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     

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: 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     

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     

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     

基于NGN的一号数字用户信令系统的研究

ISDN业务在当前的电信网络中应用广泛,因此在NGN网络中实现ISDN业务非常必要。一号数字用户信令——DSS1是ISDN业务实现的基础,本文分析了在NGN网络中实现DSS1的必要性,并对NGN网络中实现DSS1信令系统的原理进行了详细研究,提出了DSS1信令系统的实现模型,最后对DSS1的实现过程进行了详细介绍。     

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     

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     

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     

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:bulletoptimized for operation in digital telecommunications networks in conjunction with stored program controlled exchanges;bulletthat 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;bulletthat 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 andD-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.     

Object-oriented design of ISDN call-processing software

The development of object-oriented programming (OOP) software for a prototype switching system, including the DSS1 protocol on integrated services digital network (ISDN) subscriber signaling and the ISDN user part (ISUP) for network signaling, is discussed. The major goal of the project is to determine whether switching system software can be clearly structured by using the rules of OOP, and whether the use of OOP concepts leads to an improvement in productivity and quality for large software systems. The standard classes, application classes, class hierarchy, and layer model with the OOP project are described. The experiences in applying OOP for the development of switching system software are summarized     

A signaling architecture for wireless ATM access networks

A multiservice wireless Asynchronous Transfer Mode (ATM) access system is considered from a signaling protocol viewpoint. In an attempt to generalize and extend results and experiences obtained from the specification, design, and implementation of fixed ATM‐based access networks, we extend the concept of the broadband V interface (referred to as VB) for application to wireless ATM access networks. The proposed architecture follows the signaling structure of Broadband ISDN (B‐ISDN) User–Network Interface (UNI), thus offering the possibility for integration of the wireless ATM access system into fixed B‐ISDN. It is shown that the use of the proposed access signaling architecture provides cost effective implementations without degrading the agreed Quality of Service (QoS), and simplifies call/connection and handover control. The evaluation of the proposed access signaling protocol structure yields results that fall within acceptable ATM signaling performance measures. A performance comparison of our approach with an alternative access signaling configuration is also carried out to quantify the relative gains. This revised version was published online in August 2006 with corrections to the Cover Date.     

A control mechanism to prevent correlated message arrivals fromdegrading Signaling No. 7 network performance

Signaling System No. 7 (SS7) is designed to provide a connectionless transfer of signaling messages of reasonable length. Customers having access to user signaling bearer capabilities as specified in the ANSI T1.623 and CCITT Q.931 standards can send bursts of correlated messages (e.g., by doing a file transfer that results in the segmentation of a block of data into a number of consecutive signaling messages) through SS7 networks. These message bursts with short interarrival times could have an adverse impact on the delay performance of the SS7 networks. A control mechanism, credit manager, is investigated in this paper to regulate incoming traffic to the SS7 network by imposing appropriate time separation between messages when the incoming stream is too bursty. The credit manager has a credit bank where credits accrue at a fixed rate up to a prespecified credit bank capacity. This paper presents simulation results showing delay performance of the SS7 ISUP and TCAP message traffic with a range of correlated message traffic, and control parameters of the credit manager (i.e., credit generation rate and bank capacity) are determined that ensure the traffic entering the SS7 network is acceptable. The results show that control parameters can be set so that for any incoming traffic stream there is no detrimental impact on the SS7 ISUP and TCAP message delay, and the credit manager accepts a wide range of traffic patterns without causing significant delay     

Role of ISDN signaling for a satellite system with on-boardprocessing

The onboard processing (OBP) system, as currently being developed by the European Space Agency, ensures full satellite/ISDN compatibility for worldwide ISDN service operation. The authors present various arguments for opting for the international standard ISDN signaling scheme, propose several alternatives for effective interworking between different applications supported by the OBP system, and address an efficient method to transport DSS1 through the satellite system and to meet CCITT delay performance objectives for end-to-end connections     

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.     

Mobility management and control protocol for wireless ATM networks

The introduction of wireless ATM (WATM) in customer premises network environments necessitates the design of mobility protocols, since the existing versions of B-ISDN signaling do not support terminal mobility. Such protocols can be deployed either as extensions to the standard signaling capabilities, or as individual solutions that have little or no impact on existing infrastructures (switches, signaling software, etc.). A WATM architecture that adopts the latter approach is presented. After a discussion of the problems encountered in the integration of wireless networking and B-ISDN ATM technologies, a mobility management and control (MMC) protocol is proposed. Finally, in the framework of the proposed MMC protocol, algorithms for implementing mobility procedures (handover and registration) are described     

Assuring SS7 dependability: a robustness characterization ofsignaling network elements

Current and evolving telecommunication services will rely on signaling network performance and reliability properties to build competitive call and connection control mechanisms under increasing demands on flexibility without compromising on quality. The dimensions of signaling dependability most often evaluated are the rate of call loss and end-to-end route unavailability. A third dimension of dependability that captures the concern about large or catastrophic failures can be termed network robustness. The paper is concerned with the dependability aspects of the evolving Signaling System No. 7 (SS7) networks and attempts to strike a balance between the probabilistic and deterministic measures that must be evaluated to accomplish a risk-trend assessment to drive architecture decisions. Starting with high-level network dependability objectives and field experience with SS7 in the U.S., potential areas of growing stringency in network element (NE) dependability are identified to improve against current measures of SS7 network quality, as per-call signaling interactions increase. A sensitivity analysis is presented to highlight the impact due to imperfect coverage of duplex network component or element failures (i.e., correlated failures), to assist in the setting of requirements on NE robustness. A benefit analysis, covering several dimensions of dependability, is used to generate the domain of solutions available to the network architect in terms of network and network element fault tolerance that may be specified to meet the desired signaling quality goals     

分组网与ISDN互连的研究

非ＩＳＤＮ网与ＩＳＤＮ互连是向ＩＳＤＮ过渡的策略之一，其中ＰＳＤＮ与ＩＳＤＮ的互连占有重要地位。本文研究ＰＳＤＮ与ＩＳＤＮ互连的技术问题，在对两种网比较的基础上，文中提出了几种可能的互连方案，并讨论了互连层选择、号码制度互通、流量控制、差错控制、信令转换、信关结构等技术问题和性能分析问题。