TCP/IP （） layer protocols provide services to the application （） running on a computer. The application layer does not define the application itself, but rather it defines （） that applications need—like the ability to transfer a file in the case of HTTP. In short, the application layer provides an （） between software running on a computer and the network itself. The TCP/IP application layer includes a relatively large number of protocols, with HTTP being only one of those. The TCP/IP （） layer consists of two main protocol options—the Transmission Control Protocol (TCP) and the User Datagram Protocol (UDP).

TCP/IP （） layer protocols provide services.

A．application

B．transport

C．link

D．network

柔性基层