<![CDATA[DLMS/COSEM HDLC LLC Sublayer & Information Frame (I-Frame) Sliding Window Flow Control]]>

<![CDATA[DLMS/COSEM HDLC LLC Sublayer & Information Frame (I-Frame) Sliding Window Flow Control]]>High-Throughput HDLC Communication via Information Frames

For bulk data transfer over serial links, HDLC Information Frames (I-Frames) enable continuous bidirectional data transmission using sliding-window flow control.

I-Frame Control Field Format

Bit 0: 0 (Identifies I-Frame)
Bits 1-3: N(S) - Send Sequence Number (0 to 7)
Bit 4: Poll/Final (P/F) bit
Bits 5-7: N(R) - Receive Sequence Number (0 to 7)

When window_size_transmit > 1 is negotiated in SNRM/UA, the client can transmit multiple I-frames consecutively without waiting for individual acknowledgments, drastically improving profile read throughput.

]]>https://dlms.sharur.org/topic/25/dlms-cosem-hdlc-llc-sublayer-information-frame-i-frame-sliding-window-flow-controlRSS for NodeFri, 16 Oct 2026 19:54:00 GMTSat, 22 Aug 2026 12:33:43 GMT60<![CDATA[Reply to DLMS/COSEM HDLC LLC Sublayer & Information Frame (I-Frame) Sliding Window Flow Control on Sat, 22 Aug 2026 12:33:45 GMT]]>If an I-frame is received with an out-of-order sequence number $N(S)$, the receiver responds with a Reject (REJ) supervisory frame (Control: 0x09), instructing the transmitter to retransmit from frame $N(R)$.

]]>https://dlms.sharur.org/post/48https://dlms.sharur.org/post/48Sat, 22 Aug 2026 12:33:45 GMT