Internet Architecture: A Highlevel Overview

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Internet Architecture A High-level Overview

• AFIX Technical Workshop
• Session 1

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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

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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

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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

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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

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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).

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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!

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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

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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 others customers

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The transit relationship
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The peering relationship
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To peer or not to peer?
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• 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 whod rather sell
  transit!

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The Internet without peering
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The Internet without peering

• Backhaul is expensive for both parties
• Not cost effective

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IXPs shorten the chain
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..and grow local bandwidth
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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

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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

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Exchange points
Gateways
IXP
ISPs connect at Internet Exchange Points to
exchange traffic
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Conceptual Diagram of XP
Exchange Point Medium
Customer Router
Customer Router
Customer Router
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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

USA
200-900ms
200-900ms
200-900ms
5-20ms
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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!

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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

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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

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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

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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.