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Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 1 ICCRG Jaehwoon Lee 2 Internet-Draft Dongguk University 3 Intended status: Informational Chongho Yoon 4 Expires: July 30, 2020 Korea Aerospace University 5 January 31, 2020 7 Gated Adaptive CoDel for Time-Sensitive Network 8 draft-jaehwoon-icc-gacodel-00 10 Abstract 12 This draft proposes a gated adaptive CoDel algorithm that can operate 13 in the Time-Sensitive Network (TSN) environment. Here, we define 14 Virtual sojourn time, virtual Interval and virtaul Target that are 15 only operate on non-blocking part of TSN. 17 Status of this Memo 19 This Internet-Draft is submitted in full conformance with the 20 provisions of BCP 78 and BCP 79. 22 Internet-Drafts are working documents of the Internet Engineering 23 Task Force (IETF). Note that other groups may also distribute 24 working documents as Internet-Drafts. The list of current Internet- 25 Drafts is at http://datatracker.ietf.org/drafts/current/. 27 Internet-Drafts are draft documents valid for a maximum of six months 28 and may be updated, replaced, or obsoleted by other documents at any 29 time. It is inappropriate to use Internet-Drafts as reference 30 material or to cite them other than as "work in progress." 32 This Internet-Draft will expire on July 30, 2020. 34 Copyright Notice 36 Copyright (c) 2020 IETF Trust and the persons identified as the 37 document authors. All rights reserved. 39 This document is subject to BCP 78 and the IETF Trust's Legal 40 Provisions Relating to IETF Documents 41 (http://trustee.ietf.org/license-info) in effect on the date of 42 publication of this document. Please review these documents 43 carefully, as they describe your rights and restrictions with respect 44 to this document. Code Components extracted from this document must 45 include Simplified BSD License text as described in Section 4.e of 46 the Trust Legal Provisions and are provided without warranty as 47 described in the Simplified BSD License. 49 Table of Contents 51 1. Introduction.................................................2 52 2. Conventions and Terminology..................................3 53 2.1. Conventions used in this document........................3 54 2.2. Terminology ............................................3 55 3. Gated adaptive Codel for TSN.................................3 56 4. Security Considerations......................................3 57 5. IANA Considerations..........................................3 58 6. References....................................................4 59 Author's Address.................................................4 61 1. Introduction 63 Bufferbloat means that there are excess number of packets stored in 64 the buffer in the bottleneck part of the packet-switched network. 65 End-to-end latency, therefore, increases sharply due to the 66 bufferbloat[1]. CoDel AQM is one of the active queue management (AQM) 67 technique used to resolve the bufferbloat problem[2]. When a packet 68 enters the buffer, CoDel records the current time in the packet by 69 using the timestamp and computes the sojourn time on dequeue. Sojourn 70 time, together with the initial INTERVAL and TARGET values set by the 71 user, is used to determine whether to discard the packet or not. 73 Time-sensitive network (TSN) provides the deterministic arrival 74 service without delay for time-sensitive control traffic based on the 75 time triggered scheduling that is synchronized with the Time 76 Triggered Ethernet (TTE)[3-4]. In TSN, time is considered to be 77 slotted. Each slot is further divided into two minislots. The first 78 minislot is used to transmit time-sensitive control traffic. The 79 other is used to transmit asynchronous traffic. In other words, from 80 the point of view of asynchronous traffic, the gate is periodically 81 blocked at the time interval is assigned to the time-sensitive 82 control traffic. TSN provides reasonable scheduling to asynchronous 83 traffic through credit based shaper and strict priority algorithm[5]. 84 However, as the size of the first mini slot gets larger, the 85 bandwidth for asynchronous traffic decreases, and bufferbloat 86 phenomenon worsens . CoDel can resolve the bufferbloat problem that 87 may occur when transmitting the asynchronous traffic in TSN 88 environment. In this case, gated scheduler asks CoDel whether to 89 transmit the packet based on timing and scheduling information. When 90 the packet can be transmitted without being discarded, gated 91 scheduler can transmit the packet during the time slot assigned to 92 the asynchronous traffic. Codel decides whether to discard the packet 93 on dequeue. When the gate is blocked, packets can arrive and be 94 stored in the buffer anytime. However, packet that is stored in the 95 buffer cannot be transmitted during the first minislot. It means 96 that the codel algorithm will not work and stop running when the gate 97 is blocked. Therefore when applying codel to TSN, it is necessary to 98 consider the fact that gate is periodically blocked. 100 In this draft, we propose gated adaptive codel aqm to resolve the 101 bufferbloat problem arising from asynchronous traffic transmitted 102 during the non-blocking period in the TSN environment. 104 2. Conventions and Terminology 106 2.1. Conventions 108 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL","SHALL NOT", 109 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 110 document are to be interpreted as described in RFC 2119 [6]. 112 2.2 Terminology 114 TBD 116 3. Gated Adaptive CoDel for TSN 118 In this section, we define a virtual time that only operates on the 119 non-blocking period. It is independent of actual time used in the 120 CoDel packet discarding algorithm. Here, packets that arrive during a 121 blocked period are regarded as having arrived at the same time, while 122 the order of arrival is maintained. Virtual sojourn time is defined 123 as the actual sojourn time minus the blocking period. Moreover, the 124 Virtual TARGET and Virtual INTERVAL should be calculated as follows 125 and used in the codel algorithm. 127 VirtualTARGET = ActualTARGET - GatedBlockingPeriod 128 VirtualINTERVAL = ActualINTERVAL * (1-Blocking Period)/Gated Period. 130 4. Security Considerations 132 TBD 134 5. IANA Considerations 136 TBD 138 6. References 140 [1] G. Jim and K. Nichols, "Bufferbloat: Dark buffers in the 141 Internet", Queue9.11, pp. 40, 2011 143 [2] K. Nichols, V. Jacobson, A. McGregor and J. Iyengar, "Controlled 144 Delay Active Queue Management, RFC 8289, Jan. 2018. 146 [3] Institute of Electrical and Electronices Engineers, 147 Time-Sensitive Networking Task Group. 148 http://www.ieee802.org/1/pages/tsn.html, 2016. 150 [4] K. Hermann and G. Grunsteidl,"TTP-A time-triggered 151 protocol for fault-tolerant real-time systems", 152 Fault-Tolerant Computing, 1993. FTCS-23. Digest of Papers, 153 The Twenty-Third International Symposium on IEEE, 1993. 155 [5] IEEE 802.1 AVB Task Group, "IEEE 802.1Qav - Virtual 156 Bridged Local Area Networks - Amendment: Forwarding and 157 Queuing Enhancements for Time-Sensitive Streams", 2009. 159 [6] Bradner, S., "Key words for use in RFCs to Indicate 160 Requirement Levels", BCP 14, RFC 2119, March 1997. 162 Author's Address 164 Jaehwoon Lee 165 Dongguk University 166 26, 3-ga Pil-dong, Chung-gu 167 Seoul 100-715, KOREA 168 Email: jaehwoon@dongguk.edu 170 Chongho Yoon 171 Korea Aerospace University 172 76, Hanggongdaehak-ro, Deogyang-gu, Goyang-si, 173 Gyeonggi-do, 10540, KOREA 174 Email: yoonch@kau.ac.kr