Hi,
Can someone from Microsoft who manages the network for the Skype for Business please contact me to help resolve what I believe is a problem with the S4B network?
I am experiencing PMTUD issues whereby connections with an IPv4 TCP MSS above 1492 and an IPv6 TCP MSS of above 1432 do not function. I can run a clean 1500 byte MTU on both IPv4 and IPv6 from the connection I am testing with.
External validation (thus ruling out my own link) from https://wand.net.nz/pmtud/ reports that the following URLs used by Lync/S4B are failing PMTUD: