Q: In case it is requested to work in IPv4, which features will not work?

A:  We already work on "IPv4 only" networks by deploying an IPv6 overlay. This gives us a unique IPv6 range for each ORS which simplifies management a lot.

In the event this IPv6 overlay is rejected, then an IPv4 address plan must be considered. This is what we do with Teralab.

Usually, non public IPv4 addresses will be used, which means that some types of remote management and multi-site, latency optmised resilient networking need for fully leveraging edge computing could be lost, in addition to losing IPv6 support for services that are deployed. 

IPv6 architecture is based on Re6st (https://re6st.nexedi.com). This is a hybrid mesh network which relies on hundreds of routers worldwide. Thanks to babel technology (RFC 6126), all sorts of congestions can be avoided. Latency can be minimized. In order for this to work, re6st must be able to open VPN tunnel to outside world. That's why we always ask the ORS to be connected to "public" internet (meaning without any firewall).

It will however work perfectly (as in Teralab) in a "closed network" context.