When IPv6 between gNB and MME on different ORS, TCP throughput between phones with MTU 1500 and ORS is very bad. Setting MTU to 1500 on lo (where the eNB / MME GTP addresses are) fixes the issue.

Unfortunately this also reduces MTU for all local packets which is not great, but the alternative would be to move partition addresses to a different interface.

/cc @tomo