    Internet Engineering Task Force (IETF)                           H. Long
    Request for Comments: 8625                                    M. Ye, Ed.
    Category: Standards Track                  Huawei Technologies Co., Ltd.
    ISSN: 2070-1721                                           G. Mirsky, Ed.
                                                                         ZTE
                                                             A. D'Alessandro
                                                        Telecom Italia S.p.A
                                                                     H. Shah
                                                                       Ciena
                                                                 August 2019

           Ethernet Traffic Parameters with Availability Information

    Abstract

       A packet-switching network may contain links with variable bandwidths
       (e.g., copper and radio).  The bandwidth of such links is sensitive
       to the external environment (e.g., climate).  Availability is
       typically used to describe these links when doing network planning.
       This document introduces an optional Bandwidth Availability TLV in
       RSVP-TE signaling.  This extension can be used to set up a GMPLS
       Label Switched Path (LSP) in conjunction with the Ethernet
       SENDER_TSPEC object.

    Status of This Memo

       This is an Internet Standards Track document.

       This document is a product of the Internet Engineering Task Force
       (IETF).  It represents the consensus of the IETF community.  It has
       received public review and has been approved for publication by the
       Internet Engineering Steering Group (IESG).  Further information on
       Internet Standards is available in Section 2 of RFC 7841.

       Information about the current status of this document, any errata,
       and how to provide feedback on it may be obtained at
       https://www.rfc-editor.org/info/rfc8625.

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    Copyright Notice

       Copyright (c) 2019 IETF Trust and the persons identified as the
       document authors.  All rights reserved.

       This document is subject to BCP 78 and the IETF Trust's Legal
       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 and restrictions with respect
       to this document.  Code Components extracted from this document must
       include Simplified BSD License text as described in Section 4.e of
       the Trust Legal Provisions and are provided without warranty as
       described in the Simplified BSD License.

    Table of Contents

       1. Introduction ....................................................3
          1.1. Conventions Used in This Document ..........................4
       2. Overview ........................................................4
       3. Extension to RSVP-TE Signaling ..................................5
          3.1. Bandwidth Availability TLV .................................5
          3.2. Signaling Process ..........................................6
       4. Security Considerations .........................................7
       5. IANA Considerations .............................................8
       6. References ......................................................8
          6.1. Normative References .......................................8
          6.2. Informative References .....................................9
       Appendix A.  Bandwidth Availability Example .......................11
       Acknowledgments ...................................................13
       Authors' Addresses ................................................13

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    1.  Introduction

       The RSVP-TE specification [RFC3209] and GMPLS extensions [RFC3473]
       specify the signaling message, including the bandwidth request for
       setting up an LSP in a packet-switching network.

       Some data communication technologies allow a seamless change of the
       maximum physical bandwidth through a set of known discrete values.
       The parameter availability [G.827] [F.1703] [P.530] is often used to
       describe the link capacity during network planning.  The availability
       is based on a time scale, which is a proportion of the operating time
       that the requested bandwidth is ensured.  A more detailed example of
       bandwidth availability can be found in Appendix A.  Assigning
       different bandwidth availability classes to different types of
       services over links with variable discrete bandwidth provides for a
       more efficient planning of link capacity.  To set up an LSP across
       these links, bandwidth availability information is required for the
       nodes to verify bandwidth satisfaction and make a bandwidth
       reservation.  The bandwidth availability information should be
       inherited from the bandwidth availability requirements of the
       services expected to be carried on the LSP.  For example, voice
       service usually needs 99.999% bandwidth availability, while non-real-
       time services may adequately perform at 99.99% or 99.9% bandwidth
       availability.  Since different service types may need different
       availability guarantees, multiple <availability, bandwidth> pairs may
       be required when signaling.

       If the bandwidth availability requirement is not specified in the
       signaling message, the bandwidth will likely be reserved as the
       highest bandwidth availability.  Suppose, for example, the bandwidth
       with 99.999% availability of a link is 100 Mbps, and the bandwidth
       with 99.99% availability is 200 Mbps.  When a video application makes
       a request for 120 Mbps without a bandwidth availability requirement,
       the system will consider the request as 120 Mbps with 99.999%
       bandwidth availability, while the available bandwidth with 99.999%
       bandwidth availability is only 100 Mbps.  Therefore, the LSP path
       cannot be set up.  However, the video application doesn't need
       99.999% bandwidth availability; 99.99% bandwidth availability is
       enough.  In this case, the LSP could be set up if the bandwidth
       availability is also specified in the signaling message.

       To fulfill an LSP setup by signaling in these scenarios, this
       document specifies a Bandwidth Availability TLV.  The Bandwidth
       Availability TLV can be applicable to any kind of physical link with
       variable discrete bandwidth, such as microwave or DSL.  Multiple
       Bandwidth Availability TLVs, together with multiple Ethernet

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       Bandwidth Profile TLVs, can be carried by the Ethernet SENDER_TSPEC
       object [RFC6003].  Since the Ethernet FLOWSPEC object has the same
       format as the Ethernet SENDER_TSPEC object [RFC6003], the Bandwidth
       Availability TLV can also be carried by the Ethernet FLOWSPEC object.

    1.1.  Conventions Used in This Document

       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.

       The following acronyms are used in this document:

       RSVP-TE  Resource Reservation Protocol - Traffic Engineering

       LSP      Label Switched Path

       SNR      Signal-to-Noise Ratio

       TLV      Type-Length-Value

       LSA      Link State Advertisement

       QAM      Quadrature Amplitude Modulation

       QPSK     Quadrature Phase Shift Keying

    2.  Overview

       A tunnel in a packet-switching network may span one or more links in
       a network.  To set up an LSP, a node may collect link information
       that is advertised in a routing message (e.g., an OSPF TE LSA
       message) by network nodes to obtain network topology information, and
       it can then calculate an LSP route based on the network topology.
       The calculated LSP route is signaled using a PATH/RESV message to set
       up the LSP.

       If a network contains one or more links with variable discrete
       bandwidths, a <bandwidth, availability> requirement list should be
       specified for an LSP at setup.  Each <bandwidth, availability> pair
       in the list means the listed bandwidth with specified availability is
       required.  The list can be derived from the results of service
       planning for the LSP.

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       A node that has link(s) with variable discrete bandwidth attached
       should contain a <bandwidth, availability> information list in its
       OSPF TE LSA messages.  The list provides the mapping between the link
       nominal bandwidth and its availability level.  This information can
       then be used for path calculation by the node(s).  The routing
       extension for availability can be found in [RFC8330].

       When a node initiates a PATH/RESV signaling to set up an LSP, the
       PATH message should carry the <bandwidth, availability> requirement
       list as a bandwidth request.  Intermediate node(s) will allocate the
       bandwidth resources for each availability requirement from the
       remaining bandwidth with the corresponding availability.  An error
       message may be returned if any <bandwidth, availability> request
       cannot be satisfied.

    3.  Extension to RSVP-TE Signaling

    3.1.  Bandwidth Availability TLV

       A Bandwidth Availability TLV is defined as a TLV of the Ethernet
       SENDER_TSPEC object [RFC6003] in this document.  The Ethernet
       SENDER_TSPEC object MAY include more than one Bandwidth Availability
       TLV.  The Bandwidth Availability TLV has the following format:

           0                   1                   2                   3
           0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
          +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
          |               Type            |              Length           |
          +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
          |    Index      |                 Reserved                      |
          +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
          |                         Availability                          |
          +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                       Figure 1: Bandwidth Availability TLV

       Type (2 octets): 4

       Length (2 octets): 0x0C.  Indicates the length in bytes of the whole
       TLV, including the Type and Length fields.  In this case, the length
       is 12 bytes.

       Index (1 octet): When the Bandwidth Availability TLV is included, the
       Ethernet Bandwidth Profile TLV MUST also be included.  If there are
       multiple bandwidth requirements present (in multiple Ethernet
       Bandwidth Profile TLVs) and they have different availability
       requirements, multiple Bandwidth Availability TLVs MUST be carried.
       In such a case, the Bandwidth Availability TLV has a one-to-one

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       correspondence with the Ethernet Bandwidth Profile TLV as both have
       the same value in the Index field.  If all the bandwidth requirements
       in the Ethernet Bandwidth Profile TLV have the same availability
       requirement, one Bandwidth Availability TLV SHOULD be carried.  In
       this case, the Index field is set to 0.

       Reserved (3 octets): These bits SHOULD be set to zero when sent and
       MUST be ignored when received.

       Availability (4 octets): A 32-bit floating-point number in binary
       interchange format [IEEE754] describes the decimal value of the
       availability requirement for this bandwidth request.  The value MUST
       be less than 1 and is usually expressed as one of the following
       values: 0.99, 0.999, 0.9999, or 0.99999.  The IEEE floating-point
       number is used here to align with [RFC8330].  When representing
       values higher than 0.999999, the floating-point number starts to
       introduce errors to intended precision.  However, in reality, 0.99999
       is normally considered the highest availability value (which results
       in 5 minutes of outage in a year) in a telecom network.  Therefore,
       the use of a floating-point number for availability is acceptable.

    3.2.  Signaling Process

       The source node initiates a PATH message, which may carry a number of
       bandwidth requests, including one or more Ethernet Bandwidth Profile
       TLVs and one or more Bandwidth Availability TLVs.  Each Ethernet
       Bandwidth Profile TLV corresponds to an availability parameter in the
       associated Bandwidth Availability TLV.

       When the intermediate and destination nodes receive the PATH message,
       the nodes compare the requested bandwidth under each availability
       level in the SENDER_TSPEC objects, with the remaining link bandwidth
       resources under a corresponding availability level on a local link,
       to check if they can meet the bandwidth requirements.

       o  When all <bandwidth, availability> requirement requests can be
          satisfied (that is, the requested bandwidth under each
          availability parameter is smaller than or equal to the remaining
          bandwidth under the corresponding availability parameter on its
          local link), the node SHOULD reserve the bandwidth resources from
          each remaining sub-bandwidth portion on its local link to set up
          this LSP.  Optionally, a higher availability bandwidth can be
          allocated to a lower availability request when the lower
          availability bandwidth cannot satisfy the request.

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       o  When at least one <bandwidth, availability> requirement request
          cannot be satisfied, the node SHOULD generate a PathErr message
          with the error code "Admission Control Error" and the error value
          "Requested Bandwidth Unavailable" (see [RFC2205]).

       When two LSPs request bandwidth with the same availability
       requirement, the contention MUST be resolved by comparing the node
       IDs, where the LSP with the higher node ID is assigned the
       reservation.  This is consistent with the general contention
       resolution mechanism provided in Section 4.2 of [RFC3471].

       When a node does not support the Bandwidth Availability TLV, the node
       should send a PathErr message with error code "Unknown Attributes
       TLV", as specified in [RFC5420].  An LSP could also be set up in this
       case if there's enough bandwidth (note that the availability level of
       the reserved bandwidth is unknown).  When a node receives Bandwidth
       Availability TLVs with a mix of zero and non-zero indexes, the
       message MUST be ignored and MUST NOT be propagated.  When a node
       receives Bandwidth Availability TLVs (non-zero index) with no
       matching index value among the Ethernet Bandwidth Profile TLVs, the
       message MUST be ignored and MUST NOT be propagated.  When a node
       receives several <bandwidth, availability> pairs, but there are extra
       Ethernet Bandwidth Profile TLVs that do not match the index of any
       Bandwidth Availability TLV, the extra Ethernet Bandwidth Profile TLVs
       MUST be ignored and MUST NOT be propagated.

    4.  Security Considerations

       This document defines a Bandwidth Availability TLV in RSVP-TE
       signaling used in GMPLS networks.  [RFC3945] notes that
       authentication in GMPLS systems may use the authentication mechanisms
       of the component protocols.  [RFC5920] provides an overview of
       security vulnerabilities and protection mechanisms for the GMPLS
       control plane.  In particular, Section 7.1.2 of [RFC5920] discusses
       the control-plane protection with RSVP-TE by using general RSVP
       security tools, limiting the impact of an attack on control-plane
       resources, and using authentication for RSVP messages.  Moreover, the
       GMPLS network is often considered to be a closed network such that
       insertion, modification, or inspection of packets by an outside party
       is not possible.

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    5.  IANA Considerations

       IANA maintains a registry of GMPLS parameters called the "Generalized
       Multi-Protocol Label Switching (GMPLS) Signaling Parameters"
       registry.  This registry includes the "Ethernet Sender TSpec TLVs/
       Ethernet Flowspec TLVs" subregistry that contains the TLV type values
       for TLVs carried in the Ethernet SENDER_TSPEC object.  This
       subregistry has been updated to include the Bandwidth Availability
       TLV:

          Type             Description                 Reference
          ----             ----------------------      ---------
           4               Bandwidth Availability      RFC 8625

    6.  References

    6.1.  Normative References

       [IEEE754]  IEEE, "IEEE Standard for Floating-Point Arithmetic",
                  IEEE 754, DOI 10.1109/IEEESTD.2008.4610935.

       [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>.

       [RFC2205]  Braden, R., Ed., Zhang, L., Berson, S., Herzog, S., and S.
                  Jamin, "Resource ReSerVation Protocol (RSVP) -- Version 1
                  Functional Specification", RFC 2205, DOI 10.17487/RFC2205,
                  September 1997, <https://www.rfc-editor.org/info/rfc2205>.

       [RFC3209]  Awduche, D., Berger, L., Gan, D., Li, T., Srinivasan, V.,
                  and G. Swallow, "RSVP-TE: Extensions to RSVP for LSP
                  Tunnels", RFC 3209, DOI 10.17487/RFC3209, December 2001,
                  <https://www.rfc-editor.org/info/rfc3209>.

       [RFC3471]  Berger, L., Ed., "Generalized Multi-Protocol Label
                  Switching (GMPLS) Signaling Functional Description",
                  RFC 3471, DOI 10.17487/RFC3471, January 2003,
                  <https://www.rfc-editor.org/info/rfc3471>.

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       [RFC3473]  Berger, L., Ed., "Generalized Multi-Protocol Label
                  Switching (GMPLS) Signaling Resource ReserVation Protocol-
                  Traffic Engineering (RSVP-TE) Extensions", RFC 3473,
                  DOI 10.17487/RFC3473, January 2003,
                  <https://www.rfc-editor.org/info/rfc3473>.

       [RFC5420]  Farrel, A., Ed., Papadimitriou, D., Vasseur, JP., and A.
                  Ayyangarps, "Encoding of Attributes for MPLS LSP
                  Establishment Using Resource Reservation Protocol Traffic
                  Engineering (RSVP-TE)", RFC 5420, DOI 10.17487/RFC5420,
                  February 2009, <https://www.rfc-editor.org/info/rfc5420>.

       [RFC6003]  Papadimitriou, D., "Ethernet Traffic Parameters",
                  RFC 6003, DOI 10.17487/RFC6003, October 2010,
                  <https://www.rfc-editor.org/info/rfc6003>.

       [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>.

    6.2.  Informative References

       [EN-302-217]
                  ETSI, "Fixed Radio Systems; Characteristics and
                  requirements for point-to-point equipment and antennas;
                  Part 1: Overview and system-independent common
                  characteristics", ETSI EN 302 217-1, Version 3.1.1, May
                  2017.

       [F.1703]   ITU-R, "Availability objectives for real digital fixed
                  wireless links used in 27 500 km hypothetical reference
                  paths and connections", ITU-R Recommendation F.1703-0,
                  January 2005, <https://www.itu.int/rec/R-REC-F.1703/en>.

       [G.827]    ITU-T, "Availability performance parameters and objectives
                  for end-to-end international constant bit-rate digital
                  paths", ITU-T Recommendation G.827, September 2003,
                  <https://www.itu.int/rec/T-REC-G.827/en>.

       [P.530]    ITU-R, "Propagation data and prediction methods required
                  for the design of terrestrial line-of-sight systems",
                  ITU-R Recommendation P.530-17, December 2017,
                  <https://www.itu.int/rec/R-REC-P.530/en>.

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       [RFC3945]  Mannie, E., Ed., "Generalized Multi-Protocol Label
                  Switching (GMPLS) Architecture", RFC 3945,
                  DOI 10.17487/RFC3945, October 2004,
                  <https://www.rfc-editor.org/info/rfc3945>.

       [RFC5920]  Fang, L., Ed., "Security Framework for MPLS and GMPLS
                  Networks", RFC 5920, DOI 10.17487/RFC5920, July 2010,
                  <https://www.rfc-editor.org/info/rfc5920>.

       [RFC8330]  Long, H., Ye, M., Mirsky, G., D'Alessandro, A., and H.
                  Shah, "OSPF Traffic Engineering (OSPF-TE) Link
                  Availability Extension for Links with Variable Discrete
                  Bandwidth", RFC 8330, DOI 10.17487/RFC8330, February 2018,
                  <https://www.rfc-editor.org/info/rfc8330>.

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    Appendix A.  Bandwidth Availability Example

       In mobile backhaul networks, microwave links are very popular for
       providing connections of last hops.  To maintain link connectivity in
       heavy rain conditions, the microwave link may lower the modulation
       level since moving to a lower modulation level provides for a lower
       SNR requirement.  This is called "adaptive modulation" technology
       [EN-302-217].  However, a lower modulation level also means a lower
       link bandwidth.  When a link bandwidth is reduced because of
       modulation downshifting, high-priority traffic can be maintained,
       while lower-priority traffic is dropped.  Similarly, copper links may
       change their link bandwidth due to external interference.

       Presume that a link has three discrete bandwidth levels:

       o  The link bandwidth under modulation level 1 (e.g., QPSK) is 100
          Mbps.

       o  The link bandwidth under modulation level 2 (e.g., 16QAM) is 200
          Mbps.

       o  The link bandwidth under modulation level 3 (e.g., 256QAM) is 400
          Mbps.

       On a sunny day, modulation level 3 can be used to achieve a 400 Mbps
       link bandwidth.

       Light rain with a X mm/h rate triggers the system to change the
       modulation level from level 3 to level 2, with the bandwidth changing
       from 400 Mbps to 200 Mbps.  The probability of X mm/h rain in the
       local area is 52 minutes in a year.  Then the dropped 200 Mbps
       bandwidth has 99.99% availability.

       Heavy rain with a Y(Y>X) mm/h rate triggers the system to change the
       modulation level from level 2 to level 1, with the bandwidth changing
       from 200 Mbps to 100 Mbps.  The probability of Y mm/h rain in the
       local area is 26 minutes in a year.  Then the dropped 100 Mbps
       bandwidth has 99.995% availability.

       For the 100 Mbps bandwidth of modulation level 1, only extreme
       weather conditions can cause the whole system to be unavailable,
       which only happens for 5 minutes in a year.  So the 100 Mbps
       bandwidth of the modulation level 1 owns the availability of 99.999%.

       There are discrete buckets per availability level.  Under the worst
       weather conditions, there's only 100 Mbps capacity, which is 99.999%
       available.  It's treated effectively as "always available" since
       better availability is not possible.  If the weather is bad but not

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       the worst possible conditions, modulation level 2 can be used, which
       gets an additional 100 Mbps bandwidth (i.e., 200 Mbps total).
       Therefore, 100 Mbps is in the 99.999% bucket, and 100 Mbps is in the
       99.995% bucket.  In clear weather, modulation level 3 can be used to
       get 400 Mbps total, but that's only 200 Mbps more than at modulation
       level 2, so the 99.99% bucket has that "extra" 200 Mbps, and the
       other two buckets still have 100 Mbps each.

       Therefore, the maximum bandwidth is 400 Mbps.  The sub-bandwidth and
       its availability according to the weather conditions are shown as
       follows:

          Sub-bandwidth (Mbps)   Availability
          ------------------     ------------

          200                    99.99%

          100                    99.995%

          100                    99.999%

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    Acknowledgments

       The authors would like to thank Deborah Brungard, Khuzema Pithewan,
       Lou Berger, Yuji Tochio, Dieter Beller, and Autumn Liu for their
       comments on and contributions to the document.

    Authors' Addresses

       Hao Long
       Huawei Technologies Co., Ltd.
       No.1899, Xiyuan Avenue, Hi-tech Western District
       Chengdu 611731
       China

       Phone: +86-18615778750
       Email: longhao@huawei.com

       Min Ye (editor)
       Huawei Technologies Co., Ltd.
       No.1899, Xiyuan Avenue, Hi-tech Western District
       Chengdu 611731
       China

       Email: amy.yemin@huawei.com

       Greg Mirsky (editor)
       ZTE

       Email: gregimirsky@gmail.com

       Alessandro D'Alessandro
       Telecom Italia S.p.A

       Email: alessandro.dalessandro@telecomitalia.it

       Himanshu Shah
       Ciena Corp.
       3939 North First Street
       San Jose, CA 95134
       United States of America

       Email: hshah@ciena.com

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