Common Channel Signaling Research Articles

Network management-recent advances and future trends

The author provides an introduction to and an overview of network management (NM). He traces some of its history, discusses some of its recent advances, and projects some future trends. He describes many of the NM advances in the 1970s and 1980s that were made possible by stored-program control and operations systems. He examines the evolution to integrated services digital networks (ISDNs) and intelligent networks using common-channel signaling as their backbone.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

A generic integrated maintenance interface for network elements

A generic interface specification that could be used as a common definition for maintenance functions is described. The process of developing the generic interface specification is presented, including the definition of supported functions, the description of the protocol and language used, and the detailed enumeration of the message specifications to support these functions. Generic interfaces can provide economic advantages in software development, training, and opportunities for simplification of human interfaces for remote interaction with the intelligent network element. The specific case examined is the set of messages that have been developed for system maintenance of network elements including digital loop carrier, digital terminal and cross-connect equipment, digital multiplexing and line-terminating equipment, digital switching equipment, common-channel signaling systems, supervisory systems, environmental monitors, and network timing elements.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Callers' Perceptions of Post-Dialing Delays: The Effects of a New Signaling Technology

One benefit of Common-Channel Signaling (CCS), a new signaling system developed for telephone network applications, would be greatly reduced post-dialing delays. The question addressed was whether unilateral introduction of CCS in either the toll or local network would negatively affect caller behavior in the other network. Results indicate that a CCS toll network would increase caller impatience and abandonments on local calls but not vice versa. Implications of this effect are considered and felt to be far outweighed by the benefits of the CCS system.

Common Channel Signaling Network Evolution

This paper traces the evolution of the AT&T common channel signaling (CCS) network from its initial deployment as the common channel interoffice signaling (CCIS) network in 1976 to its present and future forms. Since the introduction of CCIS, the network has: added datagram direct-signaling capability, been reconfigured as a result of the AT&T divestiture, and been modernized by new digital and processor technology and by developments in software engineering techniques. In addition, the CCS network has become a key part of the AT&T service architecture, allowing faster nationwide deployment of services. The globalization and further functional enhancements of the network are also discussed.

Call setup time standards

Call setup time will be important in the future due to the new ways in which customers will use the network. This study presents two models to estimate call setup time. One model for multi frequency (MF) and the other for common channel signalling (CCS).

Realization of a Signaling System No. 7 Network for AT&amp;amp;T

Transition of the AT&T Communications Common Channel Interoffice Signaling (CCIS) Network, currently the world's largest, to a more powerful and flexible network with Common Channel Signaling System No. 7 capability has begun with the introduction of a more powerful signaling transfer point system and high-speed data links. The evolving AT&T network will be a key element in supporting an Integrated Services Digital Network (ISDN) capability. This paper describes the status of the existing AT&T CCIS network and how it will evolve toward a new network employing Signaling System No. 7 utilizing the ISDN User part (ISDN-UP). It also considers Signaling System No. 7 ISDN-UP implementation and the flexibility of the ISDNUP protocol in support of future customer needs.

An Overview of Signaling System No. 7

When it was first approved by the CCITT in the 1980 Yellow Book, Signaling System No. 7 was described as "an internationally standardized general purpose Common Channel Signalling (CCS) system: <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">\bullet</tex> optimized for operation in digital telecommunications networks in conjunction with stored program controlled exchanges; <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">\bullet</tex> that can meet present and future requirements of information transfer (circuit and non-circuit related) for inter-processor transactions within telecommunications networks for call control, remote control, network data base access, and management and maintenance signalling; <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">\bullet</tex> that provides a reliable means of information transfer in correct sequence, without loss or duplication." It then consisted of a three-level message transfer part (MTP-for connectionless message transfer), a telephone user part (for analog call setup and control), a data user part (for analog circuit switched data), and a four-level architectural model with a "fuzzy" relation to the OSI seven-layer model. By 1984, in the Red Book, the MTP had matured considerably (especially in the area of congestion control), a new level had been added to provide additional transport functionality (the signaling connection control part or SCCP), an ISDN user part provided call control for digital facilities, and the architectural model had been "adjusted." Future efforts are focusing on cod-to-end ISDN signaling compatibility (harmonization of SS7 and <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">D</tex> -channel procedures), non-circuit-related transaction capabilities (e.g., for network database interactions), a complete operations and maintenance application part (OMAP), and a more formal architectural relationship with the OSI model.

Implementing ISDN in the United States

Planning for implementation of ISDN is proceeding at a rapid rate throughout the United States. Planning for nationwide deployment of common-channel signaling to support database access, as well as internode signaling for ISDN is also underway. This paper describes planning for trials and initial applications of ISDN and common-channel signaling for service starting in late 1986 through early 1988, as well as ISDN demonstrations, some already in operation. In addition, this paper discusses the network and regulatory environment for ISDN implementation in the United States, standards for the U.S. environment, and trials of transition services.

The Role of ISDN in AT&amp;T Information Systems Architecture

AT&T Information Systems Architecture defines a framework for compatibility among AT&T products as well as with key products of other vendors. A key direction of Information Systems Architecture is the use of standard, open interfaces and protocols. Standards now being defined for the Integrated Services Digital Network (ISDN) play an important role in the architecture. Support of ISDN will provide customers with uniform access to integrated voice and data capabilities which are provided through digital transmission and common channel signaling. Support of ISDN within Information Systems Architecture promises to provide customers with compatibility and high functionality. The AT&T Information Systems PBX product family already supports many capabilities that provide ISDN functionality. These capabilities make incorporation of ISDN in Information Systems Architecture and full support of ISDN a direct step in product evolution.

Selection method for both‐way circuit groups between multiunit offices

AbstractIntroduction of common channel signaling system makes the both‐way circuit operation easy and therefore efficient operation of communication network is expected. An effective selection method is required for the circuit groups with both‐way circuit operation between multiunit offices in order to avoid service degradation in traffic between the offices caused by improper selection method at one side. In this paper, we propose new selection methods which make use of the number of idle circuits and the idle probability of circuit groups. We also clarify the effectiveness of these methods by a comparison with existing methods, e.g., the method of selecting a circuit group in proportion to the number of idle circuits in each group, etc., that had been used in oneway circuit operation, from the viewpoint of traffic characteristics.

Considerations for ISDN planning and implementation

THE INFORMATION AGE has created such a diversity between the Communications needs of the business user and the residential Community that one common-denominator public telephone network can no longer serve everyone. The time when evolutionary network enhancements can be justified and implemented will come too late to be acceptable to a large body of business users, because of this diversity of needs. The emerging proliferation of technological bypass of local telephone facilities in the United States is symptomatic of the need for one or more shared wideband/ broadband overlay networks to serve the business community. This environment requires accelerated introduction of digital technologies in the telephone network for provision of high-speed end-to-end digital services including data, facsimile, and video. This necessitates the use of Overlay facilities and networks to meet present business customer demands until the loop plant in the common-denominator network can evolve to optimally meet the varied demands of the whole community. This paper describes past progress and current plans for the introduction of digital technologies for switching, interexchange trunking, and the local loop for an end-to-end digital network. The paper also discusses the implementation of common-channel signaling, based on CCITT's SSN07 in the circuit-switched network, as well as the use of an overlay packet-switched network for provision of data commumcations and videotex services.

Stored Program Controlled Network: Overview

This paper describes the evolution and architecture of the Stored Program Controlled (SPC) Network. The critical role of common-channel interoffice signaling (CCIS) is discussed, both as an improved method for providing the traditional signaling functions, and as the key to a wide range of new service opportunities. These are made possible by the ability to interrupt call progress and, in real-time, interrogate a distant data base and modify the subsequent call handling based on the information returned. The underlying architecture by which these services are implemented is based on the objectives of providing ubiquitous service with limited deployment of essential network capabilities and creating a structure which permits customized services by modifying the contents of a centralized data base.

Stored Program Controlled Network: Prologue

The rapid introduction of electronic switching systems with Stored Program Control (SPC) has made possible the interconnection of the control processors by high-speed data links to provide common-channel interoffice signaling (CCIS). Not only does this permit higher-speed, lower-cost, more reliable setup of connections, but also the transfer of packets of information for more flexible call control. The papers in this issue describe the evolution of the SPC network concept since the introduction of CCIS in 1976 and the first new services which will exploit the power of this new network capability.

Stored Program Controlled Network: Generic Network Plan

The network of stored program control communication processors interconnected with common-channel interoffice signaling (CCIS) is commonly referred to as the Stored Program Controlled (SPC) Network. The SPC network will result in new call handling and routing improvements and in new network-based services. It is desirable to tailor the services to meet special customer needs and to deploy them rapidly. A generic plan is described which provides a basis for building services from basic functional capabilities that are deployed in network action points and controlled by network control points. Terminating-end office features can be used to provide additional customer service options. Thus, service for a customer can be composed of sequences of actions stored at appropriate network central points using basic switching capabilities deployed in the network. As needs for customer service evolve, new capabilities can be added to the repertoire of existing capabilities. By equipping key nodes with the capabilities described, the generic plan will also allow the SPC network to evolve efficiently to meet future customer needs.

Stored Program Controlled Network: Routing of Direct-Signaling Messages in the CCIS Network

This paper compares and contrasts the two methods currently used to route messages through the common-channel interoffice signaling (CCIS) network. Since its introduction in 1976, the CCIS network has been providing routing of telephone signaling messages between switching offices using permanent virtual circuits. In 1980, a new datagram routing capability, called direct signaling, has been added that significantly enhances the network's ability to interconnect Stored Program Control (SPC) systems. Stored program control systems interconnected by the signaling network can now communicate in support of improved SPC network services in addition to CCIS trunk-related call-control signaling. This paper briefly reviews banded telephone routing and then describes and compares direct signaling routing. The new flow control procedures required to implement direct signaling are discussed and two examples of applications using direct signaling are presented.

Stored Program Controlled Network: NO. 1/1A ESS-SPC Network Capabilities and Signaling Architecture

The No. 1/1A Electronic Switching System (ESS) will play an important role in the evolving Stored Program Controlled (SPC) Network because, as a major electronic switching system for local and combined local/toll service, it provides direct interfaces to many of the Bell System's customers. It provides important capabilities required for System 800 Service and for a variety of other new SPC network services. This paper describes several of the basic SPC network capabilities provided by the No. 1/1A ESS. It also describes the architecture and implementation of its common-channel interoffice signaling (CCIS) subsystem, CCIS call-processing software, and System 800 software.

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.

Control and Supervision of Remote Line Units

The ITT 1210 Class 5 digital switching system has a distributed control architecture with inherent remote line switching capability. A unique common channel signaling scheme permits control and supervision of these remote units. Testing and maintenance capabilities are, in general, identical and equivalent to those available in the 1210 host office. The Technical Assistance Center provides an extra overview level of backup maintenance for on-line assistance to personnel in any operational 1210 system.

Effect of Echo Canceler on Common-Channel Interoffice Signaling Continuity Check

Annoying echoes generated by impedance mismatches can occur in long-distance telephone networks. An echo canceler controls echo by synthesizing an echo replica and subtracting it from the actual echo on the return path. For the echo canceler to work properly, it must be able to distinguish between desired signals and echoes. One instance where this can be difficult is during the common-channel interoffice signaling (CCIS) continuity check between four-wire switching offices. On OCXS trunks the voice and the signaling are routed separately. To ensure a satisfactory transmission path, a voice path continuity check is conducted before call setup. The check is performed on a loop basis by sending a check tone and looping it back at the distant office. Since the echo canceler adaptive filter memorizes information from the last previous call, it may partially cancel the looped-back tone. In this paper we study the effect of the echo canceler adaptive memory on the CCIS continuity check. The analytical and experimental results indicate that the occurrence of continuity check failure caused by the presence of an active echo canceler is so infrequent and insignificant compared to the existing statistics of all other pertinent failure mechanisms. Thus, disabling the echo canceler during the CCIS continuity check is unnecessary.

Structure of the common channel signalling network

This paper presents the results of a research on the organisation of common channel signalling network CCITTn∘ 7 for the French network. It proves that for economical and reliability reasons, one should choose a structure with an assignment of each signalling point to the two transfert points with which its traffic affinity is greater, instead of the classical duplicated transfer point structure.