An Overlay Architecture for High Quality VoIP Streams

IEEE Trans. on Multimedia 2006

R97725013 翁郁婷R97725015 周克遠

AUTHORS

Yair AmirJohns Hopkins, US Prof.

Claudiu DanilovJohns Hopkins, Assist.

Stuart GooseIEEE Member

David HedqvistChalmers, Sweden,

Stud.

Andreas TerzisIEEE Member

AGENDA

• INTRODUCTION • FRAMEWORK• DEPLOYMENT• CONCLUSION

INTRODUCTION VoIP Quality of VoIP Internet Loss Characters

VoIP

Voice over IP

> Characters of VoIP

All-IP Service

Low Quality

Low Cost

QUALITY ISSUE

INTERACTIVE

Delay CANNOT higher than 100-150 ms Use UDP to deliver VoIP Packets

LOW QUALITY: PACKET LOSS OR DROP

Loss during the Internet Routing Delay and Drop Packet

Note: Currently we allow short delay: Use a buffer on receiver side

> The Cause Factors of VoIP Quality

INTERNET

• Internet Loss Rate: 0.42%• Internet Burstiness Rate: 72%

FRAMEWORK Overlay Network & Spines Real-time Recovery Protocol Real-time Routing for Audio

THE PROTOCOL

Why use UNRELIABLE UDP protocol?

No sufficient time to End-to-end Retransmission

How about BREAK the END-TO-END into HOP-TO-HOP

> The Reason to Use Spines

OVERLAY NETWORK

Virtual Network with Limited Scope Easy to Implement and Control Overhead Signaling Message

> What is Overlay?

THE SPINES Spines DaemonApplications

Open Source Overlay Network Two-level Architecture Each Spines Daemon (Node) is both SERVER and ROUTER

> The Spines Architecture

> The Real-time Recovery Protocol

1. Keep a buffer on each outgoing link

2. Intermediate nodes forward packets as they are received

3. Upon detecting loss, asks the upstream node for Retransmission. A Retransmission Request for a packet is only sent once.

4. When receives a Retransmission Request:If it has the packet, resends itIf not, ignore the request

5. Only the first instance will be forwarded

RECOVERY PROTOCOL

Real-time Recovery Protocol

LOSS RATE PACKET LOSS RATE on Link: p

One Overlay Link with

Two Overlay Nodes

CASE OF CANNOT RECOVERY1. Retransmission Request Loss

p(1–p)p = p2 – p3

2. Retransmission Packet Loss p(1–p)(1–p)p = p2 – 2p3 + p4

3. Else – NegligibleTotal Loss Probability: 2p2 – 3p3 , approximately

> Calculate the Loss Rate of the Real-time Recovery Protocol

p

THE ROUTING

Real Time Routing For Audio Adjust Overlay Routing to avoid Problematic Path Two Parameter: Packet Loss Rate and Latency

> Use a COST FUNCTION to handle the Two-metric Decision

> Calculate the Cost Function of the Routing

COST FUNCTION

THE COST: TRANSMISSION DELAY

ALL CASES

1. Success Transmit: (1 – p)T2. Recovery Transmit: (p – 2p2 + 3p3)(3T + Δ)

3. Packet Loss: (2p2 – 3p3) Tmax

The Cost Function Texp (1 – p)T + (p – 2p2 + 3p3)(3T + Δ) + (2p2 – 3p3) Tmax

• PACKET LOSS RATE on Link: p• Maximum WAITING TIME: Tmax

• ERROR DETECT TIME: Δ

DELAY DISTRIBUTION

ALWAYS CANNOT HANDLE Delay distribution - 1 link, 5% loss

(1–p)

(p – 2p2 + 3p3)

(2p2 - 3p3)

T

(3T+Δ)

Tma

x

COMPARISON

Different Routing Metrics - 100 nodes

DEPLOYMENT Performance on Loaded Computer Test over PlanetLab

Affected on the LOADED COMPUTERS?

APPLICATION LOAD

OVERLAY PROBLEM

INCREASE the PRIORITY

> Overlay Loading Affected by Application Layer

PlanetLab US

Planetlab US - Percentage of Streams That Missed

CONCLUSIONS

OVERLAY

ADVANTAGE

DISADVANTAGE

CONCLUSION

Segment End-to-end into shorter Overlay Paths Recovery Lost Packets with Limited Time Avoid Problematic Path

Slightly Change the Overall Architecture More Flexibility Easy to Implement and Deployment

Overhead Diminish Margin Utility

THANK YOU FOR ATTENTION