I am not certain about Debian's installer, but the Fedora installer has an option for using NFS to retrieve the installation data.
To make this work, you need to have a Linux (or other Un*x) machine with a DVD reader on it, and a network attachment between it and the machine you are trying to install on. In addition, the server (with the DVD) must be set up to export the filesystem on the DVD.
This can be accomplished by putting a line in the file /etc/exports that begins with /mnt/dvd (assuming that is where the DVD gets mounted on your system), and then giving the command
Once this is set up, you should be able to put in the necessary details for NFS mounting the DVD during your install on the target machine.