To add to the confusion, the help on macaddress.io says on What is an Organizationally Unique Identifier (OUI)?, emphasis mine:
An OUI is a 24-bit globally unique assigned number. An OUI is assigned with a MA-L identifier block …
So, I’d expect the OUI to be 3 bytes, not 4½ bytes (36 bits) as shown in TTN’s registration. However, the 24 bits 70:B3:D5 is registered to IEEE itself, probably to allow for assigning it to multiple smaller blocks.
And from macaddress.io’s What is a MA-L, MA-M, MA-S assignment?
Name Full name Previously named Number of Addresses MA-L MAC Address Block Large OUI (Organizationally Unique Identifier) 224 ~= 16 Million MA-M MAC Address Block Medium - 220 ~= 1 Million MA-S MAC Address Block Small OUI-36 (encompasses IAB Assignments) 212 ~= 4,096
So, only 12 bits in 212 for the remaining 28 bits of an EUI-64 with a 36 bits OUI? I’m quite sure that 4,096 “addresses” would not suffice for TTN. So again I think that macaddress.io is focused on true MAC addresses, using a total of 48 bits?
And, finally, from What is an Individual Address Block (IAB)?, probably no longer relevant:
The Individual Address Block is an inactive registry activity, which was replaced by the MA-S registry product as of January 1, 2014. The owner of a previously assigned IAB may continue to use the assignment until its exhaustion. The IAB was used by organizations and companies that required less than 4097 unique 48-bit numbers (EUI-48) and thus found little sense in buying their own OUI. The IAB uses a MA-L (and OUI) belonging to the IEEE Registration Authority, linked with 12 additional IEEE-provided bits (for a total of 36 bits), leaving only 12 bits for the IAB owner to assign to their individual devices (up to 4096).
@htdvisser, am I right to assume that TTN just uses all 28 rightmost bits of the assigned MA-S block?