Using a Cable Modem at Home

1
Using a Cable Modem at Home

• Tim Adye
• Particle Physics Department
• Rutherford Appleton Laboratory
• PPD Christmas Lectures
• 17th December 2001

2
Home Internet Options

• Traditional dialup modem
• Maximum baud rate 56 kbits/s (often less)
• Can be unreliable
• Dialup times 30s
• Free services available, but often heavily
  oversubscribed
• ISDN
• 64 kbits/s (can be doubled by using two lines)
• Fast dialup 1s
• Available anywhere
• ADSL
• 500/250 kbits/s (download/upload)
• Only available in some areas?
• Various companies

3
Home Internet Options

• Cable modem
• 512/256 kbits/s (cheaper 64 kbits/s option
  available)
• Always on
• Only available in some areas
• NTL and Telewest
• Cheapest broadband option, if available
• I have a 512 kbits/s NTL Cable Modem (Oxford).
• Everyone I know with broadband internet access
  has an NTL Cable Modem
• The rest of this talk is on this option only

4
Cable Modem Availability and Price

• NTL claims to be available in Abingdon, Bicester,
  Oxford, Wallingford, Wantage, Newbury, Reading
• Not everywhere in those areas
• Check you area at www.ntl.com/broadband
• uses your postcode
• Could also check www.telewest.co.uk
• NTL Cable Modem cost
• 35/month (includes cable modem box rental) or
• 30/month 149 (to buy cable modem box)
• Includes phone line
• Can also be combined with cable TV
• better deal if you have both
• Installation is 25

5
My experience of the NTL service

• Arranging for an engineer to call (installation
  or service) is really slow and frustrating
• Notoriously bad call centre
• NTL engineers were excellent
• Installed phone, cable TV, cable modem sockets
  just where I wanted them (at different ends of
  the house)
• Took a couple of hours
• Service has been pretty reliable
• 4 overnight outages since February
• One longer problem
• Took several days to arrange for an engineer to
  call
• Fix was trivial (removing an attenuator on the
  coax cable) now I know what to try

6
Installation

• Cable modem box
• Size of a large paperback (single edition LotR?)
• Coax cable to socket in the wall
• Socket does not need to be near TV/phone sockets
• Requires ethernet (10Base-T) or USB on your PC
• Works with Windows, Linux, or Mac
• Ive only used Windows
• Brief tests with Mannys Linux PC were
  unsuccessful
• USB only with Windows 98/ME/2000
• Supports DHCP, so software setup is simple
• just like a laptop at RAL
• Using more than one PC is complicated
• Even switching PCs isnt trivial

7
Documentation

• NTL Documentation is really basic
• Usually enough to get you started
• It took me some time to discover more details
• Firewall configuration
• Transparent web cache
• Cable modem diagnostics
• Speed tests
• until I discovered these excellent pages
• http//homepage.ntlworld.com/robin.d.h.walker/

8
Speed

• Bandwidth limited at
• 512 kbits/s download
• 128 kbits/s upload
• Could be slower if demand is heavy
• I usually see the full rate, but maybe Oxford is
  a luddite area

9
What it feels like

• With a 56kbits/s modem (usually connecting at 33
  kbits/s)
• Convenient ssh connections to RAL/CERN/SLAC
• Unreliable connection could interrupt work at the
  wrong time
• Most X-Windows applications (eg. xterm, emacs)
  unusable
• PAW possible, but slow
• No problem downloading small files (up to 1 MB)
• With cable modem
• Reliable ssh connections
• X-windows mostly OK
• xterm, emacs, PAW nearly as good as at RAL
• Heavy applications still sluggish, but many
  normally run locally, eg. Netscape, Acrobat
• No problem downloading medium-sized files (up to
  20 MB)
• Accessing PPD NT disk shares can still be slow ?

10
Advantages of being Always On

• No dial up time
• No contention with phone
• Can run servers
• Allows access to your home machine from work
• Useful to pick up files you forgot to bring to
  work
• Can run ftp, web, login I just use sshd
• IP address changes every few days, so need to use
  DNS service, eg. DNS2Go
• NTL forbid high bandwidth ftp/web servers

11
Security implications of being Always On

• Need to be more careful about security
• Hackers scan for security holes
• More chance theyll find you if you are always
  connected, and have the same address
• Unless you really know what youre doing, make
  sure you disable
• File and printer sharing (Windows)
• All unused inetd services (Linux)
• Consider setting up a firewall
• After trying several firewalls for Windows (eg.
  ZoneAlarm), I use Tiny Personal Firewall
  (www.tinysoftware.com)
• Virus checking is even more important

12
Accessing RAL

• RAL internal web pages and services are not
  directly available
• Eg. PPD internal page, RAL Information for Staff,
  PPD Unix systems, NT disk shares
• Sometimes there are alternatives
• RAL Notices can be accessed with a password
• ssh to csf and then to PPD Unix
• NT disks can be read via ftp
• You can also set up a virtual private network
  connection to RAL (AKA PPTP)

13
Accessing RAL VPN

• After logging in with your Federal ID/password,
  you tunnel inside the firewall
• See RAL PC Support pages (Network services
  PPTP)
• NB. PC Support pages only accessible within RAL!
• Slower than a direct connection
• Also useful when at CERN, SLAC, etc.

14
Conclusions

• Once installed, cable modem is fast and reliable
• If you have 35/month to spare
• Be careful of hackers
• PPTP to RAL can be very useful