So: The Internet is a global collection of voluntarily connected networks.

Most important players: Internet Service Providers (ISPs)

Definition: An ISP sells to businesses, organizations, and end-users connectivity to the global public Internet.

• To sell connectivity to the global public Internet, each ISP needs to get connectivity to the global public Internet
• ISPs are both clients and providers
• ISPs buy connectivity from upstream ISPs (wholesale), and sell it to customers (retail or wholesale)
  

Transit vs. Peering

Transit = business relationship where one ISP provides (usually sells) connectivity to all destinations on the global Internet.

• Bilateral business & technical arrangement.
• Transit provider carries traffic to 3d parties or from 3d parties to customer (end point).
• Most transit agreements: transit provider will carry traffic to/from its other customers AND to/from every destination on the Internet.
  • I.e., transit provider gives clients access to all network routes in its routing table.
• Defined price for access to entire Internet.
  • Usually on a volume basis, measured in Mbps
• From customer perspective: Simple relationship
  • Customer pays; transit provider gives access to entire Internet
  • Generally includes Service Level Agreement (SLA), installation & Network Operations Center (NOC) support
    

   

  Transit diagram

Peering = business relationship where 2 ISPs each give reciprocal access to their own customers

• Bilateral business & technical arrangement
• 2 providers agree to accept traffic from one another and from one another’s customers (and their customers’ customers)
• No obligation to carry traffic to 3d parties
• No cash payments involved (more like barter); no settlement
• No Service Level Agreement (SLA)
  

  Peering diagram 0

  Peering diagram 1

  Peering diagram 2

• ISP must either
  • Exchange traffic directly with other ISPs (peering), or
  • Pay a larger ISP to do it (transit)
• Because an ISP cannot peer with every other ISP in the world (10,000+), most ISPs try to do both:
  • Exchange as much traffic as possible with peers, AND
  • Pay for the portion that can’t be exchanged via peers
• ISP goal: Minimize transit to minimize costs

• The larger ISPs that sell transit to developing countries are nearly always US-, European-, or Japanese-owned
• In most developing countries, domestic ISPs do not peer with each other
• Any country whose ISPs do not peer with each other relies exclusively on transit, and is:
  • (a) Needlessly exporting capital, and
  • (b) Effectively subsidizing Internet in the developed world.
• Developing country payments for transit are not small
  

• Each ISP has its own international connection to the global Internet
  • Satellite or fiber
• Even domestic traffic has to flow over international links before being routed back to another local ISP
• This is needlessly expensive, and limits services (high latency)
• Without domestic peering, it’s actually better to host online content and services offshore

  Africa Connectivity Map
  

• Without significant domestic traffic interchange, there’s little incentive to host domestic Internet content
• Result: Few domestic content sources for developing world Internet users
  • And continued reliance on US-generated content, with US-generated advertising, from US companies pushing US products

• ISPs act like resellers, not network backbones
• ISPs each have independent satellite links to upstream providers
• Little cooperation ==>Little interconnection
• Few gateways ==> More centralized, easier to manipulate, less resilient
• Result: connectivy in developing countries is slower, less reliable, more expensive
  

• A shared switching facility that allows ISPs to exchange Internet traffic with each other.
• Enables local exchange of local Internet traffic
• Lowers cost and improves service
• 150 IXPs throughout the developed world
• Only a handful in developing countries
  • Africa: South Africa, Kenya, Mozambique, Uganda, Tanzania, D.R. Congo, and Egypt

• A room with a shared computer (a switch).
• Multiple ISPs run their wires into the room, install a router next to the switch, make a physical connection between the router and the switch, and then use the switch to exchange traffic with one or more of the other ISPs that are connected to it.

  Photo: Nepal IXP (courtesy PCH)

  More on Switch vs. Router

• Cost
  • Internet vs. telephone network
  • Peering vs. transit
• Quality of Service
  • Satellites are slow
  • Latency (slowness) makes lots of Internet services impractical, forces hosting abroad

• TESPOK
• Telkom Kenya
• KIXP
  • 2000: ~30% of upstream traffic was to a domestic destination
• Communications Commission of Kenya
  • November 2001: licensing order

   

  Results:

  • KIXP reduced latency from an average fo 1200-2000 milliseconds (via satellite) to 60-80 milliseconds (via KIXP).
  • Monthly bandwidth costs for a 64 kbit/s circuit dropped from US$ 3375 to US$200, and for a 512 kbit/s circuit from US$9546 to US$650
  • CCK is now an evangelist of IXPs

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