The Internet layer in the TCP/IP reference model is responsible for transferring data between the source and destination computers. Routing and data transmission are done by Internet Protocol and error handling is implemented by ICMP. IP provides a connectionless and unreliable data transmission system. IP also specifies the format in which data needs to be transferred, which is also called an IP datagram. The IP datagram, in turn, is encapsulated in a frame and transmitted over the network. The fields in an IP datagram that are used in the transmission of data are Version, Header Length, Types of Service, Total Length, Time to Live, Protocol, Header Checksum, Source Address, and Destination Address. The fields that are used for fragmentation are Flags, Identification, and Fragmentation Offset.