I’ve tried searching for mentions, but haven’t located any, so excuse me if this has been covered elsewhere…
One of the massive advantages of distribution of data across multiple nodes is the speed gains possible by parallelisation of transfers. This is how DrFTPD became a dominant choice for FTP daemons. How can a single threaded option, limited by the speed of a given node, possibly compete against one that took 6, 8, 10+ transfers at once? It was a clear winner in the war of fastest transfers.
Aria2 has long been a favourite transfer client, also because of this ability to handle, well, multi-parts from varying sites, simultaneously.
Given the internet is littered with machines having varying upload speeds, and limited by trans-Atlantic hops, amongst other limitations, parallel transfers are a must, in some cases.
Queuing, buffering, and other considerations obviously play a part, but to what extent is parallelisation implemented, planned, or at least catered for in some respects?