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```China

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xiong.quan@zte.com.cn

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ZTE Corporation
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```China

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zhu.xiangyang@zte.com.cn

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Routing
```LSR
This document proposes the deterministic link to provide an
one-dimensional metric to indicate the deterministic forwarding
capabilities at different levels and proposes the deterministic
links distribution by IGP extensions.

```
```
Introduction
According to ,
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).
has described the enhanced requirements for DetNet enhanced data plane
including the deterministic latency guarantees. As per
,
network nodes need to collect topology information and deterministic
capabilities through IGP.
The computing method of end-to-end delay bounds is defined in .
It is the sum of the six delays in bounded latency model. It is
the sum of non-queuing delay bound and queuing delay bound.
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 is a
non-deterministic link and a link with a time-based queuing
mechanism that can provide deterministic latency guarantee is
called a deterministic link. The delay of 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 link to provide an
one-dimensional metric to indicate the deterministic forwarding
capabilities at different levels and proposes the deterministic
links distribution by IGP extensions.
Requirements Language
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 .
Terminology
The terminology is defined as and
.
Deterministic Link
This document proposes the deterministic link to provide an one-dimensional
metric to indicate the deterministic forwarding capabilities at different
levels. The deterministic links can shield the differences from
underlying forwarding mechanisms.
Deterministic Link Model
As per , 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.
- Deterministic Link Delay = Regulation delay + Queuing subsystem delay +
Output delay + Link delay + Frame preemption delay
- Deterministic Node Delay = Processing delay

Classification of Deterministic Links
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 and QoS requirements of deterministic
guarantees such as tight jitter,strict latency, loose latency and
so on. 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.
The scheduling type of the deterministic link depends on the
classification of the queuing solutions. Many variations and
extensions of queuing mechanisms have been proposed to guarantee
the deterministic latency in DetNet such as ECQF [IEEE 802.1Qdv],
Multi-CQF ,
TCQF ,
CSQF ,
TQF ,
C-SCORE ,
EDF ,
gLBF and so on.
has described the classification criteria of the solutions.
has proposed the Time-based
Resources Container (TRC) to indicate the capabilities with time-based
resources. It can be used for deterministic link to reserve the
corresponding scheduling resources such as queuing, buffer and bandwidth
to guarantee the deterministic capability.
For example, three deterministic links with guaranteed jitter
are supported between the Node A and Node B as following shown.
- deterministic link 1, DT=1 (Jitter Guarantee, Link-scheduling-type=CSQF), bandwidth=20Mbit/s, jitter=10us.
- deterministic link 2, DT=2 (Jitter Guarantee, Link-scheduling-type=TCQF), bandwidth=30Mbit/s, jitter=20us.
- deterministic link 3, DT=3 (Jitter Guarantee, Link-scheduling-type=TQF), bandwidth=40Mbit/s, jitter=30us.

ISIS Extensions of Deterministic Link
This document defines new IS-IS TE sub-TLVs to distribute the
deterministic link attributes at TE link and it can be announced
in TLVs 22, 23, 141, 222, and 223" registry.
Deterministic Link Sub-TLV
A new IS-IS Deterministic Link Sub-TLV is defined and the format
is as shown in the following figure.
where:
- Type: Set to TBD1.
- Length: Contains the total length of the sub-TLV in octets.
The Length MUST be at least 8 and MUST be a multiple of 4.
- DT: the value of DT to indicates the set of Traffic Trunks
crossing the deterministic link that is governed by a specific
set of bounded latency constraints.
- Link Scheduling Type: indicates the type of the queuing or
scheduling mechanisms on this deterministic link.
- Sub-sub-TLV: indicates the optional sub-sub-TLV carried in
this sub-TLV.

Deterministic Link Maximum Reservable Bandwidth Sub-sub-TLV
A new IS-IS Deterministic Link Maximum Reservable Bandwidth Sub-sub-TLV
is defined and the format is as shown in the following figure.
where:
- Type: Set to TBD2.
- Length: Contains the total length of the sub-sub-TLV in octets.
The Length MUST be at least 8 and MUST be a multiple of 4.
- Maximum Reservable Bandwidth: indicates the maximum bandwidth
which can be reserved for this deterministic link.

Deterministic Link Available Bandwidth Sub-sub-TLV
A new IS-IS Deterministic Link Available Bandwidth Sub-sub-TLV
is defined and the format is as shown in the following figure.
where:
- Type: Set to TBD3.
- Length: Contains the total length of the sub-sub-TLV in octets.
The Length MUST be at least 8 and MUST be a multiple of 4.
- Available Bandwidth: indicates the available bandwidth of
this deterministic link.

Deterministic Link Delay Sub-sub-TLV
A new IS-IS Deterministic Link Delay Sub-sub-TLV is defined and the format
is as shown in the following figure.
where:
- Type: Set to TBD4.
- Length: Contains the total length of the sub-sub-TLV in octets.
The Length MUST be at least 8 and MUST be a multiple of 4.
- A: The A bit represents the Anomalous (A) bit. The A bit is set
when the measured value of this parameter exceeds its configured
maximum threshold.
- Maximum Deterministic Link Delay: indicates the maximum
deterministic link delay value (in microseconds) over a
configurable interval, encoded as an integer value.
- Minimum Deterministic Link Delay: indicates the minimum
deterministic link delay value (in microseconds) over a
configurable interval, encoded as an integer value.
- Maximum Deterministic Link Delay Variation: indicates the
maximum deterministic link delay variation value over a
configurable interval in microseconds, encoded as an
integer value.

OSPF Extensions of Deterministic Links
TBA
Security Considerations
Security considerations for DetNet are covered in the DetNet
Architecture and DetNet controller plane
and DetNet security considerations . The
security considerations specified in
are also applicable to the IGP procedures defined in this document.
IANA Considerations
IANA is requested to register the following sub-TLVs
in the "Sub-TLVs for TLVs 22, 23, 141, 222,and 223" registry:
Acknowledgements
The authors would like to acknowledge Aihua Liu, Bin Tan
for their thorough review and very helpful comments.
References
Normative References

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