Select an RTP port and connect Call Agent in VS .NET

Print ECC200 in VS .NET Select an RTP port and connect Call Agent

3 OK, port number xxxx 1 Call coming in !

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Since instances will occur where media is to be exchanged between gateways controlled by different call agents, signaling communication will be needed between call agents MGCP assumes that such a signaling protocol exists, but does not specify what it is In reality, the protocol between call agents is likely to be SIP

MGCP describes a model containing endpoints and connections Endpoints are sources or sinks of media and include such elements as trunk interfaces or plain old telephone service (POTS) line interfaces Endpoints exist within MGs, and depending on the type of endpoint, it might or might not have one or more external channel or line interfaces For example, an analog line endpoint would be connected to a physical analog line, which would in turn connect to an analog telephone On the other hand, endpoints also exist that have no external connections One example is an announcement endpoint that would reside internally in the gateway Other entities in the IP network would connect to it for the purpose of retrieving an announcement Connections are the allocation of IP resources to an endpoint such that the endpoint may be accessed from the IP network For example, when a call is to be established across a gateway from a circuit-switched line to an IP interface, an ad hoc relationship is established between the circuitswitched line and an RTP port on the IP side This relationship is called a connection, and a single endpoint can have several connections A general representation of endpoints and connections is provided in Figure 6-5

MGCP describes a number of different endpoints as follows:

DS0 channel A digital channel operating at 64 Kbps Such a channel will typically be multiplexed within a larger transmission facility such as a DS1 (1544 Mbps) or E1 (2048 Mbps) In most cases,

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6

the DS0 will carry voice coded according to either G711 m-law or G711 A-law In some cases, the DS0 will carry signaling instead of voice, such as an Integrated Services Digital Network (ISDN) D-channel, in which case it is necessary that the signaling information received be passed from the MG to the call agent for processing

Analog line Typically, an endpoint that interfaces to a standard telephone line and provides service to a traditional telephone In most cases, the media to be received on the analog line will be an analog voice stream, though it could also be audio-encoded data from a modem, in which case the gateway shall be required to extract the data and forward it as IP packets Announcement server access point An endpoint providing access to a single announcement Normally, a connection to this type of endpoint will be one-way, since the requirement is for media to be sent from the announcement rather than to it We assume that the announcement server is within the IP network and IP-based connections are to be made to it Thus, the endpoint does not have any external circuit-switched channels or lines associated with it Interactive Voice Response (IVR) access point An endpoint providing access to an IVR system, where prompts or announcements may be played, and responses from the listener may be acted upon Conference bridge access point An endpoint where media streams from multiple callers may be mixed and provided back to some or all of the callers Packet relay A specific form of conference bridge supporting only two connections This type of endpoint will use packet transport on both connections A typical example would be a firewall between an open and a protected network, where the media stream must pass through such a relay point rather than directly from end to end Wiretap access point A point from which a connection is made to another endpoint for the purposes of listening to the media transmitted or received at that endpoint Connections to a wiretap access point will be one-way only ATM trunk-side interface An endpoint corresponding to the termination of an Asynchronous Transfer Mode (ATM) trunk, where such a trunk might be an ATM virtual circuit Such an endpoint might be used in a gateway that provides an interface between a VoIP network on one side and a Voice over ATM network on the other

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