[c-nsp] bfd session flaps troubleshooting

[Mike]

Hi,

     I have an ASR920 connected to an ME3600X-24CX over a gigabit fiber 
link, and I experience periodic cases of BFD flapping.

     The fiber link is a point to point EoMPLS carrier circuit and there 
does not appear to be any interface errors, although one end does seem 
to have excessive output drops (That end is the majority traffic 
originating, too). I have engaged the carrier an after several closed 
tickets without action, I have received an analysis stating nothing 
appears wrong in the carrier mpls network go check my stuff. Although I 
understand the protocol, I don't know what else might cause these flaps 
other than faults in the carrier network. The only idea I have is 
perhaps there are microbursts >=1gbps causing the output drops and BFD 
isn't able to send its control packets out due to a backlogged queue. 
But that would be dumb, bfd should have a direct path to the output 
queue bypassing everything else for exactly this reason.

     I have read a few bfd troubleshooting documents and I don't seem to 
fit into any of the listed scenarios. I would appreciate hearing from 
others who run bfd and any opinions or suggestions where to further look.
Mike-