Internet infrastructure and access

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Internet infrastructure and access

• Henning Schulzrinne
• Dept. of Computer Science
• Columbia University
• Fall 2003

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Internet backbones

• Classify ISPs into tiers
• tier 1 global reach, about 40
• British Telecom (BT), Cable Wireless, Global
  Crossing, Level 3, Sprint, MCI (UUnet), Verio
  (NTT),
• tier 2 regional
• tier 3 local
• Tier-1s typically use railroad tracks or
  pipelines as right-of-way
• some also lease (some) circuits from other
  providers
• at least 20,000 fiber miles
• Connect to local circuits via points-of-presence
  (POP)

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Internet backbones

• OC-3 (155 Mb/s), OC-12 (622 Mb/s), OC-48 (2.4
  Gb/s) or OC-192 (10 Gb/s)
• Usually, WDM or D-WDM (e.g., 16 ? x 2.5 Gb/s, up
  to 40 ?)
• 50 or 100 GHz optical spacing
• Fiber about 30,000-50,000/mile, almost all
  construction
• Transport POS (packet over SONET), MPLS, ATM, FR
  (edges)
• Backbone utilization no more than 30 typical
• needed for fault recovery

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Network utilization

• local phone line 4
• U.S. long distance switched voice 33
• Internet backbones 10-15
• private line networks 3-5
• LANs 1

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ISPs
America Online dial 25.3
MSN dial 8.7
United Online (Juno) dial 5.2
Earthlink dial 5.0
Comcast cable 4.4
SBC DSL 2.8
Verizon DSL 1.9
Cox cable 1.7
Charter cable 1.3
BellSouth DSL 1.2

• Many dial-up ISPs dont own modems ? use
  wholesale providers
• DSL cable modem
• modems are always oversubscribed (101?)

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Residential broadband
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Quick review DSL

• Uses spectrum from 25 kHz to 1.1 MHz
• ATM cells ? Ethernet ? PPP
• DSLAM aggregates circuits
• US local loops can be up to 18 kft long
• ADSL 16 Mb/s _at_ 4 kft, 10 Mb/s _at_ 6 kft (1.1 mi)
  downstream

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Commercial international backbone
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Internet2 backbone (Abilene)
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Internet2 (Abilene) 10 Gb/s network
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Peering

• Exchange of traffic between ISPs
• autonomous systems (AS)
• private peering vs. public peering
• public peering at MAE-East, MAE-West, AMS-IX,
• either a LAN or mesh of ATM/FR VCs
• Sender keeps all (SKA) only pay for rack space,
  not traffic
• Alternative transit payment (tier2 ? tier1)

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Peering points AMSIX in Amsterdam
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Peering point AMSIX