<html><head><meta http-equiv="content-type" content="text/html; charset=utf-8"></head><body style="overflow-wrap: break-word; -webkit-nbsp-mode: space; line-break: after-white-space;">Hello Ana,<div><br></div><div>I took a very quick look in the traceroute code, see here:</div><div><div style="display: block;"><div style="-webkit-user-select: all; -webkit-user-drag: element; display: inline-block;" class="apple-rich-link" draggable="true" role="link" data-url="https://github.com/RIPE-NCC/ripe-atlas-probe-measurements/blob/7c03fba082e93b7a1f0f14cc3769bb31e83909e3/eperd/traceroute.c"><a style="border-radius:10px;font-family:-apple-system, Helvetica, Arial, sans-serif;display:block;-webkit-user-select:none;width:300px;user-select:none;-webkit-user-modify:read-only;user-modify:read-only;overflow:hidden;text-decoration:none;" class="lp-rich-link" rel="nofollow" href="https://github.com/RIPE-NCC/ripe-atlas-probe-measurements/blob/7c03fba082e93b7a1f0f14cc3769bb31e83909e3/eperd/traceroute.c" dir="ltr" role="button" draggable="false" width="300"><table style="table-layout:fixed;border-collapse:collapse;width:300px;background-color:#E5E6E9;font-family:-apple-system, Helvetica, Arial, sans-serif;" class="lp-rich-link-emailBaseTable" cellpadding="0" cellspacing="0" border="0" width="300"><tbody><tr><td vertical-align="center" align="center"><img style="width:300px;filter:brightness(0.97);height:150px;" width="300" height="150" draggable="false" class="lp-rich-link-mediaImage" alt="ripe-atlas-probe-measurements.png" src="cid:47E42341-447B-4A96-B0C3-D3FD918BFCD3"></td></tr><tr><td vertical-align="center"><table bgcolor="#E5E6E9" cellpadding="0" cellspacing="0" width="300" style="font-family:-apple-system, Helvetica, Arial, sans-serif;table-layout:fixed;background-color:rgba(229, 230, 233, 1);" class="lp-rich-link-captionBar"><tbody><tr><td style="padding:8px 0px 8px 0px;" class="lp-rich-link-captionBar-textStackItem"><div style="max-width:100%;margin:0px 16px 0px 16px;overflow:hidden;" class="lp-rich-link-captionBar-textStack"><div style="word-wrap:break-word;font-weight:500;font-size:12px;overflow:hidden;text-overflow:ellipsis;text-align:left;" class="lp-rich-link-captionBar-textStack-topCaption-leading"><a rel="nofollow" href="https://github.com/RIPE-NCC/ripe-atlas-probe-measurements/blob/7c03fba082e93b7a1f0f14cc3769bb31e83909e3/eperd/traceroute.c" style="text-decoration: none" draggable="false"><font color="#272727" style="color: rgba(0, 0, 0, 0.847059);">ripe-atlas-probe-measurements/traceroute.c at 7c03fba082e93b7a1f0f14cc3769bb31e83909e3 · RIPE-NCC/ripe-atlas-probe-measurements</font></a></div><div style="word-wrap:break-word;font-weight:400;font-size:11px;overflow:hidden;text-overflow:ellipsis;text-align:left;" class="lp-rich-link-captionBar-textStack-bottomCaption-leading"><a rel="nofollow" href="https://github.com/RIPE-NCC/ripe-atlas-probe-measurements/blob/7c03fba082e93b7a1f0f14cc3769bb31e83909e3/eperd/traceroute.c" style="text-decoration: none" draggable="false"><font color="#808080" style="color: rgba(0, 0, 0, 0.498039);">github.com</font></a></div></div></td></tr></tbody></table></td></tr></tbody></table></a></div></div></div><div><br></div><div>It seems that a sequence number in the traceroute packet is used. If this sequence number is received back it’s marked as ‘response received’. If another response is received within a certain timeframe, it’s tagged as a duplicate. Otherwise its a late packet.</div><div><br></div><div>Hope it helps.</div><div><br></div><div>Cheers,</div><div><br></div><div>Michel</div><div><div><br><blockquote type="cite"><div>On 20 Jan 2023, at 11:38, Ana Custura <ana@erg.abdn.ac.uk> wrote:</div><br class="Apple-interchange-newline"><div><div>Hi everyone,<br><br>Just a question on how Atlas detects duplicate ('dup') packets in a traceroute.<br><br>Is the 'dup' field added to a result when two received packets are exactly the same, regardless of whether they were received for a different initial TTL? <br><br>Or are any packets that were unexpectedly received for a specific TTL marked as duplicates (e.g. if you receive 6 replies from 2 different IP addresses to the 3 initial packets sent with TTL 1, will 3 of these replies be marked as duplicates)?<br><br>Thanks for your help!<br><br>Regards,<br>Ana<br>-- <br>ripe-atlas mailing list<br>ripe-atlas@ripe.net<br>https://lists.ripe.net/mailman/listinfo/ripe-atlas<br></div></div></blockquote></div><br></div></body></html>