| Internet-Draft | IGP Extensions for DetNet Deterministic | October 2023 |
| Xiong & Qian | Expires 25 April 2024 | [Page] |
This document proposes the deterministic links to provide a one-dimensional deterministic metric to guarantee the deterministic forwarding capabilities at different levels and proposes the deterministic links distribution by IGP extensions.¶
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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. The bounded latency indicates the minimum and maximum end-to-end latency from source to destination and bounded jitter (packet delay variation). [I-D.ietf-detnet-scaling-requirements]has described the enhanced requirements for DetNet enhanced data plane including the deterministic latency guarantees. [I-D.xiong-detnet-large-scale-enhancements] has proposed the packet treatment which should support new functions such as queuing mechanisms to ensure the deterministic latency. As per [I-D.ietf-detnet-controller-plane-framework], network nodes collects topology information and DetNet capabilities through IGP.¶
The computing method of end-to-end delay bounds is defined in [RFC9320]. It is the sum of the six delays in DetNet bounded latency model. It is the sum of non-queuing delay bound and queuing delay bound in DetNet bounded latency model. The upper bounds of queuing delay depends on the queuing mechanisms deployed along the path. For example, a link with a queuing mechanism that does not guarantee a bounded delay a non-determinisitc link and a link with a queuing mechanism that can provide deterministic delay is called a deterministic link. The delay of a a deterministic link is consist of the propagation delay of the packet on the link and the queuing delay of the packet at the node. A deterministic link can be a sub-network that provides deterministic transmission or a Point-to-Point (P2P) link.¶
This document proposes the deterministic links to provide a one-dimensional deterministic metric to guarantee the deterministic forwarding capabilities at different levels and proposes the deterministic links distribution by IGP extensions.¶
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in RFC 2119 [RFC2119].¶
This document proposes the deterministic links to provide a one-dimensional deterministic metric to guarantee the deterministic forwarding capabilities at different levels. The deterministic links can shield the differences from underlying forwarding and queuing mechanisms.¶
As per [RFC9320], six types of delays are defined in timing Model of DetNet. And the DetNet domain can also be modeling as deterministic links and nodes as shown in Figure 1. The deterministic node delay is constant while the deterministic link delay is variable within bounded latency. The end-to-end bounded latency depends on the sum of the deterministic link delay.¶
DetNet transit node A DetNet transit node B
+-------------------------+ +------------------------+
| Queuing | | Queuing |
| Regulator subsystem | | Regulator subsystem |
| +-+-+-+-+ +-+-+-+-+ | | +-+-+-+-+ +-+-+-+-+ |
-->+ | | | | | | | | | + +------------>+ | | | | | | | | | + +--->
| +-+-+-+-+ +-+-+-+-+ | | +-+-+-+-+ +-+-+-+-+ |
| | | |
+-------------------------+ +------------------------+
|-->|------->|------->|-->|------------>|-->|------->|------>|-->|-->|
2,3 4 5 6 1 2,3 4 5 6 1 2,3
|---- Deterministic Link Delay ---->|
Deterministic Links Deterministic Node
| A |---------------------------------->| B |----------------------->|
There are a number of deterministic links between deterministic nodes. And each deterministic link provides different level of deterministic forwarding capabilities indicated by Deterministic Class-Type (DT).¶
Deterministic Class-Type (DT): indicate the set of Traffic Trunks crossing a deterministic link that is governed by a specific set of bounded latency constraints. DT is used for the purposes of deterministic link resource planning, reservation and allocation, deterministic link resource constraint-based routing and admission control. A given Traffic Trunk belongs to the same DT on all links.¶
For example, three deterministic links with guaranteed jitter are supported between the Node A and Node B as following shown.¶
The traditional resource reservation method only considers the bandwidth availability of the BE (Best Effort) flow, which means that the reserved bandwidth meets the peak information rate (PIR) of the business flow at the macro level. As per [I-D.ietf-detnet-scaling-requirements], the enhanced DetNet need to support multiple queuing mechanisms to provide deterministic latency. For such scheduling mechanisms, even the bandwidth resources meet the transmission requirements at the macro level, there may not be enough resources in a specific timeslot, cycle or authorization time zone, so bounded delay and jitter cannot be guaranteed. So it is required to provide provisioning of fine-grained reservation for time-based resources.¶
Time-based Resources Container (TRC): the entity which is used for deterministic link to provide the time-based resources with deterministic capabilities by resolving resource conflicts between different levels. The container indicates the maximum transmitting bits per scheduling timeslot and it contains the corresponding scheduling resources reserved to guarantee the capability of deterministic link such as queuing, buffer and bandwidth.¶
This document defines new IS-IS TE sub-TLVs to distribute the deterministic links attributes at TE link and it can be announced in TLVs 22, 23, 141, 222, and 223" registry.¶
A new IS-IS Deterministic Link Sub-TLV is defined and the format is as shown in the following figure.¶
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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | DT | Link Scheduling Type | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ~ Sub-sub-TLV ~ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
where:¶
A new IS-IS Deterministic Link Maximum Reservble Bandwidth Sub-sub-TLV is defined and the format is as shown in the following figure.¶
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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Maximum Reserved Bandwidth | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
where:¶
A new IS-IS Deterministic Link Available Bandwidth Sub-sub-TLV is defined and the format is as shown in the following figure.¶
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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Available Bandwidth | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
where:¶
A new IS-IS Deterministic Link Delay Sub-sub-TLV is defined and the format is as shown in the following figure.¶
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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |A| Reserved | Maximum Deterministic Link Delay | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Reserved | Minimum Deterministic Link Delay | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Reserved | Maximum Deterministic Link Delay Variation | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
where:¶
TBA¶
TBA¶
IANA is requested to register the following sub-TLVs in the "Sub-TLVs for TLVs 22, 23, 141, 222,and 223" registry:¶
Type Description
------------------------------------
TBD1 Deterministic Link Sub-TLV
TBD2 Deterministic Link Maximum Reservble Bandwidth Sub-sub-TLV
TBD3 Deterministic Link Available Bandwidth Sub-sub-TLV
TBD4 Deterministic Link Delay Sub-sub-TLV
¶
TBA¶