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Versions: (draft-previdi-isis-te-metric-extensions) 00 01 02 03 04 05 06 07 08 09 10 11 RFC 7810

Networking Working Group                                 S. Previdi, Ed.
Internet-Draft                                       Cisco Systems, Inc.
Intended status: Standards Track                            S. Giacalone
Expires: April 13, 2014                                  Thomson Reuters
                                                                 D. Ward
                                                     Cisco Systems, Inc.
                                                                J. Drake
                                                                A. Atlas
                                                        Juniper Networks
                                                             C. Filsfils
                                                     Cisco Systems, Inc.
                                                                   Q. Wu
                                                                  Huawei
                                                        October 10, 2013


            IS-IS Traffic Engineering (TE) Metric Extensions
                draft-ietf-isis-te-metric-extensions-01

Abstract

   In certain networks, such as, but not limited to, financial
   information networks (e.g. stock market data providers), network
   performance criteria (e.g. latency) are becoming as critical to data
   path selection as other metrics.

   This document describes extensions to IS-IS TE [RFC5305] such that
   network performance information can be distributed and collected in a
   scalable fashion.  The information distributed using ISIS TE Metric
   Extensions can then be used to make path selection decisions based on
   network performance.

   Note that this document only covers the mechanisms with which network
   performance information is distributed.  The mechanisms for measuring
   network performance or acting on that information, once distributed,
   are outside the scope of this document.

Requirements Language

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in RFC 2119 [RFC2119].

   In this document, these words will appear with that interpretation
   only when in ALL CAPS.  Lower case uses of these words are not to be
   interpreted as carrying RFC-2119 significance.

Status of this Memo



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   This Internet-Draft is submitted in full conformance with the
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   This Internet-Draft will expire on April 13, 2014.

Copyright Notice

   Copyright (c) 2013 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
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   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.






















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Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  4
   2.  TE Metric Extensions to IS-IS  . . . . . . . . . . . . . . . .  5
   3.  Interface and Neighbor Addresses . . . . . . . . . . . . . . .  6
   4.  Sub TLV Details  . . . . . . . . . . . . . . . . . . . . . . .  6
     4.1.  Unidirectional Link Delay Sub-TLV  . . . . . . . . . . . .  7
     4.2.  Min/Max Unidirectional Link Delay Sub-TLV  . . . . . . . .  7
     4.3.  Unidirectional Delay Variation Sub-TLV . . . . . . . . . .  9
     4.4.  Unidirectional Link Loss Sub-TLV . . . . . . . . . . . . .  9
     4.5.  Unidirectional Residual Bandwidth Sub-TLV  . . . . . . . . 10
     4.6.  Unidirectional Available Bandwidth Sub-TLV . . . . . . . . 11
     4.7.  Unidirectional Utilized Bandwidth Sub-TLV  . . . . . . . . 12
   5.  Announcement Thresholds and Filters  . . . . . . . . . . . . . 13
   6.  Announcement Suppression . . . . . . . . . . . . . . . . . . . 14
   7.  Network Stability and Announcement Periodicity . . . . . . . . 14
   8.  Enabling and Disabling Sub-TLVs  . . . . . . . . . . . . . . . 15
   9.  Static Metric Override . . . . . . . . . . . . . . . . . . . . 15
   10. Compatibility  . . . . . . . . . . . . . . . . . . . . . . . . 15
   11. Security Considerations  . . . . . . . . . . . . . . . . . . . 15
   12. IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 15
   13. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 16
   14. References . . . . . . . . . . . . . . . . . . . . . . . . . . 16
     14.1. Normative References . . . . . . . . . . . . . . . . . . . 16
     14.2. Informative References . . . . . . . . . . . . . . . . . . 17
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 17

























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1.  Introduction

   In certain networks, such as, but not limited to, financial
   information networks (e.g. stock market data providers), network
   performance information (e.g. latency) is becoming as critical to
   data path selection as other metrics.

   In these networks, extremely large amounts of money rest on the
   ability to access market data in "real time" and to predictably make
   trades faster than the competition.  Because of this, using metrics
   such as hop count or cost as routing metrics is becoming only
   tangentially important.  Rather, it would be beneficial to be able to
   make path selection decisions based on performance data (such as
   latency) in a cost-effective and scalable way.

   This document describes extensions to IS-IS Extended Reachability TLV
   defined in [RFC5305] (hereafter called "IS-IS TE Metric Extensions"),
   that can be used to distribute network performance information (such
   as link delay, delay variation, packet loss, residual bandwidth, and
   available bandwidth).

   The data distributed by the TE Metric Extensions proposed in this
   document is meant to be used as part of the operation of the routing
   protocol (e.g. by replacing cost with latency or considering
   bandwidth as well as cost), by enhancing Constrained-SPF (CSPF), or
   for other uses such as supplementing the data used by an ALTO server
   [I-D.ietf-alto-protocol].  With respect to CSPF, the data distributed
   by ISIS TE Metric Extensions can be used to setup, fail over, and
   fail back data paths using protocols such as RSVP-TE [RFC3209];
   [I-D.atlas-mpls-te-express-path] describes some methods for using
   this information to compute Label Switched Paths (LSPs) at the LSP
   ingress.

   Note that the mechanisms described in this document only disseminate
   performance information.  The methods for initially gathering that
   performance information, such as [RFC6375], or acting on it once it
   is distributed are outside the scope of this document.  Example
   mechanisms to measure latency, delay variation, and loss in an MPLS
   network are given in [RFC6374].  While this document does not specify
   how the performance information should be obtained, the measurement
   of delay SHOULD NOT vary significantly based upon the offered traffic
   load.  Thus, queuing delays SHOULD NOT be included in the delay
   measurement.  For links, such as Forwarding Adjacencies, care must be
   taken that measurement of the associated delay avoids significant
   queuing delay; that could be accomplished in a variety of ways,
   including either by measuring with a traffic class that experiences
   minimal queuing or by summing the measured link delays of the
   components of the link's path.



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2.  TE Metric Extensions to IS-IS

   This document proposes new IS-IS TE sub-TLVs that can be announced in
   ISIS Extended Reachability TLV (TLV-22) to distribute network
   performance information.  The extensions in this document build on
   the ones provided in IS-IS TE [RFC5305] and GMPLS [RFC4203].

   IS-IS Extended Reachability TLV 22 (defined in [RFC5305]), Inter-AS
   reachability information TLV 141 (defined in [RFC5316]) and MT-ISN
   TLV 222 (defined in [RFC5120]) have nested sub-TLVs which permit the
   TLVs to be readily extended.  This document proposes several
   additional sub-TLVs:
      Type         Value
      -----------------------------------------------
      TBA          Unidirectional Link Delay

      TBA          Low/High Unidirectional Link Delay

      TBA          Unidirectional Delay Variation

      TBA          Unidirectional Packet Loss

      TBA          Unidirectional Residual Bandwidth

      TBA          Unidirectional Available Bandwidth

      TBA          Unidirectional Bandwidth Utilization

   As can be seen in the list above, the sub-TLVs described in this
   document carry different types of network performance information.
   The new sub-TLVs include a bit called the Anomalous (or "A") bit.
   When the A bit is clear (or when the sub-TLV does not include an A
   bit), the sub-TLV describes steady state link performance.  This
   information could conceivably be used to construct a steady state
   performance topology for initial tunnel path computation, or to
   verify alternative failover paths.

   When network performance violates configurable link-local thresholds
   a sub-TLV with the A bit set is advertised.  These sub-TLVs could be
   used by the receiving node to determine whether to fail traffic to a
   backup path, or whether to calculate an entirely new path.  From an
   MPLS perspective, the intent of the A bit is to permit LSP ingress
   nodes to:








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   A) Determine whether the link referenced in the sub-TLV affects any
      of the LSPs for which it is ingress. If there are, then:

   B) Determine whether those LSPs still meet end-to-end performance
      objectives. If not, then:

   C) The node could then conceivably move affected traffic to a pre-
      established protection LSP or establish a new LSP and place the
      traffic in it.

   If link performance then improves beyond a configurable minimum value
   (reuse threshold), that sub-TLV can be re-advertised with the
   Anomalous bit cleared.  In this case, a receiving node can
   conceivably do whatever re-optimization (or failback) it wishes to do
   (including nothing).

   Note that when a sub-TLV does not include the A bit, that sub-TLV
   cannot be used for failover purposes.  The A bit was intentionally
   omitted from some sub-TLVs to help mitigate oscillations.  See
   Section 5 for more information.

   Consistent with existing IS-IS TE specifications [RFC5305], the
   bandwidth advertisements defined in this draft MUST be encoded as
   IEEE floating point values.  The delay and delay variation
   advertisements defined in this draft MUST be encoded as integer
   values.  Delay values MUST be quantified in units of microseconds,
   packet loss MUST be quantified as a percentage of packets sent, and
   bandwidth MUST be sent as bytes per second.  All values (except
   residual bandwidth) MUST be calculated as rolling averages where the
   averaging period MUST be a configurable period of time.  See
   Section 5 for more information.


3.  Interface and Neighbor Addresses

   The use of TE Metric Extensions SubTLVs is not confined to the TE
   context.  In other words, IS-IS TE Metric Extensions SubTLVs defined
   in this document can also be used for computing paths in the absence
   of a TE subsystem.

   However, as for the TE case, Interface Address and Neighbor Address
   SubTLVs (IPv4 or IPv6) MUST be present.  The encoding is defined in
   [RFC5305] for IPv4 and in [RFC6119] for IPv6.


4.  Sub TLV Details





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4.1.  Unidirectional Link Delay Sub-TLV

   This sub-TLV advertises the average link delay between two directly
   connected IS-IS neighbors.  The delay advertised by this sub-TLV MUST
   be the delay from the local neighbor to the remote one (i.e. the
   forward path latency).  The format of this sub-TLV is shown in the
   following diagram:
     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    |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |A|   RESERVED  |                   Delay                       |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

     where:

                                 Figure 1

   Type: TBA

   Length: 4

   A-bit.  The A-bit represents the Anomalous (A) bit.  The A-bit is set
   when the measured value of this parameter exceeds its configured
   maximum threshold.  The A bit is cleared when the measured value
   falls below its configured reuse threshold.  If the A-bit is clear,
   the sub-TLV represents steady state link performance.

   RESERVED.  This field is reserved for future use.  It MUST be set to
   0 when sent and MUST be ignored when received.

   Delay.  This 24-bit field carries the average link delay over a
   configurable interval in micro-seconds, encoded as an integer value.
   When set to the maximum value 16,777,215 (16.777215 sec), then the
   delay is at least that value and may be larger.  If there is no value
   to send (unmeasured and not statically specified), then the sub-TLV
   should not be sent or be withdrawn.

4.2.  Min/Max Unidirectional Link Delay Sub-TLV

   This sub-TLV advertises the minimum and maximum delay values between
   two directly connected IS-IS neighbors.  The delay advertised by this
   sub-TLV MUST be the delay from the local neighbor to the remote one
   (i.e. the forward path latency).  The format of this sub-TLV is shown
   in the following diagram:





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      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    |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |A| RESERVED    |                   Low Delay                   |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |   RESERVED    |                   High Delay                  |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

     where:

                                 Figure 2

   Type: TBA

   Length: 8

   A-bit.  The A-bit represents the Anomalous (A) bit.  The A-bit is set
   when the measured value of this parameter exceeds its configured
   maximum threshold.  The A bit is cleared when the measured value
   falls below its configured reuse threshold.  If the A-bit is clear,
   the sub-TLV represents steady state link performance.

   RESERVED.  This field is reserved for future use.  It MUST be set to
   0 when sent and MUST be ignored when received.

   Low Delay.  This 24-bit field carries minimum measured link delay
   value (in microseconds) over a configurable interval, encoded as an
   integer value.

   High Delay.  This 24-bit field carries the maximum measured link
   delay value (in microseconds) over a configurable interval, encoded
   as an integer value.

   Implementations MAY also permit the configuration of a static (non
   dynamic) offset value (in microseconds) to be added to the measured
   delay value, to facilitate the communication of operator specific
   delay constraints.

   It is possible for the high delay and low delay to be the same value.

   When the delay value (Low or High) is set to maximum value 16,777,215
   (16.777215 sec), then the delay is at least that value and may be
   larger.






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4.3.  Unidirectional Delay Variation Sub-TLV

   This sub-TLV advertises the average link delay variation between two
   directly connected IS-IS neighbors.  The delay variation advertised
   by this sub-TLV MUST be the delay from the local neighbor to the
   remote one (i.e. the forward path latency).  The format of this sub-
   TLV is shown in the following diagram:
     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    |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |A|  RESERVED   |               Delay Variation                 |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

     where:

                                 Figure 3

   Type: TBA.

   Lenght: 4.

   A-bit.  The A-bit represents the Anomalous (A) bit.  The A-bit is set
   when the measured value of this parameter exceeds its configured
   maximum threshold.  The A bit is cleared when the measured value
   falls below its configured reuse threshold.  If the A-bit is clear,
   the sub-TLV represents steady state link performance.

   RESERVED.  This field is reserved for future use.  It MUST be set to
   0 when sent and MUST be ignored when received.

   Delay Variation.  This 24-bit field carries the average link delay
   variation over a configurable interval in micro-seconds, encoded as
   an integer value.  When set to 0, it has not been measured.  When set
   to the maximum value 16,777,215 (16.777215 sec), then the delay is at
   least that value and may be larger.

4.4.  Unidirectional Link Loss Sub-TLV

   This sub-TLV advertises the loss (as a packet percentage) between two
   directly connected IS-IS neighbors.  The link loss advertised by this
   sub-TLV MUST be the packet loss from the local neighbor to the remote
   one (i.e. the forward path loss).  The format of this sub-TLV is
   shown in the following diagram:






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   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    |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |A|  RESERVED   |                  Link Loss                    |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

      This sub-TLV has a type of TBD3.
      The length is 4.

   where:

   Type: TBA.

   Length: 4.

   A-bit.  The A-bit represents the Anomalous (A) bit.  The A-bit is set
   when the measured value of this parameter exceeds its configured
   maximum threshold.  The A bit is cleared when the measured value
   falls below its configured reuse threshold.  If the A-bit is clear,
   the sub-TLV represents steady state link performance.

   A-bit.  The A-bit represents the Anomalous (A) bit.  The A-bit is set
   when the measured value of this parameter exceeds its configured
   maximum threshold.  The A bit is cleared when the measured value
   falls below its configured reuse threshold.  If the A-bit is clear,
   the sub-TLV represents steady state link performance.

   RESERVED.  This field is reserved for future use.  It MUST be set to
   0 when sent and MUST be ignored when received.

   Link Loss.  This 24-bit field carries link packet loss as a
   percentage of the total traffic sent over a configurable interval.
   The basic unit is 0.000003%, where (2^24 - 2) is 50.331642%.  This
   value is the highest packet loss percentage that can be expressed
   (the assumption being that precision is more important on high speed
   links than the ability to advertise loss rates greater than this, and
   that high speed links with over 50% loss are unusable).  Therefore,
   measured values that are larger than the field maximum SHOULD be
   encoded as the maximum value.  When set to a value of all 1s (2^24 -
   1), the link packet loss has not been measured.

4.5.  Unidirectional Residual Bandwidth Sub-TLV

   This TLV advertises the residual bandwidth between two directly
   connected IS-IS neighbors.  The residual bandwidth advertised by this
   sub-TLV MUST be the residual bandwidth from the system originating



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   the LSA to its neighbor.
   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    |A|  RESERVED   |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                          Residual Bandwidth                   |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   where:

   Type: TBA.

   Length: 4.

   A-bit.  The A-bit represents the Anomalous (A) bit.  The A-bit is set
   when the measured value of this parameter exceeds its configured
   maximum threshold.  The A bit is cleared when the measured value
   falls below its configured reuse threshold.  If the A-bit is clear,
   the sub-TLV represents steady state link performance.

   RESERVED.  This field is reserved for future use.  It MUST be set to
   0 when sent and MUST be ignored when received.

   Residual Bandwidth.  This field carries the residual bandwidth on a
   link, forwarding adjacency [RFC4206], or bundled link in IEEE
   floating point format with units of bytes per second.  For a link or
   forwarding adjacency, residual bandwidth is defined to be Maximum
   Bandwidth [RFC3630] minus the bandwidth currently allocated to
   RSVP-TE LSPs.  For a bundled link, residual bandwidth is defined to
   be the sum of the component link residual bandwidths.

   The calculation of Residual Bandwidth is different than that of
   Unreserved Bandwidth [RFC3630].  Residual Bandwidth subtracts tunnel
   reservations from Maximum Bandwidth (i.e. the link capacity)
   [RFC3630] and provides an aggregated remainder across QoS classes.
   Unreserved Bandwidth [RFC3630], on the other hand, is subtracted from
   the Maximum Reservable Bandwidth (the bandwidth that can
   theoretically be reserved) [RFC3630] and provides per-QoS-class
   remainders.  Residual Bandwidth and Unreserved Bandwidth [RFC3630]
   can be used concurrently, and each has a separate use case (e.g. the
   former can be used for applications like Weighted ECMP while the
   latter can be used for call admission control).

4.6.  Unidirectional Available Bandwidth Sub-TLV

   This Sub-TLV advertises the available bandwidth between two directly
   connected IS-IS neighbors.  The available bandwidth advertised by



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   this sub-TLV MUST be the available bandwidth from the system
   originating this Sub-TLV.  The format of this Sub-TLV is shown in the
   following diagram:
      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    |A|  RESERVED   |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                      Available Bandwidth                      |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

     where:

                                 Figure 4

   Type: TBA.

   Length: 4.

   A-bit.  The A-bit represents the Anomalous (A) bit.  The A-bit is set
   when the measured value of this parameter exceeds its configured
   maximum threshold.  The A bit is cleared when the measured value
   falls below its configured reuse threshold.  If the A-bit is clear,
   the sub-TLV represents steady state link performance.

   RESERVED.  This field is reserved for future use.  It MUST be set to
   0 when sent and MUST be ignored when received.

   Available Bandwidth.  This field carries the available bandwidth on a
   link, forwarding adjacency, or bundled link in IEEE floating point
   format with units of bytes per second.  For a link or forwarding
   adjacency, available bandwidth is defined to be residual bandwidth
   minus the measured bandwidth used for the actual forwarding of non-
   RSVP-TE LSP packets.  For a bundled link, available bandwidth is
   defined to be the sum of the component link available bandwidths
   minus the measured bandwidth used for the actual forwarding of non-
   RSVP-TE Label Switched Paths packets.  For a bundled link, available
   bandwidth is defined to be the sum of the component link available
   bandwidths.

4.7.  Unidirectional Utilized Bandwidth Sub-TLV

   This Sub-TLV advertises the bandwidth utilization between two
   directly connected IS-IS neighbors.  The bandwidth utilization
   advertised by this sub-TLV MUST be the bandwidth from the system
   originating this Sub-TLV.  The format of this Sub-TLV is shown in the
   following diagram:




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      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    |A|  RESERVED   |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                       Bandwidth Utilization                   |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

     where:

                                 Figure 5

   Type: TBA.

   Length: 4.

   A-bit.  The A-bit represents the Anomalous (A) bit.  The A-bit is set
   when the measured value of this parameter exceeds its configured
   maximum threshold.  The A bit is cleared when the measured value
   falls below its configured reuse threshold.  If the A-bit is clear,
   the sub-TLV represents steady state link performance.

   RESERVED.  This field is reserved for future use.  It MUST be set to
   0 when sent and MUST be ignored when received.

   Bandwidth Utilization.  This field carries the bandwidth utilization
   on a link, forwarding adjacency, or bundled link in IEEE floating
   point format with units of bytes per second.  For a link or
   forwarding adjacency, bandwidth utilization represent the actual
   utilization of the link (i.e.: as measured in the router).  For a
   bundled link, bandwidth utilization is defined to be the sum of the
   component link bandwidth utilization.


5.  Announcement Thresholds and Filters

   The values advertised in all sub-TLVs (except Low/High delay and
   residual bandwidth) MUST represent an average over a period or be
   obtained by a filter that is reasonably representative of an average.
   For example, a rolling average is one such filter.

   Low or High delay MAY be the lowest and/or highest measured value
   over a measurement interval or MAY make use of a filter, or other
   technique to obtain a reasonable representation of a low and high
   value representative of the interval with compensation for outliers.

   The measurement interval, any filter coefficients, and any
   advertisement intervals MUST be configurable per sub-TLV.



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   In addition to the measurement intervals governing re-advertisement,
   implementations SHOULD provide per sub-TLV configurable accelerated
   advertisement thresholds, such that:
   1. If the measured parameter falls outside a configured upper
      bound for all but the low delay metric (or lower bound for
      low-delay metric only) and the advertised sub-TLV is not
      already outside that bound or,

   2. If the difference between the last advertised value and
      current measured value exceed a configured threshold then,

   3. The advertisement is made immediately.

   4. For sub-TLVs which include an A-bit (except low/high
      delay), an additional threshold SHOULD be included
      corresponding to the threshold for which the performance
      is considered anomalous (and sub-TLVs with the A-bit are
      sent). The A-bit is cleared when the sub-TLV's performance
      has been below (or re-crosses) this threshold for an
      advertisement interval(s) to permit fail back.

   To prevent oscillations, only the high threshold or the low threshold
   (but not both) may be used to trigger any given sub-TLV that supports
   both.

   Additionally, once outside of the bounds of the threshold, any
   readvertisement of a measurement within the bounds would remain
   governed solely by the measurement interval for that sub-TLV.


6.  Announcement Suppression

   When link performance values change by small amounts that fall under
   thresholds that would cause the announcement of a sub-TLV,
   implementations SHOULD suppress sub-TLV readvertisement and/or
   lengthen the period within which they are refreshed.

   Only the accelerated advertisement threshold mechanism may shorten
   the re-advertisement interval.  All suppression and re-advertisement
   interval backoff timer features SHOULD be configurable.


7.  Network Stability and Announcement Periodicity

   Section 5 and Section 6 provide configurable mechanisms to bound the
   number of re-advertisements.  Instability might occur in very large
   networks if measurement intervals are set low enough to overwhelm the
   processing of flooded information at some of the routers in the



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   topology.  Therefore care SHOULD be taken in setting these values.

   Additionally, the default measurement interval for all sub-TLVs
   SHOULD be 30 seconds.

   Announcements MUST also be able to be throttled using configurable
   inter-update throttle timers.  The minimum announcement periodicity
   is 1 announcement per second.  The default value SHOULD be set to 120
   seconds.

   Implementations SHOULD NOT permit the inter-update timer to be lower
   than the measurement interval.

   Furthermore, it is RECOMMENDED that any underlying performance
   measurement mechanisms not include any significant buffer delay, any
   significant buffer induced delay variation, or any significant loss
   due to buffer overflow or due to active queue management.


8.  Enabling and Disabling Sub-TLVs

   Implementations MUST make it possible to individually enable or
   disable each sub-TLV based on configuration.


9.  Static Metric Override

   Implementations SHOULD permit the static configuration and/or manual
   override of dynamic measurements data on a per sub-TLV, per metric
   basis in order to simplify migrations and to mitigate scenarios where
   measurements are not possible across an entire network.


10.  Compatibility

   As per [RFC5305], unrecognized Sub-TLVs should be silently ignored


11.  Security Considerations

   This document does not introduce security issues beyond those
   discussed in [RFC3630] and [RFC5329].


12.  IANA Considerations

   IANA maintains the registry for the sub-TLVs.  IS-IS TE Metric
   Extensions will require one new type code per sub-TLV defined in this



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   document.


13.  Acknowledgements

   The authors would like to recognize Ayman Soliman, Nabil Bitar, David
   McDysan, Les Ginsberg, Edward Crabbe, Don Fedyk and Hannes Gredler
   for their contributions.

   The authors also recognize Curtis Villamizar for significant comments
   and direct content collaboration.


14.  References

14.1.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.

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

   [RFC3630]  Katz, D., Kompella, K., and D. Yeung, "Traffic Engineering
              (TE) Extensions to OSPF Version 2", RFC 3630,
              September 2003.

   [RFC4203]  Kompella, K. and Y. Rekhter, "OSPF Extensions in Support
              of Generalized Multi-Protocol Label Switching (GMPLS)",
              RFC 4203, October 2005.

   [RFC4206]  Kompella, K. and Y. Rekhter, "Label Switched Paths (LSP)
              Hierarchy with Generalized Multi-Protocol Label Switching
              (GMPLS) Traffic Engineering (TE)", RFC 4206, October 2005.

   [RFC5120]  Przygienda, T., Shen, N., and N. Sheth, "M-ISIS: Multi
              Topology (MT) Routing in Intermediate System to
              Intermediate Systems (IS-ISs)", RFC 5120, February 2008.

   [RFC5305]  Li, T. and H. Smit, "IS-IS Extensions for Traffic
              Engineering", RFC 5305, October 2008.

   [RFC5316]  Chen, M., Zhang, R., and X. Duan, "ISIS Extensions in
              Support of Inter-Autonomous System (AS) MPLS and GMPLS
              Traffic Engineering", RFC 5316, December 2008.

   [RFC5329]  Ishiguro, K., Manral, V., Davey, A., and A. Lindem,



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              "Traffic Engineering Extensions to OSPF Version 3",
              RFC 5329, September 2008.

   [RFC6119]  Harrison, J., Berger, J., and M. Bartlett, "IPv6 Traffic
              Engineering in IS-IS", RFC 6119, February 2011.

   [RFC6374]  Frost, D. and S. Bryant, "Packet Loss and Delay
              Measurement for MPLS Networks", RFC 6374, September 2011.

14.2.  Informative References

   [I-D.atlas-mpls-te-express-path]
              Atlas, A., Drake, J., Giacalone, S., Ward, D., Previdi,
              S., and C. Filsfils, "Performance-based Path Selection for
              Explicitly Routed LSPs using TE Metric Extensions",
              draft-atlas-mpls-te-express-path-04 (work in progress),
              September 2013.

   [I-D.ietf-alto-protocol]
              Alimi, R., Penno, R., and Y. Yang, "ALTO Protocol",
              draft-ietf-alto-protocol-20 (work in progress),
              October 2013.

   [RFC6375]  Frost, D. and S. Bryant, "A Packet Loss and Delay
              Measurement Profile for MPLS-Based Transport Networks",
              RFC 6375, September 2011.


Authors' Addresses

   Stefano Previdi (editor)
   Cisco Systems, Inc.
   Via Del Serafico 200
   Rome  00191
   IT

   Email: sprevidi@cisco.com


   Spencer Giacalone
   Thomson Reuters
   195 Broadway
   New York, NY  10007
   USA

   Email: Spencer.giacalone@thomsonreuters.com





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   Dave Ward
   Cisco Systems, Inc.
   3700 Cisco Way
   SAN JOSE, CA  95134
   US

   Email: wardd@cisco.com


   John Drake
   Juniper Networks
   1194 N. Mathilda Ave.
   Sunnyvale, CA  94089
   USA

   Email: jdrake@juniper.net


   Alia Atlas
   Juniper Networks
   1194 N. Mathilda Ave.
   Sunnyvale, CA  94089
   USA

   Email: akatlas@juniper.net


   Clarence Filsfils
   Cisco Systems, Inc.
   Brussels
   Belgium

   Email: cfilsfil@cisco.com


   Qin Wu
   Huawei
   101 Software Avenue, Yuhua District
   Nanjing, Jiangsu  210012
   China

   Email: sunseawq@huawei.com









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