Measuring bgp
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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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Measuring bgp

Measuring BGP

Geoff Huston

Telstra


Measuring bgp

Why

  • What is changing in the deployment environment?

  • Are current address allocation policies still relevant?

  • What are sensible objectives for address allocation policies?


Measuring bgp1

Measuring BGP

  • Techniques

  • Metrics

  • Interpretation


Techniques

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


Techniques1

Techniques

  • Multiple Passive measurement points

    • Measure a number of locations simultaneously

    • Can be used to infer policy

AS2

AS1

AS3

Measurement Points


Techniques2

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


Measuring bgp

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

. . .


Techniques3

Techniques

  • Active Measurement Tests

    • Convergence

      • Announcement and withdrawal

Reporting Points

Monitoring Unit

AS1

Route Injection Point

Internet

AS2


Techniques4

Techniques

  • Active Measurement

    • Integrity of Announcements

      • Traceroute + AS Origin

        Does a traceroute match the advertised AS path?

        Sampling technique


Metrics

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


Metrics1

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


Metrics2

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)


Interpretation

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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