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This chapter describes how to dial videoconference calls involving a room system connected to the LAN with a Cisco IP/VC 3530 VTA. Calls can be initiated by the room system user or the room system can be a call recipient. In either case, the caller must dial appropriately to ensure that the call is successful. The topics in this chapter include the following:
H.323 is a videoconferencing protocol for an IP network. To place a call, the call initiator specifies the path the call is to take on the IP network in the dial string. Several H.323 components can be in the path, including following:
Each H.323 component is associated with at least one dial number. Terminals and VTAs have E.164 addresses (phone numbers from the local phone company can be used as E.164 addresses). MCUs, gateways and H.323 proxies are associated with service prefixes. (Gateways, which connect to an outside telephone line, also have telephone number that are used for incoming calls.) Gatekeepers are assigned zone prefixes. Phone numbers, service prefixes, and zone prefixes are inserted into the dial string to specify the call recipient or recipients and the services required from components to process the videoconference call.
Service prefixes convey information about how the call is to be processed. The system administrator creates service prefixes and assigns them when configuring components that provide services. MCUs provide services for multiparty videoconferences; gateways provide services for WAN calls. The system administrator defines the parameters for such services and assigns each a service prefix. An MCU or gateway can have several service prefixes. Proxy can be used for network security and QoS.
H.323 components must register with a gatekeeper to place, receive, and process videoconference calls. Each gatekeeper and the components that register with it comprise a gatekeeper zone. The gatekeeper manages network traffic in the zone. Except for some point-to-point calls, all videoconference calls including calls from other zones go through the gatekeeper. To facilitate dialing or to restrict access, the system administrator can assign gatekeepers a zone prefix. A zone prefix acts like a telephone area code. A caller in a remote zone appends the zone prefix to the recipient number in the dial string. The zone prefix is used by the processing gatekeeper to determine where the recipient is located.
Many factors can shape a videoconference call. A call can have multiple participants, require a specific bandwidth, be between zones, and have other factors. How the call is dialed depends on the call factors and the services that are available. Generally, the dial string will reflect the components in the dial path. Some common dial paths are as follows:
See your system administrator for a list of the components and services used in your videoconference environment.
The role of the VTA is to make an H.320 room system appear as an H.323 terminal on the LAN. The VTA provides the room system with an IP address, an alias, protocol translation, registration with a gatekeeper, and protocol translation. These items allow the room system to place and receive calls as an H.323 terminal. However, the room system retains one aspect of H.320: It requires the fixed bandwidths associated with circuit-switched network calls. To accommodate this requirement, the VTA allows the administrator to set a default bandwidth for outgoing calls and a default bandwidth for incoming calls. All outgoing and incoming calls must use the default bandwidth unless the caller specifies a different bandwidth using the predefined VTA prefixes and suffixes. Table 6-1 shows the prefixes the room system user is to dial for calls that require a different bandwidth than the VTA default bandwidth. Table 6-2 shows the suffixes the user calling the room system is to append to the room system number when a different bandwidth than the VTA default bandwidth is required. Subsequent sections give examples of how to dial outgoing and incoming VTA calls using the default bandwidth and the default bandwidth override.
| Bandwidth | VTA Service Prefix |
|---|---|
2 x 64 kbps (2B) | #00 |
128 kbps | #10 |
256 kbps | #20 |
384 kbps | #30 |
768 kbps | #70 |
2 x 56 kbps (2B) (restricted) | #01 |
112 kbps (restricted) | #11 |
224 kbps (restricted) | #21 |
336 kbps (restricted) | #31 |
672 kbps (restricted) | #71 |
| Bandwidth | VTA Service Suffixes |
|---|---|
2 x 64 kbps (2B) | 00 |
128 kbps | 10 |
256 kbps | 20 |
384 kbps | 30 |
768 kbps | 70 |
2 x 56 kbps (2B) (restricted) | 01 |
112 kbps (restricted) | 11 |
224 kbps (restricted) | 21 |
336 kbps (restricted | 31 |
672 kbps (restricted) | 71 |
This section describes how to dial calls between the room system and a terminal in the same zone. The call path is terminal-terminal. For such a call, the two terminals would normally negotiate a common bandwidth. However, the VTA is configured with nonnegotiable outgoing and incoming default bandwidths that the other terminal must agree to use. The call initiator can specify an alternative VTA bandwidth for the call by inserting a VTA prefix or suffix in the dial string.
Examples 6-1 through 6-4 describe how to dial calls using the default VTA bandwidth and how to dial calls that change the VTA bandwidth. Example 6-1 describes how the room system user dials a call using the default VTA bandwidth. Example 6-2 describes how a terminal user dials the room system using the default VTA bandwidth. Example 6-3 describes how the room system user dials a call using an alternative VTA bandwidth. Example 6-4 describes how a terminal user dials the room system using an alternative VTA bandwidth.
The dialing parameters used for these examples are as follows:
To place a call to the Terminal 1 using the default bandwidth, the room system user dials the Terminal 1 E.164 address: 5552.
To place a call to the room system using the default bandwidth, the Terminal 1 user dials the room system E.164 address: 5551.
To place a 128 Kbps call to Terminal 1, the room system user dials the appropriate VTA prefix and the Terminal 1 E.164 address: #105552.
To place a 128 Kbps call to the room system, the Terminal 1 user dials the room system E.164 address and the appropriate VTA suffix: 555110
This section describes how to dial MCU videoconference calls that include a VTA/room system. The call path is terminal-MCU-terminal. For such calls, the MCU negotiates a common bandwidth before completing the call. If the bandwidth required is other than the default VTA bandwidth, the caller must specify an alternative VTA bandwidth in the dial string. This section describes how to dial calls using the default VTA bandwidth and how to dial calls that change the VTA bandwidth.
Examples 6-5 through 6-8 describe how to dial calls that involve an MCU. Example 6-5 describes how the room system user dials an MCU videoconference call using the default VTA bandwidth. Example 6-6 describes how to dial an MCU videoconference call into the room system using the default VTA bandwidth. Example 6-7 describes how the room system user dials an MCU videoconference call using an alternative VTA bandwidth. Example 6-8 describes how to dial an MCU videoconference call into the room system using an alternative VTA bandwidth.
The dialing parameters used for the examples are as follows:
To initiate an MCU videoconference call to Terminal 1 and Terminal 2 using the default bandwidth, the room system user dials the MCU serve prefix, the conference ID, and both terminal E.164 addresses: 628321**5552**5553.
To invite the room system and Terminal 2 to an MCU videoconference call using the default bandwidth, the Terminal 1 user dials the MCU serve prefix, the conference ID, and the room system and Terminal 2
E.164 addresses: 628321**5551**5553.
To initiate a 128 Kbps MCU videoconference call to Terminal 1 and
Terminal 2, the room system user dials the appropriate VTA prefix, the MCU serve prefix, the conference ID, and both terminal E.164 addresses: #10628321**5552**5553.
To initiate a 128 Kbps MCU videoconference call to the room system and Terminal 2, the Terminal 1 user dials the MCU serve prefix, the conference ID, the room system VTA E.164 address. the appropriate VTA suffix, and the Terminal 2 E.164 address: 628321**555110**5553
This section describes how to dial videoconference calls involving a VTA/room system and a WAN terminal. The call path is H.323 terminal-gateway-H.320 terminal or H.320 terminal-gateway-H.323 terminal. For such calls, the VTA bandwidth must match the bandwidth the gateway uses for the call. If the bandwidth required is other than the default VTA bandwidth, the caller must specify an alternative VTA bandwidth in the dial string. This section describes how to dial calls using the default VTA bandwidth and how to dial calls that change the VTA bandwidth.
Examples 6-9 through 6-13 describe how to dial calls that involve a gateway. Example 6-9 describes how the room system user dials an outgoing call to a WAN terminal using the default bandwidth. Example 6-10 describes how the WAN terminal user dials a call to the room system using the default VTA bandwidth. Example 6-11 describes how the room system user dials an outgoing call to a WAN terminal using an alternative VTA bandwidth. Example 6-12 describes how the WAN terminal user dials to the room system using an alternative VTA bandwidth. Example 6-13 describes how the room system user dials a call to a WAN terminal that must go through an access device such as a PBX or IMUX.
The dialing parameters used for these examples are as follows:
To initiate a call to WAN Terminal 1 using the default bandwidth, the room system user dials the gateway service prefix and the WAN terminal telephone number: 955551212.
To call the VTA/room system using the default bandwidth, the WAN Terminal 1 user dials the gateway telephone number and after the IVR inquiry, the caller dials the room system E.164 address: 9000000 (IVR intercepts) 5551.
To initiate a 128 Kbps call to WAN Terminal 1, the room system user dials the appropriate VTA prefix, the gateway service prefix, and the WAN terminal telephone number: #10935551212.
To initiate a 128 Kbps call to the room system, the WAN Terminal 1 user dials the gateway telephone number and after the IVR inquiry, the caller dials the room system E.164 address and the appropriate VTA suffix: 9000000 (IVR intercepts) 555110.
If the gateway is connected to a PBX or IMUX or other device that requires an access code for dialing, you must insert the access code in the dial string in front of the recipient number. The room system user dials the gateway service prefix, the outgoing access (PBX) prefix, and the Terminal 1 telephone number: 9595551212
This section describes how to dial calls between the room system and a terminal in a different zone that uses a zone prefix. The call path is terminal-terminal. This call requires that the zone prefix of the remote terminal be inserted in the dial string. The two terminals must settle on using the VTA bandwidth. The caller can specify an alternative to the VTA default bandwidth in advance by inserting a VTA prefix or suffix in the dial string. The prefix or suffix changes the VTA bandwidth for the call. This section describe how to dial calls using the default VTA bandwidth and how to dial calls that change the VTA bandwidth.
Examples 6-14 through 6-17 describe how to dial calls to other zones. Example 6-14 describes how the room system dials a terminal in another zone using the default VTA bandwidth. Example 6-15 describes how a terminal in another zone dials the room system using the default VTA bandwidth. Example 6-16 describes how the room system dials a terminal in another zone using an alternative VTA bandwidth. Example 6-17 describes how a terminal in another zone dials the room system using an alternative VTA bandwidth.
The dialing parameters used for these examples are as follows:
To place an interzone call to Terminal 1 using the default VTA bandwidth, the room system user dials the Terminal 1 zone prefix and E.164 address: 1105552.
To place an interzone call to the room system using the default VTA bandwidth, the Terminal 1 user dials the room system zone prefix and E.164 address: 1005551.
To place an interzone 128 Kbps call to Terminal 1, the room system user dials the appropriate VTA prefix and the Terminal 1 zone prefix and E.164 address: #101105552.
To place an interzone 128 Kbps call to the room system, the Terminal 1 user dials the room system zone prefix, the room system E.164 address, and the appropriate VTA suffix: 100555110.
Posted: Mon Jun 5 13:35:28 PDT 2000
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