Fragmentation of notifications - should I combine them?

[Tim]

Suppose I have a lot of very small characteristics (1 or 2 bytes) to send lots of notifications on. They are all updated simultaneously, though the central doesn't care about that.

When I notify them, does each notification go into a separate BLE packet? Or are they concatenated into a framed stream, and then fragmented into BLE packets by L2CAP? If so what is the overhead per characteristic?

I'm basically working out if it is worth making "combined" characteristics that contain the data from several logical characteristics.

[Petter Myhre]

With our SoftDevices each ATT packet (notification) will go into separate L2CAP packets and will be sent separately over the air.

If the characteristic values are always notified at the same time it would be better to combine them.