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AGORA: A Market for Internet Connectivity. Nick Feamster, Georgia Tech Ramesh Johari, Stanford Vijay Vazirani, Georgia Tech. Today’s Internet: Bilateral Contracts. End-to-end connectivity largely determined by bilateral contracts between pairs of ASes Two types of inefficiency - PowerPoint PPT Presentation
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AGORA: A Market for Internet Connectivity
Nick Feamster, Georgia TechRamesh Johari, Stanford
Vijay Vazirani, Georgia Tech
2
Today’s Internet: Bilateral Contracts
• End-to-end connectivity largely determined by bilateral contracts between pairs of ASes
• Two types of inefficiency– Market inefficiency: Excess capacity, unfulfilled demand– Connectivity inefficiency: longer-than-necessary paths
Comcast
Abilene
AT&T Cogent
$$
$$
$$$$
$$
3
Market Inefficiency• Pair of ASes may decide to terminate connectivity arrangement
– Even if end nodes would pay for the path to be there!
31 Jul 2005: Level 3 Notifies Cogent of intent to disconnect.16 Aug 2005: Cogent begins massive sales effort andmentions a 15 Sept. expected depeering date.31 Aug 2005: Level 3 Notifies Cogent again of intent todisconnect (according to Level 3)5 Oct 2005 9:50 UTC: Level 3 disconnects Cogent. Masshysteria ensues up to, and including policymakers inWashington, D.C.7 Oct 2005: Level 3 reconnects Cogent
During the “outage”, Level 3 and Cogent’s singly homed customers could not reach each other. (~ 4% of the Internet’s prefixes were isolated from each other)
October 2005 April 2007
4
Connectivity Inefficiency
• Paths become longer simply because two ASes decide not to interconnect
Comcast
Abilene
AT&T Cogent
$$
$$
$$$$
$$
Peering pointsin Atlanta
Peering pointin Washington, D.C.
5
AGORA: AGregator-Oriented Architecture
• End-to-end paths flow through aggregators• Long-haul providers offer connectivity between aggregators• Connectivity between aggregators is black-box
– May be connectivity on single path, or along multiple paths
• Structure of Internet paths• Exploit new structure to allow new types of contracts
Two Proposed Changes
Aggregators as waypoints(“layer 3 exchanges”)
Market makers as clearinghouses
M
6
Protocol Operation
• Provider advertises, per ingress/egress pair– available capacity and – a price for that capacity
• Market maker(s) compile the pairs of endpoints to be bought and sold
• Stub networks request end-to-end connectivity from market makers
• Market makers solve an optimization problem and allocate resources to stub networks
7
Contracts: Three Types
• Best effort connectivity
• Long-term contracts– Established ahead of time, for set of destinations that
stub network is really concerned with reaching
• Short-term contracts– Recovery from rare, catastrophic periods of
disconnection
8
Challenges
• Protocol for resource advertisement– PCE/Interdomain connectivity database (?)
• Algorithm for resource allocation and computation of end-to-end paths
• Protocol to handle transactions for resources– Possible race conditions
• Scaling considerations
• Incentives for long-haul providers to invest
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