Inter-networking Layer (IP)
Sub-network Independent (works over any type of real network)
End-to-end delivery of datagrams (global addressing)
Fields:
- Version number of the Internet Protocol
- Internet Header Length (number of 32 bit words in the IP header)
- Type of Service (e.g., low delay, high bandwidth)
- Total Length (the number of bytes in the whole datagram)
- Identification (unique identifier for the datagram)
- Flags (e.g., don’t fragment)
- Fragment Offset
- Time to Live (in real seconds after discarding the datagram)
- Protocol used (e.g., TCP, ICMP, UDP)
- Header Checksum protects from packet corruption checked by hosts and every gateway
- Source Address
- Destination Address
- Options (e.g., source route, security)
- Padding (filling to get a multiple of 4 bytes)