y.1731 ETH-DM compatibility between ASR 920 and NCS 540

[jhenryz]

I am currently having problems with ETH-DM sessions sourced from ASR 920 towards NCS 540 (N540-ACC-SYS)  as DM responder. The other way around seems to be working, but the NCS/IOS-XR doesn't provide the same metrics ands results as the ASR 920, so it's not an acceptable fix to use that instead. Is this a known caveat or am I doing something wrong?

My none professional analysis indicates that it might be related to timestamping of the DMR messages, packet captures indicates that the replies from the NCS 540 has none compatible offset for the timestamps RX/TX compared to responses from an ASR 920.

I have configured the ip sla sessions in the ASR 920 with the format "ethernet y1731 delay DMMv1" for two way results. I have a parallel SLM session to the same NCS 540 responder which is working fine, utilizing the same Ethernet CFM underlying connectivity. 

[jstampstwtc]

Did you find a solution to make the 540 respond correctly?  If so, it would be nice to see both side configs if you are willing to share.

[jhenryz]

Hi, 

I have not played around with it in a while. We were promised a fix in 7.7.1, but I haven't tested/verified that. What we did instead was to use L2VPN P2P instead of bridge group, then it was working. The problem I found with the responder in bridge mode was that the replies didn't keep the VLAN P-bits (the were all zero), that's why the source of the IP SLA session (ASR920) didn't accept the replies from the NCS540. So, our workaround for the moment is to use P2P in the NCS540 instead, where possible.