BUILDING BROADBAND NETWORKS phần 2 pot

FIGURE 1.6 The addition of a video server and array to an in-place ISDN network to support additional applications. Ethernet Ethernet Primary Rate Interface T1 ISDN Router Primary Rate Interface T1 Router Array Video Server 0889Ch01Frame Page 16 Wednesday, April 17, 2002 3:06 PM © 2002 by CRC Press LLC for enabling multimedia services via LANs (Local Area Networks) based on tech- nologies such as ISDN that do not provision QoS (Quality of Service) guarantees. ITU-T H.323-compliant terminals can support any combination of data, video, and voice traffic ranging from a single person-to-person voice-only call to multiparty multimedia interactive videoconferences. Moreover, the ITU-T H.323 Recommendation describes packet telephony archi- tecture and protocols that facilitate call signaling, call management, and call control. Compression and decompression algorithms and functions supported by the ITU-T H.323 Recommendation are also clarified in the ITU-T G.711 and ITU-T G.729 Recommendations. ITU-T H.323 services support RTP/RTCP (Real-Time Protocol/Real-Time Con- trol Protocol) for video and audio signal management, synchronization of video and audio streams, and transmission of real-time content. H.323-compatible services work in concert with RSVP (Resource Reservation Protocol) for provisioning ded- icated bandwidth to specified applications. The ITU-T H.323 Recommendation establishes a foundation for multicast ser- vices and bandwidth management to enable seamless traffic flows. In addition, the ITU-T H.323 Recommendation establishes a framework for enabling point-to-point, point-to-multipoint, and multipoint-to-multipoint videoconferences that function independently of in-place network operating systems and hardware configurations. ITU-T H.323-compliant solutions support tele-education, room-based and desktop videoconferencing, workgroup computing, electronic whiteboarding applications, IP telephony or voice-over-IP (VoIP), and interactive teleshopping services. 1.11.1.4 ITU-T T.120 Recommendation The ITU-T T.120 Recommendation provisions a scalable and extendible framework for multipoint data communications services that operate in interactive multimedia videoconferencing environments. This Recommendation also complements the ITU- T H.323 Recommendation and enables streaming voice and video transmission and multimedia applications such as videoconferences, teleseminars, teleworkshops, teletraining sessions, and simulations. In addition, the ITU-T T.120 Recommendation describes procedures for distributing IP multicasts; defines methods for secure trans- missions that operate in concert with ISDN, PSTN, ATM, and Frame Relay (FR) solutions; and specifies procedures for data and file exchange and transmission of still images. 1.11.1.5 ITU-T I-Series of Recommendations The ITU-T I.100-Series of Recommendations clarify fundamental ISDN principles and concepts. The ITU-T I.200-Series of Recommendations reference telecommu- nications services supported by ISDN. The ITU-T I.300-Series of Recommendations describes ISDN-based network functions, performance objectives, network proto- cols, and numbering and addressing principles. The ITU-T I.400-Series of Recom- mendations indicates attributes of ISDN User-to-Network Interfaces (UNIs). 0889Ch01Frame Page 17 Wednesday, April 17, 2002 3:06 PM © 2002 by CRC Press LLC The ITU-T I-Series of Recommendations also refers to Recommendations in the ITU-T V-Series, the ITU-T G-Series, and the ITU-T Q-Series that affect ISDN deployment. The ITU-T V-Series of Recommendations address issues associated with the provision of data communications and message handling services via the PSTN. The ITU-T G-Series of Recommendations clarifies processes relating to telephone connections and transmission systems. The ITU-T Q-Series of Recom- mendations specifies switching and signaling functions. 1.11.2 EUROPEAN ISDN USERS FORUM (EIUF) Regarded as the counterpart to the North American ISDN Users Forum, the European ISDN Users Forum (EIUF) encourages utilization of standardized EuroISDN imple- mentations by every member state in the European Union. EuroISDN offers BRI (Basic Rate Interface) and PRI (Primary Rate Interface) services, and supports supplementary applications that include caller ID, direct dialing, and terminal portability. EuroISDN also facilitates utilization of standardized network services and applications. Prior to EuroISDN implementation, proprietary European ISDN installations were incapable of supporting interoperable applications and transborder services. The European ISDN Users Forum (EIUF) encourages EuroISDN deployment throughout member states in the European Union. Created by the European Com- mission (EC) in 1990, the EIUF establishes testbeds for assessment of EuroISDN applications and services prior to full-scale implementation. EIUF also sponsors the BIRD (Better Infrastructure for Rural Development) initiative. This project demon- strates the economic and practical value of providing EuroISDN services in remote communities. EIUF works in concert with the European Telecommunications Stan- dards Institute (ETSI) in fostering implementation of EuroISDN-compliant products and services. 1.12 ISDN SERVICE ENHANCEMENTS ISDN is no longer regarded as a universal network solution. However, ISDN tech- nology continues to overcome physical and electrical local loop impairments, thereby enabling additional bandwidth capacity for accessing multimedia services at the customer premise. To encourage widespread ISDN utilization, vendors, standards organizations, and user groups promote routine deployment of AO/DI (Always On/Dynamic ISDN), CPE (Customer Premise Equipment) Diagnostics, and ISI (Initialization Simplification Initiative) service enhancements. 1.12.1 ALWAYS ON/DYNAMIC ISDN (AO/DI) 1.12.1.1 AO/DI Functions Always On/Dynamic ISDN (AO/DI) refers to network applications that utilize the ISDN D (Delta) Channel for X.25 packet data service and maintain always-on connectivity between the communications carrier and the ISDN subscriber. With an 0889Ch01Frame Page 18 Wednesday, April 17, 2002 3:06 PM © 2002 by CRC Press LLC AO/DI constant virtual connection, ISDN enables low-bandwidth transmissions at speeds up to 9.6 Kbps. When additional bandwidth is required to support information access and deliv- ery, AO/DI automatically provisions use of the B (Bearer) Channel to support network operations at 64 Kbps. With two B Channels, ISDN enables rates reaching 128 Kbps without compression and rates up to 512 Kbps with compression. When extra bandwidth is no longer required, one or both of the B Channels are dropped from the connection. The D Channel remains in place for packet-switched services. 1.12.1.2 AO/DI Supporters In the United States, AO/DI implementations are supported by ATF (Access Technol- ogies Forum) members that include Ascend, Cisco Systems, 3Com, and Microsoft. National ISDN Council participants such as Ameritech, Verizon, BellSouth, and SBC (Southwestern Bell and Pacific Bell) endorse AO/DI functions as well. Participants in the European AO/DI Interest Group include Deutsche Telekom, France Telecom, Swiss Telecom, TeleDanmark, BT (British Telecom), Telia, and Telenor. Organized in 1999, the European AO/DI Interest Group participates in the Global ISDN Industry Forum (GIIF). The GIIF promotes EuroISDN implementation by each member state in the European Union. 1.12.2 CUSTOMER PREMISE EQUIPMENT (CPE) DIAGNOSTICS CPE (Customer Premise Equipment) Diagnostics is a program for monitoring ISDN operations in subscriber equipment. CPE loopback, fault management, and state management tests aid in the identification and correction of equipment problems at the subscriber premise that adversely impact ISDN performance. 1.12.3 INITIALIZATION SIMPLIFICATION INITIATIVE (ISI) To facilitate ISDN implementation, the Initialization Simplification Initiative (ISI) provides mechanisms for automating ISDN installation procedures. A component of the ISI, autoSPID (Automatic Service Profile Identifier) enables automatic SPID detection by the communications carrier. AutoSPID eliminates the tedious and time- consuming process of providing detailed ISDN information by the subscriber to the communications carrier. Generic SPIDs are also in development to further streamline the initialization process. 1.13 ISDN MARKETPLACE Regional ISDN communications providers and interexchange carriers in the United States include AT&T, Ameritech, Verizon, BellSouth, GTE, SBC, Sprint, Southwest- ern Bell, and U.S. West. ISDN is available worldwide in countries that include the United Kingdom, Germany, Italy, Canada, France, Switzerland, the Netherlands, Israel, New Zealand, Australia, Indonesia, and Japan. (See Figure 1.7.) 0889Ch01Frame Page 19 Wednesday, April 17, 2002 3:06 PM © 2002 by CRC Press LLC FIGURE 1.7 A NSP (Network Service Provider) ISDN solution provisioning data center, proxy-caching, and security services for campus and SOHO subscribers. Supports remote access via a network hub/modem bank. T1 or BRI SNMP Manager distributed T1s Frame Relay PSTN Analog Data Center Sniffer Server monitoring/analysis Network Management Campus User Home User Modem Network Hub/ Modem Bank Control Interface Security Server ISDN Internet Proxy/Caching Server Analog Modem Analog Laptop with internal modem Mobile User 0889Ch01Frame Page 20 Wednesday, April 17, 2002 3:06 PM © 2002 by CRC Press LLC 1.13.1 SIEMENS Available from Siemens, the Optiset series of ISDN desktop terminals is equipped with snap-in Terminal Adapter (TA) modules for interlinking multiple analog devices. Optiset ISDN desktop terminals also support a TA for MPD (Multi-Purpose Data) to facilitate access to Web resources at rates up to 115.2 Kbps. In addition to provisioning cost-effective ISDN services, the Optiset series of desktop terminals streamlines the ISDN implementation process at the customer premise by eliminating the need for every ISDN device to be equipped with an interface and an application- specific TA. 1.13.2 TELCORDIA TECHNOLOGIES As a service to ISDN equipment manufacturers, Telcordia conducts a series of tests to verify the capabilities of standards-compliant ISDN customer premise devices such as modems, phones, multiport LAN bridges or routers, and TAs and software products. 1.14 ISDN COMPETITOR TECHNOLOGIES 1.14.1 B ROADBAND RESIDENTIAL ACCESS SOLUTIONS Demand for fast access to the Web contributes to the popularity of wireline and wireless broadband residential access solutions based on cable modem, LMDS (Local Multipoint Distribution System), MMDS (Multichannel Multipoint Distribution System), and DSL technologies. As with ISDN implementations, these competitor solutions provide dependable connections to voice, video, and data services via the local loop or the first mile between the subscriber premise and the local telephone exchange. 1.14.2 N-ISDN (NARROWBAND-ISDN) AND B-ISDN (B ROADBAND-ISDN) INSTALLATIONS ISDN is the core N-ISDN (Narrowband-ISDN) technology. ATM is the core B-ISDN technology. In comparison to ATM implementations, ISDN deployments are limited in enabling access to high-performance Web-based multimedia applications. More- over, ISDN is viewed as an interim step in the evolution to multi-service, high-speed, and high-capacity boradband networks. ISDN is also regarded as an outmoded network technology without much promise for the future. Nonetheless, as demonstrated by the initiatives that follow, ISDN solutions continue to support current and emergent applications in sectors that include edu- cation, medicine, and business. ISDN videoconferences interlink geographically dispersed individuals in virtual classes for enabling interactive tele-instruction, tele- training sessions, and telecollaborative workgroup activities in public and private K–12 (Kindergarten through Grade 12) schools and post-secondary institutions. Moreover, ISDN technology also supports teleconsultations, telesurgery, and virtual grand rounds in the field of telemedicine. 0889Ch01Frame Page 21 Wednesday, April 17, 2002 3:06 PM © 2002 by CRC Press LLC 1.15 UNITED STATES (U.S.) ISDN TELE-EDUCATION INITIATIVES The Federal Communications Commission (FCC) in 1997 encouraged renewed interest in ISDN implementation in the educational sector with the endorsement of the E-Rate (Education-Rate) program. The E-Rate program enables K–12 public and private schools and libraries following federal guidelines to receive significant discounts on telecommunications equipment, services, and deployments. Despite the soaring popularity and availability of broadband networking solutions, ISDN continues to accommodate a diverse range of tele-education requirements. ISDN facilitates implementation of innovative networking configurations such as virtual schools, virtual libraries, virtual universities, and virtual communities. In school and university venues, ISDN telecommuting initiatives enable institutional administrators and staff to effectively balance work and home responsibilities. Because ISDN deploy- ments also support flexible class scheduling, telecollaboration among peers, telemen- toring after class hours and on weekends, and Web exploration, students and faculty benefit from ISDN solutions as well. In addition, ISDN distance education implemen- tations foster collaborative teleprojects between schools, school districts, and post- secondary institutions such as community colleges, four-year colleges, and universities. The following national and international initiatives demonstrate ISDN capabil- ities in enabling communications between students, subject experts, tutors, teachers, and administrators. These deployments also illustrate ISDN functionality in fostering development of global classrooms. Capabilities of ISDN videoconferencing in pro- moting student achievement, professional development, and curricular enrichment are demonstrated in these initiatives as well. As noted, the appeal of ISDN is its ability to optimize capabilities of in-place twisted copper pair wiring that also supports PSTN services. By enabling video, still image, audio, and data transmission via twisted copper pair connections, ISDN dependably fosters access to tele-education applications such as desktop videocon- ferencing and Web browsing via the local loop. 1.15.1 UNITED STATES GOVERNMENT 1.15.1.1 U.S. Department of Agriculture (USDA) Rural Utilities Services (RUS) Tele-education applications and programs sponsored by the U.S. Department of Agriculture (USDA) Rural Utilities Services (RUS) enable rural residents to access Web resources in libraries, museums, training centers, and vocational schools throughout the country via technologies that include ISDN. ISDN distance learning projects supported by the USDA RUS provision access to K–12 activities and enrichment teleclasses, vocational teletraining sessions, and college degree and adult education telecourses and teleworkshops. 1.15.2 ALABAMA 1.15.2.1 Huntsville School System ISDN facilitates a variety of administrative functions in the telelearning environment, including physical security and video surveillance. At the Huntsville School System, 0889Ch01Frame Page 22 Wednesday, April 17, 2002 3:06 PM © 2002 by CRC Press LLC an ISDN configuration supports transmission of video images from remote cameras at more than 40 public schools to a centralized facility for review by system personnel monitoring the safety of the campus community and the security of on-site facilities. 1.15.3 CALIFORNIA 1.15.3.1 Statewide Tele-education Initiative In 1994, Pacific Bell, now known as SBC Communications, initiated a $100 million program called Education First to promote the installation of four ISDN lines in every public school, library, and community college in the State of California. ISDN services were designed to enable voice, video, and data distribution, and thereby support curricular enhancement and enrichment. After providing free installation of ISDN lines and service for one year, Pacific Bell supported a flat-rate pricing plan for ISDN utilization by Education First sites. Pacific Bell also provisioned PRI services in larger library systems and school districts. Discontinued in the late 1990s, the Education First Program helped teachers, librarians, principals, and administrators effectively use the in-place ISDN telecom- munications infrastructure in fostering access to tele-education applications. To facilitate effective videoconferencing deployment, the Education First Program sup- ported Web access to ISDN videoconferencing resources, tutorials, and teaching guides. In addition, the Education First Program provided Web links to instructional strategies for helping librarians and educators plan, organize, conduct, and evaluate ISDN videoconferences. Schools, libraries, community colleges, and community organizations throughout California that used ISDN videoconferences for tele-edu- cation projects were also identified. Although the Education First Program was terminated, schools and school districts throughout California continue to use ISDN solutions. As an example, the Colton, Chico, Fresno, San Francisco, and Santa Ana Unified School Districts implement ISDN solutions for enabling access to teleclassroom activities, Web resources, and interactive tele-instruction programs, and supporting administrative and technical services such as inventory control. In addition, ISDN also facilitates e-mail exchange and desktop publishing and provisions links to attendance records, student transcripts, and administrative policies and reports. 1.15.3.2 Butte College Butte College uses ISDN technology for facilitating access to library resources and interactive videoconferencing sessions between students at distant locations and faculty in classrooms on the main campus. Students working full-time participate in ISDN videoconferencing sessions at home or in the workplace. 1.15.3.3 Los Angeles Harbor and West Valley Community Colleges At the Los Angeles Harbor and the West Valley Community Colleges, ISDN supports teletraining and teleconferencing sessions and enables place-bound students to access diverse tele-education courses and programs. 0889Ch01Frame Page 23 Wednesday, April 17, 2002 3:06 PM © 2002 by CRC Press LLC 1.15.3.4 Mendocino Unified School District The Mendocino Unified School District employs an ISDN platform to inform stu- dents about career opportunities in technology. This platform supports access to applications that enable students to develop skills in communications, problem solving, critical thinking, and information literacy. In addition, ISDN-based video- conferencing enables students to study real-world issues with their peers at remote locations and experts in the field. During these interactive videoconferences, Men- docino students learn to justify positions, ask critical questions, and draw conclusions based on the information presented. ISDN-based videoconferences also support virtual explorations beyond the con- fines of the school setting. As an example, Mendocino Middle School students met virtually with NASA (National Aeronautics and Space Administration) scientists at a remote location and participated in a virtual tour of a space shuttle mockup. The Mendocino Unified School District also owns and operates the ISDN-supported Mendocino Community Network. 1.15.3.5 Pasadena and Sacramento Public Libraries Library patrons and local residents utilize ISDN teleservices at the Pasadena and Sacramento Public Libraries for Web browsing, searching reference indexes, and accessing electronic library (E-library) digital resources. 1.15.4 FLORIDA 1.15.4.1 Broward County School District The Broward County School District employs an ISDN network that interlinks district high schools and supports interactive videoconferencing sessions, team- teaching, in-service training, and expanded course offerings. The Broward County School District ISDN configuration also enables high school students to participate in special programs and tele-enrichment activities and enroll in virtual classes spon- sored by local community colleges. Moreover, high school teachers participate in real-time ISDN-supported administrative telemeetings, teleworkshops, and telesym- posia via the Broward County School District ISDN implementation. 1.15.4.2 Florida International University (FIU) The Florida International University (FIU) Career Planning and Placement Center uses ISDN to support tele-interviews between upcoming graduates and prospective employers throughout the United States. 1.15.4.3 Nova Southeastern University (NSU) Regardless of location, working professionals enrolled in advanced degree programs in fields that include education, public health, and pharmacy at Nova Southeastern Uni- versity (NSU) participate in ISDN-supported interactive graduate class telesessions, teleworkshops, and videoconferences with peers, subject experts, and NSU professors. 0889Ch01Frame Page 24 Wednesday, April 17, 2002 3:06 PM © 2002 by CRC Press LLC 1.15.5 ILLINOIS 1.15.5.1 North Suburban Higher Education Consortium (NSHEC) The North Suburban Higher Education Consortium (NSHEC) sponsors implementation of an ISDN interactive videoconferencing network for high schools, hospitals, research laboratories, community colleges, and universities in the Northern Chicago suburbs. 1.15.5.2 Northwestern University Northwestern University uses ISDN technology to link videoconferencing facilities at its Evanston and Chicago campuses for supporting interactive telecourse sessions, videoconferences, and telecollaborative research projects. The ISDN facilities also interoperate with NSHEC ISDN videoconferencing installations. 1.15.6 INDIANA 1.15.6.1 Indiana Higher Education Telecommunications System (IHETS) The Multicampus Technology Project sponsored by the Indiana Higher Education Telecommunications System (IHETS) supports ISDN videoconferences between Indiana University campus sites. This ISDN configuration enables interactive virtual classes and telecollaborative research projects. 1.15.6.2 Notre Dame University The University of Notre Dame at South Bend employs a mixture of T-1 and ISDN technologies for interactive videoconferencing and distance education course deliv- ery in graduate programs in business and management to off-campus students. Transmission rates at 384 Kbps are supported. 1.15.7 KANSAS 1.15.7.1 Fort Hays State University (FHSU) Fort Hays State University (FHSU) employs ISDN point-to-multipoint videoconfer- ences for real-time tele-instruction. The FHSU ISDN configuration also enables connections to the Kansas University Medical Center, Wichita State University, the State Board of Education, and the High Southwest Plains Network for supporting teleseminars and curricular enhancement programs. Additionally, FHSU participates in the A+ network. This network employs ATM technology for enabling high-speed, high-capacity voice, video, and data transmission via optical fiber links. 1.15.8 MICHIGAN 1.15.8.1 Dexter Community Schools and MichNet (Michigan Network) Dexter Community Schools use ISDN technology for interlinking community school sites to MichNet (Michigan Network). A statewide educational and research network 0889Ch01Frame Page 25 Wednesday, April 17, 2002 3:06 PM © 2002 by CRC Press LLC [...]... http://www.tis.bl.ui/ © 20 02 by CRC Press LLC 0889Ch02Frame Page 47 Wednesday, April 17, 20 02 3:05 PM 2 2.1 Asynchronous Transfer Mode (ATM) Networks INTRODUCTION Demand for fast and dependable access to Web-based applications and real-time delivery of multimedia transmissions via an integrated network infrastructure drives implementation of ATM (Asynchronous Transfer Mode) broadband solutions ATM... capabilities of next-generation ATM networks are explored Research initiatives in the ATM arena are highlighted © 20 02 by CRC Press LLC 0889Ch02Frame Page 48 Wednesday, April 17, 20 02 3:05 PM 2. 3 2. 3.1 ATM FOUNDATIONS ATM DEVELOPMENT The ATM platform enables multimedia transmission via fixed-sized 53-byte packets called cells in network environments ranging from desk area networks (DANs) to global implementations... marketplace Representative EuroISDN projects in the E-commerce sector sponsored by the European Commission are highlighted in this section © 20 02 by CRC Press LLC 0889Ch01Frame Page 42 Wednesday, April 17, 20 02 3:06 PM 1 .22 .1 A NETWORK OF SMALL–MEDIUM ENTERPRISE NETWORKS USING TELEMATICS (AGORA) AGORA was a multilingual initiative that supported interactive videoconferencing, remote file access, groupware... records and monitor student progress © 20 02 by CRC Press LLC 0889Ch01Frame Page 28 Wednesday, April 17, 20 02 3:06 PM This network also enables students in schools with class sizes that do not justify salaries for on-site instructors to participate in virtual Advanced Placement (AP) classes 1.15.15 1.15.15.1 WASHINGTON K 20 Educational Telecommunications Network The K 20 Educational Telecommunications Network... telecollaborative NREN activities GÉANT, the next-generation Trans-European Network, succeeded TEN-155 on November 1, 20 01 Operational between December 1998 and October 30, 20 01, TEN-155 supported multimedia transmission at rates of 155. 52 Mbps (OC3) and 622 .08 Mbps (OC- 12) DANTÉ also manages the GÉANT Program 2. 3.5 TRANS-EUROPEAN NETWORK-34.368 MBPS (TEN-34) INITIATIVE As with the JAMES Project, the TEN-34 (Trans-European... Service) guarantees © 20 02 by CRC Press LLC 0889Ch02Frame Page 51 Wednesday, April 17, 20 02 3:05 PM Participants in the QUANTUM Program included ACONET (NREN of Austria), HEAnet (NREN of Ireland), and ARNES (NREN of Slovenia) In addition, BELnet (NREN of Belgium), DFN or Deutsche Forschungsnetz (NREN of Germany), HUNGARnet (NREN of Hungary), NORDUnet2 (the Nordic Countries Network, Phase 2) , and SuperJANET... center in the world 1 .20 .2 NORWAY 1 .20 .2. 1 Telemedicine Department in Northern Norway The Norwegian Telemedicine Department in Northern Norway enables delivery of clinical telemedicine services to isolated populations Specialists routinely conduct teleconsultations with primary care physicians via EuroISDN videoconferencing systems Rates at 384 Kbps are supported 1 .20 .3 UNITED KINGDOM 1 .20 .3.1 University... for EuroISDN is under consideration 1 .21 EUROPEAN COMMISSION TELEMATICS APPLICATIONS PROGRAM (EC-TAP) TELEMEDICINE PROJECTS Projects in the healthcare domain sponsored by the European Commission Telematics Applications Program (EC-TAP) are highlighted in the material that follows © 20 02 by CRC Press LLC 0889Ch01Frame Page 41 Wednesday, April 17, 20 02 3:06 PM 1 .21 .1 DIABCARE Q-NET The DiabCare Q-Net... Association (UKERNA), SURFnet (National Research and Education Network or the NREN of the Netherlands), and RedIRIS (NREN of Spain) also supported JAMES experiments © 20 02 by CRC Press LLC 0889Ch02Frame Page 49 Wednesday, April 17, 20 02 3:05 PM 2. 3.4 DELIVERY OF ADVANCED NETWORK TECHNOLOGY (DANTÉ) TO EUROPE, LTD DANTÉ (Delivery of Advanced Network Technology to Europe, Ltd.) provided technical service and... clinics The CARMEN ISDN platform also enables transmission of patient x-rays and CAT © 20 02 by CRC Press LLC 0889Ch01Frame Page 40 Wednesday, April 17, 20 02 3:06 PM (Computerized Axial Tomography) scans from rural clinics to major urban hospitals for enabling telediagnoses and determining treatment plans 1 .20 .1 .2 Quebec Interregional Telemedicine Network The Quebec Interregional Telemedicine Network . and video surveillance. At the Huntsville School System, 0889Ch01Frame Page 22 Wednesday, April 17, 20 02 3:06 PM © 20 02 by CRC Press LLC an ISDN configuration supports transmission of video images. Server ISDN Internet Proxy/Caching Server Analog Modem Analog Laptop with internal modem Mobile User 0889Ch01Frame Page 20 Wednesday, April 17, 20 02 3:06 PM © 20 02 by CRC Press LLC 1.13.1 SIEMENS Available from Siemens, the Optiset series. telesurgery, and virtual grand rounds in the field of telemedicine. 0889Ch01Frame Page 21 Wednesday, April 17, 20 02 3:06 PM © 20 02 by CRC Press LLC 1.15 UNITED STATES (U.S.) ISDN TELE-EDUCATION INITIATIVES The