Can Economic Incentives Make the

1
Can Economic Incentives Make the Net Work?

• Jennifer RexfordPrinceton University
• http//www.cs.princeton.edu/jrex

2
What is an Internet?

• A network of networks
• Networks run by different institutions
• Autonomous System (AS)
• Collection of routers run by a single institution
• ASes have their own local goals
• E.g., different views of which paths are good
• Interdomain routing reconciles those views
• Computes end-to-end paths through the Internet

Wonderful problem setting for game theory and
mechanism design
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Three Parts to This Talk

• Todays interdomain routing
• Protocol allows global oscillation to occur
• Yet, rational behavior ensures global stability
• Improving todays interdomain routing
• Todays routing system is not flexible enough
• Allow greater flexibility while ensuring
  stability
• Rethinking the Internet routing architecture
• Refactoring the business relationships entirely
• Raising a host of new open questions

4
Autonomous Systems (ASes)
Path 6, 5, 4, 3, 2, 1
4
3
5
2
6
7
1
Web server
Client
Around 35,000 ASes today
5
Border Gateway Protocol (BGP)

• ASes exchange reachability information
• Destination block of IP addresses
• AS path sequence of ASes along the path
• Policies programmed by network operators
• Path selection which path to use?
• Path export which neighbors to tell?

I can reach d via AS 1
I can reach d
1
2
3
data traffic
data traffic
d
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Stable Paths Problem (SPP) Model

• Model of routing policy
• Each AS has a ranking of the permissible paths
• Model of path selection
• Pick the highest-ranked path consistent with
  neighbors
• Flexibility is not free
• Global system may not converge to a stable
  assignment
• Depending on the way the ASes rank their paths

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Policy Conflicts ? Convergence Problems
1 2 0 1 0
1
0
2 3 0 2 0
3 1 0 3 0
3
2
In the meantime, data traffic is going every
which way
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Ways to Achieve Global Stability

• Detect conflicting rankings of paths?
• Computationally intractable (NP-hard)
• Requires global coordination
• Restrict the policy configuration languages?
• In what way? How to require this globally?
• What if the world should change, and the protocol
  cant?
• Rely on economic incentives?
• Policies typically driven by business
  relationships
• E.g., customer-provider and peer-peer
  relationships
• Sufficient conditions to guarantee unique, stable
  solution

9
Bilateral Business Relationships

• Provider-Customer
• Customer pays provider for access to the Internet
• Peer-Peer
• Peers carry traffic between their respective
  customers

1
Valid paths 1 2 d and 7 d Invalid path 5 8
d
Valid paths 6 4 3 d and 8 5 d Invalid paths
6 5 d and 1 4 3 d
3
4
2
d
5
6
Provider-Customer
7
8
Peer-Peer
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Act Locally, Prove Globally

• Global topology
• Provider-customer relationship graph is acyclic
• Peer-peer relationships between any pairs of ASes
• Route export
• Do not export routes learned from a peer or
  provider
• to another peer or provider
• Route selection
• Prefer routes through customers
• over routes through peers and providers
• Guaranteed to converge to unique, stable solution

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Rough Sketch of the Proof

• Two phases
• Walking up the customer-provider hierarchy
• Walking down the provider-customer hierarchy

1
3
4
2
d
5
6
Provider-Customer
7
8
Peer-Peer
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Trade-offs Between Assumptions

• Three kinds of assumptions
• Route export, route selection, global topology
• Relax one, must tighten the other two
• Are these assumptions reasonable?
• Could business practices change over time?
• Two unappealing features
• An AS picks a single best route
• An AS must prefer routes through customers

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A Case For Customized Route Selection

• ISPs usually have multiple paths to the
  destination
• Different paths have different properties
• Different neighbors may prefer different routes

Shortest latency
Most secure
Bank
VoIP provider
School
Lowest cost
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Neighbor-Specific Route Selection

• A node has a ranking function per neighbor

is node is ranking function for neighbor node j.
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Stability Conditions for NS-BGP

• Surprisingly, NS-BGP improves stability!
• Neighbor-specific selection is more flexible
• Yet, requires less restrictive stability
  conditions
• Prefer customer assumption is not needed
• Choose any permissible route per neighbor
• That is, need just two assumptions
• No cycle of provider-customer relationships
• An AS does not export routes learned from one
  peer or provider to other peers or providers

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Why Do Weaker Conditions Work?
1 2 0 1 0
1
0
2 3 0 2 0
3 1 0 3 0
3
2

• An AS always tells its neighbor a route
• If it has any route that is permissible for that
  neighbor

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Customized Route Selection

• Customized route selection as a service
• Select a different best route for different
  neighbors
• Different menu options
• Cheapest route (e.g., prefer customer)
• Best performing routes
• Routes that avoid undesirable ASes (e.g.,
  censorship)
• Nice practical features of NS-BGP
• An individual AS can deploy NS-BGP alone
• and immediately gain economic value
• Without compromising global stability!

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Looking Forward Cloud Networking

• In

Todays Internet
Competing ASes with different goals must
coordinate

• Infrastructure providers Own routers, links,
  data centers
• Service providers Offer end-to-end services to
  users

Economics play out vertically on a coarser
timescale.
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Advantages of Virtual Networks

• Simplifies deployment of new technologies
• Easier to deploy in a single (virtual) network
• Multicast, quality-of-service, security, IPv6,
• Enables the use of customized protocols
• Secure addressing routing for online banking
• Anonymity for Web browsing
• Low delay for VoIP and gaming
• Greater accountability
• Direct relationship with infrastructure providers
• Account for performance/reliability of virtual
  links

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Conclusions

• Internet is a network of networks
• Tens of thousands of Autonomous Systems (ASes)
• Network protocols are very flexible
• To enable autonomy and extensibility
• Global properties are not necessary ensured
• Stability, efficiency, reliability, security,
  managability,
• Economic incentives sometimes save the day
• E.g., rational local choices ensure global
  stability
• Are we willing to rely on economic motivations?
• Do we have any choice?

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References Related to This Talk

• The stable paths problem and interdomain
  routing
• Tim Griffin, Bruce Shepherd, and Gordon Wilfong
• http//portal.acm.org/citation.cfm?id508332
• Stable Internet routing without global
  coordination
• Lixin Gao and Jennifer Rexford
• http//www.cs.princeton.edu/jrex/papers/sigmetric
  s00.long.pdf
• "Neighbor-Specific BGP More flexible routing
  policies while improving global stability
• Yi Wang, Michael Schapira, and Jennifer Rexford
• http//www.cs.princeton.edu/jrex/papers/nsbgp_sig
  metrics09.pdf
• "How to lease the Internet in your spare time"
• Nick Feamster, Lixin Gao, and Jennifer Rexford
• http//www.cs.princeton.edu/jrex/papers/cabo-shor
  t.pdf

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Other Related Research Papers

• Inherently Safe Backup Routing with BGP
• http//www.cs.princeton.edu/jrex/papers/infocom01
  .pdf
• Design Principles of Policy Languages for Path
  Vector Protocols
• http//conferences.sigcomm.org/sigcomm/2003/papers
  /p61-griffin.pdf
• Implications of Autonomy for the Expressiveness
  of Policy Routing
• http//conferences.sigcomm.org/sigcomm/2005/paper-
  FeaBal.pdf
• Metarouting
• http//conferences.sigcomm.org/sigcomm/2005/paper-
  GriSob.pdf
• An Algebraic Theory of Interdomain Routing
• http//portal.acm.org/citation.cfm?id1103561
• Searching for Stability In Interdomain Routing
• http//www.cs.yale.edu/homes/schapira/PID808559.pd
  f

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Related Papers With Game Theory

• Interdomain Routing and Games
• http//www.cs.huji.ac.il/mikesch/routing_games-fu
  ll.pdf
• Rationality and Traffic Attraction Incentives
  for Honest Path Announcements in BGP
• http//ccr.sigcomm.org/online/?qnode/395
• Incentive-Compatible Interdomain Routing
• http//cs-www.cs.yale.edu/homes/jf/FRS.pdf
• Mechanism Design for Policy Routing
• http//cs-www.cs.yale.edu/homes/jf/FSS.pdf
• The Complexity of Game Dynamics BGP
  Oscillations, Sink Equlibria, and Beyond
• http//www.cs.berkeley.edu/alexf/papers/fp08.pdf
• Specification Faithfulness in Networks with
  Rational Nodes
• http//www.eecs.harvard.edu/econcs/pubs/podc04.pdf
  
• Distributed Algorithmic Mechanism Design
• http//cs-www.cs.yale.edu/homes/jf/AGTchapter14.pd
  f
• Partially Optimal Routing
• http//www.stanford.edu/rjohari/pubs/por.pdf

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Background on Interdomain Economics

• http//drpeering.net/a/Home.html
• http//www.fcc.gov/Bureaus/OPP/working_papers/oppw
  p32.pdf
• http//www.potaroo.net/papers/1999-6-peer/peering.
  pdf
• http//www.cisco.com/en/US/about/ac123/ac147/ac174
  /ac201/about_cisco_ipj_archive_article09186a00800c
  83a5.html
• http//www.cisco.com/en/US/about/ac123/ac147/ac174
  /ac200/about_cisco_ipj_archive_article09186a00800c
  8900.html
• http//www.vjolt.net/vol3/issue/vol3_art8.html