Multipath Routing

1
Multi-path Routing

• CSE 525 Course Presentation
• Dhanashri Kelkar
• Department of Computer Science and Engineering
• OGI School of Science and Engineering

2
Multi-path Routing

• A. Akella, B. Maggs, S. Seshan, A. Shaikh, R.
  Sitaraman, "A Measurement-Based Analysis of
  Multihoming", ACM SIGCOMM 2003.
• D. Andersen, A. Snoeren, H. Balakrishnan,
  "Best-Path v. Multi-Path Overlay Routing", IMC
  2003.

3
Multihoming Advantages The Gist

• A study of multihoming performance and
  reliability
• Data collected from Akamai content distribution
  network
• High-volume content providers
• Enterprises that mainly receive data
• Analysis
• Improve performance and reliability
• Choosing right set of providers important

4
Multihoming

• Technique to achieve resilience to service
  interruptions
• Customer network having more than one external
  link, either to single ISP or to different
  providers
• Mainly used for reliability

5
K-Multihoming

• Customer network multihomed to K (K2) service
  providers
• Expect incremental performance

6
Multihoming Two Models

• Enterprise perspective
• Route data being downloaded through appropriate
  ISP
• Web server perspective
• Route data being provided through appropriate
  ISP
• Does smart routing improve performance?
• Does choice of ISPs matter?

7
Data Collection Enterprise Perspective2-Multiho
ming

• Data set A1
• 27 monitoring nodes
• Two nodes per city connected to different ISP
• Every 6 min. nodes download objects from Akamai
  customers
• Log turnaround time for request

8
Data Collection Enterprise PerspectiveK-Multiho
ming (Kgt2)

• Data set H1
• Multiple Akamai servers per city
• Each server connected to different ISP
• Servers download from customers periodically
• Log avg turnaround time each
  hour

9
Performance 2-multihoming

• Use best provider for each download instead of
  single provider for all downloads
• Performance metric
• Measures how much each ISP loses compared to
  multihoming solution (1)

10
Performance K-Multihoming

• Performance metric
• particular K-multihoming solution
• Best multihoming obtained if we choose best of
  all ISPs

11
Enterprise 2-Multihoming Results

• 2-multihoming shows performance benefits but to
  varying degrees

12
Enterprise K-Multihoming Performance

• Each line represents different city
• No significant improvement after 4 or 5
• Knowing best ISP in advance is important

13
Data Collection Web Server Perspective
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Web Server Perspective Contd

• Data set A2
• In 5 metro areas, pick servers attached to
  distinct upstream ISPs
• Every 6 min. each server downloads 50 KB object
  from other Akamai servers
• Turnaround time for request

15
Web Server K-Multihoming

• Use Akamai servers to emulate multihomed data
  centers and their active clients
• Metric for comparison same as with enterprises
• Not much benefit beyond K4

16
Reliability

• Data set containing traceroute measurements from
  nodes of keynote systems to Akamai servers
• 50 geographically diverse keynote nodes, 2 per
  city
• 20 Akamai servers per city (top 20 ISP)
• Information about IP-level connectivity
• Robustness to IP-level failures

17
Reliability Metrics

• Fraction of total path diversity captured by
  solution
• Higher value shows better performance
• Degree of overlap in paths
• Lower value shows better performance

18
Reliability Analysis

• For both metrics, significant difference in
  optimal, average, and worse solution
• Difference about 80
• Choosing ISPs very crucial

19
Conclusion

• Multihoming helps, at least 20 improvement on
  average
• But not much beyond 4 providers
• Careful choice necessary
• Cannot just pick top individual performers
• Poor choice can affect performance significantly

20
Best-path vs. Multi-path Routing

• Analysis of performance of reactive and mesh
  routing
• Reactive routing measure path quality using
  probes and send on best path
• Mesh routing send redundant duplicates

21
Design

• Probe-based reactive overlay routing
• Periodic probes for availability, latency, loss
  rate
• Best path performance
• Redundant multi-path routing
• Sends redundant data to multiple paths
• Path independence

22
Routing Methods

• Direct Single packet, direct path
• Direct direct 2 packets, direct, no spacing
• DD 10ms 2 packets, direct, 10ms spacing
• DD 20ms 2 packets, direct, 20ms spacing
• Lat Reactive routing, min latency
• Loss Reactive routing, min loss
• Direct Rand 2 pkts, Redundant routing
• Lat Loss 2 pkts, Redundant multi-path

23
Duplication Reduces Loss Rate

• Type Loss
• direct 0.42
• direct direct 0.30
• dd 10ms 0.27
• dd 20ms 0.27
• Lat 0.43
• Loss 0.33
• Direct Rand 0.26
• Lat Loss 0.23

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Measurement Summary

• Redundant beats reactive for low loss
• Reactive finds specific good paths
• Latency improvements
• Low loss paths