GESP is Gigabit Ethernet Surge Protector that can be used to protect the network from lightning or surge damages.
Here’s what a typical use-case would be like. You have a mast with some antennas. And some switches on the ground. Put the GESP surge protectors on each end. They come sealed inside a new and improved IP67 weatherproof enclosure. Your antennas are now safe during a lightning storm.
Don’t forget about the grounding wire! Secure it to the rackmount, mast, or any other structure that is connected to the ground. For maximum protection, you should use a surge protector on both ends of long cables.