In IPv6, the functionalities of the TCP (Transmission Control Protocol) and UDP (User Datagram Protocol) protocols in terms of checking and handling data remain essentially the same as in IPv4, although with some adaptations to function properly in the new environment. IPv6 addressing and additional features.

We will explain how each protocol fits and works in the context of IPv6:

TCP over IPv6

TCP is a connection-oriented protocol, which provides reliable data transmission, flow control, congestion management, and retransmission mechanisms. In IPv6, TCP continues to offer these same functionalities:

1. Connection Start and Termination: TCP uses the same handshake mechanisms (such as the three-way handshake) to establish and terminate connections.
2. Flow and Congestion Control: Implements flow control by using receive windows and congestion control algorithms such as TCP Reno or TCP Cubic.
3. Error Checking: Uses checksums to ensure the integrity of transmitted data.

One notable difference is that the IPv6 header does not include a checksum field, unlike IPv4. In IPv6, the responsibility for the checksum falls entirely on upper layer protocols such as TCP and UDP. This means that the TCP checksum in IPv6 covers both the header and data of the TCP segment, and also includes parts of the IPv6 header to verify the integrity of the packet during transmission.

UDP over IPv6

UDP is a connectionless protocol, used for applications that require fast transmissions, such as video streaming or online gaming. As in IPv4, UDP in IPv6 offers:

1. Datagram Transmission: Send datagrams without establishing a prior connection.
2. Optional Integrity Check: In IPv4, UDP checksum is optional, but in IPv6 it is mandatory. This improves the reliability of applications that use UDP, ensuring that no corrupt datagrams are processed.

In IPv6, the UDP checksum is always required and covers the IPv6 pseudo-header (which includes the source and destination addresses, packet length, and other values), the UDP header, and the data. This checksum ensures that datagrams arrive intact and to the correct endpoints.

Conclusion

While the basic functionality of TCP and UDP remains the same in IPv6, the main difference is in how these protocols implement and handle checksums, adapting to the IPv6 design that seeks to improve packet processing efficiency and network security. .

The mandatory checksum in UDP and the inclusion of the pseudo-header in checksums are significant changes intended to take advantage of the structural improvements of IPv6.