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Checking references for intended status: Proposed Standard ---------------------------------------------------------------------------- (See RFCs 3967 and 4897 for information about using normative references to lower-maturity documents in RFCs) No issues found here. Summary: 0 errors (**), 0 flaws (~~), 2 warnings (==), 1 comment (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Network Working Group G. Mirsky 3 Internet-Draft X. Min 4 Intended status: Standards Track ZTE Corp. 5 Expires: August 8, 2021 February 4, 2021 7 Error Performance Measurement in Packet-switched Networks 8 draft-mirsky-ippm-epm-01 10 Abstract 12 This document describes the use of the error performance metric to 13 characterize a packet-switched network's conformance to the pre- 14 defined set of performance objectives. In this document, metrics 15 that characterize error performance in a packet-switched network 16 (PSN) are defined, as well as methods to measure and calculate them. 17 Also, the requirements for an active Operation, Administration, and 18 Maintenance protocol to support the error performance measurement in 19 PSN are discussed, and potential candidate protocols are analyzed. 20 All metrics and measurement methods are equally applicable to 21 underlay and overlay networks. 23 Status of This Memo 25 This Internet-Draft is submitted in full conformance with the 26 provisions of BCP 78 and BCP 79. 28 Internet-Drafts are working documents of the Internet Engineering 29 Task Force (IETF). Note that other groups may also distribute 30 working documents as Internet-Drafts. The list of current Internet- 31 Drafts is at https://datatracker.ietf.org/drafts/current/. 33 Internet-Drafts are draft documents valid for a maximum of six months 34 and may be updated, replaced, or obsoleted by other documents at any 35 time. It is inappropriate to use Internet-Drafts as reference 36 material or to cite them other than as "work in progress." 38 This Internet-Draft will expire on August 8, 2021. 40 Copyright Notice 42 Copyright (c) 2021 IETF Trust and the persons identified as the 43 document authors. All rights reserved. 45 This document is subject to BCP 78 and the IETF Trust's Legal 46 Provisions Relating to IETF Documents 47 (https://trustee.ietf.org/license-info) in effect on the date of 48 publication of this document. Please review these documents 49 carefully, as they describe your rights and restrictions with respect 50 to this document. Code Components extracted from this document must 51 include Simplified BSD License text as described in Section 4.e of 52 the Trust Legal Provisions and are provided without warranty as 53 described in the Simplified BSD License. 55 Table of Contents 57 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 58 2. Conventions used in this document . . . . . . . . . . . . . . 3 59 2.1. Terminology and Acronyms . . . . . . . . . . . . . . . . 3 60 2.2. Requirements Language . . . . . . . . . . . . . . . . . . 3 61 3. Error Performance Metrics . . . . . . . . . . . . . . . . . . 4 62 3.1. Measure Error Performance Metrics . . . . . . . . . . . . 4 63 3.2. Calculate Error Performance Metrics . . . . . . . . . . . 5 64 4. Requirements to EPM . . . . . . . . . . . . . . . . . . . . . 5 65 5. Active OAM Protocol for EPM . . . . . . . . . . . . . . . . . 5 66 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5 67 7. Security Considerations . . . . . . . . . . . . . . . . . . . 6 68 8. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 6 69 9. References . . . . . . . . . . . . . . . . . . . . . . . . . 6 70 9.1. Normative References . . . . . . . . . . . . . . . . . . 6 71 9.2. Informative References . . . . . . . . . . . . . . . . . 6 72 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 6 74 1. Introduction 76 Operations, Administration, and Maintenance (OAM) is a collection of 77 methods to detect, characterize, localize failures in a network, and 78 monitor the network's performance using various measurement methods. 79 Traditionally, the former set of OAM tools identified as Fault 80 Management (FM) OAM. The latter - Performance Monitoring (PM) OAM. 81 Some OAM protocols can be used for both groups of tasks, while some 82 serve one particular group. But regardless of how many OAM protocols 83 are in use, network operators and network users are faced with 84 multiple metrics that characterize the network conditions. This 85 document describes a new component of packet-switched network (PSN) 86 OAM. 88 Error performance measurement (EPM) is a part of an OAM toolset that 89 provides an operator with information related to network measurements 90 for a uni-directional or a bidirectional connection between two 91 systems. In current technology, EPM has been defined only for data 92 communication methods that have a constant bit-rate transmission 93 [ITU.G.826] and not for PSN, where transmissions are statistically 94 random. As a statistically multiplexed network in a PSN, a receiver 95 node does not expect a packet to arrive from a sender node at a 96 specific moment, less from a particular sender. That is what 97 differentiates PSN from networks built on a constant bit-rate 98 transmission, where a stream of bits between two nodes is always 99 present, whether it represents data or not. That provides the 100 receiver with a predictable number of measurements in a series of 101 measurement intervals. In PSN, on-path OAM methods, i.e., 102 measurement methods that use data flow, cannot provide such 103 predictability and thus be used for EPM. In PSN, EPM needs to use 104 active OAM methods, per definition in [RFC7799]. This document 105 identifies metrics that characterize PSN error performance and 106 methods to measure and calculate them. Also, the requirements for an 107 active OAM protocol to support EPM in PSN are discussed, and 108 potential candidate protocols are analyzed. 110 2. Conventions used in this document 112 2.1. Terminology and Acronyms 114 OAM Operations, Administration, and Maintenance 116 EP Error Performance 118 EPM Error Performance Measurement 120 ES Errored Second 122 ESR Errored Second Ratio 124 SES Severely Errored Second 126 SESR Severely Errored Second Ratio 128 EFS Error-Free Second 130 PSN Packet-switched Network 132 FM Fault Management 134 PM Performance Monitoring 136 2.2. Requirements Language 138 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 139 "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and 140 "OPTIONAL" in this document are to be interpreted as described in BCP 141 14 [RFC2119] [RFC8174] when, and only when, they appear in all 142 capitals, as shown here. 144 3. Error Performance Metrics 146 When analyzing the error performance of a path between two nodes, we 147 need to select a time interval as the unit of EPM. In [ITU.G.826], a 148 time interval of one second is used. It is reasonable to use the 149 same time interval for EPM for PSNs. Further, for the purpose of 150 EPM, each time interval, i.e., second, is classified either as 151 Errored Second (ES), Severely Errored Second (SES), or Error-Free 152 Second (EFS). These are defined as follows: 154 o An ES is a time interval during which at least one of the 155 performance parameters degraded below its optimal level threshold 156 or a defect was detected. 158 o An SES is a time interval during which at least one the 159 performance parameters degraded below its critical threshold or a 160 defect was detected. 162 o Consequently, an EFS is a time interval during which all 163 performance objectives are at or above their respective optimal 164 levels, and no defect has been detected. 166 The definition of a state of a defect in the network is also 167 necessary for understanding the EPM. In this document, the defect is 168 interpreted as the state of inability to communicate between a 169 particular set of nodes. It is important to note that it is being 170 defined as a state, and thus, it has conditions that define entry 171 into it and exit out of it. Also, the state of defect exists only in 172 connection to the particular group of nodes in the network, not the 173 network as a domain. 175 3.1. Measure Error Performance Metrics 177 The definitions of ES, SES, and EFS allow for characterization of the 178 communication between two nodes relative to the level of required and 179 acceptable performance and when performance degrades below the 180 acceptable level. The former condition in this document referred to 181 as network availability. The latter - network unavailability. Based 182 on the definitions, SES is the one-second of network unavailability 183 while ES and EFS present an interval of network availability. But 184 since the conditions of network are everchanging periods of network 185 availability and unavailability need to be defined with duration 186 larger than one-second interval to reduce the number of state changes 187 while correctly reflecting the network condition. The method to 188 determine the state of the network in terms of EPM OAM is described 189 below: 191 o If ten consecutive SES intervals been detected, then the EPM state 192 of the network determined as unavailability and the beginning of 193 that period of unavailability state is at the start of the first 194 SES in the sequence of the consecutive SES intervals. 196 o Similarly, ten consecutive non-SES intervals, i.e., either ES or 197 EFS, indicate that the network is in the availability period, 198 i.e., available. The start of that period is at the beginning of 199 the first non-SES interval. 201 o Resulting from these two definitions, a sequence of less than ten 202 consecutive SES or non-SES intervals does not change the EPM state 203 of the network. For example, if the EPM state is determined as 204 unavailability a sequence of seven EFS intervals is not viewed as 205 an availability period. 207 3.2. Calculate Error Performance Metrics 209 Determining the period in which the path is currently EP-wise is 210 helpful. But because switching between periods requires ten 211 consecutive one-second intervals, conditions that last shorter 212 intervals may not be adequately reflected. Two additional EP OAM 213 metrics can be used, and they are defined as follows: 215 o errored second ratio (ESR) is the ratio of ES to the total number 216 of seconds in a time of the availability periods during a fixed 217 measurement interval. 219 o severely errored second ratio (SESR) - is the ratio of SES to the 220 total number of seconds in a time of the availability periods 221 during a fixed measurement interval. 223 4. Requirements to EPM 225 TBA 227 5. Active OAM Protocol for EPM 229 TBA 231 6. IANA Considerations 233 TBA 235 7. Security Considerations 237 TBA 239 8. Acknowledgments 241 TBA 243 9. References 245 9.1. Normative References 247 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 248 Requirement Levels", BCP 14, RFC 2119, 249 DOI 10.17487/RFC2119, March 1997, 250 . 252 [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 253 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 254 May 2017, . 256 9.2. Informative References 258 [ITU.G.826] 259 ITU-T, "End-to-end error performance parameters and 260 objectives for international, constant bit-rate digital 261 paths and connections", ITU-T G.826, December 2002. 263 [RFC7799] Morton, A., "Active and Passive Metrics and Methods (with 264 Hybrid Types In-Between)", RFC 7799, DOI 10.17487/RFC7799, 265 May 2016, . 267 Authors' Addresses 269 Greg Mirsky 270 ZTE Corp. 272 Email: gregimirsky@gmail.com 274 Xiao Min 275 ZTE Corp. 277 Email: xiao.min2@zte.com.cn