Dynamic-CBT and ChIPS – Router Support for Improved Multimedia

Performance on the Internet

Jae Chung and Mark Claypool

Computer Science DepartmentWorcester Polytechnic InstituteWorcester, Massachusetts, USA

http://perform.wpi.edu/

The Internet and Multimedia

Internet routers are best effort– No timing constraints– Packet loss, which indicates congestion

TCP– Completely reliable delivery through retransmission– Respond to loss as congestion

But … TCP often unsuitable for interactive multimedia– Full reliability not needed– Window-based rate fluctuations

Multimedia Using TCP

Multimedia Using UDP

Multimedia on the Internet

Multimedia often uses UDP– Avoid delay and jitter from retransmission– Rate-based– Unresponsive!

Router queue management goals– Congestion Control– Fairness

– Reduce Jitter

Router Queue Management

Drop Tail (FIFO)Drop Tail (FIFO)

Resource ReservationResource Reservation Active Queue MgmtActive Queue Mgmt

......(Floyd, Jacobson ‘95)

CBQCBQ ......(Floyd, Jacobson ‘93)

REDRED

Class-Based Threshold (CBT)

Class-Based Threshold (CBT)

(Parris, Jeffay, Smith ‘99)

Bursty LossUnfairness

Outline

Introduction CBT D-CBT ChIPS Conclusion

CBT Design

Router Queue Management

Drop Tail (FIFO)Drop Tail (FIFO)

Resource ReservationResource Reservation

......

Active Queue MgmtActive Queue Mgmt

...... (Lin, Morris ‘97)

FREDFRED

Class-Based Threshold (CBT)

Class-Based Threshold (CBT)

(Floyd, Jacobson ‘95)

CBQCBQ(Floyd, Jacobson ‘93)

REDRED

(Parris, Jeffay, Smith ‘99)

ChIPSChIPS

Dynamic-CBTDynamic-CBT

D-CBT DesignResponsive MM

EnableThrsh

Evaluation in NS

Developed responsive multimedia application (for tagged UDP class)– AIMD Media Scaling (5 discrete rates)– “MPEG-1 like” transmission rates

Implemented and validated CBT

Implemented D-CBT and measured congestion time fairness– RED vs. CBT vs. D-CBT

Simulation (RED, CBT, D-CBT)

0 10 20 30

25 FTP-TCP

30 FTP-TCP

2 CBR-UDP(5Mbps each)

10 MM-UDP

s1

n1

s2

s66

s67

n2

r2

r2

r66

r67

25Mbps, 20ms

25Mbps, 5ms25Mbps, 5ms

n1-n2: q_size = 60

RED: max_th = 15 min_th = 5 qweight = 0.002 max_prb = 0.1

CBT: mmu_th = 2.9 udp_th = 0.6Second

RED: Class Average Per-Flow Throughput

537293 161

851 720 601

45034681

0

500

1000

1500

2000

2500

3000

3500

4000

4500

5000

0 ~ 10 Sec 10 ~ 20 Sec 20 ~ 30 Sec

Kbp

s

TCP

TAG_UDP

UTAG_UDP

Fairness: RED

Fairness: CBT

CBT: Class Average Per-Flow Throughput

587 613

305

760 739657624

318

0

100

200

300

400

500

600

700

800

900

1000

0 ~ 10 Sec 10 ~ 20 Sec 20 ~ 30 Sec

Kbp

s

TCP

TAG_UDP

UTAG_UDP

Fairness: D-CBT

D-CBT: Class Average Per-Flow Throughput

622659

356

653 660

378

637

313

0

100

200

300

400

500

600

700

800

900

1000

0 ~ 10 Sec 10 ~ 20 Sec 20 ~ 30 Sec

Kbp

s

TCP

TAG_UDP

UTAG_UDP

Outline

Introduction CBT and D-CBT

– Design – Evaluation

ChIPS – Design– Evaluation

Conclusion

Cut-In Packet Scheduling (ChIPS) Design

ChIPS Evaluation - Jitter

MM_APP Frame Delay under Basic D-CBT

30

32

34

36

38

40

42

44

0 5 10 15 20 25 30

Simulation Time (Seconds)

Del

ay (m

illis

econ

ds)

D-CBT

MM_APP Frame Delay under D-CBT with ChIPS

30

32

34

36

38

40

42

44

0 5 10 15 20 25 30

Simulation Time (Seconds)D

elay

(mill

isec

onds

)

D-CBT-ChIPS

ChIPS Evaluation - Fairness

  TCP Packets Delivered

TCP Packet Drop Rate

TCP Throughput

D-CBT 66,648 pkts 4.46 % 17,773 Kbps

D-CBT w/ ChIPS

66,386 pkts 4.44 % 17,703 Kbps

D-CBT: Class Average Per-Flow Throughput

622659

356

653 660

378

637

313

0

100

200

300

400

500

600

700

800

900

1000

0 ~ 10 Sec 10 ~ 20 Sec 20 ~ 30 Sec

Kbp

s

TCP

TAG_UDP

UTAG_UDP

D-CBT with ChIPS: Class Average Per-Flow Throughput

608666

355

673 664

384

563

297

0

100

200

300

400

500

600

700

800

900

1000

0 ~ 10 Sec 10 ~ 20 Sec 20 ~ 30 Sec

Kbp

s

TCP

TAG_UDP

UTAG_UDP

Conclusion

D-CBT– Protect responsive flows from unresponsive– Class-based consideration– Adaptive to mix of flows

ChIPS– Reduce multimedia jitter during congestion

Future Work

Active Flow Counting (Overhead)

– For every incoming packet, update flow info

• Hash Table - O(1)

– Every ms, delete old flows

• Hash Table - O(n)

Measure Overhead– Processing Time and Memory Usage

Future Work

How many different classes are needed?– Example

• 1 class is RED

• 1 class per flow is FRED

– Overhead per class

Effects of D-CBT and ChIPS on Perceptual Quality