1. Masking Failures Using Anti Entropy and Redundant Independent Paths Rebecca Braynard and Amin Vahdat Internet Systems and Storage Group Duke University http://issg.cs.duke.edu

2. Building Reliable Overlays n Hide failures in the network from applications using the overlay Scalable, reliable publish subscribe systems n Goal: Input: overlay with neighbor connection information and reliability target Probe neighbors for reliability information Construct end-to-end paths that match the target level of reliability n Benefit: Proactively handle failures Avoid convergence time after network failures through redundancy Rebecca Braynard

3. Restricted Flooding n All nodes in the overlay receive the data n Messages do not travel along every link in the overlay n Prevent nodes from receiving multiple copies Idea is similar to Anti Entropy: used to maintain consistency between replicas in distributed computing SourceDestination Rebecca Braynard

4. First Step: Maximum Reliability Tree.98.96.99.97.95.94.97.92.93.92.94.96.99.98 Source Dest_2 Dest_1 Rebecca Braynard.98.96.97.96.98.96 Highest reliability paths for source to destinations 0.951 0.922 Link Reliability (assume independence)

5. Second Step: Multiple Disjoint Routes.98.96.99.97.95.94.97.92.93.92.94.96.99.98 Source Dest_2 Dest_1 Rebecca Braynard.98.96.97.96.98.96 Tune connectivity to application specifications Basic Flood: 14Restricted Flooding: 8 0.951 0.997 0.922 0.996

6. Questions? n Webpage: http://issg.cs.duke.edu/malachi n E-Mail: Rebecca Braynard: rebecca@cs.duke.edu Amin Vahdat: vahdat@cs.duke.edu Rebecca Braynard

7. Research Problems n Disjoint paths may not be available Rebecca Braynard n Nodes only have local network state information to make decisions Only probe direct neighbors in the overlay n Loss correlations between overlay links A B D C 1 3 2 6 5 4 Overlay link Physical link Overlay node Internet router

8. Differences: RON n RON: O(N 2 ) probing to obtain network state information Each node probes every other node in the overlay Global network state to make routing decisions Limits scalability Rebecca Braynard RONBase Overlay Multiple Routes with AE

9. Differences: Mesh-Based Content Routing n MBCR: intermediate nodes receive messages multiple times Single receiver We address the problem of finding disjoint routes Rebecca Braynard Restricted Flooding to reduce network resource consumption Intermediate nodes receive the same message multiple times

10. Link Loss Correlation n Loss rates correlation between links share a link in the underlying topology Rebecca Braynard.99.95.98.95.98.99