Is a process-to-process protocol that adds only port addresses checksum error control and length information to the data from the upper layer?

Yes, the description refers to the User Datagram Protocol (UDP). UDP is a process-to-process protocol that adds port addresses, checksum error control, and length information to the data it receives from the upper layer. Unlike TCP, UDP is connectionless and does not guarantee delivery or order, making it suitable for applications where speed is essential, and occasional data loss is acceptable.