In both networking and human contexts a protocol defines the format and order of messages sent and received between human or network entities, and the actions taken on message transmission and receipt. Network protocols of which HTTP, Telnet, SMTP, POP, IMAP, DNS, FTP, UDP, TCP, IP, Ethernet, ADSL, HFC, PPP, and WiFi are examples mentioned in these modules, are defined by published standards (See IETF Standard, IEEE Standard). Human protocols are defined by cultural practices and other, often informal, conventions.

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