Ye Wang, Xuan Li, Dongtao Liu, Maoke Chen

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Optimizing Cost and Performance for Concurrent
Multipath Transferring using extended shim6
ICCT2006 Guilin, China

• Ye Wang, Xuan Li, Dongtao Liu, Maoke Chen

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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 Results
• Conclusion Future Work

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Introduction CMT

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

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20012504321/64 2001da85678/64 20019ef0246
/64
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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

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Introduction shim6

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

Receiver B
Sender A
ULP
ULP
Src ULID(A) Dst ULID(B)
Src ULID(A) Dst ULID(B)
shim6
Network Paths
shim6
Src L(A) Dst L(B)
Src L(A) Dst L(B)
IP
IP
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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

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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

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Modeling Definitions

• Path i (i 1n) locator pair i
• Traffic
• 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

6 paths (n6)
Internet
ISP21
ISP11
ISP12
ISP22
ISP13
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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

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Analysis
Typical demands for at-least
bandwidth or at-most cost
A simple metric of how well the traffic is
distributed
NPR
Cost
Cost max
EB
Cost
optimal point
EB min
Goal enhance performance and minimize cost
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Analysis

• Lemma
• Timing pricing and lease pricing both call for
  performance maximization
• Assumption
• Paths are ordered by price (p1ltp2ltltpn)
• Theorem
• N locator pairs, p1ltp2ltltpn, max u max M /
  max mi/bi sum( pimi ) ? min max
  mi/bi ? mi/bi const t? b b1 (1 m2/m1
  m3/m1 mn/m1)If mkgt0, b b1 b2
  b(k-1) b1mk/m1( good for split and rebuild
  window, good performance )or min sum( pimi )
  m1 m ( bad performance )or heuristic
  algorithm

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Algorithms 1

• Lower cost when performance satisfied
• b(i) ? m(i) / t (i 1..N)
• B ? Bmin i ? 1
• if B gt b(i), then m(i) ? b(i) t else m(i) ? B
  t, end
• B ? B b(i), i ? i 1
• if i lt n goto 3) else end.

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Algorithms 2

• Higher performance when cost restricted
• Heuristic
• reduce throughputs when deficit
• improve performance when surplus
• b(i) ? m(i) / t (i 1..n)
• let C ? sum( p(i) m(i) ) (i 1..n)
• Cdelta ? Cmax C
• if Cdelta lt 0 then m(i-1) ? m(i) 105 (i
  2..n) else m(i1) ? m(i) 95 (i1..n-1)

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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

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Simulation Results

• Simulation in ns-2
• modified TCP agent multiple modified IP agents
• network topology 3-ISP multihoming ( N paths)
• over 1000 runs

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Simulation Results

• High-bandwidth demand for CMT

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Simulation Results

• Constant-bandwidth demand for CMT

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Simulation Results

• Optimize cost when bandwidth satisfied

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Simulation Results

• Optimize bandwidth when cost restrained

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Simulation Results

• Optimize Natural Price Ratio

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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

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Thank you!

• Ye Wang, Xuan Li, Dongtao Liu, Maoke Chen