I'm tired of downloading 300mb updates. Windows has done delta updating since XP. It's just silly to download the whole thing if just a few bits of the package change.
There is nothing on upgrading via deltas. So, no, as of today there seem to be no plans.
Incremental updates have been introduced to apt around the time of the Dapper release (apt 0.6.44). The ubuntu developer community rejected using them because of incompatibilities with their infrastructure.
There is no need to submit it to revu. We are aware of the incremental update feature in apt. The apt--pdiff (1) branch (that the version in debian uses) is not merged for ubuntu (yet) because:
we are late in the release cycle (obviously :)
it needs archive support to generate diff files and a diffIndex
it only works on indexfiles, not packages
its not entirely clear if it is the right solution for ubuntu
–– Michael Vogt on 25th of May 2006
Here is a list of everything that's happening, and going to happen, in 11.04 (excluding what is not publicly tracked).
There is a blueprint for it, and I would love to be able to make it happen for all sorts of reasons, but we haven't been able to find the time to do it - it doesn't help that it requires a significant chunk of time from the Launchpad archive infrastructure team, which has been entirely swamped. It's still very much on our back-burner list for whenever we do find the time, though.
One likely issue is that the more you compress packages, the harder it is to sync them. This is a fairly fundamental property of good compression algorithms. It may be that even once we implement this there'll be some packages that will sync little better than the current situation.
.deb files are the de-facto method of installing and updating.
The method you mention is called delta updates and has been rejected as a method for several reasons, one of them being that calculating what to download takes up too much time (more mentioned in the link in the comments).
Apt-fast is a script that can "drastically improve APT download speed" by using command line download accelerators such as Axel or Aria2 with multiple connections per package.
sudo add-apt-repository ppa:apt-fast/stable sudo apt-get update sudo apt-get install apt-fast
It works the same as
apt-get but you use (2 examples):
sudo apt-fast install PACKAGE sudo apt-fast upgrade
apt-fast can also stop and resume downloads and download a package into a directory with
apt-fast download PACKAGE.
Delta-RPM was touted as the next killer package management feature, but it was less than fabulous mainly because of the calculations required. True if you are on a highly restricted bandwidth connection, it will save your time, but if all you want to do to save time consider using apt-fast a faster front-end to dpkg.