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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D">A link between 2 nodes (routers, hosts, etc.) in CORE is facilitated by a linux bridge. So, if you have 2 routers directly connected to each other, CORE creates
that by connecting each CORE node (i.e. via kernel virtualization) to the linux bridge. If you have 3 nodes connected in a string (n1 – n2 – n3), nodes n1 and n2 are connected by one linux bridge and nodes n2 and n3 connected by another linux bridge. You
can see this by looking at the output of brctl when an emulation is running. <o:p>
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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D">I would expect your RTT to increase as the number of hops increases. If 1 hop is 80us, then it seems reasonable that 2 hops would be 160us, which is going to
be system dependent. I don’t know how CORE implements bandwidth, but wouldn’t be surprised if it’s a tc configuration (shaper ?) on one of the node interfaces connected to a linux bridge.
<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D">CORE doesn’t emulate software. It runs objective software (e.g. ping, FRR, etc.) in each emulated node (i.e. via kernel virtualization) – the same software that
you’d run outside of CORE. <o:p></o:p></span></p>
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<p class="MsoNormal"><b><span style="font-size:11.0pt;font-family:"Calibri",sans-serif">From:</span></b><span style="font-size:11.0pt;font-family:"Calibri",sans-serif"> dev [mailto:dev-bounces@lists.frrouting.org]
<b>On Behalf Of </b>Lou Berger<br>
<b>Sent:</b> Thursday, April 2, 2020 5:10 PM<br>
<b>To:</b> Sofia Salgueiro <sof97@live.com.pt>; dev@lists.frrouting.org<br>
<b>Subject:</b> Re: [dev] RTT<o:p></o:p></span></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p style="margin-bottom:12.0pt"><span style="color:black">This sounds like a core question to me....<o:p></o:p></span></p>
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<span style="font-size:10.0pt;font-family:"Arial",sans-serif;color:black">On April 2, 2020 6:31:07 PM Sofia Salgueiro <<a href="mailto:sof97@live.com.pt">sof97@live.com.pt</a>> wrote:<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-family:"Calibri",sans-serif;color:black">Good afternoon,<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-family:"Calibri",sans-serif;color:black"><o:p> </o:p></span></p>
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<p class="MsoNormal"><span style="font-family:"Calibri",sans-serif;color:black">I've been using CORE with FRRouting and I've noticed that the PING rtt between two directly connected router devices is approximately 80 us, even if I change the bandwidth of the
links. I've also noticed that this value seems to increase with the number of hops, eg. between 2 routers with 4 links the value doubles to approximately 160 us.<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-family:"Calibri",sans-serif;color:black"><br>
So, I was wondering if maybe you could give me some insight on how the PING is emulated and, more specifically, why the rtt has this value?<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-family:"Calibri",sans-serif;color:black"><o:p> </o:p></span></p>
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<p class="MsoNormal"><span style="font-family:"Calibri",sans-serif;color:black">Best regards,<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-family:"Calibri",sans-serif;color:black">Sofia Salgueiro<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="color:black">_______________________________________________<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="color:black">dev mailing list<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="color:black"><a href="mailto:dev%40lists.frrouting.org">dev@lists.frrouting.org</a><o:p></o:p></span></p>
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<p class="MsoNormal"><span style="color:black"><a href="https://lists.frrouting.org/listinfo/dev">https://lists.frrouting.org/listinfo/dev</a><o:p></o:p></span></p>
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