ISDN Terminals and Integrated Services Delivery

This paper proposes that the end user's perception of an "ISDN service" should reflect'three interrelated ISDN aspects, namely:bulletISDN terminal capabilities,bulletISDN access capabilities, andbulletISDN network capabilities. Emphasis is placed on the ISDN terminal capabilities in supporting integrated services delivery of different levels to the end user (e.g., integrated bearer services and integrated teleservices delivery). Such a concept, integrated services delivery, is seen to suggest a useful framework for developing a wide range of possible ISDN commercial service/ product offerings. An ISDN service scenario is also described to illustrate some important communication capabilities made possible by an ISDN environment.     

A signaling protocol for complex multimedia services

The author introduces a signaling protocol for user applications that invokes multimedia services provided by the EXPANSE research prototype, a broadband ISDN testbed. A generic framework that flexibly accommodates a wide variety of services involving multiple parties with heterogeneous terminals is described. The author describes the generic services supported, introduces the EXPANSE call model, discusses syntax and message flow procedures, and relates EXPANSE signaling to the ISDN signaling control part (ISCP) and long-term broadband ISDN signaling work currently under study by CCITT     

Performance modeling of Signaling System No.7

The layered performance modeling approach is refined and extended to cover the latest CCITT Blue Book specifications. Specific submodels for the higher-level functional blocks, such as the message transfer part (MTP) level 3, the signaling connection control part (SCCP), the ISDN user part (ISDN-UP), and the transaction capabilities application part (TCAP), are given in a generic way, explicitly. With these submodels, generic models for signaling points and signaling transfer points are constructed. The major functional parts of the layered protocol architecture of SS7 are modeled in a generic way by extended queuing network elements such as full duplex flow controlled links, priority processors, multiple-chain multiple-class traffic streams, or elements for segmenting and reassembling of messages. The analysis of the whole network starts from a global traffic flow analysis, which takes all the different signaling message types, their paths through the network, and the load into account. The overall performance measures, such as end-to-end transfer times, are found from all the component delays. The analytical results have been validated by simulation, revealing a high degree of accuracy     

Common channel signaling for international service applications

The message transfer, telephone user, and integrated services digital network (ISDN) user parts of CCITT Signaling System No.7 (SS7) are described. The introduction of SS7 to provide control of international circuits is described. The intent is to provide a perspective on the advantages of using common channel signaling for ISDN     

ISDN protocol architecture

IT IS NOW widely recognized that the Integrated Services Digital Network (ISDN) concept is providing a useful framework for the development of future telecommunications networks and services. An ISDN can be regarded as a generalpurpose digital network capable of supporting (or integrating) a wide range of services (voice and non-voice) using a small set of standard multipurpose user-network interfaces. Relevant CCITT Recommendations (or standards) on ISDN interfaces were expected to be available in 1984, the final year of the current study period. This paper reviews CCITT progress on the architectural studies of protocols associated with ISDN's, in particular, the ISDN Protocol Reference Model being developed by Study Group XVIII. This Model, based on the concepts and principles of the ISO/CCITT Open Systems Interconnection (OSI) Reference Model, aims at providing a unified framework for modeling ISDN multiservice communications and capabilities. The new Model is applied to several possible ISDN communications configurations, enabling a number of technical issues to be easily identified.     

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.     

An overview of Signaling System No.7

An overview of Signaling System No.7 (SS7) is presented. The salient features of SS7's network services part (NSP) are described. Functionally, NSP corresponds to the first three layers of the Open System Interconnection (OSI) reference model. The signaling network structures that, in conjunction with the NSP, provide integrated services digital network (ISDN) nodes with a highly reliable and efficient means of exchanging signaling messages are discussed. The nodal capabilities of call control and remote process invocation and management, part of the SS7 user parts, are described. The very stringent performance requirements of signaling systems and their reflection on the critical nature of signaling functions and their real-time exigencies are discussed. The likely evolution of network signaling in the remaining years of the 20th century is discussed     

Signaling System No.7: a tutorial

A tutorial overview of the salient features of SS7 is provided. Its history is briefly reviewed, and the SS7 network services part (NSP), which corresponds to the first three layers of the Open Systems Interconnection (OSI) Reference Model, is described. Signaling network structures that, in conjunction with the NSP, provide integrated services digital network (ISDN) nodes with a highly reliable and efficient means of exchanging signaling messages are discussed. The nodal capabilities of connection (call) control and remote process invocation and management and other functions of the user parts of SS7 are examined. The very stringent performance requirements of signaling systems, which reflect the critical nature of signaling functions and their real-time exigencies, are stressed. A broad outline of the likely evolution of ISDN signaling systems in the remaining years of this century is sketched     

Distributed Control in a Key Telephone System

This paper describes the distributed microprocessor architecture used in the Electra IMS digital communication system. The system has been in service in the U.S. as of 1985. The system's maximum line size is 160, its maximum trunk size is 80, and it can accommodate both normal single-line telephones and proprietary digital telephones. Data switching can also be performed because of the PCM/ TDM architecture. The distributed architecture is composed of a system control (SCU) and six module control units (MCU), each MCU handles 32 ports of peripheral equipment.bulletThe SCU and MCU's have a simplified common OS designed to handle the basic call processes.bulletThe SCU executes line-state control, time-slot control, and systemfeature application.bulletThe MCU executes peripheral-operation control and peripheral-status control. Software architecture is divided into small modules which represent each system function at the SCU, or each operating sequence at the MCU, so that addition or deletion of system features is very easy to implement. Hand-shaking belwccn the SCU and MCU's is controlled using a "message" which consists of several words. This architecture enables a nonsquare key telephone configuration, the building-block concept, and future system enhancement.     

Routing and congestion control in common channel Signaling SystemNo.7

The routing and congestion control function of Signaling System No.7 (SS7) are described. The elements of the SS7 protocol functional division include message transfer part (MTP), signaling correction control part (SCCP), ISDN user part (ISUP), and transaction capabilities (TC). The routing function, which takes place at the MTP and SCCP, and the congestion control function, which is present in multiple layers, are discussed. This includes MTP level 2, MTP level 3 by signaling traffic flow control procedures, and flow control for connection-oriented services of SCCP. To illustrate the unique capabilities present in SS7, the routing and congestion control functions in SS7 are compared to other common connectionless network layers. Performance considerations in routing and congestion control are discussed     

Signaling System No. 7 ISDN User Part

The integrated services digital network (ISDN) user part of Signaling System No. 7 defines the signaling protocol which supports the establishment, supervision, and release of voice and nonvoice calls over circuit-switched connections between ISDN terminations of digital subscriber access lines. This paper gives an overview of the ISDN user part protocol, as defined in CCITT Recommendations Q.761-Q.766 [1], in terms of the signaling functions and procedures provided to support call and connection control in an ISDN, and in terms of the information elements and signaling messages that are used by the signaling functions in ISDN exchanges to communicate.     

ISDN computer-aided telephony

It is argued that ISDN computer-aided telephony requires properly architected platforms to satisfy changing application needs during the 1990s. Proper architecting necessitates the use of functionally rich and consistent telephony application programming interfaces (APIs). Other APIs are also needed to support integrated applications. The coexistence of telephony and other APIs must be accommodated in the ISDN driver architecture to make efficient use of D-channel signaling and voice, data, or image communications on the associated B/H channels. This driver may support Open Systems Interconnection (OSI), Systems Network Architecture (SNA), X.25, or other protocol stacks in the same computer using a single ISDN access link. Applications being currently explored show that significant benefits can be realized using incoming call management and LAN-based image server access by means of ISDN. It is envisioned that by the year 2001, a common API will facilitate multimedia applications on multivendor platforms architected within the OSI framework. These platforms will support interconnections of public and private ISDNs and bridging to BISDNs     

Common channel signaling in the AT&T US 5ESS switch

A brief history of the evolution that has led to the development of Signaling System No.7 (SS7) capabilities on the 5ESS switch is presented, and the hardware and software components that provide the SS7 functionality for the 5ESS switch are described. Specifically, the functionality provided by the Common Network Interface (CNI) ring, which has been used on several AT&T SS7 products is discussed. The 5ESS switch-specific common channel signaling (CCS) transport software (which is responsible for the transport of SS7 messages among 5ESS switch processing elements), the user interfaces (which provide customer administration of switch data, color display of status information, reports on the state of the SS7 network, and the tests to verify message routing through the network), and message routing itself are discussed. The SS7 ISDN user part (ISUP) and transaction capabilities application (TCAP) functionalities implemented in 5ESS switch software are described in terms of how they fit into the 5ESS switch architecture. SS7 call handling capacities and the ways in which reliability challenges are met are described     

Omissions and ambiguities in CCITT Recommendation Q.921

The data link layer protocol for the integrated services digital network (ISDN) user/network interface, known as link access protocol-D (LAPD), is a protocol that operates at layer 2 of the open systems interconnection (OSI) architecture. Its purpose is to safely convey information between layer 3 entities using the D-channel. The information types that LAPD is intended to transport include call control signaling, packet mode communications, and management information. Observations are made in this article about what are, in the authors' opinion, the most confusing points of CCITT Recommendation Q.921 with comments related to data link layer address field, broadcast connections, terminal endpoint identifier (TEI) management procedures, layer 2 frames exchange, and connection management entity response to MDL-error indication primitives. This article intends solely to clarify the recommendations so that their concepts and procedures become easier to understand and implement, which can lead to significant saving of time for those who must eventually use LAPD procedures or develop the software for handling them     

An ISDN Subscriber Loop Transmission System Based on Echo Cancellation Technique

This paper proposes an ISDN subscriber loop transmission system based on an echo cancellation technique which fully supports the CCITT recommended basic interface for ISDN, i.e.,B + B + Dover metallic cables. System design considerations of cable loss, crosstalk, impulsive noise, and system requirements such as power feeding on a caLl-by-call basis are discussed, and a transmission system is proposed. The proposed system is characterized by the use of a new line code, named "modified biphase code." The use of this code with fixed line loss equalization and coherent detection achieves circuit simplification. A special adaptation algorithm is incorporated with the echo canceller that significantly reduces convergence time. Experimental results show satisfactory performance with respect to the residual echo and the bit error rate. Since the system requires only a simple nonadaptive circuit for analog portion, it is suitable for LSI implementation.     

IMS与传统PSTN网络的互通问题研究

目前,下一代网络（NGN）的核心技术正从传统软交换向IP多媒体子系统（IMS）衍化。在IMS这个全新的网络构架下,如何实现与传统公用交换电话网（PSTN）的互通成为目前网络转化过程中急需解决的问题之一。从阐述IMS网络的系统架构入手,通过典型的呼叫实例分析,探讨从IMS终端到PSTN终端的呼叫流程。着重分析互通过程中各IMS网络功能实体的详细作用,以及会话发起协议（SIP）与综合业务数字网用户部分（ISUP）之间的转换映射关系。     

Broadband ISDN Switching Capabilities from a Services Perspective

Broadband switching and transmission technologies are maturing rapidly, promising to make broadband ISDN (B-ISDN) possible and potentially economical in the near future. The diversity of possible B-ISDN services provides much impetus for the implementation of B-ISDN, but complicates the task of specifying network switching requirements. This paper examines a few representative services in order to generate a set of basis vectors in capability space. New services are then projected onto this basis; if a new service cannot be constructed from the basis vectors, other vectors are added to the basis set. B-ISDN architects can then specify switching requirements by selecting those capability basis vectors that are required for the services most in demand. For full motion entertainment video services, circuit switching capability at about 150 Mbit/s may be required, while selective broadcast and remote switching capabilities may reduce the cost of these services. For subvideo-rate services, new transfer mode (NTM) capability may be required to allow users the flexibility to allocate access channels dynamically on a per-call basis. Multiple connection (e.g., voice and video) and multiple party call capabilities may be required for many B-ISDN services, implying a need to extend the ISDN signaling protocol. The capability for the user to request network code conversion between different coding formats (e.g., NTSC or HDTV), and network compression of signals to reduce the cost of interoffice facilities, may also be required. Finally, fast call setup capability and high calling volume capabilities may be required, implying a need to distribute call processing functions over multiple processors in the central office.