



lsr                                                         Z. Ruan, Ed.
Internet-Draft                                              R. Pang, Ed.
Intended status: Standards Track                                   X. Yi
Expires: 28 September 2026                                        M. Han
                                                                  Z. Han
                                                            China Unicom
                                                           27 March 2026


          IS-IS Traffic Engineering Extensions For Microburst
          draft-ruan-lsr-isis-te-extensions-for-microburst-00

Abstract

   This document defines a new IS-IS sub-TLV to advertise microburst-
   related statistics on links, serving as a supplement to RFC 8570(IS-
   IS Traffic Engineering (TE) Metric Extensions).  RFC 8570 specifies
   steady-state TE performance metrics (e.g., latency, jitter, packet
   loss) but does not cover microburst-related information, which this
   document intends to address.  Microbursts are short-duration, high-
   intensity traffic bursts that can cause transient congestion,
   increased latency, jitter, and packet loss, which are critical issues
   for latency-sensitive services.  The proposed sub-TLV carries
   aggregated microburst statistics on a per-traffic-class basis,
   including total burst count, burst-induced drop metrics, and a
   configurable measurement interval, along with an Anomalous (A) bit to
   indicate abnormal microburst conditions.  This extension enhances IS-
   IS Traffic Engineering capabilities by advertising link microburst
   statistics,enabling improved traffic engineering and path selection
   decisions for traffic.

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
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   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 28 September 2026.




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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
   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
     1.1.  Background  . . . . . . . . . . . . . . . . . . . . . . .   2
     1.2.  Requirements Analysis . . . . . . . . . . . . . . . . . .   3
     1.3.  Requirements Language . . . . . . . . . . . . . . . . . .   4
   2.  Unidirectional Microburst Statistics Sub-TLV Definition . . .   4
   3.  Measurement and Advertisement Rules . . . . . . . . . . . . .   6
     3.1.  Measurement Rules . . . . . . . . . . . . . . . . . . . .   6
     3.2.  Advertisement Rules . . . . . . . . . . . . . . . . . . .   6
   4.  Security Considerations . . . . . . . . . . . . . . . . . . .   7
   5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   7
   6.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   7
     6.1.  Normative References  . . . . . . . . . . . . . . . . . .   7
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   8

1.  Introduction

1.1.  Background

   Latency-sensitive applications (e.g., 5G bearer networks, financial
   market data transmission, industrial control systems) have rapidly
   evolved, imposing increasingly stringent requirements on network
   performance.  Unlike traditional best-effort services, these
   applications are highly sensitive to transient network anomalies—even
   short-duration congestion or packet loss can severely degrade service
   quality.

   RFC 8570 defines steady-state Traffic Engineering (TE) metrics (e.g.,
   latency, jitter, packet loss) for IS-IS, which effectively
   characterize long-term link performance but fail to address
   microbursts.  Microbursts are short-duration, high-intensity traffic
   bursts that cause transient congestion, latency spikes, jitter, and
   packet loss—even when average link utilization remains low.  This gap



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   in RFC 8570 means network operators lack visibility into microburst-
   related issues when making TE path selection decisions, which can
   hinder performance optimization for latency-sensitive services.

   To fill this gap, this document extends RFC 8570 by adding microburst
   visibility to the IS-IS TE framework, while adhering to RFC 8570's
   core design principles for backward compatibility and
   interoperability.

   Modern network devices now include hardware-level capabilities to
   monitor microbursts with high precision: millisecond (ms)-level
   sampling of port/queue traffic enables accurate detection of
   microbursts, without the need for active probe packets (e.g., ICMP/
   TWAMP) that introduce extra bandwidth overhead or probe-induced
   interference.  This native hardware support makes it feasible to
   collect aggregated microburst statistics and advertise them via a new
   IS-IS sub-TLV—enabling data-driven TE path selection for latency-
   sensitive services.

1.2.  Requirements Analysis

   The primary motivation for this extension is to address the
   limitations of existing IS-IS TE metrics by providing microburst
   visibility, enabling two key use cases that are critical for modern
   network operations.

   First, for latency and jitter-sensitive services (e.g., financial
   data feeds, 5G real-time services, and industrial control signals),
   path selection must prioritize links with minimal microburst
   activity.  Microbursts can cause transient spikes in latency and
   jitter, which are unacceptable for these services.  By advertising
   microburst statistics via IS-IS, Node or controller can prune links
   with frequent or severe microbursts from path calculations, ensuring
   that latency-sensitive traffic is routed over stable, low-burst
   links.

   Second, for non-urgent, best-effort (BE) traffic (e.g., system
   updates, massive file transfers, and non-critical background tasks),
   network operators need the ability to throttle or pause such traffic
   when microbursts on a link increase.

   To address these requirements, the proposed extension must meet the
   following key criteria:

   a.Carry aggregated microburst statistics to avoid excessive IS-IS
   flooding (microbursts are real-time events but must not be advertised
   per-event).




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   b.Be compatible with existing IS-IS TE extensions and non-supporting
   nodes (which should ignore the new sub-TLV), in accordance with IS-IS
   processing rules.

   c.Provide actionable metrics that are engineering-feasible to measure
   and useful for path selection and traffic management.

1.3.  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.  Unidirectional Microburst Statistics Sub-TLV Definition

   A microburst is defined as a transient, high-intensity traffic burst
   that causes instantaneous queue occupancy for a specific traffic
   class to exceed a locally configured threshold.  Microbursts can have
   significant negative impacts on network performance, including
   transient congestion, unexpected packet loss, latency spikes, and
   increased jitter-even when average link utilization remains low,
   which can severely degrade the quality of latency-sensitive services
   such as 5G real-time services and financial data transmission.

   This document defines a new IS-IS sub-TLV, the Microburst Statistics
   Sub-TLV, which is advertised within IS-IS TLVs 22 (Extended IS
   Reachability), 222 (Extended IS Reachability for IPv6), 23 (IS
   Neighbor Reachability), 223 (IS Neighbor Reachability for IPv6), 141
   (AS Level Reachability), and 25 (Protocols Supported).  For each
   link, multiple Microburst Statistics Sub-TLVs may be included (one
   per traffic class, as microbursts are class-isolated)


















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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   |      TC       |     Interval                  |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                 Total Microburst Count                        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                 Total Microburst Drop Count                   |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                 Max Drop Per Burst
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                 Total Drop Count                              |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |           Max Queue Depth     | Avg Queue Occupancy           |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

               Figure 1: Microburst Statistics Sub-TLV Format

   The Microburst Statistics Sub-TLV is structured as an IS-IS TE sub-
   TLV, with the following fields defined below:

   Type : To Be Determined (TBD) by IANA.

   A bit: This field represents the Anomalous (A) bit.  The A bit is set
   when the measured total microburst count value 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.

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

   Length : 24.

   TC : Traffic Class.  Indicates the traffic class to which the
   microburst statistics apply (0-255), commonly 0-255.

   Interval : Measurement interval (in seconds), during which microburst
   statistics are sampled and aggregated.  The interval is configurable
   per node/link.

   Total Microburst Count : Total number of microbursts detected on the
   link for the specified TC during the measurement interval.






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   Total Microburst Drop Count : Number of microbursts that caused
   packet loss on the link for the specified TC during the measurement
   interval.

   Max Drop Per Burst : Maximum number of packets lost during a single
   microburst event for the specified TC during the measurement
   interval.  This metric is useful for quantifying the severity of
   individual microburst events.

   Total Drop Count : Total number of packets lost due to all microburst
   events for the specified TC during the measurement interval.  This
   metric provides a cumulative measure of microburst impact.

   Max Queue Depth : Maximum queue depth (in bytes) observed on the link
   for the specified TC at the time microburst-induced packet loss
   occurred.  This metric directly reflects the queue accumulation level
   that triggered drop events during microbursts.

   Avg Queue Occupancy : Average queue occupancy in bytes for the TC
   during the measurement interval.

3.  Measurement and Advertisement Rules

3.1.  Measurement Rules

   a.  Microburst statistics MUST be sampled and aggregated over the
   configured interval.Microbursts MUST NOT be advertised on a per-event
   basis, as this would cause excessive IS-IS LSP flooding and network
   instability.

   b.  Microburst detection and measurement can be performed per-
   traffic-class, as different traffic classes are isolated in separate
   queues and experience microbursts independently.

   c.  The queue occupancy threshold for microburst detection is
   configurable per node/link, but SHOULD be consistent across the
   network to ensure consistent statistics interpretation.

   d.  Packet loss attributed to microbursts MUST be distinguished from
   loss due to other causes (e.g., link errors) to ensure accurate
   measurement of microburst impact.

3.2.  Advertisement Rules

   a.  For each link, burst detection can be configured on demand for
   different TC, and the detection results are transmitted
   independently.




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   b.  Under normal conditions, the sub-TLV MUST be advertised once per
   measurement interval,regardless of the number of microbursts
   detected.However, if microburst statistics change abruptly,the node
   MUST advertise the updated sub-TLV immediatelywithout waiting for the
   end of the interval.

   c.  If a node receives multiple Microburst Statistics Sub-TLVs for
   the same link, same TC, and same measurement Interval, it SHOULD
   select the first advertisement in the lowest-numbered LSP.

   d.  Nodes that do not recognize the Microburst Statistics Sub-TLV
   MUST ignore it, in accordance with IS-IS processing rules (RFC 8918),
   ensuring backward compatibility with existing networks.

4.  Security Considerations

   The Microburst Statistics Sub-TLV does not introduce new security
   risks beyond those already present in IS-IS TE extensions (RFC 5305,
   RFC 8570).  False or malicious advertisement of microburst statistics
   could lead to incorrect path selection or traffic management
   decisions.  To mitigate this risk, IS-IS authentication (RFC 5304)
   SHOULD be enabled to ensure the integrity and authenticity of LSPs
   containing the Microburst Statistics Sub-TLV, consistent with IETF
   security best practices for IS-IS extensions.

5.  IANA Considerations

   IANA is requested to assign a Type value for the Microburst
   Statistics Sub-TLV in the IS-IS Traffic Engineering Sub-TLVs registry
   (under the "IS-IS Sub-TLVs" heading).  The recommended Type value is
   TBD (to be assigned by IANA), following the registration process
   defined in RFC 5305 for IS-IS TE sub-TLVs.

                 Type   Description
                ----------------------------------------------------
                 TBD    Unidirectional Microburst statistics

    Figure 2: IS-IS TE Sub-TLV Type Assignment for Microburst Statistics

6.  References

6.1.  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>.




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   [RFC5304]  Li, T. and R. Atkinson, "IS-IS Cryptographic
              Authentication", RFC 5304, DOI 10.17487/RFC5304, October
              2008, <https://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, <https://www.rfc-editor.org/info/rfc5305>.

   [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>.

Authors' Addresses

   Zheng Ruan (editor)
   China Unicom
   Beijing
   China
   Email: ruanz6@chinaunicom.cn


   Ran Pang (editor)
   China Unicom
   Beijing
   China
   Email: pangran@chinaunicom.cn


   Xinxin Yi
   China Unicom
   Beijing
   China
   Email: yixx3@chinaunicom.cn


   MengYao Han
   China Unicom
   Beijing
   China
   Email: hanmy12@chinaunicom.cn






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   Zhengxin Han
   China Unicom
   Beijing
   China
   Email: hanzx21@chinaunicom.cn














































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