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Global Internet Textbook Ch4.1

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  1. Global InternetTextbook Ch4.1 Instructor: Joe McCarthy (based on Prof. Fukuda’s slides) CSS 432: Global Internet

  2. Routing (section 3.3) Example rows from (a) routing and (b) forwarding tables • What if every router needed an entry for every • IP address? CSS 432: Global Internet

  3. Routing (section 3.3) Example rows from (a) routing and (b) forwarding tables • What if every router needed an entry for every • IP address? (232, or 4,000,000,000 possible hosts) • Network prefix? CSS 432: Global Internet

  4. Internet Routing 430K << 4B … But do we want 430K entries in every router table? Traffic just for update messages? Sep 2012: 430,000+ prefixes http://en.wikipedia.org/wiki/Border_Gateway_Protocol CSS 432: Global Internet

  5. Internet, circa 1990 Nationwide backbone (NSFNET) Regional networks (BARRNET, Westnet, …) End-user sites (Stanford, Berkeley, …) Each node is an Autonomous System (AS) CSS 432: Global Internet

  6. Internet Routing Sep 2012: 40,000+ ASs Sep 2012: 430,000+ prefixes http://en.wikipedia.org/wiki/Border_Gateway_Protocol CSS 432: Global Internet

  7. Hierarchical Routing (Autonomous Systems aka Routing Domains) • Divide the routing problem in two parts: • Routing within a single AS • Intra-domain routing protocol (each AS selects its own) • Routing between ASs • Inter-domain routing protocol(Internet-wide standard) CSS 432: Global Internet

  8. Intra-domain Protocols • RIP: Route Information Protocol • Distributed with BSD Unix • Distance-vector algorithm • Based on hop-count • OSPF: Open Shortest Path First • More recent Internet standard • Uses link-state algorithm • Supports authentication CSS 432: Global Internet

  9. Large corporation “ ” Consumer ISP Peering point Backbone service provider Peering point Consumer ” ISP “ “ Consumer ISP ” Large corporation Small corporation Inter-domain Protocol • Border Gateway Protocol, version 4 (BGP-4) • Internet is an arbitrarily interconnected set of ASs • Each AS has a Speaker (advertiser) • Goal: Reachability than optimality • Stub AS: • A single connection to another AS • Only carries local traffic • Multihomed AS: • Connections to multiple ASs • Refuses to carry transit traffic • Transit AS: • Connections to multiple ASs • Carries both transit & local traffic CSS 432: Global Internet

  10. 128.96 Customer P 192.4.153 (AS 4) Regional provider A (AS 2) Customer Q 192.4.32 (AS 5) 192.4.3 Backbone network (AS 1) Customer R 192.12.69 (AS 6) Regional provider B (AS 3) Customer S 192.4.54 (AS 7) 192.4.23 BGP Example • Speaker for AS2 advertises reachability to P and Q • Network 128.96, 192.4.153, 192.4.32 & 192.4.3can be reached directly from AS2 • Speaker for AS1 (backbone) advertises • Networks 128.96, 192.4.153, 192.4.32, and 192.4.3 can be reached along the path (AS1, AS2) • Networks 192.12.69, 192.4.54, 192.4.23can be reached along the path (AS1, AS3) • Speaker can cancel previously advertised paths CSS 432: Global Internet

  11. Routing Areas • AS divided into areas • Area 0 • Known as the backbone area (connected to the backbone) • Area Border Routers (ABRs): R1, R2, R3 • OSPF link state packets • Do not leave the area in which they originated (if they are not ABRs) • ABRs summarize routing information that they have learned from one area and make it available in their advertisements to other areas. CSS 432: Global Internet

  12. iGP + eGP Routing CSS 432: Global Internet

  13. IP Version 6 • Features • 128-bit addresses (classless) • multicast • real-time service • authentication and security • autoconfiguration • end-to-end fragmentation • protocol extensions • Header • 40-byte “base” header • extension headers (fixed order, mostly fixed length) • fragmentation • source routing • authentication and security • other options CSS 432: Global Internet