VoIP and Unified Communications: Internet Telephony and the Future Voice Network

12

APPENDIXES

12.1 ACRONYMS AND DEFINITIONS

Some terms are defined at the locations referenced in the Index.

0x	Indication that the following characters are a hexadecimal expression.
5ESS	Class 5 Electronic Switching System, CO voice switch that serves end users.
AB	Two signaling bits in T-1 CAS when using a superframe.
ABCD	Four signaling bits in T-1 CAS when using the extended superframe.
ABNF	Augmented Backus—Naur Form.
AC	Area Code, in telephone number.
ACD	Automatic Call Distributor, PBX function or machine to spread calls among phones.
ACELP	Adaptive CELP.
ACF	Admission Confirm.
ACK	ACKnowledge, message type to confirm receipt of request or action taken.
ADC	Analog-to-Digital Converter, first step to encode voice as a digital stream.
address	IP address of a host; MAC, DLCI, or other L2 destination or source identifier; cf socket.
ADPCM	Adaptive Differential Pulse Code Modulation, form of compressed voice encoding.
AH	Authentication Header, form of IPsec that digitally signs but doesn't encrypt.
A-Law	Form of PCM companding used with E-1 links.
ALF	Application Level Framing.
ALG	Application Layer Gateway.
ALI	Automatic Location Information (Identifier), geographic indication associated with a telephone, landline or cellular, delivered to a PSAP with E911 call; kept in an ALI database.
AN	Acknowledgment Number, associated with an octet in a TCP stream or a packet.
analog	Can take on any value to represent sound; see digital.
ANI