DetNet Queue Encapsulation with MPLS Data Plane
ZTE Corp.NanjingChinasong.xueyan2@zte.com.cnZTE Corp.WuhanChinaxiong.quan@zte.com.cn
Routing
DetNet Working GroupRequest for CommentsRFCInternet DraftI-D This document specifies format and principals for the MPLS header which contains the queuing delay information, designed for use
over a DetNet network with MPLS data plane. The guaranteed delay support enables forwarding and scheduling decisions for time-sensitive
service running on DetNet transit nodes that operate within a constrained network domain. This document also specifies a representation
for the delay field values in such networks. As specified in , 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. The DetNet data planes specification refers to . Based on the updates for DetNet Charter at March, 2022. It is required to support a data plane method of packet treatment including forwarding,
service protection, and queuing over Layer 3. As defined in , the DetNet MPLS data plane provides a foundation of building
blocks to enable PREOF (Packet Replication, Elimination and Ordering Functions (PREOF)) functions to DetNet service and forwarding sub-layer.
The DetNet service sub-layer includes a DetNet Control Word (d-CW) and an identifying service label (S-Label), an aggregation label (A-Label)
is a special case of S-Label used for aggregation. The DetNet forwarding sub-layer supports one or more forwarding labels (F-Labels) for providing
necessary resource allocation and explicit routes. To support time-sensitive service with ultra-low packet loss rates and bounded end-to-end delivery latency, necessary and feasible queuing
mechanisms applied to specific applicability on DetNet flows are required. As described in ,
the end-to-end bounded latency depends on the value of queuing delay bound along with the queuing mechanisms. The queuing methodology, mentioned
in and , describes queuing mechanisms that can be used in packets of
control and data plane to achieve DetNet service with bounded latency guarantee. The queuing mechanisms include, time-scheduling queuing mechanisms
that include the Time Aware Shaping IEEE802.1Qbv, priority-scheduling queuing mechanisms that include the Credit-Based Shaper IEEE802.1Q-2014
with Asynchronous Traffic Shaping IEEE802.1Qcr, the cyclic-scheduling queuing mechanism proposed in IEEE802.1Qch. This draft uses the queuing mechanisms described in as the proof for queuing selection,
leverages the existing DetNet MPLS encapsulations and mechanisms , and defines the extensible DetNet MPLS options for
queuing support over DetNet flows in the context of MPLS data plane so as to make appropriate packet forwarding and scheduling decisions to
achieve the end-to-end bounded latency from customers' SLA requirements. 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. Refer to , , and for the key terms used in this document. provides the architecture for deterministic networking (DetNet) enables the service delivery of DetNet flows with extremely
low packet loss rates and bounded end-to-end latency. The reference for computation and selection for methodology of queuing is described
at . The end-to-end latency bound for one DetNet flow is the sum of delay bound of non-queuing and
queuing processing. The delay bound for non-queuing processing may include output delay, link delay, frame preemption delay, and processing
delay, the delay bound for queuing processing may include regulator delay, queuing delay. It is assumed that the delay of non-queuing
processing is fixed or be ignorable, the delay of queuing processing is variable. To realize the guarantee of bounded latency service
it is important to select right queuing methodology applied to specific applications and carry necessary queuing delay information for
computation of end-to-end latency. The DetNet data plane encapsulation in transport network with MPLS data plane is specified in . This document provides
additional encapsulation for the queuing delay of DetNet flows in MPLS data plane. DetNet MPLS Queue, uses DetNet-MPLS based encapsulation with queuing option extension, listed as the below, The SPL (Special Purpose Label) may be B-SPL , new-SPL, extended SPL [RFC9017]. Refer to
, the SPL carries the action indicator for queue support showed as the Figure 2. Generally speaking the queuing mechanisms are processed hop by hop, end-to-end processing for queuing support is FFS.The Flags field is designed as follow:T flag: 1 bit, time-scheduling queuing indicator, e.g., Time Aware Shaping [IIEEE802.1Qbv]. If the flag is set 1, the time-scheduling
queuing mechanism is used for the DetNet flows, the can be correlated with the special label encapsulated in figure 2, or be mapped
with F-Label (s) or S-Label showed in figure 1.P Flag: 1 bit, priority-scheduling queuing indicator, e.g., Credit-Based Shaper [IEEE802.1q-2014]. C Flag: 1 bit, cyclic-scheduling queueing indicator, e.g., CQF [IEEE802.1Qch]. Note: For one specific DetNet flow, there is one or more choices for queuing mechanisms selection, the queuing mechanisms can be used
respectively or combined with each other.If the flag field is set 1 it will associate its sub-TLV to carry detailed or ancillary data for specific queuing delay information.
The encapsulation for sub-TLV is showed below: The encapsulation for queuing delay information will follow the requirements and framework of MPLS MNA discussed in MPLS WG. The encapsulation for Special Queuing Ancillary Data field is specific for queuing mechanisms. E.g., the sub-TLV for queuing
scheduling mechanism may carry deadline time data related, refer to .The sub-TLV for
cyclic-scheduling queuing mechanism may carry cycle time related, refer to This document describes a new IANA-managed registry to identify DetNet MPLS Queue Flags Bits. The registration procedure is "IETF Review"
. The registry name is "DetNet MPLS Queue Flags". There are 4 flags in the 8-bit Flags field, defined as in Table 1.BitDescriptionReference0-7unassignedthis document Security considerations for DetNet are covered in the DetNet Architecture RFC8655 and DetNet Security Considerations
. MPLS security considerations are covered in , , .
These security considerations also apply to this document. The authors would like to acknowledge Shaofu Peng for his thorough review and very helpful comments.