socket minimum recieve

[C# Programming]

Hi

when I send 1000 byte with socket.send , I always recieve 1000 byte with socket.recieve.
I know it shouldn't be true for general but because 1000 bytes is a small amount can we be sure that it will not fragmented?

I tested it in visual studio and until 8KB every amount I sent, I got exactly the same amount and after that it didn't;

if enough data are provided is there a minimum amount on socket.available. for example because of packet size. I have heard that minimum packet size is 64, and default MTU(maximum transmit unit) in XP is 1500 bytes.

I use TCP and ethernet and actually the answer is very critical to me.

Thanks