Internet%20Routing%20Dynamics%20and%20NSIS%20Related%20Considerations%20draft-shen-nsis-routing-00.txt

1
Internet Routing Dynamics and NSIS Related
Considerations draft-shen-nsis-routing-00.txt

• Charles Shen, Henning Schulzrinne, Sung-Hyuck Lee
• IETF61 Washington DC
• November 2004

2
Outline

• An Internet Routing Dynamics Measurement
• Measurement Methodology
• Summary of Results from NSIS Perspective
• NSIS-Concerned Route Changes
• Typical NSIS Deployment Models
• Evaluation of Packet TTL Monitoring Route Change
  Detection
• Conclusion and Next Step

3
Measurement Methodology

• Traceroute end-to-end path characterization
• 24 Public servers located in US, Iceland,
  Netherlands, Australia, Germany, Switzerland,
  Bulgaria, Sweden and Thailand.
• Independent, exponential sampling interval
  15/30min per-site (2.75h/11.5h per-path)
• Selected paths with 10min fixed interval
• Between April and August 2004

4
Summary of Results (I)

• Route Prevalence and Route Persistence
• Paths strongly dominated by a single route
• Significant site to site variation exists.
• Adaptive approach for NSIS and routing
• Different Types of Route Changes
• Wide range of time / location scales
• Majority with no change of total hop count
• Route splitting and load balancing

5
Summary of Results (II)

• Accuracy of Measuring Path Characteristics
• 10-min fixed / 2-hour exponential interval
• Both capture the same number of routes, AS-paths
  changes
• The latter missed about half the number of
  routes, AS-paths and changes.
• Essentially site-to-site variation adaptive
  mechanism eg. Refresh?
• Impact of multi-homing
• AS level route changes and asymmetric routing
• An example
• change of main outgoing ISP from month to month
• but still occasionally use the previous ISP
  (10-30min)
• No change of incoming ISP

6
NSIS-Concerned Route Changes

• Generic route change
• Inter-AS
• Intra-AS Ingress-point, Egress-point, Mid-point
• Deal with all generic route changes only in a
  full NSIS model
• But a mixed NSIS deployment model more likely
• NSIS-concerned route changes (NCRCs)
• Involving change of NSIS entities in the path
• Subsets of generic route changes

7
Typical NSIS Deployment Models

• AS model
• a central NE in each AS
• NCRCs equivalent to inter-AS route changes (RCs)
• Entry model
• ingress routers of ASes are NEs
• NCRCs - inter-AS and intra-AS ingress route
  changes
• Border model
• both ingress and egress routers of ASes are NEs
• NCRCs inter-AS, intra-AS ingress and egress
  route changes
• Edge model
• access routers of src/dst sites are NEs.
• NCRCs inter-AS RC involving the first or last
  AS, intra-AS ingress RC in the first AS, intra-AS
  egress RC in the last-AS.

8
TTL Monitoring Evaluation (I)
Description DS I DS II DS III
TTL-visible RCs 38 25 23
AS level RCs 18 8 8
TTL-visible AS level RCs 77 83 88

• Overall TTL-visible RCs not so promising
• Most concerned are non-trivial RCs
• Pretty good for AS level changes

9
TTL Monitoring Evaluation (II)
NSIS Model DS I DS II DS III
AS Model 77 83 88
Entry Model 51 41 40
Border Model 45 39 38
Edge Model 74 90 92

• TTL method more effective in these models
• Ratio higher in sparser models
• Generic mixed model falls between these results

10
Conclusions and Future Work

• A recent end-to-end routing measurement
• Different Route Changes require different
  handling
• routing monitoring inside the network for
  frequent yet local route changes caused by route
  splitting or load balancing.
• simple packet TTL monitoring reasonably good for
  NSIS-concerned route changes in typical NSIS
  deployment models.
• More route change detection methods to be
  evaluated.