LSR Working Group R. Gandhi, Ed. Internet-Draft Cisco Systems, Inc. Intended status: Standards Track 18 July 2026 Expires: 19 January 2027 IS-IS, OSPF, and BGP-LS Extensions for Advertising Bit Error Rate Metric for Traffic Engineering draft-gandhi-lsr-ber-02 Abstract Networks may experience transmission bit errors due to various factors, such as poor fiber quality. This document describes extensions to IS-IS, OSPF, and BGP-LS to advertise the Bit Error Rate (BER) and Packet Error Rate (PER) metrics for the links that can be used for Traffic Engineering. Note that mechanisms for measuring bit errors or acting on that information, once advertised, 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. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet- Drafts is at https://datatracker.ietf.org/drafts/current/. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." This Internet-Draft will expire on 19 January 2027. Copyright Notice Copyright (c) 2026 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. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components Gandhi Expires 19 January 2027 [Page 1] Internet-Draft IS-IS, OSPF, and BGP-LS BER Extensions July 2026 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. Protocol Extensions . . . . . . . . . . . . . . . . . . . . . 3 4.1. IS-IS Extensions . . . . . . . . . . . . . . . . . . . . 4 4.2. OSPF Extensions . . . . . . . . . . . . . . . . . . . . . 5 4.3. BGP-LS Extensions . . . . . . . . . . . . . . . . . . . . 6 5. Security Considerations . . . . . . . . . . . . . . . . . . . 6 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6 6.1. IS-IS Link Sub-TLVs . . . . . . . . . . . . . . . . . . . 7 6.2. OSPF Link Sub-TLVs . . . . . . . . . . . . . . . . . . . 7 6.3. BGP-LS Link Attribute TLVs . . . . . . . . . . . . . . . 7 7. References . . . . . . . . . . . . . . . . . . . . . . . . . 8 7.1. Normative References . . . . . . . . . . . . . . . . . . 8 7.2. Informative References . . . . . . . . . . . . . . . . . 9 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. [RFC8570] for IS-IS, [RFC7471] for OSPF, and [RFC8571] for BGP-LS, define Traffic Engineering (TE) metrics extensions for advertising latency, loss, and bandwidth 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 TE. Additionally, IS-IS, OSPF and BGP-LS extensions are defined to advertise anomaly state that can be used to avoid the links with anomaly state in path computation. Note that the mechanisms for measuring bit errors or acting on that information, once advertised, are outside the scope of this document. Gandhi Expires 19 January 2027 [Page 2] Internet-Draft IS-IS, OSPF, and BGP-LS BER Extensions July 2026 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 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 TE. Additionally, IS-IS, OSPF, and BGP-LS extensions are defined to advertise anomaly state that can be used to avoid the links with anomaly state in path computation. The PER metric can be added in the existing packet loss metric (instead of using it as a separate metric). However, the PER metric can provide different characteristics of the network, since, 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. However, this does not support anomaly state advertisement. 4. Protocol Extensions IS-IS, OSPF, and BGP-LS extensions are defined to advertise BER and PER metrics as well as anomaly state as follows. A bit: Gandhi Expires 19 January 2027 [Page 3] Internet-Draft IS-IS, OSPF, and BGP-LS BER Extensions July 2026 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 MUST be advertised as 0xFFFF FF. EMA: The BER metric advertised is the exponential moving average (EMA) of the BER in order to suppress the frequent advertisements. Similarly, the PER metric advertised is the exponential moving average (EMA) of the PER. Threshold: The BER metric is only advertised when user-configured threshold is crossed. Similarly, the PER metric is only advertised when user- configured threshold is crossed. 4.1. IS-IS Extensions IS-IS extensions for TE are defined in [RFC8570]. This document extends the sub-TLV structure defined in [RFC8570]. These new sub- TLVs provide ways to advertise network-performance information related to BER and PER. The extensions in this document build on the extensions provided in IS-IS TE [RFC5305] and GMPLS [RFC4203]. This document defines several additional sub-TLVs for the links. Value Description ----- ---------------------------- TBA1 Unidirectional Link BER TBA2 Unidirectional Link PER Example Sub-TLV for advertising BER metric in IS-IS is shown in Figure 1. Gandhi Expires 19 January 2027 [Page 4] Internet-Draft IS-IS, OSPF, and BGP-LS BER Extensions July 2026 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 2 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type | Length=4 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |A| RESERVED | BER | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 1: IS-IS Unidirectional BER Metric Sub-TLV The format of the PER metric sub-TLV is the same as the BER metric sub-TLV. 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 for BER and PER. This document registers new IS-IS TE sub-TLVs in the Sub-TLVs for TLVs 22, 23, 25, 141, 222, and 223. 4.2. OSPF Extensions OSPF extensions for TE are defined in [RFC7471]. This document extends the sub-TLV structure defined in [RFC7471]. These new sub- TLVs provide ways to advertise network-performance information related to BER and PER. This document defines several additional sub-TLVs for the links. Value Description ----- ---------------------------- TBA11 Unidirectional Link BER TBA12 Unidirectional Link PER Example Sub-TLV for advertising BER metric in OSPF is shown in Figure 2. 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 2 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type | Length = 4 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |A| RESERVED | BER | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Gandhi Expires 19 January 2027 [Page 5] Internet-Draft IS-IS, OSPF, and BGP-LS BER Extensions July 2026 Figure 2: OSPF Unidirectional BER Metric Sub-TLV The format of the PER metric sub-TLV is the same as the BER metric sub-TLV. The BER metric advertisement is carried in Application-Specific Link Attributes Sub-TLV [RFC9492], which is advertised in Extended Link Opaque LSAs [RFC7684] for OSPFv2 and E-Router-LSAs [RFC8362] for OSPFv3. 4.3. BGP-LS Extensions The IGP TE metric extensions in BGP - Link State (BGP-LS) advertisement are defined in [RFC8571]. New BGP-LS Link Attribute TLVs are defined for BER and PER. New TLV formats follow the rules defined in [RFC9552]. Value Description ----- ---------------------------- TBA21 Unidirectional Link BER TBA22 Unidirectional Link PER Example TLV for advertising 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 2 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type | Length = 4 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |A| RESERVED | BER | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 3: BGP-LS Unidirectional BER Metric TLV The format of the PER metric TLV is the same as the BER metric TLV. 5. Security Considerations The security considerations specified in [RFC7471], [RFC8570], and [RFC8571] apply to the procedure and extensions defined in this document. 6. IANA Considerations Gandhi Expires 19 January 2027 [Page 6] Internet-Draft IS-IS, OSPF, and BGP-LS BER Extensions July 2026 6.1. IS-IS Link Sub-TLVs IANA maintains the registry for "IS-IS Sub-TLVs for TLVs Advertising Neighbor Information". IANA is requested to allocate the following sub-TLVs for types 22, 23, 25, 141, 222, and 223 from this registry. +=======+=========================+===============+ | Value | Description | Reference | +=======+=========================+===============+ | TBA1 | Unidirectional Link BER | This document | +-------+-------------------------+---------------+ | TBA2 | Unidirectional Link PER | This document | +-------+-------------------------+---------------+ Table 1: IS-IS Sub-TLV Types The new sub-TLVs are also added in the registry "IS-IS Sub-Sub-TLV Codepoints for Application-Specific Link Attributes". 6.2. OSPF Link Sub-TLVs IANA maintains the registry for "Types for sub-TLVs of TE Link TLV" for OSPF. IANA is requested to allocate the following sub-TLVs from this registry. +=======+=========================+===============+ | Value | Description | Reference | +=======+=========================+===============+ | TBA11 | Unidirectional Link BER | This document | +-------+-------------------------+---------------+ | TBA12 | Unidirectional Link PER | This document | +-------+-------------------------+---------------+ Table 2: Types for sub-TLVs of TE Link TLV in OSPF 6.3. BGP-LS Link Attribute TLVs IANA maintains the registry for "BGP-LS NLRI and Attribute TLVs". IANA is requested to allocate the following TLVs from this registry. Gandhi Expires 19 January 2027 [Page 7] Internet-Draft IS-IS, OSPF, and BGP-LS BER Extensions July 2026 +=======+=========================+===============+ | Value | Description | Reference | +=======+=========================+===============+ | TBA21 | Unidirectional Link BER | This document | +-------+-------------------------+---------------+ | TBA22 | Unidirectional Link PER | This document | +-------+-------------------------+---------------+ Table 3: BGP-LS Attribute TLV Types 7. References 7.1. 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, . [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, . [RFC7684] Psenak, P., Gredler, H., Shakir, R., Henderickx, W., Tantsura, J., and A. Lindem, "OSPFv2 Prefix/Link Attribute Advertisement", RFC 7684, DOI 10.17487/RFC7684, November 2015, . [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, May 2017, . [RFC8362] Lindem, A., Roy, A., Goethals, D., Reddy Vallem, V., and F. Baker, "OSPFv3 Link State Advertisement (LSA) Extensibility", RFC 8362, DOI 10.17487/RFC8362, April 2018, . [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, . [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, . Gandhi Expires 19 January 2027 [Page 8] Internet-Draft IS-IS, OSPF, and BGP-LS BER Extensions July 2026 [RFC9492] Psenak, P., Ed., Ginsberg, L., Henderickx, W., Tantsura, J., and J. Drake, "OSPF Application-Specific Link Attributes", RFC 9492, DOI 10.17487/RFC9492, October 2023, . 7.2. Informative References [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, . [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, . [RFC5305] Li, T. and H. Smit, "IS-IS Extensions for Traffic Engineering", RFC 5305, DOI 10.17487/RFC5305, October 2008, . [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, . [RFC9552] Talaulikar, K., Ed., "Distribution of Link-State and Traffic Engineering Information Using BGP", RFC 9552, DOI 10.17487/RFC9552, December 2023, . Acknowledgments TBA. Author's Address Rakesh Gandhi (editor) Cisco Systems, Inc. Canada Email: rgandhi@cisco.com Gandhi Expires 19 January 2027 [Page 9]