16-Interdomain - Interdomain Routing EE122 Fall 2011 Scott...

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1 Interdomain Routing EE122 Fall 2011 Scott Shenker http://inst.eecs.berkeley.edu/~ee122/ Materials with thanks to Jennifer Rexford, Ion Stoica, Vern Paxson and other colleagues at Princeton and UC Berkeley
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Announcements • Homework 3 will be released in a day or two – It is long, it is hard, and it is mean . – Picking up the pace, need to give you practice – We will provide help (office hours!) and give you time – This is the only way to prepare you for final…. • Piazza decorum meltdown – Please watch your tone – We will process this issue later…. 2
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Where are we? • Covered foundations (reliability, routing) • Covered essentials of today’s architecture – Naming, web, TCP • Now revisiting foundations – Congestion control – Routing: interdomain and advanced • Then on to various topics: – Eithernet, wireless, security, etc. 3
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4 Routing • Provides paths between networks – Prefixes refer to the “network” portion of the address • So far, only considered routing within a domain – All routers have same routing metric (shortest path) • Many issues can be ignored in this setting…. – No autonomy: central administrative control – No privacy issues: central administrative control – No policy issues: central administrative control • Not any more!
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5 Internet is more than a single domain… • Internet not just unstructured collection of networks – “Networks” in the sense of prefixes • Internet is comprised of a set of autonomous systems (ASes) – Independently run networks, some are commercial ISPs – Currently over 30,000 Ases • ASes are sometimes called domains – Hence “interdomain routing”
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6 Internet: a large number of ASes Large ISP Large ISP Dial-Up ISP Access Network Small ISP Stub Stub Stub
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7 Three levels in routing hierarchy • Within a single network: to reach individual hosts – To be covered in “Link-layer” lecture (ethernets, etc.) • Intradomain: routes between networks – Covered in previous routing lectures • Interdomain: routes between ASes – Today’s lecture • Need a protocol to route between domains – BGP is current standard
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A New Routing Paradigm • The idea of routing through networks was well- known before the Internet – Dijkstra's algorithm 1956 – Bellman-Ford 1958 • The notion of autonomous systems which could implement their own private policies was new • BGP was hastily designed in response to this need • It has mystified us ever since…. . 8
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9 Who speaks BGP? R border router internal router BGP R2 R1 R3 AS1 AS2 s Two types of routers s Border router (Edge), Internal router (Core)
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10 Purpose of BGP R border router internal router BGP R2 R1 R3 A AS1 AS2 you can reach net A via me traffic to A table at R1: dest next hop A R2 Share connectivity information across ASes
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11 I-BGP and E-BGP R border router internal router R1 AS1 R4 R5 B AS3 E-BGP R2 R3 A AS2 announce B IGP: Intradomain routing Example: OSPF I-BGP IGP
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16-Interdomain - Interdomain Routing EE122 Fall 2011 Scott...

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