IGP Extensions for Time-based Resource

Abstract

This document proposes the time-based resources and the distribution by IGP extensions for traffic engineering in control plane to simplify resource management and scheduling in certain networks requiring the latency guarantees.¶

1. Introduction

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). DetNet uses resource allocation mechanism of Traffic Engineering (TE) technology to ensure a certain level of QoS, such as eliminating the contention loss and reducing jitter.¶

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 flow at the macro level. Bandwidth is generally used to meet the average rate, representing the maximum amount of bits within one second. But in large-scale network, there are problems such as large amount of dynamic concurrent traffic, complex topology, and long-distance propagation latency. Even the bandwidth resources meet the transmission requirements at the macro level, it may not guarantee the bounded latency due the bursts of massive traffic flows.¶

As per [I-D.ietf-detnet-scaling-requirements], the enhanced DetNet needs to support multiple time-based queuing mechanisms to provide deterministic latency. [I-D.ietf-detnet-dataplane-taxonomy] has discussed the classification criteria of many variations and extensions of queuing mechanisms such as ECQF [IEEE 802.1Qdv], Multi-CQF [I-D.dang-queuing-with-multiple-cyclic-buffers], TCQF [I-D.eckert-detnet-tcqf], CSQF [I-D.chen-detnet-sr-based-bounded-latency], TQF [I-D.peng-detnet-packet-timeslot-mechanism], C-SCORE [I-D.joung-detnet-stateless-fair-queuing], EDF[I-D.peng-detnet-deadline-based-forwarding], gLBF [I-D.eckert-detnet-glbf] and so on.¶

As per [I-D.ietf-detnet-dataplane-taxonomy], the enhancement solutions can be a combination of multiple data plane functional entities, such as regulators/shapers, queues, and schedulers. It requires enough bandwidth resources in a specific timeslot, cycle or authorization time zone to guarantee the bounded delay and jitter. So it is required to provide provisioning of fine-grained reservation for time-based resources which is a combination of bandwidth, buffer and time-based regulators/shapers, queues, and schedulers.¶

This document proposes the time-based resources and the distribution by IGP extensions for traffic engineering in control plane to simplify resource management and scheduling in certain networks requiring the latency guarantees.¶

2. Time-based Resource Container

The queuing and scheduling mechanism needs to combine corresponding buffer and bandwidth requirements to ensure the transmission delay and jitter of deterministic flows. This document lists the bandwidth requirements for different queuing mechanisms as following.¶

• For the ATS/CBS/C-SCORE mechanism, different traffic classes (such as class A, class B) can allocate initial burst and bandwidth, and then obtain the upper bound of each hop delay for each traffic class based on the "rate and delay" service curve.¶
• For the CQF/CSQF/TCQF mechanism, different cycle levels can allocate initial bandwidth resource, and the upper bound of each hop delay at each cycle level is related to the cycle length.¶
• For the EDF mechanism, different delay levels can allocate initial burst resources and bandwidth resource, satisfying schedulability conditions. Each delay level determines the upper bound of delay per hop.¶
• For the TQF mechanism, it has an initial burst resource for each slot number during the scheduling cycle, which does not exceed the length of the slot multiplied by the link bandwidth. The upper bound of each hop delay depends on the offset between the incoming slot and the reserved outgoing slot.¶

It is required to provide provisioning of fine-grained reservation for time-based resources which is a combination of bandwidth buffer and time-based regulators/shapers, queues, and schedulers. This can be approached with a tight control of the deterministic resources to maintain the amount of traffic within a budgeted volume of data per unit of time that fits the deterministic capabilities of the underlying network, and the use of time-based resources (bandwidth and buffers) per circuit, and by shaping and scheduling the packets at every hop.¶

This document defines the Time-based Resources Container (TRC) which is the virtual entity being used for link or node to provide the time-based resources with deterministic capabilities by resolving resource conflicts between different levels. The time-based resources container indicates the transmit data size per unit of time. The container indicates the transmitting bits per scheduling timeslot and contains the corresponding scheduling resources reserved to guarantee the capability of deterministic link and it may include queuing, buffer or bandwidth.¶

3. ISIS Extensions of Time-based Resources

   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              |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |           MaxReservableTimeResourcesBandwidth               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                       Time Unit Length                      |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                       Time Unit Number                      |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   ~                        Sub-sub-TLV                          ~
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   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              |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |     Time Unit ID            |          Reserved             |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                          AvailbleTimeUnitSize               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

4. OSPF Extensions of Time-based Resources

TBA¶

5. Security Considerations

Security considerations for DetNet are covered in the DetNet Architecture [RFC8655] and DetNet controller plane [I-D.ietf-detnet-controller-plane-framework] and DetNet security considerations [RFC9055]. The security considerations specified in [RFC5304] are also applicable to the IGP procedures defined in this document.¶

6. IANA Considerations

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    Time-based Resources Sub-TLV
    TBD2    Time Unit Sub-sub-TLV

7. Acknowledgements

The authors would like to acknowledge Aihua Liu, Bin Tan for the thorough review and very helpful comments.¶

8. References