---------------------------------------------------------------------------- The Florida SunFlash Multimedia: ISDN (6 of 6) SunFLASH Vol 40 #30 April 1992 ---------------------------------------------------------------------------- 6 ISDN Integrated Services Digital Network (ISDN) is a new service offered by many telephone companies that provides fast, high-capacity digital transmission of voice, data, still images and full-motion video over the worldwide telephone network. ISDN will soon be to wide area networking what Ethernet is to local area networking today. It will enable multimedia communication - voice, video, images and data combined - over the existing telephone network. ISDN will help workstation users integrate their telephone with workstation applications in a seamless way, increasing their productivity. In addition, ISDN will provide an alternate channel enabling customers to transmit information from one point to another in real-time at a reasonable cost. ISDN offers many times the speed of current analog modems, and twice the bandwidth of the leased lines commonly used today to carry video conferencing. ISDN Applications ISDN applications fall into two categories: o Basic applications in which ISDN replaces or enhances existing applications o New types of applications that integrate voice, images, video and data in ways that don't exist today Basic Applications of ISDN The basic application of ISDN is for wide area networking. When workstations come with an ISDN interface built in, just as they have an Ethernet interface today, your reach will not be limited just to the local network but will extend to the whole world. Some of the applications this basic capability enables are described in the following paragraphs. Replacement or Backup for Private, Leased, or Public Packet Switched Lines For most customers, the cost of an ISDN line is much less than that of a private line or leased line. For customers that can afford private lines, ISDN will provide a cost-effective alternative as a backup line. Most leased lines are 56 kilobits per second (Kbps), compared to ISDN speeds of up to 128 Kbps (aggregated) for basic rate ISDN. For customers that cannot afford the substantial fixed charges for leased lines, ISDN for the first time offers them equivalent bandwidth at a cost they can afford. The cost of ISDN will also be much less than public switched network access (X.25), especially in Japan and Europe. Telecommuting Working from home on a networked workstation will become a reality when ISDN becomes available at home. ISDN provides data transmission speeds that enable true client-server computing over a wide area network, making access from home practical. Workstations will require an ISDN terminal adapter (or an SBus card for SPARCstations) and software that allows TCP/IP (communication protocols used in the UNIX environment) over ISDN. Replacement of Data and Fax Modems Currently, 9600-baud modems are becoming a standard. However, the price range for such modems is $500-$1000. The price for ISDN adapters is currently in the $1000-$1500 range but they offer speeds that are about seven times greater than 9600-baud modems. New Applications of ISDN New applications made possible by ISDN technology can be discussed in three categories. These categories are not all-inclusive. Customers will find many more applications of the technology as it becomes widely available. Some of these applications are described in the following paragraphs. Telephone-Workstation Integration Telephones used in proprietary PBX systems currently provide functionality such as caller identification with a liquid crystal display (LCD). A workstation with a graphical user interface could provide a much more flexible and powerful display. This type of integration enables the following applications: o An automatic phone dialer linked with an address file or calendar application o A customizable answering machine application that can take messages or forward calls based on the identity of the caller o The integration of voice messaging (voicemail) with electronic mail Multimedia Communication/Collaboration A conference call between people at different locations that includes sharing each others' screens in a collaborative work environment will require point-to- point connections with real-time response. ISDN can enable this type of connection. Some of the applications in this category are: o Collaborative work environments. This could involve real-time screen-sharing between two or more people working on the same project. o Concurrent engineering. This would enable everyone involved in a project (including suppliers) access to shared work even if they are not connected to the same local area network. o Video conferencing. With proper compression/decompression, a reasonable quality video conference can be carried over the ISDN lines. For example, some of the video conferencing systems available today use two 56 Kbps switched lines, for 112 Kbps total. Vertical Applications There are certain market segments such as customer service, where computer users spend a lot of time on the phone. Any degree of automation that can integrate the phone and the computer will help improve service and increase efficiency. Some of the examples in this category are: o Customer service applications. ISDN's caller ID feature enables immediate access to the customer's records when a customer's call is received. o Technical support. A support person could easily look at a workstation screen and provide support remotely. o Voice response applications. o Intelligent operator terminals in telephone companies. Benefits of ISDN ISDN will benefit workstation users, system administrators, companies of all sizes, and the telephone company as well. o Workstation users will get better access speeds and higher transmission quality of voice and data. ISDN will make wide area networking and communications as easy as plugging a phone into the wall jack. It will also allow a viable telecommuting environment. Wide area networking will provide users with the functionality of today's local area network, but with the added benefit of access to people on other networks as well. o Telecommunication system administration can more easily accommodate changes when office moves occur. It will also reduce the network wiring requirements and maintenance costs. ISDN will make troubleshooting from remote locations easier. o Company benefits include reduced transmission costs resulting in enhanced employee productivity. There will be faster dial-up transmission at lower cost and higher profits in the long run. o For the telephone company, ISDN will reduce maintenance and upgrade costs and provide an increase in the data communication business for the telephone companies. These benefits will ultimately result in higher profitability. Key ISDN Concepts The following paragraphs describe some of the technical aspects of ISDN. Current Telephone Network In order to understand ISDN technology, you should first understand the current telephone network. Voice Call Routing Voice is analog in nature and so are most telephones today. When you make a call, your analog signal goes through the telephone company's central office (CO) switch which converts it to a digital signal. If it is a long-distance call, the switch routes the digital signal to an inter-exchange carrier (IEC) such as AT&T, US Sprint or MCI. The IEC then routes the call to the appropriate local central office which converts the digital signal back to an analog signal so that it can be used by the telephone on the receiving end. Data Call Routing Computers generate digital signals instead of analog signals, so two additional steps are required. A modem must convert the computer's digital signal into analog form before sending it to the telephone company's CO switch, and another modem must convert the analog signal back to digital so the receiving computer can understand it. In this process the data is converted between analog and digital forms at least four times in one transmission, thereby under-utilizing the network capacity. When voice is converted into digital form, a bit rate of 56 Kbps (kilobits per second) is often used to maintain the sound quality. Most modems today transmit data at 1200 or 2400 bps (with 9600 bps modems becoming more common). At 1200 bps, less than 2% of the 56 Kbps network capacity is used. ISDN Telephone Network Computer equipment is currently at a disadvantage because the telephone network was designed for voice. ISDN will remove this limitation, enabling companies and individuals to access a variety of multimedia services (voice, textual data, images, video) over a single international phone system serving as a global network. Integrated Services Digital Network (ISDN) is a worldwide public telecommunications network that will deliver a wide variety of data and voice transmission services. The first set of standards for ISDN were issued by the International Telecommunications Standards Organization (CCITT) in 1984. As ISDN becomes established globally, a variety of multimedia services (voice, textual data, images, video) can be supported over a single, homogeneous infrastructure. Digital communication will eventually prevail, resulting in enhanced quality and reduced costs of telecommunication. In addition, ISDN promises to make wide area networking as economical and accessible as local area networking is today. There are various types of ISDN that cater to different requirements. Unlike the current telephone network's in-band signalling, all ISDN services offer out-of- band signalling (signalling information and data are carried on different channels). This provides more flexibility in network operations and control. D Channels and B Channels There are two types of ISDN channels, D channels and B channels. o D Channel A D (or Delta) channel is a control channel. o B Channels B (or Bearer) channels are 64 Kbps clear channels for carrying data. Depending on the service offerings of the telephone companies, a number of B channels can be concatenated to provide higher bandwidths. BRI, PRI, and BISDN There are three types of ISDN, Basic Rate Interface (BRI), Primary Rate Interface (PRI), and Broadband ISDN (BISDN). o Basic Rate Interface (BRI) BRI is the interface that will eventually replace the current single-line telephones in residences and many businesses. BRI will be the standard interface to connect desktop devices such as telephones, fax machines and computers to the ISDN network. It normally provides two B channels and one D channel and is commonly referred to as a 2B+D interface. o Primary Rate Interface (PRI) PRI will become the standard interface between a PBX and a central office switch, or between two PBX switches. In the US and Japan, this service provides 23 B channels and one D channel (23B+D) with an aggregate rate of 1.544 Mbps. In Europe, the primary rate interface is 30B+D with an aggregate rate of 2.048 Mbps. These rates are different due to the requirement of maintaining compatibility with the existing digital systems in each country. Most phone companies in the US have applied to their regulatory agencies for rate approval for both BRI and PRI services. This means that ISDN will soon be available in most metropolitan areas in the US. o Broadband ISDN (BISDN) Broadband ISDN is the telephone companies' solution to the bandwidth limitations associated with BRI and PRI. As video and high-quality images become commonplace on desktops, their bandwidth requirements will exceed the capabilities of BRI and PRI. BISDN will offer a rates as high as 150 Mbps. However, BISDN is at least 2-3 years away from a trial stage in the USA. Signalling System #7 (SS7) For ISDN services to be useful, a user must be able to communicate to the rest of the world. SS7 is an international standard for common channel signalling that enables internetworking between the various ISDN exchanges. It is called "common channel signalling". The signalling information is sent on a separate, shared signalling channel. AT&T has been using a proprietary common channel signalling scheme, but is migrating its switches to SS7 to permit easy internetworking. Challenges ISDN's promise for integrating voice and data over a wide area network opens up possibilities for a universal network with a cost structure in line with current telephone service. ISDN does not require any change in our current wirings except for some minor additional investments in equipment. The US has been slow to implement ISDN so far, but the new aggressive plans published by telephone companies call for ISDN availability in all metropolitan areas by 1994. In contrast, ISDN is already available today in most of the European countries and in Japan. In fact, most of the developing countries are also migrating to ISDN. Japan, Australia, France, Germany, and Great Britain have ISDN available today for all businesses and many residential customers. Providing ISDN support as a standard feature will be a requirement for computer companies doing business in Europe and Japan. ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ For information send mail to info-sunflash@sunvice.East.Sun.COM. Subscription requests should be sent to sunflash-request@sunvice.East.Sun.COM. Archives are on solar.nova.edu, paris.cs.miami.edu, uunet.uu.net, src.doc.ic.ac.uk and ftp.adelaide.edu.au All prices, availability, and other statements relating to Sun or third party products are valid in the U.S. only. Please contact your local Sales Representative for details of pricing and product availability in your region. Descriptions of, or references to products or publications within SunFlash does not imply an endorsement of that product or publication by Sun Microsystems. John McLaughlin, SunFlash editor, flash@sunvice.East.Sun.COM. (305) 776-7770.