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SidevõrgudIRT 0020

loeng 6 04. okt. 2005

Avo Otstelekommunikatsiooni õppetool,

TTÜ raadio- ja sidetehnika inst.avo.ots@ttu.ee

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Shouldn’t you have some kind of equipment or

something?

It’s the Quality of the Service, our methods are not always apparent.

Q o S

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The Hidden Costs WAN Over-provisioning

LAN Over-provisioning

Increased administrative costs

Extensive Troubleshooting

Unintended PSTN usage

Monitoring and measurement

Problems grow as network size increases

PositiveIP Telephony

Business Case

NegativeIP Telephony

Business Case

HiddenCosts of

Convergence

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• Voice not just another IP data application…

• Enterprise customers have high expectations:– “No tolerance for poor voice, it has to be toll

quality”– “Voice goes down – they are on the phone”– “Don’t want to lose business because of QoS”

• Voice inherently different from most data applications

– Intolerant of delays, packet loss and jitter

– Performance essential to the delivery of the service

– Voice specific application behavior

Yet Yet Another Another

Data Data ApplicationApplication

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DiffServ• Predominant QoS technology in use today

• Bandwidth allocated per traffic classes (via DSCP)

• Traffic Classification and Conditioning at edge

• Per Hop Behavior at interior nodes– Queuing and Dropping according to priority & bandwidth

• Queuing must be configured for minimum packet delay

• Easy for endpoints, scales well, CPU intensive

• DiffServ:– Has no end-to-end network/service view

– Limited Call Admission Control Scheme

– High priority packets can be dropped when congested

– Often difficult to configure and maintain

– Doesn’t always guarantee high quality

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(IntServ)• Reserves resources end-to-end to provide service

guarantees

• Uses the RSVP protocol which signals per flow QoS

requirements to the network

• If reservation succeeds, flow has end-to-end

guaranteed bandwidth

• Includes an inherent call admission control mechanism

• Ideal for real-time traffic such as voice and video

• Providing benefits similar to circuit switching

• Not as heavily used due to perceived drawbacks:– Setup times, I.e. post-dial delay– Issues due to per-flow behavior– Amount of state information and overhead

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IP Solution

Easy to Easy to ManageManage

Dynamic Pro-active Adaptable

Dynamic Pro-active Adaptable

Qos Engineering

Qos Engineering

IP TelephonyIP Telephony ContentContentVideoVideo

MultiserviceApplicationsMultiserviceApplications

Any InfrastructureAny Infrastructure

GatewayGateway RouterRouter SwitchSwitch

MediaIP Controller MediaIP Controller

Flow Aggregation, QoS/Access Control Flow Aggregation, QoS/Access Control

Traffic Engineering, Forecasting and OptimizationTraffic Engineering, Forecasting and Optimization

MediaIP Director MediaIP Director

IntegratedServices

Diffserv (with LLQ)

Operations

Savings

Bandwidth Savings

Bandwidth Savings

PSTN/ISDN Savings

PSTN/ISDN Savings

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Over-Provisioning

• Traditional approach for data networks…

• No mechanism for QoS

• Is actually best-effort

• Overprovision where?

• Expensive

• Converged Networks:– “Bursty” Traffic

– 3X to 5X not sufficient

– Congestion still occurs0 1 2 3 4

0

500

1000

1500

2000

2500

3000

3500

4000

4500

5000Packet Counts

Hours

Pac

kets

Mean

Bandwidth Over-Provisioning

2x

3x

4x

5x

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The Benefits and ROI from QoSThe Benefits and ROI from QoS

Enterprise WAN Network

OperationsCenter

IPPBX

Legacy PBX

PSTN

FewerPSTN Trunks

ReducedPSTN

MinutesReducedISDN

Minutes

WANBandwidth

Savings

AccessBandwidth

Savings

Operations Savings

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384 Kbps Video (30 fps)

• “I” frame is a full sample of the video

• “P” and “B” frames use quantization via motion vectors and prediction algorithms

“P” and “B” Frames128–256 Bytes

“I” Frame1024–1518

Bytes

“I” Frame1024–1518

Bytes

15pps15pps

30pps30pps

600Kbps600Kbps

32Kbps32Kbps