Data Link Protocols Asynchronous Protocols XMODEM frame ...

HDLC: Use of P/F fieldHDLC: Use of P/F field43 of 5344 of 53HDLC: S-FrameAcknowledgementHDLC: S-FramePositive Acknowledgement• RR• Receiver sends “Positive Ack” (no data to send)• N(R) = seq of next frame• RNR• Receiver sends “Positive Ack”• N(R) = seq of next frame• Receiver tells sender that sender cannot send anyframe until ‘RR’ frame is received45 of 5346 of 53HDLC: S-FrameNegative AcknowledgementHDLC: U-Frame control field• Reject (REJ)• Go-back-n ARQ• N(R) = # of damage frame (and follow)• Selective-Reject (SREJ)• N(R) = # of damage frameFor session management and control information47 of 5348 of 538