Cesar,
Thanks for your input. I agree that we should not get into details of
dynamic discovery in the current protocol specification.
We do, however, probably need to put in enough details on preconfiguration
to have the specification be sufficiently stand-alone.
In the meantime, I've taken another stab at this section addressing some of
the concerns raised by Gabor.
Comments are welcomed from all.
-vince
--------------------------------
4.1. Database Discovery
Different regulators may have different requirements for the approval
and operation of databases, such as:
o A regulator may only allow a limited number of certified databases
to operate. It also may require the certification of each device-
to-database pairing.
o A regulator may maintain a trusted website that lists all approved
databases. It also may mandate how devices use the listing
service.
o A regulator may allow each database to define its own terms of
use, so that, for example, an approved device may not be able to
access all approved databases.
Prior to sending PAWS messages, a Device MUST determine the URI for a
Database that provides service at its current location.
o A Device SHOULD support operation in any regulatory environment.
Preconfiguration
The Device MAY be provisioned statically with the URI of one or more
Databases. For operation in regulatory domains that do not have a
listing server, the Device SHOULD be provisioned with the URI of all
the databases for which it is certified or otherwise permitted to
operate. The Device also MAY be provisioned with the URI of listing
servers approved by regulators. To adapt to changes to the list of
certified or approved databases, the Device SHOULD be able to update
its preconfigured lists of databases and listing servers. When the
preconfigured list of databases is provided by a listing service, the
Device SHOULD check the service periodically to update its list. The
time between such updates SHALL be no longer than one week, or any
update interval required by the applicable regulatory domain,
whichever is shorter.
Dynamic Discovery
The Device MAY obtain the URI of one or more Databases dynamically
from authorized and authenticated entities. The Device SHOULD use
dynamic provisioning of Database URIs when the mechanism is defined.
The Device MUST use dynamic provisioning in regulatory domains that
do not allow static provisioning.
Error Handling
Whether the Device's list of databases is preconfigured or obtained
dynamically, the Device SHOULD select an alternate database from the
list if:
o A database is unreachable or does not respond.
o A database returns an UNSUPPORTED error (see Error Codes
(Section 5.13)), which may indicate that the database does not
support the regulatory domain where the device is located.
If a suitable database cannot be contacted, the Device MUST NOT
operate in white space spectrum. If the Device is already operating
when it fails to contact a suitable database, and if the applicable
regulatory domain provides a grace period, the Device may continue to
operate during such period, but must cease operation at or before the
expiration of the grace period. If a grace period is not provided by
the applicable regulatory domain, an operating Device that fails to
contact a suitable database MUST cease operation immediately.
Redirects
The Database MAY redirect a PAWS request by returning a HTTP 3xx
response (as defined by HTTP/1.1 [RFC2616]). The Database MUST
provide the redirect URI in the Location header of the 3xx response,
and the Device MUST handle redirects by using the Location header
provided by the Database. When redirecting, the Device MUST observe
the delay indicated by the Retry-After header. The Device MUST
authenticate the Database that returns the redirect response before
following the redirect. Also, the Device MUST authenticate the
Database indicated in the redirect. Since the Device may communicate
with a Database (which it authenticated) without user interaction,
when the response code is 301 (Moved Permanently), the Device MAY
redirect without asking a user for confirmation (note that this
represents an exception to the HTTP/1.1 [RFC2616] requirements for
HTTP POST methods).
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