1

Korea Advanced Institute of Science and Technology

Network Systems Lab.

Dual-resource TCP/AQM for processing-constrained

networks

INFOCOM 2006, Barcelona, Apr. 25, 2006

Minsu Shin and Song ChongDepartment of EECS,

KAIST, Korea

Injong RheeDepartment of CS,

NC State Univ., USA

2

Network Systems Lab.

OutlineMotivation

Processing-constrained networkDual-resource environment

ObjectiveDual-resource fair allocationDual-resource TCP/AQM (DRQ)

DRQ objectiveDRQ implementation

Simulation resultsConclusion

3

Network Systems Lab.

Processing-constrained networkLink bandwidth grows fast

Advancement in optical network technology Over-provisioning as the solution to congestion

The rise of in-network applications

IP forwarding

Packet classification and filteringNetwork address translation

Web-switchingVPN & IPSec

Data TranscodingDuplicate data suppression

Firewall

Complexityincreases

Traditional network

Future network

Virus detection

4

Network Systems Lab.

Dual-resource environmentBoth bandwidth and CPU can be a bottleneck

Can existing congestion control (TCP) be applied?

CPUSwitch

User

Malicious userCongestion

What is fair and efficient resource allocation?

5

Network Systems Lab.

ObjectiveTo propose a dual-resource fairness criteria

Extend the proportional fairness to the dual-resource environmentProvide fair and efficient resource usages

To propose a dual-resource queue (DRQ)Active queue management (AQM) strategy Approximate dual-resource fairness for TCP sourcesScalable : Not maintaining per-flow states or queuesIncrementally deployable : No changes in TCP stacks

6

Network Systems Lab.

Single-resource fairnessOnly considering link bandwidth constraint

Assume that network consists of L links

Ss

ss rU )(maximize

LlBr lS(l)s

s

,

tosubject

Maximization problem

rate r1

TxTxOutput

Link

Bl (Mbps)rate rS

)1(1)1(lim

)log(a

sa

s

s

ra

r

r

)( ss rU

maximum throughputproportionalfair

max-min fair

Selection of [Mo 00]

[Low 99]

7

Network Systems Lab.

Dual-resource fairnessConsidering both CPU and bandwidth constraint

Network consists of L links and K CPUs

TxTxCPUCPUOutput

Link

C (cycles/sec) B (Mbps)

rate r1

rate rS

Ss

ss rU )(maximize

LlBr

KkCrw

lS(l)s

s

kS(k)s

sks

,

,

tosubject

Maximization problem

ksw : processing density

Indicating required CPUcycles per bit

)log( ss r

)( ss rU

Proportional fairness is weight of flow s

Selection of

s

8

Network Systems Lab.

PerformanceSingle link case

Dual-resource fair allocationSingle-resource fair allocation

TxTxCPUCPUOutput

Link

C (cycles/sec) B (Mbps)

rate r1

rate r4

w = [1, 2, 4, 8]

40% utilization increasesCPU fair share

9

Network Systems Lab.

Dual-resource fair rateCongestion price of resources

CPU price : θ, Link price : πIncreasing : demand > resource capacityDecreasing : demand < resource capacityPositive when the resource becomes a bottleneckZero when not a bottleneck

Fair rateInversely proportional to the aggregate price

)()( sLl lsKk k

ks

ss

wr

Weighted CPU price sum Link price sum

10

Network Systems Lab.

Dual-resource TCP/AQMExtend dual-resource fairness to TCP network

DRQ modifies RED algorithmTxTx

B1 (Mbps) C2 (cycles/s)

TxTx

B3 (Mbps)

p2Packet drop with probability p1

p3

CPUCPU

TCP Sender (w) TCP receiver

TCP Sending rate ≈ α

321 ppp Current TCP/AQM

TCP Sending rate ≈ α

321 ppwp Our Goal

11

Network Systems Lab.

DRQ algorithm

TxTx

B1 (Mbps) C2 (cycles/s)

TxTx

B3 (Mbps)

p2packet drop with probability p1

p3

CPUCPU

TCP Sending rate ≈ α

2231 pwpp

Our Goal

Xpwpppwpp 23

22

21

2321 )()(

Each resource drops packet with p2 (link), or (wp)2 (CPU)

)22()22()22( 323121 pwpppwppX

Communication between resources is needed

TCP Sender (w) TCP receiver

12

Network Systems Lab.

DRQ algorithm

32321 22222 pwppwppX

At link 1, mark packet with prob. 12pAt CPU 2, mark packet with prob.

22wpAt link 3, mark packet with prob. 32p

If already marked, then drop packet!

(link), or (CPU) : Intra-marking probability

p2 (link), or (CPU) : Inter-marking probabilitywp2

2p 2)(wp

No explicit communication between resources!

Red card!

Yellow card!

13

Network Systems Lab.

DRQ-ECN implementationThree ECN cases

ECN = 00 : Initial stateECN = 10 : Signaling-marked

(No congestion notification)ECN = 11 : Congestion-marked

(TCP source decreases its window size by half)

DRQ’s ECN marking algorithmWhen a packet arrives

if(ECN ≠ 11) set ECN to 11 with red-card probabilityif(ECN == 00) set ECN to 10 with yellow-card probabilityif(ECN == 10) set ECN to 11 with yellow-card probability

14

Network Systems Lab.

Performance evaluationComparison partners

RED-RED : CPU and link queues use original RED

Very cheap. Most of current network system architecture

DRR-RED : Scheduling CPU using per-flow queue

Expensive approach. Similar architecture to current computing system

TxTxCPUCPUOutput

Link

C (cycles/sec) B (Mbps)

RED RED

TxTxCPUCPUOutput

Link

C (cycles/sec) B (Mbps)

REDDRR

DRQ’s complexity : RED-REDbut,DRQ’s performance : DRR-RED

15

Network Systems Lab.

Single CPU and link case

Topology

DRQ

In DRQ, each follows fair rates.

40 TCP sources, which require different processing(0.25, 0.50, 1.00, 2.00)

Varying CPU capacity

Average throughput of each source

16

Network Systems Lab.

Single CPU and link case

Comparison of bandwidth utilization

RED-RED has much lower bandwidth utilizationDRQ performance is comparable to DRR-RED

Efficiency improves !

17

Network Systems Lab.

Impact of high processing flows

Insert a few high processing flows(w=10.0)

DRQ and DRR-RED prevent their domination but RED-RED doesn’t

Prevent CPU domination!

Increase total throughput

18

Network Systems Lab.

Multiple-link simulation(1)

Throughput of TCP/DRQ in multiple link simulations

Parking-lot topology, with various cross-traffic

DRQ follows theoretic fair rates very well.

19

Network Systems Lab.

Partial deploymentNetwork edge

Pushing complicated tasks to the edge of InternetDRQ can be initially deployed to the edge system

Simulation topology

DRQ is implemented at only IE1 and EE1

Source groups

SG1 : High processingSG2 : low processing

Others : Negligible processing

20

Network Systems Lab.

Partial deployment

Throughput of processing-constrained edge

Increase throughput of IE1

Partial deployment is also beneficial to improve efficiency

21

Network Systems Lab.

ConclusionContribution of this paper

Finding an efficient and fair allocation policy in the dual-resource environmentSuggestion of the practical implementation guideline

22

Network Systems Lab.

References[Kelly 98] “Rate control in communication networks: shadow prices, proportional fairness and stability", J. of the Operational Research Society, 1998

[Mo 00] “Fair end-to-end window-based congestion control", IEEE/ACM TON 2000

[Wolf 00] “Commbench – a telecommunications benchmark for network processors", ISPASS 2000

[Low 99] “Optimization flow control I : Basic algorithm and convergence", IEEE/ACM TON 1999

[Floyd 93] “Random early detection gateways for congestion avoidance", IEEE/ACM TON 1993

[Low 03] “A duality model of TCP and queue management algorithms", IEEE/ACM TON 2003

[Pappu 02] “Scheduling processing resources in programmable routers”, IEEE INFOCOM 2002