Resilient Overlay Networks Robert Morris Frans Kaashoek and Hari Balakrishnan MIT LCS

Problems with ISP-Based Routing Users cannot select routing metrics. Sophisticated routing only within each ISP. Only ISPs assemble measurements. Hop-by-hop model is error-prone.

Example Problem: Policy Routing ISP3 ISP1ISP2 Site 1 Site 5Site 4 Site 3 Site 2 The red path may be legal but forbidden by policy.

RON Approach Move routing control towards end systems. Take advantage of small scale. Base decisions on end-to-end monitoring.

A Resilient Overlay Network ISP3 ISP1ISP2 N1 N5N4 N3 N2 RON node / edge router Site 2 Virtual RON link RON nodes exchange measurements and choose routes. Site 1 Site 3

End-System Control Enables Sophisticated Applications End-to-end QoS requirements. End-to-end metrics and trust. Aggressive adaptive re-routing algorithms. Application-oriented policy interpretation. Coordinated reactions to DoS attacks.

Example: Reliable Routing ISP3 ISP1ISP2 N1 N5N4 N3 N2 Overload x

Example: Perimeter Defense (1) Analyzing DoS attacks requires cooperation. –Detect near target, control near source. –Variable routing confuses historic traffic analysis. –Asymmetric routing hides one-way flows. –Hard to guess ingress even w/ true source addr. Groups of ISPs can deploy monitoring nodes. –Use RON for reliable coordination.

Example: Perimeter Defense (2) ISP3 ISP1ISP2 C1 C4 C3 C2 R4R3 R2R1 1. Look for unusual traffic. 2. Exchange alerts over RON. Attacker 3. Detect and control sources.

RON Implementation Challenges Measurements Topology choice Adaptive Routing Security

Measurements Characterize alternate paths: –Do they fail independently? –How often do they perform better? –Are there multiple sensible metrics? Are measurements predictive? Time scales long enough for adaptive routing?

Topology Choice ISP3 ISP1ISP2 N1 N7 N6 N4 N2 N5 N3 IP routing prefers short virtual links for high reliability. Gnutella prefers long links for fast query propagation.

Adaptive Routing Goal: Good paths through the RON topology. Tools: –Application-provided guidance. –Small scale  aggressive algorithms. –Cooperative measurement infrastructure. –RON-level source routing obviates consistency. Example: choose best 2-hop path.

Security Protection of data: –End-to-end or IPSec over RON virtual links. Protection of routing and control traffic: –Sites can choose whom to trust. Protection against DoS attacks on RON: –End-to-end authentication, hash cash.

Project Plan 1.Measure existing Internet for validation. 2.Design topology and routing algorithms. 3.Deploy RON nodes. 4.Build initial app: real-time collaboration. 5.Generalize API (content distribution, peer to peer file sharing).

Summary RON moves routing control to end systems. Well suited to collaborating groups of sites. Benefits: –More robust routing than the Internet. –More control over QoS. –Platform for cooperative defenses.