| Internet-Draft | DetNet Deterministic Latency Option for | January 2023 |
| Xiong & Zhao | Expires 9 July 2023 | [Page] |
This document introduces new IPv6 options to identify the Deterministic Latency related information for DetNet flows in IPv6 and SRv6 networks.¶
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According to [RFC8655], 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 [RFC8938]. 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. [I-D.liu-detnet-large-scale-requirements] has described the enhancement requirements for DetNet data plane, it is required to support information used by functions ensuring Deterministic Latency. [I-D.xiong-detnet-large-scale-enhancements] 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 [I-D.ietf-detnet-bounded-latency], 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 [I-D.dang-queuing-with-multiple-cyclic-buffers]. The deadline-scheduling queuing mechanism has been proposed in [I-D.stein-srtsn] and improved in [I-D.peng-detnet-deadline-based-forwarding]. The per-flow queuing mechanism includes Guaranteed-Service Integrated service (IntServ) [RFC2212]. The asynchronous queuing mechanism includes the Asynchronous Deterministic Networking (ADN) as per [I-D.joung-detnet-asynch-detnet-framework]. 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.¶
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 [RFC2119] [RFC8174] when, and only when, they appear in all capitals, as shown here.¶
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 [RFC8200]. The option may be placed either in an HbH or a DoH EH.¶
The DetNet Deterministic Latency Option helps to discriminate the types of mechanisms and specify the related parameters.¶
0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Option Type | Opt Data Len | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | DLA Type | Reserved | TU | DLL | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Deterministic Latency Information(variable) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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.¶
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:¶
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Sub-type |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type(8 bits): indicates the behaviour action type of packet treatment ensuring the deterministic latency as following shown.¶
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Behaviour Action |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0x0000 | Unassigned |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0x0100 | Bandwidth guarantee |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0x0200 | Jitter guarantee |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0x0300 | Delay guarantee |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0x0400 | Low delay and jitter guarantee |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0x0500 |Ultra-low delay and jitter guarantee |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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.¶
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Sub-type| Function Action |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0x0000 | Unassigned |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0x0001 | Cycle Information |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0x0002 | Deadline Information |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0x0003 | Local Deadline Information |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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.¶
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 [I-D.dang-queuing-with-multiple-cyclic-buffers]. The Cycle information may be carried and designed as following shown:¶
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Cycle Profile ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Cycle ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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:¶
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Flags |M|D| Planned Deadline |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Accumulated Planned Deadline / Accumulated Deadline Deviation |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Accumulated Actual Residence Time / Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Planned and deadline Deviation has been provided as defined in [I-D.peng-6man-deadline-option].¶
When the Sub-type is set to 0x0003, the Local Deadline Information may be carried and designed as follow:¶
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Local Deadline |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Local Deadline: indicates the local deadline as defined in [I-D.stein-srtsn].¶
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.¶
+-----------------------------------+
| DetNet App-Flow |
| (original IP) Packet |
+-----------------------------------+
| other EHs |
+-----------------------------------+--\
| IPv6 Hop-by-Hop Ex Hdr | |
| (Deterministic Latency Option) | DetNet Options
| | |
+-----------------------------------+--/
| IPv6 Header |
+-----------------------------------+
| Data-Link |
+-----------------------------------+
| Physical |
+-----------------------------------+
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.¶
+-----------------------------------+
| DetNet App-Flow |
| (original IP) Packet |
+-----------------------------------+
| Segment Routing Header |
+-----------------------------------+ ---\
| IPv6 Destination Ex Hdr | |
| (Deterministic Latency Option) | DetNet Options
| | |
+-----------------------------------+ ---/
| IPv6 Header |
+-----------------------------------+
| Data-Link |
+-----------------------------------+
| Physical |
+-----------------------------------+
TBA¶
The authors would like to thank Peng Liu, Bin Tan, Shaofu Peng for their review, suggestions and comments to this document.¶
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] |