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An Analysis of BGP Convergence Properties

An Analysis of BGP Convergence Properties. Introduction The BGP protocol NP completeness Routing anomalies Complexity analysis Summery. Introduction (BGP). BGP - the de-facto EGP. Policy-based path-vector protocol. nlri, next-hop, as-path, loc-pref

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An Analysis of BGP Convergence Properties

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  1. An Analysis of BGP Convergence Properties • Introduction • The BGP protocol • NP completeness • Routing anomalies • Complexity analysis • Summery

  2. Introduction(BGP) • BGP - the de-facto EGP. • Policy-based path-vector protocol. • nlri, next-hop, as-path, loc-pref • Implemented with little global knowledge. • Protocol divergence. • Dynamic solution. • Static solution. Static Solution: • Programs Routing Policies Analysis • The Route Arbiter Project • Routing Policy Specification Language (RPSL). • Internet Route Registries (IRRs). • Software Tools (RAToolSet).

  3. Introduction(NP-Completeness) • Non Deterministic Turing Machine (NDTM). • NP problems class. • NP-Complete problems class. • Reductions. • ANP-Hard, ANP  ANP-Complete. • The 3-SAT problem: (xyz)(xyz)(xyz)

  4. Routing Anomalies The DISAGREE System • AS 1 prefers route 1-2-0. • AS 2 prefers route 2-1-0.

  5. Routing Anomalies

  6. Routing Anomalies The BAD GADGET System • All AS want to reach destination d in AS 0. • Each AS prefers the counter-clockwise path of length 2.

  7. Routing Anomalies The BAD GADGET System

  8. Routing Anomalies The BAD GADGET System • All AS 2 export rules: • nlri = d  loc-pref = 1 • AS 2 import(2<-1) rules: • (nlri = d  as-path = [3,0])  loc-pref = 2 • nlri = d  loc-pref = 1 • AS 2 import(2<-3) rules: • nlri = d  loc-pref = 1

  9. Complexity Analysis The ASSIGN System An example of a 3-SAT problem: (xyz)(xyz)(xyz)

  10. Complexity Analysis The ASSIGN System X=True, Y=False, Z=False

  11. Complexity Analysis REACHABILITY (single destination)

  12. (xyz)(xyz)(xyz) C2 import(C2C1) rule: • nlri = d  (x  as-path  y  as-path  z  as-path)  loc-pref = 1

  13. Complexity Analysis ASYMMETRY

  14. Complexity Analysis SOLVABILITY (single destination)

  15. Complexity Analysis Relevant Routing Issues • REACHABILITY. • ASYMMETRY. • SOLVABILITY. • TRAPPED. • K-ROBUST. • UNIQUE.

  16. Summery Static Analysis approach problems: • Routing policies are not shared. • Complexity results  A need to rely on heuristics analysis rather than on exact analysis.

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