(such as SNA's Path Control in its early stages) require a connection-oriented data link layer. Others (like IP) do not. (After the appearance of APPN, SNA could operate on a connectionless data link service as well.) Notable connectionless protocols are: Internet Protocol (IP), User Datagram Protocol (UDP), Internet Control Message Protocol (ICMP), Internetwork Packet Exchange (IPX), Transparent Inter-process Communication, NetBIOS, and Fast and Secure Protocol (FASP). References Network protocols Computer networking Internet architecture Internet protocols