Hello,
http://centos.bio.lmu.de/mrtg/141.84.43.23_141.84.43.22.html
This is a german mirror, offering rsync, http and ftp, all isos including DVD. The lack of traffic you can see in July was a config problem :)
so usually you have an average of about 2 MB/s which means about 16MBit bandwidth?
Since HTTP seems to be the more widely used protocol for yum, which HTTP daemon do you use? I guess not Apache httpd with all its unnecassary features for a read only httpd?
Regards Marten