The Digi Retoura was the most difficult. The management systems reach the routers through terminal emulation into the router's serial port or through Telnet. Using Telnet means you can manage the utility remotely. Whenever you connect to the Internet, you expose your system to hackers. This seems far-fetched, but it happens more often than anybody likes to admit.
Most routers now implement firewall technologies.
The Pipeline and Pacesetter also include spoofing filters to block hackers who generate packets with IP addresses which appear local to your network. All three routers support these. These also matter on the remote site. An important aspect to consider on the router, however, is compression. The Van Jacobson standard for compressing IP header data eliminates a lot of the overhead traffic in an IP connection.