Network Working Group
Internet Engineering Task Force (IETF)                           H. Long, Long
Request for Comments: 8625                                    M. Ye
Internet Draft Ye, Ed.
Category: Standards Track                  Huawei Technologies Co., Ltd
Intended status: Standards Track Ltd.
ISSN: 2070-1721                                           G. Mirsky Mirsky, Ed.
                                                                     ZTE
                                                         A.D'Alessandro
                                                         A. D'Alessandro
                                                    Telecom Italia S.p.A
                                                                 H. Shah
                                                                   Ciena
Expires: November 2019                                      May 5,
                                                             August 2019

       Ethernet Traffic Parameters with Availability Information
           draft-ietf-ccamp-rsvp-te-bandwidth-availability-16.txt

Abstract

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

Status of this This Memo

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   provisions of BCP 78 and BCP 79.

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   Internet Engineering Steering Group (IESG).  Further information on
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   reference material or to cite them other than as "work available in progress."

   The list Section 2 of RFC 7841.

   Information about the current Internet-Drafts can be accessed at
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   This Internet-Draft will expire on November 5, 2019.
   https://www.rfc-editor.org/info/rfc8625.

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Table of Contents

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

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 draft:

   RSVP-TE  Resource Reservation Protocol-Traffic Engineering

   LSP      Label Switched Path
   SNR      Signal-to-noise Ratio

   TLV      Type Length Value

   LSA      Link State Advertisement ...................................................13
   Authors' Addresses ................................................13

1.  Introduction

   The RSVP-TE specification [RFC3209] and GMPLS extensions [RFC3473]
   specify the signaling message message, including the bandwidth request for
   setting up a Label Switched Path an LSP in a packet switching 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], [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 on the of
   bandwidth availability can be found in Appendix A.  Assigning
   different bandwidth availability classes to different types of
   services over such kind of 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 "five nines" 99.999% bandwidth availability, while
   non-real non-real-
   time services may adequately perform at four 99.99% or three nines 99.9% bandwidth
   availability.  Since different service types may need different availabilities
   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; 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 Mbps.  Therefore, the LSP path
   cannot be set up. But, in fact,  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 links link with
   variable discrete bandwidth, such as microwave or DSL.  Multiple
   Bandwidth Availability TLVs TLVs, together with multiple Ethernet
   Bandwidth Profiles 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 packet-switching network may span one or more links in
   a network.  To setup a Label Switched Path (LSP), set up an LSP, a node may collect link information which
   that is advertised in a routing message, e.g., message (e.g., an OSPF TE LSA message,
   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 for setting to set
   up the LSP.

   In case that there is (are) link(s)

   If a network contains one or more links with variable discrete bandwidth
   in a network,
   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 could can be derived from the results of service
   planning for the LSP.

   A node which 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 resource 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): 0x04(suggested; TBD by IANA) 4

   Length (2 octets): 0x0C.  Indicates the length in bytes of the whole TLV
   TLV, including the Type and Length fields, in fields.  In this case 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 one-to-one
   correspondence with the Ethernet Bandwidth Profile TLV by having as both have
   the same value of in the Index field.  If all the bandwidth requirements
   in the Ethernet Bandwidth Profile TLV have the same Availability 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 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 in the value as one of
      0.99/0.999/0.9999/0.99999. the following
   values: 0.99, 0.999, 0.9999, or 0.99999.  The IEEE floating-point
   number is used here to align with [RFC8330]. However when  When representing
   values higher than 0.999999, the floating-point number starts to
   introduce errors in relation to intended precision. However  However, in reality, 0.99999
   is normally considered as the highest availability value (5 (which results
   in 5 minutes of outage in a year) in a telecom
      network, therefore network.  Therefore,
   the use of a floating-point number in for availability is acceptable.

3.2.  Signaling Process

   The source node initiates a PATH message 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.

   The

   When the intermediate and destination nodes check whether they can
   satisfy receive the PATH message,
   the nodes compare the requested bandwidth requirements by comparing under each bandwidth
   request inside availability
   level in the SENDER_TSPEC objects objects, with the remaining link sub- bandwidth resource with respective
   resources under a corresponding availability guarantee level on the a local link when link,
   to check if they can meet the PATH message is received. bandwidth requirements.

   o  When all <bandwidth, availability> requirement requests can be
      satisfied (the (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 resource 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,
   with where the LSP with the higher node ID being is assigned the
   reservation.  This is consistent with the general contention
   resolution mechanism provided in section 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 (the (note that the availability level of
   the reserved bandwidth is unknown).  When a node receives Bandwidth
   Availability TLVs with a mix of zero index and non-zero
   index, 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 bandwidth-TLVs, 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 bandwidth-TLVs
   without matching
   Ethernet Bandwidth Profile TLVs that do not match the index of any Availability-TLV,
   Bandwidth Availability TLV, the extra
   bandwidth-TLVs 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. Especially section  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 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 registries and sub-registries for RSVP-TE used by
   GMPLS. IANA is requested to make allocations from these registries
   as set out in the following sections.

5.1 Ethernet Sender TSpec TLVs

   IANA maintains a registry of GMPLS parameters called the "Generalized
   Multi-Protocol Label Switching (GMPLS) Signaling Parameters".

   IANA has created a sub-registry called Parameters"
   registry.  This registry includes the "Ethernet Sender TSpec TLVs / TLVs/
   Ethernet Flowspec TLVs" to contain subregistry that contains the TLV type values
   for TLVs carried in the Ethernet SENDER_TSPEC object. The sub-registry needs
   to be  This
   subregistry has been updated to include the Bandwidth Availability TLV which is
   defined as follow. This document proposes a suggested value for the
   Availability sub-TLV; it is requested that the suggested value be
   granted by IANA.
   TLV:

      Type             Description                 Reference

   -----                    --------------------
      ----             ----------------------      ---------

   0x04
       4               Bandwidth Availability      [This ID]

   (Suggested; TBD by IANA)

   The registration procedure for this registry is Standards Action as
   defined in [RFC8126].      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, S.
              Jamin, "Resource ReSerVation Protocol (RSVP) - -- Version 1
              Functional Specification", RFC 2205, DOI 10.17487/RFC2205,
              September 1997. 1997, <https://www.rfc-editor.org/info/rfc2205>.

   [RFC3209]  Awduche, D., Berger, L., Gan, D., Li, T., Srinivasan,
             V.,and V.,
              and G. Swallow, "RSVP-TE: Extensions to RSVP for LSP
              Tunnels", RFC 3209, DOI 10.17487/RFC3209, December 2001.

   [RFC3473] 2001,
              <https://www.rfc-editor.org/info/rfc3209>.

   [RFC3471]  Berger, L., Ed., "Generalized Multi-Protocol Label
              Switching (GMPLS) Signaling Resource ReserVation Protocol-Traffic
             Engineering (RSVP-TE) Extensions", Functional Description",
              RFC 3473, 3471, DOI 10.17487/RFC3471, January 2003.

   [RFC3471] 2003,
              <https://www.rfc-editor.org/info/rfc3471>.

   [RFC3473]  Berger, L., Ed., "Generalized Multi-Protocol Label
              Switching (GMPLS) Signaling Functional Description", Resource ReserVation Protocol-
              Traffic Engineering (RSVP-TE) Extensions", RFC 3471, 3473,
              DOI 10.17487/RFC3473, January 2003. 2003,
              <https://www.rfc-editor.org/info/rfc3473>.

   [RFC5420]  Farrel, A., Ed., Papadimitriou, D., Vasseur Vasseur, JP., and Ayyangar
             A., 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. 2009, <https://www.rfc-editor.org/info/rfc5420>.

   [RFC6003]  Papadimitriou, D. D., "Ethernet Traffic Parameters",
              RFC 6003, DOI 10.17487/RFC6003, October 2010. 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, May 2017.

   [IEEE754]  IEEE, "IEEE Standard for Floating-Point Arithmetic",IEEE
             754-2008, DOI 10.1109/IEEESTD.2008.4610935, 2008,
             <http://standards.ieee.org/findstds/standard/754-
             2008.html>. 10.17487/RFC8174,
              May 2017, <https://www.rfc-editor.org/info/rfc8174>.

6.2.  Informative References

   [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
             Requirement Levels", RFC 2119, March 1997.

   [RFC8126] Cotton,M. and Leiba,B.,

   [EN-302-217]
              ETSI, "Fixed Radio Systems; Characteristics and Narten T., "Guidelines for
             Writing an IANA Considerations Section in RFCs", RFC 8126,
             June 2017.

   [RFC3945] Mannie, E., "Generalized Multi-Protocol Label Switching
             (GMPLS) Architecture", RFC 3945, October 2004.

   [RFC5920] Fang, L., "Security Framework
              requirements for MPLS point-to-point equipment and GMPLS
             Networks", RFC 5920, July 2010.

   [G.827]  ITU-T Recommendation, "Availability performance parameters antennas;
              Part 1: Overview and objectives for end-to-end international constant bit-
             rate digital paths", September 2003. system-independent common
              characteristics", ETSI EN 302 217-1, Version 3.1.1, May
              2017.

   [F.1703]  ITU-R Recommendation,   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. 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 Recommendation," Propagation    ITU-R, "Propagation data and prediction methods required
              for the design of terrestrial line-of-
             sight line-of-sight systems", February 2012

   [EN 302 217] ETSI standard, "Fixed Radio Systems; Characteristics
             and requirements
              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 point-to-point equipment MPLS and
             antennas", April 2009 GMPLS
              Networks", RFC 5920, DOI 10.17487/RFC5920, July 2010,
              <https://www.rfc-editor.org/info/rfc5920>.

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

7. Appendix: 2018,
              <https://www.rfc-editor.org/info/rfc8330>.

Appendix A.  Bandwidth Availability Example

   In a mobile backhaul network, networks, microwave links are very popular for
   providing connections of last hops. In case of  To maintain link connectivity in
   heavy rain conditions, to maintain the link connectivity, the microwave link may lower the modulation
   level since moving to a lower modulation level provides for a lower Signal-to-Noise Ratio (SNR)
   SNR requirement.  This is called adaptive modulation "adaptive modulation" technology [EN 302 217].
   [EN-302-217].  However, a lower modulation level also means a lower
   link bandwidth.  When a link bandwidth is reduced because of
   modulation down-shifting, high-
   priority 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.

   Presuming

   Presume that a link has three discrete bandwidth levels:

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

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

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

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

   A light

   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.

   A heavy

   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 100M 100 Mbps bandwidth of the modulation level 1, only the extreme
   weather condition 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 and that's capacity, which is 99.999%
   available.  It's treated as effectively as "always available" since there's no way to do any better.
   better availability is not possible.  If the weather is bad but not
   the worst weather, possible conditions, modulation level 2 can be used, which
   gets an additional 100 Mbps bandwidth (i.e., 200 Mbps total), so there are total).
   Therefore, 100 Mbps is in the 99.999% bucket bucket, and 100 Mbps is in the
   99.995% bucket.  In clear weather, modulate 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 their 100 Mbps each.

   Therefore, the maximum bandwidth is 400 Mbps. According to the
   weather condition, the  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%

8.

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 on to the document.

Authors' Addresses

   Hao Long
   Huawei Technologies Co., Ltd.
   No.1899, Xiyuan Avenue, Hi-tech Western District
   Chengdu 611731, P.R.China 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, P.R.China 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
   US
   United States of America

   Email: hshah@ciena.com