Making CDN and ISP Routings Symbiotic

1. Making CDN and ISP Routings Symbiotic Varun Khare Beichuan Zhang Department of Computer Science University of Arizona

2. Content Delivery On Internet Origin Server SRVC Content Provider User1 1 OriginSRV SRVC 2 Surrogate Server DNS User3 User2

3. ISPs prefer On-Net Traffic • Traffic served within an ISP’s network • Benefits: • Reduce transmission costs for ISPs for redundant requests • Reduce latency for users by moving content close Origin Server Content Provider Internet ISPA Surrogate Server Users

4. Routing Mismatch for Off-Net Traffic • Routing Conflict: • ISP route traffic as per its inter-domain routing policies • CDN route traffic to maximize performance • Traffic served outside an ISP’s network Content Provider Internet ISPB ISPA Surrogate Server Nearest ISPC Farther Costly IP Route Cheaper IP Route

5. Problem Statement • Mismatch of routing preference can result in higher operational cost for CDN and ISPs • CDN has incentive to resolve such conflicts • For cooperation between CDN and ISPs: • What information needs to be shared? • What mechanism can enable this cooperation? without introducing any unnecessary dependencies

6. Outline • Introduction • CDN and ISP Cooperation • Problem Formulation • CORE-OMN Algorithms • Experiment and Results • Conclusion

7. ISP change their Charging Function • Present: ISP charge on traffic volume • Reality: ISP prefer on-net traffic and want to regulate off-net traffic • Modify: ISP charge as per transmission costs • E.g. On-Net Traffic < Off-Net Traffic $4.2K 50 Mbps = 15 TB

8. ISP announces Pricing Information • CDN need: Given User IP address := available routes and their associated price • Passive BGP session with ISP border router • BGP Community Attribute PATH_PRICE CDN NOCC SRV2 SRV1 IPx | cA(r) IPx | cB(r) ISPB ISPA ISPC IPx: 208.1.1.0/24

9. ISP tailor Pricing Information • ISPs can decide the granularity at which pricing information is exchanged On-Net Customer Off-Net Peer Off-Net Provider Off-Net On-Net Off-Net Per IP Prefix Customer ISPs Small Regional Providers ISPs with inter-ISP Link diversity e.g. Tier-1 and Tier-2 ISPs ISPs with specific Traffic Engineering goals

10. CDN change Request-Routing (RR) • Present: RR improves application performance • Reality: RR also impacts operational cost for CDN and ISPs • Modify: RR assigns users to minimize bandwidth cost, while providing good network performance • Given the ISP routes and associated prices

11. Outline • Introduction • CDN and ISP Cooperation • Problem Formulation • CORE-OMN Algorithms • Experiment and Results • Conclusion

12. Problem Formulation • Given information about servers in CDN: • ISP charging functions for On-Net and Off-Net traffic • Available Bandwidth • Find user assignment for N users that minimizes ISP cost of group i.e.Σ CiON (On-Net) + CiOFF (Off-Net) • Such that: • All users are assigned • Bandwidth constraint is met at every server site.

13. Problem Formulation • Given information about servers in CDN: • ISP charging functions for On-Net and Customer, Peer and Provider Off-Net Traffic • Available Bandwidth • Find user assignment for N users that minimizes ISP cost of group i.e. Σ CiON (On-Net) + CiPROV (T) + CiPEER (T) + CiCUST (T) • Such that: • All users are assigned • Bandwidth constraint is met at every server site

14. CORE-OMN Greedy Algorithm • Assign user to server with least marginal ISP cost • Pseudo-Algorithm: • Find locally cheapest On-Net server (SRVon) • Compare Server and User ISP location • Find globally cheapest Off-Net server (SRVoff) • Compare charges associated with Off-Net IP routes • Compare marginal ISP cost of SRVoff and SRVon • Assign user to server with cheaper ISP cost

15. CORE-OMN Greedy Algorithm • On-Net always preferred over Off-Net Server cAON(r) << both cBOFF(r) and cDOFF(r) On-Net Off-Net ISPA ISPB ISPD Surrogate Server Users

16. CORE-OMN Greedy Algorithm • Order of Off-Net ISP Charging Functions controls CDN Request Routing cBCUST(r) < cDPROV(r) Customer Provider ISPA ISPB ISPD Surrogate Server Customer Route Provider Route Users

17. Problem Formulation • Given information about servers in CDN: • ISP charging functions • Available Bandwidth • Find user assignment for N users that minimizes ISP cost of group i.e. Σ CiON (On-Net) + CiOFF (Off-Net) • Such that: • Delay Constraint for each user is met i.e.For each user Ui assigned to SRVx disti,x ≤ disti,M where SRVM is Top M server • All users are assigned • Bandwidth constraint is met at every server site

18. CORE-OMN Delay Algorithm • Assign user to cheapest server which complies with the delay constraint • User Delay = Last-Hop + Overlay-Tree Delay • Pseudo-Algorithm: • For each User Ui, find top M (=5) servers that don’t violate the delay constraint • Assign user to cheapest server in top M servers using CORE-OMN Greedy Algorithm

19. CORE-OMN Delay Algorithm • Assigns user to cheap delay-compliant server that may not be cheapest Cheap IP Route Farther Costly IP Route Delay-Compliant ISPA ISPB ISPC Customer Route Peer Route Surrogate Server Users

20. Simulation and Experiment Setup • Inter AS topology data (http://irl.cs.ucla.edu/) • Node Relation Map • Publicly available BGP Routing Tables dataRoute Views (http://www.routeviews.org/) • Lixin Gao’s algorithm to infer BGP policy compliant paths between any pair of ISPs • ISP Charging Function • c(r) = (α – β . Log (r) ) . r • c is monthly fees and r is charging volume • CORE-OMN compared against Nearest-Available

21. Server and User Deployment • Servers are deployed in Tier-1 and Tier-2 networks • Users distributed in ISPs with diversity in inter-ISP link connectivity • Users distributed amongst ISPs following Zipf-distribution • Captures clustering and diversity in user population [IMC 2003, IMC 2004]

22. Compare Inter-ISP Traffic • Each RR assign 30% user to On-Net servers • CORE-OMN assigns remaining users predominantly over customer paths • Nearest-Available unable to control inter-ISP traffic

23. Reason for Inter-ISP Traffic Result • On-Net Server saturation forces Off-Net Servers to be used ISPB SRVB ISPA Saturated Peer Route ISPD Provider Route SRVD SRVC ISPC

24. Compare ISP Cost • CORE-OMN by regulating Inter-ISP traffic is able to reduce ISP cost • CORE-OMN-Greedy produces lowest ISP cost • CORE-OMN-Delay present significant ISP cost savings

25. Compare User Delay Performance • CORE-OMN improves user delay by offering lower Overlay Tree delay • CORE-OMN-Delay assigns users to servers that are already part of overlay tree • Nearest-Available increase overlay tree size, which increases overall delay

26. Summary • Modified ISP Charging function provides economic incentives for CDN to consider underling ISP’s routing preferences • CORE-OMN-Greedy achieves lowest bandwidth cost but user network performance suffers • CORE-OMN Delay by assigning users to cheap delay compliant servers provides good network performance with significant savings in bandwidth cost • CORE-OMN moves significant portions of inter-domain traffic over cheaper IP routes when compared to Nearest-Available

27. Thank You Making CDN and ISP Routings Symbiotic Varun Khare vkhare@cs.arizona.edu Kee Roo Search Phrase: CDN and ISP Routings