Q. Here's a sample traceroute from a user. Router 4 times out! Is that okay?
Quote
2 20 ms 22 ms 22 ms lo0.10.central10.ptw-bng01.plus.net [195.166]
3 20 ms 14 ms 16 ms irb.10.PTW-CR01.plus.net [84.93.249.1]
4 * * * Request timed out.
5 19 ms 19 ms 17 ms gra-g2-a9.fr.eu [178.33.103.218]
6 18 ms 19 ms 17 ms 37.187.36.162
7 * * * Request timed out.
8 97 ms 96 ms 97 ms mwomercs.com [192.99.109.192]
A. Yes! Absolutely. Many core routers often don't respond to pings, they're too busy sending traffic. If you can see, the traffic from hop 3 to hop 5 gets there just fine.
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Q. I used some advanced software and it shows that 60% of the traffic is being dropped!
Quote
A. That's also fine! Many routers simply don't prioritize responding to pings and drop most of them! If it was actually dropping 60% of your traffic, how would 100% of your traffic still make it to the next node?
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Q. I pinged a random router in the traceroute and it didn't respond!
A. That's also fine! Why would it respond to a random ping? If every router on the internet had to respond to pings, folks would be able to do massive DDoS attacks on core components of the internet just by pinging them!
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Q. I did a traceroute and one of the routers is taking way too long to respond!
Quote
2 20 ms 22 ms 22 ms lo0.10.central10.ptw-bng01.plus.net [195.166]
3 20 ms 14 ms 16 ms irb.10.PTW-CR01.plus.net [84.93.249.1]
4 * * * Request timed out.
5 900 ms 867 ms 757 ms gra-g2-a9.fr.eu [178.33.103.218]
6 18 ms 19 ms 17 ms 37.187.36.162
7 * * * Request timed out.
8 97 ms 96 ms 97 ms mwomercs.com [192.99.109.192]
A. Still fine. Same logic here - it's not prioritizing responding to pings because it has other more important stuff to do. Like making sure the traffic that passes through it gets where it is going. If you look, the time at hop 5 is really high, but if it really did take 900ms to pass any traffic, how is the traffic at hop 6 managing to come back in 18 ms?
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Q. What would actually be a problem, then?
A. I'll give some examples from real problems
Quote
Tracing route to mwomercs.com [192.99.109.192]
over a maximum of 30 hops:
1 1 ms <1 ms <1 ms 192.168.1.1
2 30 ms 30 ms 29 ms b-ras1.lmk.limerick.eircom.net [159.134]
3 28 ms 28 ms 28 ms ge-1-1-7.pe1.lmk.lmk-mlw.eircom.net [86.43.247.33]
4 34 ms 39 ms 39 ms 86.43.253.72
5 34 ms 33 ms 33 ms tenge-2-2-1.core1.srl.core.eircom.net [86.43.252.54]
6 49 ms 46 ms 48 ms tenge-2-2-1.pe1.thn.the-thn.eircom.net [86.43.253.114]
7 49 ms 48 ms 45 ms ge7-1-0.corea.thn.london.eircom.net [86.43.244.194]
8 * * 60 ms sw1.tc.lon.ovh.net [195.66.224.220]
9 168 ms 170 ms 166 ms rbx-g2-a9.fr.eu [91.121.128.195]
10 177 ms 75 ms 73 ms 37.187.36.133
11 * * * Request timed out.
12 245 ms 249 ms 258 ms mwomercs.com [192.99.109.192]
Trace complete.
A1. This is a problem! Why is it taking a user in Ireland 177ms to reach our fibre in France when the average user in London can get there in 20ms?
Quote
2 5 ms 6 ms 5 ms 122.28.24.38
3 7 ms 6 ms 6 ms 122.28.24.62
4 8 ms 8 ms 9 ms 221.184.12.221
5 6 ms 6 ms 6 ms 122.28.168.89
6 6 ms 6 ms 6 ms 118.23.168.89
7 13 ms 7 ms 7 ms ae-5.r21.tokyjp05.jp.bb.gin.ntt.net [129.250]
8 7 ms 9 ms 8 ms ae-0.r24.tokyjp05.jp.bb.gin.ntt.net [129.250.6.96]
9 81 ms 75 ms 81 ms ae-3.r21.sngpsi05.sg.bb.gin.ntt.net [129.250.7.35]
10 73 ms 73 ms 76 ms ae-13.r00.sngpsi02.sg.bb.gin.ntt.net [129.250.4.74]
11 75 ms 74 ms 73 ms ae0.singapore2.sin.seabone.net [93.186.133.12]
12 330 ms 333 ms 325 ms xe-2-0-3.milano51.mil.seabone.net [195.22.205.109]
13 329 ms * * mil-1-6k.it.eu [91.121.131.25]
14 * 333 ms * fra-1-6k.de.eu [213.251.128.66]
15 339 ms 337 ms 338 ms sbg-g1-a9.fr.eu [91.121.128.80]
16 * 340 ms 343 ms 37.187.36.153
17 * * * 要求がタイムアウトしました。
18 333 ms 322 ms 329 ms mwomercs.com [192.99.109.192]
A2. This is a problem! Why is this user in JAPAN being sent to Milano, Italy.
Let me know if you see issues like this. : )
There's some other types of problems that are a bit more complicated to discuss that I've left off the list here, but these are the common ones.