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Measuring BGP

Measuring BGP. Geoff Huston Telstra. Why. What is changing in the deployment environment? Are current address allocation policies still relevant? What are sensible objectives for address allocation policies?. Measuring BGP. Techniques Metrics Interpretation. Techniques.

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Measuring BGP

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  1. Measuring BGP Geoff Huston Telstra

  2. Why • What is changing in the deployment environment? • Are current address allocation policies still relevant? • What are sensible objectives for address allocation policies?

  3. Measuring BGP • Techniques • Metrics • Interpretation

  4. Techniques • Passive Measurement • Takes measurements from a default-free router at the edge of the local network • Easily configured • Single (Filtered) view of the larger Internet • What you see is a collection of best paths from your immediate neighbours eBGP Local AS Measurement Point

  5. Techniques • Multiple Passive measurement points • Measure a number of locations simultaneously • Can be used to infer policy AS2 AS1 AS3 Measurement Points

  6. Techniques • Single passive measurement point with multiple route feeds • Best example: • Route-views.oregon-ix.net • Operating since 1995 • 42 peers • Uses eBGP multihop to pull in route views

  7. route-views.oregon-ix.net>show ip bgp sum BGP router identifier 198.32.162.100, local AS number 65534 BGP table version is 4651390, main routing table version 4651390 116358 network entries and 2664238 paths using 106733862 bytes of memory 400080 BGP path attribute entries using 20804160 bytes of memory 327716 BGP AS-PATH entries using 8147076 bytes of memory 212 BGP community entries using 5344 bytes of memory Dampening enabled. 5796 history paths, 4151 dampened paths BGP activity 259000/138257 prefixes, 15859917/13175944 paths Neighbor V AS MsgRcvd MsgSent TblVer InQ OutQ Up/Down State/PfxRcd 4.0.0.2 4 1 405536 4764 4650716 0 0 2d09h 95769 12.127.0.249 4 7018 447139 4761 4650716 0 0 2d09h 95730 134.24.127.30 4 1740 368349 4756 4650716 0 0 2d09h 95845 134.55.20.229 4 293 260120 4769 4650716 0 0 3d07h 96192 144.228.241.81 4 1239 474733 4760 4650716 0 0 2d09h 95919 157.22.9.7 4 715 360065 4762 4650716 0 0 2d09h 99695 163.179.232.37 4 2551 462529 4760 4650716 0 0 2d09h 96461 165.87.32.5 4 2685 632135 9476 4650716 0 0 2d02h 95779 167.142.3.6 4 5056 345017 9484 4650716 20 0 06:28:17 97903 192.121.154.25 4 1755 412061 4759 4650716 0 0 2d09h 97203 193.0.0.56 4 3333 263659 4769 4650716 0 0 3d07h 98129 193.140.0.1 4 8517 356130 4759 4650716 0 0 2d09h 99649 195.66.225.254 4 5459 120794 4778 4650716 0 0 2d17h 37968 195.219.96.239 4 8297 448953 4761 4650716 0 0 2d09h 96995 202.232.1.8 4 2497 235843 4769 4650716 0 0 3d07h 96619 203.62.252.21 4 1221 585273 4753 4650716 0 0 04:58:24 111615 203.181.248.233 4 7660 297716 4760 4650716 0 0 2d09h 95296 . . .

  8. Techniques • Active Measurement Tests • Convergence • Announcement and withdrawal Reporting Points Monitoring Unit AS1 Route Injection Point Internet AS2

  9. Techniques • Active Measurement • Integrity of Announcements • Traceroute + AS Origin Does a traceroute match the advertised AS path? Sampling technique

  10. Metrics • BGP Tables can tell you: • Number of selected entries • Selected and non-selected entries • For each entry • Address span (start and length) • Origin AS • AS path • Dampened paths

  11. Metrics • What BGP metrics are useful and why? • Total Table Size and trend • Average prefix length used for switching • Announcement overlap (more specifics) • Aggregation possibilities • Per-prefix size and trend • Announcements and withdrawals • AS consumption • Inter-AS relationships

  12. Metrics • Interence metrics: • Incidence of Multi-homing • Inter-AS degree of connectivity • Stability of advertisements • Address Reachability per AS hop • Inter-AS relationships • (customer, peer, mixed)

  13. Interpretation • BGP is not a link state protocol • There is no synchronized overview of the entire connectivity and policy state • Every BGP viewing point contains a filtered view of the network • Just because you can’t see it does not mean that it does not exist • BGP metrics are sample metrics

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