From the bottom
up, these layers are:
Network Transport
Enables the other layers to communicate. This layer almost always consists of
TCP/IP plus a faster connection scheme for local clients (Section 1.14), but
many older or proprietary network transports can be used, including IPX/SPX
and DecNET.
X Window Server
Consists of the software that manages the display (which normally consists of a
keyboard, video screen, and mouse) and runs on the computer connected to the
display hardware. All of the layers above the X server are considered clients of
that server and may be located anywhere on the local network, or even over the
Internet.
Figure 1-1. The layers of an X-based GUI
Application Clients - User Productivity
OpenOffice.org, Firefox, Gimp
Desktop Environment - Application and
File Management
Gnome/KDE panels, desktop icon managers
Window and Compositing Manager -
Placement and Controls Of Windows
Compiz, Metacity, kwin
Session Manager
gnome-session, ksmserver
Display Manager - Local X Server Startup
and User Authentication
gdm, kdm, xdm
X Window Server - Display Hardware Management
Xorg
Network Transports - Client -Server Connections
TCP/IP, Unix domain sockets
Toolkits
GTK, Qt, Moif, Xaw
1.
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