There are several network layer protocols in existence; however, only the following two are commonly implemented as show in the figure:
- Internet Protocol version 4 (IPv4)
- Internet Protocol version 6 (IPv6)
Other legacy network layer protocols that are not widely used include:
- Novell Internetwork Packet Exchange (IPX)
- Connectionless Network Service (CLNS/DECNet)
Discussion of these legacy protocols will be minimal.