|  |  | Summary
The TCP/IP protocol stack maps closely to the lower layers of the OSI reference model and has the following components: Protocols to support file transfer, e-mail, remote login, and other applications Reliable and unreliable transports Connectionless datagram delivery at the network layer Application protocols exist for file transfer, e-mail, and remote login. Network management is also supported at the application layer. The transport layer performs two functions: Flow control, which is provided by sliding windows Reliability, which is provided by sequence numbers and acknowledgments The TCP/IP Internet layer corresponds to the OSI network layer. ICMP provides control and message functions at the network layer. ICMP is implemented by all TCP/IP hosts. ARP is used to resolve or map a known IP address to a MAC sublayer address to allow communication on a multiaccess medium such as Ethernet. RARP relies on the presence of a RARP server with a table entry or other means to respond to RARP requests.