Wow, welcome to LQ -- and, totally not enough information there to make any sort of stab at all, as to what the problem might be.
What sort of machine is it you are using? Is it a desktop machine (in which case I'll move your thread to a better location), or is this actually a server-related question?
Make & model if it's a laptop. What type of network card is it (make & model please) and which driver is it using, and is it a USB or PCI device or what?
Which version of Linux does this pertain to? And, what kernel version is it running?
What's the environment surrounding the problem? I.e. are you sitting home trying to browse the internet, or is this a situation with a file server, or an online game or a game server, or maybe this is a firewall machine?
Please, fill us in
as we need
details in order to help.
Sasha