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BGP Stability Study

BGP Stability Study. http://psg.com/~avri/irtf/BGP-stability-charter.html. Why Study BGP Stability.

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BGP Stability Study

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  1. BGP Stability Study http://psg.com/~avri/irtf/BGP-stability-charter.html

  2. Why Study BGP Stability • The starting hypothesis for the BGP Stability Routing Research Sub Project is that problems in IBGP are one of the prime causes in the demonstrated lack of full global BGP convergence in the Internet.

  3. Operator struggles with IBGP/BGP • Persistent Route Oscillation Condition (Danny McPherson, et. all) • RFC • The problem with BGP Convergence, • Craig Labovitz, Microsoft Research/Merit, and Abha Ahuja, Internap/Merit. NANOG 18, February 2000. • Worse than RIP • Happy packets by Randy Bush, et al. • http://www.nanog.org/mtg-0405/pdf/bush.pdf

  4. 4 different focuses • Measure what happens • Review Existing work: • Beacon, Registries, etc. • New ideas: • Use Route Flap damping code to save • Reproduce in Lab • Can we re-produce in the lab what we see in the net • Internet mix versus generated traffic • Benchmarking texts • Create Theoretical Modules to match • Distance Vector • BGP depends on IGP • Test out new algorithms proposed • Simulation, Code new algorithms, Benchmark

  5. Steps of Work • Create full list of existing studies and work • Cull existing work to find effects of IBGP on global convergence • Only if needed: (but probably will) • Create new investigation and data collection methods to define problem • Test existing proposals for improvements • Make Recommendations

  6. Solving the problem • Lots of passion in this • WIRED workshop inspired mixture of research, discussion and testing • Not just academics • Not just vendors • Not just operators • Both Historical trends • And most recent input

  7. Convergence Testingmethodology

  8. Convergence issues VPLS BGP Auto- Discovery LDP/ OSPF convergence Impacts BGP Convergence IGP Convergence Link Failure Detect impacts

  9. But BGP has other issues • BGP convergence problems • IGP fail-over in IBGP • TCP impacts BGP • Full mesh IBGP mesh • Topologies may cause BGP to never converge • Parallel BGP calculations • BGP policy may be costly to run • Has inflexible boundaries to BGP (iBGP or EBGP) • Lacks of policy verification prior to load • Lacks ability to synchronize BGP policy

  10. Convergence test methodology • IGP • BGP • Multicast

  11. IGP Convergence methodology

  12. Types of topology Lightly connected (1-2 links/ router) Medium connected (2-3 links/router Highly connected (4-5 links/router) Least Squares IGP Topologies

  13. IGP Convergence times LoC(p) = D + O + QSP + (h * F) + SPF(n) + RIB (p) + FIB(p) + DD + CRR • D: Failure is detected (down fast, up slow • Link failure (802.1g, SONET timers (down fast, 10 ms up)) • O: New LSP is originated • QSP: cumulative queuing, serialization, propagation, • H*F: LSP is flooded up to rerouting node • SPF: Shortest path calculation • RIB: RIB is updated • FIB: FIB is updated • DD: LCs are updated • CRR: BGP recursion is fixed

  14. OSPF Performance • The deployment of the OSPF code may be in a single area or in multiple areas. Large amounts of external routes are not normally injected in the OSPF calculations. Due to the differences in the way OSPF is deployed, the OSPF performance numbers are indicated in the following areas: • Inter-Area SPF computation • Intra-Area Database Lookup • Intra-Area SPF calculations for AS-External (type-5) and NSSA Computations • Summary Computations for an Area Border Router [Summary network (type-3) and Summary ASBR (type-4)]

  15. BGP convergence

  16. BGP convergence • Debated, but not well understood • Lots of research papers (some good, lots bad) • BGP beacon experiments • Trying to insert change and measure at temperature points

  17. Multi-AS Convergence for Beacon Beacon 1st change 1st change AS 2 AS 1 AS 3 Last change Last change • Convergence Terms • 1st change detected in AS 1 = beacon • 1st change detected in AS 2 • 1st change detected in AS 3 • last change detected in AS 1 • last change detected in AS 2 • last change detected in AS 3 Easy to see in line topology

  18. D: Failure is detected LoC(p): IGP convergence Uo: New Update is originated TR – transmission of Update QSP: cumulative queuing, serialization, propagation RS-Policy: Route Selection Policy PV: Path Vector Calculation RIB: RIB is updated DS-Policy: Distribution Policy TX – Update is transmitted FIB: FIB is updated BGP – Route Recursion is check I-BGP Convergence for an AS BGPoc(p) = D + LoC(p) + Uo + N-Peers (Tr + QSP + RS-Policy + PV + RIB + DS-Policy+ RIB + Tx) + FIB + CRR Time = 1st change to last change in each AS

  19. Key factor is the IBGP convergence Minor factors – E-BGP transmission BGP ASconvergence BGPconvergence = Max(sum(IBGPconvergence_last)) BGPchange = Min(sum(IBGPnotify_first))

  20. How to Join • IRTF page will link to • www.ndzh.com/IBGP for public information • Send a note to skh@nexthop.com or avri@psg.com • Start with reading list • You can catch up in August and September • Bi-Weekly conference calls • Face-to-Face meetings • September aligned with RIPE in Europe • October aligned with NANOG • Possible Japanese/China meeting in Early October

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