Ethernet Availability TE: Ethernet Traffic Parameters with Availability Information

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.

Copyright Notice

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

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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

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
   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.

   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
   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.

   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.

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>.

   [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>.

   [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>.

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
   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%

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