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network research support services

Marlyn Kemper Littman
Nova Southeastern University, USA


The remarkable popularity of Web-based applications featuring text, voice, still images, animations, full-motion video and/or graphics and spiraling demand for broadband technologies that provision seamless multimedia delivery motivate implementation of asynchronous transfer mode (ATM) in an array of electronic learning (e-learning) environments (Parr & Curran, 2000). Asynchronous refers to ATM capabilities in supporting intermittent bit rates and traffic patterns in response to actual demand, and transfer mode indicates ATM capabilities in transporting multiple types of network traffic.

E-learning describes instructional situations in which teachers and students are physically separated (Lee, Hou & Lee, 2003; Hunter & Carr, 2002). ATM is a high-speed, high-performance multiplexing and switching communications technology that bridges the space between instructors and learners by providing bandwidth on demand for enabling interactive real-time communications services and delivery of multimedia instructional materials with quality-of-service (QoS) guarantees.

Research trials and full-scale ATM implementations in K-12 schools and post-secondary institutions conducted since the 1990s demonstrate this technology’s versatility in enabling telementoring, telecollaborative research and access to e-learning enrichment courses. However, with enormous bandwidth provided via high-capacity 10 Gigabit Ethernet, wavelength division multiplexing (WDM) and dense WDM (DWDM) backbone networks; high costs of ATM equipment and service contracts; and interoperability problems between different generations of ATM core components such as switches, ATM is no longer regarded as a universal broadband solution.

Despite technical and financial issues, ATM networks continue to support on-demand access to Webbased course content and multimedia applications. ATM implementations facilitate the seamless integration of diverse network components that include computer systems, servers, middleware, Web caches, courseware tools, digital library materials and instructional resources such as streaming video clips in dynamic e-learning system environments. National research and education networks (NRENs) in countries that include Belgium, Croatia, Estonia, Greece, Israel, Latvia, Moldavia, Portugal, Spain, Switzerland and Turkey use ATM in conjunction with technologies such as Internet protocol (IP), synchronous digital hierarchy (SDH), WDM and DWDM in supporting synchronous and asynchronous collaboration, scientific investigations and e-learning initiatives (TERENA, 2003).

This article reviews major research initiatives contributing to ATM development. ATM technical fundamentals and representative ATM specifications are described. Capabilities of ATM technology in supporting e-learning applications and solutions are examined. Finally, trends in ATM implementation are explored.


Bell Labs initiated work on ATM research projects during the 1960s and subsequently developed cell switching architecture for transporting bursty network traffic. Initially known as asynchronous time-division multiplexing (ATDM), ATM was originally viewed as a replacement for the time-division multiplexing (TDM) protocol that supported transmission of time-dependent and time-independent traffic and assigned each fixed-sized packet or cell to a fixed timeslot for transmission. In contrast to TDM, the ATM protocol dynamically allocated timeslots to cells on demand to accommodate application requirements.

In the 1990s, the foundation for practical ATM e-learning implementations was established in the European Union (EU) with the Joint ATM Experiment on European Services (JAMES); Trans-European Network-34.368 Mbps or megabits per second (TEN-34); and TEN-155.52 Mbps (TEN-155) projects. EU NRENs such as Super Joint Academic Network (SuperJANET) in the United Kingdom and SURFnet in The Netherlands demonstrated ATMs’ dependable support of multimedia applications with QoS guarantees, interactive videoconferences and IP multicasts via optical connections at rates reaching 2.488 gigabits per second (Gbps, or in OC-48 in terms of optical carrier levels).

Implemented between 1994 and 1999, the European Commission (EC) Advanced Communications Technology and Services (ACTS) Program demonstrated ATM technical capabilities in interworking with wireline and wireless implementations. For instance, the EC ACTS COIAS (convergence of Internet ATM satellite) project confirmed the use of IP version 6 (IPv6) in enhancing network functions in hybrid satellite and ATM networks. The EC ACTS AMUSE initiative validated ATM-over-asynchronous digital subscriber line (ADSL) capabilities in delivering time-critical interactive broadband services to residential users (Di Concetto, Pavarani, Rosa, Rossi, Paul & Di Martino, 1999).

A successor to the EC ACTS Program, the EC Community Research and Development Information Service (CORDIS) Fifth Framework Information Society Technologies (IST) Program sponsored technical initiatives in the ATM arena between 1998 and 2002. For example, the open platform for enhanced interactive services (OPENISE) project verified capabilities of the ATM platform in interworking with ADSL and ADSL.Lite in supporting multimedia services and voice-over-ATM implementations. The creation and deployment of end user services in premium IP networks (CADENUS) initiative confirmed the effectiveness of ATM, IP and multiprotocol label switching (MPLS) operations in facilitating delivery of multimedia applications with QoS guarantees via mixed-mode wireline and wireless platform. The IASON (generic evaluation platform for services interoperability and networks) project validated the use of ATM in conjunction with an array of wireline and wireless technologies including universal mobile telecommunications systems (UMTS), IP, integrated services digital network (ISDN) and general packet radio service (GPRS) technologies. The WINMAN (WDM and IP network management) initiative demonstrated ATM, SDH and DWDM support of reliable IP transport and IP operations in conjunction with flexible and extendible network architectures. The NETAGE (advanced network adapter for the new generation of mobile and IP-based networks) initiative verified ATM, ISDN and IP functions in interworking with global systems for mobile communications (GSM), a 2G (second generation) cellular solution, and GPRS implementations.

Research findings from the Fifth Framework Program also contributed to the design of the transborder e-learning initiative sponsored by the EC. Based on integrated information and communications technology (ICT), this initiative supports advanced e-learning applications that respect language and cultural diversity and promotes digital literacy, telecollaborative research, professional development and lifelong education.

In the United States (U.S.), an IP-over-ATM-over-synchronous optical network (SONET) infrastructure served as the platform for the very high-speed broadband network service (vBNS) and its successor vBNS+, one of the two backbone networks that originally provided connections to Internet2 (I2). A next-generation research and education network, sponsored by the University Consortium for Advanced Internet Development (UCAID), I2 supports advanced research and distance education applications with QoS guarantees. Although replacement of ATM with ultra-fast DWDM technology as the I2 network core is under way, ATM technology continues to provision multimedia services at I2 member institutions that include the Universities of Michigan, Mississippi and Southern Mississippi, and Northeastern and Mississippi State Universities.


To achieve fast transmission rates, ATM uses a standard fixed-sized 53-byte cell featuring a 5-byte header or addressing and routing mechanism that contains a virtual channel identifier (VCI), a virtual path indicator (VPI) and an error-detection field and a 48-byte payload or information field for transmission. ATM supports operations over physical media that include twisted copper wire pair and optical fiber with optical rates at 13.27 Gbps (OC-192). Since ATM enables connection-oriented services, information is transported when a virtual channel is established. ATM supports switched virtual connections (SVCs) or logical links between ATM network endpoints for the duration of the connections, as well as permanent virtual connections (PVCs) that remain operational until they are no longer required (Hac, 2001).

ATM specifications facilitate implementation of a standardized infrastructure for reliable class of service (CoS) operations. ATM service classes include available bit rate (ABR), to ensure a guaranteed minimum capacity for bursty high-bandwidth traffic; constant bit rate (CBR), for fixed bit-rate transmissions of bandwidth-intensive traffic such as interactive video; and unspecified bit rate (UBR), for best-effort delivery of data-intensive traffic such as large-sized files. Also an ATM CoS, variable bit rate (VBR) defines parameters for non-real-time and real-time transmissions to ensure a specified level of throughput capacity to meet QoS requirements (Tan, Tham & Ngoh, 2003). Additionally, ATM networks define parameters for peak cell rate (PCR) and sustainable cell rate (SCR); policies for operations, administration and resource management; and protocols and mechanisms for secure transmissions (Littman, 2002).

ATM service classes combine the low delay of circuit switching with the bandwidth flexibility and high speed of packet switching. ATM switches route multiple cells concurrently to their destination, enable high aggregate throughput, and support queue scheduling and cell buffer management for realization of multiple QoS requirements (Kou, 1999). ATM employs user-to-network interfaces (UNIs) between user equipment and network switches, and network-to-network interfaces (NNIs) between network switches; and enables point-to-point, point-to-multipoint and multipoint-to-multipoint connections.

Layer 1, or the Physical Layer of the ATM protocol stack, supports utilization of diverse transmission media, interfaces and transport speeds; transformation of signals into optical/electronic formats; encapsulation of IP packets into ATM cells; and multiplexing and cell routing and switching operations. Situated above the ATM Physical Layer, Layer 2—or the ATM Layer—uses the ATM 53-byte cell as the basic transmission unit, which operates independently of the ATM Physical Layer and employs ATM switches to route cellular streams received from the ATM Adaptation Layer (AAL), or Layer 3, to destination addresses. The AAL consists of five sublayers that enable cell segmentation and re-assembly, and CBR and VBR services.

Widespread implementation of IP applications contributes to utilization of IP overlays on ATM networks. To interoperate with IP packet-switching services, ATM defines a framing structure that transports IP packets as sets of ATM cells. ATM also interworks with ISDN, frame relay, fibre channel, digital subscribe line (DSL), cable modem, GSM, UMTS and satellite technologies.


Standards groups in the ATM arena include the International Telecommunications Union-Telecommunications Sector (ITU-T), European Telecommunications Standards Institute (ETSI), ATM Forum and the International Engineering Task Force (IETF). Broadband passive optical networks (BPONs) compliant with the ITU-T G.983.1 Recommendation enable optical ATM solutions that support asymmetric transmissions downstream at 622.08 Mbps (OC-12) and upstream at 155.52 Mbps (OC-3) (Effenberger, Ichibangase & Yamashita, 2001).

Sponsored by ETSI (2001), the European ATM services interoperability (EASI) and Telecommunications and IP Harmonization Over Networks (TIPHON) initiatives established a foundation for ATM interoperability operations and ATM QoS guarantees. HiperLAN2 (high performance radio local area network-2), an ETSI broadband radio access network specification, works with ATM core networks in enabling wireless Internet services at 54 Mbps.

The ATM Forum establishes ATM interworking specifications, including ATM-over-ADSL and protocols such as multi-protocol-over-ATM (MPOA) for encapsulating virtual LAN (VLAN) IP packets into ATM cells that are routed across the ATM network to destination VLAN addresses. The ATM Forum promotes integration of ATM and IP addressing schemes for enabling ATM devices to support IP version 4 (IPv4) and IPv6 operations, as well as security mechanisms and services such as elliptic curve cryptography.

Defined by the IETF, the IP multicast-over-ATM Request for Comments (RFC) supports secure delivery of IP multicasts to designated groups of multicast recipients (Diot, Levine, Lyles, Kassem & Bolensiefen, 2000). The IETF also established RFC 2492 to support ATM-based IPv6 services. IPv6 overcomes IPv4 limitations by providing expanded addressing capabilities, a streamlined header format and merged authentication and privacy functions.

The Third Generation Partnership Project (3GPP), an international standards alliance, endorsed the use of ATM as an underlying transport technology for 3G UMTS core and access networks and satellite-UMTS (S-UMTS) configurations (Chaudhury, Mohr & Onoe, 1999). Developed by the European Space Agency (ESA) and endorsed by the ITU-T, S-UMTS supports Web browsing and content retrieval, IP multicasts and videoconferencing. S-UMTS also is a component in the suite of air interfaces for the International Mobile Telecommunications-Year 2000 (IMT-2000). This initiative enables ubiquitous mobile access to multimedia applications and communications services (Cuevas, 1999).


A broadband multiplexing and switching technology that supports public and private wireline and wireless operations, ATM enables tele-education applications with real-time responsiveness and high availability (Kim & Park, 2000). In this section, ATM e-learning initiatives in Estonia, Lithuania and Poland are examined. These countries also participate in EC e-learning program initiatives that support foreign language tele-instruction, intercultural exchange, pedagogical innovations in distance education and enhanced access to e-learning resources. ATM e-learning initiatives in Singapore and the U.S. are also described.


The Estonian Education and Research Network (EENET) provisions ATM-based videoconferences and multicast distribution in the Baltic States at institutions that include the University of Tartu and Tallinn Technical University. A participant in the (networked education (NED) and Swedish-ATM (SWEST-ATM) projects, EENET also enables ATM links to the Royal Institute of Technology in Stockholm, Tampere University in Finland and the National University of Singapore (Kalja, Ots & Penjam, 1999).


The Lithuania Academic and Research Network (LITNET) uses an ATM backbone network to support links to academic libraries and scientific institutions; GÉANT, the pan European gigabit network; and NRENs such as EENET. The Lithuania University of Agriculture and Kaunas Medical University employ ATM and Gigabit Ethernet technologies for e-learning projects. The Kaunas Regional Distance Education Center uses ATM in concert with ISDN and satellite technologies to support access to distance education courses (Rutkauskiene, 2000).


Sponsored by the State Committee for Scientific Research (KBN, 2000), the Polish Optical Internet (PIONIER) project employs a DWDM infrastructure that interworks with ATM, Gigabit Ethernet, IP and SDH technologies. This initiative supports e-learning applications at Polish educational institutions and research centers, including the Wroclaw University of Technology.


The Singapore Advanced Research and Education Network (SingAREN) supports ATM connections to the Asia Pacific Area Network (APAN), the Trans-Eurasia Information Network (TEIN) and the Abilene network via the Pacific Northwest GigaPoP (gigabit point of presence) in Seattle, Washington, U.S. SingAREN transborder connections enable the Singapore academic and research community to participate in global scientific investigations and advanced e-learning initiatives in fields such as space science and biology. Academic institutions in Singapore that participate in SingAREN include the National Technological University.



The Maine Distance Learning Project (MDLP) employs ATM to support ITU-T H.323-compliant videoconferences and facilitate access to I2 resources. The ATM infrastructure enables high school students at MDLP sites with low enrollments to participate in calculus physics and anatomy classes and take advanced college placement courses. In addition, the MDLP ATM configuration provisions links to graduate courses developed by the University of Maine faculty; certification programs for teachers, firefighters and emergency medical personnel; and teleworkshops for state and local government agencies.

New Hampshire

The Granite State Distance Learning Network (GSDLN) employs an ATM infrastructure for enabling tele-education initiatives at K-12 schools and post-secondary institutions. GSDLN provides access to professional certification programs, team teaching sessions and enrichment activities sponsored by the New Hampshire Fish and Game Department.

Rhode Island

A member of the Ocean State Higher Education Economic Development and Administrative Network (OSHEN) Consortium, an I2 special-education group participant (SEGP), Rhode Island Network (RINET) employs ATM to facilitate interactive videoconferencing and provision links to I2 e-learning initiatives. RINET also sponsors an I2 ATM virtual job-shadowing project that enables students to explore career options with mentors in fields such as surgery.


The ATM Forum continues to support development of interworking specifications and interfaces that promote the use of ATM in concert with IP, FR, satellite and S-UMTS implementations; broadband residential access technologies such as DSL and local multipoint distribution service (LMDS), popularly called wireless cable solutions; and WDM and DWDM optical configurations. The Forum also promotes development of encapsulation methods to support converged ATM/MPLS operations for enabling ATM cells that transit IP best-effort delivery networks to provide QoS assurances. Approaches for facilitating network convergence and bandwidth consolidation by using MPLS to support an ATM overlay on an IP optical network are in development.

Distinguished by its reliable support of multimedia transmissions, ATM will continue to play a critical role in supporting e-learning applications and initiatives. In 2004, the Delivery of Advanced Network Technology to Europe (DANTE), in partnership with the Asia Europe Meeting (ASEM) initiated work on TIEN2, a South East Asia intra-regional research and education network that will support links to GÉANT (GN1), the pan-European gigabit network developed under the EC CORDIS IST initiative. GN1 employs an IP-over-SDH/WDM infrastructure that enables extremely fast transmission rates at heavily trafficked core network locations and an IP-over-ATM platform to facilitate voice, video and data transmission at outlying network sites.

The ATM Forum and the Broadband Content Delivery Forum intend to position ATM as an enabler of content delivery networks (CDNs) that deliver real-time and on-demand streaming media without depleting network resources and impairing network performance (ATM Forum, 2004). In the educational arena, ATM-based CDNs are expected to support special-event broadcasts, telecollaborative research, learner-centered instruction, Web conferencing, on-demand virtual fieldtrips and virtual training.

In addition to e-learning networks and multimedia applications, ATM remains a viable enabler of e-government, telemedicine and public safety solutions. As an example, Project MESA, an initiative developed by ETSI and the Telecommunications Industry Association (TIA), will employ a mix of ATM, satellite and wireless network technologies to support disaster relief, homeland security, law enforcement and emergency medical services (ETSI & TIA, 2004).


ATM technology is distinguished by its dependable support of e-learning applications that optimize student achievement and faculty productivity. ATM technology seamlessly enables multimedia transport, IP multicast delivery and access to content-rich Web resources with QoS guarantees. Despite technical and financial concerns, ATM remains a viable enabler of multimedia e-learning initiatives in local and wider-area educational environments. Research and experimentation are necessary to extend and refine ATM capabilities in supporting CDNs, wireless solutions, secure network operations, and interoperability with WDM and DWDM optical networks. Ongoing assessments of ATM network performance in provisioning on-demand and real-time access to distributed e-learning applications and telecollaborative research projects in virtual environments are also recommended.

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