optimizing cost and performance for concurrent multipath transferring using extended shim6

Ye Wang, Xuan Li, Dongtao Liu, Maoke Chen

ICCT2006Guilin, China

Optimizing Cost and Performance

for Concurrent Multipath Transferring

using extended shim6

Guilin, ChinaICCT2006

Content

Introduction• CMT, shim6, traffic optimization

Modeling, Analysis, and Algorithm• lower cost when performance satisfied

• higher performance when cost restricted

• cost-performance tradeoff (higher NPR)

Simulation ResultsConclusion & Future Work


Introduction – CMT

Concurrent Multipath Transferring• Multimedia / P2P / Distributed Computing / FTP / …

Site

ISP1CERNET2

ISP1CERNET2

ISP2NSFCNET

ISP2NSFCNET

ISP3…

ISP3…

Remote Site

2001:250::4321/64

2001:da8::5678/64

2001:9ef::0246/64

2001:980:ffe:1::42


Introduction – CMT

Possible CMT • multiple TCP connections

– not applicable for general applications

• SCTP– far beyond deployment

– little work for end sites’ demand

• TCP with extended shim6– incremental deployable

– more applicable

– simple way to achieve traffic optimization


Introduction – shim6

Sender A

shim6 Network Paths

ULP

IP

Src ULID(A)Dst ULID(B)

Src L(A)Dst L(B)

Receiver B

shim6

ULP

IP

Src ULID(A)Dst ULID(B)

Src L(A)Dst L(B)

Site Multihoming by IPv6 Intermediation• Separate Identifier (host ID) from Locator (IP address)


Introduction – traffic optimization

Communication Solicitation of End Sites• Performance Maximization + Cost Minimization

Big Challenging for Internet• more than “best effort”

• transferring in Layer 4, forwarding in Layer 3

Our proposal: TCP CMT using extended shim6• intermediation in Layer 4.5

• traffic (re)distribution on multiple Locator pairs

• shim6 + TCP trigger


Introduction – traffic optimization

Related Works• Augmenting TCP

– TCP-Reno, AQM/ECN, RED, XCP, VCP, etc.

• SCTP: Stream Control Transmission Protocol– much more powerful than TCP

– aim at better QoS for general purpose transferring

• Smart routing– distribute traffic “optimally” in Layer 3

– long-term mechanism

– gateway-side traffic control


Modeling – Definitions

Path i (i: 1~n): locator pair iTraffic • traffic volume through Path i:

ISP Pricing and Site Cost• *flow pricing, lease pricing, flat-rate pricing• pricing via Path i by according ISP: • site cost:

Site Performance• bandwidth:• Equivalent Bandwidth:

Natural Price Ratio• NPR:

Internet

6 paths (n=6)

ISP11

ISP12

ISP13

ISP21

ISP2

2

1

n

i ii

C p m

im

ip

ii

mb

t

1

n

ii

mb

t

bu

C


Modeling

Problem Statement• For what and not for what

– How to (re)distribute TCP cwnd? care

– How to rebuild TCP recv window? care

– Which locator pairs to use? careless, depends on shim6

– Deal with fast retransmission? careless at present, depends on TCP-sub

• 1. Optimize cost when performance satisfied

• 2. Optimize performance when cost restrained

• 3. Higher NPR

1

min min1

min ( min )

. ( )

n

i ii

ni

i

p m C

mst B b B

t

1

max max1

max ( max )

. ( )

ni

i

n

i ii

mb

t

st p m C C C

1 1

1

max max{ } max{ / }

n n

i i ii i

n

ii

m p mb

uC t m


Analysis

EB

Typical demands for “at-least” bandwidth

or“at-most” cost

NPR

Cost

A simple metric of how well the traffic is distributed

PerformanceNPR

Cost

“optimalpoint”

Goal: enhance performance and minimize cost

“EB min”

“Cost max”

Cost


Analysis

• Lemma – Timing pricing and lease pricing both call for performance maximization

• Assumption– Paths are ordered by price (p1<p2<…<pn)

• Theorem – N locator pairs, p1<p2<…<pn,

max{ u } = max{ M / [ max{ mi/bi } * sum( pi*mi ) ] } min max { mi/bi } mi/bi = const = t b = b1 (1 + m2/m1 + m3/m1 + … + mn/m1)If mk>0, b = b1 + b2 + … + b(k-1) + b1*mk/m1( good for split and rebuild window, good performance )

or min{ sum( pi*mi ) }m1 = m …( bad performance )

or heuristic algorithm


Algorithms – 1

Lower cost when performance satisfied1. b(i) m(i) / t (i = 1..N);

2. B Bmin; i 1;

3. if B > b(i), then m(i) b(i) * t; else m(i) B * t, end;

4. B B – b(i), i i + 1

5. if i <= n goto 3); else end.


Algorithms – 2

Higher performance when cost restricted• Heuristic

– reduce throughputs when deficit

– improve performance when surplus

1. b(i) m(i) / t (i = 1..n);

2. let C sum( p(i) * m(i) ) (i = 1..n);

3. Cdelta Cmax – C;

4. if Cdelta < 0 then m(i-1) m(i) * 105% (i = 2..n); else m(i+1) m(i) * 95% (i=1..n-1);


Algorithms – 3

Higher NPR• similar as Algorithm 2, but use another metric for judgment

• cut half load of Path i when

• enlarge sub-window of Path i when

• Relative Agio:

• Quick metric:

2

1 1 1

1 1

( )1 1

/( )

n n n

i i i ii i i

n n

i i ii i

m p m mU

t n tm n p m

1

i

ii

i i

mmtU

p p t

iU U

iU U

1 j i jij

i i

p p pr

p p

2

1.. ,

1i i

iik k

k n k i

mU U m

p tn m r m


Simulation Results

Simulation in ns-2• modified TCP agent + multiple modified IP agents

• network topology: 3-ISP multihoming (+ N paths)

• over 1000 runs

Site

ISP1CERNET2

ISP1CERNET2

ISP2NSFCNET

ISP2NSFCNET

ISP3…

ISP3…

Remote Site


Simulation Results

High-bandwidth demand for CMT


Simulation Results

Constant-bandwidth demand for CMT


Simulation Results

Optimize cost when bandwidth satisfied


Simulation Results

Optimize bandwidth when cost restrained


Simulation Results

Optimize Natural Price Ratio


Conclusion and Future Work

Contribution• A case study on future IPv6 Internet technology (shim6)

• Optimize CMT for the cost and performance of multihomed end sites within the TCP layer

Status• Good attempt in theory and simulation-based study

• Little practice (shim6 has not yet been deployed), Only a best-effort way

Stepping forward• Develop real-system (shim6 prototype + UDP + algorithms)

• Better congestion control mechanism (retransmission and reordering)

• Study on site-ISP games

Thank you!

Ye Wang, Xuan Li, Dongtao Liu, Maoke Chen

optimizing cost and performance for concurrent multipath transferring using extended shim6

Documents

site cost

traffic redistribution

traffic optimizationguilin

traffic optimizationmodeling

traffic controlguilin

algorithmlower cost

performance satisfied2

cost restrained3