Trying to understand tracert output

I'm looking at the following tracert ouput:

  1    <1 ms    <1 ms    <1 ms  my-router-ip
  2     *       14 ms     2 ms  something-from-my-isp
  3   182 ms   157 ms   158 ms  something-dynamic-from-my-isp
  4    54 ms    53 ms    53 ms  something-in-between
  5    59 ms    59 ms    58 ms  something-in-between
  6   168 ms   211 ms   173 ms  something-in-between
  7   178 ms   178 ms     *     something-in-between
  8   176 ms   173 ms   171 ms  something-in-between
  9   185 ms   185 ms   182 ms  final destination

What I do not understand is line #3. How can the delay in a given hop be greater than the next hop's delay? Aren't they supposed to sum up?

Also, is it possible to at least suppose why the dynamic ISP server is taking so much time to reach? It is located somewhere in my city, so this looks really weird to me.

Thank you!

traceroute

iksemyonov

Posted 2012-11-07T15:16:47.537

Reputation: 193

Answers

There are a couple of problems with traceroute.

Forward and return paths are not always the same. traceroute measures both and shows only forward path.
Routers deprioritize ICMP ttl exceeded replies and that adds latency (a lot of it sometimes)

In your case, it seems like it's the second.

Rajesh

Posted 2012-11-07T15:16:47.537

Reputation: 146

1How would you interpret a hop with 3 stars, as opposed to a hop that may have a MS reading 1 or 2 times and then a * or some variation of that? – j_bombay – 2012-11-07T15:40:39.210

- could mean a router in the path does not return ICMP messages, or that it returns the message with a TTL too small to get back to you, or the router could be faulty.

< – Paul – 2012-11-07T15:42:32.073

Well, 2) is a reason for increased latency. What I'm trying to understand is, why does it not sum up the latencies? In this regard, the actual reason is not as useful. Still, thank you for the input, that's another direction for me to search in. – iksemyonov – 2012-11-07T15:56:54.370

If I understood your first question right: No, they are not suppose to sum-up. Good explanation of tracert can be found at ( http://technet.microsoft.com/en-us/library/ff961507.aspx ) Hope that address your question.

user176105

Posted 2012-11-07T15:16:47.537

Reputation: 46

Please provide an explanation of the link you provided for this site. If your link goes dead then so does this answer. Thanks for your contribution. – jAce – 2015-10-12T10:38:16.790