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     

七号信令网MTP3层安全机制分析

七号信令网络由于缺乏安全机制而存在诸多安全漏洞。通过分析攻击者如何利用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,从而实现了信令节点间的相互认证和对消息的完整性保护,增强了七号信令网络的安全性。     

天津网通七号信令集中监测系统

七号信令网是电信网的重要组成部分,其运行质量直接影响到电信网及各种新业务的稳定运行和经济收益。七号信令集中监测系统通过直接采集七号信令的原始数据进行分析处理,提供对七号信令网实时动态监测,以及各种用户信令的各种微观分析。章在分析七号信令集中监测系统框架的基础上,对监测系统的组网结构、系统功能、软件应用做了进一步的研究。     

Isolating faulty routing tables in SS7 networks: present and future

The author presents the standardized method used to isolate faulty routing tables in SS7 packet switched networks, and suggests an alternative for the future. The present method used has a drawback: the extra load it induces on the network. Furthermore, it requires the audit logic, with its associated software packages, in all the SS7 nodes. The alternative suggested by this article does not induce any extra load on the network. It does not require any special audit logic in the SS7 nodes. However, it requires a TMN infrastructure. There is no doubt that TMN will gradually become a reality. But before TMN products are available on a large scale, SS7 network operators will have to do with the existing method. Routing tables can be audited using the existing method, but extra care is needed in order to avoid overloading the network. Audits therefore have to be done with circumspection. They need to be carefully scheduled, especially when used to test periodically and thoroughly all the routing tables of an SS7 network     

Signaling System No.7 local exchange deployment

The author examines the deployment of Signaling System No.7 (SS7) from the viewpoint of the local exchange carrier. The three phases of local exchange deployment-service planning and design, local exchange network design, and interconnection design-are discussed in sequence. SS7 is a fundamental change to the infrastructure of the local exchange telecommunications network. The author describes how the backbone network, centered on the signaling transfer points (STPs), is installed first, followed by the local exchange network, and then interconnection to interchange and other networks     

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     

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     

PSTN与IMS间网关信令转换研究与实现

随着网络技术及通信技术的快速发展,传统电信网络与下一代网络之间的互通成为一个很热门的话题.网络互通的主要问题之一是承载协议的相互转换,网关提供了一种信令转换的桥梁.从此问题出发分析了PSTN网与IMS网问的互通,并对两网络中的相关协议(SS7和SIP)展开讨论,提出了一种互通模型,提供了一套在实际项目中证明可行的实现方案.     

WCDMA核心网信令系统对七号信令网的影响

BICC和GCP是第三代移动网络中必不可少的信令,主要支持的承载网络是ATM和IP,许多厂商也侧重开发ATM和IP传输技术。在中国未来几年逐渐开展3G移动业务后,GSM网络的业务也可以逐渐连接到3G核心网络中,GSM也会支持分层网络,使用比STM更经济的IP作为传输,原来七号信令网络中的流量就会逐渐减少。在设计3G七号信令网络时,需要考虑3G网络信令对传输的要求,为将采用的新技术进行准备。     

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     

Error monitoring issues for common channel signaling

Motivated by field data which showed a large number of link changeovers and incidences of link oscillations between in-service and out-of-service states in common channel signalling (CCS) networks, a number of analyses of the link error monitoring procedures in the SS7 protocol were performed by the authors. This paper summarizes the results obtained thus far and include the following: (a) results of an exact analysis of the performance of the error monitoring procedures under both random and bursty errors; (b) a demonstration that there exists a range of error rates within which the error monitoring procedures of SS7 may induce frequent changeovers and changebacks; (c) an analysis of the performance of the SS7 level-2 transmission protocol to determine the tolerable error rates within which the delay requirements can be met; (d) a demonstration that the tolerable error rate depends strongly on various link and traffic characteristics, thereby implying that a single set of error monitor parameters will not work well in all situations; and (e) some recommendations on a customizable/adaptable scheme of error monitoring with a discussion on their implementability. These issues may be particularly relevant in the presence of anticipated increases in SS7 traffic due to widespread deployment of advanced intelligent network (AIN) and personal communications service (PCS) as well as for developing procedures for high-speed SS7 links currently under consideration by standards bodies     

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     

JAIN protocol APIs

JAIN envisions the creation of a number of Java APIs that abstract the details of networks and protocol implementations, and allow for the development of portable applications. The JAIN Protocol Experts Group (PEG) will focus on developing Java APIs for protocols used in telephony, INs, wireless networks, and the Internet. The PEG is organized into an SS7 subgroup and an IP subgroup. The article provides an introduction to PEG. It next describes the JAIN SS7 APIs. It then describes the JAIN IP APIs. The article also explains how JAIN SS7 and IP APIs can be leveraged for the converged SS7-IP networks of the future and describes the JAIN PEG roadmap     

Performance analysis of SS7 congestion controls under sustainedoverload

Congestion controls are a key factor in achieving the robust performance required of common channel signaling (CCS) networks in the face of partial network failures and extreme traffic loads, especially as networks become large and carry high traffic volume. The CCITT recommendations define a number of types of congestion control, and the parameters of the controls must be well set in order to ensure their efficacy under transient and sustained signalling network overload. The objective of this paper is to present a modeling approach to the determination of the network parameters that govern the performance of the SS7 congestion controls under sustained overload. Results of the investigation by simulation are presented and discussed     

七号信令中TUP的微机仿真

本文按照“中国本地网七号信号方式技术规范”要求，对我国本地网中端局至端局ＳＳ７信号扣的ＴＵＰ直达接续过程进行了实验研究。描述了采用ＰＣ／ＡＴ机实现信号可靠传送的软件设计方法，实验表明，按ＳＳ７信令来传递本地网中的电话信号是完全可行的。     

No.7信令系统的安全威胁及其防护

No.7信令系统（SS7）是公用电话网的关键支撑系统,SS7网络最初作为封闭网络来设计的,整个网络由运营商完全控制,各实体高度信任。文章分别针对该系统的信令协议、网络节点和来自外部网络的安全威胁进行了分析,并从协议安全、边界防护和内部安全加固三个方面提出了构建信令系统防护体系的方案。     

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.     

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