Voice Over Internet Protocol (VoIP)

Copyright © 2006 Heathkit Company, Inc. All Rights Reserved

Presentation 8 - MGCP and Megaco/H.248

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Objectives

At the end of this presentation, you will be able to:

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Explain the difference between MGCP and Megaco/H.248.

Explain the difference between a Media Gateway Controller (MGC) and a Media Gateway (MG).

Describe the actions of an MGC and MG during an MGCP call.

Recognize the difference between MGCP commands and Megaco commands.

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PSTN(Voice)

Cable(Video)

Internet(Data)

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Why so many call processing (signaling) protocols?

H.323 has its roots the telephone world.

SIP has its roots the Internet world.

MGCP and Megaco/H.248 has its roots in the cable world.

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Simple Gateway Control Protocol

(SGCP)

Internet ProtocolDevice Control

(IPDC)

Media GatewayControl Protocol

(MGCP)IETF

Media GatewayControl Protocol(Megaco/H.248) IETFITU

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What is MGCP?The call processing (signaling) protocol for

voice/data/ and video that was the predecessor of Megaco.

Originally released as an “informational document” rather than a standard.

Equipment was developed based on this protocol some of which is still being used and marketed today.

Considered by most to be “on its way out.”

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What is MGCP?Another multimedia signaling

protocol.

A protocol that acts as an interface between a media gateway controller and a media gateway.

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VoIP ParadigmsH.323 – Terminals, Gateways,

Gatekeepers, and Multipoint Control Units (MCUs).

SIP – Clients and Servers

MGCP – Call Agents, Signaling Gateways, and Media Gateways.

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MGCP TermsMedia Gateway Controller (MGC) –

Handles call signaling and controls media gateways.

Call Agent (CA) – Another term for a Media Gateway Controller (MGC)

Media Gateway (MG) – Handles the conversion and transfer of the voice stream.

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Separation of Call Signaling from Media Transfer.

CallSignaling

CallSignaling

Call Signaling

over IP

MediaTransfer

MediaTransfer

MediaTransfer over IP

Gateway Gateway

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The MGCP Architecture

MediaGateway

Controller(MGC)

Call Signaling

over IP

MediaGateway

(MG)

MediaTransfer over IP

MediaGateway

Controller(MGC)

MediaGateway

(MG)

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Internet

MediaGateway

MG-1

MediaGateway

MG-2

Media Gateway

Controller(MGC)

RoutingDatabase

Hey MG-1! Monitor Phone 1 for an “off hook”

condition.

Phone-1 Phone-2

ACK

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Phone-1

Internet

MediaGateway

MG-1

MediaGateway

MG-2

Media Gateway

Controller(MGC)

RoutingDatabase

Phone-2

ACK. Send him a dial tone.

Hey MGC! Phone-1 just went off-hook.

Buzzzzz…

Roger. Dial tone sent.

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Phone-1

Internet

MediaGateway

MG-1

MediaGateway

MG-2

Media Gateway

Controller(MGC)

RoutingDatabase

Phone-2

ACK. Collect the dialed digits.

Okay, he dialed1-269-925-6000.

1-269-925-6000

Roger. I will collect the digits.

ACK. I have them.

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Phone-1

Internet

MediaGateway

MG-1

MediaGateway

MG-2

Media Gateway

Controller(MGC)

RoutingDatabase

Phone-2

Monitor for “On hook” condition.

Roger. I will do that.

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Phone-1

Internet

MediaGateway

MG-1

MediaGateway

MG-2

Media Gateway

Controller(MGC)

RoutingDatabase

Phone-2

Seize the circuit and set it up like

this….Roger. Here is how I have it set up…..

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Phone-1

Internet

MediaGateway

MG-1

MediaGateway

MG-2

Media Gateway

Controller(MGC)

RoutingDatabase

Phone-2

Hey Database! Get me the IP address of and best route to this

number?

Here is the information you

requested.

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Phone-1

Internet

MediaGateway

MG-1

MediaGateway

MG-2

Media Gateway

Controller(MGC)

RoutingDatabase

Phone-2

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Phone-1

Internet

MediaGateway

MG-1

MediaGateway

MG-2

Media Gateway

Controller(MGC)

RoutingDatabase

Phone-2

Hey MG-2. Seize the circuit to phone-2 and

set it up like this….

Roger. Here is how I have it set

up…..

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Phone-1

Internet

MediaGateway

MG-1

MediaGateway

MG-2

Media Gateway

Controller(MGC)

RoutingDatabase

Phone-2

Hey MG-2. Ring phone-2.

Roger. Ringing phone-2.

Ring…Ring…

Hey MG-1. Send “comfortringing tones” to phone-1.

Roger. Sending“comfort

ringing tones”.

Ring…Ring…

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Phone-1

Internet

MediaGateway

MG-1

MediaGateway

MG-2

Media Gateway

Controller(MGC)

RoutingDatabase

Phone-2

Ring…Ring…

Ring…Ring…

Hey MGC. She just picked up

the phone.

Hey MG-1. Stop the “comfortringing tones” to phone-1.Roger. “Comfort

ringing tones”stopped.

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Phone-1

Internet

MediaGateway

MG-1

MediaGateway

MG-2

Media Gateway

Controller(MGC)

RoutingDatabase

Phone-2

Hey MG-1. Set-up a full duplex connection to MG-2.Roger. Full duplex

connectionset-up..

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Phone-1

Internet

MediaGateway

MG-1

MediaGateway

MG-2

Media Gateway

Controller(MGC)

RoutingDatabase

Phone-2

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Phone-1

Internet

MediaGateway

MG-1

MediaGateway

MG-2

Media Gateway

Controller(MGC)

RoutingDatabase

Phone-2

Hey MGC. Phone-1Just hung up. Hey MG-1 and MG-2.

Delete the connection.

StatisticsReport

StatisticsReport

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Phone-1

Internet

MediaGateway

MG-1

MediaGateway

MG-2

Media Gateway

Controller(MGC)

RoutingDatabase

Phone-2

Hey MG-1! Monitor Phone 1 for an “off hook”

condition.

ACK

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MGCP CommandsCreateConnection CRCX

DeleteConnection DLCX

ModifyConnection MDCX

NotificationRequest RQNT

Notify NTFY

AuditEndPoint AUEP

AuditConnection AUCX

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MGCP ReviewMost of the intelligence resides in the

gateway controller.

The gateways require little intelligence and are therefore simple and inexpensive.

The protocol is considered to be “on its way out” having been upstaged by Megaco.

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Megaco/H.248

Grew out of MGCP.

Joint effort by ITU and IETF.

Maintains many of MGCP’s characteristics and features.

Uses different commands, adds new capabilities, and has two important new abstractions: Terminations and Contexts

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TerminationSoftware construct or abstraction.

Somewhat like a port or a socket in TCP/IP.

An entity that sources or sinks a media stream.

May be physical or logical.

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ContextA collection of terminations.For example, all the terminations

participating in a conference might constitute a single Context.

Or, multiple data paths (voice, data, video) used by a single participant might constitute a single Context.

All terminations are placed in a context. Any termination not in a specified Context, by default, falls into a Null Context.

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Megaco CommandsAdd termination

Subtract termination

Modify termination

Move termination

Notify

Audit capability

Audit value

Service change

Voice Over Internet Protocol (VoIP)

Copyright © 2006 Heathkit Company, Inc. All Rights Reserved

End