The idea with chunks is simply swarming downloads. When you divide the file in chunks, you can request the different chunks from different hosts and download the file simultaneously from different sources. That will speed up the transferring proccess. Dividing in chunks itslef will not help at all, it will actually decrease the downloading efficient rate. But when there are multiple sources available and the chunk size is reasonable, it will significantly increase the download transfer rates for broad band users. But without Keep-Alive and HTTP-pipelinig small chunks may have huge negative affect to the transfer rates.