https://devzone.nordicsemi.com/f/nordic-q-a/36874/ble-mesh-seqauthIn the Lower transport layer, segmentation will be carried out. The concept of a place is not very clear. Can you help me? SeqAuth = IV Index + first segment SEQ = 56bit, SeqZero is the least significant 13bits of the SeqAuth. When SEQ = 0x647262en-USTelligent Community 13Thu, 09 Aug 2018 10:12:51 GMThttps://devzone.nordicsemi.com/thread/143528?ContentTypeID=1Thu, 09 Aug 2018 10:12:51 GMT137ad170-7792-4731-bb38-c0d22fbe4515:4b0c0148-98fa-4c5b-850a-eacc6912cbccSusheel Nuguru<p>sorry for the late reply,</p> <p>Isn&#39;t this the function that calculates the sequence number.&nbsp;</p> <p><pre class="ui-code" data-mode="text">static uint32_t seqauth_sequence_number_get(uint32_t seqnum, uint16_t seqzero) { if ((seqnum &amp; TRANSPORT_SAR_SEQZERO_MASK) &lt; seqzero) { return ((seqnum - ((seqnum &amp; TRANSPORT_SAR_SEQZERO_MASK) - seqzero) - (TRANSPORT_SAR_SEQZERO_MASK + 1))); } else { return ((seqnum - ((seqnum &amp; TRANSPORT_SAR_SEQZERO_MASK) - seqzero))); } }</pre></p> <p>I am not sure of the internals of&nbsp;segmentation</p><div style="clear:both;"></div>