--- 1/draft-ietf-roll-nsa-extension-02.txt 2019-06-28 09:13:08.756722674 -0700 +++ 2/draft-ietf-roll-nsa-extension-03.txt 2019-06-28 09:13:08.788723485 -0700 @@ -1,21 +1,21 @@ ROLL R. Koutsiamanis, Ed. Internet-Draft G. Papadopoulos Intended status: Standards Track N. Montavont -Expires: December 26, 2019 IMT Atlantique +Expires: December 30, 2019 IMT Atlantique P. Thubert Cisco - June 24, 2019 + June 28, 2019 RPL DAG Metric Container Node State and Attribute object type extension - draft-ietf-roll-nsa-extension-02 + draft-ietf-roll-nsa-extension-03 Abstract Implementing Packet Replication and Elimination from / to the RPL root requires the ability to forward copies of packets over different paths via different RPL parents. Selecting the appropriate parents to achieve ultra-low latency and jitter requires information about a node's parents. This document details what information needs to be transmitted and how it is encoded within a packet to enable this functionality. @@ -28,21 +28,21 @@ 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 December 26, 2019. + This Internet-Draft will expire on December 30, 2019. Copyright Notice Copyright (c) 2019 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 @@ -68,107 +68,113 @@ 6. Security Considerations . . . . . . . . . . . . . . . . . . . 9 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10 8. References . . . . . . . . . . . . . . . . . . . . . . . . . 10 8.1. Informative references . . . . . . . . . . . . . . . . . 10 8.2. Other Informative References . . . . . . . . . . . . . . 11 Appendix A. Implementation Status . . . . . . . . . . . . . . . 11 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 13 1. Introduction - Industrial network applications have stringent requirements on - reliability and predictability, and typically leverage 1+1 - redundancy, aka Packet Replication and Elimination (PRE) - [I-D.papadopoulos-6tisch-pre-reqs] to achieve their goal. In order - for wireless networks to be able to be used in such applications, the - principles of Deterministic Networking [I-D.ietf-detnet-architecture] - lead to designs that aim at maximizing packet delivery rate and - minimizing latency and jitter. Additionally, given that the network - nodes often do not have an unlimited power supply, energy consumption - needs to be minimized as well. + Network-enabled applications in the industrial context must provide + stringent guarantees in terms of reliability and predictability. To + achieve this they typically leverage 1+1 redundancy, also known as + Packet Replication and Elimination (PRE) + [I-D.papadopoulos-6tisch-pre-reqs]. Allowing these kinds of + applications to function over wireless networks requires the + application of the principles of Deterministic Networking + [I-D.ietf-detnet-architecture]. This results in designs which aim at + maximizing packet delivery rate and minimizing latency and jitter. + Additionally, given that the network nodes often do not have an + unlimited power supply, energy consumption needs to be minimized as + well. As an example, to meet this goal, IEEE Std. 802.15.4 [IEEE802154-2015] provides Time-Slotted Channel Hopping (TSCH), a - mode of operation which uses a fixed communication schedule to allow - deterministic medium access as well as channel hopping to work around - radio interference. However, since TSCH uses retransmissions in the - event of a failed transmission, end-to-end delay and jitter - performance can deteriorate. + mode of operation which uses a common communication schedule based on + timeslots to allow deterministic medium access as well as channel + hopping to work around radio interference. However, since TSCH uses + retransmissions in the event of a failed transmission, end-to-end + delay and jitter performance can deteriorate. Furthermore, the 6TiSCH working group, focusing on IPv6 over IEEE Std. 802.15.4-TSCH, has worked on the issues previously highlighted and produced the "6TiSCH Architecture" [I-D.ietf-6tisch-architecture] to address that case. Building on this architecture, "Exploiting Packet Replication and Elimination in Complex Tracks in 6TiSCH LLNs" [I-D.papadopoulos-6tisch-pre-reqs] leverages PRE to improve the - Packet Delivery Ratio (PDR), provide a hard bound to the end-to-end - latency, and limit jitter. + Packet Delivery Ratio (PDR), to provide a hard bound to the end-to- + end latency, and to limit jitter. PRE is a general method of maximizing packet delivery rate and potentially minimizing latency and jitter, not limited to 6TiSCH. - More specifically, PRE achieves a controlled redundancy by laying + More specifically, PRE achieves controlled redundancy by laying multiple forwarding paths through the network and using them in parallel for different copies of a same packet. PRE can follow the Destination-Oriented Directed Acyclic Graph (DODAG) formed by RPL from a node to the root. Building a multi-path DODAG can be achieved based on the RPL capability of having multiple parents for each node in a network, a subset of which is used to forward packets. In order for this subset to be defined, a RPL parent subset selection - mechanism, which falls within the remit of the RPL Objective Function - (OF), needs to have specific path information. The specification of - the transmission of this information is the focus of this document. + mechanism, which is among the responsibilities of the RPL Objective + Function (OF), needs to have specific path information. This + document focuses on the specification of the transmission of this + specific path information. More concretely, this specification focuses on the extensions to the DAG Metric Container [RFC6551] required for providing the PRE mechanism a part of the information it needs to operate. This information is the RPL [RFC6550] parent address set of a node and it - must be sent to potential children nodes of the node. The RPL DIO - Control Message is the canonical way of broadcasting this kind of - information and therefore its DAG Metric Container [RFC6551] field is - used to append a Node State and Attribute (NSA) object. The node's - parent address set is stored as an optional TLV within the NSA - object. This specification defines the type value and structure for - this TLV. + must be sent to potential children of the node. The RPL DIO Control + Message is the canonical way of broadcasting this kind of information + and therefore its DAG Metric Container [RFC6551] field is used to + append a Node State and Attribute (NSA) object. The node's parent + address set is stored as an optional TLV within the NSA object. This + specification defines the type value and structure for the parent + address set TLV. 2. Terminology 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]. The draft uses the following Terminology: - Packet Replication and Elimination (PRE): The sending of multiple - copies of a packet using multi-path forwarding over a multi-hop - network and the consolidation of multiple received packet copies - to control flooding. See "Exploiting Packet Replication and - Elimination in Complex Tracks in 6TiSCH LLNs" - [I-D.papadopoulos-6tisch-pre-reqs] for more. + Packet Replication and Elimination (PRE): A method which transmits + multiple copies of a packet using multi-path forwarding over a + multi-hop network and which consolidates multiple received packet + copies to control flooding. See "Exploiting Packet Replication + and Elimination in Complex Tracks in 6TiSCH LLNs" + [I-D.papadopoulos-6tisch-pre-reqs] for more details. - Alternative Parent (AP) Selection: The problem of how to select the - next hop target node for a packet copy to be forwarded to when - performing packet replication. + Alternative Parent (AP) Selection: The mechanism for choosing the + next hop node to forward a packet copy when replicating packets. 3. Alternative Parent Selection In the RPL protocol, each node maintains a list of potential parents. - For PRE, the PP node is defined to be the same as the RPL DODAG - Preferred Parent (PP) node. Furthermore, to construct an alternative - path toward the root, in addition to the PP node, each node in the - network registers an AP node as well from its Parent Set (PS). There - are multiple alternative methods of selecting the AP node, - functionality which is included in the operation of the RPL Objective - Function (OF). A scheme which allows the two paths to remain - correlated is detailed here. More specifically, in this scheme a - node will select an AP node close to its PP node to allow the - operation of overhearing between parents. If multiple potential APs - match this condition, the AP with the lowest rank will be registered. + For PRE, the Preferred Parent (PP) node is defined to be the same as + the RPL DODAG Preferred Parent node. Furthermore, to construct an + alternative path toward the root, in addition to the PP node, each + node in the network registers an AP node as well from its Parent Set + (PS). There are multiple alternative methods of selecting the AP + node. This functionality is included in the operation of the RPL + Objective Function (OF). A scheme which allows the two paths to + remain correlated is detailed here. More specifically, in this + scheme a node will select an AP node close to its PP node to allow + the operation of overhearing between parents. For more details about + overhearing and its use in this context see Section 4.3. + "Promiscuous Overhearing" in "Exploiting Packet Replication and + Elimination in Complex Tracks in 6TiSCH LLNs" + [I-D.papadopoulos-6tisch-pre-reqs]. If multiple potential APs match + this condition, the AP with the lowest rank will be registered. There are at least three methods of performing the AP selection based on common ancestors (CA), named Common Ancestor Strict, Common Ancestor Medium, and Common Ancestor Relaxed, depending on how restrictive the selection process is. A more restrictive method will limit flooding but might fail to select an appropriate AP, while a less restrictive one will more often find an appropriate AP but might increase flooding. 3.1. Common Ancestor Strict @@ -413,21 +419,21 @@ This proposal requests the allocation of a new value TBD1 for the "Parent Set" TLV in the Routing Metric/Constraint TLVs sub-registry from IANA. 8. References 8.1. Informative references [I-D.ietf-6tisch-architecture] Thubert, P., "An Architecture for IPv6 over the TSCH mode - of IEEE 802.15.4", draft-ietf-6tisch-architecture-22 (work + of IEEE 802.15.4", draft-ietf-6tisch-architecture-23 (work in progress), June 2019. [I-D.ietf-detnet-architecture] Finn, N., Thubert, P., Varga, B., and J. Farkas, "Deterministic Networking Architecture", draft-ietf- detnet-architecture-13 (work in progress), May 2019. [I-D.papadopoulos-6tisch-pre-reqs] Papadopoulos, G., Montavont, N., and P. Thubert, "Exploiting Packet Replication and Elimination in Complex @@ -555,22 +561,22 @@ | Strict | | | | | CA | 99.66 | 13.75 | 28.86 | | Medium | | | | +----------+---------------+------------------+---------------------+ Links: o Contiki OS DIO DAGMC NSA extension (draft-koutsiamanis-roll-nsa- extension branch) [1] - o Wireshark dissectors (for the optional TLV, i.e., PS) - currently - merged / in master [2] + o Wireshark dissectors (for the optional PS TLV) - currently merged + / in master [2] Authors' Addresses Remous-Aris Koutsiamanis (editor) IMT Atlantique Office B00 - 126A 2 Rue de la Chataigneraie Cesson-Sevigne - Rennes 35510 FRANCE