Computer Networking › Section E · The network layer: control plane › Topic E.3
Routing among ISPs: BGP
OSPF finds paths inside one network, but a packet from Lagos to Lima crosses many networks owned by companies that compete, cooperate and bill each other. The Border Gateway Protocol glues them together, and its choices are driven as much by business as by distance.
In this topic
- What BGP must do
- Sessions: eBGP and iBGP
- Attributes: AS-PATH and NEXT-HOP
- Hot potato routing
- The route-selection procedure
- Worked example: choosing among three routes
- Policy: customers, peers and providers
- Worked example: who hears which route?
- Anycast, getting online, and security
- Common mistakes to avoid
- Key takeaways
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