by Firewall.cx web site. A pool of interesting articles on TCP/IP network protocols: UDP, TCP, IPv4, IPv6, IPSec, RIP, OSPF, ICMP, DNS, FTP, TFTP, Ethernet. In the networking and communications area, a protocol is the formal specification that defines the procedures that must be followed when transmitting or receiving data. Protocols define the format, timing, sequence, and error checking used on the network.