Functions of Protocols:-

1) Segmentation & Reassembly:-

• Segmentation is division of a large size of data into small data units for easy handling and avoiding unnecessary Re-transmission.
• If error occurs only the part of the data is to be Re-transmitted not the entire data. Hence, the network is not overloaded so, efficiency increases.
• On the Receiver side the data is to be reassembled in ordered fashion.

2) Encapsulation:-

• Encapsulation is the process of attaching control information in the form of header and trailer.
• The header includes the control information related to delivery like source address, destination address, Sequence number for reordering of data acknowledgement number for confirmed delivery of data, Priority for specifying the type of data etc.
• These information are in header.
• The trailer which includes cyclic redundancy check are related to error.

3) Connection Control:-

• Connection control is combination of error control and flow control.

4) Error Control:-

• Error control includes the error detection by checking the CRC bits or Parity bits.
• If CRC is fine then acknowledgement is send otherwise the Receiver will remain silent. Hence, the sender will Re-transmit the data to provide error correction.

5) Flow Control:-

• It is provided with the help of acknowledgement number which gives the confirmation of delivery of the data and let the sender know that receiver is ready to accept and process further data.

6) Ordered delivery:-

• With the help of sequence number if the data is received in out of order fashion then it can be recorded.
• Other functions of protocols are Addressing, Multiplexing and Transmission Services.