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

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

IP –responsible for routing the packets from node to node reassembling the packets back into the message

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

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

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 –Expressed in decimal form (each part range from )

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 –Using Subnet mask to identify the network and host address

Subnet Mask –Class A : IP : SM : Network : Host : networks = ( 256 – 2 ) hosts = ( 256 * 256 * 256 – 2 )

Subnet Mask –Class B : IP : SM : Network : Host : networks = ( 256 * 256 – 2 ) hosts = ( 256 * 256 – 2 )

Subnet Mask –Class C : IP : SM : Network : Host : networks = ( 256 * 256 * 256 – 2 ) 254 hosts = ( 256 – 2 )

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