Internet DRAFT - draft-rosen-ecrit-lost-planned-changes
draft-rosen-ecrit-lost-planned-changes
ecrit B. Rosen
Internet-Draft Neustar
Intended status: Standards Track October 19, 2015
Expires: April 21, 2016
Validation of Locations Around a Planned Change
draft-rosen-ecrit-lost-planned-changes-03
Abstract
This document defines an extension to LoST (RFC5222) that allows a
planned change to the data in the LoST server to occur. Records that
previously were valid will become invalid at a date in the future,
and new locations will become valid after the date. The extension
adds two elements to the <findservice> request: a URI to be used to
inform the LIS that previously valid locations will be invalid after
the planned change date, and add a date which requests the server to
perform validation as of the date specified. It also adds an
optional TTL element to the response, which informs all queriers the
current expected lifetime of the validation.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
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This Internet-Draft will expire on April 21, 2016.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Conventions used in this document . . . . . . . . . . . . . . 3
3. <plannedChange> element . . . . . . . . . . . . . . . . . . . 4
4. <locationInvalidated> object . . . . . . . . . . . . . . . . 4
5. uri Not Stored Warning . . . . . . . . . . . . . . . . . . . 4
6. TTL in Response . . . . . . . . . . . . . . . . . . . . . . . 5
7. Relax NG Schema . . . . . . . . . . . . . . . . . . . . . . . 5
8. Security Considerations . . . . . . . . . . . . . . . . . . . 8
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8
9.1. Relax NG Schema Registration . . . . . . . . . . . . . . 8
9.2. LoST Namespace Registration . . . . . . . . . . . . . . . 9
10. Normative References . . . . . . . . . . . . . . . . . . . . 9
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 9
1. Introduction
This document describes an update to the LoST protocol [RFC5222]
which allows a <findservice> request to optionally add a URI and a
date to be used with planned changes to the underlying location
information in the server. The URI is retained by the LoST server,
associated with the data record that was validated, and used to
notify the LIS (the LoST client) when a location which was previously
valid will become invalid. The date is used by the client to ask the
server to perform validation as of a future date. In addition to
this mechanism, the lt;findserviceResponse> is also extended to
provide a TTL for validation, after which the client should
revalidate the location.
Validation of civic locations involves dealing with data that changes
over time. A typical example is a portion of a county or province
that was not part of a municipality is "annexed" to a municipality.
Prior to the change, the content of the PIDF A3 element would be
blank, or represent some other value and after the change would be
the municipality that annexed that part of the county/province. This
kind of annexation has an effectivity date and time (typically 00:00
on the first or last day of a month).
Records in a LIS must change around these kinds of events. The old
record must be discarded, and a new, validated record must be loaded
into the LIS. It is often difficult for the LIS operator to know
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that records must be changed around such events. There are other
circumstances where locations that were previously valid become
invalid, such as a street renaming or renumbering event. As RFC5222
defines validation, the only way for a LIS to discover such changes
was to periodically revalidate its entire database. Of course, this
would not facilitate timely changes, is not coordinated with the
actual change event, and also adds significant load to the LoST
server. Even if re-validation is contemplated, the server has no
mechanism to control, or even suggest the time period for
revalidation
This extension allows the client to provide a stable URI that is
retained by the server associated with the location information used
in the request. In the event of a planned change, or any other
circumstance where the LI becomes invalid, the server sends a
notification to the URI informing it of a change. The notification
contains the date and time when the LI becomes invalid.
Ideally, following such a notification, the LIS will prepare a new
record to be inserted in its active database, that becomes active at
the precise planned event date and time, at which point it would also
delete the old record. However, the new record has to be valid, and
the LIS would like to validate it prior to the planned change event.
If it requests validation before the planned event, the server
(without this extension) would inform the client that the location
was invalid. This extension includes an optional "asOf" date and
time in the request that allows the LoST server to provide validation
as of the date and time specified, as opposed to the "as of now"
implied in the current LoST protocol.
When it is not practical or advisable for the LIS to maintain stable
URIs for all of its records, periodic revalidation can be still used
to maintain the data in the LIS. However, the server should be able
to control the rate of such revalidation. For this purpose, a new
TTL element is included in the lt;findserviceResponse> which provides
advice from the server to the LIS of when validation is suggested.
2. Conventions used in this document
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119].
"Server" in this document refers to the LoST server and "Client" is
the LoST client, even when the server is performing an operation on
the client.
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3. <plannedChange> element
This document defines a new element to <findService> called
'plannedChange'. This element contains two attributes: 'uri' and
'asOf'. The 'uri' attribute MUST be a URI with a scheme of https.
The URI will be stored by the server against the location in the
request for subsequent use with the notification function defined
below. To minimize storage requirements of at the server, the length
of the URI MUST be less than 256 bytes. Each client of the server
may only store one URI against a location, where "location" is
defined by policy at the server, since a given unique location may
have many combinations of LI elements that resolve to the same
location. If the server receives a 'uri' for the same location from
the same client, the URI in the request replaces the URI it
previously retained. Policy at the server may limit how many uris it
retains for a given location. A new warning is defined below to be
used to indicate that the URI has not been stored. If the location
in the request is invalid, the uri will not be stored and the warning
will be returned.
The 'asOf' attribute contains a date and time. The server will
validate the location in the request as of the date specified, taking
into account planned changes. This allows the client to verify that
it can make changes in the LIS commensurate with changes in the LoST
server by validating locations in advance of a change.
4. <locationInvalidated> object
When the server needs to invalidate a location where the client
provided a URI in <plannedChange>, the server executes an HTTPS POST
containing <locationInvalidated> to the URI previously provided.
This is the notice from the server to the client that the location
may be invalid and should be revalidated. <locationInvalidated>
contains an asOf attribute that specifies when the location may
become invalid. If the date/time in asOf is earlier than the time
the <locationInvalidated> was sent, the location may already be
invalid and the LIS should take immediate action. If the POST
operation fails, the server MAY retry the operation immediately, and
if it fails again, retry the operation at a later time.
5. uri Not Stored Warning
A new warning is added to the exceptionContainer, 'uriNotStored'.
This warning MUST NOT be returned unless the plannedChange element
was found in the corresponding request. The warning is returned when
the server decides not to store the URI found in the plannedChange
element. As discussed above, this may occur because, among other
reasons, the policy at the server limits how many URIs will be stored
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against a specific location, the uri is not well formed or the policy
at the server has some other restriction on the feature.
6. TTL in Response
A new 'ttl' element is added to the lt;findserviceResponse>. The ttl
element contains a date and time after which the client may wish to
revalidate the location at the server. This element MAY be added by
the server if validation is requested in the response. The form of
the element is the 'expires' pattern, which allows explicit 'No
Cache' and 'No Expiration' values to be returned. 'No Cache' has no
meaning and MUST NOT be returned in TTL. 'No Expiration' means the
server does not have any suggested revalidation period.
Selecting a revalidation interval is a complex balancing of
timeliness, server load, stability of the underlying data, and policy
of the LoST server. Too short, and load on the server may overwhelm
it. Too long and invalid data may persist in the server for too
long. The URI mechanism provides timely notice to coordinate
changes, but even with it, it is often advisable to revalidate data
eventually.
In areas that have little change in data, such as fully built out,
stable communities already part of a municipality, it may be
reasonable to set revalidation periods of 6 months or longer,
especially if the URI mechanism is widely deployed at both the server
and the clients. In areas that are quickly growing, 20-30 day
revalidation may be more appropriate even though such revalidation
would be the majority of the traffic on the LoST server.
When a planned change is made, typically the TTL for the affected
records is lowered, so that revalidation is forced soon after the
change is implemented. It is not advisable to set the expiration
precisely at the planned change time if a large number of records
will be changed, since that would cause a large spike in traffic at
the change time. Rather, the expiration time should have a random
additional time added to it to spread out the load.
7. Relax NG Schema
The Relax NG schema in [RFC5222] is extended to include:
namespace a = "http://relaxng.org/ns/compatibility/annotations/1.0"
default namespace ns1 = "urn:ietf:params:xml:ns:lost-plannedChange1"
##
## Extension to Location-to-Service Translation (LoST) Protocol
## to support a planned change to location data
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##
## plannedChange is used in the extensionPoint of
## commonRequestPattern in a findService request
##
## locationInvalidated is used by the LoST server to notify a
## LIS that a previously valid location may be (or will become)
## invalid
##
## ttl is used in the extensionPoint of
## commonResponsePattern in a findService response
##
## uriNotStored is a new warning to be used in a
## exceptionContainer in the warnings element of a
## findServiceResponse
##
start =
plannedChange
| locationInvalidated
| uriNotStored
##
## plannedChange
##
div {
plannedChange =
element plannedChange {
attribute uri {
xsd:anyURI }?,
attribute asOf {
xsd:dateTime }?,
extensionPoint+
}
}
##
## locationInvalidated
##
div {
locationInvalidated =
element locationInvalidated {
attribute asOf {
xsd:dateTime }?,
extensionPoint+
}
}
##
## ttl
##
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div {
ttl =
element ttl {
expires,
extensionPoint+
}
}
##
## uriNotStored
##
div {
uriNotStored =
element uriNotStored { basicException }
}
##
## Patterns for inclusion of elements from schemas in
## other namespaces.
##
div {
##
## Any element not in the LoST namespace.
##
notLostChange = element * - (ns1:* | ns1:*) { anyElement }
##
## A wildcard pattern for including any element
## from any other namespace.
##
anyElement =
(element * { anyElement }
| attribute * { text }
| text)*
##
## A point where future extensions
## (elements from other namespaces)
## can be added.
##
extensionPoint = notLostChanged*
}
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8. Security Considerations
As an extension to LoST, this document inherits the security issues
raised in [RFC5222]. The server could be tricked into storing a
malicious URI which, when sent the locationInvalidated object could
trigger something untoward. The server MUST NOT accept any data from
the client in response to POSTing the locationInvalidated.
The server is subject to abuse by clients because it is being asked
to store something and may need to send data to an uncontrolled URI.
Clients could request many URIs for the same location for example.
The server MUST have policy that limits use of this mechanism by a
given client. If the policy is exceeded, the server returns the
uriNotStored warning. The server MUST validate that the content of
the uri sent is syntactically valid and meets the 256 byte limit.
When sending the locationInvalidated object to the uri stored, the
server MUST protect itself against common http vulnerabilities.
The mutual authentication between client and server when is
RECOMMENDED for both the initial findService operation that requests
storing the uri and the sending of the locationInvalidated object.
The server should be well known to the client, and its credential
should be learned in a reliable way. For example, a public safety
system operating the LoST server may have a credential traceable to a
well known Certificate Authority known to provide credentials for
public safety agencies. Many of the clients will be operated by
local ISPs or other service providers where the server operator can
reasonably obtain a good credential to use for the URI. Where the
server does not recognize the client, its policy MAY limit the use of
this feature beyond what it would limit a client it recognized.
9. IANA Considerations
9.1. Relax NG Schema Registration
URI: urn:ietf:params:xml:schema:lost-planedChange1
Registrant Contact: IETF ECRIT Working Group, Brian Rosen
(br@brianrosen.net).
Relax NG Schema: The Relax NG schema to be registered is contained
in Section 5. Its first line is
default namespace = "urn:ietf:params:xml:ns:lost-PlannedChange1
and its last line is
}
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9.2. LoST Namespace Registration
URI: urn:ietf:params:xml:ns:lost-plannedChange1
Registrant Contact: IETF ECRIT Working Group, Brian Rosen
(br@brianrosen.net).
XML:
BEGIN
<?xml version="2.0"?>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML Basic 1.0//EN"
"http://www.w3.org/TR/xhtml-basic/xhtml-basic10.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="content-type"
content="text/html;charset=iso-8859-1"/>
<title>LoST Planned Change Namespace</title>
</head>
<body>
<h1>Namespace for LoST Planned Change extension</h1>
<h2>urn:ietf:params:xml:ns:lost-plannedChange1</h2>
<p>See <a href="http://www.rfc-editor.org/rfc/rfc????.txt">
RFC????</a>.</p>
</body>
</html>
END
10. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<http://www.rfc-editor.org/info/rfc2119>.
[RFC5222] Hardie, T., Newton, A., Schulzrinne, H., and H.
Tschofenig, "LoST: A Location-to-Service Translation
Protocol", RFC 5222, DOI 10.17487/RFC5222, August 2008,
<http://www.rfc-editor.org/info/rfc5222>.
Author's Address
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Brian Rosen
Neustar
470 Conrad Dr
Mars, PA 16046
US
EMail: br@brianrosen.net
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