1. Internet Architecture: A High-level Overview AFIX Technical Workshop Session 1

2. AFIX Technical Workshop: Session 1 Outline of content The underlying structure of the Internet and the forces that have shaped it. The concepts of peering and transit A general overview of exchange points (IXPs) The state of IXPs and peering in Afrca

3. AFIX Technical Workshop: Session 1 History: Where it all started Way back in the dawn of Internet time (1969!): ARPANET 1972 DARPA-sponsored “Internetting project” to develop communication protocols for linked packet networks. TCP/IP written early 1970s

4. AFIX Technical Workshop: Session 1 Some key decisions Independent networks: no modification to reach Internet Networks linked by gateways which transmit data packets but retain no information about traffic Use the fastest available route for each packet Gateways to route traffic without discrimination Operating principles freely available to all

5. AFIX Technical Workshop: Session 1 Towards the net as we know it 1970s: e-mail, first small-scale commercial services, Usenet, Unix networking for universities 1980s: Bitnet, CSNet, EuNet, EARN. Internet hosts:1969 – 4 1981 – 210 1984 – 1,000 1986 – 5,000 1987 – 28,000 1989 – 130,000

6. AFIX Technical Workshop: Session 1 Key growth enablers The Domain Name System (DNS) Replaced single static host file database with dynamic hierarchical structure. NSFNet US backbone for all university traffic. Broke bottleneck, encouraged use. Exclusion of commercial users encouraged growth of private ISPs (UUNET 1987).

7. AFIX Technical Workshop: Session 1 1990s: Birth of the web 1990: Hosts grew to 300,000 Archie (first search engine) 1991:Private access to NSFNet Tim Berners-Lee developed HTTP and HTML Internet: A network of networks (infrastructure) Web: Information space – abstract!

8. AFIX Technical Workshop: Session 1 Network Access Points 4 original NAPs, all in US, to provide access to NSFNet (“onramps”) Regional access providers developed to aggregate traffic – direct interconnection led to NSFNet obsolescence. Multiplication of peering and exchange points

9. AFIX Technical Workshop: Session 1 The role of IXPs today The Internet would not exist without agreements to exchange traffic!!! Competitor ISPs must co-operate to serve their clients Two main forms of traffic exchange: Transit – sell access to all destinations in routing table Peering – access to each other’s customers

10. AFIX Technical Workshop: Session 1 The transit relationship

11. AFIX Technical Workshop: Session 1 The peering relationship

12. AFIX Technical Workshop: Session 1 To peer or not to peer? ProsCons Lower transit costsTraffic asymmetry Lower latencyLoss of transit sales Increased usageResource use ISPs can offer more and better services No service guarantees Increased customer satisfaction

13. AFIX Technical Workshop: Session 1 “The overall structure of the Internet is one where there is a strong business pressure to create a rich mesh of interconnection at various levels” Less easy for African ISPs to peer with international providers who’d rather sell transit!

14. AFIX Technical Workshop: Session 1 The Internet without peering

15. AFIX Technical Workshop: Session 1 Backhaul is expensive for both parties Not cost effective Internet A B The Internet without peering

16. AFIX Technical Workshop: Session 1 Domestic interconnectionInternet A B IXPs shorten the chain…

17. AFIX Technical Workshop: Session 1..and grow local bandwidth

18. AFIX Technical Workshop: Session 1 The rationale for IXPs Two ISPs in a market: Peer directly More than two: Peer at an exchange point “A facility operated by a single entity to facilitate the exchange of Internet traffic between three or more ISPs”. Closer = cheaper, faster, more efficient

19. AFIX Technical Workshop: Session 1 How an IXP works Major providers connect their networks and exchange traffic High-speed network or switch Simple concept - anyplace where providers come together to exchange traffic

20. AFIX Technical Workshop: Session 1 Exchange points ISPs connect at Internet Exchange Points to exchange traffic ISP A Gateways IXP ISP BISP C

21. AFIX Technical Workshop: Session 1 Conceptual Diagram of XP Customer Router Exchange Point Medium

22. AFIX Technical Workshop: Session 1 Why use an Exchange Point? KEEP LOCAL TRAFFIC LOCAL!! ISPs within a region peer with each other at local exchange No need to have traffic go overseas only to come back ISP AISP B 200-900ms USA 5-20ms 200-900ms

23. AFIX Technical Workshop: Session 1

24. The African picture 1.5Gbps outgoing bandwidth (2002) 13Mbps intra-African!!! High international tariffs discourage multiple links Lack of peering has cascading effects – eg many African websites are hosted offshore!

25. AFIX Technical Workshop: Session 1 Major issues for the African Internet International bandwidth prices are biggest contributor to high costs African users effectively subsidise international transit providers! Fibre optic links are few and expensive  reliance on satellite connectivity High satellite latency  slow speed, high prices Growth of Internet businesses is inhibited

26. AFIX Technical Workshop: Session 1 The solution: IXPs for Africa So far, 10 out of 53 countries have IXPs (2003 count) More IXPs  lower latency, lower costs, more usage Both national and regional IXPs needed Also needed: regional carriers, more fibre optic infrastructure investment

27. AFIX Technical Workshop: Session 1 Obstacles Current providers (cable and satellite) have a lot to lose Many of these have close links to regulators and governments Regulatory regimes on the whole closed and resistant to change Sometimes ISPs themselves are unwilling to co-operate

28. AFIX Technical Workshop: Session 1 Solutions Education and lobbying! Players: AFRISPA, AFIX-TF, CATIA, AFNOG This workshop is part of the process Later sessions will deal in more detail with the practical and political issues.