ABCs of videoconferencing
Pick the right client device, figure out LAN bandwidth requirements, nail down WAN links, then start conferencing.
If your company's travel budget has been slashed or if the recent terrorist attacks have made employees reluctant to fly, you may be considering videoconferencing as an alternative to face-to-face meetings.
Before you jump in, here's a comprehensive guide to enterprise-level videoconferencing that covers everything from bandwidth requirements to equipment options to deployment costs.
Audio primer: Videoconferencing
Get up to speed on the basic technology.
Currently there are three distinct categories of clients defined primarily by usage.
Types of client devices, bandwidth requirements, and network components for videoconferencing.
Videoconferencing can leverage the existing public telephone network, a private IP network or the Internet. The target bandwidth for interactive video communications is in the 300K to 400K bit/sec per stream range. This includes audio and video as well as control signaling.
The H.323 protocol does not require that two or more endpoints in a session send the same data rate they receive. A low-powered endpoint may only be able to encode at a rate of 100K bit/sec, but, because decoding is less processor-intensive, it could decode a 300K bit/sec videostream.
Nevertheless, in videoconferencing, bandwidth is assumed to be symmetrical. In full-duplex networks such as ISDN, Ethernet, ATM and time division multiplexed networks, capacity is expressed as bandwidth in one direction, though equal bandwidth is available for traffic in the opposite direction.
You need to estimate the number of simultaneous sessions your network needs to support, and figure out if your network has bandwidth end-to-end.
A T-1 offers 1.5M bit/sec in each direction and would be ample bandwidth for two 512K bit/sec or three 384K bit/sec videoconferences, depending on the amount of simultaneous traffic on the network. Also, make sure that you have 10/100 switched Ethernet throughout the LAN segments where videoconferencing traffic is expected.
Multipoint conference bandwidth (with which three or more locations can see and hear one another) is calculated separately from point-to-point sessions. Multipoint can be conducted in either IP or ISDN environments, and some conferencing units will support both network types.
Multipoint conferencing products may be software-based or accelerated with special hardware, and their configuration can produce different bandwidth consumption patterns as well as different user experiences. For example, when an endpoint is used to host a multipoint conference, the maximum bandwidth for any single participant is the bandwidth allocated to that host divided by the number of locations participating. When you need to have more than four locations on a call at the same time, network-based products are recommended.
If you decide that your IP network can't handle the additional traffic associated with live video sessions in a merged or converged network deployment, your options are to rely on circuit switched networks or to deploy additional IP bandwidth capacity.
The WAN connection
Approximately 80% of the group videoconferencing units installed today interface directly with ISDN. Less than 5% use ATM, and the remainder are on an IP net.
ISDN is recommended when:
If you use ISDN for transport and you want to add centralized user administration or system management, you can still install an Ethernet connection to each device and a management software package such as Polycom's Global Management System or Vcon's MXM on a server in the company's data center.
The limitations of ISDN (Basic Rate Interface or Primary Rate Interface) include:
Video calls on ISDN cannot be put on hold, cannot be forwarded (when no one answers, when the line is in use or for any other reason), and there has never been a “video mail box” on ISDN. Recording one side of an ISDN videoconference is possible using an analog VCR provided the appropriate interfaces exist on the local client system.
The IP option
Using proprietary technologies or H.323 standard-compliant endpoints, an IP network designed only for data can be modified to support business-quality videoconferencing services.
Where bandwidth is available, the IT manager would need to add and adjust a few components to provide a complete solution, or outsource the management to a third party such as WireOne's GlowPoint service or Sprint's IP videoconferencing services.
If the deployment is expected to have more than five or six systems, a centralized user and network administration console such as Polycom's Global Management System, RADVision's H.323 gatekeeper or Vcon's MXM is recommended.
Some companies are going a step further and designing an enterprise conferencing portal using technologies such as FVC's Click-to-Meet. While these packages differ in their features and functions, they are designed to perform address book management (an important issue when clients are set up behind a firewall and use network address translation), set performance metrics on a per-device or user basis, and can even reduce the risk of application data traffic degradation due to excessive bandwidth consumption.
Implementing quality of service (QoS) in a LAN helps to protect the integrity of service-sensitive applications without forklift upgrades. Most of the leading network equipment vendors already support common QoS standards, such as RSVP; they only need to be enabled by the network administrator.
You should also find out what your backbone provider uses for its QoS. If the protocol or scheme chosen for QoS in the local loop is not the same as that implemented in the backbone, the enterprise network needs to put QoS translation software in place for QoS requests to operate end-to-end during a videoconference.
Even when QoS protocols are in place, you may need additional network tuning to ensure that the video applications don't crowd out data applications. To avoid this, network managers should segment and manage bandwidth on each switch and router to limit the total, prioritized video traffic.
After provisioning appropriate bandwidth and QoS, other challenges remain. One of the biggest obstacles is getting real-time video traffic through firewalls. Since H.323-compliant applications use dynamically allocated sockets for audio, video and data channels, a firewall must be able to allow H.323 traffic through on an intelligent basis. The firewall must be either H.323-enabled with an H.323 proxy, or able to “snoop” on the control channel to determine which dynamic sockets are in use for H.323 sessions, and to allow traffic through only as long as the control channel is active.
Merging and emerging services
Since the very essence of videoconferencing is communications and most legacy systems are not on IP networks, the user is likely to encounter a situation where protocols need translation across different networks. When a videoconference needs to span both the ISDN and IP infrastructures, gateways are necessary.
RADVision is the leading manufacturer of videoconferencing gateways and offers a variety of form factors and densities to meet diverse network requirements.
Some companies have to share limited resources and want a reservation system to permit room or multipoint control unit (MCU) scheduling.
Endpoint and MCU vendors offer some scheduling tools that may meet your company's needs. Third-party products, such as Collaborative Systems' Orchestra, MagicSoft's VC Wizard and Global Scheduling Solutions' Global Schedule, have unique features.
When the videoconferencing basics are in place for group conferencing, you might consider a number of optimizations. For example, by enabling IP multicast and using intelligent clients, a network can efficiently support multiway meetings without adding an MCU.
If using IP multicasting to achieve a multipoint scenario, each client sends only one stream of packets to an IP multicast group and all participating machines receive the packets. In this scenario, bandwidth consumption is lower than when an endpoint or MCU sends out copies of the same packet to each of the receivers.
Another second-generation feature found in products such as Polycom's ViewStation FX is integration of videoconferencing with streaming media systems, enabling the broadcast of a videoconference from a coder/decoder to many remote viewers via a streaming media server or to archive a videoconference on a streaming media server for later review.
Although an exception to the rule today, large financial services companies that have integrated videoconferencing into their corporate cultures are beginning to deploy desktop videoconferencing capabilities. With Universal Serial Bus interfaces, setting up a videocamera takes only a few minutes, in contrast with earlier desktop products that required opening the PC and installing a card. Low-cost Webcams put all the computational load from compressing video and audio on the host computer. Optional hardware-accelerated cameras designed specifically for videoconferencing, such as the Polycom ViaVideo or Vcon Vigo, produce the best results.
How much does it cost?
Depending on the number of endpoints, the type of client and choice of networks, videoconferencing can cost as little as the price of a Webcam ($100) per seat to more than $15,000 per conference room.
To budget a videoconferencing deployment, break down the fixed acquisition costs from the recurring and usage-based costs. The exact fixed costs are going to depend on the number of systems and the features your users need. In general, systems provisioned for ISDN will also support IP, but IP-only systems tend to cost several hundred dollars to $1,000 less than ISDN systems because they have fewer components. Management software is sold according to site licenses from $250 per license to $40,000 or more for unlimited licenses. Complete enterprise conferencing portal environments suitable for large companies can exceed $100,000 per installation, depending on hardware and software components.
Another factor is the cost of installing the last mile. Basic Rate ISDN installation runs about $225 in most regions of the SBC territory, while other regions tend to be higher. The cost of installing a T-1 depends on the distance between your facility and the nearest central office.
Recurring costs are composed of the monthly cost of network access, network usage costs and, potentially, the salary for one or more technicians managing network provisioning, installations, room or conferencing system reservations, technical support and user training. The largest variable in this equation is the network usage costs.
ISDN usage charges vary but can be estimated for individual customers (one site) at 5 cents per minute per B channel. A 384K bit/sec videoconference will consume 6 B channels at a cost of approximately 30 cents per minute, or $18 per hour. Companies that negotiate their telecommunications rates with carriers for voice and video usually receive discounts on this rate.
ISPs also charge for capacity, though not by the minute. To calculate the costs of IP backbone services, multiply the data rate by the time. A 384K bit/sec call for one hour will generate nearly 1.4G bits of bandwidth. On a VPN the network usage costs are already fixed and the company will incur no additional charges.
Going with a managed service provider can be cost-effective for some regions and some companies. GlowPoint's Web site offers a calculator, and users can plug in the number of hours of usage per location and the average cost of ISDN service to obtain a cost estimate.
The costs of deploying videoconferencing are as variable as the networks and depend on the number of installations, features and choice of network. Cost of ownership runs about $15 per hour for a midsize enterprise. It's safe to predict that costs will continue to fall as more people get on the bandwagon. And, in the face of rising travel costs, getting a rapid return on your investment in videoconferencing is easier now than ever before.
Perey is president of Perey Research and Consulting in Placerville, Calif. She can be reached at firstname.lastname@example.org.
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Perey is also a member of the Network World Global Test Alliance, a cooperative of the premier reviewers in the network industry, each bringing to bear years of practical experience on every review. For more Test Alliance information, including what it takes to become a member, go to www.nwfusion.com/alliance.
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