eBGP over iBGP Shortest IGP path cost to next hop implements hot potato routing

Ebgp over ibgp shortest igp path cost to next hop

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eBGP over iBGP Shortest IGP path cost to next hop: implements “hot potato” routing Router ID tiebreak: arbitrary tiebreak, since only a single “best” route can be selected BGP routes have the following attributes, on which the route selection process is based: 19 BGP Route Selection CSE 222A – Lecture 3: Packet Forwarding
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Hot - Potato Routing Prefer route with shorter IGP path cost to next-hop Idea: traffic leaves AS as quickly as possible I New York Atlanta Washington, DC 5 10 Dest . Common practice: Set IGP weights in accordance with propagation delay ( e.g., miles, etc.) Traffic 20 CSE 222A – Lecture 3: Packet Forwarding
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Hot - Potato Dynamics Small changes in IGP weights can have significant impact 21 I San Fran New York LA 5 10 Dest . Traffic 11 CSE 222A – Lecture 3: Packet Forwarding
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Internet Business Model (Simplified) Customer/Provider: One AS pays another for reachability to some set of destinations “Settlement-free” Peering: Bartering. Two ASes exchange routes with one another. Provider Peer Customer Preferences implemented with local preference manipulation Destination Pay to use Get paid to use Free to use 22 CSE 222A – Lecture 3: Packet Forwarding
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Measurement With Traceroute Traceroute tool to measure the forwarding path u Send packets with TTL=1, 2, 3… u Record the source of the “time exceeded” message Useful, but introduces many challenges u Path changes u Non-participating nodes u Inaccurate, two-way measurements source destination TTL=1 Time exceeded TTL=2 23 CSE 222A – Lecture 3: Packet Forwarding
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For Next Class… Read P&D Chapter 4 Read and review Paxson ’97 Keep thinking about term project ideas/groups u Initial ideas due next Thursday u Email to me 24 CSE 222A – Lecture 3: Packet Forwarding
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  • Fall '08
  • Vahdat,A

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