Holy hell guys, is it even possible to download files from DLSite? I mean, maybe that's just me, but download speed that I'm getting is abysmal - around 100-150Kb/s if I'm lucky enough, and sometimes it drop even lower. And getting archive ~1Gb is an exercise in futility - waited for around 1 hour for download irreversibly fail at around 300Mb. And I have normal internet connection and speed, it's just when it comes to getting demos or downloading the game itself it slows down to a crawl.
That is weird. Downloading stuff is kind of DLSite's business. From what I can tell, they have a pretty respectable contract with akamai to provide content delivery, things should work, at very decent speeds.
That said - I have found specific things to be slow sometimes. Presumably, their master servers are in japan, and servers near you act as caches. For anything that was already requested by someone else near you, things will be blazingly fast.
But if you try to get something that's either very new or very old, it might not be in cache yet, getting you 100kB/s because that's now coming all the way from japan, and long bandwidth is expensive.
Try the same thing a few hours or a day later - it might be in local cache by then.
I did find that aborting those slow downloads wasn't that bad - it'd often be fast up until the point where I left off (because that section is now in local cache) and crawling speeds onwards from there.
Though I also think that resuming worked for me in the past - really, no reason for caches not to support range-requests needed for resuming.
Of course, it's entirely possible that your ISP is just throttling akamai. Which is absurd, that breaks half the internet, but that's ISPs for you...
You could also try a download manager (now there's a term I haven't heard in a long time), those might have tricks to speed things up / help with resuming.
The problem is that they might only work properly on public demo links - I think the paid-product download links use some funky cookie-based authentication that an external download manager might struggle with...
Edit: Checking again, I'm not getting akamai, so either I'm completely misremembering, or they changed their setup since I last checked it out.
At least from my end (may differ based on where you access from) I'm getting download requests sent to a cdnga server in japan. So, no happy local caches, everything is going across oceans now.
Which means download speeds might depend on how good your ISP's peering with KDDI is, or whatever they're using to get to japan.
All I can say is that the setup can totally deliver at least 7.5MB/s if everything is working properly.
Edit2: On the server I'm hitting, resuming also works just fine. Either your browser is being weird, or there's something really strange going on with your connection, where you sometimes can't reach the server at all...