[atlas] Measurement question

Hi Michael,
thank you very much for the explanation. I made another measure using UDP and now the collected routes make more sense. I was not aware of the 5 hops without response.

Glad we spot out a particular case 😊

Regards,
Roberto


From: Michel Stam <mstam at ripe.net>
Date: Wednesday, 8 February 2023 at 14:08
To: roberto.lucignani at caleidos.it <roberto.lucignani at caleidos.it>
Cc: Qasim Lone <qlone at ripe.net>, Emile Aben <eaben at ripe.net>, Alexander Burke via ripe-atlas <ripe-atlas at ripe.net>
Subject: Re: [atlas] Measurement question
Hello Roberto,

I’ve done the exact same measurement too, using the 3 types of traceroute available (ICMP, UDP and TCP).
UDP:
(https://atlas.ripe.net/measurements/49826077/#general)
[cid:image001.png at 01D93BD2.0F829F90]


TCP:
(https://atlas.ripe.net/measurements/49826078/#general)
[cid:image002.png at 01D93BD2.0F829F90]

ICMP:
(https://atlas.ripe.net/measurements/49826076/#general)
[cid:image003.png at 01D93BD2.0F829F90]

The way the traceroute works in Atlas is that if 5 hops have been received without response, the trace skips over to TTL 255 and ends the traceroute. This is what you see with TCP and ICMP. The traceroute stops for lack of response. To prove that, I’ve run the trace again, skipping hops 1-7, for both ICMP and TCP:

https://atlas.ripe.net/measurements/49826868/#general
[cid:image004.png at 01D93BD2.0F829F90]

https://atlas.ripe.net/measurements/49826959/#general
[cid:image005.png at 01D93BD2.0F829F90]



  *   100.64.0.0/10 is CGN (Carrier Grade NAT), RFC 6598.
  *   Looking at the traceroute differently:

     *   Hop 1 (AS16509, Amazon EU West, Amazon-02)
     *   Hop 2-7 CGN
     *   Hop 8-9 (AS unknown, but between UK and US, IPROU3-ARIN, so Amazon IP routing 3)
     *   Hop 10 (AS unknown, but between UK and US, IPROU3-ARIN/ARMP-ARIN, Amazon IP routing)
     *   Hop 11-15 CGN
     *   Hop 16 (AS unknown,  presumably US, IPROU3-ARIN/ARMP-ARIN, I presume Amazon IP routing still)
     *   Hop 17-19 CGN
     *   Hop 20 (AS13335, Cloudflare US)

So it seems like every cloud zone interconnect (amazon Europe west, US, then Cloudflare) transitted goes through a CGN setup. Not sure but I can understand if this confuses some types of traffic.

I don’t think there’s anything wrong with your setup, but the results are interesting. I’ve copied a couple of our researchers onto the mail as they may be interested in this as well.

Regards,

Michel


On 8 Feb 2023, at 11:33, roberto.lucignani at caleidos.it wrote:

Hi Michael,
for example, one measure ID is this one: 49813750
The result says there are 7 HOPS.
 The result of the traceroute made directly on the host is the following one
 traceroute to www.madghigno.tech (172.67.221.209), 30 hops max, 60 byte packets
1  52.56.0.19  24.303 ms 52.56.0.31  9.067 ms 52.56.0.17  29.663 ms
2  * 100.65.18.192  7.843 ms 100.65.19.176  6.252 ms
3  100.66.8.254  1.563 ms 100.66.8.146  0.697 ms 100.66.8.168  1.449 ms
4  100.66.10.138  8.469 ms 100.66.10.14  5.713 ms 100.66.10.6  8.127 ms
5  100.66.7.77  1.653 ms 100.66.6.173  2.658 ms *
6  100.66.4.75  2.726 ms 100.66.4.87  2.327 ms 100.66.4.89  1.550 ms
7  100.65.10.65  0.533 ms 100.65.11.1  0.857 ms 100.65.10.161  8.616 ms
8  15.230.158.29  2.062 ms 15.230.158.171  5.998 ms 15.230.158.27  1.617 ms
9  15.230.158.164  1.315 ms 52.94.33.120  2.089 ms 15.230.158.40  1.484 ms
10  54.239.101.83  1.440 ms 150.222.65.23  1.358 ms 54.239.101.87  1.897 ms
11  100.91.211.7  1.368 ms 100.91.13.66  1.956 ms 100.91.13.100  5.077 ms
12  100.91.210.16  1.837 ms 100.100.6.119  1.848 ms 52.93.134.81  2.178 ms
13  100.100.73.70  2.434 ms 100.91.203.106  4.546 ms 100.100.85.70  1.139 ms
14  100.91.207.15  1.289 ms * 100.100.72.67  1.767 ms
15  100.100.2.76  3.616 ms 100.91.201.140  1.955 ms 100.91.205.18  1.744 ms
16  99.83.89.19  6.820 ms 100.91.201.1  2.454 ms 100.91.201.97  2.415 ms
17  100.91.211.89  17.823 ms 172.71.176.2  3.200 ms 172.70.160.2  4.450 ms
18  100.100.6.77  1.805 ms 100.100.6.3  1.943 ms 100.100.6.111  2.005 ms
19  100.100.80.70  1.980 ms 100.100.76.134  2.679 ms 100.100.69.134  2.081 ms
20  172.67.221.209  2.799 ms 100.100.89.209  7.318 ms 100.100.89.17  6.869 ms
 Since the website is served by cloudflare the route may vary between requests but the are always around 18/20 HOPS
 I don’t understand if I0m missing something here. Let me know if you need further details
  Regards,
Roberto
  From: Michel Stam <mstam at ripe.net>
Date: Wednesday, 8 February 2023 at 10:13
To: roberto.lucignani at caleidos.it <roberto.lucignani at caleidos.it>
Subject: Re: [atlas] Measurement question
Hello Roberto,
 Would you be able to share screenshots/measurement ids so we can have a look?
 Regards,
 Michel


On 8 Feb 2023, at 09:04, roberto.lucignani at caleidos.it wrote:
 I’m doing some measurement from one of my software probes, the measure is a traceroute to a destination.
 The results I get are completely different from what I see doing the same traceroute directly on host where the probe is installed. I configured the measure to sue the DNS resolution on the probe..
 From the Atlas portal I get a traceroute with 7 hops, doing it directly on the host returns 28 hops, for the same destination.
 Why this difference ?
  Regards,
Roberto
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