ICCRG Jaehwoon Lee Internet-Draft Dongguk University Intended status: Informational Chongho Yoon Expires: July 30, 2020 Korea Aerospace University January 31, 2020 Gated Adaptive CoDel for Time-Sensitive Network draft-jaehwoon-icc-gacodel-00 Abstract This draft proposes a gated adaptive CoDel algorithm that can operate in the Time-Sensitive Network (TSN) environment. Here, we define Virtual sojourn time, virtual Interval and virtaul Target that are only operate on non-blocking part of TSN. 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 http://datatracker.ietf.org/drafts/current/. 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Jaehwoon Lee Expires July 30, 2020 [Page 1] Internet-Draft Gated Adaptive CoDel for TSN Jan. 31, 2020 Table of Contents 1. Introduction.................................................2 2. Conventions and Terminology..................................3 2.1. Conventions used in this document........................3 2.2. Terminology ............................................3 3. Gated adaptive Codel for TSN.................................3 4. Security Considerations......................................3 5. IANA Considerations..........................................3 6. References....................................................4 Author's Address.................................................4 1. Introduction Bufferbloat means that there are excess number of packets stored in the buffer in the bottleneck part of the packet-switched network. End-to-end latency, therefore, increases sharply due to the bufferbloat[1]. CoDel AQM is one of the active queue management (AQM) technique used to resolve the bufferbloat problem[2]. When a packet enters the buffer, CoDel records the current time in the packet by using the timestamp and computes the sojourn time on dequeue. Sojourn time, together with the initial INTERVAL and TARGET values set by the user, is used to determine whether to discard the packet or not. Time-sensitive network (TSN) provides the deterministic arrival service without delay for time-sensitive control traffic based on the time triggered scheduling that is synchronized with the Time Triggered Ethernet (TTE)[3-4]. In TSN, time is considered to be slotted. Each slot is further divided into two minislots. The first minislot is used to transmit time-sensitive control traffic. The other is used to transmit asynchronous traffic. In other words, from the point of view of asynchronous traffic, the gate is periodically blocked at the time interval is assigned to the time-sensitive control traffic. TSN provides reasonable scheduling to asynchronous traffic through credit based shaper and strict priority algorithm[5]. However, as the size of the first mini slot gets larger, the bandwidth for asynchronous traffic decreases, and bufferbloat phenomenon worsens . CoDel can resolve the bufferbloat problem that may occur when transmitting the asynchronous traffic in TSN environment. In this case, gated scheduler asks CoDel whether to transmit the packet based on timing and scheduling information. When the packet can be transmitted without being discarded, gated Jaehwoon Lee Expires July 30, 2020 [Page 2] Internet-Draft Gated Adaptive CoDel for TSN Jan. 31, 2020 scheduler can transmit the packet during the time slot assigned to the asynchronous traffic. Codel decides whether to discard the packet on dequeue. When the gate is blocked, packets can arrive and be stored in the buffer anytime. However, packet that is stored in the buffer cannot be transmitted during the first minislot. It means that the codel algorithm will not work and stop running when the gate is blocked. Therefore when applying codel to TSN, it is necessary to consider the fact that gate is periodically blocked. In this draft, we propose gated adaptive codel aqm to resolve the bufferbloat problem arising from asynchronous traffic transmitted during the non-blocking period in the TSN environment. 2. Conventions and Terminology 2.1. Conventions The key words "MUST", "MUST NOT", "REQUIRED", "SHALL","SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in RFC 2119 [6]. 2.2 Terminology TBD 3. Gated Adaptive CoDel for TSN In this section, we define a virtual time that only operates on the non-blocking period. It is independent of actual time used in the CoDel packet discarding algorithm. Here, packets that arrive during a blocked period are regarded as having arrived at the same time, while the order of arrival is maintained. Virtual sojourn time is defined as the actual sojourn time minus the blocking period. Moreover, the Virtual TARGET and Virtual INTERVAL should be calculated as follows and used in the codel algorithm. VirtualTARGET = ActualTARGET - GatedBlockingPeriod VirtualINTERVAL = ActualINTERVAL * (1-Blocking Period)/Gated Period. 4. Security Considerations TBD 5. IANA Considerations TBD Jaehwoon Lee Expires July 30, 2020 [Page 3] Internet-Draft Gated Adaptive CoDel for TSN Jan. 31, 2020 6. References [1] G. Jim and K. Nichols, "Bufferbloat: Dark buffers in the Internet", Queue9.11, pp. 40, 2011 [2] K. Nichols, V. Jacobson, A. McGregor and J. Iyengar, "Controlled Delay Active Queue Management, RFC 8289, Jan. 2018. [3] Institute of Electrical and Electronices Engineers, Time-Sensitive Networking Task Group. http://www.ieee802.org/1/pages/tsn.html, 2016. [4] K. Hermann and G. Grunsteidl,"TTP-A time-triggered protocol for fault-tolerant real-time systems", Fault-Tolerant Computing, 1993. FTCS-23. Digest of Papers, The Twenty-Third International Symposium on IEEE, 1993. [5] IEEE 802.1 AVB Task Group, "IEEE 802.1Qav - Virtual Bridged Local Area Networks - Amendment: Forwarding and Queuing Enhancements for Time-Sensitive Streams", 2009. [6] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. Author's Address Jaehwoon Lee Dongguk University 26, 3-ga Pil-dong, Chung-gu Seoul 100-715, KOREA Email: jaehwoon@dongguk.edu Chongho Yoon Korea Aerospace University 76, Hanggongdaehak-ro, Deogyang-gu, Goyang-si, Gyeonggi-do, 10540, KOREA Email: yoonch@kau.ac.kr Jaehwoon Lee Expires July 30, 2020 [Page 4]