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Quality of Service:for Multimedia Internet Broadcasting

Applications

CP 4022- Lecture 1

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Background

• Interactive Multimedia applications stretch resources

• What is Quality of service?• What does a QoS-aware architecture

look like? • What building blocks does a QoS-aware

architecture consist of?• What is happening on the Internet?

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Applications• Four important properties of multimedia

internet broadcasting applications– Continuity,

• IMM applications generally deliver streams of data

– Capacity,• Large amounts of data are transported

– Timeliness• real-time constraints

– Integrity• presentation constraints

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Architectural consideration

• A critical design issue is to provide mechanisms to observe and to control – stream continuity,– buffer capacities, – transmission delays and – integrity of data.

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Definition (1)• QoS is a system or object property, and

consists of a set of quality requirements on the collective behaviour of one or more objects (ISO/IEC IS 10746)

• for example: – rate of information transfer, – the latency, – the probability of a communication being disrupted, – the probability of system failure, – the probability of storage failure, – etc

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Definition(2)

• to evaluate the characteristics of a system or service as to its task performance...qualitatively and quantitatively(ETSI)

• this is an end-user view

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Frameworks(1)• OSI-RM Quality of Service framework ISO 13236

(1997)• Covers speed and reliability of transmission - e.g.

– throughput, – delay, – delay variation (jitter), – bit error rate (BER), – cell loss rate, and – connection establishment failure probability

etc.

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Frameworks(2)

• ODP QoS Framework (1999) – More complete than ISO 13236

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ODP framework

• QoS management of a system is driven by – the QoS characteristics

• user requirements or

• system policies.

• A QoS characteristic represents – QoS aspects of the system, service or the

resources, – the actual behaviour of the application.

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QoS Parameters

• Application - mainly presentation characteristics, e.g.

– image size – resolution, – frame rate, – start-up delay etc

• Transportation - mainly network characteristics e.g

– bandwidth, – delay, – jitter and – transmission error rate

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Management Functions(ODP)

• Application and Transportation– allowing control of QoS

• control at transportation level uses congestion detection (i.e after the event)

• Control at application level allows for congestion avoidance (before the event)

– this split gives a two-level control architecture• application and network level

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Others• Other frameworks exist and different

groupings used– e.g Nahrstedt uses– performance-oriented parameters

• e.g. end-to-end delay and bit rate;

– format-oriented parameters • e.g video resolution, frame rate, storage format and

compression scheme

– a synchronisation-oriented QoS parameter• e.g. the skew between the beginning of audio and

video sequences;

– cost-oriented parameters • e.g. connection and data transmission charges and

copyright fees;

– user-oriented parameters

• these describe the subjective image and sound quality.

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Management functions(ISO)

• Stages of evolution of quality-controlled services– Prediction– resource reservation– negotiation– monitoring– tuning– termination

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User’s view

• How does this fit with the user’s perception?– User’s understand

– resolution, image size, colour depth, etc.

– Mapped onto communication parameters

– cell-loss rate, jitter etc

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QoS Management architecture

(de Meer)

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Principles

• Basic concepts – Feedback (tuning and flow control)– Feed-forward (admission control)

• Architectures need both to be QoS aware

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CORBA

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TINA

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QoSA - Lancaster

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Heidelberg Architecture

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TENET Architecture

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Omega Architecture

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General features• Resource-oriented transport

mechanisms– e.g. point-to-point flow control or admission

control

• Openness– providing visibility of internal behaviour to

enable QoS control– e.g filtering, shaping, monitoring

• Decision procedures– to interpret signals for the adaptation of

resources

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Intserv (integrated services)

Huston G (2000) QoS Fact or fiction, Internet Protocol Journal Vol 3 No 1 from www.cisco.com

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Diffserv(Differentiated services)

Huston G (2000) QoS Fact or fiction, Internet Protocol Journal Vol 3 No 1 from www.cisco.com

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Design constraints

To identify openness constraints for a known QoS policy in terms of observability and controllability.

To identify continuous variables that are stringent to the QoS policy to be achieved. Define their relationships to input and output of the system.

To separate, architecturally, control functions from service functions. Define a clear interface between the control plane and the service or network plane.

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Conclusions

• Many models exist• Those outlined are mainly QoS-

aware• IMM applications will suffer without

QoS-awareness