A Comparison of
Access Techniques
href="http:// /JVXSL.asp?x=1&mode=section&sortKey=insertDate&sortOrder=desc&view=&xmlid=0-201-77423-2/ch14lev1sec5&open=true&title=New%20This%20Week&catid=&s=1&b=1&f=1&t=1&c=1&u=1#ch14table01#ch14table01"> 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.