First of all let me discuss the matter of what you are saying.
2.1mbps on a what type of connection? If you are on ADSL or DSL with any sort of contention ratio this could mean you are just in a busy period. Download speed of 236kbps. How are you measuring
MBps and Mbps are two different things. Different by a factor of 8. If you are using 2 separate ways to work this out you may be happen to be getting the speed read wrong if you are you are downloading at 1.888Megabits per second when you read it.
ADSL speeds are the maximum speeds you can expect to get, however like 56k dial up you rarely get it. I have never gotten the full speed on either of these services.
If you can clarify how you are getting these figures we can probably help more. Also try a speed test over at click here