1. Fixing the Internet: Think Locally, Impact Globally
Jennifer Rexford
Computer Science Department
Princeton University

2. Autonomous Systems (ASes)
Path: 6, 5, 4, 3, 2, 1 4 3 5 2 7 6 1
Web server
Client
Around 35,000 ASes today…

3. Interdomain Routing ASes exchange information with neighbors
Destination: block of Internet Protocol addresses
AS path: sequence of ASes along the path
Local policies in each AS
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

4. Routing Oscillation 1 2 Prefers 1-2-d over 1-d Prefers 2-3-d over 2-d

5. Business Relationships
Provider
Peer
Peer
Customer
Customer pays provider
Settlement-free peering

6. Local Control  Global Stability
Internet hierarchy
No cycles of provider-customer relationships
E.g., my customer’s customer is not my provider
No free-riding
An AS does not support “transit service” for free
Peers and providers can only reach the AS’s customers
Prefer profitable paths
Prefer paths through customers
… over paths through peers and providers
Guaranteed to converge to unique, stable solution

7. Interdomain “Route Hijacking”
AS 6 owns and announces d
AS 1 wrongly announces d 1 2 3 4 5 6 7 d d

8. Incremental Deployment
Complete solution is hard to deploy
Address registry, public key infrastructure, cryptography
Little benefit to early adopters
Incrementally-deployable solutions
Individual ASes detect and avoid suspicious paths
Maintain history of who announces each destination
Prefer paths consistent with path history
Significant security gains
Small deployments (e.g., top 40 of the 35,000 ASes)
Protects around 95% of the Internet
Most big ASes learn at least one valid route
Most other ASes pick routes chosen by these providers

9. How to Build Federated Networks
Evolvable Technology
(under-specified, programmable) ?
Autonomy
(autonomous parties, with economic/political objectives)
Global Properties
(stability, scalability, reliability, security, efficiency, managability, …)
Can we have all three? Under what conditions?