A gateway operates at the upper levels of the OSI model and translates information between two completely different network architectures or data formats.

Bit rate is the number of bits transmitted during one second whereas baud rate refers to the number of signal units per second that are required to represent those bits. Baud rate= bitrate/N where N is no of bits represented by each signal shift.

TCP windowing concept is primarily used to avoid congestion in the traffic. It controls the amount of unacknowledged data. A sender can send before it gets an acknowledgement back from the receiver that it has received it.

Public key encryption use public and private key for encryptioin and decryption. In this mechanism, public key is used to encrypt messages and only the corresponding private key can be used to decrypt them. To encrypt a message, a sender has to know reciepients public key.

Data encryption ensures data safety and very important for confidential or critical data. It protect data from being read, altered or forged while transmission.