AGORA: A Market for Internet Connectivity

Nick Feamster, Georgia TechRamesh Johari, Stanford

Vijay Vazirani, Georgia Tech

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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

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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

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Connectivity Inefficiency

• Paths become longer simply because two ASes decide not to interconnect

Comcast

Abilene

AT&T Cogent

$$

$$

$$$$

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Peering pointsin Atlanta

Peering pointin Washington, D.C.

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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

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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

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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

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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