Protocol spoofing
Protocol spoofing is used in data communications to improve performance in situations where an existing protocol is inadequate, for example due to long delays or high error rates.
A communications device such as a modem or router simulates ("spoofs") the remote endpoint of a connection to a locally attached host, while communicating with a compatible remote device using a more appropriate protocol.
Note: In a computer security context, spoofing refers to various forms of falsification of data. Protocol spoofing as discussed here is a legitimate technique, not an attack method.