There is no single body that manages the internet. There are so many entities involved in the provision of the internet and the management of services it provides. You can not call a single entity as managers of the internet however there are a lot of companies and software that provide management for the internet connection you have.
The services they provide can help you maintain a healthy connection with the outer world by configuration, monitoring, and management. They are also responsible for the security and accounting of your internet.
Some of the functionalities this software perform are
Network management is a way of administrating, monitoring, and managing a network using a network management system by constantly collecting and analyzing data and pushing out configuration changes for performance improvement.
The internet management software manages the configuration of the internet in a desired and consistent state and then building and maintaining those states. This will free you from the confusion of managing individual networks and servers, etc.
Internet management tools or software can help you keep all your equipment at the proper configurations, network settings, desired addresses, and will help you maintain all other necessities for equipment while managing a network.
If a fault occurs in your network configuration or if you face any other technical issue regarding your internet, the internet management tool will help you recognize it, as well as help you solve the fault that occurred.
Internet management software can monitor the performance of your internet and suggest different ways through which you can improve the performance of your overall network including the equipment you are using within the networks
Internet management software can also manage the security of your devices by detecting any malware or virus and informing you about any risky files in your system. It can also detect intrusions from a malicious user and can suggest improvements in firewall and other security protocols manage any threats.
Internet management tools also log all the data that went through your network, at which rate it got transferred, the source and destination locations of data, and other important information that can help you improve your network in the longer run.
There is so much more an internet management tool can do for you. The only thing you have to do is to choose the right tool for your network.