]> ZTE Corporation

No.6 Huashi Park Rd Wuhan Hubei 430223 China xiong.quan@zte.com.cn

ZTE Corporation

Shenzhen China liu.aihua@zte.com.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 support new functions to ensure deterministic latency and the identification of deterministic latency related information. 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 Time Aware Shaping [IIEEE802.1Qbv] and priority-scheduling includes the Credit-Based Shaper[IEEE802.1Q-2014] with Asynchronous Traffic Shaping[IEEE802.1Qcr]. The cyclic-scheduling queuing mechanism has been proposed 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. So it is required to carry deterministic latency related information such as queuing parameters in data plane 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 carried 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 information Option The DetNet Deterministic Latency Information 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. Flag(16 bits): indicates the type of Deterministic Latency function. The flag is defined in section 3.1.1. TU(2 bits): indicates the time units for the Deterministic Delay. ODL(3 bits): Length of the Deterministic Delay field as an unsigned 3-bit integer. The length of Deterministic Delay variation field is same with Deterministic Delay field. OPL(3 bits): Length of the Deterministic Latency Parameters field as an unsigned 3-bit integer. Maximum Deterministic Delay (variable): indicates the Maximum queuing delay. The value is various when the Queuing type is different. Maximum Deterministic Delay variation (variable): indicates the Maximum Deterministic delay variation. The value is various when the flag is different. Deterministic Latency Parameters Sub-TLVs (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.

Flag The types of Deterministic Latency function 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. It indicates that a type of mechanisms is used for DetNet when one flag is set to 1 and multiple cooperating queuing mechanisms may be implemented when more than one flag is set to 1. For example, Credit-Based Shaper with Asynchronous Traffic Shaping can be used to provide the guaranteed delay. This document proposed the flags to cover the existing mechanisms and other mechanisms should be taken into considerations in the future. The Flags field is designed as follow:

Flag

T flag: 1 bit, if the flag is set to 1, it indicates the TAS (Time Aware Shaping) [IIEEE802.1Qbv] queuing mechanism. P Flag: 1 bit, if the flag is set to 1, it indicates the CBS (Credit-Based Shaper) [IEEE802.1Q-2014] queuing mechanism. C Flag: 1 bit, if the flag is set to 1, it indicates the CQF (Cyclic Queuing and Forwarding) [IEEE802.1Qch] queuing mechanism. A Flag: 1 bit, if the flag is set to 1, it indicates the ATS (Asynchronous Traffic Shaping) [IEEE802.1Qcr] queuing mechanism. M Flag: 1 bit, if the flag is set to 1, it indicates the Multiple Cyclic Queuing as defined in . D Flag: 1 bit, if the flag is set to 1, it indicates the Deadline-based Queuing mechanisms defined in and . N Flag: 1 bit, if the flag is set to 1, it indicates the ADN mechanism defined in .

Deterministic Latency Parameters The Deterministic Latency Parameters sub-TLVs is optional and it provides Deterministic Latency additional parameters for a node to forward a DetNet flow. The format of Sub-TLVs is based on the type and the flag field. When the M flag is set to 1, the Cycle Sub-TLV may be carried and designed as follow:

Cycle Sub-TLV

Sub-type (16bits): TBD2, indicates the type of Cycle Sub-TLV. Length (16bits): indicated the length of Cycle Sub-TLV. 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 D flag is set to 1, the Deadline Sub-TLV may be carried and designed as follow:

Deadline Sub-TLV

Sub-type (16bits): TBD3, indicates the type of Deadline Sub-TLV. Length (16bits): indicated the length of Deadline Sub-TLV. Deadline Information(variable): indicates the deadline information such as deadline as defined in or planned Deadline and deadline Deviation as defined in .

Encapsulation of DetNet Options

IPv6 Networks The DetNet Deterministic Latency information 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 information 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 Information 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 Information Option	[this document]

The Sub-TLVs has been proposed for Deterministic Latency Information Option as following shown:

Sub-type	Description	Reference
TBD2	Cycle Sub-TLV	[this document]
TBD3	Deadline Sub-TLV	[this document]

Normative References 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. This memo describes the network element behavior required to deliver a guaranteed service (guaranteed delay and bandwidth) in the Internet. [STANDARDS-TRACK] 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. 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. This document provides an overall framework for the Deterministic Networking (DetNet) data plane. 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. 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. 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. Huawei Huawei This document presents a queuing mechanism with multiple cyclic buffers. 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. 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. ZTE Corporation ZTE Corporation This document introduces new IPv6 options for Hop-by-Hop Options header, to carry deadline related information for deterministic flows. 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. This document specifies version 6 of the Internet Protocol (IPv6). It obsoletes RFC 2460.