Dear Weber,
In a nutshell both are possible. Connecting A to B, B to C and C to BSC is called a daisy chain config. And connecting A,B and C to BSC by separate links is called star config. The former has a drawback, if the first site connected to the BSC goes down, so does the remaining. Advantage, it is possible for A,B and C to share the same 2MB link and saving 2MB ports at the BSC. Thus A,B and C will require 1 BSC port. On the contrary Star config will eat up more 2MB ports at the BSC end. Thus A,B and C will require 3 ports at the BSC. There is much much more to it. I hope this helps.