Re: [Geopriv] "PossibyMobile" attribute in PIDF-LO

From: Henning Schulzrinne ^lt;>
Date: Wed Aug 23 2006 - 10:29:49 EDT

There are two possibly more general solutions:

- timed-presence, where the source can indicate how long it
anticipates the location to be valid. If the location-information is
coarse-grained, even a highly mobile device may have information that
is valid for minutes or hours.

- stretching the definition a bit, the LO retention period.

Thus, I'm not convinced that a simple flag is all that helpful. Just
about any device in California is mobile if you wait long enough.


On Aug 23, 2006, at 9:46 AM, Rosen, Brian wrote:

> We need a flag in PIDF-LO that indicates that the location supplied
> may
> change over time periods of less than normal lease times of IP
> addresses. It can't be reliable, that is, it can't guarantee the
> location WILL change, only that it could, and therefore needs to be
> refreshed before it is used.
> Take the following scenario:
> A hardwired VoIP phone, sold for use in a fixed enterprise environment
> is connected to an Ethernet switch, which is plugged into a small
> router. The router uplink is a GPRS (or EvDO, or Satellite) radio
> modem. The entire network is installed in an RV, and is "moving down
> the highway, looking for adventure" in Montana. The phone is on a VPN
> to an IP-PBX located in, of course, Sierra Leone.
> Let's say the phone acquired its location from somewhere. For the
> moment, don't worry about how that happened. Suppose the phone
> makes an
> emergency call.
> Somehow, the phone has to know it should retry its location
> acquisition
> query and get a new location before it places the call. That's
> what the
> flag is for.
> We'll also need this flag in the DHCP location options, and someone
> ought to tell the LLDP-MED guys.
> Brian
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