E xplicit Retransmit Request Higher channel utilization than the implicit retransmit request. On receiving a NAK, P retransmits I-frame. ACKs and NAKs are never in error. C ontinuous RQ Higher link utilization. Larger buffer storage requirements.
P sends frames continuously without waiting for ACKs.
S transmits an ACK for each correctly received I-frame. P maintains a retransmission list. S maintains a receive list. A corrupted frame is detected when a frame with the next sequence number is received. R etransmission List P maintains a list of frames sent and a copy of each frame.