For roughly every 10mbps of download, you need 1mbps of upload, just for your ip/tcp/http headers. If using p2p protocols such as bittorrent it can be slightly higher. So when ISPs give you a slow upload rate they are actually sneakily breaking your download rate. For Example, say you get a 2048kbps upload on a 40mbps line. You will be capped to around 20mbps for sustained downloads, and only get higher for burstable downloads(browsing) where your control data is limited. This has also been happening a lot on slower DSL packages like the 10mbps where often your upload is set at 640kbps or 512kbps. Its an artificial way to cap your download speed without you ever realizing it ! Now sure telkom can say .. but your line (copper quality) is so poor that we must slow it down or it drops, but is that always the case ? Or do they just arbitarily decrease your upload sync speed when you arnt looking ? On my line this seems to happen quite often and if I request a "DSLAM Port Reset" from my ISP then it goes back to its proper speed of 1024kbps upload and 10240kbps download.
https://disqus.com/home/discussion/mybroadband/why_vdsl_upload_speeds_are_so_slow_57/