The hardware
eUICC: the physical SIM chip. Unlike a traditional SIM, it can store more than one network profile.
EID: the unique ID of the eUICC chip itself. It stays the same whichever profile is active.
The subscription
Profile: a network subscription stored on the eUICC. It's what used to be the "SIM" in the old sense. Each profile has its own ICCID.
A single eUICC can hold several profiles, but only one is active at a time.
❗ Because the profile and the chip are now separate things, we use the term "profile" for the subscription and "eUICC" for the hardware, rather than "SIM", which can mean either.
The management layer
eIM (eSIM IoT Manager): the server that sends profile instructions to your eUICCs. Onomondo runs its own eIM.
IPA (IoT Profile Assistant): the software that talks to the eIM on the chip's behalf. It comes in two versions:
IPAe: runs inside the eUICC.
IPAd: runs in your device firmware.
PSMO (Profile State Management Operation): an instruction the eIM sends to the chip, such as enable, disable, delete, list profiles or set fallback.
The above components work together to perform:
Polling: your device checks in with the eIM to collect waiting instructions. The eIM doesn't contact the device directly.
Fallback and rollback: safety nets that bring a device back onto a working profile if something goes wrong.
💡 Learn more:
How remote profile management works with the Onomondo eIM
IPAe vs IPAd: which should I use?
Fallback and rollback: keeping devices connected during profile changes