Chapter 7-QoS Management

8/9/2019 Chapter 7-QoS Management

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Quality of Service Provide guarantees on the ability of a network to deliver predictable

results. Elements of network performance within the scope of QoS often

include availability (uptime), bandwidth (throughput), latency

(delay), and error rate.

Multimedia Traffic Parameters

peak arrival rate of the multimedia data when the source is in the

active state(peak rate);

average data unit arrival rate; burstiness: ratio between the peak data rate and the average data

rate;

average duration of the active state.


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Multimedia Traffic Characterization

A requirement for real-time transmission of continuous mediainformation (audio and video);

Substantial volumes of data to be exchanged due to the encoding of

continuous media information;

Distribution-oriented applications; and

Long-range dependency (or similarity)


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Categories of QoS Parameters


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Quality of Service requirements throughput

transit delay

delay variation

error rate

multicasting and broadcasting capabilities

document caching capabilities

The QoS is the collective eect of service performances which

determine the degree of satisfaction of a user of the service..


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QoS Mapping Diagram


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QoS Co-ordination QoS translation captures application QoS requirements

and configures system and network QoS specificationcorrespondingly.

QoS control mechanisms provide real-time traffic control

of flows based on requested levels of QoS established

during the connection. The basic QoS control mechanisms

include traffic shaping, scheduling and flow control.

QoS management mechanisms ensure the contracted QoS

is sustained, which operate on a slower time scale and

implement the QoS monitoring, maintenance,

renegotiation and scalability.


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QoS Co-ordination Allow explicit specification of QoS parameters when creating a

session for multimedia transmission; Translate application QoS parameters into network layer QoS

parameters;

Negotiate QoS demands on the application's behaviours;

reserve the necessary resources at communication systems if

negotiation is successful;

Perform dynamic QoS management on existing sessions;

Employ admission control to check if enough resources are

available to satisfy a new application; and

Regulate and monitor all sessions to protect network resources

from misbehaving users.


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Network Characteristics


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Generalized QoS Framework

Autonomous Systems

Service Level

AgreementService

Provider

Access

Provider

Network

Provider

Service Level Specification

Resource

Provider


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QoS Principles for MM Data Traffic Governing integration principle states that QoS must be configurable,

predictable and maintainable over all architectural layers to meet

end-to-end QoS.

separation principle states that media transfer, control and

management are functionally distinct architectural activities.

transparency principle states that applications should be shieldedfrom the complexity of underlying QoS specification and QoS

management.

multiple timescales principle guides the division of functionality

between architectural modules and pertains to the modeling of

control and management mechanisms.

performance principle subsumes a number of widely agreed rules

for the implementation of QoS-driven communications systems


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QoS Provision Mechanisms Components

QoS Mapping

Automatic translation between representations of QoS at

different system levels


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QoS Provision Mechanisms

Admission Testing It is responsible for comparing the resource

requirement arising from the requested QoS against

the available resources in the system.

Resource reservation protocols

These protocols arrange for the allocation of suitable end-

system and network resources according to the user QoS

specication.


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QoS Control Mechanisms Flow shaping regulates flows based on user supplied flow

performance specifications

Flow scheduling manages the forwarding of flows in the end-

system and network in an integrated manner

Flow policing: dual monitoring: observes whether QoS

contracted by a provider is being maintained whereas the

former observes whether the QoS contracted by a user is being

adhered to

Flow control which includes both open-loop and closed loopschemes

Flow synchronisation which is required to control the event

ordering and precise timings of multimedia interaction


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QoS Management Mechanisms QoS monitoring allows each level of the system to track the

ongoing QoS levels achieved by the lower layer

QoS maintenance compares the monitored QoS against the

expected performance and then exerts tuning operations

on resource modules to sustain the delivered QoS.

QoS degradation issues a QoS indication to the user when

it determines that the lower layers have failed to maintain

the QoS of the flow

QoS availability allows the application to specify the

interval over which one or more QoS parameters

QoS scalability comprises QoS filtering and QoS

adaptation mechanisms.


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QoS System Layers

protocols - transport, network network

middleware

operating system - scheduling, resource

management, real-time support

distributed platforms - CPU, memory/buyers, devices

application


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QoS Specification QoS specification encompasses requirements for:

performance - expected performance characteristics are neededto establish resource commitments,

synchronization - characterizes the degree of synchronization

required between related services, events, or information flows,

level of service - species the degree of resource commitment

required to maintain performance guarantees,

cost of service - the price a user is willing to incur to obtain a

level of service,

QoS management - the degree of QoS adaptation that can be

tolerated and scaling actions to be taken in the event the

contracted QoS cannot be met.


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QoS Parameters Classification of multimedia QoS in communication

layers.


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QoS Parameters An example of QoS parameters at different levels

specified


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User Level QoS Parameters


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Application Level QoS Parameters

End-to-end level

Unicast or multicast;

Dedicated to the transfer of a single

Flow of application data; Able to offer a specific QoS;

To support multimedia applications, the following six

network criteria are critical: through-put; transit delay;delay variation; error rate; multicasting; and

broadcasting capabilities document caching capabilities.


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Transport Level QoS In addition to QoS parameters, an application must

specify four service parameters: The first one characterizes the traffic generated by the

multimedia application sender;

The second one designates which transport protocol to use(UDP, TCP);

The third one designates the IP layer's QoS management

desired by the application;

The final parameter identifies the address, either unicast

or multicast, of set of a destination applications.


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Network Level QoS On the data path: QoS functions are applied by routers at

the packet level in order to provide different levels of

service.

On the control path: QoS functions concern routers

configuration and act to enforce the QoS provided.

Three services have been defined at the IP level:

GS (Guaranteed Service) is used for data flows having

strong constraints in both delay and reliability;

AS (Assured Service) is appropriate for responsive flows

having no strong constraints in terms of delay, but

requiring a minimum average bandwidth;

BE (Best Effort) service offers no QoS guarantees.


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Network Services Rule 1: Services are applied end-to-end, between source

and destination, at all network elements in the path of theapplication flow. This includes the systems' device drivers,

operating systems, and application interfaces.

Rule 2: Services are configurable using QoS

characteristics at each network element in the path of the

application flow.

Rule 3: Services are verifiable within the applicable

network. These rules are necessary conditions for services

to be meaningful within the network and to their high-

priority applications.


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Service Components Maintaining service state of all network elements and end

systems.

User and application support for network services,

including a general mapping of application requirements

to QoS characteristics.

Defining service levels and QoS characteristics.

Mechanisms to evaluate service requests, congure

authorized requests in the network, and manage network

resources. Rules for how services and network resources

are allocated and managed are part of these mechanisms.

Mechanisms for fault detection and management.

S i C


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Service Components

Service Mechanisms

service system will evaluate service requests to

determine if the network has sufficient resources to

support it

Fault Detection and Management

When faults occur on the network, such as routing

transients, hardware and software failures, the

service system will have the capability to recoverfrom faults and re-establish services to its users and

applications.

S i M h i C t


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Service Mechanism Components Theservice system gathers and maintains state for all network

elements and end systems.A user makes a request for a network

service.

The service system evaluates the service request from the

user/application, and either denies the request, accepts the request,

or offers alternatives to the service level requested

If the service request is accepted, the service system configures the

network elements and end systems in the path of the application

flow with the QoS characteristics associated with the service level.

Service system manages network resources for the duration of

service request, then releases the resources at the end of the

request, updating the service system's state and services tables.

N t k Q lit f S i A hit t


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Network Quality of Service Architecture The QoS in the network consists of several software

components, implemented on all network elements and

end-systems in the path of each application flow that

receives QoS from the network.

The network service software components of QoS:

Service system (server) software.

Device drivers for specialized end-equipment.

OS/APIs for end-hosts, possible including end-equipment.

Sets of rules for how service requests are evaluated and

managed, and how network faults are managed, will be

developed and integrated into this software.

f


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Service System Software The service system is the kernel of service request

handling and support. Service system software is implemented on one or more

servers in the network, and it interfaces with

users/applications, network elements, and with end-

systems.

The service system supports all of the components:

maintaining service state, user and application support,

mechanisms to evaluate, configure, and manage service

requests, managing network resources, and mechanisms

for fault detection and management.

D i D i


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Device Drivers As agents for service system software in end-equipment,

device drivers keep state information about its end

equipment, and translate service requests into device-

specific configuration characteristics.

A device driver for an Magnetic Resonance Imaging keeps

information about active and scheduled service requests,

fault information, and the types of device-specific services

that it can offer to the network.

Device-specific service information can be presented by theservice system to users/applications, to help them to

determine which devices they want to use.


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M d lli f Q S M t


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Modelling for QoS Management Metadata required for the management of multimedia:

metadata about the representation, the structure, the

content, the storage and the versions.

Categories of QoS information

the user

the system components

the multimedia documents.

Q S M d lli


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QoS Modelling QoS Parameters associated with system components

User's QoS Parameters

M d l b d Q S M t


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Model based QoS Management QoS Adoption Space

P li b d


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Policy based

QoS

ManagementPolicy

Server

Authentication,

Authorization, and

Accounting

Lightweight

Directory

Access Protocol

Heidelberg QoS Model


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Heidelberg QoS Model

OMEGA QoS Management Architecture


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OMEGA QoS Management Architecture

Int Serv Architecture of QoS Manager


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Int-Serv Architecture of QoS Manager

End System QoS Framework


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End-System QoS Framework

Chapter 7-QoS Management

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