Building a Strong Foundation for a Future Internet Jennifer Rexford ’91 Computer Science...
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Transcript of Building a Strong Foundation for a Future Internet Jennifer Rexford ’91 Computer Science...
Building a Strong Foundation for a Future Internet
Jennifer Rexford ’91Computer Science Department
(and Electrical Engineering and the Center for IT Policy)
http://www.cs.princeton.edu/~jrex
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Clean-Slate Network Architecture
• Clean-slate architecture–Without constraints of today’s artifacts–To have a stronger intellectual foundation–And move beyond the incremental fixes
• Still, some constraints inevitably remain–Resource limitations (CPU, memory, bandwidth)–Time delays between nodes–Independent economic entities–Malicious parties–The need to evolve over time
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An Open Research Challenge
Distributed Protocols(decentralized coordination
between many hosts, routers)
Autonomous Actors(autonomous parties, with
different economic objectives)
Global Properties (stability, scalability, reliability,
security, privacy, managability, …)
?
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Two Forays into a Theory of Networks
• Example topic: Internet routing–What paths should carry the traffic?–How should these paths be computed?–How much traffic should traverse each path?
• Two theoretical approaches–Game theory
Interdomain routing driven by economic incentives
–Optimization theory Protocol as an implicit solution to optimization problem
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What is an Internet?
• A “network of networks”–Networks run by different institutions
• Autonomous System (AS)–Routers run by a single institution–With a local routing policy
• ASes have different goals–Different views of which paths are good
• Interdomain routing reconciles those views–Computes end-to-end paths through the Internet
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Conflicting Policies Cause Oscillation
0
1
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1 2 01 0
2 3 02 0
3 1 03 0
Pick the highest-ranked path consistent with your neighbors’ choices.
Only choice!
Top choice!
Only choice!
Better choice!
Only choice!
Better choice!
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Economic Incentives Save the Day
• Two common business relationships– Customer-provider (e.g., Princeton and USLEC)– Peer-peer (e.g., AT&T and Sprint)
• Three economic incentives– No “transit service” for peers and providers– An AS is not its own
indirect customer– Prefer routes through
paying customers
• Provably ensuresa stable system!
2 3
1
d
4
5
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Moving Beyond the Original Model
• How might business relationships evolve?–Backup routes–Siblings
• How might economic incentives evolve?–Desire to attract traffic from others–Accidental and malicious behavior
• How much can we rely on incentives?–Are we willing to rely on economic incentives to
assure the most basic properties of the Internet?–Do we really have a choice?
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Traffic Management Today
• How much traffic should traverse each path?
End hosts:Congestion control
Operator: Traffic engineering
Routers:Compute paths
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Rethinking Traffic Management
• What should be the objective of the system?
Source rate xi
Ui(xi)
Maximize User Utility
Link utilization ul
f(ul
)
Minimize Link Congestion
Goal: max ∑i Ui(xi) - w∑l
f(ul)
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Routers: Compute link “prices”
Distributed Solutions
• Protocols as distributed optimizers–Link prices: higher as load approaches capacity–Path rates: sending traffic over cheaper paths
Edge nodes: Adjust path sending rates
ss
s
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Moving Beyond the Original Model
• Evaluating protocols in practice–Speed of convergence to optimal flow of traffic–Sensitivity to tunable parameters
• Considering other objectives–E.g., minimizing end-to-end delay
• Supporting multiple classes of traffic–Mix of throughput-sensitive and delay-sensitive–Dynamically adapting the sharing of bandwidth
• Deploying the protocols in real networks!
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Conclusion
• Computer networks are key infrastructure–The stakes are very high–Designs that are worthy of society’s trust
• Inherently an interdisciplinary problem–Game theory, optimization theory, control theory,
cryptography, computer science, coding theory–Domain knowledge and an experimental mindset
• We are making real progress–On creating a “science of computer networks”–And on building and deploying new solutions