what if a server upload data to me in a speed less than my download speed ??

There isn't anything wrong with that. A server's Internet connection may be less than your download speed or more commonly bandwidth is throttled so that one connection doesn't take up all of the available bandwidth.

so my downloads speed =< upload speed of server

Your computer cannot download any faster than the server can upload.

it isn't necessory, Downloading speed and uploading depends on the server and band width.

Be a part of the DaniWeb community

We're a friendly, industry-focused community of developers, IT pros, digital marketers, and technology enthusiasts meeting, networking, learning, and sharing knowledge.