Welcome back. As you've seen, computer networking can be an incredibly complicated business. There are so many layers, protocols and devices at play. And sometimes this means that things just don't work properly. No surprise there. Many of the protocols and devices we've covered have built-in functionalities to help protect against some of these issues. These functionalities are known as error detection and error recovery. Error-detection, is the ability for a protocol or program to determine that something went wrong. Error-recovery is the ability for a protocol or program to attempt to fix it. For example, you might remember that cyclical redundancy checks are used by multiple layers to make sure that the correct data was received by the receiving end. If a CRC value doesn't match the data payload, the data is discarded. At that point, the transport layer will decide if the data needs to be reset. But, even with all of these safeguards in place, errors still pop up. Misconfigurations occur, hardware breaks down and system incompatibilities come to light. In this module, you'll learn about the most common techniques and tools you use as an IT support specialist when troubleshooting network issues. By the end of this module, you'll be able to detect and fix a lot of the common network connectivity problems, by using tools available on the three most common operating systems: Microsoft Windows, Mac OS and Linux. And finally, at the end of this module, we'll cover some concepts that are super important to the future of networking: the cloud and IPv 6.