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A digital content channel requires a network infrastructure capable of delivering a variety of content to the end user. A typical channel requires servers for delivering Web pages, pushing content, streaming real-time video or audio, or providing online chat. The networks for channels also need to be scaleable to be able to service a large number of users on the Internet. This requires that the server technology being used is highly scaleable. The network must also have sufficient bandwidth to service the traffic that will be generated by a successful channel.

The Internet as seen from the home user is typically a modem connection into an Internet Service Provider (ISP). The ISP leases a T1 or larger line from a major carrier such as MCI* that actually provides an interface to the Internet backbone. The Internet consists of routers that store in its tables the actual route of the IP addresses going across it. These routers can handle a large amount of traffic but are the primary cause of the latency that a user encounters. During peak hours, this latency can exceed one second or more. And in some cases, latency increases when internet requests time out or packets are dropped.

When the user dials into an ISP, he or she may expect a full 28.8-Kbps connection. This speed is, of course, dependent on the capabilities of the ISP and the quality of the line connection. The actual speed of the connection may be lower in some cases. This connection is, of course, shared with a large number of users who connect through the T1 line. And then the backbone is shared among an even larger number of users.

The destinations for IP requests are servers that respond to the request for a particular packet. The large numbers of requests that come in can overwhelm any server. Any popular site can experience server busy messages, depending on the load currently displayed to the user. For channels, it is important that server technologies being used are scaleable. For channel developers, it is important to understand the limitations of the Internet to determine what rich multimedia data types can be realistically delivered over the Internet.

The consumer has a variety of options (in some cases) for connecting to the Internet. These options include 14.4- to 56.6-Kbps modems. New technologies are emerging that provide higher bandwidth for the end user. These technologies include cable modems, satellite and ADSL. All promise to deliver high-bandwidth pipes to the consumer that should ultimately benefit channels.

 

 

Figure F-1: Future Internet connections to the home

A majority of the modems currently connected to the Internet run at 28.8 Kbps. Newer 56-Kbps modems are widely available but require support at the ISP level. This effectively doubles the potential bandwidth for users dialing into the Internet over standard phone lines. The actual modem bandwidth is highly dependent on the quality of the phone connection and the availability of the higher speed modem at the ISP. Modem speeds can drop down to 19.2 Kbps or lower. The effective bandwidth can be somewhat lower, depending on network traffic at the time. Internet traffic at peak times during the day tends to occur in bursts and can further limit effective bandwidth.

Given a 28.8-Kbps modem connection, the user can receive very limited video and good-quality audio in real time over the Internet. Most Internet Web sites are limited to 2D graphics with text. Video is restricted to 160x120 with low frame rates. Audio is somewhat better, with quality that approaches what one gets with FM radio. This type of audio is good for live concerts and interviews with band members. This limitation can be overcome with push servers to increase the size of assets that are delivered, since this is done in the background. However, applications can benefit greatly with better quality audio, video, 3D and graphics delivered on storage media such as CD-ROM and DVD-ROM. Some emerging technologies may increase the bandwidth available on the Internet. ADSL is one of these higher bandwidth solutions becoming available for the home.

ADSL is an emerging technology that can provide anywhere from 1.5–9 Mbps downstream and 16–640 Kbps upstream when connected to the Internet. The connection speed of ADSL is dependent on the distance from the Telco. This limits the availability of ADSL to the home and the maximum speed that can be attained with ADSL. At 18,000 feet from the Telco, the maximum bandwidth is limited to 1.544 Mbps. The adoption of ADSL is currently not widespread, but it is a technology that is capable of providing fast access to the home, since it connects over standard twisted-pair telephone lines.

ADSL provides much larger bandwidth to the end user and can potentially deliver real-time MPEG1 and MPEG2 streams and virtually any high-quality audio compression schemes, such as AC3. This is as long as the high-bandwidth streams can be delivered across the Internet backbone and the infrastructure provided by the ISP. ISPs typically have T1 or T3 access to the Internet backbone shared by multiple users. It is highly unlikely that the ISP would dedicate the equivalent of one T1 line to deliver a stream of video to one end user. The ISP can provide multicast broadcasts, but the ISP is limited by the bandwidth available to the Internet. Private networks are being put in place to deliver multicast streams on the Internet, but their deployment is currently limited.

ADSL shows some promise for delivering high-bandwidth connections to the home. Of course, improvements in the capacity of the backbone, quality of service and ADSL equipment at the telephone company will make the availability of ADSL limited to certain areas in the short term. Cable modems are another technology that unlike ADSL already has connections to the home.

Cable modems have been in existence for several years, and available cable modems and head-end solutions are starting to mature. Cable modems use what is known as Hybrid Fiber Coax (HFC) to deliver high-bandwidth data. The cable modem can deliver up to 30 Mbps of downstream data to the end-user PC. Users share from 0.1–3 Mbps on the upstream link. Alternatively, the end user can utilize an existing modem connection to the Internet as an upstream link.

Cable modems require a head-end solution. The head end equipment resides at the cable company and provides the router, modulator, network management software and an upstream server switch. This head-end system is shared by thousands of users. Cable modems provide a large bandwidth to the home and allow for the potential delivery of good-quality MPEG2 video as well as a large amount of data. The main advantage of cable is the availability of connections to a large number of existing homes. The large bandwidth makes it a potential solution for delivering digital channels to the home.

The large number of cable operators across the country makes it difficult to deploy to all parts of the country simultaneously. The deployment of cable modems has been slowed because of the investment required by cable companies.

Satellite broadcasting is an emerging technology that holds great promise for the delivery of digital data. Its main advantage is that it can be delivered from one satellite system and reach a large number of users simultaneously. Investment in head-end equipment is cheaper, since a stream is broadcast from one satellite to every subscriber.

Satellite provides up to 27 Mbps on the downlink, with uplink being provided by the modem. A large amount of data can be delivered to the PC continuously. This is 1,000 times more bandwidth that can be delivered by a standard 28.8-Kbps modem. It is an ideal medium for delivering broadcast data channels that can be received by millions of users.

One example of a satellite connection is DirectPC*. It delivers 400 Kbps one way to the home. Upstream is done using a standard telephone modem with a speed of 33.6 Kbps. This provides Internet access with a higher bandwidth available on the downstream. DirectPC* is currently available to any home that can install a satellite and with a direct line of sight (no trees) to the satellite.

The advantage of satellite is that it can be sent data that would not have to travel over the Internet to arrive. It could be sent directly to the satellite head end and broadcast immediately to users. Satellite deployment is limited today but is growing rapidly.

Surfing the Internet at speeds of 1–6 Mbps seems unthinkable to most users. However, the speed of connection to the Internet is not always the determining factor of Internet delivery speed. The backbone limits the amount of data that can be effectively delivered online at any given time. The large amount of traffic is shared with every user on the Internet.

In addition, popular sites can be bogged downed with the common server-busy message. The main point is that connecting to the Internet at 1 Mbps or higher will not guarantee that type of service. Traveling across the backbone limits the effective bandwidth at which users can surf the Internet. Some T1 connections have the throughput of a 28.8-Kbps modem, depending on Internet traffic.

The bandwidth available for delivery of rich multimedia across the Internet will be limited in the short term. To deliver rich multimedia and exciting channels to the user requires the use of CD-ROM, DVD-ROM or push technology. The future holds great promise for delivering rich multimedia channels with the wider availability of ADSL, cable modems and satellite. The key for digital content channel developers is to provide scaleable solutions that take advantage of higher bandwidths. Appendix B covers live streaming of audio and video to enhance a channel, despite current limitations in bandwidth. Several scaleable solutions are available that take advantage of increasing bandwidth and richer data types.

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© 1997 Intel Corporation. All rights reserved.

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