1. Internet Routing Dynamics and NSIS Related Considerations draft-shen-nsis-routing-00.txt Charles Shen, Henning Schulzrinne, Sung-Hyuck Lee IETF#61 – 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) DescriptionDS IDS IIDS III TTL-visible RCs38%25%23% AS level RCs18%8% TTL-visible AS level RCs77%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) TTL method more effective in these models Ratio higher in sparser models Generic mixed model falls between these results NSIS ModelDS IDS IIDS III AS Model77%83%88% Entry Model51%41%40% Border Model45%39%38% Edge Model74%90%92%

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.