1. Introduction to TCP/IP • TCP / IP • including 2 protocols Protocol : = a set of rules that govern the communication between different devices • TCP • Transmission Control Protocol • IP • Internet Protocol • Communication protocol for network

2. TCP • responsible for • dividing the message into packets • verifying the correct delivery of packets from node to node • if unsuccessful >>> re-send / retransmission • until correctly and completely received • provide reliability

3. IP • responsible for • routing the packets from node to node • reassembling the packets back into the message

4. TTL • Time to live • packet sending > with header and data • header : contain information of destination address and some control fields • one of the control fields is TTL • TTL : initialised by the sender to a particular value (e.g. 64) • the number decreased by 1 when the packet passes through 1 router • if TTL reach 0, the packet discard and sender re-send • safety mechanism - prevent packets from travelling forever

5. TCP / IP • = 2 protocol ? • No !!! • TCP / IP is a suit of protocols • FTP / SMTP / SNMP / Telnet / TCP / UDP / IP / PPP / SLIP …. Etc • each protocol with particular feature

6. IP Address • IP Address • = internet protocol address • identify every computer in any network • must be unique within a network • 32 bits binary number (IPv4) • Written as four 8-bit numbers 11011010. 10111100.00000011.00000101 • Expressed in decimal form (each part range from 0-255) 218.188.3.5

7. Each IP address has 2 parts • network address • To identify a network in a larger network (Internet) • host address • identify a particular device in the network • that is : its unique address in the network 218.188.3.4 • Using Subnet mask to identify the network and host address

8. Subnet Mask • Class A : 255.0.0.0 • IP : 218.188.3.5 • SM : 255.0.0.0 • Network : 218.0.0.0 • Host : 188.3.5 • 254 networks = ( 256 – 2 ) • 16777214 hosts = ( 256 * 256 * 256 – 2 )

9. Subnet Mask • Class B : 255.255.0.0 • IP : 218.188.3.5 • SM : 255.255.0.0 • Network : 218.188.0.0 • Host : 3.5 • 65534 networks = ( 256 * 256 – 2 ) • 65534 hosts = ( 256 * 256 – 2 )

10. Subnet Mask • Class C : 255.255.255.0 • IP : 218.188.3.5 • SM : 255.255.255.0 • Network : 218.188.3.0 • Host : 5 • 16777214 networks = ( 256 * 256 * 256 – 2 ) • 254 hosts = ( 256 – 2 )

11. For a LAN • the IP assignment is controlled by the administrator • may be DHCP (dynamic) or • static / fixed IP • For the network “INTERNET” • The IP assignment is issued by InterNIC • Internet Network Information Centre • also responsible for the registering and maintaining the .com, .net (Top-Level Domain names) of the WWW