Take the 2-minute tour ×
Super User is a question and answer site for computer enthusiasts and power users. It's 100% free, no registration required.

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!

share|improve this question
add comment

1 Answer 1

There are a couple of problems with traceroute.

  1. Forward and return paths are not always the same. traceroute measures both and shows only forward path.
  2. 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.

share|improve this answer
1  
How 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 Nov 7 '12 at 15:40
    
* * * 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 Nov 7 '12 at 15:42
    
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. –  Semen Semenych Nov 7 '12 at 15:56
add comment

Your Answer

 
discard

By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.