100100100110 Using TCP/IP, it makes sense! Coded with TCP/IP rules

10. TCP/IP Rules (just for this) HEXADECIMAL, ASCII All packets follow this rule for order: –IP address –Total number of packets (1 bit) –Packet number (1 bit) –Start message character (1 bit) –Message (2 bits each character) –End of message character Example:1154AF22ECD987625417