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

From: "Rosen, Brian" <[email-masked]>
Date: Wed, 23 Aug 2006 09:46:25 -0400

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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From: Henning Schulzrinne <[email-masked]>
Date: Wed, 23 Aug 2006 10:29:49 -0400

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.

Henning