[CentOS] How CentOS Mirrors Work

Can someone tell me how the mirroring process works? Like, is any 
portion of bandwidth useful, or should something like a full T-1 be 
considered a minimum useful addition? I guess I'm wondering if when I'm 
doing updates, when one RPM is coming in, if it is coming in from one 
mirror server at a time or if it is a cumulative situation? So, like 
would an additional 50k capped connection would be helpful or just be a 
slow update connection?

Best,
John Hinton