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TCP/IP Tutorial and Technical Overview - IBM Redbooks

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MDCX “ModifyConnection” changes the parameters associated with an<br />

established connection.<br />

DLCX “DeleteConnection” deletes an existing connection. ACK returns call<br />

statistics.<br />

AUEP “AuditEndpoint” audits an existing endpoint.<br />

AUCX “AuditConnection” audits an existing connection.<br />

RS<strong>IP</strong> “RestartInProgress” is a gateway notification to the call agent that an<br />

media gateway or an endpoint is restarting or stopping.<br />

Among those primitives, of specific interest are the notification messages. The<br />

MGCP device uses these messages to tell the call agent of a change of state<br />

<strong>and</strong> typically involve signaling or events. We describe examples of both:<br />

► Signals include ringing, distinctive ringing, ringbacktone, dial tone, intercept<br />

tone, network congestion tone, busy tone, confirm tone, answer tone, call<br />

waiting tone, off-hook warning tone, pre-emption tone, continuity tone,<br />

continuity test, <strong>and</strong> dial tones.<br />

► Events include the on-hook transition, off-hook transition, flash hook, <strong>and</strong><br />

receipt of dial digits.<br />

20.4 Media Gateway Controller (Megaco)<br />

Similar to the use of MGCP in an <strong>IP</strong> telephony network, Megaco addresses the<br />

relationship between a gateway <strong>and</strong> a call agent. However, unlike MGCP,<br />

Megaco supports a broader range of networks, including ATM. This makes the<br />

protocol applicable to a much wider range of media gateways.<br />

After the MGCP st<strong>and</strong>ard was approved, additional proposals <strong>and</strong><br />

enhancements were submitted to the IETF. The Megaco protocol combines<br />

these different st<strong>and</strong>ards into a single architecture <strong>and</strong> is the result of joint<br />

development by the ITU <strong>and</strong> the IETF.<br />

20.4.1 Megaco architecture<br />

Megaco has been architected to support gateways ranging in size from a single<br />

port to thous<strong>and</strong>s of ports.There are two components in a st<strong>and</strong>ard Megaco<br />

network:<br />

► Terminations<br />

► Contexts<br />

738 <strong>TCP</strong>/<strong>IP</strong> <strong>Tutorial</strong> <strong>and</strong> <strong>Technical</strong> <strong>Overview</strong>

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