I am developing an app which will be installed on multiple devices, which will need to communicate with each other.
As the connected devices will be on the same network, I intend to use IPv6 link local addressing on the assumption that
- All Android devices support IPv6
- All Wifi networks can carry link-local IPv6
Are these assumptions correct?
My motivation for this is really minimal user configuration although I guess there are other ways to achieve this.
In response to the comment I am attempting to answer my own question though the project is question is on hold:
Wifi is a layer two network, like Ethernet. Specifically, peers communicate with each other using MAC addresses.
So, when one host wants to communicate with a peer on the same LAN using, say IPv4, it uses ARP to determine the MAC address of the peer based on the IPv4 address. For IPv6, neighbour discovery protocol (part of ICMPv6) is used to achieve the same. To the Wifi hardware, it matters not whether the layer 3 protocol is ARP, IPv4, IPv6 or some non IP-related protocol - to the Wifi hardware it's all just Ethernet packets.
So the only issue would be if the Wifi base station has some kind of filtering built in to explicitly suppress ICMPv6 for security.
Remember my question was specifically about link-local - of course if you want to route IPv6 outside of the LAN then there has to be an IPv6-aware router. That router may or may not be the same device as the Wifi base station.
As for the question of whether link-local IPv6 is available on all (modern) android devices, I think it's a safe bet. Remember the link-local address is derived autonomously from the MAC address - there doesn't need to be anything installed on the network to facilitate this.