Internet DRAFT - draft-ietf-alto-cost-mode
draft-ietf-alto-cost-mode
alto M. Boucadair
Internet-Draft Orange
Updates: 7285 (if approved) Q. Wu
Intended status: Standards Track Huawei
Expires: 4 December 2022 2 June 2022
A Cost Mode Registry for the Application-Layer Traffic Optimization
(ALTO) Protocol
draft-ietf-alto-cost-mode-05
Abstract
This document creates a new IANA registry for tracking cost modes
supported by the Application-Layer Traffic Optimization (ALTO)
Protocol. Also, this document relaxes a constraint that was imposed
by the ALTO specification on allowed cost mode values.
This document updates RFC 7285.
Editorial Note (To be removed by RFC Editor)
Please update RFC XXXX statements within the document with the RFC
number to be assigned to this document.
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 4 December 2022.
Copyright Notice
Copyright (c) 2022 IETF Trust and the persons identified as the
document authors. All rights reserved.
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Provisions Relating to IETF Documents (https://trustee.ietf.org/
license-info) in effect on the date of publication of this document.
Please review these documents carefully, as they describe your rights
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Updates to RFC7285 . . . . . . . . . . . . . . . . . . . . . 3
3.1. Updates to Section 6.1.2 of RFC7285 . . . . . . . . . . . 3
3.2. Updates to Section 10.5 of RFC7285 . . . . . . . . . . . 4
4. Backward Compatibility Considerations . . . . . . . . . . . . 5
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5
6. Security Considerations . . . . . . . . . . . . . . . . . . . 6
7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 6
8. References . . . . . . . . . . . . . . . . . . . . . . . . . 6
8.1. Normative References . . . . . . . . . . . . . . . . . . 6
8.2. Informative References . . . . . . . . . . . . . . . . . 7
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 7
1. Introduction
The cost mode attribute indicates how costs should be interpreted
when communicated in the Application-Layer Traffic Optimization
(ALTO) Protocol [RFC7285]. The base ALTO specification includes a
provision for only two modes:
"numerical": Indicates that numerical operations can be performed
(e.g., normalization) on the returned costs (Section 6.1.2.1 of
[RFC7285]).
"ordinal": Indicates that the cost values in a cost map represent
ranking (relative to all other values in a cost map), not actual
costs (Section 6.1.2.2 of [RFC7285]).
Additional cost modes are required for specific ALTO deployment cases
(e.g., [I-D.ietf-alto-path-vector]). In order to allow for such use
cases, this document relaxes the constraint imposed by the base ALTO
specification on allowed cost modes (Section 3) and creates a new
ALTO registry to track new cost modes (Section 5).
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The mechanisms defined in [RFC7285] are used to advertise the support
of new cost modes for specific cost metrics. Refer to Section 4 for
more details.
2. Terminology
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in BCP
14 [RFC2119][RFC8174] when, and only when, they appear in all
capitals, as shown here.
This document makes use of the terms defined in [RFC7285].
3. Updates to RFC7285
3.1. Updates to Section 6.1.2 of RFC7285
This document updates Section 6.1.2 of [RFC7285] as follows:
OLD:
The cost mode attribute indicates how costs should be interpreted.
Specifically, the cost mode attribute indicates whether returned
costs should be interpreted as numerical values or ordinal
rankings.
It is important to communicate such information to ALTO clients,
as certain operations may not be valid on certain costs returned
by an ALTO server. For example, it is possible for an ALTO server
to return a set of IP addresses with costs indicating a ranking of
the IP addresses. Arithmetic operations that would make sense for
numerical values, do not make sense for ordinal rankings. ALTO
clients may handle such costs differently.
Cost modes are indicated in protocol messages as strings.
NEW:
The cost mode attribute indicates how costs should be interpreted.
Two cost modes (numerical values and ordinal rankings) are
defined, but additional cost modes can be defined in the future.
It is important to communicate such information to ALTO clients,
as certain operations may not be valid on certain costs returned
by an ALTO server. For example, it is possible for an ALTO server
to return a set of IP addresses with costs indicating a ranking of
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the IP addresses. Arithmetic operations that would make sense for
numerical values, do not make sense for ordinal rankings. ALTO
clients may handle such costs differently.
Cost modes are indicated in protocol messages as strings.
Future documents that define a new cost mode are strongly
recommended to indicate whether that new cost mode applies to all
or a subset of cost metrics. This recommendation is meant to
prevent non-deterministic behaviors that may result in presenting
a cost mode with a specific metric, while such an association does
not make sense or can't be unambiguously interpreted by ALTO
implementations.
If the definition of a cost mode does not indicate whether that
cost mode applies to a subset of cost metrics, ALTO
implementations MUST be prepared to accept that cost mode for any
cost metric.
3.2. Updates to Section 10.5 of RFC7285
This document updates Section 10.5 of [RFC7285] as follows:
OLD:
A cost mode is encoded as a string. The string MUST have a value
of either "numerical" or "ordinal".
NEW:
A cost mode is encoded as a string. The string MUST be no more
than 32 characters, and it MUST NOT contain characters other than
US-ASCII alphanumeric characters (U+0030-U+0039, U+0041-U+005A,
and U+0061-U+007A), the hyphen-minus ('-', U+002D), the colon
(':', U+003A), or the low line ('_', U+005F). Cost modes reserved
for Private Use are prefixed with "priv:" (Section 5). Otherwise,
the cost mode MUST have a value that is listed in the registry
created in Section 5 of RFCXXXX.
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4. Backward Compatibility Considerations
ALTO servers that support new cost modes for specific cost metrics
will use the mechanism specified in Section 9.2 of [RFC7285] to
advertise their capabilities. ALTO clients (including legacy) will
use that information to specify cost constraints in their requests
(e.g., indicate a cost metric and a cost mode). An example of such a
behavior is depicted in Section 9.2.3 of [RFC7285].
If an ALTO client includes a cost mode that is not supported by an
ALTO server, the server indicates such an error with the error code
E_INVALID_FIELD_VALUE as per Section 8.5.2 of [RFC7285]. In
practice, legacy ALTO servers will reply with the error code
E_INVALID_FIELD_VALUE to requests that include a cost type other than
"numerical" or "ordinal" for the "routingcost" cost metric.
The encoding constraints in Section 3.2 do not introduce any
interoperability issue given that currently implemented cost modes
adhere to these constrains (mainly, those in [RFC7285] and
[I-D.ietf-alto-path-vector]).
5. IANA Considerations
This document requests IANA to create a new subregistry entitled
"ALTO Cost Modes" under the "Application-Layer Traffic Optimization
(ALTO) Protocol" registry available at [ALTO].
The assignment policy for this subregistry is "IETF Review"
(Section 4.8 of [RFC8126]).
Requests to register a new ALTO cost mode must include the following
information:
Identifier: The name of the ALTO cost mode. Refer to Section 3.2
for more details on allowed encoding.
Description: A short description of the requested ALTO cost mode.
Intended Semantics: A reference to where the semantic of the
requested cost mode is defined.
Reference: A reference to the document that registers the requested
cost mode.
Cost modes prefixed with "priv:" are reserved for Private Use
(Section 4.1 of [RFC8126]). This document requests IANA to add the
following note to the new subregistry:
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Note: Identifiers prefixed with 'priv:' are reserved for Private Use
(see [RFCXXXX], Section 5).
The subregistry is initially populated with the following values:
+============+=============================+============+===========+
| Identifier | Description | Intended | Reference |
| | | Semantics | |
+============+=============================+============+===========+
| numerical | Indicates that numerical | Section | RFCXXXX |
| | operations can be performed | 6.1.2.1 of | |
| | on the returned costs | RFC7285 | |
+------------+-----------------------------+------------+-----------+
| ordinal | Indicates that the cost | Section | RFCXXXX |
| | values in a cost map | 6.1.2.2 of | |
| | represent ranking | RFC7285 | |
+------------+-----------------------------+------------+-----------+
6. Security Considerations
This document does not introduce new concerns other than those
already discussed in Section 15 of [RFC7285].
7. Acknowledgements
Many thanks to Benjamin Kaduk for spotting the issue during the
review of [I-D.ietf-alto-path-vector].
Thanks to Adrian Farrel, Dhruv Dhody, Luis Miguel Contreras Murillo,
Sabine Randriamasy, and Qiao Xiang for the review and comments.
Special thanks to Kai Gao for Shepherding the document.
Thanks to Martin Duke for the AD review.
Thanks to Roni Even for the gen-art review, Jaime Jimenez for the
artart review, and Stephen Farrell for the secdir review.
Thanks to Robert Wilton, Lars Eggert, Francesca Palombini, Roman
Danyliw, Paul Wouters, and Murray Kucherawy for the IESG review.
8. References
8.1. Normative References
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[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.
[RFC7285] Alimi, R., Ed., Penno, R., Ed., Yang, Y., Ed., Kiesel, S.,
Previdi, S., Roome, W., Shalunov, S., and R. Woundy,
"Application-Layer Traffic Optimization (ALTO) Protocol",
RFC 7285, DOI 10.17487/RFC7285, September 2014,
<https://www.rfc-editor.org/info/rfc7285>.
[RFC8126] Cotton, M., Leiba, B., and T. Narten, "Guidelines for
Writing an IANA Considerations Section in RFCs", BCP 26,
RFC 8126, DOI 10.17487/RFC8126, June 2017,
<https://www.rfc-editor.org/info/rfc8126>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>.
8.2. Informative References
[ALTO] "Application-Layer Traffic Optimization (ALTO) Protocol",
2 March 2022, <https://www.iana.org/assignments/alto-
protocol/alto-protocol.xhtml>.
[I-D.ietf-alto-path-vector]
Gao, K., Lee, Y., Randriamasy, S., Yang, Y. R., and J. J.
Zhang, "An ALTO Extension: Path Vector", Work in Progress,
Internet-Draft, draft-ietf-alto-path-vector-25, 20 March
2022, <https://www.ietf.org/archive/id/draft-ietf-alto-
path-vector-25.txt>.
Authors' Addresses
Mohamed Boucadair
Orange
35000 Rennes
France
Email: mohamed.boucadair@orange.com
Qin Wu
Huawei
101 Software Avenue, Yuhua District
Nanjing
Jiangsu, 210012
China
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Email: bill.wu@huawei.com
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