On 19 July 2013 08:38, Andrew Allen <aallen@xxxxxxxxxxxxxx> wrote: > > I suggest you also read > http://datatracker.ietf.org/doc/draft-allen-dispatch-imei-urn-as-instanceid/ I read that document. The placement of IMEI in the instance id is a little bit of a non-sequitur to my thinking. There are three cases identified where it might be necessary to convey an IMEI, but no real motivation is provided for why it has to be included, specifically, in the instance ID. Nor is it the case that all of these cases necessarily require that IMEI is conveyed in the clear. I can imagine solutions to the real problems that do not require that an IMEI transit the network. However, I'll concede that the relationship between a network provider and the devices that use the network does not necessarily grant those devices any right protections of the form in which Tim seems to be assuming to be necessary. The real risk here is with scope of use. I'd have thought that a P- header would have been more appropriate for these use cases.