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 Tim Adye

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 Tim Adye

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 Tim Adye

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 Tim Adye

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 Tim Adye

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 • I’ve only used Windows • Brief tests with Manny’s 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 isn’t trivial Tim Adye

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/ Tim Adye

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 Tim Adye

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 Tim Adye

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 Tim Adye

11. Security implications of being “Always On” • Need to be more careful about security • Hackers scan for security holes • More chance they’ll find you if you are always connected, and have the same address • Unless you really know what you’re 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 Tim Adye

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”) … Tim Adye

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. Tim Adye

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 Tim Adye