Explain the TCP Services in the Computer Network.

Following are some of the services offered by the Transmission Control Protocol (TCP) to the processes at the application layer:

• Stream Delivery Service
• Sending and Receiving Buffers
• Bytes and Segments
• Full Duplex Service
• Connection Oriented Service
• Reliable Service

All the above mentioned TCP services are explained below in detail.

Stream Delivery Service

TCP is a stream-oriented protocol. It enables the sending process to deliver data as a stream of bytes and the receiving process to acquire data as a stream of bytes.

TCP creates a working environment so that the sending and receiving procedures are connected by an imaginary "tube" that provides seamless data flow.

Sending and Receiving Buffers

The sending and receiving processes cannot produce and receive data at the same speed. Hence, TCP needs buffers for storage to handle this speed mismatch.

There are two types of buffers used in each connection:

• Sending Buffer − Stores data waiting to be transmitted
• Receiving Buffer − Stores received data waiting to be consumed by the application

A buffer can be implemented using a circular array of 1-byte locations. The buffer has three types of locations:

• Empty Locations − Available space for new data
• Sent but Unacknowledged − Bytes kept until acknowledgment is received
• Ready to Send − Bytes waiting to be transmitted by TCP

Bytes and Segments

Buffering handles speed differences, but TCP must send data to the IP layer in packets, not as a continuous stream of bytes.

At the transport layer, TCP groups several bytes into a packet called a segment. A header is added to each segment for control purposes. The segment is then encapsulated in an IP datagram for transmission.

Segments may arrive out of order, get lost, or become corrupted during transmission. TCP handles these issues transparently to ensure reliable delivery. Each segment can carry hundreds of bytes, and segments are not necessarily of the same size.

Full-Duplex Service

TCP offers full-duplex service where data can flow in both directions simultaneously. Each TCP connection maintains both a sending buffer and receiving buffer on each end, allowing bidirectional communication.

TCP segments are sent in both directions independently, enabling efficient two-way communication between processes.

Connection-Oriented Service

TCP is a connection-oriented protocol. When a process wants to communicate with another process, the sequence of operations is:

• TCP of process-1 informs TCP of process-2 and gets approval (connection establishment)
• Both TCPs exchange data in both directions (data transfer phase)
• After completing data exchange, when buffers are empty, both TCPs destroy their buffers (connection termination)

The TCP connection is virtual, not physical. TCP segments encapsulated in IP datagrams can be sent out of order, may get lost or corrupted, and each segment may take a different path to reach the destination.

Reliable Service

TCP is a reliable transport protocol. It uses an acknowledgment mechanism to ensure safe and sound arrival of data. Features that provide reliability include:

• Acknowledgments − Receiver confirms successful data receipt
• Retransmission − Lost or corrupted segments are retransmitted
• Sequence numbers − Ensure correct ordering of data
• Flow control − Prevents overwhelming the receiver

Conclusion

TCP provides essential services including stream delivery, buffering, segmentation, full-duplex communication, connection-oriented service, and reliable data transmission. These services work together to ensure accurate and efficient data communication between applications over unreliable networks.