Your (1) may need to be broken down further:
User maps to network,
network maps to location (network itself may be mobile: planes, trains,
location then maps to PSAP.
Of course, if the user has GPS, then the above may be short-circuited.
> -----Original Message-----
> From: ecrit-bounces@xxxxxxxx [mailto:ecrit-bounces@xxxxxxxx]
> On Behalf Of Henning Schulzrinne
> Sent: Saturday, September 17, 2005 12:00 PM
> To: 'ECRIT'
> Subject: Re: [Ecrit] draft-polk-dhc-uri-00 (big picture)
> I'm not sure a DNS-vs.-DHCP discussion is all that helpful.
> Since a lot of messages have gone back and forth, it would
> help me at least to summarize some of the points and see if
> we can at least agree on the facts.
> # The system we're building has a number of translations
> between the "dial emergency number" and the final IP address
> of the phone of the PSAP call taker, including at least:
> (1) Caller maps location and service desired to PSAP URL,
> possibly using the mapping URL conveyed in DHCP
> (2) The PSAP URL needs to be resolved via a sequence of DNS
> translations (NAPTR, SRV, A), each of which has a TTL value,
> based on standard SIP procedures documented in RFC 3263.
> (3) The DNS resolution points to one or more SIP proxies,
> which in turn route calls to the next step, either another
> SIP proxy closer to the call taker or the call taker. Repeat
> step (2) and (3) until the phone rings.
> # If the PSAP URL(s) are included in the DHCP information,
> presumably the DHCP server performs step (1) above, for each
> attached device based on its location. The draft does not
> really say so, but I'm certainly hoping that this is not
> manually configured. Presumably, this would take place at the
> time the client asks for an address or does a DHCPINFORM.
> Let's see if I got the picture right.
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