The role of ISDN signaling in global networks

A historical context is provided for integrated services digital network (ISDN) to give some perspective on how the current signaling capabilities have evolved. A communications architecture is introduced and used to organize the discussion of the ISDN protocols (i.e. DSS1 and SS7) and to highlight the role of signaling in the overall architecture. The architecture defines a functional partitioning of the capabilities of ISDN, which is used to compare and contrast the DSS1 and SS7 protocols and to discuss the interfaces that support global intelligent networks. The purpose is to illustrate the similarity between the DSS1 and SS7 control protocols. The likely evolution of the ISDN protocols is discussed, showing their convergence toward a single control protocol based on the International Organization for Standardization (ISO) protocols     

Implementation of SS7: Italtel's experience

Field results in implementing Signaling system No.7 (SS7) in preparation for the introduction of intelligent network (IN) services are reported. Besides implementing SS7 for interexchange trunk signaling, Italtel has adapted it for communications with remote units, i.e. remote switching modules and subscriber multiplexers and concentrators. IN implementation in a distributed system is discussed. The distributed architecture of the Linea UT intelligent network is described     

Current role and future evolution of the ISDN Signaling system inNTT's network

The current role of the integrated services digital network (ISDN) Signaling System is examined, covering general features of the ISDN protocol, functionalities supporting ISDN services, and functionalities supporting existing services. The Signaling System No.7 (SS7) network and its operation are described. The future evolution of the ISDN signaling system is discussed     

Signaling System No.7 in corporate networks

Corporate network user requirements are identified. The significance of Signaling System No.7 (SS7), in corporate network as a separate backbone signaling system for implementing a robust, flexible and transparent communication network is discussed. The architecture for a corporate network utilizing enhanced signaling is described. The use of SS7 instead of the integrated services digital network primary rate interface (ISDN PRI) is explored. Some SS7 applications in corporate networks are examined     

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     

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     

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     

Capacity and performance analysis of signaling networks inmultivendor environments

The load of common channel signaling networks is being increased through the introduction of new services such as supplementary services or mobile communication services. This may lead to a performance degradation of the signaling network, which affects both the quality of the new services and of the services already offered by the network. In the paper, a generic modeling methodology for the signaling load and the signaling network performance as a result of the various communication services is extended in order to include certain implementation-dependent particularities. The models are obtained by considering the protocol functions of Signaling System No. 7 as specified by the CCITT, as well as the information flows through these functions. With this approach, virtual processor models are derived which can be mapped onto particular implementations. This allows the analysis of signaling networks in a multivendor environment. Using these principles, a signaling network planning tool concept has been developed which provides the distinct loading of hardware and software signaling network resources, and on which hierarchical performance analysis and planning procedures are based. This allows to support the planning of signaling networks according to given service, load, and grade-of-service figures. A simple case study outlines the application of the tool concept to a network supporting Freephone, Credit Card, and ISDN voice services     

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.     

Consideration on common channel signaling evolution for globalintelligent networking

With the evolution of digital networks and intelligent network (IN) capabilities, the role of common channel signaling has become more and more important. In respect to IN, common channel signaling would play a significant role not only inside one network but also over multiple networks. International credit card validation and internetworking for digital mobile services represented by GSM (Global System for Mobile Communications) are examples which utilize internetwork signaling capabilities in the framework of the initial-phase IN. Enhanced service providers (ESPs) may access the public network through the common channel signaling interface to make use of the IN capabilities, as is being discussed in terms of ONA (open network architecture) or ONP (open network provision). This paper first identifies various scenarios where internetwork signaling interactions would take place in the framework of IN in the forthcoming era. It then identifies various requirements to cope with these scenarios. It finally discusses the directions for evolution of common channel signaling toward global intelligent networking     

Performability analysis of common-channel signaling networks, basedon signaling system 7

Within integrated services digital networks (ISDN), all inter-change signaling messages for ISDN and intelligent network (IN) call controls are carried through a common channel signaling network (CCSN) as a backbone signaling network. Since CCSN usually have very strict reliability requirements as well as good performance objectives, performance and reliability of CCSN need to be jointly analyzed. This paper evaluates the mean end-to-end delay of a single-mated pair (SMP) CCSN for various call-arrival rates in a normal state and several failure states, as a performance index. As a performability index, this paper also analyzes the mean time to unreliable operation (MTUO) of a given network for various call-arrival rates at each signaling end point (SEP) and the failure rate of each signaling transfer point (STP). These results can be used in the design of common-channel signaling networks. This performability evaluation can be further studied for varying the failure rates of SEP and linksets, and the various threshold values of the unreliable operation     

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     

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.     

New directions in signaling for broadband ISDN

User networks signaling is considered. The evolution of signaling protocols is outlined, analyzing the forces producing changes in the past. Emerging broadband switching technologies and services are discussed, emphasizing capabilities that might be required. A conceptual model for representing integrated-services digital network (ISDN) calls is presented as the basis for structuring a more flexible signaling protocol to meet the needs for a broadband environment     

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     

Common channel signaling: the nexus of an advanced communicationsnetwork

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     

Japanese subscriber loop network and fiber optic loop development

Japanese local-loop networks are addressed with a special focus on ISDN and fiberoptic systems deployment. Basic telecommunication services and local network evolution in Japan are reviewed, and the various types of loop transmission systems in existence are described. Future networks and systems development are discussed     

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     

Progress Towards User Access Arrangements in Integrated Services Digital Networks

This paper deals with arrangements for local access to emerging Integrated Services Digital Networks (ISDN's). The ISDN concept is here introduced as the focal point for the ongoing international activity on multiservice digital networks. ISDN's are conceived as networks which have evolved from the basic digital telephone networks and they will provide end-to-end digital connectivity to support a wide range of services including voice, data, sound, and video applications. After giving a general outline of the evoving ISDN network scenarios for digital communications, the paper reviews the international trends on user access arrangements in terms of 1) user equipment and interface configurations, 2) access channel structures and information transfer capabilities, 3) local distribution plant configurations (with emphasis on the copper plant), and 4) access protocols.     

七号信令在现代通信中的应用

七号信令是国际标准化公共信道信令，介绍了七号信令的网络结构和功能结构，及其在公用电话网(PSTN)／综合业务数据网(ISDN)、移动通信网和智能网中的应用。随着现代通信网的快速发展，七号信令有必要引入高速信令链路以解决网络拥塞问题，同时对第三代移动通信系统将影响到现有七号信令的网络结构与协议，七号信令也要与下一代IP网络的融合，以实现电信网与下一代网络体系的互通等问题进行了进一步探讨。