Common Channel Signaling Research Articles

Routing and congestion control in common channel Signaling System No.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.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Evolving intelligent interexchange network-an SS7 perspective

The role of common channel signaling, referred to as Signaling System No.7 (SS7), in the evolution of services in an interexchange carrier environment is discussed. The importance of SS7 in evolving the intelligent network necessary to support these services is addressed. Interworking with virtual private networks via the out-of-band ISDN messaging channel (D-channel) to extend the capabilities of SS7 network signaling to customer networks is also discussed. For ubiquitous support of ISDN, CLASS, and future services, the interworking of interexchange SS7 with domestic local exchange carriers as well as foreign administrations is critical. This service and intelligent network evolution is described. Emphasis is placed on services and the anticipated migration to those types of services which demand an intelligent interaction and close coupling of both virtual private networks and local public switched networks to the interexchange network. >

Signaling System No.7, IS-41 and cellular telephony networking

Globally, the common channel Signaling System No.7 (SS7) has grown and matured over the past five years in two directions. Outside of the US, the development of CCITT Signaling System No.7 (C7) has grown largely due to the need for modern call completion capabilities in national telephone networks. Within the US, SS7 has evolved from the need to provide fast and reliable database services to the support of the custom calling features to the local exchange carrier (LEC) networks. The 1990s will further accelerate the requirements for network solutions to customer needs, especially in the rapidly growing cellular telephony industry. These network solutions are forcing the merger of call delivery and database services in both the SS7 and C7 worlds. The issues, concerns, and difficulties with the merger of these functions are discussed. >

Common Channel Signalling

Common Channel Signalling

Common-Channel Signalling

Common-Channel Signalling

Common channel signalling system number 7 for ISDN and intelligent networks

Various functional parts of signalling system number 7 and the underlying concepts are described. The unique attributes of the lower and higher functional layers are discussed. Applications of signaling system number 7 for call control and for transaction services are presented. The signaling transfer point makes signalling networks possible. Using the lower layers of the protocol, it provides routing capability for signaling messages between the exchange offices and access of these exchange offices to the network databases. The author discusses the performance parameters associated with the signalling transfer point and examines its implementations.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

The intelligent network-changing the face of telecommunications

The realization of the intelligent network concept is traced, first in the former Bell System in the early 1980s, and subsequently in the Regional Operating Companies, post divestiture. The history of common channel signaling and the introduction of 800 Service, Calling Card Service, and Private Virtual Network Service are described. The network nodes and operations systems that are the major components of the intelligent network are introduced, and their potential application for a wealth of voice, data, and video services is suggested. The next generation of the intelligent network, called the advanced intelligent network, which through its service-creation capabilities holds promise for rapid service development and a cornucopia of customized services, is described.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Introduction of flexible routing for international networks

This paper summarizes a deployment strategy for flexible routing in international networks. In an earlier paper, we proposed to define flexible routing for international networks based on Dynamic Nonhierarchical Routing call processing principles, including originating call control, common channel signaling and crankback capabilities, and investigated the problem of dimensioning multiservice bilateral networks assuming that flexible routing is introduced by both international carriers. In reality, however, there will be a period of transition in which most administrations will continue to design and manage international networks based on traditional hierarchical routing principles. Thus, we show that by combining flexible routing with trunk reservation, we can introduce flexible routing unilaterally in such a way that it will result in more robust and cost-effective netowrk provisioning for both international carriers.

Alternatives and issues for network signaling transport in a broadband environment

The reliable transport of signaling information is fundamental to telecommunications networks. Common channel signaling for public telephone networks is currently based on CCITT Signaling System No. 7. The issues addressed in this paper deal with how signaling transport could be provided in Broadband ISDN (BISDN) networks using Asynchronous Transfer Mode (ATM). Different methods for signaling transport are considered, the criteria to be used in selecting a method of transport are identified, and problems that need to be studied to determine the appropriate direction to follow are formulated. The purpose of the paper is to provide a framework in which to consider various methods and determine how signaling transport protocols should evolve as networks move towards BISDN.

Integrated methodology for supporting packet network performance management and planning

This paper describes an integrated approach for supporting packet network performance management and planning. As more and more packet networks — such as the public packet switched networks, common channel signalling networks and metropolitan area networks — are being deployed in the Regional Bell Operating Companies, new network operations systems are required for planning the evolution and engineering the service performance of these traffic-sensitive packet networks. This paper describes some of the synthesis and analysis algorithms that we have designed for supporting the traffic engineering of a public packet switched network. The synthesis algorithms include network element sizing, processor load balancing, network layer window size adjustment and traffic rerouting. The analysis algorithms include network element utilization and delay estimation as well as network end-to-end delay estimation.

Common channel signaling: the nexus of an advanced communications network

An overview of BellSouth's current and future common channel signaling (CCS) network is presented. The current network and its architecture are described. Network element testing and network interconnection in a multivendor, multinetwork environment are discussed. Services offered by BellSouth via the existing network are summarized. Future plans for the CSS network are outlined. These include the establishment of a target architecture that will permit the rapid introduction of a wide range of communications services in a manner consistent with the probable evolution of the market and the regulatory environment. The introduction of two BellSouth programmable nodes-the local service control point (SCP) and the ISDN service node-is described. Advanced services are highlighted.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Common channel signaling interface for local exchange carrier to interexchange carrier interconnection

Issues associated with the interconnection of common channel signaling (CCS) networks are identified. Protocol additions to support exchange access services are discussed. Possible extensions for circuit-switched services beyond basic exchange access, as well as further extensions of Signaling System No.7 to support non-circuit-associated signaling between carriers, are described. >

Telephone challenges: a plethora of services

Technical advances and changes in the regulatory climate in US telephony since the court-ordered divestiture of AT&T Company in 1984 are examined in this second of a series of articles (for previous article, by G. Zorpette, see ibid., vol.27, no.5, p.28 (1990)). A set of services based on Custom Local Area Signaling Service (Class) technology, introduced in New Jersey in 1987, provides caller identification, call block, priority call, return call, repeat call, select forward, and call trace. Throughout the USA it is being rolled out at varying clips, depending on state regulatory climates and the pace of technology upgrades in the network. Class is usually based on Common Channel Signaling System 7 (SS7) software, but can also be implemented by the Advanced Intelligent Network, which puts the control software in a computer outside the switch so that computers more powerful than switch hardware can manipulate a call. Other major trends discussed are the growing use of cordless telephones, cellular telephony, voice mail, and computers replacing human operators.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

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.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Meeting the challenge of assuring dependable telecommunication services in the '90s

Assuring the dependability of telecommunication services in the face of increasing customer expectations, revolutionary changes being made or proposed in networks, and recent disruptive disasters are discussed. Work focused on reducing vulnerability to network element outages is described and examined for three new technologies: fiber network architectures, common channel signaling, and intelligent network architectures. A comprehensive service dependability management process to be established by service providers is recommended. >

Minimum-cost dimensioning model for common channel signaling networks under joint performance and reliability constraints

The common channel signaling (CCS) network using the signaling system no.7 protocol is a special-purpose packet switching network transporting various types of network signaling messages between telephone exchanges and/or network databases. Because of the criticality of the information that is being carried, CCS networks should be highly reliable and provide fast response times. They should be dimensioned with sufficient redundancy so that the performance requirements of the networks are satisfied even when a large number of the network components fail. An efficient method is developed to calculate the joint performance and reliability measure, called performability, between an arbitrarily chosen source-destination pair of signaling points in a CCS network. An iterative optimal dimensioning procedure is developed to minimize the total link cost of the network subject to the required end-to-end performability constraints between the signaling points. Using examples, it is shown that the developed dimensioning method overcomes shortcomings of a conventional link-by-link dimensioning method. >

Assuring the dependability of telecommunications networks and services

Service dependability is defined as comprising reliability, availability, maintainability, and survivability, and the service dependability management process is addressed. A description is given of a service dependability management process intended to assure high-quality telecommunications services for ISDN, intelligent network, common channel signaling, broadband service capabilities, and other new network service concepts. Techniques for assessing network dependability are briefly considered. >

The ultimate intelligent network?

An ‘intelligent’ telecommunications network is a network that is capable of providing flexible control of its services and capabilities to both network operator and network user. The evolution to intelligent telecomunications networks began some thirty years ago with the introduction of stored programme control exchanges into the public switched network. Since then the introduction of digital switching techology, common channel signalling and network databases have advanced the concept. The evolutionary path now being followed by many network operators will lead from the universal voice telephone service we have today to a universal information service of tomorrow in which the public switched network will be able to provide any combination of voice, data and image with maximum convenience and economy.— Truly the ultimate intelligent network?

X.25 — the fulcrum for network standardization

The synchronous interface to packet switched data networks defined by the CCITT's X.25 recommendation has been in practical use for approximately ten years. Conceived and introduced amidst controversy, it has, despite its defects, more than stood the test of time. The recommendation's early history is briefly outlined, followed by a review of its development to the present day in some detail. In a wider context, the international acceptance of the standard has, in turn, contributed greatly to the success of packet switching. This wider influence is also discussed, as is the influence of X.25 in other related areas, whether Common Channel Signalling (CCS), Integrated Services Digital Networks (ISDN), Asynchronous Time-Division Switching (ATDS) or the whole Open Systems Interconnection Reference Model. X.25 is the fulcrum which has enabled the telecommunication administrations of the world to lever the computer manufacturers and users into ever greater conformance to international standards in all aspects of data networks.

Callers' perceptions of post-dialling delays: the effects of a new signalling technology

Abstract The present paper reports an investigation of the potential impact of introducing common-channel signalling (CCS) into the current telephone network. This technology would have the effect of greatly diminishing post-dialling delay (PDD). As such, its main benefits would be obtained by introducing it into the toll network, in which PDDs are much longer than in the local network. The issues examined concerned potential ‘contrast’ effects, in that reducing PDDs in the toll network may cause callers to be less patient with normal PDDs in the local network. Three laboratory studies were undertaken to evaluate caller impatience and abandonment under (1) the current system, (2) the current local system with a simulated new toll system and (3) the current toll system with a simulated new local system. Ratings of impatience and abandonment increased on local calls when the new technology was implemented on the toll network, but not vice versa. The explanation offered is based on a ‘cognitive’ contrast eff...