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.
They tend to be used only by companies whose business is built around the Internet or who need to transfer massive amounts of data. An ISDN connection's speed ranges from 64 to 128 Kbps. Disadvantages ISDN has been around the longest, but just isn't the best option anymore. It can be a hassle to install and troubleshoot. It also isn't a constant line, and you connect when you want to.