A Comparison of Access Techniques | Advanced Linux Networking

Table 14.1 summarizes some important characteristics of the various access techniques discussed in this chapter. Note that some of these assessments depend upon the nature of the configuration or specific software products used. For instance, login security for a text-mode VNC login depends upon the text-mode tool used; if you use SSH to make the initial connection, your login security should be excellent , but if you use an unencrypted login protocol, that initial connection may be compromised, although if you use a different password for the VNC connection, its password will remain secure.

Table 14.1. Remote GUI Access Comparisons

Characteristic	Unencrypted Text-Mode X Login	SSH Text-Mode X Login	XDMCP X Login	Text-Mode VNC Login	VNC with XDMCP
Login security	Poor	Excellent	Poor	Poor to Excellent	Poor
Session security	Poor	Excellent	Poor	Poor	Poor
Potential for problems with firewalls	High	Low	High	Low	Low
Session persistence (log out, then back in to the same session)	Low	Low	Low	High	Low
Speed	High	Moderate	High	Low to Moderate	Low to Moderate
Potential for application problems	Low to Moderate	Low to Moderate	Low to Moderate	Moderate	Moderate

Which GUI access technique should you use? That's a question that has no simple answer. X is an excellent tool for connections between Linux or UNIX systems, particularly within a single subnet. Such systems almost invariably have all the necessary software installed already, so using X is fairly straightforward, and you'll get good speed. If you want to access Linux systems from Windows or MacOS, X is also a good choice, but you'll need to locate an X server for the non-Linux systems, and these can be costly. VNC is a less expensive choice for such environments, and it has the advantage of working in the opposite direction (you can control a Windows or MacOS system from Linux). VNC may also be worth considering for remote access when the system at which the user sits is protected by a firewall, because a firewall is more likely to block a return connection to the local X server than an outgoing VNC connection.