Preupgrade is slow

[W.H. Kalpa Pathum]

hi all,

I'm trying to upgrade F12 to F13 and I'm using preupgrade-cli. Al
though my internet connection is capable to transfer around 50kB/s,
the preupgrade downloads files with around 20kB/s. Further it hangs a
long times after a file is downloaded to begin the next file
downloading. It's not packages but the files prior to that like

/boot/upgrade/vmlinuz checksum OK
/boot/upgrade/initrd.img checksum OK

and when I stop the process and restart preupgrade the whole process
starts from the very beginning downloading the files which are already
downloaded.

Why is this and how can I overcome those issues?

-- 
Best Regards,

W.H.Kalpa Pathum
http://kalpapathum.blogspot.com
http://thiraya.wordpress.com