What three requirements are defined by the protocols used in network communcations to allow message transmission across a network? (Choose three.)

Protocols in network communications are designed to ensure proper and efficient transmission of data across a network. The following three are typical requirements defined by these protocols:

1. Message encoding: This is the process of converting information into another form or code. In network communications, protocols define how a message is formatted or converted into signals that are transmitted over the media. This can include encoding schemes such as binary, analog, or digital encoding, depending on the medium and technology in use.
2. Delivery options: Protocols must define how messages are treated during the delivery process. This includes whether the communication is unicast, multicast, or broadcast, as well as handling aspects like message prioritization, quality of service (QoS), and routing.
3. Message size: Protocols often define a maximum message size, which can be dictated by the Maximum Transmission Unit (MTU). The MTU is the largest size of a packet or frame that can be sent in a packet- or frame-based network such as the Internet. If a message exceeds the MTU, it must be divided into smaller packets or frames, a process known as fragmentation.

The other options provided, such as end-device installation, media selection, and connector specifications, are more related to the physical setup and hardware requirements of the network rather than the protocols used for network communications. Protocols do dictate certain physical layer specifications but those are more about the electrical, optical, or mechanical aspects, and less about the actual selection and installation of media and devices.