Download Can Economic Incentives Make the `Net Work?

Can Economic Incentives
Make the ‘Net Work?
Jennifer Rexford
Princeton University
http://www.cs.princeton.edu/~jrex
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
• Today’s interdomain routing
–Protocol allows global oscillation to occur
–Yet, rational behavior ensures global stability
• Improving today’s interdomain routing
–Today’s 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…
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Autonomous Systems (ASes)
Path: 6, 5, 4, 3, 2, 1
4
3
5
2
7
1
6
Web server
Client
Around 35,000 ASes today…
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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”
2
1
data traffic
d
3
data traffic
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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
12d
1d
1
2
23d
2d
3
31d
3d
d
• 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
Better choice!
120
10
Only choice!
0
Top choice!
310
30
Only choice!
Better choice!
3
2
230
20
Only choice!
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 can’t?
• 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
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Bilateral Business Relationships
• Provider-Customer
– Customer pays provider for access to the Internet
• Peer-Peer
– Peers carry traffic between their respective customers
Valid paths: “6
“1 4
23
d”d”
and
and
“7“8
d”5 d”
Invalid
Invalidpaths:
path: “5
“6 85 d”
d” and “1 4 3 d”
1
4
3
2
d
5
6
Provider-Customer
Peer-Peer
7
8
9
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
4
3
2
d
5
6
Provider-Customer
Peer-Peer
7
8
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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
Bank
Most
secure
Shortest
latency
VoIP
provider
School
Lowest cost
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Neighbor-Specific Route Selection
• A node has a ranking function per neighbor

i
j
is node i’s 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
120
10
0
310
30
3
2
230
20
• 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”
Internet
–Today’s
In
Tomorrow’s Internet
Competing ASes
with different goals
must coordinate
Hosting “virtual networks”
over infrastructure owned
by many parties
• 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 links19
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?id=508332
• “Stable Internet routing without global coordination”
– Lixin Gao and Jennifer Rexford
– http://www.cs.princeton.edu/~jrex/papers/sigmetrics00.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_sigmetrics09.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-short.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/p61griffin.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?id=1103561
• Searching for Stability In Interdomain Routing
– http://www.cs.yale.edu/homes/schapira/PID808559.pdf
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Related Papers With Game Theory
• Interdomain Routing and Games
– http://www.cs.huji.ac.il/~mikesch/routing_games-full.pdf
• Rationality and Traffic Attraction: Incentives for Honest Path Announcements in
BGP
– http://ccr.sigcomm.org/online/?q=node/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.pdf
• 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/oppwp32
.pdf
• http://www.potaroo.net/papers/1999-6-peer/peering.pdf
• http://www.cisco.com/en/US/about/ac123/ac147/ac174/ac2
01/about_cisco_ipj_archive_article09186a00800c83a5.html
• http://www.cisco.com/en/US/about/ac123/ac147/ac174/ac2
00/about_cisco_ipj_archive_article09186a00800c8900.html
• http://www.vjolt.net/vol3/issue/vol3_art8.html
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