A QoS management framework for distributed ... - Semantic Scholar

INTERNATIONAL JOURNAL OF NETWORK MANAGEMENT Int. J. Network Mgmt 2003; 13: 115–127 (DOI: 10.1002/nem.465)

A QoS management framework for distributed multimedia systems By Daniel Won-Kyu Hong*† and Choong Seon Hong‡ This paper proposes a high-performance connection management architecture to design a common QoS framework applied to an ATM network based on the Open Distributed Processing (ODP) concept. We design the QoS framework in accordance from the RM-ODP information and computational viewpoints. Copyright © 2003 John Wiley & Sons, Ltd.

Introduction

M

eeting quality of service (QoS) guarantees in distributed multimedia systems is fundamentally an end-toend issue, that is, from application to application. Consider, for example, the remote play of a sequence of audio and video: in the distributed system platform, quality of service assurances should apply to the complete flow of media, from the remote server across the network to the point(s) of delivery. This generally requires endto-end admission testing and resource reservation in the first instance, followed by careful coordination of disk and thread scheduling in the end system, packet/cell scheduling and flow control in the network, and finally active monitoring and maintenance of the delivered quality of service. A key observation is that for applications relying on the transfer of multimedia, and, in particular, continuous media flows, it is essential that quality of service is configurable, predictable and maintainable system-wide, including the endsystem devices, communications subsystem and networks. Furthermore, it is also important that all end-to-end elements of distributed systems archi-

tecture work in unison to achieve the desired application level behaviour.1 There is much research on the developments in the provision of quality of service support in the context of individual architectural layers.6–8 Much less progress has been made in designing the issue of an overall QoS architecture for multimedia communications. The objective of this paper is to propose a high-performance distributed QoS framework based on the Reference Model of the Open Distributed Processing (RM-ODP) concept.5 First, this paper identifies three levels of QoS specification of application, network and user to identify the necessary QoS information or parameters and to define the reference model of the end-to-end QoS specification. The RM-ODP describes an architecture within which support distribution, inter-working, interoperability and portability can be integrated. The RM-ODP framework defines ODP concerns using five viewpoints (abstraction), namely enterprise, information, computational, engineering and technology.9–14 On the other hand, there are major unsolved problems concerned with end-to-end QoS provision such as incompleteness of application pro-

Daniel Won-Kyu Hong works in the Operations Support System Lab., R&D Group, KT, Daejoen, Korea. ‡

Choong Seon Hong is with School of Electronics and Information, Hyung Hee University, Korea.

* Correspondence to: Daniel Won-Kyu Hong, Operation Support System Lab., R&D Group, KT, 463-1 Jeonmin-Dong Yuseong-Gu, Daejoen 305-811, Korea. † E-mail: [email protected]

Copyright © 2003 John Wiley & Sons, Ltd.

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D. WON-KYU HONG AND C. SEON HONG

QoS Specification

Application Level

• • • •

Video Conferencing Telemedicine Remote Education Web Browsing

QoS Framework Functions Cell Discarding, Priority Control, Buffer Management, Traffic Shaping, UPC, etc Feedback Controls

ATM Level

• • •

Service Categories Source Traffic Descriptor QoS Class

Routing, Connection Setup, Connection Admission Control, Resource Allocation Distributed Network Management

User Level

• • •

PDU Loss Gap Loss Delay

Long Term Network Engineering

Figure 1. QoS specification levels and management functions

gramming interfaces, lack of mechanisms to support QoS guarantees, and lack of an overall framework. To solve these problems, this paper lays down a QoS framework and the QoS mapping rule from applications to network from the perspectives of information and computational viewpoints of RM-ODP. The data unit considered on the application level is the frame (video frame or audio packet) while the ATM cell is used on the network level. That is, this paper focuses on the understanding the relation between application level QoS specification and the network level QoS specification. Application-to-network QOS mapping is needed to reserve the appropriate amount of network resources at connection establishment time. Because good mapping rules are essential for avoiding the reservation of too many or too few resources, this paper proposes the QoS mapping rule between application level and network level QoS specifications in terms of the RM-ODP information object. In addition this paper designs the distributed computational QoS model taking into account the performance under the distributed processing environment of CORBA. Lastly, it shows two kinds of scenarios: one is to establish the end-to-end QoS guaranteed connection and the other is to provide the long-


term and short-term network planning according to the analysis of performance data. The rest of this paper organized as follows. In the next section, we define three levels of QoS specification. In the third section we present the distributed QoS reference model in accordance with the three levels of QoS specifications. In addition, the two reference models are described in terms of RM-ODP information and computational viewpoints respectively. In the fourth section we shows the end-to-end QoS provisioning scenario and network planning scenario. Finally, in the fifth section we summarize our study and further studies.

A Reference Model for End-toend QoS Specification Quality of Service can be defined at various levels in terms of the information transport protocol of ISO layered architecture. There are three kinds of levels of QoS specifications: application, network and user. The application level QoS specification refers to multimedia-based user applications such as video conferencing, telemedicine, web browsing, etc. The network level QoS specifi-

Int. J. Network Mgmt 2003; 13: 115–127

QoS MANAGEMENT FRAMEWORK FOR MULTIMEDIA SYSTEMS

cation represents the ATM service categories such as CBR (Constant Bit Rate), UBR (Unspecified Bit Rate), nrt-VBR (non-real time Variable Bit Rate), rtVBR (real-time Variable Bit Rate) and ABR (Available Bit Rate). The user level QoS specification at the lowest level refers to the PDU loss, gap loss and delay. Figure 1 shows the QoS specification levels and the network management functions for the QoS Framework.

A Distributed QoS Reference Model The current state of QoS provision in architectural frameworks can be summarized as follows:7 • Incompleteness: current interfaces (e.g. application programming interfaces such as Berkeley Sockets) are generally not QoS configurable and provide only a small subset of the facilities needed for control and management of multimedia flows. • Lack of mechanisms to support QoS guarantees: research is needed in distributed control, monitoring and maintenance QoS mechanisms so that contracted levels of service can be predictable and assured. • Lack of an overall framework: it is necessary to develop an overall architectural framework to build upon and reconcile the existing notion of quality of service at different system levels and among different network architectures.

T

o solve the incompleteness, lack of mechanisms to support QoS gurantees and lack of an overall framework, a reference mode of QoS framework is needed.

117

based QoS mapping, we find an optimal route satisfying the required traffic descriptor and QoS parameters referring to the network resources and we control the network elements to set-up connection in line with the found optimal route via the User Level QoS Specification—Reference Point (QLQR-RP). From now on, the network elements at the User Level QoS Specification (ULQS) do the necessary functions to guarantee the requested QoS, to avoid network congestion, and so on. In addition, each network element gathers network status such as in/out cells, lost cells, discarded cells, and so on. The gathered network status is reported to the Performance Manager at the Network Level QoS Specification (NLQS) via the LNQS-Reference Point 2 (LNQS-RP2). In this section, we define the three kinds of models for the QoS framework from the perspectives of RM-ODP information, computation and engineering respectively.

—An Informational Model— An information viewpoint is used to describe the information required by an ODP application through the use of schemas, which describe the state and structure of an object.10–12 The information specification of an ODP application could be expressed using a variety of methods, e.g. entityrelationships models, conceptual schemas, and the Z formal description technique. However, this paper specifies the QoS information model using the Rumbaugh’s Object Model notation (OMT)15 as shown in Figure 3.

A

To solve these problems, we define a reference model of QoS framework for ATM as shown in Figure 2. At the Application Level QoS Specification (ALQS), we identify the required service types and issue it to the Rule-based QoS Manager at the Network Level QoS Specification (NLQS) via the NLQS-Reference Point 1 (NLQS-RP1). The rulebased QoS manager maintains the rule-based QoS mapping relationship between the service type and the traffic descriptor. After finishing rule-


n information viewpoint is used to describe the information required by an ODP application through the use of schemas, which describe the state and structure of an object.

As described above, there are three kinds of QoS specification level of application, network and user. The relationship between the application level QoS specification and the network level QoS specification is shown in Table 1.


118


Application Level QoS Specification (ALQS) Video Conference

…..

Web Browsing

Telemedicine

Video Phone

NLQS-RP1

Network Level QoS Specification (NLQS) Network Resource Management

Node B Link

Rule-Based QoS Mapper

Node A

Available Bandwidth for ABR and UBR

Performance Monitor

Reserved Bandwidth for ABT traffic : Â MCRt t

Reserved Bandwidth for nrtVBR traffic : Â SCRt t

Reserved Bandwidth for rtVBR traffic : Â SCRt t

Guaranteed Bandwidth for CBR traffic : Â PCRt t

Routing (CAC)

Connection Management NLQS-RP2

ULQS-RP

User Level QoS Specification (ULQS) SB

TB B-NT2

B-TE

B-NT1

UPC

Connection Admission Control Priority Control Traffic Shaping Congestion Control Resource Management SB B-TE

Network A

Network-to-Network Interface (NNI)

TB B-NT2

B-NT1

Network B

NPC

Figure 2. A reference model of the QoS framework

The Application Type information object represents the service types to be supported in an ATM network as described in Table 1. The QoS Profile information object represents the meter to be applied to Network Level QoS Specification (NLQS). It is determined by the rule-based QoS coordinator composed of service categories, traffic descriptors and QoS class as shown in Table 1. The detailed rule-based QoS Profile is described in Table 2. The Network Resource and Topology information object represents the network topology that is preplanned according to service needs and its bandwidth management information as shown in the part of network resource management of the reference model of Figure 2.


We manage the bandwidth of each link in accordance with the service categories and the service needs of each service category. In addition, network elements monitor the network connection and resource status in terms of performance and QoS guarantee. The Performance Monitor at the NLQS periodically collects the network connection and resource status to identify whether there is any performance degradation and whether any connection of QoS is guaranteed. The Performance Data information object maintains the collected network connection and resource status from network elements as shown in Table 3. The Network Planning Policy information object maintains the policies for re-configure network topology for improving network perfor-



119

Figure 3. Information model for QoS framework

Application Level

Network Level Service Category

POTS, Circuit Emulation CBR-Video Packet-Video & Audio in teleconferencing, Multimedia applications Connection-oriented Data Service (X.25, Frame-Relay) Connectionless Data Service (IPOA, SDMS) Connection-oriented Data Service (LAN-interconnection) Connectionless Data Service (LAN-interconnection, Internet)

CBR rt-VBR

Traffic / QoS Parameters PCR, End-to-End CTD, Peak-to-Peak CDV, BER, CLR PCR, SCR/MBS, End-to-End CTD, Peak-to-Peak CDV, BER, CLR

rrt-VBR

PCR, SCR/MBS, BER, CLR

nrt-VBR

PCR, SCR/MBS, BER, CLR

ABR

PCR, MCR

UBR

Table 1. The relationship between application and network level QoS specifications

mance and the ATM VP/VC connection reconfiguration for guaranteeing the requested QoS.

—A Computational Model— The computational viewpoint is used to specify the functionality of an ODP application in a


distribution-transparent manner.11–13 A computational specification defines the objects within an ODP system, the activities within those objects, and the interactions that occur among objects. Most objects in a computational specification describe application functionality, and these objects are linked by bindings through which interactions



QMR-11

QMR-9 QMR-10

QMR-8

QMR-6 QMR-7

QMR-5

QMR-4

~ 70 Mbps DS1: 1.5 Mbps CBR DS3: 5 Mbps CBR 64 kbps ~ 45 Mbps

~ 10 Mbps

64 kbps ~ 2 Mbps 64 kbps ~ 45 Mbps

10 Mbps VBR

1.5 Mbps VBR

4.0 ms + 2.0 ms per 100 miles

— 150 ms

0.8 ms 27 ms ~ 1.185 sec —

5 ms

5 ms

5 ms

300 ms 5 ms

64 kbps ~ 384 kbps 2 Mbps CBR 5 Mbps VBR

300 ms

End-to-End CTD

64 kbps CBR

Bit Rate

0.5 ms

— 200 ms

—

1 ms

6.5 ms

6.5 ms

130 ms 6.5 ms

10 ms

Peak-toPeak CDV

1.8 ¥ 10-6 2.5 ¥ 10-6 1.5 ¥ 10-6

10-11 4 ¥ 10-11 6 ¥ 10-12

10-7

5 ¥ 10-13

1.3 ¥ 10-6

With error handling in AAL

3 ¥ 10-11

10-7

Without error handling in AAL

BER

Network level QoS Specification (NLQS) CLR

2 ¥ 10-9

10-8

4 ¥ 10-9

10-8 10-8

10-3

Without error handling in AAL

Table 2. Rule-based QoS mapping between application and network level QoS specifications

PVC Cell Relay CBR

LAN Emulation IPOA Circuit Emulation

Video Phone Video Conference MPEG 1 Core MPEG 2 Core Frame Relay SDMS

QMR-2

QMR-3

Voice Telephony

QMR-1

QoS Application Mapping Level QoS Rule Spec. (QMR) (ALQS)

10-9 1.7 ¥ 10-10

10-7 10-7

4 ¥ 10-6

9.5 ¥ 10-6

5 ¥ 10-6

8 ¥ 10-6 8 ¥ 10-6

With error handling in AAL

120 D. WON-KYU HONG AND C. SEON HONG



Categories Performance Information

121

Group

Item

Cell Level Protocol Group TC Adaptor Group TC Traffic Load Group VP/VC Traffic Load Group VP/VC UPC/NPC Group

QoS Information

Discarded Cells Invalid Header Discarded Cells HEC Violation Error Cells HEC Violation Incoming Cells Outgoing Cells Incoming Cells Outgoing Cells Discarded Cells Successfully Passed Cells Response Time Excessive Queue Size Exceeded Bandwidth Reduced Retransmission Rate Excessive Threshold Crossed Performance Degraded Congestion

Table 3. Performance data information object

occur. There are some generic control/management functions to support the end-to-end QoS provisioning. Because of the distributed nature of a large-scaled ATM network, the network management functions for guaranteeing the ATM QoS should be distributed. To support these functions for supporting end-to-end QoS provisioning and the distributed nature of a large-scale telecommunications network, this paper proposes the computational model of a distributed QoS framework based on the CORBA distributed processing environment in terms of the RM-ODP computational viewpoint as shown in Figure 4.

T

he computational viewpoint is used to specify the functionality of an ODP application in a distribution-transparent manner. A computational specification defines the objects within an ODP system, the activities within those objects, and the interactions that occur among objects. Most objects in a computational specification describe application functionality.

• Network Topology Manager (NTM): To deploy any service network, it is the prerequisite for


a network service provider to plan and to dimension the service network according to its network planning policy taking into account the service types and subscriber demands. In addition, it is necessary for the network service provider to reconfigure the service network on some occasions such as performance degradation, fault, and the change of subscriber’s requirements. Therefore the Network Topology Manager has the network planning policy and tools. • Resource Configuration Management (RCM): This manages the network resources and network topology provided by the Network Topology Manager (NTM) in terms of network management layer function of TMN. It also manages the link bandwidth according to the service category as shown in Figure 1. It aims to provide short-term network engineering, which is necessary for a QoS framework to detect network abnormalities in real-time and changes the network topology to provide incessant network service provisioning. • Subscription Data Manipulation Manager (SDMM) receives service subscription via web, fax and phone from service users and issues the work orders to provide the network service in accordance with the subscriber’s requests. It also maintains subscriber-related


122


Service Subscription via Web, Phone, Fax and so on Subscriber Data Manipulation Manager (SDMM)

Client Role Traffic Mediator (TM)

Service Types 3

ATM Traffic Descriptor & QoS Class 4 Gather Performance Data

Network Topology Manager (NTM) Network Resource Provisioning & Reconfiguration

Optimal Route or Reroute 6 Provisioning

Routing and Rerouting Manager (RRM)

13 Request Alternative Path

Connection Manager (CM) 12

14

5

Resource Configuration Manager (RCM)

CORBA Object

Server Role

Connection Admission Control

1

2

CORBA Object

Notify Performance Degradation 9

Network Element Resource Provisioning & Reconfiguration

Performance Data Manager (PDM) 8

Performance Data Collection

Event Notification Manager (ENM) Event Notification

Connection Setup/ Modify/ Release

10 7

CORBA/CMIP . CORBA/SNMP Gateway (JIDM)

Figure 4. A computational model for a QoS framework

data such as service type, service provisioning period, billing data, etc. • Traffic Mediator (TM) takes the main role of mapping between an Application Level QoS Specification (ALQS) and the Network Level QoS Specification (NLQS) according to the previously defined mapping role in Tables 1 and 2. • Routing and Rerouting Manager (RRM) provides the optimal route based on the network topology maintained by the Network Topology Manager (NTM) and provides alternative route in cases of performance degradation and fault. Finding an optimal route or alternative route, it refers to the network resource information maintained by the Resource Configuration Manager (RCM) in terms of Connection Admission Control (CAC). In order to guarantee the required QoS level to users and maintain the network utilization in best condition, the transport network must perform the bandwidth allocation and the route selection according to the service category.


– For the CBR service, the bandwidth must be allocated for the required PCR, and the endto-end CTD must be guaranteed. The route selection for the CBR traffic is finding a route with minimum end-to-end CTD that can allocate the required bandwidth, peak-to-peak CDV (cell delay variance) and CLR (cell loss ratio). – In rt-VBR service, the bandwidth is allocated for the required SCR (sustainable cell rate) that is defined as the upper bound on the conforming average rate of an ATM connection. For the rt-VBR services, the transport network guarantees the SCR with associated MBS (maximum burst size), end-to-end cell transfer delay timing, and peak-to-peak CDV. The route selection criteria for the rt-VBR traffic are the same as for the CBR service. – In nrt-VBR services, the requested band width is allocated by either SCR or MCR. The transport network must guarantee the SCR/MCR, mean CDV.



– In ABR services, the transport network guarantees the MCR (minimum cell rate) of the requested bandwidth and the CLR. – In UBR services, the transport network guarantees no specific traffic/QoS parameters for the services. At each switching node, the bandwidth allocation is performed according to the priority of service category. The switching node determines the acceptance of the connection establishment request by the connection admission control (CAC) with the buffer allocation (BA) strategy. • Connection Manager (CM) establishes, modifies and releases the ATM VP/VC PVC in accordance with the route selected by Routing and Rerouting Manager (RRM). It interacts with the CORBA/CMIP or CORBA/SNMP gateways to control the network elements and maintains the established connection information. • Event Notification Manager (ENM) receives various kinds of event generated by network elements such as fault, performance degradation, notifies them to the Resource Configuration Manager (RCM) in terms of synchronization of network resource status between EML and NML or to the Connection Manager (CM) to provide the end-to-end QoS guaranty by fast rerouting. In addition, it performs alarm correlation, fault localization, alarm propagation and alarm logging. • Performance Data Manager (PDM) periodically gathers the performance data of the network resources and VP/VC PVC from network elements. It analyses the gathered performance data identified in Table 3 to validate whether there is any symptom to affect the contracted QoS requirement with the subscriber and logs into the database for the purpose of providing them to the Network Topology Manager (NTM). The Network Topology Manager (NTM) refers to the performance data logged by the Performance Data Manager to reconfigure network topology in terms of the network optimisation and the increment of end-to-end QoS guarantee probability. It aims to provide the long-term network engineering, which is most necessary for the QoS framework to gather the performance data from the network and to analyse them to plan the future network topology.


123

• CORBA Gateway (CG) adapts the distributed CORBA computational objects to the CMIP or SNMP-based network elements in accordance with the JIDM approach.16 The Network Element (NE) has the following major functions of Usage/Network Parameter Control (UPC/NPC), Congestion Control, Priority Control and Buffer Control. The Usage/Network Parameter Control is defined as the set of actions taken by the network to monitor and control traffic in accordance with the traffic offered and validity of the ATM connections, at the user access and the network access, respectively. The user may generate different priority traffic flows by using the cell loss priority bit in term of priority control. A congested network element may selectively discard cells with low priority if necessary to protect as far as possible the network performance for cells with high priority.

The QoS Provisioning Scenario We implement the proposed distributed QoS framework using the CORBA, especially IONA Orbix 2.3c and the Oracle DBMS. We also use three workstations of SUN ULTRA Sparc 20 (E6500) equipped with two 336 MHz CPUs respectively. One is for Subscriber Data Manipulation Manager (SDMM), another is for Traffic Mediator (TM), Routing and Rerouting Manager (RRM), and Connection Manager (CM), and the other is for Network Topology Manager (NTM), Resource Configuration Manager (RCM), Performance Data Manager (PDM) and Event Notification Manager (ENM).

S

hort-term network planning restores performance or a faulty connection in real-time for the purpose of a QoS guarantee.

In this section, we will show two scenarios. One is to provide the end-to-end QoS guaranteed ATM PVC establishment and the other is to reconfigure the network topology in terms of long-term network planning and the connection in terms of short-term network planning with the assumption that the service network planning has been fin-


124


SDMM

TM

(1) Service Type (Source/Destination)

RRM

(2) Service Category / Traffic Descriptor / QoS Class (Source/Destination)

RCM

CM

CG

(3) Service Category / Traffic Descriptor / QoS Class (4) CAC Result (OK) (5) Service Category / Traffic Descriptor / QoS Class (Route)

(8) CAC Result (OK) (10) CAC Result (OK)

(6) Service Category / Traffic Descriptor / QoS Class (7) CAC Result (OK)

(9) CAC Result (OK)

Figure 5. ATM PVC establishment scenario for end-to-end QoS guarantee

ished with the interaction among Network Topology Manager (NTM), Resource Configuration Manager (RCM) and Network Element (NE). Short-term network planning restores performance or a faulty connection in real-time for the purpose of a QoS guarantee. The scenario for supporting short-term network planning is shown in Figure 5: (1) The SDMM receives the subscription from the subscriber and issues the work order to establish the end-to-end QoS guaranteed connection to Topology Mediator with the service type. (2) On receiving the service type from SDMM, TM derives the necessary Network Level QoS Specification (NLQS) in accordance with Tables 1 and 2. After determining the NLQS, TM issues the optimal route selection request to Routing and Rerouting Manager (RRM) with the LNQS. (3) After calculating the equivalent according to the service category, QoS parameters and traffic descriptor, the Routing and Rerouting Manger (RRM) finds the most reasonable path from its routing table and requests CAC of the selected route to Resource Configuration Manager.


(4) On receiving CAC request, RCM does CAC on the route provided by RRM and returns its result to RRM. (5) If the CAC result is successful RRM issues the end-to-end connection establishment request to Connection Manager (CM). (6) On receiving connection set-up request, the CM issues the cross-connection requests to all CORBA Gateways (CGs) traversing the route provided by RRM. (7) Every CG returns its result to Connection Manager (CM). (8) On receiving the cross-connection result from CGs, the CM returns its result to Routing and Rerouting Manager (RRM). (9) The RRM gives the result of end-toend connection establishment to Traffic Manager (TM). (10) The TM gives the result of end-to-end QoS guaranteed connection establishment to SDMM. The SDMM maintains the subscriber information for the purpose of billing. Our distributed QoS framework provides the long- and short-term network planning mechanism from the perspective of stable service



CG

NTM

PDM

CM

RCM

RRM

(2) Notify Performance Degradation (Network Bandwidth)

(3) Network Bandwidth Manipulation (4) Result (OK)

(4) Notify Performance Degradation (Connection)

Target Object - Network Bandwidth - Connection

(5) Request Alternative Route

(6) CAC (7) CAC Result (OK) (9) Connection Set-up or Release

(8) Provide Alternative Route

(10) Result (OK) (11) Result (OK)

(2) Change Network Topology (3) Network Resource Resize, Addition or Removal (4) Result (OK) (5) Result (OK)

Performance Monitoring For Long-term Network Planning

(1) Gather Performance Data per every 15minutes

Performance Monitoring Short-term Network Planning

(1)Notifyr Performance Data per every 15minutes

125

Figure 6. Long- and short-term network planning scenarios for QoS guarantee

network provisioning and real-time connection restoration respectively. Figure 6 shows these scenarios. The scenario for supporting the long-term network planning is as follows: (1) The Network Element (NE) sends the gathered performance data to Performance Data Manager (PDM) via CORBA Gateway (CG) every 15 minutes. (2) On receiving the performance data from CORBA Gateways, the PDM analyses them. If it is necessary to reconfigure network topology such as increase, modify or decrease of link bandwidth as a result of analysing the performance data, Perfor-


mance Data Manager (PDM) issues the link manipulation requests to Resource Configuration Manager (RCM). (3) After receiving the link bandwidth manipulation, RCM issues the link bandwidth manipulation requests to corresponding Network Elements (NEs) via CORBA Gateways (CGs). (4) After manipulation of link bandwidth according to the requests of RCM, each Network Element (NE) returns its result to RCM. (5) After manipulating the link bandwidth, Network Elements (NEs) return their results to Resource Configuration Manager (RCM).


126

(6) On receiving the performance data from CORBA Gateways, the PDM analyses them. If it is necessary to reroute the existing connection because of performance degradation, Performance Data Manager (PDM) notifies the performance degradation of connection to Connection Manager (CM). (7) On receiving the performance degradation, the CM issues the alternative route selection request to Routing and Rerouting Manager (RRM). (8) After calculating the equivalent according to the service category, QoS parameters and traffic descriptor, the Routing and Rerouting Manger (RRM) finds the most reasonable alternative path from its routing table and requests CAC of the selected route to Resource Configuration Manager. (9) On receiving CAC request, RCM performs CAC on the route provided by RRM and returns its CAC result to Routing and Rerouting Manager (RRM). (10) On receiving alternative route from RRM, the CM issues the cross-connection removal/addition requests to every CORBA Gateways (CGs) traversing the alternative route provided by RRM. (11) Every CGs returns its result to Connection Manager (CM). (12) On receiving the cross-connection result from CGs, the CM returns its result to Routing and Rerouting Manager (RRM).

T

he long-term network planning reconfigures network topology from the perspective of not only the link bandwidth modification but also network topology change such as node or link addition.

On the other hand, the long-term network planning reconfigures network topology from the perspective of not only the link bandwidth modification but also network topology change such as node or link addition. The network planning policies of the network service provider as a result of long-term performance analysis determines this. The scenario to change network topol-



ogy in terms of long-term network planning is as follows: (1) The Network Topology Manager (NTM) retrieves the gathered performance data from Performance Data Manager (PDM) every 15 minutes. (2) On retrieving the performance data from PDM, the NTM analyses them. If it is necessary to reconfigure network topology such as addition, removal or modification of network topology in accordance with the its planning policy, the NTM issues the network topology change requests to Resource Configuration Manager (RCM). (3) After receiving the network topology change request, RCM issues the network resource manipulation requests to corresponding Network Elements (NEs) via CORBA Gateways (CGs). (4) After manipulating the network resources, Network Elements (NEs) return their results to Resource Configuration Manager (RCM). (5) On receiving the result of network resource manipulation from Network Elements (NEs), the RCM issues the result of network topology change to the Network Topology Manager (NTM).

Concluding Remarks The current status of QoS provision in architecture frameworks has some problems such as incompleteness of application programming interfaces, lack of mechanisms to support QoS guarantees and lack of overall framework. To solve these problems and to meet the distributed nature of a telecommunications network, this paper proposed a distributed QoS framework taking into account the maximization of QoS provisioning performance under the distributed processing environment. Because the RM-ODP gives a useful design concept concerning the distributed application, we designed the QoS framework according to information and computational viewpoints. From the perspective of information, we identified the three-level QoS specifications for identifying the end-to-end QoS guaranteed information and parameters and proposed the rule-based QoS mapping rule between application and network level QoS specification. From the perspective of



the computational viewpoint, we proposed the distributed computational QoS model taking into account the distribution of QoS management functions under the distributed processing environment. We also implemented the proposed QoS framework using CORBA and showed two kinds of scenarios: one is to provide the end-to-end QoS guaranteed connection provision and the other is to provide long- and short-term network planning as a result of the analysis of the network performance data to deploy the efficient service network in terms of QoS guarantees. However, there are some unsolved issues in a distributed QoS framework such as real-time performance data gathering from a network element, its analysis, and real-time manipulation of the network resource or connections suffering from performance degradation. This method can gather network performance data every 15 minutes because most network elements collect their performance data every 15 minutes. It is not appropriate to provide the unceasing end-to-end QoS service provision of the highly guaranteed QoS connections. Therefore some mechanisms should be further studied to rapidly detect the performance degradation of network resources including connections and to restore the network resources suffering from performance degradation as soon as possible.

5.

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9. 10.

11.

12.

References

13.

1. Aurrecoechea C, Campbell AT, Hauw L. A survey of QoS architectures. ACM/Springer Verlag Multimedia Systems Journal, Special Issue on QoS Architecture, 6: 3, 138–151, May 1998. 2. Huard J-F, Lazar AA. On QoS mapping in multimedia networks. 21st IEEE Annual International Computer Software and Application Conference (COMPSAC ’97), 13–15 August 1997; Washington, D.C. 3. Huard J-F, Lazar AA. On end-to-end QoS mapping. IFIP Fifth International Workshop on Quality of Service (IWQoS ’97) May, 1997; New York, 303–314. 4. Chan MC, Lazar AA. Designing a CORBA-based high performance open programmable signalling system for ATM switching platforms. IEEE Journal

14.


15.

16.

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on Selected Areas in Communications, 1999; 17: No. 9, September. Tokuda H, Kitayama T. Dynamic QoS control based on real-time threads. Proc. Fourth International Workshop on Network and Operating System Support for Digital Audio and Video, Lancaster University, UK, 1993. ODP. Draft recommendations X.903: basic reference model of open distributed processing, ISO/IEC JTC1/SC21/WG7, International Standards Organization, 1992. Hutchison D, Coulson G, Campbell A, Blair G. Quality of service management in distributed systems. Network and Distributed Systems Management, Sloman M (ed.). Addison-Wesley: 1994. Yeadon N, Garcia F, Campbell A, Hutchison D. QoS adaptation and flow filtering in ATM networks. Second International Workshop on Advanced Teleservices and High Speed Communication Architectures, Heidelberg, 1994. CCITT Recommendation X.701 | ISO/IEC 10040 Systems Management Overview. Draft ITU-T Recommendation X.901 | ISO/IEC CD 10746-1—Basic Reference Model of Open Distributed Processing—Part 1, November 1993. Draft ITU-T Recommendation X.902 | ISO/IEC DIS 10746-2—Basic Reference Model of Open Distributed Processing—Part 2: Descriptive Model, April 1994. Draft ITU-T Recommendation X.903 | ISO/IEC DIS 10746-3.1—Basic Reference Model of Open Distributed Processing—Part 3: Prescriptive Model, April 1994. Draft ITU-T Recommendation X.725 | ISO/IEC DIS 10165-7—General Relationship Model. Draft ITU-T Recommendation X.750 | ISO/IEC DIS 10164-16—Systems Management: Management Knowledge Management Function. Rumbaugh J, Blaha M, Premerlani W, Eddy F, Lorensen W. Object-oriented modeling and desing. Prentice Hall: 19991. NMF CS342: CORBA/CMIP/SNMP Interworking. The Open Group, 1997.

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