Internet Protocol Internetworking Lab 1

Why Internet?

Protocols for Inter-network TCP/IP protocol suite –TCP /UDP – layer 4 – Transport layer –IP network layer Forward packets from network to network Unique address which is globally recognized –Why not MAC/Physical addresses Routing ( algorithms, decisions, tables )

Internet Protocol - Goals Single seamless communication Physical network details to be hidden from applications –Hardware details –Software details Addressing mechanism to locate the network/machine (independent of MAC/Phy address)

Internet Protocol Goals Based on the location of the network – forward the packets For this purpose use – routing algorithms and tables

Solution – IP functions Provide an addressing mechanism –IP addresses IP layer ( network layer) to provide Routing and forwarding mechanisms Is not Reliable – No guarantees Best Effort Delivery

IP Address 32 bits or 4 bytes Each byte – 255 decimal – FF (hex) Typical address –Dotted quad, dotted decimal Two parts – –Network id – locates the network – used in routing –Host id – identifies the host in the network

Classes of IP address Class A –Network id is in 1 st byte, host id in the rest 3 Class B –Network id is in first two bytes, host id in the last 2 Class C –Network id is in the first three bytes, host id in the last byte Class D and E – special cases

Classes of IP addresses

Identifying class

Number of networks and hosts

Specific IP addresses

Network Mask The network mask (subnet mask) where there are 1’s indicates the network ID where there are 0’s indicates the host ID Examples for a class A address: for a class B address: for a class C address:

IP functions

Fragmentation in IP

Identification –used to determine which fragments belong to each other Flag –D flag =0– data may be fragmented –=1 data may not be fragmented Fragment offset –indicates where a fragment belongs in the complete message – measured in octets

Fragmentation field

IP properties Unreliable Connectionless - ? Best Effort