Answer: The cable modem that is supposed to be connected to the modem should be coaxial cable .The coaxial cable is attached with the wide area network's (WAN) port for providing the internet service to the customer and also other customers/neighbors got engaged with with the TV cable infrastructure through sharing.
Due to several connections that is made by the neighbors in the evening time when they return from work with the WAN port, degrades the speed of the internet service.These people are using the service at the same time thus ,slow's down the network service.