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 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 28 September 2026. Ruan, et al. Expires 28 September 2026 [Page 1] Internet-Draft IS-IS Traffic Engineering Extensions For March 2026 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 Ruan, et al. Expires 28 September 2026 [Page 2] Internet-Draft IS-IS Traffic Engineering Extensions For March 2026 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). Ruan, et al. Expires 28 September 2026 [Page 3] Internet-Draft IS-IS Traffic Engineering Extensions For March 2026 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) Ruan, et al. Expires 28 September 2026 [Page 4] Internet-Draft IS-IS Traffic Engineering Extensions For March 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | 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. Ruan, et al. Expires 28 September 2026 [Page 5] Internet-Draft IS-IS Traffic Engineering Extensions For March 2026 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. Ruan, et al. Expires 28 September 2026 [Page 6] Internet-Draft IS-IS Traffic Engineering Extensions For March 2026 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, . Ruan, et al. Expires 28 September 2026 [Page 7] Internet-Draft IS-IS Traffic Engineering Extensions For March 2026 [RFC5304] Li, T. and R. Atkinson, "IS-IS Cryptographic Authentication", RFC 5304, DOI 10.17487/RFC5304, October 2008, . [RFC5305] Li, T. and H. Smit, "IS-IS Extensions for Traffic Engineering", RFC 5305, DOI 10.17487/RFC5305, October 2008, . [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, May 2017, . [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, . 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 Ruan, et al. Expires 28 September 2026 [Page 8] Internet-Draft IS-IS Traffic Engineering Extensions For March 2026 Zhengxin Han China Unicom Beijing China Email: hanzx21@chinaunicom.cn Ruan, et al. Expires 28 September 2026 [Page 9]