As Kevin said, IPv6 is not supported and the memory used per socket depends on exactly what you're doing on top of the various buffers involved. For details on what SSL sizes are supported, you should check with the OpenSSL version that is in NETMF 4.3. Using built in Ethernet, some of the networking functionality is handled by the processor. But most is done by the lwip stack in NETMF. Generally your best bet is to measure and test NETMF in your environment.