Digital signature is an attachment to an electronic message used for security purpose. It is used to verify the authenticity of the sender.
Ethernet technology is a high speed broadcast bus technology. In this type, all the station shares a single ether channel and receives every single transmitted signal.
NIC is used to connect computer to an Ethernet network.
In this technology, all the devices are arranged in a circle. A token moves around the circular network. A device waits for the token before it sends its frame. Once it receives token, it initiates transmission of its frame.
In CSDA (carrier sense multiple access), presence of any digital signal in a network is checked before transmission. Data transmission occurs only when no signal is sensed.
CD, Collision detection is responsible for monitoring carrier in order to avoid signal jam.