If you host your sites on a dedicated hosting machine, you would expect that they'll perform ultra fast and that the access speed to them will depend only on the Internet connection of the visitors. Having said that, this won't be the case in case the hosting machine has poor network connectivity or relies on a network card, which just cannot deal with high volume of website traffic. If this is the situation, it'll take a long time for your websites to load if lots of people open them simultaneously or visitors could see error messages. Consequently you might lose website visitors as most likely many people will not return to your site if they have experienced problems or slow loading speeds. That's why you need to pay attention to the network components of any new server that you buy and not just to the main hardware which includes CPU, Random access memory or hard drive.