Next Generation Networks Architecture and Layered End-to-End QoS Control1

Weijia Jia, Bo Han, Ji Shen and Van Fu

Department of Computer Science City University of Hong Kong, 83 Tat Chee Avenue, Kowloon, Hong Kong

wjia@cs.cityu.edu.hk

Abstract. Next-generation network (NGN) is a new concept and becoming important for future telecommunications networks. This paper illustrates five function layers of NGN architecture and discusses some end-to-end QoS (quality of service) for NGN (called NGNQoS) as: (1) One Application Layer that supports SIP protocol; (2) Network Control Layer that aims at overcoming the bottleneck problem at edge nodes or servers for end-to-end admission control; (3) Adaptation Layer that supports different network configurations and mobility; (4) Network Transmission Layer that provides end-to-end QoS controls for real-time communications through integrating DiffServ and MPLS and (5) Management Layer that provides Web-based client-server GUI browser and wireless information connection.

1 Introduction

Next-generation network (NGN) is a new concept commonly used by network designers to depict their vision of future telecommunications networks. Various views on NGN have been expressed by operators, manufacturers and service providers. NGN seamlessly blends the end-to-end QoS into the public switched telephone network (PSTN) and the public switched data network (PSDN), creating a single multi-service network. Rather than large, centralized, proprietary switch infrastructures. Next-generation architecture pushes central core functionality to the edge of the network. The result is a distributed network infrastructure that leverages new, open technologies to reduce the cost of market entry dramatically, and to increase flexibility, and to accommodate both circuit-switched voice and packet-switched data. The integrated services will bring communication market billions of incomes, however, the R&D for NGN still lack behind of the actual demands of the society [1]. On the other hand, the architecture of the Internet and IP-based networks is rapidly evolving towards one where service-enablement, reliability and scale become paramount. Dynamic IP routing supported by routing protocols such as OSPF, IS-IS and BGP provides the basic internetworking function while confronting

1 The work is supported by Research Grant Council (RGC) Hong Kong, SAR China, under grant nos.:

CityU 1055/00E and CityU 1039/02E and CityU Strategic grant nos. 7001709.

the dual challenges of greater scale and faster convergence. Many providers are looking to a converged packet switch network (PSN) future based on IP/MPLS and they seek a way to converge many networks into one to reduce costs and expand service reach. The transport layer protocols including TCP and SCTP continues to be an area of active research as developers seek optimal application throughput and resilience. IP QoS as defined by IntServ and DiffServ continues to evolve and interesting efforts are underway to enhance QoS signaling for wire line and wireless networks.

The challenges and opportunities associated with a fundamental transformation of current networks toward a multi-service ubiquitous infrastructure with a unified control and management architecture have been discussed in BellSouth Science & Technol., Atlanta, GA, USA [2], in which, the outline of the fundamental reasons why neither the control infrastructure of the PSTN nor that of the present-day Internet is adequate to support the myriad of new services in NGN. Although NGN will inherit heavily from both the Internet and the PSTN, its control and management architecture is likely to be radically different from both, and will be anchored on a clean separation between a QoS-enabled transport/network domain and an object-oriented service/application domain, with a distributed processing environment that glues things together and universally addresses issues of distribution, redundancy, and concurrency control for all applications.

This paper presents NGN architecture and discusses some end-to-end QoS for NGN. In Sec 2, a survey for NGN is given and the five layers architecture of NGN is illustrated in Sec 3. Some end-to-end QoS issues of NGN are described in Sec 4 and we conclude in the final section.

2 Survey of NGN: Research and Development

Lucent proposed next-generation networks with various venues, expanding the boundaries [3]. The basis of this proposal is that the coordination of feature interactions in NGN can be served well with the use of semaphores. A feature semaphore is associated with each zone of a call session, and these semaphores become part of the user's per call data. Telcordia Technol in NJ, USA [4] proposed next generation networks (NGNs) that support a variety of communications services (data, video, and voice) seamlessly. Customers will demand that these networks be highly reliable as more and more traffic and services use them. Because of the historically exceptional reliability of wire-line voice telephony, the reliability of voice services supported by NGN voice over packet (VOP) necessitates special attention in order to achieve the customer satisfaction of the service.

In South Koera, KT is considering the installation of NGN backbone network with IP Router. KT is now testing packet delay, loss and jitter in their test bed. QoS discussions on whether the IP router satisfies the forthcoming NGN customers who use basic application of NGN still remain. QoS values as packet delay, packet loss and jitter are measured and analyzed at the KT-NGN test bed, and are compared with the ITU-T QoS recommendation values [5, 6].

In Slovenia, Iskratel Ltd. is a company with of telecommunications with the latest product SI2000 with the basic functions, data and interfaces included in the management node software, which manages various network elements of the SI2000 product line [7] in which data and voice will share a common packet-switched network. The major drawbacks of the current NGN implementations that are based on those services are investigated. A new element in the NGN architecture is proposed, called multi-service mediator (MSM) and an interworking scenario with other currently defined NGN elements is described, especially with the softswitch [8].

Some German companies discuss QoS from a somewhat unconventional point of view and argue that high availability is a key ingredient in QoS perceived by the user. High availability with extremely short interruptions in case of failure is needed for acceptable QoS in real-time dialog services such as telephony or video conferencing and an even distribution of the traffic load over the network is essential to ensure the efficient network utilization given that some kind of admission control for QoS traffic has to be in place for overload avoidance [9].

Alcatel (France) proposes the NGN multimedia network structure and its business model with four players involved in charging: access provider, connection provider, telecommunication service provider, and value-added service provider. Often charging components must be correlated to create a clear postpaid bill and ensure correct treatment of prepaid accounts, as well as settlement between the providers involved. If charging is to remain a prime competitive tool in next-generation networks, it must be functionally intelligent and flexible, and able to optimize operator and service provider revenues while providing a fair policy toward the end users [10]. A prototype for a service platform for the next-generation network is also described, targeted at offering services in fixed and mobile networks using NGN principles, and focused primarily on the architecture of the core IP-UMTS network based on current 3GPP specifications [11]. France Telecom R&D presented a generic functional architecture to help people to identify functions needed to deliver different type of services, with different QoS levels and constraints using a NGN DSL network [12]. IP Differentiated Services have been discussed in Alcatel Network Strategy Group, Antwerp, Belgium and is widely seen as the framework to provide quality of service in the Internet in a scalable fashion. However many issues have still not been fully addressed, such as the way per-hop behaviors can be combined to provide end-to-end services; the specification of admission control and resource reservation mechanisms; and the role of management plane functionality and its integration with the control and data planes.

A team group at NTT, Tokyo, Japan has considered connectionless network is more suitable than connection-oriented network where voice over IP (VoIP) technologies are becoming practical. Call agents are being developed for the next generation network, called NGN-CA. NGN-CA provides OpenAPI, which is standardized application programmer interface to control various network elements. Although various applications using OpenAPI are written, ordinary call agent supports only one OpenAPI because there is difference among call models of OpenAPIs. A call model has been proposed combining multiple OpenAPIs. Various applications written in different OpenAPIs can be installed on the implementation and these applications can provide services on a call simultaneously [14].

Centre for Telecommunication in South Africa, University of Witwatersrand proposed the use of the TINA retailer and accounting management architecture as the basis for usage accounting in the NGN [15]. Three computational objects, namely the accountable object, the metering manager and the accounting policy manager, are used. A CORBA-based distributed processing environment (DPE) enables the TINA components to be deployed in a non-TINA NGN environment. Service components and computational objects used in the TINA accounting management are described.

In UK, next generation IP-based networks that offering QoS guarantees by deploying technologies such as DiffServ and MPLS for traffic engineering and network-wide resource management have been proposed. The discussion includes the following aspects: emerging service level agreements (SLAs) and service level specifications (SLSs) for the subscription to QoS-based services; management protocols for off-line service negotiation and signaling mechanisms for the dynamic invocation of service instances; approaches for the derivation of a traffic matrix based on subscribed SLAs/SLSs and monitoring data; algorithms for off-line traffic engineering and provisioning through MPLS or through plain IP routing with QoS extensions; algorithms for dynamic resource management to deal with traffic fluctuations outside the predicted envelope; a policy-based overall framework for traffic engineering and service management. Finally, ongoing work towards inter-domain QoS provisioning is presented [16]. The base issue of NGN trials on Russian public networks is interoperability testing of foreign equipment and adapted to the specific of Russian networks, domestic NGN system SAPFIR. Results of these NGN trials will be used for the development of the “NGN Evolution Concept” for the Russian public networks [17].

Beijing Univ. of Posts & Telecom., China, discussed that the NGN should provide end-to-end QoS solutions to users and analyzed QoS problems of wireless broadband applications in next generation mobile communications system, sets up a QoS index evaluation model, and presents an adaptive QoS paradigm for wireless broadband applications on NGN. A media negotiation mechanism in soft-switch based NGN is presented. The central point of this solution is to dynamically adjust the bandwidth occupation property of media connection belonging to certain sessions, reserve resource for the sessions, thus guarantee QoS. A variety of solutions are stated considering different soft-switch architecture and different types of sessions [18-20].

3 Overall NGN Architecture

NGNQoS can be described from five layers: (1) Application layer that contains the typical middleware for authorization, accounting, directory, browser, search and navigation of the information for millions of users where we focus on SIP protocol; (2) Network control layer aims at overcoming the bottleneck problem at edge nodes or servers and it composes a series of control agents for admission control, call setup, end-to-end QoS control and application flows through available bandwidth detection and distributed incomplete local information control, class priority and intelligent scheduling. Multicast and anycast group managements will be implemented to leverage the load for the admission control or service/message distributions; (3) Adaptation layer that supports different network configurations and mobility. It provides soft switching between different network on different level such as IPv4, IPv6, ATM, Ethernet, WLAN, WMAN and 3G networks, the layer supports both

packet and circuit switching and provides interconnection between the two switching networks protocols; (4) Network Transmission Layer that provides the effective end-to-end QoS controls for the real-time requests and flows through integration of parameterized QoS control and QoS class priority control, i.e., the DiffServ application to guarantee end-to-end delay with efficient routing algorithms for anycast and multicast etc.. This is particularly important to resolve the bottleneck problems as multipath routing enables the multiple choices for the path and anycast routing enables the selection to different (replicated) server thus reducing the bottleneck problems and (5) Management layer that provides Web-based client-server GUI

Fig. 1. NGN Network Architectures

browser and wireless information connection such as the access to the data using XML and Web-based visualization for data presentation, monitoring, modification and decision making on NGN. The IP telecommunication network architecture and software layer architecture are shown in Fig. 1 (see http://www.huawei.com) in which Bearer Control Layer and Logical Bearer Network together perform network control.

4 Layered End-to-End QoS

This section describes the details of each layer and their functions for end-to-end QoS services. Note that we do not intend to give all the functions for NGN layer but give some important QoS services and introduce our designs and algorithms.

4.1. Application Layer: SIP

Application layer contains typical middleware for authorization, accounting, directory, browser, search and navigation of information for millions of users. Web services have been discussed extensively; however, there are not many discussions about application end-to-end service on the NGN architecture, especially with mobility and multimedia transmissions support. In this subsection, we only focus on a prototype of wired and wireless QoS service using Session Initiation Protocol (SIP) [24]. SIP is an application layer signaling protocol standardized by IETF (Internet Engineering Task Force), which is used for managing multimedia sessions among different parties. An example on existing popular signaling protocols is H.323 [23]. The principle role of SIP is to set up sessions or associations between two or more end users. Sessions initiated can be used to exchange the various types of media data using appropriate protocols such as RTP, RSTP and so on. It can carry out bi-directional authentication and capability negotiation. SIP is simple and extensible. It accepts complementary information inserted as SIP payload for other applications.

Fig. 2. Layered functions of NGNQoS

Network control: Distributed Admission Control End-to-end QoS control,

Available bandwidth detection for resource allocations based on local information

Adaptation: supports different network configurations and mobility: supports soft

switching for packet and circuit switching between IPv4, IPv6, ATM, Ethernet, WLAN, WMAN and

Physical Layer

Managem

ent: Web-based client-server G

UI or

wireless inform

ation browser, accessing, updating,

Visualization and presentation

Applications: SIP based multimedia communications, directory,

browser, Search and navigation, Client-server viewer and browser-viewer

Currently, SIP is able to set up a call carrying the information of a more detailed multimedia session using protocols as the Session Description Protocol (SDP) [21]. By using of adaptive protocol, the selection mechanism is achieved for applying the most suitable communication protocol for end user devices adaptively during connection without any interruption and disconnection [22]. SIP is a control protocol for establishing media sessions. A session can be a simple two-way telephone calls or a collaborative multi-media conference session. The ability to establish these sessions means that a host of innovative services become possible for IP Centrex services such as video conferencing. The application layer SIP implementations may integrate wired and wireless networks based on NGN architecture.

Little work is done to enable end-to-end QoS multimedia transmission of hybrid of wired and wireless with SIP. We have implemented a prototype of wireless service using SIP based end-to-end multimedia transmission system for real time and non-real time video/audio communications, called AnyServer as shown in Fig. 3. To achieve SIP based end-to-end multimedia transmissions, SIP is not only used for call setup signaling, but also carries information for session making in adaptive protocol selection mechanism. SIP carries an SDP packet describing an audio or video session, indicating supported communication protocols and end terminals capabilities exchange. QoS requirements of applications and session ID are used for user identification of multi-parties communications in video-conferencing. To select the most suitable protocol for adapting different situations intelligently during a connection, data buffering service is provided such that media data flows must transmit between end users. In this way, end users can communicate among the others at their best acceptable QoS level without any interruption and disconnection. Currently, we are integrating AnyServer with NGN and wireless networks to provide multi-point end-to-end QoS applications such as video conferencing. Four major functions constitutes of the following system as User Agent in client device, SIP Proxy Server, Database Server and Agent Server to form the heterogeneous wireless and Internet services [32, 35].

Fig. 3 SIP based end-to-end multimedia transmission system for integrated wired

and wireless networks

4.2. Network Control Layer Network control layer composes of a series of control agents for distributed admission control (DAC), call setup and application flows through available bandwidth detection and distributed incomplete local information control, class priority and intelligent scheduling. We discuss the layer based on the following functions:

(1) Traffic classification for incoming requests: This function is performed by scheduler agent that exam the legal incoming requests and make classifications in terms of delay sensitive or VIP traffic. For those VIP/delay sensitive requests, the requests may be tagged with “gold” or “green”, “yellow” or “red (best effort)” tags. Then the classified traffic will be processed through admission control agents (or the admission nodes). To avoid any unnecessary delay, the scheduler and the admission control agents normally reside on the same site. By this tagging approach, the internet and telecommunication tasks can be classified and treated properly as detailed in the end-to-end QoS design. (2) Admission control: We have designed admission control algorithms which performs bandwidth detection and connection control. Bandwidth detection enables the approximate network resource to be detected in case that the networks are managed by different administrates or involved in heterogeneous networks. Based on the available bandwidth detections information and class priority for incoming requests, our distributed admission control algorithms with deal with for admissions for a large number of user connection requests to enhance the scalability and the admission probability by distributing the admission control nodes and the replicating the service nodes. A cooperative distributed approach can be implemented at the some board NGN admission nodes [36] and we give a brief discussion of admission control algorithm for anycast flows below.

Anycast flow is a flow which may connect to any destination in a target group. We consider anycast flow as a general flow concept because the anycast flow may be a unicast flow if the group only has one destination or multicast flows when the flow must be sent to every destination in the group. We first consider the destination selection issue. Destination selection determines which destination the anycast flow should be sent to. A good selection will bring better chance for the flow to be admitted. We propose several weight assignment algorithms based on available information such as route distance and available bandwidth. Different status information surely impacts differently on the network performance in terms of admission probability, overhead, and compatibility as illustrated below:

(1) Weighted destination selection based on the static route distance information [27, 36]: The admission control routers/servers may apply even weight assignments for the destination selection if none of the information is available. For one source, there is one route to a member in an anycast group. The length of the route may be easy to obtain via the current routing protocols [28, 29]. In this scenario, the dynamic information of network may not be available. The differences of route distances reflect the different resource consumption by the anycast flow. Intuitively, the flow to destinations with shorter distances will consume less bandwidth. A flow with short route distance will consume fewer resources. Hence a smart destination selection algorithm should prefer destinations with short route distances.

(2) Weight assignment based on local admission history: The local admission history may be defined as a log that records the successfulness of selecting individual

destinations in admission control. Let Hi record the number of the continual failures in the most recent admission history. For example, Hi =3 implies that for the last three times when destination i was selected in admission control process, there was insufficient bandwidth and resource reservation (to be discussed later) return failure. We propose a destination selection algorithm to combine both route distance and local admission history information. Given that this weight assignment algorithm uses both the route distance and local admission history, we expect that the admission probability will be higher than that of some static algorithm.

(3) Weighted Assignment based on available bandwidth: Local admission history may not accurately reflect the network dynamic status. We may use the approach illustrated in Sec. 4.2.1 to detect the available bandwidth for use of admission control.

Resource Reservation can be made by some standard protocols such as RSVP [30] or to check the availability of link bandwidth along the route based on approach illustrated before. We have extended our anycast admission control protocol [36] to include the bandwidth available information report. 4.3. Adaptation Layer

This layer provides soft-switching between different networks on different levels such as IPv4, IPv6, ATM, Ethernet, WLAN, WMAN or 3G networks which supports both packet and circuit switching and provides soft-switching between the heterogeneous networks. The layer can be divided into the following major functions:

(1) Soft switching between IPv4 and IPv6 using tunneling techniques carried out by edge routers of the subnet between the networks.

(2) ATM and convergence sub-layers merge the ATM cells to IP packets of WLAN and WMAN networks.

(3) Soft switching between ITU H.323/H.324 protocols to handle the circuit/packet switching.

We have implemented efficient transformation of 3G-324M standards for 3G wireless communications [37]. Fast transformation between circuit switching networks to packet switching networks are under development. We are currently using some new algorithms for the connections of wireless networks such as WLAN, WMAN and 3G and implementing the multimedia transmission channel for 3G circuit switching based on 3G-324M standards. The major feature of softawitching is to multiplex the circuit based frames into packets to enable TCP/IP transmissions [37].

4.4. Network Transmission Layer In this layer, we focus on the discussions of Differentiated Service and Multi-Protocol Label Switching and their related end-to-end issues. 4.4.1 Differentiated service

Differentiated Service (DiffServ) architecture achieves scalability by aggregating traffic classification state and it is scalable, which is conveyed by means of IP-layer packet marking use of DiffServ field (or DSCP--codepoint) [22]. Packets are classified and marked to receive a particular per-hop forwarding behavior on nodes along their path. Sophisticated classification, marking, policing, and shaping operations need only be implemented at network boundaries or hosts.

The major advantage using DiffServ is that the Internet flows can be differentiated from the telecommunication flows by the board routers that may deal them with different QoS requirements. This is particularly useful for NGNQoS. We designed some special devices called network mapping (NM) that maps user’s QoS requirement into service level agreements, SLA contract between customer and Internet service provider (ISP). Network resources are allocated to traffic streams by service provisioning policies which govern how traffic is marked and conditioned upon entry to a differentiated services-capable network, and how that traffic is forwarded within that network. A wide variety of services can be implemented on top of these building blocks. The admission control can be integrated with MPLS and DiffServ architectures for the end-to-end QoS solutions, particularly the implementations of controls for end-to-end delay bound, jitter and loss rate. Fig. 5 shows the block diagram of a classifier and traffic conditioner. Note that a traffic conditioner may not necessarily contain all the four elements. For example, in the case where no traffic profile is in effect, packets may only pass through a classifier and a marker.

Fig. 4 Logical View of a Packet Classifier and Traffic Conditioner

To achieve the scalability and QoS for the DiffServ flows, we have designed a generalized regulator to provide an adaptive traffic control mechanism for very high rate real-time aggregated flows, especially, for those traffic that have been marked as red. Normally, three classes of traffic flows (green, yellow and red) in DiffServ network are defined in [23, 24] and we are interested in the deterministic delay bound for the real-time flows which may be marked as red/yellow but do require the stringent delay requirements. We assume that a real-time flow has the priority over the non real-time traffic in the network during transmissions. The generalized regulator, based on the extended network calculus, is developed for the purpose of effective control of high rate of aggregate flows with QoS requirements as detailed in [38].

4.4.2 Multi-Protocol Label Switching (MPLS) In MPLS, packets are encapsulated at ingress points. The local significant labels, which are short and fixed-length, are used in the headers of encapsulated packets. The packets are forwarded via Label Switching Routers (LSRs) by label swapping. An explicit path for each connection is called Label Switched Path (LSP). A reservation protocol is required to establish a LSP through a network.

MPLS is intended to work over any data link layer technology including ATM, Ethernet and SONET. MPLS networks usually refer to IP networks with MPLS and inherit the advantages of connection-oriented networks and the flexibility of

connectionless networks. They provide QoS guaranteed services with a lower computational complexity and operational costs, compared IP networks with ATM connectivity structure. The most important advantage of MPLS networks is that they can perform the traffic engineering for load balancing, which is able to improve the network performance in a long run.

However, since a QoS guaranteed path has to be established for each connection, the total operational overhead of MPLS is not scalable to the network size. Traffic engineering (TE) is in general the process of specifying the manner in which traffic is treated within a given network. TE has both user- and system-oriented objectives [23]. Users expect certain performance from the network, which in turn should attempt to satisfy these expectations. The expected performance depends on the type of traffic the network carries, and is specified in the SLA contract between customer and ISP. The network operator, on the other hand, should attempt to satisfy the user traffic requirements. Hence, the target is to accommodate as many traffic requests as possible by optimally using the available network resources.

Although the concept of TE does not depend on specific layer 2 technologies, MPLS is a suitable mechanism to provide it. MPLS allows sophisticated routing control capabilities as well as QoS resource management techniques to be introduced into IP networks. End-to-end QoS based on MPLS should offer a variety of QoS levels ranging from those with explicit, hard performance guarantees for bandwidth, loss, and delay characteristics down to low-cost services based on best-effort traffic, with a range of services receiving qualitative traffic assurances occupying the middle ground. The following functional architectures are important:

1. Dynamic Route Management (DRM): DRM is responsible for managing the routing processes in the network according to the guidelines produced by admission device (AD) on routing traffic according to QoS requirements associated with such traffic (contracted Service Level Aggrements--SLA). This function is responsible mainly for managing the parameters based on which the selection of one of the established LSPs is effected in the network, with the purpose of load balancing. It receives as input the set of ERPs (multiple Explicates Route Paths per source-destination pair) defined by NM and relies on appropriate network state updates distributed by the DRM function. In addition, it informs AD, by sending notifications, of over utilization of the defined paths so that appropriate actions are taken (e.g., creation of new paths/channels). In this approach, the functionality of the BRM is distributed at the network border routers/edges. In MPLS-based TE the LSP bandwidth is implicitly allocated through link scheduling parameters along the topology of the LSPs, while traffic conditioning enforced at an ingress router is used to ensure that input traffic is within its defined capacity.

2. Bearer Resource Management (BRM): With all the implementations as discussed before, BRM has distributed functionality, with an instance attached to each NGN node/router. This component aims to ensure that link capacity is appropriately distributed between the PHBs sharing the link. It does this by setting buffer and scheduling parameters according to AD directives, constraints, and rules, and taking into account actual experienced load as compared to required (predicted) resources illustrated before. Additionally, BRM attempts to resolve any resource contention that may be experienced while enforcing different per hop behavior (PHB). It does this at a higher level than the scheduling algorithms located in the routers themselves. DRM

gets estimates of the required resources for each PHB from AD such as bandwidth detection, and it is allowed to dynamically manage resource reservations within certain constraints, which are also defined by AD. For example, the constraints may indicate the effective resources required to accommodate a certain quantity of unexpected dynamic SLA invocations. Compared to AD, BRM operates on a relatively short timescale. BRM manages two main resources: link bandwidth and buffer space. (1) Link bandwidth: AD determines the bandwidth required on a link to meet the QoS requirements conveyed in the SLA. BRM translates this information into scheduling parameters, which are then used to configure link schedulers in the routers. These parameters are subsequently managed dynamically, according to actual load conditions, to resolve conflicts for physical link bandwidth and avoid starving of such bandwidth for the enforcement of some PHBs. (2) Buffer space: Appropriate management of the buffer space allows packet loss probabilities to be controlled. The buffers also provide a bound on the largest delay that successfully transmitted packets may experience. Buffer allocation schemes in the router dictate how buffer space is split between contending flows and when packets are dropped. According to the constraints imposed by AD for the QoS parameters associated with the traffic of a given PHB, BRM sets the buffer space and determines the rules for packet dropping in the routers. The drop levels need to be managed as the traffic mix and volume changes. For example, altering the bandwidth allocated to an LSP may alter the bandwidth allocated for the correct enforcement of a corresponding PHB. If the loss probability for the PHB is to remain constant, the allocated buffer space may need to change. BRM also triggers AD when network/traffic conditions are such that its algorithms are no longer able to operate effectively. For example, link partitioning is causing lower-priority/best effort traffic to be throttled due to excessive high-priority traffic and these conditions cannot be resolved within the constraints previously defined by AD.

4.5. Management Layer (plane) This layer provides Web-based client-server GUI browser and wireless information connection such as the access to the data using XML. Web-based visualization presentation is critical for the management of NGNQoS for data presentation, monitoring, modification and decision making. Network management is an indispensable building block in our proposed NGN architecture. NGN management layer contains the management functionality relating to QoS, security and network management. There are five levels in NGN Management Layer as (1) fault-management level, (2) configuration level, (3) accounting level, (4) performance level and (5) security level. Effective management of the NGN is becoming the key to the successful competition and continued growth. To efficiently design and implement NGN Management Layer should deal with the wide variety of challenges such as:

1. Scalability to manage small to large networks; 2. Interoperability of multi-vendor networks under one roof; 3. Carrier’s Operation Expenditure (OPEX) control to increase network

efficiency and hence be more competitive; 4. Deployment and automatic provisioning of millions of lines; 5. Customer satisfaction through reliable and highly available QoS.

Based on a modular concept of element management, domain management and applications, we have designed the NGN Management Layer that fully support day-to-day operation, administration and maintenance tasks, network configuration and service provisioning - including mass deployment for China Mobile (FoShan). Moreover, using of open interfaces for easy integration could round off the functionality of the NGN Management. We also plan to integrate NGN Management Layer into the web environment, into cross-domain management systems and into the business processes of the network operator.

Through recent advances in WWW and Database Management System (DBMS) technology, the best features of both technologies can be combined to provide client/server DBMS applications over the Internet. The result is Web-Based Client/Server (WBCS) computing, which sends and receives dynamic data over the Internet by creating HyperText Mark-up Language (HTML) files on the fly. Almost all major DBMS vendors offer proprietary means to put dynamic data on the web. Third-party tools are now much more abundant and open in nature, allowing use of WBCS applications to access data from various major DBMS brands. Even certain operating systems have built-in WBCS development tools. Most, if not all, of these tools provide a generic, yet customizable gateway between the web server and the DBMS, eliminating much tedious coding. WBCS computing uses a typical web browser to access and manipulate dynamic information, stored in a centrally controlled DBMS, over the Internet. This is an alternative to the current client/server model, in which a custom-written graphical user. Interface (GUI) application accesses and manipulates dynamic information stored in a DBMS using proprietary communication software. WBCS generates HTML pages on the fly to provide the latest information via WWW. Moreover, we aim at the design and implementation of NGN Management Layer with the following features:

1. Scalability: Configurations from a single machine to powerful server-client architecture;

2. Modular and open architecture: Providing a flexible, modular and open client/server architecture based on NGN layering concept;

3. Graphical User Interface (GUI): Providing a task-oriented graphical user interface which offers the same “Look and Feel” as Microsoft Windows;

4. Carrier-grade FCAPS function: The FCAPS (fault-management, configuration, accounting, performance, and security) functions of the NGN Management Layer provide fast fault analysis, qualification of subscriber lines and performance data as input for SLA agreements;

5. Mass provisioning support: Special automatic mass provisioning procedures are available. Used from external network planning systems via XML interfaces, this layer deliver ultra-fast service activation times for new subscribers;

6. Automated supervision: Automated functions such as auto discovery, scheduled software download, automatic export of alarm history or performance log help operators to supervise more efficiently;

7. Easy integration with external OSS: CORBA, SNMP interfaces, as well as file-type interfaces based on ASCII and XML, are available to allow integration into any end-to-end OA&M process.

5 Conclusions

We have discussed some important design issues for the next generation architecture and different layers of end-to-end QoS services. The issues of NGNQoS presented here are not exhaustive; however, the most functions presented are drawn from our design and implementation experiences. The future work will tackle with the cross layer protocols that can harness the heterogeneous networks across Internet, telecommunication and wireless networks. We are currently focusing on the implementations of cross layer/platform of packet switching and circuit switching for 3G wireless networks.

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