PFS, the key used to protect transmission of data must not be used to derive any additional keys. If the key was derived from some other keying material, that material must not be used to derive any more keys.
PING. Packet INternet Groper. Utility program that uses an ICMP echo message and its reply to verify that one network node can reach another. Often used to verify that two hosts can communicate over a network.
PPP.
protocol. Formal set of rules and conventions that specify how information can be exchanged over a network.
PSTN. Public Switched Telephone Network.
repeater. Device that regenerates and propagates electrical signals between two network segments. Also known as a hub.
RFC. Request for Comment. Set of documents that specify the conventions and standards for TCP/IP networking.