windows - What does the "Bitmap Caching" option do in the Remote Desktop Client?

This setting has always confused me:

What exactly does the Bitmap Caching option in the Windows Remote Desktop Client do? I understand that it is supposed to improve connection performance, but how? Is it really that much of a difference?

Answer

Caching bitmap means that images and other bitmap resources are locally stored on the client computer for reusing them later. This way, the remote server or PC doesn't send images twice reducing the amout of data sent and saving your bandwidth usage.

The option makes particularly sense for slow (low bandwidth) connections, less if you connect to a machine in the same local area network.

If you enable the option the Remote Desktop client caches bitmaps into a BMC file located on the client hard disk in (example for Windows XP)

C:\Documents and Settings\\Local Settings\
     Application Data\Microsoft\Terminal Server Client\Cache 

folder.

Note (interesting if your computer is part of a domain): since the cache folder is stored in a "Local Settings" folder, it won't be replicated as part of a roaming user profile.