IP

Internet Protocol (IP) is the primary part of the Network Layer of the OSI Model that is responsible for routing traffic across network boundaries. It is the protocol that is responsible for addressing. IPv4 is probable the version that most people are familiar with and it has been around since 1974. IPv6 is its current successor and due to a shortage of available IPv4 addresses compared to the explosive increase in the number of devices that use IP addresses, IPv6 is rapidly increasing in use.

When IP is chosen as the protocol type the available option to further specify the protocol is the protocol number. This is used to narrow down which protocol within the Internet Protocol Suite and provide a more granular control.

Protocol Number

IP is responsible for more than the address that it is most commonly associated with and there are a number of associated protocols that make up the Network Layer. While there are not 256 of them, the field that identifies them is a numeric value between 0 and 256.

In the Internet Protocol version 4 (IPv4) [RFC791] there is a field called “Protocol” to identify the next level protocol. This is an 8 bit field. In Internet Protocol version 6 (IPv6) [RFC2460], this field is called the “Next Header” field.

Protocol Numbers