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This chapter provides a general overview of the Cisco IP/VC 3500 Series product and architecture and describes the physical features and functionality of the Multipoint Control Unit (MCU).
Videoconferencing is helping organizations make the transition to an Internet-driven world with instant worldwide connectivity. Spurred by changes in communications technology, low-cost bandwidth, plus continuous improvements in hardware and performance, videoconferencing solutions provide large and small enterprises, government institutions, and educational environments with the tools they need to be more productive, to make decisions faster, to train and educate more effectively, and to save time and avoid the burden of travel.
The Cisco IP/VC 3500 Series product family is Cisco's videoconferencing solution. It comprises several products that are developed for enterprises and service providers who want a reliable and easy to manage network infrastructure for videoconferencing applications deployment. Cisco videoconferencing products enable video applications over IP networks, and integrate legacy H.320 system, thus protecting enterprises' original investment in videoconferencing.
H.323 is the International Telecommunications Union (ITU) standard for real-time multimedia communications and conferencing over packet-based (IP) networks. Sending videoconferences over standard ISDN lines is expensive and prone to connectivity problems. Because of specialized, dedicated equipment needs, ISDN-based videoconferencing is often restricted to special sites and rooms. Network-based H.323 videoconferencing is the next-generation standard. H.323 is more cost-effective, offering greater flexibility and scalability: wherever there is a LAN connection, H.323 videoconferencing equipment will operate.
The H.323 specification defines a number of new network components that interoperate with other standards-compliant endpoints and networks by virtue of an H.323/H.32X gateway.
Following are the network components defined by the H.323 standard:
The Cisco IP/V 3500 Series consists of the following products:
The Cisco IP/VC 3510 MCU includes an MCU and a Gatekeeper integrated in one box. The MCU can also be used with an external gatekeeper.
The MCU is designed to have a simple user interface and to allow conferencing with H.323 and non-H.323 clients (H.320, POTS as so on) via gateways. There is no need for a per-conference configuration.
The MCU enables voice only and multimedia conference calls between H.323 entities and non-H.323 entities. Non-H.323 devices such as telephones orH.320 terminals can join the conference via a gateway.
The MCU supports LAN and WAN terminals that can send and receive video streams, as well as those that can only receive video streams. This means that terminals without a video camera or video capturing capabilities can participate in a conference as "voice only" participants while benefiting from seeing the other participants.
The MCU version 1.5 lets you stack up to four MCUs, significantly increasing the number of simultaneous calls. This is achieved by configuring one unit as an MCU Distributed and the other units as MP Dedicated. The unit configured as an MCU Distributed performs the control and management functions while the MPs provide the extra ports. You only have to define services for the unit configured as the MCU Distributed, let this unit know which are the MPs available and the MCU does all the necessary management and control.
The MCU 5 allows you to cascade two or more conferences managed by separate MCUs to create one unified conference with multiple participants. Participants in a cascaded conference seamlessly exchange audio and video and are not aware of the cascaded nature of the conference.
Cascading can substantially increase the total number of participants per conference. For example, a single MCU supports up to 15 participants in a 128 kbps (video bit rate) videoconference; cascading two MCUs can increase the total number of participants up to 28.
Cascading MCUs creates a distributed environment in which the use of network bandwidth resources is optimized. When terminals want to join a conference managed by an MCU on another network segment, each terminal connects directly to the MCU, congesting the connecting router with multiple video and audio streams. If, however, the remote terminals join a conference managed by an MCU on their network segment, and this MCU joins the conference managed by the remote MCU, only one video and audio stream travels between the network segments, reducing network bandwidth usage and delay.
Cascading can significantly reduce communication costs between remote networks connected through Gateways. You only need one telephone line, for each Gateway, to connect multiple participants to a remote conference.
In a cascaded conference, the processing resources required by the MCU are distributed between the participating MCUs.
The number of conferences you can unite into one conference depends on the bandwidth available on the LAN. Connecting each MCU unit to a separate network segment can improve the capacity and prevent videoconferencing congestion on one particular network segment.
The MCU includes the following features:
The MCU is built in a low-profile unit designed to comfortably fit in the cabinet of your H.320 video conferencing system or in a 19-inch rack.
The front panel contains LEDs and a serial port, as shown in Figure 1-1. The LEDs the MCU features include:
| Status of LED | CPU load range |
|---|---|
Not illuminated | Load in range 0-3% |
One flashed LED | Load in range 3-20% |
One illuminated LED | Load in range 20-40% |
Two illuminated LEDs | Load in range 40-60% |
Three illuminated LEDs | Load in range 60-80% |
Four illuminated LEDs | Load in range 80-100% |
The asynchronous EIA/TIA-232 serial port connects either to a terminal or to a modem.
The rear panel contains a single LAN port. The LAN port is a 10/100BaseT, IEEE 802.3 Ethernet connections. Figure 1-2 shows the MCU rear panel.
Posted: Tue Nov 16 15:08:25 PST 1999
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