Internet DRAFT - draft-gellens-lost-validation
draft-gellens-lost-validation
Network Working Group R. Gellens
Internet-Draft Core Technology Consulting
Updates: 5222 (if approved) B. Rosen
Intended status: Standards Track July 1, 2020
Expires: January 2, 2021
The LoST-Validation S-NAPTR Application Service Tag
draft-gellens-lost-validation-09
Abstract
This document adds the "LoST-Validation" service tag to the
Straightforward Naming Authority PoinTeR (S-NAPTR) Application
Service Tag IANA registry. This tag can appear in a Naming Authority
Pointer (NAPTR) Domain Name System (DNS) record to assist clients of
the Location-to-Service Translation Protocol (LoST) in identifying
LoST servers explicitly willing to perform location validation. This
tag and the information on its use is an update to RFC5222 that
enables the explicit discovery of a server that supports location
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 January 2, 2021.
Copyright Notice
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Table of Contents
1. Document Scope . . . . . . . . . . . . . . . . . . . . . . . 2
2. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
3. The LoST-Validation Application Service Tag . . . . . . . . . 3
4. Backwards Compatability . . . . . . . . . . . . . . . . . . . 4
5. Security Considerations . . . . . . . . . . . . . . . . . . . 5
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6
6.1. S-NAPTR Registration . . . . . . . . . . . . . . . . . . 6
7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 6
8. Changes from Previous Versions . . . . . . . . . . . . . . . 6
8.1. Changes from -00 to -01 . . . . . . . . . . . . . . . . . 6
8.2. Changes from -01 to -02 . . . . . . . . . . . . . . . . . 7
8.3. Changes from -02 to -03 . . . . . . . . . . . . . . . . . 7
8.4. Changes from -03 to -04 . . . . . . . . . . . . . . . . . 7
8.5. Changes from -04 to -05 . . . . . . . . . . . . . . . . . 7
8.6. Changes from -05 to -06 . . . . . . . . . . . . . . . . . 7
8.7. Changes from -06 to -07 . . . . . . . . . . . . . . . . . 7
8.8. Changes from -07 to -08 . . . . . . . . . . . . . . . . . 8
8.9. Changes from -08 to -09 . . . . . . . . . . . . . . . . . 8
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 8
9.1. Normative References . . . . . . . . . . . . . . . . . . 8
9.2. Informative references . . . . . . . . . . . . . . . . . 8
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 9
1. Document Scope
This document adds 'LoST-Validation' to the S-NAPTR Application
Service Tag IANA registry, and describes how this tag fits in the
LoST server discovery procedure described in [RFC5222]. This tag is
used with Naming Authority Pointer (NAPTR) Domain Name System (DNS)
records so that clients of the Location-to-Service Translation
Protocol (LoST) [RFC5222] can identify servers explicitly willing to
perform location validation. This tag and the information on its use
is an update to [RFC5222] that enables the explicit discovery of a
server that supports location validation.
2. Introduction
The Location-to-Service Translation Protocol, LoST [RFC5222] defines
a mapping service with the additional ability for a client to request
that a civic address be validated. The LoST protocol allows servers
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to ignore a request to perform location validation. The National
Emergency Number Association (NENA) has defined an architecture for
all-IP emergency services (known as "i3" [NENA-i3]), which defines
the mapping (routing) and validation functions as two distinct
functional elements, defined as an Emergency Call Routing Function
(ECRF) and a Location Validation Function (LVF). NENA i3 requires
that the mapping (ECRF) and validation (LVF) functions be separable,
so that an entity responsible for a LoST server cluster can decide to
provide mapping and validation services using consolidated or
separate server clusters (i.e., using the same or separate boxes).
The rationale is that the mapping service is used in real-time during
emergency call routing, while the validation service is used in
advance, typically when data is provisioned, and therefore the
mapping service has much higher availability and response time
requirements than the validation service. An organization might
choose to deploy these services using different server clusters to
make it easier to provide higher levels of service for the mapping
function while shielding it from the potentially bursty load of
validation, while another organization might choose to use the same
sets of servers for both, configured and deployed to offer the high
service level demanded of the mapping service.
In order to permit this separability, any entity querying a LoST
server needs to be able to resolve an Application Unique String (AUS)
into a URL for a LoST server that offers the required service
(mapping or validation). This separability needs to be maintained
throughout the LoST tree structure, from forest guide to leaf node
(LoST architecture is described in [RFC5582]). Because LoST
referrals return an AUS rather than a URL, either a different Service
Tag or a DNS name convention (e.g., "ecrf.example.org" and
"lvf.example.org") is needed to differentiate the different services.
DNS name conventions are inflexible and fragile, making a different
service tag the preferred approach.
Because a server discovered using the "LoST" application service tag
may ignore a request to perform location validation, a service tag
explicitly for location validation also reduces the likelihood (which
has existed since [RFC5582]) of a client requiring location
validation reaching servers unwilling to do so.
3. The LoST-Validation Application Service Tag
This document adds 'LoST-Validation' to the S-NAPTR Application
Service Tag registry created by [RFC3958]. The 'LoST-Validation' tag
serves as a counterpart to the 'LoST' tag added by [RFC5222]: The
'LoST' tag identifies servers able to perform the core mapping
function, while 'LoST-Validation' identifies servers explicitly
willing to perform the validation function.
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Because some servers might be configured to provide both mapping and
validation functions, a server identified using the 'LoST' service
tag might also perform the validation function (and resolving the two
tags might result in the same URL). Because the two functions might
be separate, clients seeking a LoST server for location validation
can first try U-NAPTR resolution using the 'Lost-Validation' service
tag, and fallback to the 'LoST' service tag if this does not resolve
to a usable LoST server.
LoST [RFC5222] specifies that LoST servers are located by resolving
an application Unique String (AUS) using U-NAPTR/DDDS (URI-Enabled
NAPTR/Dynamic Delegation Discovery Service) [RFC4848], and defines
the 'LoST' Application service tag. In order to permit separability
of the mapping and validation services performed using LoST, and to
reduce the likelihood of a client requiring location validation
reaching servers unwilling to do so, this document defines the 'LoST-
Validation' service tag. NAPTR records for LoST servers available
for location validation contain the 'LoST-Validation' service tag.
An entity needing to perform location validation using LoST performs
the discovery procedure as described in [RFC5222], except that the
'LoST-Validation' service tag is used in preference to the 'LoST'
service tag. For both service tags, the HTTP and HTTPS URL schemes
are used. In the absense of any NAPTR records containing the 'LoST-
Validation' service tag, the 'LoST' service tag is used. Fallback to
the 'LoST' service tag may follow if the 'Lost-Validation' service
tag fails to result in a usable LoST server. The discovery procedure
with the 'LoST-Validation' service tag might result in the same URL
as the 'LoST' service tag, or it may result in a different URL. When
the URLs are different, they could lead to the same physical servers,
or different servers.
4. Backwards Compatability
The primary use of LoST in general, and the location validation
functionality in particular, is within the emergency services area.
Within North America, the NENA i3 [NENA-i3] document specifies how
protocols including LoST are used. The i3 document is expected to
reference the 'LoST-Validation' service tag, and specify its use in
both server NAPTR DNS records and client resolution of Application
Unique Strings (AUS).
LoST allows a server to refuse to perform location validation, and
defines the 'locationValidationUnavailable' warning. LoST also
allows a server to refer to another server rather than answering
itself. So, in a deployment where a LoST tree has separate server
clusters for mapping and for validation, mapping servers receiving a
request for validation could either perform the validation as
requested, or return the 'locationValidationUnavailable' warning, and
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potentially also include a <redirect> element to redirect to a
validation server. However, the <redirect> element contains an
Application Unique String, so unless the AUSs for validation and
mapping are different (e.g., 'ecrf.example.org' and
'lvf.example.org'), we still need a different service tag to allow
for flexible deployment choices (i.e., not requiring a DNS name
convention).
LoST clients performing emergency services operations are expected to
comply with the latest NENA i3 specification, and hence support the
'LoST-Validation' service tag when defined. A LoST client
implemented prior to the addition of the 'LoST-Validation' tag would
use the 'LoST' tag to resolve an AUS. Such a client might not be
performing location validation, but if it is, the LoST server it
contacts may perform the service. Even in a deployment where mapping
and validation are split, the data is identical; the split is a load
and deployment optimization strategy. The server designated for
mapping is likely to perform validation when requested, potentially
unless it is under load. If an older client attempts validation
using a designated mapping server that refuses the request, the
client will retry later, at which point the server may no longer be
under load and may provide the function. Even in the (unlikely) case
of a designated mapping server that refuses to perform validation at
any time, the server could return a redirect with a different AUS
(e.g., "lvf.example.com") that resolves to a designated validation
server. In the (unlikely) worst case, the client will be unable to
reach a server willing to perform validation, and will submit a
discrepancy report, as specified in NENA i3. The discrepancy report
resolution would be to update the client with the 'LoST-Validation'
service tag, update the AUS returned in a redirect and DNS to use a
different DNS host name, or permit the server to perform validation
when not under stress (or a combination). Note that, because LoST
does not require servers to perform validation, the situation
described can exist regardless of the addition of the 'LoST-
Validation' service tag. The addition of the tag improves the
likelihood of a client needing validation being able to do so.
5. Security Considerations
The security considerations described in [RFC3958], [RFC4848], and
[RFC5222] apply here. No additional security aspects are foreseen by
the addition of an extra tag. Separation of services might be
desired, for example, to be able to allocate different levels of
resources (such as server capacity, attack mitigation, bandwidth,
etc.) to the mapping and validation services, in which case separate
tags are needed to allow LoST clients (which may include other LoST
servers) to identify the correct server cluster.
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[RFC5222] descriptively discusses the use of DNS Security [RFC4033]
to mitigate the risk of DNS-based attacks. Because DNS Security has
become more widely deployed since the publication of [RFC5222], such
measures SHOULD be used when performing NAPTR resolution. Note that,
while there are valid reasons to proceed with a LoST mapping query
despite security failures while initiating or processing an emergency
call, these concerns generally do not apply to a loST validation
query done in advance of an emergency call.
6. IANA Considerations
IANA is requested to add 'LoST-Validation' to the S-NAPTR Application
Service Tag registry created by [RFC3958] This tag serves as a
counterpart to the 'LoST' tag added by [RFC5222].
(Note that IANA and [RFC3958] call this registry "S-NAPTR Application
Service Tags" while [RFC5222] calls it "U-NAPTR application service
tag".)
6.1. S-NAPTR Registration
This document registers an S-NAPTR application service tag:
Application Service Tag: LoST-Validation
Defining Publication: This document.
7. Acknowledgements
Many thanks to Ted Hardie, Ben Campbell, Dan Banks, Pete Resnick,
Shawn Emery, Robert Wilton, Roman Danyliw, and Benjamin Kaduk for
their helpful reviews and suggestions, and to Barry Leiba for
shepherding the document.
8. Changes from Previous Versions
8.1. Changes from -00 to -01
o Fixed incorrect tag in Section 6
o Clarified background and explanation in Section 2
o Clarified text in Section 3
o Expanded text in Section 5
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8.2. Changes from -01 to -02
o Fixed bug in .xml file
8.3. Changes from -02 to -03
o Reworded fallback text in Section 2
8.4. Changes from -03 to -04
o Fixed some references to [RFC4848] that should be to [RFC5222] in
sections Section 2 and Section 3
o Added clarifying text in Abstract
o Copied text from Abstract to Section 1
o Added clarifying text in Section 2
8.5. Changes from -04 to -05
o Added reference to [RFC5222] in Section 5
o Added clarifying text to Section 2
o Moved some text from Section 2 to Section 3
o Added new section Section 4
8.6. Changes from -05 to -06
o Changed intended status from Informational to Standards Track
o Added indication that the document (if approved) updates RFC 5222
o Added text to Abstract, Document Scope (Section 1), and
Introduction (Section 2) to better explain document purpose.
o Added Informational reference to [RFC5582]
o Minor wording improvements in multiple sections
8.7. Changes from -06 to -07
o Minor editorial changes to Introduction (Section 2)
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8.8. Changes from -07 to -08
o Added text in Abstract and Document Scope (Section 1) clarifying
the updates to [RFC5582]
8.9. Changes from -08 to -09
o Added text in Security Considerations (Section 5) making the use
of DNS Security [RFC4033] a SHOULD
9. References
9.1. Normative References
[RFC3958] Daigle, L. and A. Newton, "Domain-Based Application
Service Location Using SRV RRs and the Dynamic Delegation
Discovery Service (DDDS)", RFC 3958, DOI 10.17487/RFC3958,
January 2005, <https://www.rfc-editor.org/info/rfc3958>.
[RFC4033] Arends, R., Austein, R., Larson, M., Massey, D., and S.
Rose, "DNS Security Introduction and Requirements",
RFC 4033, DOI 10.17487/RFC4033, March 2005,
<https://www.rfc-editor.org/info/rfc4033>.
[RFC4848] Daigle, L., "Domain-Based Application Service Location
Using URIs and the Dynamic Delegation Discovery Service
(DDDS)", RFC 4848, DOI 10.17487/RFC4848, April 2007,
<https://www.rfc-editor.org/info/rfc4848>.
[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,
<https://www.rfc-editor.org/info/rfc5222>.
9.2. Informative references
[NENA-i3] National Emergency Number Association (NENA)
Interconnection and Security Committee, i3 Architecture
Working Group, , "Detailed Functional and Interface
Standards for the NENA i3 Solution", 2016,
<https://www.nena.org/page/i3_Stage3>.
[RFC5582] Schulzrinne, H., "Location-to-URL Mapping Architecture and
Framework", RFC 5582, DOI 10.17487/RFC5582, September
2009, <https://www.rfc-editor.org/info/rfc5582>.
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Authors' Addresses
Randall Gellens
Core Technology Consulting
US
Email: rg+ietf@coretechnologyconsulting.com
URI: http://www.coretechnologyconsulting.com
Brian Rosen
470 Conrad Dr
Mars, PA 16046
US
Email: br@brianrosen.net
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