Also, DSL is a dedicated line, like a cable modem. You have instant access to the web. And not only that, even if it is available, not all offices are equipped to handle this type of telecom connection. If you're considering DSL, be sure to check that your building can handle it. Startup costs can be quite high.
Customer service has the potential to be tricky as well.
Finally, be aware that DSL is particularly vulnerable to hacking. With any dedicated access, it's recommended that you invest in a firewall to protect your system. Advantages Unlike ISDN, a T-1 line is a dedicated connection, meaning that it is permanently connected to the Internet. Plus, it's super-fast. Disadvantages Leased lines are pricey.