High-availability Seamless Redundancy (HSR)

Packet Data Network (PDN)
Packet Data Protocol (PDP)
Packet Switched/Packet Switching (PS)
Packet Temporary Mobile Subscriber Identity (P-TMSI)
Policy and Charging Control (PCC)
Private Branch Exchange (PBX)
Private Mobile Network (PMN)
Public Globally Routable User Agent URI (P-GRUU)
Public Land Mobile Network (PLMN)
Public Service Identity (PSI)
Public Switched Telephone Network (PSTN)