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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: August 15, 2016                                    Unaffiliated
                                                                 D. Ward
                                                     Cisco Systems, Inc.
                                                                J. Drake
                                                        Juniper Networks
                                                                   Q. Wu
                                                                  Huawei
                                                       February 12, 2016


            IS-IS Traffic Engineering (TE) Metric Extensions
                draft-ietf-isis-te-metric-extensions-11

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 Traffic Engineering
   Extensions (RFC5305) such that network performance information can be
   distributed and collected in a scalable fashion.  The information
   distributed using IS-IS 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.








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Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
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   Internet-Drafts are draft documents valid for a maximum of six months
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   This Internet-Draft will expire on August 15, 2016.

Copyright Notice

   Copyright (c) 2016 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
   (http://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
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   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
   2.  TE Metric Extensions to IS-IS . . . . . . . . . . . . . . . .   4
   3.  Interface and Neighbor Addresses  . . . . . . . . . . . . . .   5
   4.  Sub TLV Details . . . . . . . . . . . . . . . . . . . . . . .   6
     4.1.  Unidirectional Link Delay Sub-TLV . . . . . . . . . . . .   6
     4.2.  Min/Max Unidirectional Link Delay Sub-TLV . . . . . . . .   7
     4.3.  Unidirectional Delay Variation Sub-TLV  . . . . . . . . .   8
     4.4.  Unidirectional Link Loss Sub-TLV  . . . . . . . . . . . .   8
     4.5.  Unidirectional Residual Bandwidth Sub-TLV . . . . . . . .   9
     4.6.  Unidirectional Available Bandwidth Sub-TLV  . . . . . . .  10
     4.7.  Unidirectional Utilized Bandwidth Sub-TLV . . . . . . . .  11
   5.  Announcement Thresholds and Filters . . . . . . . . . . . . .  12
   6.  Announcement Suppression  . . . . . . . . . . . . . . . . . .  13
   7.  Network Stability and Announcement Periodicity  . . . . . . .  13



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   8.  Enabling and Disabling Sub-TLVs . . . . . . . . . . . . . . .  14
   9.  Static Metric Override  . . . . . . . . . . . . . . . . . . .  14
   10. Compatibility . . . . . . . . . . . . . . . . . . . . . . . .  14
   11. Security Considerations . . . . . . . . . . . . . . . . . . .  14
   12. IANA Considerations . . . . . . . . . . . . . . . . . . . . .  15
   13. Contributors  . . . . . . . . . . . . . . . . . . . . . . . .  15
   14. Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  16
   15. References  . . . . . . . . . . . . . . . . . . . . . . . . .  16
     15.1.  Normative References . . . . . . . . . . . . . . . . . .  16
     15.2.  Informative References . . . . . . . . . . . . . . . . .  17
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  17

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 (hereafter called "IS-IS TE Metric
   Extensions") to IS-IS Extended Reachability TLV defined in [RFC5305],
   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 IS-IS 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
   [RFC7285].  With respect to CSPF, the data distributed by IS-IS TE
   Metric Extensions can be used to setup, fail over, and fail back data
   paths using protocols such as RSVP-TE [RFC3209].

   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



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   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.

2.  TE Metric Extensions to IS-IS

   This document proposes new IS-IS TE sub-TLVs that can be announced in
   TLVs 22, 141, 222, and 223 in order 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-ISIS
   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
   ----------------------------------------------------
    33 (Suggested) Unidirectional Link Delay

    34 (Suggested) Min/Max Unidirectional Link Delay

    35 (Suggested) Unidirectional Delay Variation

    36 (Suggested) Unidirectional Packet Loss

    37 (Suggested) Unidirectional Residual Bandwidth

    38 (Suggested) Unidirectional Available Bandwidth

    39 (Suggested) 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.




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   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:

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






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

4.  Sub TLV Details

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 (suggested value: 33).

   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.








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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:

    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    |                   Min Delay                   |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |   RESERVED    |                   Max Delay                   |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   where:

                                 Figure 2

   Type: TBA (suggested value: 34).

   Length: 8.

   This field represents the Anomalous (A) bit.  The A bit is set when
   one or more measured values exceed a 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.

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

   Max 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 an 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 Min and Max delay to be the same value.



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

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    |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |  RESERVED     |               Delay Variation                 |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   where:

                                 Figure 3

   Type: TBA (suggested value: 35).

   Length: 4.

   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 microseconds, 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 (suggested value: 36).

   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.

   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.

4.5.  Unidirectional Residual Bandwidth Sub-TLV

   This sub-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
   the LSA to its neighbor.









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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    |  RESERVED     |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                          Residual Bandwidth                   |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   where:

   Type: TBA (suggested value: 37).

   Length: 4.

   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 [RFC5305] 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 [RFC5305].  Residual Bandwidth subtracts tunnel
   reservations from Maximum Bandwidth (i.e. the link capacity)
   [RFC5305] and provides an aggregated remainder across priorities.
   Unreserved Bandwidth, on the other hand, is subtracted from the
   Maximum Reservable Bandwidth (the bandwidth that can theoretically be
   reserved) and provides per priority remainders.  Residual Bandwidth
   and Unreserved Bandwidth [RFC5305] 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
   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:







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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    |  RESERVED     |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                      Available Bandwidth                      |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   where:

                                 Figure 4

   Type: TBA (suggested value: 38).

   Length: 4.

   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
   (see Section 4.5 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    |  RESERVED     |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                     Utilized Bandwidth                        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   where:

                                 Figure 5

   Type: TBA (suggested value: 39).

   Length: 4.

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

   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 represents the actual utilization of the link (i.e., as
   measured by the advertising node).  For a bundled link, bandwidth
   utilization is defined to be the sum of the component link bandwidth
   utilizations.

5.  Announcement Thresholds and Filters

   The values advertised in all sub-TLVs (except Min/Max 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.

   Min and max delay MUST each be derived in one of the following ways:
   by taking the lowest and/or highest measured value over a measurement
   interval, or by making use of a filter or other technique to obtain a
   reasonable representation of a min and max 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.

   In addition to the measurement intervals governing re-advertisement,
   implementations SHOULD provide per sub-TLV configurable accelerated
   advertisement thresholds, such that:





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   1. If the measured parameter falls outside a configured upper
      bound for all but the min delay metric (or lower bound for
      min 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, 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 described in
   Section 5 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
   topology.  Therefore care should be taken in setting these values.

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



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   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 for each sub-TLV in order to
   simplify migration and to mitigate scenarios where dynamic
   measurements are not possible.

10.  Compatibility

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

11.  Security Considerations

   The subTLVs introduced in this document allow an operator to
   advertise state information of links (bandwidth, delay) that could be
   sensitive and that an operator may not want to disclose.

   Section 7 describe a mechanism in order to ensure network stability
   when the new sub-TLVs defined in this document are advertised.
   Implementation SHOULD follow the described guidelines in order to
   mitigate the instability risk.

   [RFC5304] describes an authentication method for IS-IS LSP that
   allows cryptographic authentication of IS-IS LSPs.

   It is anticipated that in most deployments, IS-IS protocol is used
   within an infrastructure entirely under control of the same operator.
   However, it is worth to consider that the effect of sending IS-IS
   Traffic Engineering sub-TLVs over insecure links could result in a
   man-in-the-middle attacker delaying real time data to a given site



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   (or destination), which could negatively affect the value of the data
   for that site/destination.  The use of LSP cryptographic
   authentication allows to mitigate the risk of man-in-the-middle
   attack.

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
   document in the following sub-TLV registry: TLVs 22, 23, 141, 222,
   and 223:

   Type                   Value
   ----------------------------------------------------
    33 (Suggested) Unidirectional Link Delay

    34 (Suggested) Min/Max Unidirectional Link Delay

    35 (Suggested) Unidirectional Delay Variation

    36 (Suggested) Unidirectional Packet Loss

    37 (Suggested) Unidirectional Residual Bandwidth

    38 (Suggested) Unidirectional Available Bandwidth

    39 (Suggested) Unidirectional Bandwidth Utilization

13.  Contributors

   The following people gave a substantial contribution to the content
   of this document and should be considered as co-authors:

   Alia Atlas
   Juniper Networks
   US

   akatlas@juniper.net


   Clarence Filsfils
   Cisco Systems Inc.
   Belgium

   Email: cfilsfil@cisco.com






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14.  Acknowledgements

   The authors would like to recognize Ayman Soliman, Nabil Bitar, David
   McDysan, Les Ginsberg, Edward Crabbe, Don Fedyk, Hannes Gredler, Uma
   Chunduri, Alvaro Retana, Brian Weis and Barry Leiba for their
   contribution and review of this document.

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

15.  References

15.1.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,
              <http://www.rfc-editor.org/info/rfc2119>.

   [RFC4206]  Kompella, K. and Y. Rekhter, "Label Switched Paths (LSP)
              Hierarchy with Generalized Multi-Protocol Label Switching
              (GMPLS) Traffic Engineering (TE)", RFC 4206,
              DOI 10.17487/RFC4206, October 2005,
              <http://www.rfc-editor.org/info/rfc4206>.

   [RFC5120]  Przygienda, T., Shen, N., and N. Sheth, "M-ISIS: Multi
              Topology (MT) Routing in Intermediate System to
              Intermediate Systems (IS-ISs)", RFC 5120,
              DOI 10.17487/RFC5120, February 2008,
              <http://www.rfc-editor.org/info/rfc5120>.

   [RFC5304]  Li, T. and R. Atkinson, "IS-IS Cryptographic
              Authentication", RFC 5304, DOI 10.17487/RFC5304, October
              2008, <http://www.rfc-editor.org/info/rfc5304>.

   [RFC5305]  Li, T. and H. Smit, "IS-IS Extensions for Traffic
              Engineering", RFC 5305, DOI 10.17487/RFC5305, October
              2008, <http://www.rfc-editor.org/info/rfc5305>.

   [RFC5316]  Chen, M., Zhang, R., and X. Duan, "ISIS Extensions in
              Support of Inter-Autonomous System (AS) MPLS and GMPLS
              Traffic Engineering", RFC 5316, DOI 10.17487/RFC5316,
              December 2008, <http://www.rfc-editor.org/info/rfc5316>.

   [RFC6119]  Harrison, J., Berger, J., and M. Bartlett, "IPv6 Traffic
              Engineering in IS-IS", RFC 6119, DOI 10.17487/RFC6119,
              February 2011, <http://www.rfc-editor.org/info/rfc6119>.




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15.2.  Informative References

   [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,
              <http://www.rfc-editor.org/info/rfc3209>.

   [RFC4203]  Kompella, K., Ed. and Y. Rekhter, Ed., "OSPF Extensions in
              Support of Generalized Multi-Protocol Label Switching
              (GMPLS)", RFC 4203, DOI 10.17487/RFC4203, October 2005,
              <http://www.rfc-editor.org/info/rfc4203>.

   [RFC6374]  Frost, D. and S. Bryant, "Packet Loss and Delay
              Measurement for MPLS Networks", RFC 6374,
              DOI 10.17487/RFC6374, September 2011,
              <http://www.rfc-editor.org/info/rfc6374>.

   [RFC6375]  Frost, D., Ed. and S. Bryant, Ed., "A Packet Loss and
              Delay Measurement Profile for MPLS-Based Transport
              Networks", RFC 6375, DOI 10.17487/RFC6375, September 2011,
              <http://www.rfc-editor.org/info/rfc6375>.

   [RFC7285]  Alimi, R., Ed., Penno, R., Ed., Yang, Y., Ed., Kiesel, S.,
              Previdi, S., Roome, W., Shalunov, S., and R. Woundy,
              "Application-Layer Traffic Optimization (ALTO) Protocol",
              RFC 7285, DOI 10.17487/RFC7285, September 2014,
              <http://www.rfc-editor.org/info/rfc7285>.

Authors' Addresses

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

   Email: sprevidi@cisco.com


   Spencer Giacalone
   Unaffiliated

   Email: spencer.giacalone@gmail.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


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

   Email: sunseawq@huawei.com


























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