



LSR Working Group                                         R. Gandhi, Ed.
Internet-Draft                                       Cisco Systems, Inc.
Intended status: Standards Track                            22 July 2025
Expires: 23 January 2026


   IS-IS, OSPF and BGP-LS Traffic Engineering and Flexible Algorithm
            Extensions for Utilizing Bit Error Rate Metrics
                        draft-gandhi-lsr-ber-00

Abstract

   This document describes extensions to IS-IS, OSPF, and BGP-LS Traffic
   Engineering to distribute the Bit Error Rate (BER) and Packet Error
   Rate (PER) metrics for the links that can be used for flexible
   algorithm and path selection purpose.


   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.

Status of This Memo

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

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   This Internet-Draft will expire on 23 January 2026.

Copyright Notice

   Copyright (c) 2025 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents (https://trustee.ietf.org/
   license-info) in effect on the date of publication of this document.



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   Please review these documents carefully, as they describe your rights
   and restrictions with respect to this document.  Code Components
   extracted from this document must include Revised BSD License text as
   described in Section 4.e of the Trust Legal Provisions and are
   provided without warranty as described in the Revised BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Conventions Used in This Document . . . . . . . . . . . . . .   3
     2.1.  Requirements Language . . . . . . . . . . . . . . . . . .   3
     2.2.  Abbreviations . . . . . . . . . . . . . . . . . . . . . .   3
   3.  Overview  . . . . . . . . . . . . . . . . . . . . . . . . . .   3
   4.  IS-IS Extensions  . . . . . . . . . . . . . . . . . . . . . .   4
   5.  OSPF Extensions . . . . . . . . . . . . . . . . . . . . . . .   5
   6.  BGP-LS Extensions . . . . . . . . . . . . . . . . . . . . . .   6
   7.  Flexible Algorithm Type Extensions  . . . . . . . . . . . . .   6
   8.  Security Considerations . . . . . . . . . . . . . . . . . . .   7
   9.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   7
   10. References  . . . . . . . . . . . . . . . . . . . . . . . . .   8
     10.1.  Normative References . . . . . . . . . . . . . . . . . .   8
     10.2.  Informative References . . . . . . . . . . . . . . . . .   8
   Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . .   9
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .   9

1.  Introduction

   Networks may experience transmission bit errors due to various
   factors, such as poor fiber quality.  The bit error can be a single
   bit error or a burst of bit errors at a time.  Bit errors include
   layer-2 bit errors (e.g., causing CRC errors) or layer-3 and layer-4
   bit errors (e.g., causing checksum failures).  It is feasible to
   measure the Bit Error Rate (BER) and Packet Error Rate (PER) of the
   links using measurement packets.  However, the measured BER and PER
   metrics are currently not used in flexible-algorithm and traffic
   engineering as they are not advertised in IS-IS, OSPF or BGP-LS.

   [RFC8570] for IS-IS, [RFC7471] for OSPF, and [RFC8571] for BGP-LS,
   define TE metrics extensions for distributing latency, loss, and
   bandwidth metrics.  These documents, however, do not define
   extensions for distributing BER and PER metrics.

   In this document, IS-IS, OSPF, and BGP-LS extensions are defined to
   advertise the BER and PER metrics for the links in the network that
   can be used for flexible algorithm and TE.  Also, IS-IS, OSPF and
   BGP-LS extensions are defined to advertise anomaly state of the links
   that can be used to avoid the links with anomaly state.




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2.  Conventions Used in This Document

2.1.  Requirements Language

   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.

2.2.  Abbreviations

   BER: Bit Error Rate

   EMA: Exponential Moving Average

   MTU: Maximum Transmission Unit

   PER: Rate of Packets with Bit Errors

   TLV: Type-Length-Value

3.  Overview

   In this document, IS-IS, OSPF, and BGP-LS extensions are defined to
   advertise the BER and PER metrics for the links in the network that
   can be used for flexible algorithm and TE.  Also, IS-IS, OSPF and
   BGP-LS extensions are defined to advertise anomaly state of the links
   that can be used to avoid the links with anomaly state.

   Various BER metrics are distributed including:

   (1) Average BER

   (2) Maximum BER

   (3) Minimum BER

   (4) Exponential Moving Average of BER

   (5) Variance of BER (difference of minimum and average, for example)

   (6) BER anomaly state

   Various PER metrics are distributed including:

   (1) Average PER




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   (2) Maximum PER

   (3) Minimum PER

   (4) Exponential Moving Average EMA) of PER

   (5) Variance of PER metrics (difference of minimum and average, for
   example)

   (6) PER anomaly state

   Editor's note: The PER metric can be added in the existing packet
   loss metric (instead of using it as a separate metric).  However, the
   BER metric can provide different characteristics of the network, as
   depending on the BER pattern (bursty or single), there can be high
   BER but low packet loss, and vice versa.

   Editor's note: The BER and PER metrics of the links can be used as
   generic metrics in IS-IS, OSPF and BGP-LS.

4.  IS-IS Extensions

   This document extends the sub-TLV structure define in [RFC8570].
   This document registers new IS-IS TE sub-TLVs in the "Sub-TLVs for
   TLVs 22, 23, 141, 222, and 223" registry.  These new sub-TLVs provide
   ways to distribute network-performance information.  The extensions
   in this document build on the extensions provided in IS-IS TE
   [RFC5305] and GMPLS [RFC4203].

   The Extended IS Reachability TLV (type 22) (defined in [RFC5305]),
   Inter-AS Reachability TLV (also called "inter-AS reachability
   information TLV") (type 141) (defined in [RFC9346]), and MT-ISN TLV
   (type 222) (defined in [RFC5120]) have nested sub-TLVs that permit
   the TLVs to be readily extended.  This document registers several
   sub-TLVs:

   Type Description

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

   TBA1 Unidirectional Link Average BER

   TBA2 Unidirectional Link Average PER

   Example Sub-TLV for distributing BER metric in IS-IS is shown in
   Figure 1.





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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=4    |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |A|  RESERVED   |                     BER                       |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

         Figure 1: IS-IS Unidirectional Average BER Metric Sub-TLV

   A bit

   This field 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 cleared, the sub-TLV
   represents steady-state link performance.

   Unit for BER and PER Metrics

   This 24-bit field carries BER or PER as a percentage over a
   configurable interval.  The basic unit is 0.000003%, where (2^24 - 2)
   is 50.331642%.  This value is the highest percentage that can be
   expressed (the assumption that high-speed links with over 50% BER/PER
   are unusable).  Measured values that are larger than the field
   maximum SHOULD be encoded as the maximum value.

   The BER metric added is the exponential moving average (EMA) of the
   BER in order to suppress the frequent advertisements.  The metric is
   only distributed when user-configured threshold is crossed for the
   same reason.  This applies to PER metric as well.

5.  OSPF Extensions

   OSPF extensions for TE are defined in [RFC7471].  This document
   defines several additional sub-TLVs for the Link TLV:

   Type Description

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

   TBA3 Unidirectional Link Average BER

   TBA4 Unidirectional Link Average PER

   Example Sub-TLV for distributing BER metric in OSPF is shown in
   Figure 2.




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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 = 4             |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |A|  RESERVED   |                   BER                         |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

          Figure 2: OSPF Unidirectional Average BER Metric Sub-TLV

   The A flag and Unit of BER and PER metrics are defined the same way
   as for IS-IS.

6.  BGP-LS Extensions

   The IGP/TE metrics in BGP Link-State are defined in [RFC8571].  New
   BGP-LS Link Attribute TLVs are defined for BER.  TLV formats follow
   the rules defined in [RFC9552].

   Value TLV Code Point

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

   TBA5 Unidirectional Link Average BER

   TBA6 Unidirectional Link Average PER

   Example TLV for distributing BER metric in BGP-LS is shown in
   Figure 3 below.

      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 = 4            |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |  RESERVED     |               BER                             |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

         Figure 3: BGP-LS Unidirectional Average BER Metric Sub-TLV

   The A flag and Unit of BER and PER metrics are defined the same way
   as for IS-IS.

7.  Flexible Algorithm Type Extensions

   IGP Flexible algorithm is defined in RFC 9502 and RFC 9350.  New IS-
   IS and OSPF Flexible algorithm type extensions are defined using the
   BER and PER metrics of the links.



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   Editor's note: Additional details on the procedure will be added in
   the future revision of this document.

8.  Security Considerations

   The security considerations specified in [RFC8571], [RFC8570], and
   [RFC7471] apply to the procedure and extensions defined in this
   document.

9.  IANA Considerations

   IANA maintains the registry for the sub-TLVs for IS-IS.  IANA is
   requested to allocate the following sub-TLVs in the "Sub-TLVs for
   TLVs 22, 23, 141, 222, and 223" registry:

    +=======+========================================+===============+
    | Value |              Description               | Reference     |
    +=======+========================================+===============+
    | TBA1  | Unidirectional Link Average BER Metric | This document |
    +-------+----------------------------------------+---------------+
    | TBA2  | Unidirectional Link Average PER Metric | This document |
    +-------+----------------------------------------+---------------+

                       Table 1: IS-IS Sub-TLV Types

   IANA maintains the registry for the sub-TLVs for OSPF link TLV.  IANA
   is requested to allocate the following sub-TLVs for the OSPF link
   TLV.

    +=======+========================================+===============+
    | Value |              Description               | Reference     |
    +=======+========================================+===============+
    | TBA3  | Unidirectional Link Average BER Metric | This document |
    +-------+----------------------------------------+---------------+
    | TBA4  | Unidirectional Link Average PER Metric | This document |
    +-------+----------------------------------------+---------------+

                       Table 2: OSPF Sub-TLV Types

   IANA maintains the registry for the link attribute TLVs in BGP-LS.
   IANA is requested to allocate the following link attribute TLVs in
   BGP-LS.









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    +=======+========================================+===============+
    | Value |              Description               | Reference     |
    +=======+========================================+===============+
    | TBA5  | Unidirectional Link Average BER Metric | This document |
    +-------+----------------------------------------+---------------+
    | TBA6  | Unidirectional Link Average PER Metric | This document |
    +-------+----------------------------------------+---------------+

                 Table 3: BGP-LS Link attribute TLV Types

   Editor's note: Additional Sub-TLVs for carrying minimum, maximum, and
   variance of the BER and PER metrics will be defined in the future
   revision of this document.

10.  References

10.1.  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,
              <https://www.rfc-editor.org/info/rfc2119>.

   [RFC7471]  Giacalone, S., Ward, D., Drake, J., Atlas, A., and S.
              Previdi, "OSPF Traffic Engineering (TE) Metric
              Extensions", RFC 7471, DOI 10.17487/RFC7471, March 2015,
              <https://www.rfc-editor.org/info/rfc7471>.

   [RFC8174]  Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
              2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
              May 2017, <https://www.rfc-editor.org/info/rfc8174>.

   [RFC8570]  Ginsberg, L., Ed., Previdi, S., Ed., Giacalone, S., Ward,
              D., Drake, J., and Q. Wu, "IS-IS Traffic Engineering (TE)
              Metric Extensions", RFC 8570, DOI 10.17487/RFC8570, March
              2019, <https://www.rfc-editor.org/info/rfc8570>.

   [RFC8571]  Ginsberg, L., Ed., Previdi, S., Wu, Q., Tantsura, J., and
              C. Filsfils, "BGP - Link State (BGP-LS) Advertisement of
              IGP Traffic Engineering Performance Metric Extensions",
              RFC 8571, DOI 10.17487/RFC8571, March 2019,
              <https://www.rfc-editor.org/info/rfc8571>.

10.2.  Informative References

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



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   [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,
              <https://www.rfc-editor.org/info/rfc4203>.

   [RFC9346]  Chen, M., Ginsberg, L., Previdi, S., and D. Xiaodong, "IS-
              IS Extensions in Support of Inter-Autonomous System (AS)
              MPLS and GMPLS Traffic Engineering", RFC 9346,
              DOI 10.17487/RFC9346, February 2023,
              <https://www.rfc-editor.org/info/rfc9346>.

   [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,
              <https://www.rfc-editor.org/info/rfc5120>.

   [RFC9552]  Talaulikar, K., Ed., "Distribution of Link-State and
              Traffic Engineering Information Using BGP", RFC 9552,
              DOI 10.17487/RFC9552, December 2023,
              <https://www.rfc-editor.org/info/rfc9552>.

Acknowledgments

   TBA.

Author's Address

   Rakesh Gandhi (editor)
   Cisco Systems, Inc.
   Canada
   Email: rgandhi@cisco.com



















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