Which is best: T-1 or cable modem?

* Help Desk columnist Ron Nutter discusses the pros and cons of T-1 vs. cable for a K-12 school's Internet access

Nutter discusses the pros and cons of T-1 vs. cable for a K-12 school's Internet access

I need to provision Internet access for a K-12 school. The usage is primarily e-mail and Web surfing, so download speed is more important than upload speed. Our local cable company is willing to donate a cable modem connection, which in my area is delivering about 4M bit/sec down and 500K bit/sec up. My personal experience is that they have been pretty stable, but everybody is telling me to go for a T-1 - which would be lots more money and provide slower download speeds. Any thoughts?

- Via the Internet

Cost and line speed are definitely two things that need to be considered with when it comes to any potential Internet connection. Let's look at each of the connections you're considering.:

A conventional T-1 will require some type of DSU/CSU (a special type of interface that connects the T-1 from the telco demark to the serial port on your router). You can use an internal or external DSU/CSU. Internals mean one less thing to plug in and fewer cables to worry about. Externals can be cheaper, but also have another advantage. In the event you experience a voltage or nearby lightning strike to the incoming copper carrying your T-1 service, the external DSU/CSU has the potential for acting like a fuse and possibly preventing damage to the router. With an internal DSU/CSU, the potential exists that the voltage surge could jump right from the DSU/CSU into the router and damage it. In the years I have been installing T-1s, I have not had a situation in which the external DSU/CSU that took damage passed the damage onto the router. As with anything, others may have not had this type of luck. In addition to the cost of the DSU/CSU, you will also have to factor in the cost of a router and a firewall. It is possible to combine the functionality of the router and firewall into one box. With a T-1, you will have close to 1.544M bit/sec in speed up and down, assuming your ISP configures the line for that.

With a cable modem, things may be a little simpler. Most ISP-provided cable modems have a built-in Ethernet jack. This can go straight to a firewall appliance to which the remainder of your network connects on the private side. Since the local cable company is donating the cable connection (and I will assume for the purposes of this discussion the cable modem, as well), all you need to look for is a good hardware firewall appliance. In your case, I'm thinking more about an appliance than a software-based firewall (such as several open-source Linux firewall distros that boot off of a CD) to get you something you can get without relying on an Internet listserv. Since the need for the line is more internal (i.e., Web surfing and e-mail) the cable modem option might best in terms of simplicity and associated hardware costs.

Something else to consider once you have things up and running is a caching appliance or proxy cache server. Where this will help you in that repeated requests for the same information will be served up locally, keeping your Internet connection free for other requests in which the information has to be retrieved. Another question to ask the T-1 and cable Internet providers is how oversubscribed their service is. Let me try to explain this another way - when you purchase a T-1 to the Internet, your provider runs a connection from your location to their network operations center where Internet requests are combined to the connection used by the ISP. Since you probably won't use your T-1 connection at full capacity, the ISP potentially can sell the same service to other customers, so you may end up competing with 10, 15, 20+ other customers for the same bandwidth. Some ISPs oversubscribe less, others more. Nonetheless this is a fair question to ask when you are evaluating different Internet connection options.

If you will be having some type of Web site presence where people will visit, ask each potential ISP what they will charge for a static IP address so you can more easily offer this service. Determine which other servers may need a public IP address and see what the additional charges are for additional static public IP addresses. Most ISPs offer some type of Web site offering you can host on one of their servers, keeping your Internet connection free to handle the requests coming from your network. I have hardly scratched the surface on what you need to think about with a new Internet connection but this should get you started on your journey.

Learn more about this topic

Join the Network World communities on Facebook and LinkedIn to comment on topics that are top of mind.

Copyright © 2005 IDG Communications, Inc.

IT Salary Survey 2021: The results are in