A Cost Mode Registry for the Application-Layer Traffic Optimization (ALTO) Protocol
draft-ietf-alto-cost-mode-00

alto                                                        M. Boucadair
Internet-Draft                                                    Orange
Updates: 7285 (if approved)                                        Q. Wu
Intended status: Standards Track                                  Huawei
Expires: 22 September 2022                                 21 March 2022

  A Cost Mode Registry for the Application-Layer Traffic Optimization
                            (ALTO) Protocol
                      draft-ietf-alto-cost-mode-00

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.

Status of This Memo

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   This Internet-Draft will expire on 22 September 2022.

Copyright Notice

   Copyright (c) 2022 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

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   This document is subject to BCP 78 and the IETF Trust's Legal
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   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.  Update to Section 6.1.2 of RFC7285  . . . . . . . . . . .   3
     3.2.  Update to Section 10.5 of RFC7285 . . . . . . . . . . . .   4
   4.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   4
   5.  Security Considerations . . . . . . . . . . . . . . . . . . .   5
   6.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   5
   7.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   5
     7.1.  Normative References  . . . . . . . . . . . . . . . . . .   5
     7.2.  Informative References  . . . . . . . . . . . . . . . . .   5
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   6

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 creates a new ALTO registry to track new cost
   mode values (Section 4) and relaxes the constraints imposed by the
   base ALTO specification on allowed cost mode values (Section 3).

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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.  Update 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.
   This document defines two cost modes (numerical values or ordinal
   rankings), 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 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.

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   Future documents that define a new cost mode SHOULD indicate whether
   that new cost mode applies to all or a subset of cost metrics.

3.2.  Update 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 ('-', U+002D), the colon (':', U+003A), or
   the low line ('_', +005F).  Cost modes reserved for Private Use are
   prefixed with "priv:" (Section 4).  Otherwise, the cost mode MUST
   have a value that is listed in the registry created in Section 4 of
   RFCXXXX.

   *  Note to the RFC Editor: Please replace RFCXXXX with the RFC number
      to be assigned to this document.

4.  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 registry is initially populated with the following values:

   +===========+=============================+=================+
   | Cost Mode | Description                 | Specification   |
   +===========+=============================+=================+
   | numerical | Indicates that numerical    | Section 6.1.2.1 |
   |           | operations can be performed |  of RFC7285     |
   |           | on the returned costs       |                 |
   +-----------+-----------------------------+-----------------+
   | ordinal   | Indicates that the cost     | Section 6.1.2.2 |
   |           | values in a cost map        |  of RFC7285     |
   |           | represent ranking           |                 |
   +-----------+-----------------------------+-----------------+

   The assignment policy for this registry is "IETF Review" (Section 4.8
   of [RFC8126]).

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   Cost modes prefixed with "priv:" are reserved for Private Use
   (Section 4.1 of [RFC8126]).

5.  Security Considerations

   This document does not introduce new concerns other than those
   already discussed in Section 15 of [RFC7285].

6.  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,
   and Sabine Randriamasy for the review and comments.

   Special thanks to Kai Gao for Shepherding the document.

7.  References

7.1.  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,
              <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>.

   [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>.

7.2.  Informative References

   [ALTO]     "Application-Layer Traffic Optimization (ALTO) Protocol",
              2 March 2022, <https://www.iana.org/assignments/alto-
              protocol/alto-protocol.xhtml>.

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   [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>.

   [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>.

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
   Email: bill.wu@huawei.com

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