Telephony Abbreviations

(Updated: November 14, 2022)

Below is a listing of abbreviations related to telephony technology, with the abbreviations of some general terms and of some more specific ones which can be seen in several disclosed documents from NSA.

This listing is work in progress and will be expanded/corrected frequently.

See also the list of Abbreviations and Acronyms related to SIGINT and COMSEC

Fiber-optic cable abbreviations:

CWDM - Coarse Wavelength Division Multiplexing
DCO - Direct Cable Ownership
DWDM - Dense Wavelength Division Multiplexing
FP - Fiber Pair
IRU - Indefeasible Right of Use
LC - Leased Capacity
MMF - Multi-Mode Fibers
RFS - Ready For Service
SMF - Single-Mode Fibers
WDM - Wavelength-Division Multiplexing

Telephony abbreviations:

AAL-2 - ATM Adaptation Layer, Type 2 (for voice and low-bit-rate data)
AAL-5 - ATM Adaptation Layer, Type 5 (for packet data and ATM signalling)
ADSL - Asymmetric Digital Subscriber Line
ALCAP - Access Link Control Application Part (control plane protocol for the transport layer in UMTS networks)
APN - Access Point Name
ATM - Asynchronous Transfer Mode
ATP - Advanced Technology Provider (Cisco IP telephony?)
AU1 - ?

BTS - Base Transceiver Station (GSM)
BSC - Base Station Controller (GSM)

C7 - Signaling System No. 7
CCH - Common CHannel
CCS - Common Channel Signaling
CdFMID - Cd Fingerprint Mobile Identification Device
CdGID - Cd General Identifier (locks a particular SIM to a particular tariff)
CDR - Call Detail Record
CEPT - Conférence Européenne des administrations des Postes et Télécommunications
CgFMID - Cg Fingerprint Mobile Identification Device
CI - Cell Identifier
CIC - Circuit Identification Code
CK - Confidentiality (or Cipher) Key (UMTS)
CLI - Caller Line Identification, also known as Caller ID
CNI - Calling Number Identification
CSI - Called Subscriber ID (Fax)
CSLI - Cell Site Location Information

DCH - Dedicated CHannel
DCME - Digital Circuit Multiplication Equipment
DPC - Destination Point Code (in the SS7 system)
DSLAM - DSL Access Multiplexer (telephony gateway)
DSME - Destination Short Message Entity

ESN - Electronic Serial Number (uniquely identifies a CDMA phone in the US)

FFU - ?
FP - Frame (Handling) Protocol
FTIN - Forward Terminal Identification Number (INMARSAT?)

GCID - Global Cell-Tower ID
GGSN - Gateway GPRS Support Node
GMSC - Gateway Mobile Switching Centre (GSM)
GPRS - General Packet Radio Services
GRX - Global (or GPRS) Roaming Exchange
GSM - Global System for Mobile communications (2nd generation)
GSMA - GSM Association
GTP - GPRS Tunneling Protocol

HLR - Home Location Register
HSS - Home Subscriber Server

IK - Integrity Key (UMTS)
IMEI - International Mobile Station Equipment Identity
IMN - Inmarsat Mobile Number
IMSI - International Mobile Subscriber Identity
IR.21 - International Roaming document
ISDN - Integrated Services Digital Network
Iu UP - Iu User Plane

Kc - Confidentiality (or Cipher) Key (GSM)
Ki - SIM Card key number

LAC - Location Area Code (16-digit code that identifies the phone's location area)
LAIC - Loopback Access Interface Card
LTE - Long Term Evolution (4th generation)

M3UA - MTP-3-User Adaptation layer (SS7)
MCC - Mobile Country Code
MDN - Mobile Directory Number
MIN - Mobile Identification Number (24-bit number assigned by the wireless service provider to each phone it sells)
MNC - Mobile Network Code
MNO - Mobile Network Operator
MSC - Mobile Switching Center (GSM)
MSISDN - Mobile Subscriber ISDN-Number
MTP-3b - Message Transfer Part Level 3 (Broadband)

NBAP - Node B Application Protocol
NNI - Network-to-Network Interface (ATM)

ODN - Optical Distribution Network
OPC - Originating Point Code (in the SS7 system)
OSME - Originating Short Message Entity

PCM - Pulse-Code Modulation
PDCP - Packet Data Control Protocol
PDP - Packet Data Protocol
PTMSI - Packet Temporary Mobile Subscriber Identity (for GPRS)
PWID - ?

Q_CK1 - ? (Confidentiality Key)
Q_IK1 - ? (Integrity Key)

RAC - Route Area Code
RACH - Random CHannel
RANAP - Radio Access Network Application Part
RegFMID - Regular Fingerprint Mobile Identification Device
RLC - Radio Link Control
RNSAP - Radio Network Subsystem Application Part
ROAX - Roaming Agreement EXchange
RQ1 - ?
RRC - Radio Resource Control
RTIN - Reverse Terminal Identification Number (INMARSAT?)
RTMSI - Radio Temporary Mobile Subscriber Identity (for GPRS)

SCCP - Signalling Connection Control Point
SCTP - Stream Control Transmission Protocol
SIM - Subscriber Identity Module
SGSN - Service GPRS Support Node
SS7 - Signaling System No. 7
SSCF - Service Specific Coordination Function
SSCOP - Service Specific Connection Oriented Protocol
STC - Signalling Transport Converter
SVoIP - Secure Voice over Internet Protocol

TD-LTE - Time Division-Long Term Evolution
TEID - Tunnel Endpoint IDentifier (32-bit(4-octet) field used to multiplex different connections in the same GTP tunnel)
TLLI - Temporary Logical Link Identifier
TMSI - Temporary Mobile Subscriber Identity
TRAN - Terrestrial Radio Access Network
TSI - Transmitting Subscriber ID (Fax)

UDP - User Datagram Protocol
UICC - Universal Integrated Circuit Card
UMTS - Universal Mobile Telecommunications System (3rd generation)
UNI - User-to-Network Interface (ATM)
UTRAN - UMTS Terrestrial Radio Access Network

VLR - Visitor Location Register
Vo5G - Voice over 5G
VoIP - Voice over Internet Protocol
VoLTE - Voice over LTE (4G)
VoNR - Voice over New Radio (5G)
VoSIP - Voice over Secure Internet Protocol
VSAT - Very Small Aperture Terminal

XR1 - ?

A slide from an NSA presentation, showing some records in the
database nicknamed FASCIA, which contains telephony metadata

- eLectures about Telephone Communication Systems

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