26-January-2000

Mizzou Linux Users Group

AT&T Cable

AT&T @Home Cable Service

• Overview

• Technical Description

• Why to Chose a Cable Modem

• Problems and Issues

Overview

• What is AT&T @Home Cable?
• High speed Internet access through standard television cable
• Anywhere AT&T cable television service can be utilized AT&T @Home can be as well
• Service 100 percent launched in Columbia
• Installation within four weeks of intitial call
• Up to four IPs per cable modem
• Special deal: $19.95 for three months now

Technical Description

• Connection to service
• Computer connects to cable modem via ethernet card
• Cable modem connects to fiber node (each fiber node is equivalent to LAN) which converts signal from RF to light
• Fiber node connects to head end
• Head end connects to Regional Data Center (R.D.C.) via OS-3
• R.D.C. connects to Network Access Point (N.A.P.)
• N.A.P. goes out to Internet
• R.D.C connected together via OC-43 lines
• Data transfer
• Data moves accross modem in Frequency Modulation
• Modem data encrypted with 56 bit DES encryption
• Data moves upstream at speeds around 1 m.b.p.s at fastest but much slower downstream

Why to Chose a Cable Modem

• Alternatives
• ASDL from Socket costs $10 more per month and performance decreases as distance increases
• T1 Line is too costly
• 56 k.b.p.s. modem not fast enough

Problems and Issues

• No linux support
• Traffic issues
• Designed to handle 50,000 people (expandable)
• Speed decreases as more people use service on fiber node (peak time 5-10 p.m.)
• Number of computers on service
• Up to four computers only (including Sega Dreamcast)
• No computers outside premisis
• Packet sniffing
• All packets encrypted with 56 bit DES encryption

Last modified 16-Feb-2000
Neil Bradshaw