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     

Analysis of the effects of SS7 message discard schemes on callcompletion rates during overload

The author considers the performance of a Signaling System Number 7 network when the routing processors, as opposed to transmission facilities, of signaling transfer points are overloaded. The choice of overload controls in such a situation is implementation-dependent, with an option of simply discarding messages in excess of the signaling transfer point (STP) processing capability. It is this option that is studied. Call completion performance, rather than message throughput is considered as being the primary performance measure of interest since it most accurately reflects the service provided to customers. To determine realistic call completion estimates. the authors explicitly incorporate into their analysis the effects of application-level recovery procedures and customer reattempts, both of which significantly impact the service levels achieved. In so doing, they demonstrate that message throughput can be a very misleading measure of the network's ability to provide service. The need for some form of feedback mechanism to the traffic sources that will allow them to appropriately control traffic entering the network is demonstrated     

DCNA Higher Level Protocols

This paper explains a philosophy for modeling the higher level communication functions into a network architecture for heterogeneous computer networks called Data Communication Network Architecture (DCNA), the logical structure of the architecture, and several protocols based on it. To specify higher level protocols among computers of different types, DCNA defines a logical model of a computer network consisting of three submodels: the basic model, the logical network model, and the virtual network model. The basic model represents a logical view of the network resources, e.g., processing power, files, data bases, I/O devices, and a layered structure for the basic mechanisms for accessing such resources, which incorporate the concept of sublevels as well as levels. The logical network model describes the mechanisms for unified management of network resources. The virtual network model describes the mechanisms for using network resources. The. common use of network resources, by several sets of interrelated applications is made easier by treating the logical network and the virtual network separately. These models form the basis for the stipulation of higher level protocols, such as network management protocols, message transfer protocols, virtual terminal protocols, and virtual file system protocols.     

Generic signaling protocol: architecture, model, and services

The functional architecture, connection model, and services of the generic signaling protocol (GSP) are described. GSP is a simple, yet powerful, connection management protocol for ISDN. The semantics and structure of GSP support call suspension and resumption, symmetric and asymmetric bridging, third-party `proxy' call setup, and multiple-connection multimedia calling. GSP can function as a network access, interswitch, computer-to-switch, or network configuration protocol, and it has applications in circuit-switching and packet-switching networks. An example message flow demonstrating how GSP can be used to perform third-party call setup is provided     

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     

一种基于折回点重路由的折回机制在ASON中的应用

该文提出了ASON网络中一种基于折回点重路由的折回机制,当连接发生折回时,该机制通过折回点对连接进行重路由,从而省去了折回消息发送的过程。为了实现该机制,扩展了信令消息及处理流程。搭建了15个节点的试验平台,采用了RSVP-TE、OSPF-TE及LMP等协议来实现ASON网络的控制平面。试验数据显示该机制与传统的折回机制相比较,不但节省了信令通信网(SCN)的带宽,而且节省了连接的最终建立时间。     

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     

A signaling protocol for complex multimedia services

The author introduces a signaling protocol for user applications that invokes multimedia services provided by the EXPANSE research prototype, a broadband ISDN testbed. A generic framework that flexibly accommodates a wide variety of services involving multiple parties with heterogeneous terminals is described. The author describes the generic services supported, introduces the EXPANSE call model, discusses syntax and message flow procedures, and relates EXPANSE signaling to the ISDN signaling control part (ISCP) and long-term broadband ISDN signaling work currently under study by CCITT     

Performance analysis of ATM banyan networks with shared queueing.I. Random offered traffic

The paper develops the analysis of multistage banyan interconnection networks in which the switching elements are provided with a buffer shared among all the inlets and outlets of the element. The packet transfer within the network takes place according to absence or presence of backpressure signals between adjacent stages. In this latter case four different modes for operating backpressure have been studied: local and global backpressure with acknowledgment or grant backward signaling. The paper describes three models for the analysis of these networks when loaded by a random traffic. These models are based on an increasing degree of accuracy (and hence of complexity) in the representation of the state of the generic switching elements. The accuracy of these models in evaluating the network performance is assessed in the paper also in comparison with the results given by previously proposed models     

SDN-based architecture for providing quality of service to high-performance distributed applications

The specification of quality of service (QoS) requirements in most of the existing networks is still challenging. In part, traditional network environments are limited by their high administrative cost, although software-defined networks (SDNs), a newer network paradigm, simplify the management of the whole network infrastructure. In fact, SDN provides a simple way to effectively develop QoS provisioning mechanisms. In this sense, we explore the SDN model and its flexibility to develop a QoS provisioning architecture. Through the use of our new architecture, network operators are able to specify QoS levels in a simple way. Each individual data flow can be addressed, and the architecture we propose also negotiates the QoS requirements between the network controller and applications. On the other hand, the network controller continuously monitors the network environment. Then, it allocates network elements resources and prioritizes traffic, adjusting the network performance. We evaluate the feasibility of our QoS provisioning mechanism by presenting three experimental setups under realistic scenarios. For example, for a given scenario where we evaluate file transfers, our results indicate that the additional SDN modules present negligible overhead. Moreover, for a given setup, we observe a reduction of up to 82% in the file transfer times.     

The role of signaling in quality of service enabled networks

In this article we identify the common building blocks that enable some networks to provide better than best-effort transfer guarantees to the traffic they carry. We consider the role signaling plays in such a network and argue in favor of pinned routes, with a highly efficient pinning process, to improve network stability and to ease the task of maintaining QoS guarantees in the face of changing network characteristics, including failures; the use of broad QoS classes to determine the path that a particular flow should follow through the network; and providing the flexibility of specifying the detailed QoS for the flow, if needed, at any arbitrary time during the life of the flow. We conclude that a flexible signaling architecture is an essential enabling component of any QoS-aware network. We present an overview of the design and implementation of UNITE, as an example of a signaling architecture that embodies these attributes. More generally, we consider the relationship between QoS-related signaling and other protocols and mechanisms that may form part of an overall QoS-enabled network and service infrastructure     

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.     

基于业务分布的传送网网络预警分级机制的应用

传送网运行状况的优劣，直接影响其提供业务的能力，因此应避免一个SDH环上不同复用段同时出现故障点而导致业务中断。方法是当传送网某一点发生故障导致网络安全性降低时，网管中心向网络其他部位的维护者发送警示信息。告知网络上已经发生故障，提醒其他部位的维护者对自己负责维护的区段重点保障。通过对多点故障造成网络业务中断的情况进行评估，得出预警的重要性级别，并结合网络历史运行数据对预警分级修正。从而提高传送网络承载业务的安全可靠性。     

A Dual Ring Connectivity Model for VANET Under Heterogeneous Traffic Flow

Vehicular ad-hoc network (VANET) is characterized as a highly dynamic wireless network due to the dynamic connectivity of the network nodes. To achieve better connectivity under such dynamic conditions, an optimal transmission strategy is required to direct the information flow between the nodes. Earlier studies on VANET’s overlook the characteristics of heterogeneity in vehicle types, traffic structure, flow for density estimation, and connectivity observation. In this paper, we have proposed a heterogeneous traffic flow based dual ring connectivity model to enhance both the message disseminations and network connectivity. In our proposed model the availability of different types of vehicles on the road, such as, cars, buses, etc., are introduced in an attempt to propose a new communication structure for moving vehicles in VANETl under cooperative transmission in heterogeneous traffic flow. The model is based on the dual-ring structure that forms the primary and secondary rings of vehicular communication. During message disseminations, Slow speed vehicles (buses) on the secondary ring provide a backup path of communication for high speed vehicles (cars) moving on the primary ring. The Slow speed vehicles act as the intermediate nodes in the aforementioned connectivity model that helps improve the network coverage and end-to-end data delivery. For the evaluation and the implementation of dual-ring model a clustering routing scheme warning energy aware cluster-head is adopted that also caters for the energy optimization. The implemented dual-ring message delivery scheme under the cluster-head based routing technique does show improved network coverage and connectivity dynamics even under the multi-hop communication system.     

基于IMS网络的CTD业务平台的设计

提出基于IMS网络的CTD业务平台设计,介绍了CTD平台内部各功能模块及与短信中心、彩信中心、计费、网管等外界系统对接的架构,分析了各分体系的特性。点击拨号所使用的不同场景,提出各种场景所对应的话务模型,通过各种业务需求分析确定平台建设规模,提出计算方法并计算出硬件设备配置,同时提出软件架构。根据网络路由组织原则及网络安全技术要求提出实现该业务功能的网络连接方案。最后根据现网电信运营商应用情况,对CTD平台进行分析总结。     

Towards successful VoLTE and VoWiFi deployment: network function virtualization solutions’ benefits and challenges

The Recent decades have witnessed intensive efforts from operators to implement methods enabling better control over network utilization, service usage, and service monetization. Nevertheless, they report significant growth in Diameter signaling traffic, especially policy management signaling traffic. More specifically, operators offering long term evolution (LTE) data-only services and planning for a massive introduction of voice over LTE (VoLTE) and voice over WiFi (VoWiFi) services need to tackle the enormous growth in Diameter signaling traffic. The biggest challenge for those operators is to find an appropriate solution, scalable enough to handle the unpredictable growth of Diameter signaling traffic; as the VoLTE and VoWiFi services will reshape the landscape of LTE policies. Throughout this paper, we propose a network function virtualization (NFV) based model, mature enough to tackle the challenges of those operators planning to launch VoLTE and VoWiFi, without impacting existing services and without jeopardizing current revenues. In our approach we first used standard VoLTE and VoWiFi message flow and referenced users’ behavior; then we considered NFV architecture characteristics. We finally referred to the latest experiments and test results related to NFV maturity cycle.