1 / 24

Incentive-Compatible Interdomain Routing

Incentive-Compatible Interdomain Routing. Joan Feigenbaum Yale University Vijay Ramachandran Stevens Institute of Technology Michael Schapira The Hebrew University. Verizon. AT&T. Comcast. Qwest. Interdomain Routing. Establish routes between autonomous systems (ASes).

Download Presentation

Incentive-Compatible Interdomain Routing

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. Incentive-CompatibleInterdomain Routing Joan FeigenbaumYale UniversityVijay RamachandranStevens Institute of TechnologyMichael SchapiraThe Hebrew University

  2. Verizon AT&T Comcast Qwest Interdomain Routing Establish routes between autonomous systems (ASes). Currently done with the Border Gateway Protocol (BGP).

  3. Why is Interdomain Routing Hard? • Route choices are based on local policies. • Autonomy: Policies are uncoordinated. • Expressiveness: Policies are complex. Always chooseshortest paths. Load-balance myoutgoing traffic. Verizon AT&T Comcast Qwest Avoid routes through AT&T ifat all possible. My link to UUNET is forbackup purposes only.

  4. Welfare-Maximizing Routing Private information:Route valuations Strategies Mechanism a1 v1(.) p1 AS 1 RoutesR1,…,Rn an vn(.) pn AS n • For each destination (independently / in parallel), compute: • A confluent routing tree that maximizes the sum of nodes’ valuations for that destination, i.e., ∑ivi(Ri) ; and • VCG payments (nodes are paid for their contribution to the routing tree) • … using a BGP-compatible (distributed) algorithm.

  5. VCG Payments Td is the optimal routing tree to destination d. Td-k is the optimal tree to d if node k is removed. • The VCG payment to node k is of the form pk = ∑ikvi(Td) – hk(•) where hk is a function that does not depend on k’s valuation. • If hk({vi}) = ∑i ≠ kvi(Td-k), then the payment to each node is pk(Td) = ∑i ≠ k [vi(Td) – vi(Td-k)].

  6. Payment Components • The total payment to node k can be broken down into payment components:pk(Td) = ∑i ≠ kpki(Td). • Each payment component depends only on the valuations at some node i: pki(Td) = vi(Td) – vi(Td-k). • Compute these in a distributed manner. • Problem: We don’t want to run an algorithm for every Td-k (not efficient).

  7. Routing-Protocol Desiderata • Does not assume a priori knowledge of the network topology • Distributed • Autonomy-preserving • Dynamic (responds to network changes) • Space- and communication-efficient • Complies with Internet next-hop forwarding

  8. BGP Route Processing • The computation of a single node repeats the following: Choose“Best”Route UpdateRouting Table Send updatesto neighbors Receive routes from neighbors • Paths go through neighbors’ choices, which enforces consistency. • Decisions are made locally, which preserves autonomy. • Uncoordinated policies can induce protocol oscillations. (Much recent work addresses BGP convergence.) • Recently, private information, optimization, and incentive-compatibility have also been studied.

  9. Known Results: Welfare Maximizationand Interdomain Routing

  10. Question • These are mostly negative results. • Is there a realistic and useful class of routing policies (i.e., something broaderthan LCPs) for which we can get anincentive-compatible, BGP-compatible algorithm to compute routes and payments?

  11. Gao-Rexford Framework (1) Neighboring pairs of ASes have one of: • a customer-provider relationship(One node is purchasing connectivity fromthe other node.) • a peering relationship(Nodes have offered to carry each other’stransit traffic, often to shortcut a longer route.) peer providers peer customers

  12. Gao-Rexford Framework (2) • Global constraint: no customer-provider cycles • Local preference and scoping constraints, which are consistent with Internet economics: • Gao-Rexford conditions => BGP always converges [GR01] Preference Constraints Scoping Constraints . . . . R1 j provider k1 . . . . . . . . . . d . . . . i peer d i R2 . . . . . . m k2 k customer • If k1 and k2 are both customers, peers, or providers of i, then either ik1R1 orik2R2 can be more valued at i. • If one is a customer, prefer the route through it. If not, prefer the peer route. • Export customer routes to all neighbors and export all routes to customers. • Export peer and provider routes to all customers only.

  13. Efficient Payment Computation • Next-hop valuations: The valuation of a route depends only on its next hop. • Theorem: If Gao-Rexford conditions hold and ASes have next-hop policies, then routes and payments can be computed with “good” space efficiency. * (We only run “BGP” once.)

  14. Next-Hop Payment Computation • Send augmented BGP update message whenever best route or availability of ak-avoiding route changes: • When an update message is received: • Store path and bits in routing table. • Scan bits to update best k-avoiding next hop. AS Path ki-avoiding path known?

  15. Next-Hop Routing Table • Store usable routes, availability of k-avoiding routes from neighbors (for all stored routes), and best k-avoiding next hops (for current most preferred route). • Payment components are derived from next hops:pki(Td) = vi(Td) – vi(Td-k) for transit k ; = 0 otherwise. Best k-avoiding next hops AS 2 AS 2 AS 1 Destination Optimal AS path AS 4 AS 5 AS 2 d Y Y Bit vector from update Alternate AS path AS 3 AS 5 AS 1 d Y Y Bit vector from update

  16. Towards a General Theory • Gao-Rexford + Next-Hop valuations are a special case. • We identify a broad sufficient condition for valuations that permit BGP-compatible, incentive-compatible computation of routes and VCG payments.

  17. Dispute Cycles Relation 1: Subpath Relation 2: Preference Q1 R1 vi(Q1) > vi(Q2) . . . . . . d i i d . . . R2 Q2 Q1Q2 R1R2 • Valuations do not induce a dispute cycle iff there is no cycle formed by the above relations on all permitted paths in the network. • No dispute cycle => robust BGP convergence [GSW02, GJR03]

  18. Example of a Dispute Cycle v(12d) = 10 v(1d) = 5 v(23d) = 10 v(2d) = 5 2 1 1d 2d 3d d 31d 12d 23d 3 v(31d) = 10 v(3d) = 5 Dispute Cycle Subpath Preference

  19. Policy Consistency Valuations are policy consistentiff, for all routes R1 and R2(whose extensions arenot rejected), R1 . . . . k i d . . . THEN vi((i,k)R1) > vi((i,k)R2) R2 IF vk(R1) > vk(R2) (analogous toisotonicity [Sob.03])

  20. Optimality • Theorem: If the valuation functions are policy consistent and do not induce a dispute cycle, then BGP converges to theglobally optimal routing tree.

  21. Efficiently Computing Payments • Local optimality: In a globally optimal routing tree, every node gets its most valued route. • Theorem A: No dispute cycle + policy consistency => local optimality. • Theorem B: Local optimality => If k is not on the path from i to d, then payment component pki (Td) = 0.

  22. Conclusions • Gao-Rexford + Next-Hop valuations are a reasonable class of policies that admit incentive-compatible, BGP-compatible computation of routes and VCG payments. • Only a constant-factor increase in BGP routing-table size is required. • Dispute-cycle-free and policy-consistent valuations generalize this result.

  23. Future Work • Approximability of the interdomain-routing problem? • Without restrictions on policies, no good approximation ratio is achievable [FSS04]. • Remove bank? • Optimal communication complexity?

  24. Technical Report Full version of this paper is available asYale University Technical ReportYALEU/DCS/TR-1342 http://www.cs.yale.edu/publications/techreports/tr1342.pdf

More Related