MGCP Call Preservation

MGCP gateway is a Survivable endpoint unlike H323 which is not survivable. What does it mean? It means that an active call through an MGCP gateway will not tear-down and the call will be preserved. As discussed already in another section that an MGCP gateway terminates Layer 2 signalling at the gateway while Backhauling LayerContinue reading “MGCP Call Preservation”

Hardware Conferencing

To make use of DSP resources for a Conference Call, we will have to enable Conference Bridge at the gateway. Configure the following at the gateway: voice-card 0 dspfarm dsp services dspfarm sccp local Loopback0 sccp ccm identifier 2 priority 2 version 5.0.1 sccp ccm identifier 1 priority 1 version 5.0.1 sccp !Continue reading “Hardware Conferencing”

IOS Transcoding

Transcoding is required to enable communication between different Codecs. For example, CUE is G.711 only and will not be reachable from a Branch side if Inter-region codec has been set as G.729. Similarly a UCCX Pilot point is G.711 only and cannot be reached from another site using G.729 codec. To make this communication possible,Continue reading “IOS Transcoding”

Hardware Conferencing in SRST mode (CBarge)

In a scenario where a customer wants to enable Hardware conferencing while in SRST for CBarge as well as in normal operation. We can configure this by registering the conference bridge first to the Call managers and then to the telephony service IP source address. In this way when the gateway will go in SRST,Continue reading “Hardware Conferencing in SRST mode (CBarge)”

MGCP Gateway Setup

MGCP Configuration Using Trombone Feature: To register an MGCP gateway to call manager, follow these steps: Do a show inventory OR show diag to check the position of E1/T1 Enable the E1/T1 by using command – card type T1 0 0 OR card type T1 0 1 (whatever the case may be) Do show verContinue reading “MGCP Gateway Setup”


In a typical ISDN setup for an Inbound call from PSTN to an IP phone (-SCAC-) CCM  –  GW  – PSTN Setup <——- Call proceeding ——-> Alerting ——-> Connect ——> Gateway and PSTN switch exchange Q921 Layer 2 information. Gateway registers with ISDN switch and terminates Q921 at gateway. A Q931 Setup message arrives. TheContinue reading “MGCP Call Flow – ISDN PRI”

MGCP – How it works?

General: MGCP stands for Media Gateway Control Protocol. It’s a client-server protocol which means that it has  to depend on Media Controller (Call agent) for call routing. In case of Cisco this MC is a CUCM. The Call agent controls the ports of a MGCP gateway. UDP Port 2427  is used for communication between CallContinue reading “MGCP – How it works?”

Signalling & Call Set-up

Signalling and Call set-up There are three types of Signalling: 1) Supervisory: On-hook, off-hook, Ringing 2) Address: Communicates the digits that were dialed like DTMF (Dual tome multi frequency) and Pulse dialing 3)Informational: Dial-tone, ring-back tone, recorder tone. Call set-up: 1.The calling phone goes off-hook, closing the circuit to the local CO switch. 2. TheContinue reading “Signalling & Call Set-up”