This MIB is an enhancement for existing XGCP-MIB.
        
xGCP is a set of protocols, for example SGCP (Simple
Gateway Control Protocol) and MGCP (Media Gateway
Control Protocol), which are designed as a control 
protocol within a distributed system that appears  
to the outside as a single VoIP/VoATM gateway. 
This system is composed of a call agent (or MGC,
Media Gateway Controller) and of a set of  
'media gateways' that perform the conversion of media   
signals between circuits and packets.  
In the xGCP model, the gateways focus on the audio signal 
translation function, while the call agent handles the  
signaling and call processing functions.
        
Examples of Gateway Control Protocols are:
  * Simple Gateway Control Protocol (SGCP)
  * Media Gateway Control Protocol (MGCP)
        
xGCP assumes a connection model where the basic constructs are:
        
  Endpoints   : sources or sinks of data that could be physical
                or virtual.
        
  Connections : an association between two or more endpoints 
                with the purpose of transmitting data between 
                these endpoints. 
                Once this association is established for both
                endpoints, data transfer between these 
                endpoints can take place. 
        
Connections are grouped in calls. One or more connections 
can belong to one call. Connections and calls are set up at 
the initiative of one or several call agents.
        
Terminologies used:
        
AAL    : ATM Adaptation Layer
AUCX   : Audit Connection Command used by the MGC to find out  
         the status of a given gateway connection.
AUEP   : Audit Endpoint Command used by the MGC to find out the 
         status of a given endpoint.
CCAPI  : Call Control Application Program Interface.
CID    : Channel Identifier
CRCX   : Connection Command from a MGC to request the 
         gateway
MG     : Media Gateway
MGC    : Media Gateway Controller
DLCX   : Delete Command. This command can be initiated by 
         either the MGC or gateway.
GSM    : Global System for Mobile Communications
GW     : Gateway.
HP     : Hairpin
MDCX   : Modify Connection Command from a MGC to request the 
         gateway
NSE    : Negative Stuffing Event 
NTFY   : A Notify Command sent from a gateway to a MGC in  
         response to a RQNT command.
PSTN   : Public Switched Telephone Network
RQNT   : Request To Nofity Command from a MGC to request the 
         gateway to provide a notification for configuration 
         changes.
RSIP   : Restart in Progress Command.  This command can be 
         initiated by either the MGC or gateway.
SPRT   : Simple Packet Relay Transport
SSE    : Silicon Switching Engine
TDM    : Time Division Multiplexing
TGW    : Target Gateway
TWC    : Three Way Calling
VCCI   : Virtual Circuit Connection Identifier
VMG    : Virtual Media Gateway. It is a logical representation of
         a module (or a set of modules) that has MG functionality.
         There could be multiple VMGs in a device.
VoAAL2 : Voice over AAL2