The Internet Protocol: IPV4 Packets
Now that we have clarified the allocation of IPv4 addresses and the utilization of the longest prefix match to forward IPv4 packets, we can have a more detailed look at IPv4 by starting with the format of the IPv4 packets.
The IPv4 packet format was defined in RFC 791. Apart from a few clarifications and some backward compatibility changes, the IPv4 packet format did not change significantly since the publication of RFC 791. All IPv4 packets use a 20-byte header as shown below. Some IPv4 packets contain an optional header extension that is described later.
IPv4 Packet Header
Press + to interact
The IP version 4 header
Fields of The Header
The main fields of the IPv4 header are:
- A 4 bit version that indicates the version of IP used to build the header. Using a version field in the header allows the network layer protocol to evolve.
- A 4 bit IP Header Length (IHL) that indicates the
Access this course and 1400+ top-rated courses and projects.