Media Gateway Control Protocol Gateways
MGCP is a plain-text protocol used by call-control devices to manage IP telephony gateways.
MGCP (IETF RFC 2705) is a master/slave protocol that allows a call-control device (CUCM) to take control of a specific port on a gateway. MGCP has the advantage of centralized gateway administration and provides for scalable IP telephony solutions. CUCM controls the MGCP state of the configured ports of the gateway. MGCP allows centralized administration of the dial plan and gives CUCM
per-port control of all gateway interfaces. The gateway interfaces are traditional time-division multiplexing (TDM) interfaces, including analog and digital interfaces, which can interconnect PBXs, voice-mail systems, plain old telephone service (POTS) phones, and other traditional device connections. MGCP is implemented with the use of a series of plaintext commands (Session Description Protocol [SDP]) sent over User Datagram Protocol (UDP) port 2427 from CUCM to the gateway.
It is also important to note that for an MGCP interaction to take place with CUCM, the gateway and gateway interface must have CUCM support. Use the Feature Navigator tool (http://www.cisco.com/go/fn) to make sure that the router or switch platform version of Cisco IOS Catalyst Operating System (CatOS) software is compatible with the CUCM version MGCP features.
Endpoint Identifiers
The MGCP call agent (CUCM) directs its commands to the gateway to manage an endpoint or a group of endpoints on the device. Endpoint identifiers address individual endpoint interfaces.
Endpoint identifiers consist of two logical parts. The first part is the local name of the endpoint (hostname of fully qualified domain name). The two parts are separated by an at symbol (@). If the local part represents a hierarchy, the subparts of the hierarchy are separated by a slash (/). The local ID may be representative of a particular gateway/circuit number, and the circuit number may in turn be representative of a circuit ID/channel number.
Figure 10-1 shows a gateway with two endpoint interfaces. The show voice port summary Cisco IOS command would display the hardware T1 or E1 voice WAN interface card (VWIC) in slot 1, subslot 1, port 1 (1/1/1) and the Foreign Exchange Station (FXS) analog interface in slot 2, subslot 1, port 1 (2/1/1). The T1 or E1 card provides the ability to trunk 24 (T1-CAS), 23 (T1-PRI), or 30 (E1) calls to the PSTN. The configuration of the T1 or E1 interface is done primarily in CUCM for MGCP gateways. The first of CUCM's two configured endpoints (S1/SU1/[email protected]) indicates that the T1 interface was configured as an ISDN PRI using the DS1 (digital signal level 1) signaling specification. The second interface is an analog access line number (AALN) that indicates the interface is an FXS or Foreign Exchange Office (FXO) port. An FXS port generates dial tone to the device plugged into the RJ-11 port. End-user devices such as fax machines and analog phones are normally plugged into FXS ports. FXO RJ-11 ports accept dial tone and are normally connected to the PSTN to make and receive phone calls. MGCP gateways do not support caller ID services on FXO ports. If caller ID over analog FXO interfaces is a requirement, H.323 gateways should be used. H.323 is covered in a later chapter.
Figure 10-1 MGCP Endpoint Nomenclature
Slot 2 Subunit 1 Hostname
S1/SU1/[email protected] AALN/S2/SU1/[email protected]
Slot 2 Subunit 1 Hostname
MGCP
AALN/S2/SU1/[email protected]
Endpoint Type (Analog Line)
Port 1
FXS VWIC 2/1/1
Both MGCP and Skinny Client Control Protocol (SCCP) are master/slave protocols; the CUCM is the master server for both protocols. SCCP and MGCP devices cannot operate without CUCM:
■ SCCP IP phones communicate directly with CUCM for all call setup signaling.
■ MGCP gateways communicate directly with CUCM for all call setup signaling.
Figure 10-2 displays a call that was received over an MGCP gateway to an SCCP IP phone. The MGCP communication from the gateway is sent to the CUCM for call processing. CUCM performs digit analysis on the received digits, and the lookup results in an SCCP endpoint. CUCM sends information to the gateway, allowing the gateway endpoint to play a ringback tone to the calling party. CUCM also sends SCCP signaling to the Cisco IP Phone, indicating that there is an incoming call. When the destination Cisco IP Phone end user answers the phone, CUCM coordinates the communication of the media path between the Cisco IP Phone and the MGCP gateway. The voice bearer traffic from the gateway to the IP phone uses Real-Time Transfer Protocol (RTP). RTP uses an even port number in the UDP port range of 16,384 through 32,767.
Figure 10-2 MGCP Call Flow
CUCM
Figure 10-2 MGCP Call Flow
CUCM
MGCP Gateway Support
MGCP support in CUCM includes a wide range of analog and digital interfaces that can be used on several Cisco router and switch platforms. Tables 10-1, 10-2, and 10-3 list MGCP-supported analog and digital features.
CUCM allows the Cisco IOS MGCP gateway to pull its MGCP-related configuration from the Cisco TFTP server. This eliminates the need for manual MGCP gateway configuration.
CUCM also supports Q.931 backhauling. Q.931 backhauling is supported on ISDN PRI, BRI, and E1 using common channel signaling (CCS). The MGCP call agent (CUCM) takes control of the ISDN D channel. The gateway sends CUCM all Q.931 call setup and teardown traffic over TCP port 2428.
Table 10-1 lists supported MGCP hardware.
|
Gateway |
Supported Voice Hardware |
Remarks |
|
Cisco 3800 |
Analog FXS/FXO, T1 CAS (E&M Wink Start; Delay Dial only), T1/E1 PRI |
Beginning with Cisco IOS Release 12.3.11T |
|
Cisco 2800 |
Same as Cisco 3800 |
Beginning with Cisco IOS Release 12.3.8T4 |
|
Gateway |
Supported Voice Hardware |
Remarks |
|
Cisco 3700 |
Same as Cisco 3800 |
|
|
Cisco 3640 and 3660 |
Same as Cisco 3800 |
|
|
Cisco 2600/2600XM/V G200 |
Same as Cisco 3800 |
|
|
Cisco 1751 and 1760 |
Same as Cisco 3800 |
|
|
WS-X4604-GWY Module |
Same as Cisco 3800 |
|
|
Comm. Media Module (CMM) |
T1 CAS FXS, T1/E1 PRI, FXS |
|
|
WS-X6608-x1 Module and FXS Module WS-X6624 |
T1 CAS E&M, T1 CAS FXS, T1/E1 PRI, FXS with WS-6624 |
|
|
VG224 |
FXS only |
|
|
Cisco ATA 188 |
FXS only |
|
Gateway |
FXS |
Battery Reversal |
Analog DID |
CAMA 911 |
||
|
Cisco 3800 |
Yes |
Yes |
No |
Yes |
No |
No |
|
Cisco 2800 |
Yes |
Yes |
No |
Yes |
No |
No |
|
Cisco 3700 |
Yes |
Yes |
No |
Yes |
No |
No |
|
Cisco 3640 and 3660 |
Yes |
Yes |
No |
Yes |
No |
No |
|
Cisco 2600 and 2600XM |
Yes |
Yes |
No |
Yes |
No |
No |
|
VG200 |
Yes |
Yes |
No |
Yes |
No |
No |
|
Cisco 1751 and 1760 |
Yes |
Yes |
No |
Yes |
No |
No |
|
WS-X4604-GWY Module |
Yes |
Yes |
No |
No |
No |
No |
|
Communication Media Module (CMM) 24FXS |
Yes |
N/A |
N/A |
N/A |
N/A |
N/A |
|
FXS Module WS-X6624 |
Yes |
N/A |
N/A |
N/A |
N/A |
N/A |
|
VG224 |
Yes |
N/A |
N/A |
N/A |
N/A |
N/A |
|
Cisco ATA 188 |
Yes |
N/A |
N/A |
N/A |
N/A |
N/A |
Table 10-3 lists supported MGCP digital features.
|
Gateway |
BRI* |
TI CAS (E&M) |
T1 PRI |
T1 QSIG |
E1 PRI |
E1 QSIG |
|
Cisco 3800 |
12.4(2)T |
Yest |
Yest |
Yest |
Yest |
Yest |
|
Cisco 2800 |
12.4(2)T |
Yest |
Yest |
Yest |
Yest |
Yest |
|
Cisco 3700 |
12.4(2)T |
Yest |
Yest |
Yest |
Yest |
Yest |
|
Cisco 3640 and 3660 |
12.4(2)T |
Yest |
Yest |
Yest |
Yest |
Yest |
|
Cisco 2600 and 2600XM |
12.4(2)T |
Yest |
Yest |
Yest |
Yest |
Yest |
|
VG200 |
No |
Yes |
Yes |
Yes |
Yes |
Yes |
|
Cisco 1751 and 1760 |
12.3(14)T |
Yes |
Yes |
Yes |
Yes |
Yes |
|
WS-X4604-GWY Module |
No |
Yes |
Yes |
Yes |
Yes |
Yes |
|
Communication Media Module (CMM) 6T1/E1 |
N/A |
Yes |
Yes |
Yes |
Yes |
Yes |
|
WS-X6608-T1/E1 |
N/A |
Yes |
Yes |
Yes |
Yes |
Yes |
*Cisco IOS 12.4(2)T supports BRI MGCP with the following hardware: NM-HDV2, NM-HD-XX, and on-board HWIC slots. BRI MGCP is also supported on older Cisco IOS releases with NM-1V/2V hardware.
*Cisco IOS 12.4(2)T supports BRI MGCP with the following hardware: NM-HDV2, NM-HD-XX, and on-board HWIC slots. BRI MGCP is also supported on older Cisco IOS releases with NM-1V/2V hardware.
^AIM-VOICE-30 modules require Cisco IOS Release 12.2.13T.
Continue reading here: MGCP Configuration Server
Was this article helpful?