Presto: A project to add delta rpm support into yum for Fedora users
https://hosted.fedoraproject.org/projects/presto/wiki/WikiStart

Installation:
=============
1- Install yum-presto on your system (yum -y install yum-presto) 
2- Now install an old rpm from updates or extras using rpm, then try updating
   it using yum. The plugin should kick in, try to download the drpm,
   reconstruct the full rpm, and yum should install that.

Notes:
======
Presto will read the deltaurl from two possible locations:
1. The repository's .repo file ("deltaurl = http://repository.com")
2. Appended to /etc/yum/pluginconf.d/presto.conf in the form:
   [repository]
   deltaurl = http://repository.com

Presto.conf has the following options in [main]:
keepdeltas=1               Always keep deltas in cache no matter what keepcache
                           is set to.
neverkeepdeltas=1          Always remove deltas after creating full rpms.
exitondownloadfailure=0|1  If there is a problem downloading the deltarpm, exit
                           rather than trying to download the full rpm.
Note: If you specify neither keepdeltas nor neverkeepdeltas, presto will follow
      the keepcache option in yum.conf.