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     

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.     

Congestion and flow control in Signaling System No. 7-impacts ofintelligent networks and new services

Focuses on the transient performance analysis of the congestion and flow control mechanisms in CCITT Signaling System No. 7 (SS7). Special attention is directed to the impacts of the introduction of intelligent services and new applications, e.g., Freephone, credit card services, user-to-user signaling, etc. In particular, the authors show that signaling traffic characteristics like signaling scenarios or signaling message length as well as end-to-end signaling capabilities have a significant influence on the congestion and flow control and, therefore, on the real-time signaling performance. One important result of the performance studies is that if, e.g., intelligent services are introduced, the SS7 congestion and flow control does not work correctly. To solve this problem, some reinvestigations into these mechanisms would be necessary. Therefore, some approaches, e.g., modification of the signaling connection control part (SCCP) congestion control, usage of the SCCP relay function, or a redesign of the message transfer part (MTP) flow control procedures are discussed in order to guarantee the efficacy of the congestion and flow control mechanisms also in the future     

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     

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 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     

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     

Analysis of the link error monitoring protocols in the commonchannel signaling network

Motivated by the excessive link status changes observed in some field operations of the common channel signaling (CCS) network, the authors provide a detailed analysis of the signaling link error monitoring algorithms in the Signaling System No. 7 (SS7) protocol. These algorithms determine when to fail a link due to excessive error rates and when to put a failed link back into service. The analysis shows that, under current SS7 specifications of the error monitoring algorithms, the probability of a signaling link oscillating in and out of service could be high, depending on the traffic load, signal unit size, and the statistical nature of errors (bursty or random). The link oscillation phenomenon could become worse as longer Transaction Capability Application Part (TCAP) messages for transaction-based services (e.g., 800 Service) are carried in the CCS networks. While the risk to the existing network may not be high due to the light loads carried at present, there is still a need to study the error monitoring issues thoroughly     

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     

A satellite switched CDMA system for fixed service communications

Satellite-switched code-division multiple access is a system proposed for geostationary fixed satellite service. SS/CDMA provides both multiple access and switching to a multibeam satellite. In this article we present the system architecture and performance. The SS/CDMA consist of the common air interface (CAI) and the onboard code switching mechanism. The CAI provides signaling control and traffic channels. Traffic channel access and modulation is based on a spectrally efficient CDMA scheme. The satellite code-division switch (CDS) routes calls from an uplink to a downlink beam without onboard demodulation and channel decoding. This system operates with demand assignment control; that is, channel bandwidth and switch connections are only assigned per user request. The system can offer a wide variety of bit rates with wireline quality of service. The services provided are circuit-switched calls for voice data and video, and packet-switched for data. As shown, the proposed SE-CDMA can achieve high capacity and very low bit error rates at low signal-to-noise ratio. Also, the innovative switching technique can provide low complexity and achieve high throughput for all services     

七号信令网中基于MTP3层的安全机制研究

七号信令系统作为电信网络的神经系统,其安全问题日益严重.给出了SS7网络面临的主要安全威胁,分析了攻击者利用网络缺乏认证机制,通过MTP3层的网络管理消息对七号信令网实施攻击.提出用密钥交换协议和认证头协议对MTP3层进行安全保护,增强SS7网络的安全性.     

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     

线性多用户检测器的软件无线电实现

无线多媒体通信的实现要求对不同种类业务提供不同的服务质量（ＱｏＳ）,文章将软件无线电技术应用于无线通信系统中,通过现场可编程门阵列（ＦＰＧＡ）和数字信号处理器（ＤＳＰ）的配合实现ＤＳ－ＣＤＭＡ系统的线性多用户检测。可以根据业务要求与信道状况调整线性滤波器抽头值,从而动态选择检测器类型,在算法复杂度和性能上求得平衡。仿真结果给出了４种线性多用户检测器对用户数及信噪比变化的性能比较。     

中国信息处理系统发展建议

信息处理系统(MHS)位于开放系统互连(OSI)基本参考模型的最高层。它基于存储转发方式,可快速、准确、安全、可靠地完成信息的处理和传送,并可处理各种类型的信息客体,为用户提供丰富的服务。中国的MHS是一个很大的系统工程,要求有关部门统一管理、统筹安排。     

Threshold-based congestion control for the SS7 signaling network inthe GSM digital cellular network

This paper considers the congestion control scheme for the SS7 signaling network in the group special mobile (GSM) digital cellular network. This congestion control scheme is based on monitoring the SS7 link buffer occupancy. In this scheme, a congestion onset message is sent to the user parts of the SS7 network when the buffer occupancy exceeds a certain threshold, and, subsequently, a congestion abatement message is sent when the buffer occupancy goes below another threshold. Upon receipt of the congestion onset message, the user parts are expected to “intelligently” throttle the user traffic (reduce the traffic rate) so as to yield speedy recovery from congestion. Subsequently, on receipt of the abatement message, the user traffic is restored to precongestion levels. This paper primarily proposes appropriate choice of throttles and an algorithmic procedure to size the thresholds so as to yield good performance during congestion. The paper also addresses some implementation issues related to the throttles. Finally, it considers the effects of delays for the onset and abatement messages in reaching the user parts on the performance and parameters of the congestion control scheme     

一种基于IMS域的移动增值新业务:PoC

文章介绍了一种基于IMS域的移动增值新业务:无线一键通(PoC)业务,讨论了其实现方案,并对典型PoC业务的SIP信令交互流程进行了描述.在对PoC技术的优缺点进行分析的基础之上,文章探讨了未来PoC业务的用户定位问题,得出结论:企业级用户群、社团用户群以及主要由白领和青少年组成的个人用户群将是PoC业务的市场主体.文章认为PoC系统完全可以充当彩信、即时消息、状态呈现、图片收发等众多新业务的工具,将像短信业务那样,最终形成终端厂商、设备厂商、服务提供商、运营商合作共赢的PoC产业价值链.     

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     

基于MPC8260MCC的MTP2协议的实现

在E1收发器MT9075实现信令数据链路级功能的基础上,按照MPC8260的MCC的7号信令模式处理E1信令,实现MTP2协议。重点说明了初始化MCC信道为7号信令信道的流程和实现的功能。将此信令处理方案应用于E1接口板,实验证明可以实现MTP2协议,同时为7号信令信令网级和用户级功能的实现提供了信令处理平台。     

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     

Common channel signaling interface for local exchange carrier tointerexchange 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