Using Tuángòu to Reduce IP Transit Costs

1. 团购 (tuángòu)= group-buying Using Tuángòuto Reduce IP Transit Costs RadeStanojevic (Joint work with Ignacio Castro and Sergey Gorinsky) ‍‍ ACM CoNext 2011 Tokyo, Japan

2. Part 1: Tuángòufor IP transit CIPT: Using Tuángòu to Reduce IP Transit Costs

3. IP transit as a service • IP transit • Lower tier ISPs customers of higher tier ISPs • Critical for global connectivity • Fee depends on traffic CIPT: Using Tuángòu to Reduce IP Transit Costs

4. IP Transit costs • Affects almost every online entity • IP transit cost-reduction technologies • ISP peering • CDN • Multicast • P2P localization • Traffic shaping (P2P throttling) • The less traffic on transit links the lower the cost CIPT: Using Tuángòu to Reduce IP Transit Costs

5. CIPT: Cooperative IP transit • Simple idea: • Exploit the IP transit market properties: • Price elasticity • 95th-percentile pricing purchase in group and share the costs CIPT: Using Tuángòu to Reduce IP Transit Costs

6. IP transit billing: two key properties • Price elasticity • Peak based traffic metering: 95th-percentile pricing • Submodularity of the peak: • peak(f) + peak(g) ≥ peak(f+g) Voxelpricing Source=https://www.voxel.net/ip-services (as accessed on June 2011) CIPT: Using Tuángòu to Reduce IP Transit Costs

7. CIPT as a cooperative game • How to share the benefits of cooperation? • Shapley value • ‘Fair’, exists and unique for any cooperative game • Individually rational (everyone better off in the coalition) • Hard to calculate exactly for large number of players • Monte-Carlo method for accurate estimation CIPT: Using Tuángòu to Reduce IP Transit Costs

8. Part 2: Quantifying CIPT benefits CIPT: Using Tuángòu to Reduce IP Transit Costs

9. From peering to transit traffic • ISP Transit traffic data: not available • ISP Peering traffic data: available at some IXPs • Peering traffic as a proxy for estimating transit traffic • Ttransit(t) = cTpeering(t) • Validation using 4 medium-sized (academic) ISPs CIPT: Using Tuángòu to Reduce IP Transit Costs

10. Obtaining peering traffic data 1. Peering traffic data of 264 ISPs from 6 IXPs Collection of mrtg images Optical function/ character recognition 2. Transform images into numeric data on peering traffic CIPT: Using Tuángòu to Reduce IP Transit Costs

11. Country-wide coalitions • Expected cost savings in the range of 8%-56% • ISP traffic volume distribution, peak-hour profile, nmb of transit providers, etc. • Per ISP savings from $1K to few $100K per year • Smallest ISPs save >90%, Largest ISPs save <10% • Breakdown • Around 1/3 of the savings come from the 95th-pct • The rest comes from the elastic pricing • Check the paper for details… CIPT: Using Tuángòu to Reduce IP Transit Costs

12. CIPT coalition size: low of diminishing returns • Small (random) coalitions provide most of total attainable gains CIPT: Using Tuángòu to Reduce IP Transit Costs

13. Beyond gains sharing • Organizational embodiment • Physical infrastructure • Performance/SLAs • Traffic confidentiality • Transit providers and strategic issues CIPT: Using Tuángòu to Reduce IP Transit Costs

14. Open problems • CIPT coalition formation process? • Shapley value too implicit. Simpler metrics? • Tuángòu in other (price-elastic) domains? • IP transport • Wired/wireless access • Mobile voice/txt/data CIPT: Using Tuángòu to Reduce IP Transit Costs

15. Conclusions • Team-buying has potential for cutting IP transit bill • Shapley value as a mechanism for cost sharing • Unique dataset of traffic data from 264 ISPs with heterogeneous sizes and temporal properties CIPT: Using Tuángòu to Reduce IP Transit Costs

16. Backup slides CIPT: Using Tuángòu to Reduce IP Transit Costs

17. Cooperative IP Transit (CIPT) • Tuángòu = team-buying coalitional arrangement for bulk buying of IP transit • CIPT gains Per-Mbps price reduction thanks to elastic pricing and peak-based (95th-pct) metering CIPT: Using Tuángòu to Reduce IP Transit Costs

18. Price decay vs. traffic growth Per-Mbps transit price decline vs. interdomain traffic growth Source=https://www.telegeography CIPT: Using Tuángòu to Reduce IP Transit Costs

19. Shapley value definition • Shapley value(i) • ISPi's expected marginal contribution if the players join the coalition one at a time, in a uniformly random order i’s marginal contribution N = number of players c(S)= cost of coalition S S(π,i) = set of players arrived in the system not later than i π = permutations of the set of players N CIPT: Using Tuángòu to Reduce IP Transit Costs

20. Shapley value estimation • Monte Carlo method* • We estimate the Shapley value as the average cost contribution over set πkof K randomly sampled arrival orders. • Estimation accuracy • Kis the knob controlling the accuracy • We use K = 1000 to keep the error under 1% (*) D. Liben-Nowell, A. Sharp, T. Wexler, K. Woods, “Computing Shapley Value in Cooperative Supermodular Games”, Preprint, 2010. R. Stanojevic, N. Laoutaris, P. Rodriguez, “On Economic Heavy Hitters: Shapley Value Analysis of the 95th-Percentile Pricing”, Proc. of ACM IMC 2010. CIPT: Using Tuángòu to Reduce IP Transit Costs

21. Peering-transit traffic similarity • Peering = 35-40% of the total traffic. • Peering and transit follow very similar patterns. CIPT: Using Tuángòu to Reduce IP Transit Costs

22. Aggregate CIPT gains • Absolute aggregate CIPT gains grow with IXP size (in terms of billed traffic) • Relative aggregate CIPT gains decrease with IXP size CIPT: Using Tuángòu to Reduce IP Transit Costs

23. Per-partner CIPT gains • Absolute individual CIPT gains grow with ISP size • Relative individual CIPT gains decrease with ISP size There are large gains for all CIPT members CIPT: Using Tuángòu to Reduce IP Transit Costs