The Internet has made great strides since its inception. It has grown from a relatively slow system for military communications to a robust platform for developing rich applications. Speed has been the major catalyst in that transformation; after all, it is the increase in data transfer speeds over the Internet that has allowed developers write applications that run completely in cloud and do not require code to be installed on the user's personal computer. Unfortunately, there are times when the Web is not as fast as it ought to be. There are a number things that can cause the Internet to slow down.
The most common issue that people tend to have with their routers is port forwarding. Port forwarding is the way that the router can allow communication that might otherwise be restricted to be received by a PC or group of PC's. Unfortunately, if you have not configured your router's port forwarding properly, your Internet connection will slow to a crawl, as your router tries to delegate where to send the data.
Under heavy usage, Internet service providers' systems will be forced to divide out the same bandwidth that it would under light usage to a very large amount of people. In this scenario, everyone in your immediate area that had service from you ISP would also be experiencing low bandwidth related issues. There is little that you can do about this.
The Internet is a large network that runs on the backs of thousands of servers and miles of fiber optic cables. If the servers that you use to connect to the Internet, the fiber optic cables, or telephone lines are down, then you will certainly experience low bandwidth. Again, there is little you can do about this, other than call your ISP and let them know that there is a problem in your area.
Viruses and spyware can do a lot of damage to your system. Certain types of malware use up large amounts of bandwidth, usually by downloading other malware or more copies of themselves from a remote server. Victims of these attacks will experience that they are experiencing extremely slow download and upload speeds. If this describes your situation, then it is recommended that you run a malware scan on your system on soon as possible to avoid any major system damage.