With selective repeat, the sender sends a number of frames specified by a window size even without the need to wait for individual ACK from the receiver as in Go-Back-N ARQ.
If the receiving window is larger than half the maximum sequence number, some, possibly even all, of the packets that are present after timeouts are duplicates that are not recognized as such.
Alternately selective retransmission may be employed in conjunction with the basic ARQ mechanism where the message is first subdivided into sub-blocks (typically of fixed length) in a process called packet segmentation.
The ITU-T G.hn standard, which provides a way to create a high-speed (up to 1 Gigabit/s) Local area network using existing home wiring (power lines, phone lines and coaxial cables), uses Selective Repeat ARQ to ensure reliable transmission over noisy media.
G.hn employs packet segmentation to sub-divide messages into smaller units, to increase the probability that each one is received correctly.
The STANAG 5066 Profile for High Frequency (HF) Radio Data Communication uses selective repeat ARQ, with a maximum window size of 128 protocol-data units (PDUs).