Nowaday almost network system and switch and router support at least MTU is 1500, even on a normal ethernet adapter, but I don't know why the TX 5020E , a new SS7 NMS card still just keep support the maximum MTU at 1400.
The core network of my partners has the infrastructure network support MTU at least 1500 . We can't make change the core of network of partner because there are many services are still running there and they may encounter problem if we did it, and for the most reason, we don't have permission to did that such thing.
We connect our system directly to STP with sigtran connection, we already set PERFORM_MTU = TRUE at SCTP,
We already set MTU for eth which are connecting to STP at maximum 1400. But it still made our SS7 signal blinking because the return message from STP is packet size exceed 1400 bytes. The message return from STP will be dropped at TX 5020E card, because the messages are lost, our app on TX5020E card can't receive and response messages from STP. STP wait and timeou it's will abort our SCTP Association , our SP node retry to establish the SCTP connection so SS7 signalling keeps blinking repeatly.
Hope Dialogic will fix / remove this limitation on next release of Natural Access SS7 TX 5000 series.