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-1’s 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 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 don’t 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 Mb/s @ 4 kft, 10 Mb/s @ 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