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l7 inter domain routing protocols

l7 inter domain routing protocols - Lecture 7 Inter-Domain...

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Lecture 7: Inter-Domain Routing Credits: Based on lecture by Rob Sherwood
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What Last time: Intra-domain routing protocols (IGP) - Last time - OSPF link state - RIP distance vector Today: Inter-domain routing protocols (EGP) - Border Gateway Protocol v4 - Path vector routing protocol: list possible paths - No other EGP’s today. . . why?
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Why Inter vs. Intra? Why not just use OSPF everywhere? - E.g., hierarchies of OSPF areas - Hint: scaling is not the only limitation BGP is a policy control and information hiding protocol - intra == trusted, inter == untrusted
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Why Inter vs. Intra? Why not just use OSPF everywhere? - E.g., hierarchies of OSPF areas - Hint: scaling is not the only limitation BGP is a policy control and information hiding protocol - intra == trusted, inter == untrusted
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Why Study BGP? Critical protocol: makes the Internet run - Only widely deployed EGP Active area of problems! - Efficiency - Cogent vs. Level3: Internet partition - Pakistan accidentally took down YouTube - Spammers use prefix hijacking
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Outline History (very briefly!) Function Properties Policies Example Problems and proposed solutions
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History Why border gateway protocol? Historical distinction: - 1989: BGPv1, “directional” routing [RFC 1105] : - 1990: BGPv2, bunch of incompatible changes [RFC 1163] - 1991: BGPv3, resolves connection “collisions” [RFC 1267] - 1994: BGPv4 (proposed) [RFC 1654] - 1995: BGPv4 (actual), w. CIDR support [RFC 1771] - Latest revision of BGPv4 spec [RFC 4271] Additional information: - Application of BGP in Internet [RFC 1772] - Experience w. BGPv4 [RFC 1773] - Protocol analysis [RFC 1774]
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High Level Recall notion of Autonomous System (AS) - Organizations that participate in EGP - Assigned AS Number, originally 16 bits, now 32 [RFC 4893] Abstract each AS down to a single node Exchange prefix-reachability with all neighbors “I can reach prefix 171.67.0.0/14 through ASes 15444 3549 174 46749 32” Select a single path by routing policy Critical : learn many paths, propagate only one! - Add your ASN to advertised paths
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BGP State BGP speaker conceptually maintains 3 sets of state Adj-RIBs-In - Stands for “Adjacent Routing Information Base, Incoming” - Has unprocessed routes learned from other BGP speakers - Contains both reachable and unreachable routes (in case later become reachable and can be added to Loc-RIB) Loc-RIB (Local RIB)
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