6LoWPAN Working Group P. Wang Internet Draft H. Wang Interned status: Standards Track G. Ge Expires: Dec 11,2011 Chongqing University of Posts and Telecommunications June 28,2011 Industrial Scheduling Requirements for Transmission of IPv6 Packets over IEEE 802.15.4 Networks draft-wang-6lowpan-scheduling-requirements-00.txt Abstract Industrial automation field either process automation or factory automation has its special characteristics and requirements because of the crucial environment and the safety of industrial production itself. 6LoWPAN working group standard Rfc4944 "Transmission of IPv6 Packets over IEEE 802.15.4 Networks" introduces the methods of transmitting IPv6 packets over IEEE 802.15.4 networks. This document describes the function requirements of industrial scheduling for transmission of IPv6 packets over IEEE 802.15.4 networks to extend the 6LoWPAN resolution method for industrial application space. Status of this Memo This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79. This document may not be modified, and derivative works of it may not be created, except to publish it as an RFC and to translate it into languages other than English. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet- Drafts. 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." The list of current Internet-Drafts can be accessed at http://www.ietf.org/ietf/1id-abstracts.txt The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html This Internet-Draft will expire on December 28, 2011. Wang, et al. Expires Dec 11, 2011 [Page 1] Internet-Draft ietf-6lowpan-Scheduling-requirements June 2011 Copyright Notice Copyright (c) 2011 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 (http://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. Table of Contents 1. Introduction...................................................2 1.1. Requirements Language.....................................3 1.2. Terms Used................................................3 2. Overview.......................................................3 2.1. Industrial requirements...................................3 2.2. Data features and QoS.....................................5 3. Determinism requirements.......................................7 4. Reliability requirements.......................................7 5. Real-time requirements.........................................8 6. Low power requirements.........................................9 7. Security Considerations.......................................10 8. IANA Considerations...........................................10 9. Acknowledgments...............................................10 10. References...................................................10 10.1. Normative References....................................10 10.2. Informative References..................................11 1. Introduction The development of industrial wireless technology encourages Internet communities to integrate wireless technology into mature IP technology with mutual advantages. IEEE 802.15.4 standard and minimum Internet protocol stack uIP etc make 6LoWPAN(IPv6 over Low power Wireless Personal Area Networks) technology arises at the historic moment. In industrial application space 6LoWPAN has technological advancements that doesn't exist in Zigbee WIA-PA ISA100 and Wireless-HART. It is important to improve 6LoWPAN standard for industrial application space. IETF 6LoWPAN work group RFC4944 "Transmission of IPv6 Packet over IEEE 802.15.4 Networks" has described the frame format for transmission of IPv6 packet and the method of forming IPv6 link- Wang, et al. Expires Dec 11, 2011 [Page 2] Internet-Draft ietf-6lowpan-Scheduling-requirements June 2011 local addresses and stateless auto-configured addresses on IEEE 802.15.4 networks. IETF ROLL (Routing Over Low power and Lossy networks) work group has presented a Ripple routing protocol for Low power and Lossy networks. Other relative work group includes 6LoWAPP for application exploration. But there are still not a IETF 6LoWPAN RFC focusing on the industrial scheduling requirements which is a MUST function in industrial application area. Either ISA100.11a or IEEE 802.15.4e takes deterministic schedule as a top priority. So the aim of this document is to analyze the requirements from the industrial environment for a scheduling protocol in 6LoWPAN networks. 1.1. Requirements Language 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 [RFC2119]. 1.2. Terms Used BO: Beacon Order CAP: Contention Access Period CFP: Contention-Free Period SAB: Slot Allocation Bitmap LLDN: Low Latency Deterministic Network ASN: Absolute Slot Number TDMA: Time Division Multiple Address 2. Overview Industrial field environment has many special requirements for wireless technology, once malfunction, there will result in great economic loss, even seriously, lost lives. This section introduces the specific industrial requirement and the important features and function of industrial wireless technology. 2.1. Industrial requirements Industrial automation is segmented into two distinct application spaces, known as "process" or "process control" and "discrete Wang, et al. Expires Dec 11, 2011 [Page 3] Internet-Draft ietf-6lowpan-Scheduling-requirements June 2011 manufacturing" or "factory automation". In industrial process control, the product is typically a fluid (oil, gas, chemicals, etc.). In factory automation or discrete manufacturing, the products are individual elements (screws, cars, dolls). While there are some overlap of products and systems between these two segments, they are surprisingly separate communities. The specifications targeting industrial process control tend to have more tolerance for network latency than what is needed for factory automation. The industrial market classifies process applications into three broad categories and six classes. o Safety * Class 0: Emergency action-Always a critical function o Control * Class 1: Closed-loop regulatory control-Often a critical function * Class 2: Closed-loop supervisory control-Usually a noncritical function * Class 3: Open-loop control-Operator takes action and controls the actuator (human in the loop) o Monitoring * Class 4: Alerting-Short-term operational effect (for example, event-based maintenance) * Class 5: Logging and downloading/uploading-No immediate operational consequence (e.g., history collection,sequence-of events, preventive maintenance) Industrial wireless control networks system usually needs the following requirements: - high determinism, - high reliability, - low latency, i.e. transmission of sensor date in 10ms, - low round trip time, Wang, et al. Expires Dec 11, 2011 [Page 4] Internet-Draft ietf-6lowpan-Scheduling-requirements June 2011 - support for many sensors per LLDN PAN coordinator, - resisting disturbance, i.e. reject bad channel and channel hop. 2.2. Data features and QoS In industrial wireless network, the data link layer usually uses IEEE 802.15.4 low data rate wireless personal area network standard. There is usually small amount of data and large period of data transmission in practical industrial applications. Quality of service is defined as the sum of features and characteristics which meet the requirements of service and potential demands, referring to the extent that the service meets the needs of service providers. In communication networks, the QoS indicators are as follows: deterministic, real-time, reliability, low latency, low power consumption, etc. Application data can be classified according to the following methods: 2.2.1. It can be divided into periodic data and aperiodic data according to the period of data transmission. Periodic data is generally normal application data, which has lower quality of service requirements and is sent more regularly, so it can be used a centralized scheduling and pre-arranged the necessary resources. Aperiodic data is generally used to the management service or the alarm service. It requires a higher quality of service. It has to set aside separate resources in order to ensure the quality of service for aperiodic data because there is no fixed sending period. 2.2.2. It can be divided into general data, management data and alarm data according to the urgency of the data. General data generally refer to the data which collected by sensors or environmental monitoring data. It has smaller amount of data and is sent periodically, so it can use a centralized scheduling, which can allocate resources rationally based on the pre-data transmission period. Management data is generally used for network management and security management services. It manages the network using the uploading and downloading application service. This kind of data has Wang, et al. Expires Dec 11, 2011 [Page 5] Internet-Draft ietf-6lowpan-Scheduling-requirements June 2011 higher emergency than general data, so it needs to set aside resources rationally to ensure the QoS for network communication. Alarm data is used to alarm the network communication failure. It has the longest sending period and the highest urgency, so it must be processed as fast as possible to ensure the safety of industrial production and the staff. When setting aside resources, it has to ensure the reliability of data in a large extent and make the minimum delay. 2.2.3. It can be divided into fragment data and non-fragment data according to whether the data is fragment packets or not. Fragment data belongs to a complete datagram. The error rate of fragment datagram directly results in packet loss rate. Datagram delay is equal to the maximum delay of all the fragment datagram, so it needs to arrange the time slot resources for every fragment combined with certainty and the size of delay. Non-fragment data is normal sending data, it can arrange data transmission resources rationally combined with the cycle of data transmission. 2.2.4. It can be divided into aggregated data and non-aggregated data according to whether the data is aggregated or not. Aggregated data carried large amount of information, therefore it has higher requirements of QoS than normal data. Non-aggregated data is normal data. 2.2.5. It can be divided into 0-5 categories of industrial data according to industrial application. The reliability and real-time requirements for applications are decreased for data from Class 0 to Class 5.The class of security data has the highest reliability and real-time requirements, while the class of logging on, uploading and download data have the lowest reliability and real-time requirements. Scheduling protocol needs to arrange the resources reasonably according to different characteristics of data in order to ensure the requirements of QoS in real time, reliability and certainty. When classifying the data, sometimes it needs to make reasonable adjustments in real-time, reliability and certainty between the priority and importance. Wang, et al. Expires Dec 11, 2011 [Page 6] Internet-Draft ietf-6lowpan-Scheduling-requirements June 2011 3. Determinism requirements Determinism means that data is sent and arrivalled within the stipulated time. Determinism is one of the three important features in the field of industrial applications, while another two characteristics of industrial applications are reliability and real- time. In the process automation and factory automation and other industrial areas, generally f(t) is the input and output control function, therefore only precise time synchronization and time deterministic input can generate the output which is correct and meets the requirements.When the input is not in deterministic time, it can lead to very serious consequences such as great economic loss, even seriously, lost lives. ISA100 working group draws up the ISA100.11a standards for process automation,in which deterministic scheduling technology is its key technology and all types are using the TDMA frame scheduling mechanism.The IEEE 802.15.4 working group recognizes that industrial applications has higher requirements on deterministic scheduling, so it establishes the IEEE 802.15.4e working group whose purpose is to improve the IEEE 802.15.4:2006 standard and draws up the relevant technical standards of the most critical features for three contorl areas,which are process automation, factory automation and business automation. Using the IPv6 technology for low-power wireless personal area network is the main purpose of the 6LoWPAN. RFC 4944 standard has solved the most basic techniques such as the delivery method for the IPv6 packeand and the IPv6 address configuration methods.But for the key technical requirements in industrial applications such as industrial deterministic scheduling, there are not relevant standards and methods. Therefore it needs to develop the industrial schedule demands for 6LoWPAN in order to support the determinism requirements of the wireless network. It specifically refers to determine the range of the error tolerance time and assign a fixed transmit/receive/broadcast time slot by rationally arranging the time slot length. 4. Reliability requirements Reliability is an important overall feature in industrial wireless sensor networks for industrial applications. Reliability in wireless Wang, et al. Expires Dec 11, 2011 [Page 7] Internet-Draft ietf-6lowpan-Scheduling-requirements June 2011 sensor networks for industry specific applications are wireless communication problem in harsh industrial environment and the minimum energy consumption. Such as network connectivity, data transmission delay, channel interference and packet loss will affect the reliability of industrial wireless communications. In the industrial wireless communication system, network managers allocate communication resources (time slots for communication link and communication channel access, etc.) through communication scheduling techniques. Communication scheduling technology can affect the reliability of the network greatly. Traditional IEEE80.2.15.4 network uses the MAC layer protocol based on CSMA which is a competitive channel access protocol. The MAC layer protocol requires that nodes must first listen to the channel before sending the MAc frame, if the channel is idle, then immediately senting the MAc frame, otherwise randomly selecting a delay to wait and re-scheduling group after waiting, but it can not guarantee the certainty of transmission time. The communication scheduling based on time slot allocation technology arranges each node to send and receive data in a predetermined super-frame time slot, which meet the conditions of timing and synchronization. The node can receive the data frame of each node at each time slot without mixing interference.At the same time, data frames sending to other nodes are arranged in scheduled time slot for transmission, each mobile terminal will be able to distinguish data frames sending to it and receive them as long as it receives data in the specified time slot, which avoid network communication conflicts considerably and increase the certainty and reliability of network communication. In addition, the jump-channel technology ensures the data to transmit in channel which has better quality and improve the reliability of the network. 5. Real-time requirements The definition of real-time in industrial wireless network means that data transmission in network is determinative.It is predictable, which means that data transmission in real-time network has time limit. Real-time is an important feature to which industrial wireless network need to meet. Many operations are required to predict the data delay of the network transmission in the field of industrial application, and the shortest path routing based scheduling algorithm is particularly needed, which not only considers traditional path indicators such as Wang, et al. Expires Dec 11, 2011 [Page 8] Internet-Draft ietf-6lowpan-Scheduling-requirements June 2011 the hop count/actual distance, but also the path delay. Especially for IPv6 wireless sensor network, when using the real-time internet applications such as multimedia audio, video, instant messaging and other applications, it needs to reduce the network transmission delay as much as possible in order to ensure the fluency of multimedia. At this time the deterministic scheduling mechanism should try to support the low latency requirements of real-time network as much as possible. Therefore, when designing scheduling mechanism in the industry, it must consider the delay requirements in actual industrial application network to support the real-time network in order to achieve a higher Qos of communication. Specific real-time requirements are as follows: 1. To ensure Qos by the type of the application stream. 2. To minimize the network delay in the condition that the low cost of network. 3. To support the routing mechanisms based on scheduling in wireless sensor network. 6. Low power requirements Industrial wireless network is composed by a considerable number of nodes with limited resources.This kind of node is a tiny embedded device and usually carries very limited battery power,at the same time it usually requires the node to achieve the life of 3-5 years in order to reduce the economic losses by renewing the equipment. Therefore, low power is an important technical feature in industrial wireless network. There are many methods to improve the entire network life cycle in wireless sensor network, such as making part of nodes in dormancy in the network, or increasing the density of nodes in the entire network to extend the network life cycle, or using the energy-aware routing node technology. For the energy problem of a single node, the methods include using dormant nodes, data compression, and the part of RFID in dormancy. Deterministic scheduling itself arranges time slot including sending and receiving time slot in data communications network by considering the data characteristics and Qos,so the communication time and idle time can be predicted in advance and it can well supported the dormant nodes. The nodes turn off radio frequency Wang, et al. Expires Dec 11, 2011 [Page 9] Internet-Draft ietf-6lowpan-Scheduling-requirements June 2011 transceiver in idle time to sleep.When the communication slot is coming, it opens node transceiver to enter the working condition. To support the dormancy mechanisms of nodes, the IEEE 802.15.4 standard and the IEEE 802.15.4e standard design the sleep stage in the super- frame structure for low-power support. Therefore when designing the deterministic scheduling mechanisms it needs to consider the low power requirements in order to save the energy of nodes and ensure the network life cycle. 7. Security Considerations 8. IANA Considerations 9. Acknowledgments Thanks to the authors of RFC 4944 and , as parts of this document are patterned after theirs. Thanks to Shanyang Ji for edit of this document. Also thanks to Hao Wang et al. This document was prepared using 2-Word-v2.0.template.dot. 10. References 10.1. Normative References [1] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [2] Crocker, D. and Overell, P.(Editors), "Augmented BNF for Syntax Specifications: ABNF", RFC 2234, Internet Mail Consortium and Demon Internet Ltd., November 1997. [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [RFC2234] Crocker, D. and Overell, P.(Editors), "Augmented BNF for Syntax Specifications: ABNF", RFC 2234, Internet Mail Consortium and Demon Internet Ltd., November 1997. Wang, et al. Expires Dec 11, 2011 [Page 10] Internet-Draft ietf-6lowpan-Scheduling-requirements June 2011 10.2. Informative References [3] Faber, T., Touch, J. and W. Yue, "The TIME-WAIT state in TCP and Its Effect on Busy Servers", Proc. Infocom 1999 pp. 1573- 1583. [Fab1999] Faber, T., Touch, J. and W. Yue, "The TIME-WAIT state in TCP and Its Effect on Busy Servers", Proc. Infocom 1999 pp. 1573- 1583. Wang, et al. Expires Dec 11, 2011 [Page 11] Internet-Draft ietf-6lowpan-Scheduling-requirements June 2011 Authors' Addresses Ping Wang Chongqing University of Posts and Telecommunications Administrative Building, Chongqing University of Posts and Telecommunications Chongqing, 400065 China Phone: (86) -23- 6246- 1061 Email: wangping@cqupt.edu.cn Heng Wang Chongqing University of Posts and Telecommunications Administrative Building, Chongqing University of Posts and Telecommunications Chongqing, 400065 China Email: wangheng@cqupt.edu.cn Genchang Ge Chongqing University of Posts and Telecommunications Administrative Building, Chongqing University of Posts and Telecommunications Chongqing, 400065 China Email: cqupt.ggc@gmail.com Wang, et al. Expires Dec 11, 2011 [Page 12]