Network congestion and typical slow Livna repos.
When it starts to cache it, when you notice the lag, hit ctrl+c. This makes it skip that particular mirror immediately and moves on to the next available one. However, don't hit it constant or keep it depressed, it will abort the entire transaction. Skip mirror by mirror.
Also it will help if you install the package called 'yum-fastest-mirror' which assigns the closest mirror to you, typically this should be the IITM mirror in Chennai, http://ftp.iitm.ac.in
And finally, install 'yumex' which is a graphical frontend to yum. This is much faster than the typical yum from the command line.