Internet infrastructure and access Henning Schulzrinne Dept. of Computer Science Columbia University Fall 2003

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)

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 λ x 2.5 Gb/s, up to 40 λ) – 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

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

ISPs America Onlinedial25.3 MSNdial8.7 United Online (Juno)dial5.2 Earthlinkdial5.0 Comcastcable4.4 SBCDSL2.8 VerizonDSL1.9 Coxcable1.7 Chartercable1.3 BellSouthDSL1.2 Many dial-up ISPs dont own modems use wholesale providers DSL + cable modem modems are always oversubscribed (10:1?)

Residential broadband

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 4 kft, 10 6 kft (1.1 mi) downstream

Commercial international backbone

Internet2 backbone (Abilene)

Internet2 (Abilene) 10 Gb/s network

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)

Peering points: AMSIX in Amsterdam

Peering point: AMSIX