Brian Rosen wrote:
The cable systems use the MAC address of the DOCSIS modem to determine which
subscriber is asking for location. It's not perfect, because it is possible
to move a DOCSIS cablemodem from one house to another within some area
(often the service area of the CMTS, but in many systems, less than that).
The ability to move without detection is a problem the have for other
revenue sources and there is some effort being put into systems to detect
that kind of thing. The incidence of moving the cablemodem without notice
is apparently very small.
You don't get the location of the server, you get the location of the
That's only because there's an out of band arrangement with the MSO
and the subscriber. DHCP itself gives no such information. Wireless
substantially confuses the matter too. All it takes is two Pringle's cans
to cast that relationship in doubt.
From: Michael Thomas [mailto:mat(_at_)cisco(_dot_)com]
Sent: Friday, April 20, 2007 9:39 AM
To: Brian E Carpenter
Cc: 'GEOPRIV WG'; 'Dawson,Martin'; ietf(_at_)ietf(_dot_)org; 'Allison Mankin';
Subject: Re: [Geopriv] Confirmation of GEOPRIV IETF 68 Working Group Hums
Brian E Carpenter wrote:
On 2007-04-20 09:21, Hannes Tschofenig wrote:
DHCP is not a great choice in a mobile environment and also not when
it comes to more complex location representations.
Why can't a mobile system have a locally valid DHCP record (+/- the
of a wireless link)? For that matter, why couldn't a DHCP server have
real-time triangulation data, if it exists at all?
Do you mean more complex than can be expressed by RFC 4776 and RFC
If you look at DOCSIS cable, a single head end can subtend a huge amount
of cable in a single bridged domain. I seem to recall that in a rural
MSO I worked with it was 10's if not 100's of miles. I have no clue how
accurate GEOPRIV tries to be, but it sure seems that if the location of
headend/dhcp relay is only piece of information you have, your accuracy is
going to be pretty lousy in many cases. If this information is intended
first responders, it seems that all you're doing is pointing to the
to start searching for the needle.
Mike, who probably shouldn't open his mouth here
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