1. A Comparison of Overlay Routing and Multihoming Route Control
Aditya Akella, Bruce Maggs, Jeffrey Pang, Srinivasan Seshan,
Annes Shaikh
07/28/04
Systems Seminar - Claudiu Danilov

2. Systems Seminar - Claudiu Danilov
Background
Overlay routing can improve performance over BGP, between a limited number of nodes [RON, Detour]
Flexibility, key property of overlays
Basic assumption of previous overlay studies is that end nodes subscribe to a single ISP
Multihoming allows end-network sites to schedule their transfers over multiple ISPs (route control)
How much benefit does overlay routing provide over BGP, when multihoming and route control are considered ?
Round trip time and throughput metrics are used
07/28/04
Systems Seminar - Claudiu Danilov

3. Systems Seminar - Claudiu Danilov
Definitions
k-multihoming: End node has access to multiple ISPs. Emulated by a virtual node composed of multiple physical 1-multihoming nodes in the same city.
k-overlay: Same as above, but paths can use additional nodes
Note: Multihoming can be seen as a special case of overlay with paths of max 2 hops, and intermediate nodes on different ISPs
Note: What is the difference between 1-overlay, k-overlay and k-multihoming?
07/28/04
Systems Seminar - Claudiu Danilov

4. Systems Seminar - Claudiu Danilov
Testbed
68 nodes,17 US cities
All-to-all latency and throughput measurements
Two types of throughput estimates – optimistic and pessimistic
Assumptions
Instantaneous knowledge about the performance and availability of routes via each of its ISPs or overlay paths
For throughput maximizing overlay paths, only paths comprised of at most two overlay hops are considered
07/28/04
Systems Seminar - Claudiu Danilov

5. 1-Multihoming vs. 1-Overlays
1-Overlays offer better round trip time (33%) and throughput (15%)
In a large fraction of measurements (46%) indirect paths offered better RTT performance than direct path.
07/28/04
Systems Seminar - Claudiu Danilov

6. 1-Multihoming versus k-Multihoming and k-Overlays
Both k-multihoming and k-overlay routing offer significantly better performance than 1-multihoming
k-overlay, (k≥3) performs better than 1-overlay (5-20% RTT)
07/28/04
Systems Seminar - Claudiu Danilov

7. k-Multihoming versus k-Overlays
k-overlays offer marginal benefits over k-multihoming alone
Only a small fraction of transfers showed significantly better performance with k-overlays rather than k-multihoming
07/28/04
Systems Seminar - Claudiu Danilov

8. Reasons for performance difference
For large improvements (> 50 ms) performance is mainly due to avoiding congestion (small difference in propagation delay)
72% of the points are above y = x/2 line, which implies that most of the time improvement is due to finding physically shorter paths
07/28/04
Systems Seminar - Claudiu Danilov

9. Resilience to path failures
All-to-all pings between 68 nodes, every minute, for 5 days
A path declared lost if at least 3 consecutive pings are lost (3 minutes)
Paths with more than 10% lost probes are eliminated from this analysis
Epochs of failure intervals TF are computed
07/28/04
Systems Seminar - Claudiu Danilov

10. Resiliency to path failures (cont.)
07/28/04
Systems Seminar - Claudiu Danilov

11. Systems Seminar - Claudiu Danilov
Discussion
Overlays vs. Multihoming (benefits and drawbacks)
Competing or complementary ?
Cost of operation
Ease of deployment
Overlay link protocols …
Systems perspective
How to monitor different ISP connections with arbitrary destinations ?
What would be a good multihoming route control mechanism ?
What is a good overlay deployment strategy ?
07/28/04
Systems Seminar - Claudiu Danilov