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BGP

BGP. Border Gateway Protocol. EE122 Section 3. Border Gateway Protocol. Protocol for inter-domain routing Designed for policy and privacy Why not distance-vector? Shortest path may not be policy-compliant …and policies vary across domains! Why not link-state?

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BGP

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  1. BGP Border Gateway Protocol EE122 Section 3

  2. Border Gateway Protocol • Protocol for inter-domain routing • Designed for policy and privacy • Why not distance-vector? • Shortest path may not be policy-compliant • …and policies vary across domains! • Why not link-state? • Everybody knows everything – privacy goes for a toss! • Enter path vector!

  3. BGP: Path Vector 0 A: 1 B: 2 1 2 A: 1 B: 2 A B

  4. BGP: Path Vector 0 A: 0 1 B: 0 2 B: 0 2 A: 0 1 1 2 A: 1 B: 2 A B

  5. BGP: Path Vector 0 A: 0 1 B: 0 2 1 2 A: 1 B: 1 0 2 A: 2 0 1 B: 2 A B

  6. BGP: Path Vector 0 A: 0 1 B: 0 2 A: 0 1 B: 0 Withdrawal - B: 0 2 Advertise - B: 0 1 2 A: 1 B: 1 0 A: 2 0 1 B: 2 A B

  7. BGP Relationships • Provider -> Customer: • Peer <-> Peer: A: 1 0 B: 1 0 C: 0 0 A: 1 B: 1 C: 0 1 1 2 A: 1 2 B: 2 C: 0 2 A B C

  8. It’s all about the money! • Customer pays provider • Peers don’t pay each other • Assume equal flow both ways • Routing policies try to minimize payment

  9. Typical Export Policy We’ll refer to these as the “Gao-Rexford” rules (capture common -- but not required! -- practice!)

  10. Gao-Rexford providers peers customers With Gao-Rexford, the AS policy graph is a DAG (directed acyclic graph) and routes are “valley free”

  11. Packets flow where money flows • Route Selection • Preference Order: Customer > Peer > Provider • Route Export Policy • Peers provide transit between their customers • Peers do not provide transit to each other

  12. Route Selection: Customer > Peer • Provider -> Customer: • Peer <-> Peer: A: 1 0 B: 1 0 C: 0 0 A: 1 B: 1 C: 0 1 1 2 A: 1 2 B: 2 C: 0 2 A B C

  13. Route Selection : Peer > Provider • Provider -> Customer: • Peer <-> Peer: A: 1 0 B: 1 0 C: 0 0 A: 1 B: 1 C: 0 1 1 2 A: 1 2 B: 2 C: 0 2 A B C

  14. Route Selection : Provider (no choice) • Provider -> Customer: • Peer <-> Peer: A: 1 0 B: 1 0 C: 0 0 A: 1 B: 1 C: 0 1 1 2 A: 1 2 B: 2 C: 0 2 A B C

  15. Route Export policy: Advertise customers • Provider -> Customer: • Peer <-> Peer: A: 1 0 B: 1 0 C: 0 0 A: 1 B: 1 C: 0 1 1 2 A: 1 2 B: 2 C: 0 2 A B C

  16. BGP Routing Game! • No talking! Communicate via pieces of paper • Route selection precedence • Customer > Peer > Provider • Export policy: Advertise customers • Message format: • Withdrawal - <host network>: <path> • Advertise - <host network>: <path> • Ping - <destination> • Goal: Reach steady state

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  19. Level3 Cogent Google Fiber Netflix Facebook Google East, Akamai: Verizon, Level3 KC: Google Fiber, Level3 East, Akamai: Verizon, Level3 West, Akamai: Comcast, Cogent Verizon Comcast FB, Google: Level3, Cogent Time Warner Cable People in Kansas City People on the West coast Akamai CDN People on the East coast People in the South

  20. Level3 Cogent Google Fiber Netflix Facebook Google East, Akamai: Verizon, Level3, Cogent West, Akamai: Verizon, Level3, Cogent Verizon Comcast Time Warner Cable People in Kansas City People on the West coast Akamai CDN People on the East coast People in the South

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