Gateway Overview
Cisco offers a wide variety of voice and video gateways. A gateway provides interfaces that allow the Unified Communications network to communicate with an external network. Traditionally, gateways have been used to connect the IP-based Unified Communications network to legacy telephone interfaces such as the PSTN, a private branch exchange (PBX), or legacy devices such as an analog phone or fax machine. In its simplest form, a voice gateway has an IP interface and a legacy telephony interface, and the gateway translates messages between the two networks so that the two networks can communicate.
Gateway Protocols
Most Cisco gateways offer multiple deployment options and can be deployed using any one of a number of protocols. Depending on the gateway that you want to deploy, your gateway may be configurable using any of the following communication protocols:
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Media Gateway Control Protocol (MGCP)
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Skinny Call Control Policy (SCCP)
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Session Initiation Protocol (SIP)
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H.323
Vendor Interface Cards
The Vendor Interface Card (VIC) must be installed on the gateway to provide a connection interface for external networks. Most gateways offer multiple VIC options and each VIC may offer many different ports and connection types for both analog and digital connections.
Refer to your gateway documentation for the protocols, cards, and connections that are offered with your gateway.
Port and Trunk Connection Types
Following are the main types of port connections that you can configure on gateways:
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Foreign Exchange Station (FXS)—FXS ports offer connections to analog stations such as an analog phone, speakerphone, or legacy voicemail system.
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Foreign Exchange Office (FXO)—FXO ports offer analog connections to the PSTN or a legacy PBX.
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T1 Channel Assocatied Signaling (T1/E1 CAS) —T1/E1 CAS connections offer digital trunk connections to a central office, PBX, or other analog device.
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Primary Rate Interface (T1/E1 PRI)—Digital access PRI connections are widely used in corporate communications. T1 PRI is widely used in North America and Japan and offers 23 B-channels for voice and data and one D-channel for common channel signaling at a rate of 1.544 Mb/s. E1 is widely used in Europe, offering 30 B-channels for voice and data, one D-channel for common signaling, and one framing channel. E1 uses of rate of 2.048 Mb/s.
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Basic Rate Interface (BRI)—BRI is a digital telephony protocol, which is used for small office and home communications links, provides two B-channels for voice and data and one D-channel for signaling.
Connection Types per Protocol
MGCP gateways offer the following connection types:
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TI/E1 PRI Digital access
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T1 CAS
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BRI
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FXO
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FXS
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FXS
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BRI
SIP gateways offer the following connections:
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FXS
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FXS-DID
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E&M
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BRI
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BRI QSIG
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T1 CAS
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T1 FGD
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E1 CAS
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T1/E1 PRI
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T1/E1 QSIG
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T1/E1 NFAS
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T1/E1 PRI (MegacomISDN)
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Centralized Automatic Message Accounting (CAMA)
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J1
H.323 gateways offer the following connection types:
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FXS
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FXS-DID
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E&M
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BRI
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BRI QSIG
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T1 CAS
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T1 FGD
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E1 CAS
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T1/E1 PRI
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T1/E1 QSIG
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T1/E1 NFAS
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T1/E1 PRI (MegacomISDN)
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Centralized Automatic Message Accounting (CAMA)
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J1