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I need to estimate network connectivity of various dedicated server hosting providers, e.g. how fast and uniform will my services perform when hosted there. I use traceroute command on my home computer to check the servers that are hosted by the provider; if I don't know any, then I traceroute their homepage (I know it might not be on the same network; it's a guess)

Intuitively I aim for:

  1. minimum number of hops,
  2. minimum roundtrip time both for the target and intermediate nodes,
  3. and lack of stars:

*stars*: traceroute soyoustart.com

Are all these metrics relevant for general web service hosting? What do stars mean and should I really avoid them?

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The stars mean a device in the chain didn't respond to your ICMP / UDP packet. That can be a router, firewall or a host configured not to respond. They're usually only interesting if you get them mixed in with responses, e.g.

21 * 10 ms *

which suggests the device at or around hop 21 is intermittently responding or is intermittently available.

Whether the metrics you gather are useful depends on what services you're hosting at the end of the connection. Web browsers require a different kind of performance to streamed video or multi-chat audio, etc.

In general, the numbers (response time and number of hops) do impact performance, but for web browsing it's probably negligible unless some hop in the route is >200ms. Much more worrying would be a lot of stars mixed with responses on the same lines (lines full of stars are harder to interpret if you don't know whether the connection used to work).

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Number of hops (if reasonable) and response time of intermediate devices is completely unimportant, because:

1) These devices are not designed to respond lossless your icmp requests

2) Often there is icmp rate limiting policy on routers

3) Pings directed to router must be processed by CPU, forwarded packets don't

You should measure RTT and packet loss end-to-end only.

Stars in output of traceroute means, that this device does not replies with echo icmp when TTL packet exeeded (It's how traceroute works, sends icmp request to target starting with ttl=1 and increasing this value by 1)

  • What does it mean if the number of hops is unreasonable? I ran out of 50 hops on So you Start (an OVH trademark), the last couple of dozen hops being all stars. Looks suspicious to me, what exactly is going on here? – Nickolai Leschov May 2 '14 at 20:16
  • it depends, but certainly more than 30 hops (default for traceroute) IS unreasonable. The page you introduced is not trivial, because if you will request content from this page, it will delivered from nearest CDN to you (try ping this domain, and look at ttl value, for me its 250 - initial was probably 256, so its 6 hops away, rtt~12ms, and reverse dns is 198-27-92-2.any.cdn.anycast.me). Traceroute to this page will filled with stars always, it's not suspicious - it's network policy – fazie May 2 '14 at 20:31

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