<P> The SSL / TLS library operates above the transport layer (uses TCP) but below application protocols . Again, there was no intention, on the part of the designers of these protocols, to comply with OSI architecture . </P> <P> The link is treated as a black box . The IETF explicitly does not intend to discuss transmission systems, which is a less academic but practical alternative to the OSI model . </P> <P> The following is a description of each layer in the TCP / IP networking model starting from the lowest level . </P> <P> The link layer has the networking scope of the local network connection to which a host is attached . This regime is called the link in TCP / IP literature . It is the lowest component layer of the Internet protocols, as TCP / IP is designed to be hardware independent . As a result, TCP / IP may be implemented on top of virtually any hardware networking technology . </P>

Software ports are specific to which layer in the tcp/ip model