Support of Existing Data Interfaces by the ISDN

During the past decade, the opportunity has arisen to economically combine data and voice services onto a single system, the integrated services digital network (ISDN). Studies in CCITT have led to the production of a set of Recommendations covering aspects of the ISDN, including the customer terminal interface. Inevitably, there are significant differences between the customer terminal interfaces recommended for dedicated data networks and that proposed for the ISDN. To ensure a smooth transition towards the introduction of ISDN based services, the CCITT have published recommendations describing how existing terminal interface designs may be connected to an ISDN. These recommendations are the subject of this paper.     

ISDN: a customer perspective

Early projected benefits of the integrated services digital network (ISDN) are evaluated from a customer premises equipment (CPE) perspective. It is argued that economic conditions continue to affect ISDN investment in the USA. Worldwide customer acceptance of ISDN is contrasted with earlier projections and shown to be running at about 25% of earlier projections. IBM's current ISDN product set is discussed briefly. Even though the rollout of services has not yet achieved expectations, IBM believes the potential for ISDN use by customers is significant     

Southwestern Bell Telephone's ISDN experience

Southwestern Bell Telephone's (SWBTs) integrated services digital network (ISDN) experience has been heavily influenced by the realization that from a customer perspective, the most important aspects of ISDN are its applications. The authors describe the following ISDN applications that SWBT has been exploring: desktop conferencing; asynchronous protocol conversion to SNA/SDLC; VTAM INN link replacement; asynchronous protocol conversion to SNA/SDLC with multiplexing; remote 3174 multiplexing via B channel packet; remote 3174 multiplexing via B channel packet and NPSI; 327X emulation via SIMPC, SIM-VTAM, and NPSI; 327X emulation with QLLC and NPSI; asynchronous access to private packet-switched networks; asynchronous access to UNIX host; asynchronous access to UNIX host via PAD and X.25 multiplexing; 327X coaxial cable elimination; extended local area network with passive bus; asynchronous access to Ethernet terminal server; dedicated line replacement (64 kb/s); asynchronous modem pooling (out-dial); asynchronous modem pooling (in-dial); ISDN wide-area networking; ISDN data gateway; gateway to AppleTalk network; application processor features; circuit-switched compressed video; and Ethernet LAN bridging     

Integrating ISDN and OSI: an example

A successful multivendor trial demonstrating the integration of Open Systems Interconnection (OSI) and integrated services digital network (ISDN) technologies is discussed. The planning, staging, and results of this trial, which demonstrated ISDN as a viable transport technology for OSI data applications, are detailed. The technical requirements to be fulfilled and the initial plans are outlined. The actual configuration used is described, and the results are summarized     

Whatever happened to ISDN?

The integrated services digital network (ISDN) standard was defined in 1972 yet the progress towards its implementation has been very slow and very little is yet on offer to the consumer. The author looks at the vision where the concept of ISDN transforms the telephone network into a transport mechanism for all communications needs. Services offered by ISDN are discussed as are implementation and tariffs     

CITT E.700 recommendation series-a framework for trafficengineering of ISDN

Traffic engineering of ISDN (integrated services digital network) has become a key area of CCITT recommendations since 1985. The authors report on the first recommendations formalized in a dedicated series on ISDN traffic engineering, the CCITT E.700 series of recommendations. The authors also report on the ongoing work towards an extension of the series to cover integration of mobile services into ISDN, the E.750 series. Future directions related to such emerging issues as intelligent network services and broadband-ISDN/ATM (asynchronous transfer mode) are also reviewed     

Switching System Software Design for ISDN

The ISDN offers various services through multipurpose digital subscriber lines. The switching program for the ISDN should be so designed as to realize the control of various voice and nonvoice services and provide for developing service enhancement. To attain the goal, the ISDN services are classified hierarchically and each category is allocated to appropriate network nodes for implementation. As a result, the local switching program provides an out-slot subscriber line signaling capability and call connection with appropriate compatibility checking including a check for access capability to communications processing nodes. The switching program modules specific to analog services and those specific to digital services are separated to allow the use of the existing program file and to afford easy program design and maintenance. Remote-controlled switching is a suitable means for an economical introduction of the ISDN services to low traffic density areas. Special routing and reliability arrangements as well as the program structure for a remote-controlled switch are discussed.     

Narrowband and broadband ISDN CPE directions

Noting that ISDN customer premises equipment (CPE) is critical to the successful deployment of ISDN whatever the bandwidth, the author examines the market for narrowband and wideband integrated services digital network (NISDN and BISDN) CPE. He establishes the basic requirements for NISDN terminals and discusses terminal adaptors, digital telephone sets, screen-based telephony, workstations, customer premises networks, and CPE maintenance and upgrades. He examines the BISDN market and discusses the features and architecture of the terminals     

ISDN in France-1987 to 1990: from the first commercial offering tonational coverage of NUMERIS

NUMERIS, the commercial integrated services digital network (ISDN) in France, is discussed. National coverage was completed in 1990. NUMERIS specifications, network components, and customer premises equipment are described. Operational experience with NUMERIS, including equipment conformance testing and ISDN implementation, is examined. Applications development and the use of partnership ventures (usually involving a user, a service provider, and France Telecom) are discussed     

Positioning the Subscriber Loop Network for Digital Services

The need to enhance the digital transmission capability of the local loop network to provide for new services is widely recognized in the telecommunications industry. Companies around the world [1]-[3] have been working towards this goal and plan to use digital loop carrier (DLC) to meet this demand. Although this approach is generally accepted, there has been little information presented on how to plan for the evolution of the local plant. To address these pressing issues, the Bell System is introducing a concept called fundamental subscriber carrier planning (FSCP). This paper discusses the impact that digital services will have on the subscriber loop network, including loop plant design requirements necessary to position the network for up to 64 kbit/s digital services. Existing cable plant has the capability to support most digital services, but there are specific design requirements that are quite different from those required for the "typical" analog voiceband service. This paper reviews the need to position the loop for digital services, and substantiates the major conclusion that digital loop carrier technology offers a significant advantage when provisioning for digital services.     

Multi-rate ISDN

Multi-rate integrated services digital network (ISDN) is a new technology for providing dialed-up, circuit-switched, isochronous communications for bandwidths from 128 kb/s to 1.536 Mb/s (DS-1) or 1.920 Mb/s (CEPT-1). Multi-rate ISDN provides a simple way to extend ISDN network services to match the higher bandwidth requirements emerging for videoconferencing, multimedia, imaging, and other high-speed applications. Using this technology, network service providers can offer high-speed connectivity within the boundaries and benefits of existing, circuit-switched, central office and transmission equipment. Only minor changes are required in the operations administration and maintenance and provisioning (OAM&P) procedures associated with multi-rate ISDN, versus existing ISDN transmission and central office maintenance procedures     

Integration of Public and Private Networks

As the designs of private automatic branch exchanges (PABX's) evolve towards "electronic offices" and incorporate aspects of the integrated services digital network (ISDN), public exchanges are themselves taking on functions that were often only found in private networks. It is therefore pertinent to question the status of the PABX as a node of the ISDN rather than as a mere customer terminal. With the present designs of PABX's, public exchanges, and the signaling systems employed, it is not possible to provide PABX extensions with all the facilities on the public network which are available to directly connected main-exchange subscribers, although facilities available over private networks continue to proliferate. This paper considers aspects of signaling via both public and private networks to ensure that there need be no restriction on the facilities offered.     

ISDN-the path to broadband networks

The author evaluates the effect of ISDN (integrated services digital network) on the field of data networks, anticipates future directions for this technology, and discusses how the user should view these developments. It is emphasized that broadband ISDN (BISDN) is a service that has identified capabilities that are truly exciting and could very well dominate data networking in this decade. It is noted that the success of BISDN will depend strongly on the rollout of products, the ubiquity of its presence, and the tariffing of its services     

Design Issues in the ISDN U-Interface Transceiver

The design challenges faced in the integrated circuit realization of the basic customer access U-interface transceiver at 144 kbits/s in the integrated services digital network (ISDN) are summarized. Given the cost and performance objectives, this represents a very challenging design problem from an algorithmic and technology point of view. This survey paper describes the alternative design approaches concentrating on algorithmic issues as opposed to circuit design issues, in the context of the echo cancellation (EC) method of full duplex data transmission. Particular emphasis is given to the areas of echo cancellation, equalization, line code selection, and timing recovery.     

CCITT Recommendations on the ISDN: A Review

This paper gives a brief overview of the I-Series of Recommendations on the integrated services digital network (ISDN) developed by the International Telephone and Telegraph Consultative Committee (CCITT). This set of Recommendations is printed in the CCITT "Red Book." The I-Series Recommendations represent the first major step towards worldwide harmonization of the fast-growing digital network capabilities in support of multiservice (voice, data, and image) user applications. Over 25 different Recommendations set up standard guidelines and features for service capability, network architecture, and user-network interfaces in the ISDN.     

Considerations on Customer Access to the ISDN

A concept for a digital customer access to an integrated services digital network (ISDN) is proposed. It is based on a passive bus which conveys information by means of two circuit switched B channels and aDchannel to support associated signaling (outslot channel) dynamically multiplexed with slow speed packetized data and telemetry. The customer access can support multiple terminal arrangements with simultaneously active users. Information to be conveyed by theDchannel is transferred in the form of messages, each associated with a logical link which has to coexist with other logical links on the common physicalDchannel. Access to that channel is regulated by level 1 arbitration with collision avoidance. It is possible to connect one X.25 DTE with minimum adaptation to the customer installation.     

Design Philosophy and Hardware Implementation for Digital Subscriber Loops

This paper presents various requirements and configurations in the information network system (INS) NTT's version of the integrated services digital network (ISDN)- such as field trials, and technologies and equipment design of the digital subscriber loop using balanced wire pairs. The main aspects characterizing digital subscriber loops, are a customer access structure, a digital transmission system on existing subscriber loops, and customer interface. A configuration of two-wire digital subscriber loops with two customer access channels, which is adopted in the field trials, will be described. The time-shared two-wire digital transmission and power feeding methods on subscriber loops are discussed. The common mode rejection ratio (CMRR) is discussed in detail, since CMRR is one of the main factors which affects the transmission ability of balanced wire pairs. A proposed self-clocked four-wire customer interface utilizes time division multiplexing technique. The digital subscriber loop operates on a call-by-call basis for link establishment to avoid excessive power dissipations as well as to avoid impairments caused by crosstalk from other lines within a cable. Its design objectives and implementation are also discussed.     

Progress Towards Digital Subscriber Line Services and Signaling

With digital connectivity, future subscribers will be able to exercise local and network services involving the routine delivery, management, and processing of information. Accelerated by rapidly advancing technology, the evolutionary process towards digital connectivity and integrated voice and data services in the network is underway. This paper describes the methods of integrating voice and information capability into the telecommunications network. The attributes of this network will include the availability of digital connectivity directly to the subscriber, the availability of a robust signaling means between the subscriber and his local switching office, and common channel signaling to implement all interexchange signaling. Issues of interest include an overview of digital subscriber connectivity, signaling and information structures for these kinds of lines, communications protocols, and general network considerations for the provision of information services. Partitioning of intelligence between intelligent subscriber terminals and controllers and their switching system is investigated. The use of message and virtual channel switching facilities to handle limited information rate services is discussed. Finally, an exploratory digital subscriber line under investigation at Bell Laboratories is described.     

Digital subscriber lines: network considerations for ISDN BasicAccess standard

The authors review digital subscriber line (DSL) technology features and the key technical factors that have driven the development of the technology. The application of DSL technology to network access and the relevant standards activities that provide a framework for developing DSL performance requirements are considered. The important aspects of the physical and operational characteristics of the US loop plant that influenced critical technology choices are reviewed with an emphasis on the physical characteristics of the embedded loop plant and considerations pertinent to the economic provisioning and operations for ISDN (integrated services digital network) Basic Access. A review of the essentials of DSL technology for ISDN Basic Access is presented