Pingman Tools Home Forums PingPlotter PingPlotter Support graph and packet loss

One thing I have noticed is that if I am tracing to a site that is say 10 hops away and I notice packet loss starting at hop 5, why isnt that packet loss showing up on the subsequent hops that I have graphs displaying for?<br><br>Thanks!<br><br><br><br>

Do subsequent hops show packet loss? Quite often, an individual router might be dropping TTL=0 ICMP echo requests under load. This means that any packets that Ping Plotter sends out that it intends to get back with information about this hop - are sometimes (based on load or other conditions defined by the router) dropped.<br><br>The fact that downstream hops are not seeing packet loss means that the router is configured to *pass* ICMP echo requests where TTL > 0 through with a higher priority. This is why a router at one hop might be showing packet loss, but routers further downstream are not.<br><br>When this situation occurs, this doesn't mean there anything wrong with the router showing packet loss. Remember that the most important hop is the final one - and if there is no packet loss at the final hop, then packet loss in any of the OTHER hops is meaningless. Always start to look at the final destination and move backwards from there to determine the problem. <br><br>Hope that helps!<br><br>

Oops - looks like I responded to that last one as "Anonymous". Sorry about that.<br><br>Here's an example of the situation I'm talking about.<br><br><br><br>Notice how hop 4 has 6% packet loss (for 8500 samples, too!), but hop 5 has 0%. Now hop 9 shows 10% packet loss - and the final destination shows 9%. The packet loss at hop 4 isn't contributing to the problem though - even though there's a bump in latency and packet loss at that hop - because it recovers at hop 5. Hop 9, however, adds packet loss that is *NOT* recovered from, so the packet loss at hop 9 is contributing to (and, it appears, causing all of) the packet loss at the final destination. Not completely on-topic, but another key indicator that hop 9 is a problem is that we change domains between hop 8 and hop 9 - from rr.com to alter.net. This points us to a problem in the link between those two routers.<br><br><br>

Thanks again! Great info, you answered my question.<br><br><br>