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

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     

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 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 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.     

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     

Traffic routing and link dimensioning in the common channel signaling networks

Signaling can be defined as the exchange of information specifically concerned with the establishment and control of connections, and with network management, in a telecommunications network. It constitutes the command/control infrastructure of the modern telecommunications networks. The Common Channel Signaling (CCS) network not only forms the foundation for control and management in the modern telecommunications environments but also provides database transaction processing capability for special services such as the 800 Service and Alternate Billing Service (ABS). The CCS network is the backbone for providing the Integrated Services Digital Network (ISDN) signaling, the Advanced Intelligent Network (AIN) services, and the Personal Communications Service (PCS). It is therefore critical to provide adequate switching and transmission (link) capacities so that performance of CCS networks can be ensured. This paper describes a flexible link set dimensioning algorithm for supporting CCS network and traffic engineering. We first show that increasing a link set by one or more links may not always increase the link set capacity accordingly because of the current routing procedure defined in the Signaling System No. 7 (SS7) protocol. We then demonstrate a theorem that enables us to construct the number of all possible meaningful links in a CCS link set. Based on the theorem, an efficient and flexible procedure for implementing the link dimensioning algorithm in software is devised to support the mechanization of the CCS network planning traffic engineering functions. Finally, we show an approach to improve the CCS link utilization efficiency and its sufficient and necessary conditions.     

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     

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     

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     

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, 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     

The role of ISDN in data networking

The integrated services digital network (ISDN) offers on-demand switched end-to-end digital connectivity over the wide area, enabling the integration of both voice and data services over a common core network. This paper considers the role of ISDN in data networking, both as the core transport network and as a means of enhancing resilience in a mixed-technology data solution, complementing other data network technologies. The issues associated with data transport based on an ISDN solution are considered, and include security, bandwidth utilisation, scalability and the management of ISDN-attached devices. Optimising the use of ISDN networks for supporting the most prevalent routed and routeing protocols is also discussed.     

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.     

Interworking IEEE 802/FDDI LANs via the ISDN frame relay bearerservice

The author presents a generic architecture for interconnecting LANs (local area networks) through the ISDN (integrated services digital network) bearer services, particularly the frame relay bearer service. The architecture is derived from the IEEE 802.1 MAC (medium access control) bridge and ISDN frame relay standards. An algorithm for MAC/ISDN address resolution that makes minimal use of the WAN (wide area network) bandwidth (which is potentially the most expensive resource) is presented. The algorithm uses a MAC/ISDN address resolution server to resolve addresses for new stations, the resolution in all other cases (e.g. stations moving from the ISDN address to another) being fully distributed. To prevent a server failure from inhibiting communication to new stations, a backup server may be provided. A practical implementation of the architecture has been found capable of supporting full throughput at ISDN hyperchannel rates (384-1920 kb/s) for all IEEE 802.3 frame lengths. Frame relay is seen as having a number of important advantages for LAN interconnection, including the following: a large number of virtual circuits available, giving the potential for a rich interconnection architecture with single-hop connections across the ISDN; and low processing overhead enabling efficient use of ISDN channels, including ISDN hyperchannels (384-1920 kb/s)     

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.     

Multipoint multimedia conferencing

The development of multipoint multimedia services for conferencing is described. The use of integrated services digital network (ISDN) as part of the work carried out in the European collaborative projects Multipoint Interactive Audiovisual Communication (MIAC) and Multipoint Interactive Audiovisual System (MIAS) is emphasized. The history of multipoint teleconferencing, the different types of multipoint conferencing systems, and protocol requirements for multipoint multimedia conferencing systems are also discussed     

Personal Access Communications System: fixed wireless local loopand mobile configurations and services

The Personal Access Communications System (PACS) supports wireline quality voice, voiceband data, digital data, and messaging services and is based on a low-power, low-complexity design. Operating environments for PACS include indoor and outdoor; fixed, low mobility, and vehicular mobility; and private and public access. PACS is a microcellular system providing high frequency reuse efficiency and thus is capable of supporting high traffic density. These attributes make PACS ideal for providing fixed wireless local loop and mobile services in moderate to densely populated areas, including developing countries. PACS mobile and fixed wireless local loop service can be offered by interfacing PACS with advanced intelligent network/ISDN switches, any traditional wireline switches, or with cellular/personal communications system mobile switching centers. The PACS air interface has been standardized by the American National Standards Institute     

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     

ISDN standardization

The history and achievements of ISDN (integrated services digital network) standardization in the CCITT are reviewed. Two of the most important developments, ISDN basic and supplementary services and broadband ISDN, are focused upon. The underlying concepts in the discussions of ISDN standardization are briefly explained