Internet Protocol (IP Protocol) -

1. It is connectionless datagram protocol.
2. It is host to host network layer delivery protocol designed for the internet.
3. It is a set of requirements for addressing and routing data on the Internet.
4. It is unreliable protocol because it does not provide any error or flow control.
5. is the method or protocol by which data is sent from one computer to another on the internet.

Functions of Internet Protocol -

1. Reassembly :- Internet Protocol keeps track of the way messages between computers are broken into packets. Since most messages are too big to fit in one packet, and since packets aren't sent in any organized order, they must be reassembled as they arrive at the recipient.

2. Addressing :- IP packet headers contain addresses that identify the sending computer and the receiving computer. Routers use this information to guide each packet across communication networks and connect the sending and receiving computers.

3. Options :- IP includes optional features such as allowing the sending computer to decide the path its packets take to get to the receiving computer, to trace the path they take or to include added security in the packets.

4. Timeouts :- Each IP packet contains a self-destructive counter that limits its lifetime. If a packet's defined lifetime expires, the packet is destroyed so that the Internet doesn't get overloaded with broken packets wandering aimlessly.

5. Types of Service :- IP supports traffic prioritization by allowing packets to be labeled with an abstract type of service.

Header Format of Internet Protocol :-

1. Version :- It is the version of IP Protocol. It's bit value is 4 in static.

2. Header length :- It is the length of the header in 32-bit words. Minimum is 20 bytes and maximum is 60 bytes.

3. Types of Service :- It specifies how the datagram should be handled.

4. Total Length :- It is the length of the entire (header + data). The minimum length is 20 bytes, and the maximum is 65537 bytes.

5. Identification :- It is used to differentiate fragmented packets from different datagrams.

6. Flags :- It is used to control or identify fragments.

7. Fragmented Offset :- It is used for fragmentation and reassembly if the packet is too large to put in a frame.

8. Time to Live :- It limits a datagram’s lifetime.

9. Protocol :- It defines the protocol used in the data portion of the IP datagram.

10. Header Checksum :- It is used for error-checking of the header. If a packet arrives at a router and the router calculates a different checksum than the one specified in this field, the packet will be discarded.

11. Source IP address :- It is the IP address of the host (sender).

12. Destination IP address :- It is the IP address of the host (receiver).

13. Options :- It is used for network testing. It is usually not required for every datagram.

14. Padding :- It is variable size bit field.