求 sqeeze 源仓库解释

ch_fb

squeeze 发行说明中有
“Some packages from proposed-updates may also be made available via the squeeze-updates mechanism. This path will be used for updates which many users may wish to install on their systems before the next point release is made, such as updates to virus scanners and timezone data. All packages from squeeze-updates will be included in point releases.
Note that this replaces the functionality previously provided by the volatile.debian.org archive. ”
如此说来， squeeze-updates 是包含了过去的 volatile ，那 proposed-updates 呢？我打开 ftp 看到里面依然还有 squeeze-proposed-updates 目录呀，而且东 西似乎比 squeeze-updates 要多。
其二， security 呢？我只知道以前 proposed-updates 是包含 security 的，加 了 proposed-updates 就不必加 security ，现在呢？