| Internet-Draft | Segment Routing Header Extensions for De | July 2024 |
| Xiong, et al. | Expires 2 January 2025 | [Page] |
The DetNet data fields such as the Deterministic Latency Option can be used in enhanced Deterministic Networking (DetNet) to provide QoS treatment to achieve deterministic latency.¶
This document defines how DetNet data fields are encapsulated as part of the Segment Routing with IPv6 data plane (SRv6) header.¶
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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]. [I-D.ietf-detnet-scaling-requirements]has described the enhancement requirements for DetNet enhanced data plane in large-scale networks. The packet treatment should schedule the resources and indicate the behaviour to ensure the deterministic latency. Moreover, new functions and related metadata should be supported in DetNet enhanced data plane. [I-D.xiong-detnet-data-fields-edp] has proposed a common DetNet data fields and option types for enhanced DetNet data plane and defined a Deterministic Latency Option to carry queuing-based metadata.¶
This document defines how DetNet data fields are encapsulated as part of the Segment Routing with IPv6 data plane (SRv6) header [RFC8754].¶
The terminology is defined as [RFC8655] ,[RFC8938] and [RFC8754].¶
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.¶
Abbreviations and definitions used in this document:¶
The DetNet data fields such as deterministic latency option are defined in [I-D.xiong-detnet-data-fields-edp], and can be used for ensuring deterministic latency in enhanced DetNet data plane. The SRv6 encapsulation header (SRH) is defined in [RFC8754] and DetNet data fields can be encapsulated in the SRH.¶
The DetNet data fields can be divided into option header and data. And it can be carried in SRH extensions including the options such as SRH header field, segment List, TLV and the last segment. This enables the DetNet enhanced functions to build on the network programmability capability of SRv6.¶
The following sections discuss the optional SRH extensions for enhanced DetNet data plane in encapsulating the Deterministic Latency Option.¶
The DetNet data field can be carried in SRH segment list. This enables the ability of SRv6 networks to forward a DetNet flow per segment list. This document defines a new SRv6 Endpoint behavior which can be used to indicate the Deterministic Forwarding (DF) function, called End.DF. The End.DF is a variant of the End.X behavior defined in [RFC8986]. The End.DF SID SHOULD support the SRH processing of Penultimate Segment Pop (PSP), Ultimate Segment Pop (USP), and Ultimate Segment Decapsulation (USD) flavors as defined in [RFC8986]. The End.DF SIDs can be allocated by a centralized network controller and advertized by IGP or BGP-LS. The SRH segment list extensions for Deterministic Latency Option is as follows.¶
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Next Header | Hdr Ext Len | Routing Type | Segments Left |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Last Entry | Flags |D| TAG | DL Type |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| Segment List[0] (128-bit IPv6 address) |
| Deterministic Latency Option Data List[0] |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| |
...
| |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| Segment List[n] (128-bit IPv6 address) |
| Deterministic Latency Option Data List[n] |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
// //
// Optional Type Length Value objects (variable) //
// //
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
D (Deterministic Flag): when it is set, indicates the SRH extension for Deterministic Latency Option Data.¶
DL (Deterministic Latency) Type (8bits): as defined by the Deterministic Latency Option Header field, and is defined in Section 6.1 of [I-D.xiong-detnet-data-fields-edp].¶
Deterministic Latency Option Data List (variable): as defined by the Deterministic Latency Option data field, and is defined in Section 6.2 of [I-D.xiong-detnet-data-fields-edp].¶
The DetNet data field can be carried in SRH TLV. This enables the ability for an SRv6 node to determine whether to process or ignore some specific SRH TLVs is based on the SID function. The nodes which support the enhanced DetNet functionality can process the SRH TLV and the others can ignore the SRH DetNet TLV. The SRH TLV for DetNet Deterministic Latency Option is as follows.¶
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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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| SRH-TLV-Type |SRH-TLV-Length | DL Type | Data Len |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Deterministic Latency Data List[0](variable) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Deterministic Latency Data List[n](variable) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
SRH-TLV-Type/SRH-TLV-Length (8 bits): DetNet TLV Type for SRH is defined as TBA1. Length of the SRH TLV in 4-octet units. The fields related to the encapsulation of DetNet data fields in the SRH are defined as follows:¶
DL Type (8 bits): as defined by the Option Type field, and is defined in Section 6.1 of [I-D.xiong-detnet-data-fields-edp].¶
Data Len (8 bits): unsigned integer. This field specifies the length of option data added by each node.¶
Deterministic Latency Data List(variable): as defined by the Deterministic Latency Option data field, and is defined in Section 6.2 of [I-D.xiong-detnet-data-fields-edp]. The Option Data can be carried one time or in list.¶
As this document describes new options for IPv6, it can apply the security considerations of [RFC8754]. Security considerations for DetNet are covered in the DetNet Architecture [RFC8655] and DetNet data plane [RFC8938], [RFC8939], [RFC8964] and DetNet security considerations [RFC9055]. The security considerations specified in [I-D.ietf-detnet-scaling-requirements] are also applicable to the procedures defined in this document.¶
The authors would like to thank Rakesh Gandhi, Aihua Liu, Peng Liu, Bin Tan and Shaofu Peng for their review, suggestions and comments to this document.¶