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     

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

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.     

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     

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     

Achieving timely message delivery quality-of-service in fixed and variable connectivity distributed routing networks

Variable connectivity distributed routing networks (VCDRNs) are networks designed with the goal of reliably delivering message traffic even when network connectivity (both routing node to routing node and subscriber to routing node) is continuously and unpredictably changing. A general-purpose point-to-point VCDRN which provides optimum (fewest hop) connectivity in a fixed network and adapts as network topology changes so as to automatically reroute traffic is presented. The routing algorithm includes the multimedia, multidata rate, multierror rate case. It is shown how to design the network to offer a quality-of-service (QoS) in terms of a numerical probability of successful message delivery in a specified time or to adjust the network to provide a users desired QoS on single and multihop paths. This is an important feature to users who want rapid message delivery, even as network topology changes. The case of multiple message priorities is also included. Routing knowledge is distributed by adding path and error rate information to packets as they traverse the network, without adversely impacting QoS. This methodology applies to all routing protocols that employ selective reject retransmission error control. The methodology also presents a means for comparing the performance of candidate protocols in terms of parameters meaningful to the user. While the methods presented herein are applicable to any network they are of particular value to the wireless network with limited bandwidth, high error rates, and variable connectivity, where the user wants message traffic to be delivered as fast as possible in that environment with some prior assurance as to the speed and certainty of delivery.     

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 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     

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     

一种基于GEO卫星网络的IP组网方案的设计及仿真

当前,大部分支持IP的卫星系统只是提供了一个连接地面路由器的物理通道,难以满足带宽接入、多媒体服务以及星地网络一体化等新的需求.为此,提出了一个分组传输和交换均基于IP的GEO卫星系统,采用三层路由交换的组网方案,实现了同一交换域内用户信息的链路层快速转发,以及不同交换域间用户IP信息的网络层路由交换处理.最后,研究了最简单的RIP路由协议在此GEO卫星网络中的适应性,利用OPNET仿真软件对其进行了建模仿真及结果分析.     

Sleep scheduling with expected common coverage in wireless sensor networks

Sleep scheduling, which is putting some sensor nodes into sleep mode without harming network functionality, is a common method to reduce energy consumption in dense wireless sensor networks. This paper proposes a distributed and energy efficient sleep scheduling and routing scheme that can be used to extend the lifetime of a sensor network while maintaining a user defined coverage and connectivity. The scheme can activate and deactivate the three basic units of a sensor node (sensing, processing, and communication units) independently. The paper also provides a probabilistic method to estimate how much the sensing area of a node is covered by other active nodes in its neighborhood. The method is utilized by the proposed scheduling and routing scheme to reduce the control message overhead while deciding the next modes (full-active, semi-active, inactive/sleeping) of sensor nodes. We evaluated our estimation method and scheduling scheme via simulation experiments and compared our scheme also with another scheme. The results validate our probabilistic method for coverage estimation and show that our sleep scheduling and routing scheme can significantly increase the network lifetime while keeping the message complexity low and preserving both connectivity and coverage.     

Economic analysis of robust access network architecture in two-tierdata networks

Recent studies have addressed routing and performance issues of nonhierarchical and hierarchical backbone packet networks in a unified fashion, by adopting an end-to-end mean delay objective and including a variety of practical routing constraints. The authors build on this approach to include the design of robust access networks, and they analyze the economic and robustness-related tradeoffs of several access network architectures in two-tier data packet networks. Two-tier architectures consist of an access network that homes to a high-capacity backbone network through a variety of topological arrangements. The access tier provides protocol handling and traffic concentration. The backbone tier performs high-speed transport and alternate routing under congestion/failure conditions. They identify the fundamental access network parameters that allow them to develop network designs with optimized characteristics. The analysis demonstrates the cost effectiveness of access diversity as well as the enhanced robustness it can provide even though it requires higher switch functionality and cost     

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     

软件无线电台自组网技术研究

本文对软件无线电台自组网的研究情况进行了概述,并介绍了一些关键技术的研究进展,包括网络控制管理、路由、网络资源共享、动态负载均衡、软件无线电台网互连等,描述了设计软件无线电台自组网所面临的主要问题,提供了进一步研究软件无线电台自组网的一种思路.     

Telephone challenges: a plethora of services

Technical advances and changes in the regulatory climate in US telephony since the court-ordered divestiture of AT&T Company in 1984 are examined in this second of a series of articles (for previous article, by G. Zorpette, see ibid., vol.27, no.5, p.28 (1990)). A set of services based on Custom Local Area Signaling Service (Class) technology, introduced in New Jersey in 1987, provides caller identification, call block, priority call, return call, repeat call, select forward, and call trace. Throughout the USA it is being rolled out at varying clips, depending on state regulatory climates and the pace of technology upgrades in the network. Class is usually based on Common Channel Signaling System 7 (SS7) software, but can also be implemented by the Advanced Intelligent Network, which puts the control software in a computer outside the switch so that computers more powerful than switch hardware can manipulate a call. Other major trends discussed are the growing use of cordless telephones, cellular telephony, voice mail, and computers replacing human operators     

Designing a practical ATM LAN

The adaptor cards and driver software for workstations and local asynchronous transfer mode (ATM) switches and switch control software used in an ATM local area network (LAN) system are discussed. It is shown that the ATM hardware and software components together provide services that are essential for ATM to be considered a realistic alternative to current shared-media LANs. These services include: completely transparent support for the TCP/IP protocol suite, an application programming interface for full access to the underlying ATM capabilities, support for AAL5, AAL3/4, and the null AAL, both connection-oriented and connectionless service, dynamic connection establishment or switched virtual circuits, resource reservation of guaranteed bandwidth and quality of service, full-bandwidth multicast and broadcast, virtual path and channel routing among multiple switches, automatic configuration and failure recovery, dynamic address assignment and internetwork address resolution, and network management via the simple network management protocol (SNMP)     

Information Theoretic Analysis of Proactive Routing Overhead in Mobile Ad Hoc Networks

This paper considers basic bounds on the overhead of link-state protocols in mobile ad hoc networks. Hierarchical protocols are known for their good scalability properties, and hence this paper considers a two-level hierarchical protocol. In such protocols, nodes need to keep track of shortest path information, link states and cluster membership. Two types of overheads are considered; the memory needed to store routing-related information, including link-states and cluster membership, and the control messages that need to be exchanged to keep track of the changes in the network. Memory overhead is important practically for dimensioning network nodes, while message routing overhead is important since it reduces the effective capacity of the network to carry user data (vis-a-vis control data). The scalability properties of the message routing overhead are analyzed for different modes of network scaling. Practical implications, such as optimal cluster size, average/fixed memory requirement and routing protocol parameter selections are discussed.     

我国部分进口交换机接入本地网网管系统情况

本文概要介绍Ｓ１２４０等８种进口交换机接入我国本地网网管系统的情况。     

Network control for wireless communications

Existing wireless network architectures and the increasing demand for cellular services are reviewed. Wireless network control tasks and the structure of a cellular packet switch (CPS) based on an optical fiber metropolitan area network (MAN) are described. Protocols for moving information through the MAN focusing on handoff, a crucial function of wireless networks, are discussed. The results of an analysis of switch performance as measured by capacity and the distribution of functionality are presented. Several open issues regarding the capability of the CPS to deliver telephone service to wireless terminals, including privacy and security issues, are discussed