The difference is that TCP is responsible for the data delivery of a packet and IP is responsible for the logical addressing. In other words, IP obtains the address and TCP guarantees delivery of data to that address.

TCP/IP is a protocol stack which contains different protocols required for the data transfer from sender to receiver.

TCP – Layer 4 protocol which ensures reliability and is connection oriented.

TCP/IP is also a layered protocol but does not use all of the OSI layers, though the layers are equivalent in operation and function (Fig. 2). The network access layer is equivalent to OSI layers 1 and 2. The Internet Protocol layer is comparable to layer 3 in the OSI model. The host-to-host layer is equivalent to OSI layer 4. These are the TCP and UDP (user datagram protocol) functions. Finally, the application layer is similar to OSI layers 5, 6, and 7 combined.

The TCP layer packages the data into packets. A header that’s added to the data includes source and destination addresses, a sequence number, an acknowledgment number, a check sum for error detection and correction, and some other information. The header is 20 octets (octet = 8 bits) grouped in 32-bit increments.

TCP/IP is because (short answer) TCP/IP have four layer but in OSI have seven layer.

TCP is the Transmission Control Protocol. It runs over IP, so the common name TCP/IP. It’s meant to provide a reliable stream of communication between two hosts. One host (the client) sends a communication request to the other host (the server); a communication channel is stablished and the two hosts start talking to each other. TCP guarantees that the messages are delivered in the same order they were originally sent. Also, TCP includes special mechanisms to deal with congestion, using special algorithms that detect packet losses and adjust transmission speed accordingly.

TCP/IP four layer which is –

1. Application layer combinations of Application layer, presentation layer and session layer.
2. Transport layer which is combinations of only transport layer.
3. Internet layer combinations of network layer.
4. Network interface layer which is combinations of Data link layer and Phsical layer .