Communications protocolnetworking, a communications protocol or network protocol is the specification of a set of rules for a particular type of communication.
Different protocols often describe different aspects of a single communication; taken together, these form a protocol stack. The terms "protocol" and "protocol stack" also refer to the software that implements a protocol.
Systems engineering principles have been applied to design network protocols.
Layer 1 protocols
Layer 2 protocols
Layer 2+3 protocols
Layer 3 protocols
Layer 3+4 protocols
Layer 4 protocols
Layer 5+ protocols
Layer 7 protocols
and secure versions of the above (as HTTPS, etc.)