]> DetNet Deterministic Latency Option for IPv6 ZTE Corporation
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CAICT
China zhaojunfeng@caict.ac.cn
Routing DETNET This document introduces new IPv6 options to identify the Deterministic Latency related information for DetNet flows in IPv6 and SRv6 networks.
Introduction According to , Deterministic Networking (DetNet) operates at the IP layer and delivers service which provides extremely low data loss rates and bounded latency within a network domain. DetNet data planes has been specified in . The existing deterministic technologies are facing large-scale number of nodes and long-distance transmission, traffic scheduling, dynamic flows, and other controversial issues in large-scale networks. The enhanced DetNet Data plane is required to support a data plane method of flow identification and packet treatment. has described the enhancement requirements for DetNet data plane, it is required to support information used by functions ensuring Deterministic Latency. has proposed the overall framework of DetNet enhancements for large-scale deterministic networks. The packet treatment should schedule the resources and indicate the behaviour to ensure the deterministic latency. Moverover, new functions and related metadata shouled be supported in enhanced DetNet. The queuing-based mechanisms is an important type of resource to ensure the deterministic latency. As described in , the end-to-end bounded latency depends on the value of queuing delay bound along with the queuing mechanisms. Multiple queuing mechanisms can be used to guarantee the bounded latency in DetNet. And many types of queuing mechanisms have been proposed to provide diversified deterministic service for various applications. For example, time-scheduling queuing mechanisms includes the TAS (Time Aware Shaping) [IIEEE802.1Qbv] and priority-scheduling includes the CBS (Credit-Based Shaper)[IEEE802.1Q-2014] with ATS (Asynchronous Traffic Shaping)[IEEE802.1Qcr]. The cyclic-scheduling queuing mechanism has been proposed such as CQF (Cyclic Queuing and Forwarding) in [IEEE802.1Qch] and improved in . The deadline-scheduling queuing mechanism has been proposed in and improved in . The per-flow queuing mechanism includes Guaranteed-Service Integrated service (IntServ) . The asynchronous queuing mechanism includes the Asynchronous Deterministic Networking (ADN) as per . The functions such as the queuing mechanisms should be provided for enhanced DetNet to ensure the deterministic latency. And when queuing mechanisms uesed in large-scale networks, some queuing parameters should be carried for coordination between nodes so as to make appropriate packet forwarding and scheduling decisions to meet the time bounds. The DetNet forwarding nodes along the path can apply the function and the deterministic latency related information should be carried as metadata in the packet to achieve the end-to-end bounded latency. This document introduces new IPv6 options to identify the Deterministic Latency related information for DetNet flows in IPv6 and SRv6 networks.
Conventions used in this document
Terminology The terminology is defined as .
Requirements Language The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in BCP 14 when, and only when, they appear in all capitals, as shown here.
The DetNet Options This document defines new IPv6 options for DetNet to signal Deterministic Latency related information to the DetNet layers. The format of the options follow the generic definition in section 4.2 of . The option may be placed either in an HbH or a DoH EH.
The Deterministic Latency Option The DetNet Deterministic Latency Option helps to discriminate the types of mechanisms and specify the related parameters.
Deterministic Latency Option Format
Option Type: 8-bit identifier of the type of option. Value TBD1 by IANA; the highest-order 3 bits of the field is 001 to skip over this option and continue processing the header if the processing IPv6 node does not recognize the Option Type and to permit the Option Data to be changed en route to the packet's final destination. Opt Data Len: 8-bit unsigned integer. Length of the Option Data field of this option, in octets. It is set to 12. DLA(Deterministic Latency Action) Type(16 bits): indicates the type of deterministic latency actions for IPv6/SRv6 metadata. The DLA Type is defined in section 3.1.1. TU(3 bits): indicates the time units for the Deterministic Delay. DLL(3 bits): Length of the Deterministic Latency Information field as an unsigned 3-bit integer. Deterministic Latency Information(variable): it is optional and provides additional information for a node to forward a DetNet flow. The Sub-TLVs has been defined in section 3.1.2.
DLA Type The DLA Type can be divided into two parts including behaviour action type and function/queuing type. The format is 16 bits such as 0xFFFF. The DLA Type field is designed as follow:
DLA Type
Type(8 bits): indicates the behaviour action type of packet treatment ensuring the deterministic latency as following shown.
Behaviour Action Type
Sub-type(8 bits): indicates the type of functions ensuring the deterministic latency and related metadata. For example, the functions such as a pirticular queuing mechanism may be indicated and related parameters should be provided as section 3.1.2 shown.
Function Action Sub-type
The types of Deterministic Latency functions should cover all the mechanisms ensuring the Deterministic Latency such as the existing queuing and scheduling mechanisms and other mechanisms which may be proposed in the future.
Deterministic Latency Information It provides deterministic latency information for a node to forward a DetNet flow. The format is based on the sub-type. When the Sub-type is set to 0x0001, indicates the Multiple Cyclic Queuing mechasims as defined in . The Cycle information may be carried and designed as following shown:
Cycle information
Cycle Profile ID (32bits): indicates the profile ID which the cyclic queue applied at a node. Cycle ID (32bits): indicates the Cycle ID for a node to forward a DetNet flow. When the Sub-type is set to 0x0002, the Deadline Information may be carried and designed as follow:
Deadline Information
Planned and deadline Deviation has been provided as defined in . When the Sub-type is set to 0x0003, the Local Deadline Information may be carried and designed as follow:
Local Deadline Information
Local Deadline: indicates the local deadline as defined in .
Encapsulation of DetNet Options
IPv6 Networks The DetNet Deterministic Latency Option is intended to be placed in an IPv6 HbH EH since it must be processed by every DetNet forwarding node along the path. All DetNet forwarding nodes can use the queuing information to achieve the packet forwarding and queue scheduling.
Deterministic Latency Information Option Format
SRv6 Networks The DetNet Deterministic Latency Option is intended to be placed in an DOH EH before an SRH since it must be processed by the DetNet forwarding nodes of the SRv6 segment list. The DetNet forwarding nodes among SRv6 segment list can use the Deterministic Latency to achieve the packet forwarding and queue scheduling.
Deterministic Latency Option Format
Security Considerations TBA
Acknowledgements The authors would like to thank Peng Liu, Bin Tan, Shaofu Peng for their review, suggestions and comments to this document.
IANA Considerations
New Option for IPv6 This specification updates the "Destination Options and Hop-by-Hop Options" under the "Internet Protocol Version 6 (IPv6) Parameters" registry with the values below:
Type Description Reference
TBD1 Deterministic Latency Option [this document]
Normative References Key words for use in RFCs to Indicate Requirement Levels In many standards track documents several words are used to signify the requirements in the specification. These words are often capitalized. This document defines these words as they should be interpreted in IETF documents. This document specifies an Internet Best Current Practices for the Internet Community, and requests discussion and suggestions for improvements. Specification of Guaranteed Quality of Service This memo describes the network element behavior required to deliver a guaranteed service (guaranteed delay and bandwidth) in the Internet. [STANDARDS-TRACK] Deterministic Networking Architecture This document provides the overall architecture for Deterministic Networking (DetNet), which provides a capability to carry specified unicast or multicast data flows for real-time applications with extremely low data loss rates and bounded latency within a network domain. Techniques used include 1) reserving data-plane resources for individual (or aggregated) DetNet flows in some or all of the intermediate nodes along the path of the flow, 2) providing explicit routes for DetNet flows that do not immediately change with the network topology, and 3) distributing data from DetNet flow packets over time and/or space to ensure delivery of each packet's data in spite of the loss of a path. DetNet operates at the IP layer and delivers service over lower-layer technologies such as MPLS and Time- Sensitive Networking (TSN) as defined by IEEE 802.1. Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words RFC 2119 specifies common key words that may be used in protocol specifications. This document aims to reduce the ambiguity by clarifying that only UPPERCASE usage of the key words have the defined special meanings. Deterministic Networking (DetNet) Data Plane Framework This document provides an overall framework for the Deterministic Networking (DetNet) data plane. Requirements for Large-Scale Deterministic Networks China Mobile Huawei Futurewei Technologies USA ZTE Corporation ETRI Aiming at the large-scale deterministic network, this document describes the technical and operational requirements when the different deterministic levels of applications co-exist and are transported over a wide area. This document also describes the corresponding Deterministic Networking (DetNet) data plane enhancement requirements. DetNet Enhancements for Large-Scale Deterministic Networks ZTE Corporation China Mobile This document describes enhancements to DetNet to achieve the differentiated DetNet QoS in large-scale deterministic networks including the overall requirements and solutions with deterministic resources, routes and services. DetNet Bounded Latency Huawei Technologies Co. Ltd EPFL EPFL Huawei Technologies Co. Ltd Ericsson This document presents a timing model for sources, destinations, and DetNet transit nodes. Using the model, it provides a methodology to compute end-to-end latency and backlog bounds for various queuing methods. The methodology can be used by the management and control planes and by resource reservation algorithms to provide bounded latency and zero congestion loss for the DetNet service. A Queuing Mechanism with Multiple Cyclic Buffers Huawei Huawei This document presents a queuing mechanism with multiple cyclic buffers. Segment Routed Time Sensitive Networking RAD Routers perform two distinct user-plane functionalities, namely forwarding (where the packet should be sent) and scheduling (when the packet should be sent). One forwarding paradigm is segment routing, in which forwarding instructions are encoded in the packet in a stack data structure, rather than programmed into the routers. Time Sensitive Networking and Deterministic Networking provide several mechanisms for scheduling under the assumption that routers are time synchronized. The most effective mechanisms for delay minimization involve per-flow resource allocation. SRTSN is a unified approach to forwarding and scheduling that uses a single stack data structure. Each stack entry consists of a forwarding portion (e.g., IP addresses or suffixes) and a scheduling portion (deadline by which the packet must exit the router). SRTSN thus fully implements network programming for time sensitive flows, by prescribing to each router both to-where and by-when each packet should be sent. Deadline Based Deterministic Forwarding ZTE Corporation ZTE Corporation China Mobile This document describes a deterministic forwarding mechanism based on deadline. The mechanism enhances strict priority scheduling algorithm with dynamically adjusting the priority of the queue according to its deadline attribute. Deadline Option ZTE Corporation ZTE Corporation This document introduces new IPv6 options for Hop-by-Hop Options header, to carry deadline related information for deterministic flows. Asynchronous Deterministic Networking Framework for Large-Scale Networks Sangmyung University ETRI ETRI Huawei China Mobile This document describes an overall framework of Asynchronous Deterministic Networking (ADN) for large-scale networks. It specifies the functional architecture and requirements for providing latency and jitter bounds to high priority traffic, without time- synchronization of network nodes. Internet Protocol, Version 6 (IPv6) Specification This document specifies version 6 of the Internet Protocol (IPv6). It obsoletes RFC 2460.