MPLS micro-cuts and upper-layer problems

Hi Rene,

i’m pretty struggling with a problem which is impossible to see from a “down”-layer view. While PRTG/Smokeping and so on only see how the average RTT goes from, for example, average 5ms to 20ms 20ms 20ms - we have customers complaining about the interruptions and cuts on an upper-layer protocol like tools in DC to branch-office. What you can see is retrans. on TCP session but windows size is always good and whis 32-64bit msgs. Maybe you can advice?

Thank you (ps access is always clean and we do not see any capacity problems).

Hi Dalibor,

This might be difficult to troubleshoot on your own if you can only see the connections on your end. I’m guessing the MPLS connection is offered by a SP? If so, it might be best to inform them what you have found so they can see what is going on. Probably some of your traffic is getting dropped on their end.


hi Rene,

Thank you a lot for writing back on this. Actually regarding these/such cases i’m the one who is trobleshooting the issues from the ISP side. The traffic is switched through MPLS, yes. The worst thing about is that we are troubleshooting “micro cuts” which comes and goes so without any rules that no monitoring tool can record it. while policies and interfaces remain clean.