Ye Wang, Xuan Li, Dongtao Liu, Maoke Chen ICCT2006 Guilin, China Optimizing Cost and Performance for Concurrent Multipath Transferring using extended shim6

Guilin, China ICCT2006 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

Guilin, China ICCT2006 Introduction – CMT Concurrent Multipath Transferring Multimedia / P2P / Distributed Computing / FTP / … Site ISP1 CERNET 2 ISP1 CERNET 2 ISP2 NSFCNET ISP2 NSFCNET ISP3 … ISP3 … Remote Site 2001:250::4321/ :da8::5678/ :9ef::0246/ :980:ffe:1::42

Guilin, China ICCT2006 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

Guilin, China ICCT2006 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)

Guilin, China ICCT2006 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

Guilin, China ICCT2006 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

Guilin, China ICCT2006 Modeling – Definitions Path i (i: 1~n): 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: Internet 6 paths (n=6) ISP11 ISP12 ISP13 ISP2 1 ISP22

Guilin, China ICCT2006 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

Guilin, China ICCT2006 Analysis EB Typical demands for “at-least” bandwidth or “at-most” cost NPR Cost A simple metric of how well the traffic is distributed “optimal point” Goal: enhance performance and minimize cost “EB min” “Cost max” Cost

Guilin, China ICCT2006 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 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

Guilin, China ICCT2006 Algorithms – 1 Lower cost when performance satisfied 1.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 if i <= n goto 3); else end.

Guilin, China ICCT2006 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);

Guilin, China ICCT2006 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:

Guilin, China ICCT2006 Simulation Results Simulation in ns-2 modified TCP agent + multiple modified IP agents network topology: 3-ISP multihoming (+ N paths) over 1000 runs Site ISP1 CERNET 2 ISP1 CERNET 2 ISP2 NSFCNET ISP2 NSFCNET ISP3 … ISP3 … Remote Site

Guilin, China ICCT2006 Simulation Results High-bandwidth demand for CMT

Guilin, China ICCT2006 Simulation Results Constant-bandwidth demand for CMT

Guilin, China ICCT2006 Simulation Results Optimize cost when bandwidth satisfied

Guilin, China ICCT2006 Simulation Results Optimize bandwidth when cost restrained

Guilin, China ICCT2006 Simulation Results Optimize Natural Price Ratio

Guilin, China ICCT2006 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