Internet Engineering Task Force (IETF) B. Varga
Request for Comments: 9016 J. Farkas
Category: Informational Ericsson
ISSN: 2070-1721 R. Cummings
National Instruments
Y. Jiang
Huawei
D. Fedyk
LabN Consulting
March 2021
Flow and Service Information Model for Deterministic Networking (DetNet)
Abstract
This document describes the flow and service information model for
Deterministic Networking (DetNet). These models are defined for IP
and MPLS DetNet data planes.
Status of This Memo
This document is not an Internet Standards Track specification; it is
published for informational purposes.
This document is a product of the Internet Engineering Task Force
(IETF). It represents the consensus of the IETF community. It has
received public review and has been approved for publication by the
Internet Engineering Steering Group (IESG). Not all documents
approved by the IESG are candidates for any level of Internet
Standard; see Section 2 of RFC 7841.
Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
https://www.rfc-editor.org/info/rfc9016.
Copyright Notice
Copyright (c) 2021 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(https://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction
1.1. Goals
1.2. Non-Goals
2. Terminology
2.1. Terms Used in This Document
2.2. Abbreviations
2.3. Naming Conventions
3. DetNet Domain and Its Modeling
3.1. DetNet Service Overview
3.2. Reference Points Used in Modeling
3.3. Information Elements
4. App-Flow-Related Parameters
4.1. App-Flow Characteristics
4.2. App-Flow Requirements
5. DetNet Flow-Related Parameters
5.1. Management ID of the DetNet Flow
5.2. Payload Type of the DetNet Flow
5.3. Format of the DetNet Flow
5.4. Identification and Specification of DetNet Flows
5.4.1. DetNet MPLS Flow Identification and Specification
5.4.2. DetNet IP Flow Identification and Specification
5.5. Traffic Specification of the DetNet Flow
5.6. Endpoints of the DetNet Flow
5.7. Rank of the DetNet Flow
5.8. Status of the DetNet Flow
5.9. Requirements of the DetNet Flow
5.9.1. Minimum Bandwidth of the DetNet Flow
5.9.2. Maximum Latency of the DetNet Flow
5.9.3. Maximum Latency Variation of the DetNet Flow
5.9.4. Maximum Loss of the DetNet Flow
5.9.5. Maximum Consecutive Loss of the DetNet Flow
5.9.6. Maximum Misordering Tolerance of the DetNet Flow
5.10. BiDir Requirement of the DetNet Flow
6. DetNet Service-Related Parameters
6.1. Management ID of the DetNet Service
6.2. Delivery Type of the DetNet Service
6.3. Delivery Profile of the DetNet Service
6.3.1. Minimum Bandwidth of the DetNet Service
6.3.2. Maximum Latency of the DetNet Service
6.3.3. Maximum Latency Variation of the DetNet Service
6.3.4. Maximum Loss of the DetNet Service
6.3.5. Maximum Consecutive Loss of the DetNet Service
6.3.6. Maximum Misordering Tolerance of the DetNet Service
6.4. Connectivity Type of the DetNet Service
6.5. BiDir Requirement of the DetNet Service
6.6. Rank of the DetNet Service
6.7. Status of the DetNet Service
7. Flow-Specific Operations
7.1. Join Operation
7.2. Leave Operation
7.3. Modify Operation
8. Summary
9. IANA Considerations
10. Security Considerations
11. References
11.1. Normative References
11.2. Informative References
Authors' Addresses
1. Introduction
Deterministic Networking (DetNet) provides a capability to carry
specified unicast or multicast data flows for real-time applications
with extremely low packet loss rates and assured maximum end-to-end
delivery latency. A description of the general background and
concepts of DetNet can be found in [RFC8655].
This document describes the DetNet flow and service information
model. For reference, [RFC3444] describes the rationale behind
information models in general. This document describes the flow and
service information models for operators and users to understand
DetNet services and for implementors as a guide to the functionality
required by DetNet services.
The DetNet architecture treats the DetNet-related data plane
functions decomposed into two sub-layers: a service sub-layer and a
forwarding sub-layer. The service sub-layer is used to provide
DetNet service protection and reordering. The forwarding sub-layer
provides resource allocation (to ensure low loss, assured latency,
and limited out-of-order delivery) and leverages traffic engineering
mechanisms.
DetNet service utilizes IP or MPLS, and DetNet is currently defined
for IP and MPLS networks, as shown in Figure 1, which is a reprint of
Figure 2 from [RFC8938]. IEEE 802.1 Time-Sensitive Networking (TSN)
utilizes Ethernet and is defined over Ethernet networks. A DetNet
flow includes one or more application-level flow (App-flow) as
payload. App-flows can be Ethernet, MPLS, or IP flows, which impacts
which header fields are utilized to identify a flow. DetNet flows
are identified by the DetNet encapsulation of App-flow(s) (e.g., MPLS
labels, IP 6-tuples, etc.). In some scenarios, App-flow and DetNet
flow look similar on the wire (e.g., Layer 3 (L3) App-flow over a
DetNet IP network).
+-----+
| TSN |
+-------+ +-+-----+-+
| DN IP | | DN MPLS |
+--+--+----+----+ +-+---+-----+-+
| TSN | DN MPLS | | TSN | DN IP |
+-----+---------+ +-----+-------+
Figure 1: DetNet Service Examples as per Data Plane Framework
As shown in Figure 1 and as described in [RFC8938], a DetNet flow can
be treated as an App-flow, e.g., at DetNet flow aggregation or in a
sub-network that interconnects DetNet nodes.
The DetNet flow and service information model provided by this
document contains both DetNet-flow- and App-flow-specific information
in an integrated fashion.
In a given network scenario, three information models can be
distinguished:
* Flow information models that describe characteristics of data
flows. These models describe, in detail, all relevant aspects of
a flow that are needed to support the flow properly by the network
between the source and the destination(s).
* Service information models that describe characteristics of
services being provided for data flows over a network. These
models can be treated as an information model that is network
operator independent.
* Configuration information models that describe, in detail, the
settings required on network nodes to provide proper service to a
data flow.
Service and flow information models are used between the user and the
network operator. Configuration information models are used between
the management/control plane entity of the network and the network
nodes. They are shown in Figure 2.
User Network Operator
flow/service
/\ info model +---+
/ \ <---------------> | X | management/control
---- +-+-+ plane entity
^
| configuration
| info model
+------------+
v | |
+-+ | v network
+-+ v +-+ nodes
+-+ +-+
+-+
Figure 2: Usage of Information Models (Flow, Service, and
Configuration)
The DetNet flow and service information model is based on [RFC8655]
and the concept of the data model specified by [IEEE8021Qcc]. In
addition to the TSN data model, [IEEE8021Qcc] also specifies
configuration of TSN features (e.g., traffic scheduling specified by
[IEEE8021Qbv]). The common architecture and flow information model
allow configured features to be consistent in certain deployment
scenarios, e.g., when the network that provides the DetNet service
includes both L3 and L2 network segments.
1.1. Goals
As expressed in the DetNet WG Charter [IETFDetNet], the DetNet WG
collaborates with IEEE 802.1 TSN in order to define a common
architecture for both Layers 2 and 3. This is beneficial for several
reasons, e.g., in order to simplify implementations and maintain
consistency across diverse networks. The flow and service
information models are also aligned for those reasons. Therefore,
the DetNet flow and service information models described in this
document are based on [IEEE8021Qcc], which is an amendment to
[IEEE8021Q].
This document specifies flow and service information models only.
1.2. Non-Goals
This document does not specify flow data models or DetNet
configuration. Therefore, the goals of this document differ from the
goals of [IEEE8021Qcc], which also specifies the TSN data model and
configuration of certain TSN features.
The DetNet-specific YANG data model is described in [DETNET-YANG].
2. Terminology
2.1. Terms Used in This Document
This document uses the terminology established in the DetNet
architecture [RFC8655] and the DetNet data plane framework [RFC8938].
The reader is assumed to be familiar with these documents and any
terminology defined therein. The DetNet <=> TSN dictionary of
[RFC8655] is used to perform translation from [IEEE8021Qcc] to this
document.
The following terminology is used in accordance with [RFC8655]:
App-flow The payload (data) carried over a DetNet service.
DetNet flow A sequence of packets that conform uniquely to a flow
identifier and to which the DetNet service is to be
provided. It includes any DetNet headers added to
support the DetNet service and forwarding sub-layers.
The following terminology is introduced in this document:
Source Reference point for an App-flow, where the flow starts.
Destination Reference point for an App-flow, where the flow
terminates.
DN Ingress Reference point for the start of a DetNet flow.
Networking technology-specific encapsulation may be
added here to the served App-flow(s).
DN Egress Reference point for the end of a DetNet flow.
Networking technology-specific encapsulation may be
removed here from the served App-flow(s).
2.2. Abbreviations
The following abbreviations are used in this document:
DetNet Deterministic Networking
DN DetNet
MPLS Multiprotocol Label Switching
PSN Packet Switched Network
TSN Time-Sensitive Networking
2.3. Naming Conventions
The following naming conventions were used for naming information
model components in this document. It is recommended that extensions
of the model use the same conventions.
* Descriptive names are used.
* Names start with uppercase letters.
* Composed names use capital letters for the first letter of each
component. All other letters are lowercase, even for
abbreviations. Exceptions are made for abbreviations containing a
mixture of lowercase and capital letters, such as IPv6. Example
composed names are SourceMacAddress and DestinationIPv6Address.
3. DetNet Domain and Its Modeling
3.1. DetNet Service Overview
The DetNet service can be defined as a service that provides a
capability to carry a unicast or a multicast data flow for an
application with constrained requirements on network performance,
e.g., low packet loss rate and/or latency.
Figures 5 and 8 in [RFC8655] show the DetNet service-related
reference points and main components.
3.2. Reference Points Used in Modeling
From a service-design perspective, a fundamental question is the
location of the service/flow endpoints, i.e., where the service/flow
starts and ends.
App-flow-specific reference points are the source (where it starts)
and the destination (where it terminates). Similarly, a DetNet flow
has reference points termed "DN Ingress" (where a DetNet flow starts)
and "DN Egress" (where a DetNet flow ends). These reference points
may coexist in the same node (e.g., in a DetNet IP end system). DN
Ingress and DN Egress reference points are intermediate reference
points for a served App-flow.
In this document, all reference points are assumed to be packet-based
reference points. A DN Ingress may add and a DN Egress may remove
networking technology-specific encapsulation to/from the served App-
flow(s) (e.g., MPLS label(s), UDP, and IP headers).
3.3. Information Elements
The DetNet flow information model and the service information model
rely on three groups of information elements:
App-flow-related parameters: These describe the App-flow
characteristics (e.g., identification, encapsulation, traffic
specification, endpoints, status, etc.) and the App-flow service
expectations (e.g., delay, loss, etc.).
DetNet flow-related parameters: These describe the DetNet flow
characteristics (e.g., identification, format, traffic
specification, endpoints, rank, etc.).
DetNet service-related parameters: These describe the expected
service characteristics (e.g., delivery type, connectivity delay/
loss, status, rank, etc.).
In the information model, a DetNet flow contains one or more
(aggregated) App-flows (N:1 mapping). During DetNet aggregation, the
aggregated DetNet flows are treated simply as App-flows and the
aggregate is the DetNet flow, which provides N:1 mapping. Similarly,
there is an aggregated many-to-one relationship for the DetNet
flow(s) to the DetNet service.
4. App-Flow-Related Parameters
When DetNet service is required by time-/loss-sensitive
application(s) running on an end system during communication with its
peer(s), the resulting data exchange has various requirements on
delay and/or loss parameters.
4.1. App-Flow Characteristics
App-flow characteristics are described by the following parameters:
FlowID: a unique (management) identifier of the App-flow, which
can be used to define the N:1 mapping of App-flows to a
DetNet flow
FlowType: set by the encapsulation format of the flow, which can
be Ethernet (TSN), MPLS, or IP
DataFlowSpecification: a flow descriptor, defining which packets
belongs to a flow, using specific packet header fields,
such as src-addr, dst-addr, label, VLAN-ID, etc.
TrafficSpecification: a flow descriptor, defining traffic
parameters, such as packet size, transmission time
interval, and maximum packets per time interval
FlowEndpoints: delineates the start and end reference points of the
App-flow by pointing to the source interface/node and
destination interface(s)/node(s)
FlowStatus: indicates the status of the App-flow with respect to
the establishment of the flow by the connected network,
e.g., ready, failed, etc.
FlowRank: indicates the rank of this flow relative to other flows
in the connected network
| Note: When defining the N:1 mapping of App-flows to a DetNet
| flow, the App-flows must have the same FlowType and different
| DataFlowSpecification parameters.
4.2. App-Flow Requirements
App-flow requirements are described by the following parameters:
FlowRequirements: defines the attributes of the App-flow regarding
bandwidth, latency, latency variation, loss, and
misordering tolerance
FlowBiDir: defines the data path requirement of the App-flow
whether it must share the same data path and physical
path for both directions through the network, e.g., to
provide congruent paths in the two directions
5. DetNet Flow-Related Parameters
The data model specified by [IEEE8021Qcc] describes data flows using
TSN service as periodic flows with fixed packet size (i.e., Constant
Bitrate (CBR) flows) or with variable packet size. The same concept
is applied for flows using DetNet service.
Latency and loss parameters are correlated because the effect of late
delivery can result in data loss for an application. However, not
all applications require hard limits on both latency and loss. For
example, some real-time applications allow graceful degradation if
loss happens (e.g., sample-based data processing and media
distribution). Some other applications may require high-bandwidth
connections that make use of packet replication techniques that are
economically challenging or even impossible. Some applications may
not tolerate loss but are not delay sensitive (e.g., bufferless
sensors). Time- or loss-sensitive applications may have somewhat
special requirements, especially for loss (e.g., no loss over two
consecutive communication cycles, very low outage time, etc.).
DetNet flows have the following attributes:
a. DnFlowID (Section 5.1)
b. DnPayloadType (Section 5.2)
c. DnFlowFormat (Section 5.3)
d. DnFlowSpecification (Section 5.4)
e. DnTrafficSpecification (Section 5.5)
f. DnFlowEndpoints (Section 5.6)
g. DnFlowRank (Section 5.7)
h. DnFlowStatus (Section 5.8)
DetNet flows have the following requirement attributes:
a. DnFlowRequirements (Section 5.9)
b. DnFlowBiDir (Section 5.10)
Flow attributes are described in the following sections.
5.1. Management ID of the DetNet Flow
A unique (management) identifier is needed for each DetNet flow
within the DetNet domain. It is specified by DnFlowID. It can be
used to define the N:1 mapping of DetNet flows to a DetNet service.
5.2. Payload Type of the DetNet Flow
The DnPayloadType attribute is set according to the encapsulated App-
flow format. The attribute can be Ethernet, MPLS, or IP.
5.3. Format of the DetNet Flow
The DnFlowFormat attribute is set according to the DetNet PSN
technology. The attribute can be MPLS or IP.
5.4. Identification and Specification of DetNet Flows
Identification options for DetNet flows at the Ingress/Egress and
within the DetNet domain are specified as follows; see Section 5.4.1
for DetNet MPLS flows and Section 5.4.2 for DetNet IP flows.
5.4.1. DetNet MPLS Flow Identification and Specification
The identification of DetNet MPLS flows within the DetNet domain is
based on the MPLS context in the service information model. The
attributes are specific to the MPLS forwarding paradigm within the
DetNet domain [RFC8964]. DetNet MPLS flows can be identified and
specified by the following attributes:
a. SLabel
b. FLabelStack
5.4.2. DetNet IP Flow Identification and Specification
DetNet IP flows can be identified and specified by the following
attributes [RFC8939]:
a. SourceIpAddress
b. DestinationIpAddress
c. IPv6FlowLabel
d. Dscp
e. Protocol
f. SourcePort
g. DestinationPort
h. IPSecSpi
The IP 6-tuple that is used for DetNet IP flow identification
consists of items a, b, d, e, f, and g. Items c and h are additional
attributes that can be used for DetNet flow identification in
addition to the 6-tuple. The 6-tuple and use of wild cards for these
attributes are specified in [RFC8939].
5.5. Traffic Specification of the DetNet Flow
The DnTrafficSpecification attributes specify how the DN Ingress
transmits packets for the DetNet flow. This is effectively the
promise/request of the DN Ingress to the network. The network uses
this traffic specification to allocate resources and adjust queue
parameters in network nodes.
TrafficSpecification has the following attributes:
a. Interval: the period of time in which the traffic specification
is specified
b. MaxPacketsPerInterval: the maximum number of packets that the
Ingress will transmit in one Interval
c. MaxPayloadSize: the maximum payload size that the Ingress will
transmit
d. MinPayloadSize: the minimum payload size that the Ingress will
transmit
e. MinPacketsPerInterval: the minimum number of packets that the
Ingress will transmit in one Interval
These attributes can be used to describe any type of traffic (e.g.,
CBR, Variable Bitrate (VBR), etc.) and can be used during resource
allocation to represent worst-case scenarios. Intervals are
specified as an integer number of nanoseconds. PayloadSizes are
specified in octets.
Flows exceeding the traffic specification (i.e., having more traffic
than defined by the maximum attributes) may receive a different
network behavior than the DetNet network has been engineered for.
Excess traffic due to malicious or malfunctioning devices can be
prevented or mitigated (e.g., through the use of existing mechanisms,
such as policing and shaping).
When MinPayloadSize and MinPacketsPerInterval parameters are used,
all packets less than the MinPayloadSize will be counted as being of
the size MinPayloadSize during packet processing when packet size
matters, e.g., when policing; all flows having less than
MinPacketsPerInterval will be counted as having MinPacketsPerInterval
when the number of packets per interval matters, e.g., during
resource reservation. However, flows having less than
MinPacketsPerInterval may result in a different network behavior than
the DetNet network has been engineered for. MinPayloadSize and
MinPacketsPerInterval parameters, for example, may be used when
engineering the latency bounds of a DetNet flow when Packet Ordering
Function (POF) is applied to the given DetNet flow.
Further optional attributes can be considered to achieve more
efficient resource allocation. Such optional attributes might be
worth for flows with soft requirements (i.e., the flow is only loss
sensitive or only delay sensitive but not both delay and loss
sensitive). Possible options about how to extend
DnTrafficSpecification attributes is for further discussion.
5.6. Endpoints of the DetNet Flow
The DnFlowEndpoints attribute defines the start and end reference
points of the DetNet flow by pointing to the ingress interface/node
and egress interface(s)/node(s). Depending on the network scenario,
it defines an interface or a node. Interface can be defined, for
example, if the App-flow is a TSN Stream, and it is received over a
well-defined User-to-Network Interface (UNI). For example, for App-
flows with MPLS encapsulation, defining an ingress node is more
common when a per-platform label space is used.
5.7. Rank of the DetNet Flow
The DnFlowRank attribute provides the rank of this flow relative to
other flows in the DetNet domain. Rank (range: 0-255) is used by the
DetNet domain to decide which flows can and cannot exist when network
resources reach their limit. Rank is used to help to determine which
flows can be bumped (i.e., removed from node configuration thereby
releasing its resources) if, for example, a port of a node becomes
oversubscribed (e.g., due to network reconfiguration). DnFlowRank
value 0 is the highest priority.
5.8. Status of the DetNet Flow
The DnFlowStatus attribute provides the status of the DetNet flow
with respect to the establishment of the flow by the DetNet domain.
DnFlowStatus includes the following attributes:
a. DnIngressStatus is an enumeration for the status of the flow's
Ingress reference point:
None: No Ingress.
Ready: Ingress is ready.
Failed: Ingress failed.
OutOfService: Administratively blocked.
b. DnEgressStatus is an enumeration for the status of the flow's
Egress reference points:
None: No Egress.
Ready: All Egresses are ready.
PartialFailed: One or more Egress is ready, and one or more
Egress failed. The DetNet flow can be used if the Ingress is
Ready.
Failed: All Egresses failed.
OutOfService: All Egresses are administratively blocked.
c. FailureCode is a nonzero code that specifies the error if the
DetNet flow encounters a failure (e.g., packet replication and
elimination is requested but not possible or DnIngressStatus is
Failed, DnEgressStatus is Failed, or DnEgressStatus is
PartialFailed).
Defining FailureCodes for DetNet is out of scope for this document.
Table 46-1 of [IEEE8021Qcc] describes TSN failure codes.
5.9. Requirements of the DetNet Flow
The DnFlowRequirements attribute specifies requirements to ensure the
service level desired for the DetNet flow.
DnFlowRequirements includes the following attributes:
a. MinBandwidth (Section 5.9.1)
b. MaxLatency (Section 5.9.2)
c. MaxLatencyVariation (Section 5.9.3)
d. MaxLoss (Section 5.9.4)
e. MaxConsecutiveLossTolerance (Section 5.9.5)
f. MaxMisordering (Section 5.9.6)
5.9.1. Minimum Bandwidth of the DetNet Flow
MinBandwidth is the minimum bandwidth that has to be guaranteed for
the DetNet flow. MinBandwidth is specified in octets per second.
5.9.2. Maximum Latency of the DetNet Flow
MaxLatency is the maximum latency from Ingress to Egress(es) for a
single packet of the DetNet flow. MaxLatency is specified as an
integer number of nanoseconds.
5.9.3. Maximum Latency Variation of the DetNet Flow
MaxLatencyVariation is the difference between the minimum and the
maximum end-to-end, one-way latency. MaxLatencyVariation is
specified as an integer number of nanoseconds.
5.9.4. Maximum Loss of the DetNet Flow
MaxLoss defines the maximum Packet Loss Rate (PLR) requirement for
the DetNet flow between the Ingress and Egress(es) and the loss
measurement interval.
5.9.5. Maximum Consecutive Loss of the DetNet Flow
Some applications have special loss requirements, such as
MaxConsecutiveLossTolerance. The maximum consecutive loss tolerance
parameter describes the maximum number of consecutive packets whose
loss can be tolerated. The maximum consecutive loss tolerance can be
measured, for example, based on sequence number.
5.9.6. Maximum Misordering Tolerance of the DetNet Flow
MaxMisordering describes the tolerable maximum number of packets that
can be received out of order. The value zero for the maximum allowed
misordering indicates that in-order delivery is required; misordering
cannot be tolerated.
The maximum allowed misordering can be measured, for example, based
on sequence numbers. When a packet arrives at the egress after a
packet with a higher sequence number, the difference between the
sequence number values cannot be bigger than "MaxMisordering + 1".
5.10. BiDir Requirement of the DetNet Flow
The DnFlowBiDir attribute defines the requirement that the flow and
the corresponding reverse direction flow must share the same path
(links and nodes) through the routed or switch network in the DetNet
domain, e.g., to provide congruent paths in the two directions that
share fate and path characteristics.
6. DetNet Service-Related Parameters
The DetNet service has the following attributes:
a. DnServiceID (Section 6.1)
b. DnServiceDeliveryType (Section 6.2)
c. DnServiceDeliveryProfile (Section 6.3)
d. DNServiceConnectivity (Section 6.4)
e. DnServiceBiDir (Section 6.5)
f. DnServiceRank (Section 6.6)
g. DnServiceStatus (Section 6.7)
Service attributes are described in the following sections.
6.1. Management ID of the DetNet Service
The DnServiceId attribute is a unique (management) identifier for
each DetNet service within the DetNet domain. It can be used to
define the many-to-one mapping of DetNet flows to a DetNet service.
6.2. Delivery Type of the DetNet Service
The DnServiceDeliveryType attribute is set according to the payload
of the served DetNet flow (i.e., the encapsulated App-flow format).
The attribute can be Ethernet, MPLS, or IP.
6.3. Delivery Profile of the DetNet Service
The DnServiceDeliveryProfile attribute specifies the delivery profile
to ensure proper serving of the DetNet flow.
DnServiceDeliveryProfile includes the following attributes:
a. MinBandwidth (Section 6.3.1)
b. MaxLatency (Section 6.3.2)
c. MaxLatencyVariation (Section 6.3.3)
d. MaxLoss (Section 6.3.4)
e. MaxConsecutiveLossTolerance (Section 6.3.5)
f. MaxMisordering (Section 6.3.6)
6.3.1. Minimum Bandwidth of the DetNet Service
MinBandwidth is the minimum bandwidth that has to be guaranteed for
the DetNet service. MinBandwidth is specified in octets per second
and excludes additional DetNet header (if any).
6.3.2. Maximum Latency of the DetNet Service
MaxLatency is the maximum latency from Ingress to Egress(es) for a
single packet of the DetNet flow. MaxLatency is specified as an
integer number of nanoseconds.
6.3.3. Maximum Latency Variation of the DetNet Service
MaxLatencyVariation is the difference between the minimum and the
maximum end-to-end, one-way latency. MaxLatencyVariation is
specified as an integer number of nanoseconds.
6.3.4. Maximum Loss of the DetNet Service
MaxLoss defines the maximum Packet Loss Rate (PLR) parameter for the
DetNet service between the Ingress and Egress(es) of the DetNet
domain.
6.3.5. Maximum Consecutive Loss of the DetNet Service
Some applications have a special loss requirement, such as
MaxConsecutiveLossTolerance. The maximum consecutive loss tolerance
parameter describes the maximum number of consecutive packets whose
loss can be tolerated. The maximum consecutive loss tolerance can be
measured, for example, based on sequence number.
6.3.6. Maximum Misordering Tolerance of the DetNet Service
MaxMisordering describes the tolerable maximum number of packets that
can be received out of order. The maximum allowed misordering can be
measured, for example, based on sequence number. The value zero for
the maximum allowed misordering indicates that in-order delivery is
required; misordering cannot be tolerated.
6.4. Connectivity Type of the DetNet Service
Two connectivity types are distinguished: point-to-point (p2p) and
point-to-multipoint (p2mp). Connectivity type p2mp may be created by
a forwarding function (e.g., p2mp LSP). (Note that from a service
perspective, mp2mp connectivity can be treated as a superposition of
p2mp connections.)
6.5. BiDir Requirement of the DetNet Service
The DnServiceBiDir attribute defines the requirement that the flow
and the corresponding reverse direction flow must share the same path
(links and nodes) through the routed or switch network in the DetNet
domain, e.g., to provide congruent paths in the two directions that
share fate and path characteristics.
6.6. Rank of the DetNet Service
The DnServiceRank attribute provides the rank of a service instance
relative to other services in the DetNet domain. DnServiceRank
(range: 0-255) is used by the network in case of network resource
limitation scenarios. DnServiceRank value 0 is the highest priority.
6.7. Status of the DetNet Service
The DnServiceStatus information group includes elements that specify
the status of the service-specific state of the DetNet domain. This
information group informs the user whether or not the service is
ready for use.
DnServiceStatus includes the following attributes:
a. DnServiceIngressStatus is an enumeration for the status of the
service's Ingress:
None: No Ingress.
Ready: Ingress is ready.
Failed: Ingress failed.
OutOfService: Administratively blocked.
b. DnServiceEgressStatus is an enumeration for the status of the
service's Egress:
None: No Egress.
Ready: All Egresses are ready.
PartialFailed: One or more Egress is ready, and one or more
Egress failed. The DetNet flow can be used if the Ingress is
Ready.
Failed: All Egresses failed.
OutOfService: Administratively blocked.
c. DnServiceFailureCode is a nonzero code that specifies the error
if the DetNet service encounters a failure (e.g., packet
replication and elimination is requested but not possible or
DnServiceIngressStatus is Failed, DnServiceEgressStatus is
Failed, or DnServiceEgressStatus is PartialFailed).
Defining DnServiceFailureCodes for DetNet service is out of scope for
this document. Table 46-1 of [IEEE8021Qcc] describes TSN failure
codes.
7. Flow-Specific Operations
The DetNet flow information model relies on three high-level
information groups:
DnIngress: The DnIngress information group includes elements that
specify the source for a single DetNet flow. This information
group is applied from the user of the DetNet service to the
network.
DnEgress: The DnEgress information group includes elements that
specify the destination for a single DetNet flow. This
information group is applied from the user of the DetNet service
to the network.
DnFlowStatus: The DnFlowStatus information group includes elements
that specify the status of the flow in the network. This
information group is applied from the network to the user of the
DetNet service. This information group informs the user whether
or not the DetNet flow is ready for use.
There are three possible operations for each DetNet flow with respect
to its DetNet service at a DN Ingress or a DN Egress (similar to App-
flows at a source or a destination):
Join: DN Ingress/DN Egress intends to join the flow.
Leave: DN Ingress/DN Egress intends to leave the flow.
Modify: DN Ingress/DN Egress intends to change the flow.
7.1. Join Operation
For the join operation, the DnFlowSpecification, DnFlowRank,
DnFlowEndpoint, and DnTrafficSpecification are included within the
DnIngress or DnEgress information groups. For the join operation,
the DnServiceRequirements groups can be included.
7.2. Leave Operation
For the leave operation, the DnFlowSpecification and DnFlowEndpoint
are included within the DnIngress or DnEgress information groups.
7.3. Modify Operation
For the modify operation, the DnFlowSpecification, DnFlowRank,
DnFlowEndpoint, and DnTrafficSpecification are included within the
DnIngress or DnEgress information group. For the join operation, the
DnServiceRequirements groups can be included.
The Modify operation can be considered to address cases when a flow
is slightly changed, e.g., only MaxPayloadSize (Section 5.5) has been
changed. The advantage of having a Modify is that it allows
initiation of a change of flow spec while leaving the current flow
operating until the change is accepted. If there is no linkage
between the Join and the Leave, then while figuring out whether the
new flow spec can be supported, the controller entity has to assume
that the resources committed to the current flow are in use. By
using Modify, the controller entity knows that the resources
supporting the current flow can be available for supporting the
altered flow. Modify is considered to be an optional operation due
to possible controller plane limitations.
8. Summary
This document describes the DetNet flow information model and the
service information model for DetNet IP networks and DetNet MPLS
networks. These models are used as input for creating the DetNet-
specific YANG module.
9. IANA Considerations
This document has no IANA actions.
10. Security Considerations
The external interfaces of the DetNet domain need to be subject to
appropriate confidentiality. Additionally, knowledge of which flows/
services are provided to a customer or delivered by a network
operator may supply information that can be used in a variety of
security attacks. Security considerations for DetNet are described
in detail in [DETNET-SECURITY]. General security considerations are
described in [RFC8655]. This document discusses modeling the
information, not how it is exchanged.
11. References
11.1. Normative References
[IEEE8021Qcc]
IEEE, "IEEE Standard for Local and Metropolitan Area
Networks--Bridges and Bridged Networks -- Amendment 31:
Stream Reservation Protocol (SRP) Enhancements and
Performance Improvements",
DOI 10.1109/IEEESTD.2018.8514112, IEEE 802.1Qcc-2018,
October 2013,
<https://ieeexplore.ieee.org/document/8514112/>.
[RFC8655] Finn, N., Thubert, P., Varga, B., and J. Farkas,
"Deterministic Networking Architecture", RFC 8655,
DOI 10.17487/RFC8655, October 2019,
<https://www.rfc-editor.org/info/rfc8655>.
[RFC8939] Varga, B., Ed., Farkas, J., Berger, L., Fedyk, D., and S.
Bryant, "Deterministic Networking (DetNet) Data Plane:
IP", RFC 8939, DOI 10.17487/RFC8939, November 2020,
<https://www.rfc-editor.org/info/rfc8939>.
[RFC8964] Varga, B., Ed., Farkas, J., Berger, L., Malis, A., Bryant,
S., and J. Korhonen, "Deterministic Networking (DetNet)
Data Plane: MPLS", RFC 8964, DOI 10.17487/RFC8964, January
2021, <https://www.rfc-editor.org/info/rfc8964>.
11.2. Informative References
[DETNET-SECURITY]
Grossman, E., Mizrahi, T., and A. J. Hacker,
"Deterministic Networking (DetNet) Security
Considerations", Work in Progress, Internet-Draft, draft-
ietf-detnet-security-16, 2 March 2021,
<https://tools.ietf.org/html/draft-ietf-detnet-security-
16>.
[DETNET-YANG]
Geng, X., Chen, M., Ryoo, Y., Fedyk, D., Rahman, R., and
Z. Li, "Deterministic Networking (DetNet) YANG Model",
Work in Progress, Internet-Draft, draft-ietf-detnet-yang-
11, 19 February 2021,
<https://tools.ietf.org/html/draft-ietf-detnet-yang-11>.
[IEEE8021Q]
IEEE, "IEEE Standard for Local and Metropolitan Area
Networks--Bridges and Bridged Networks",
DOI 10.1109/IEEESTD.2018.8403927, IEEE 802.1Q-2018, July
2018, <https://ieeexplore.ieee.org/document/8403927>.
[IEEE8021Qbv]
IEEE, "IEEE Standard for Local and metropolitan area
networks -- Bridges and Bridged Networks - Amendment 25:
Enhancements for Scheduled Traffic",
DOI 10.1109/IEEESTD.2016.8613095, IEEE 802.1Qbv-2015,
March 2016,
<https://ieeexplore.ieee.org/document/8613095>.
[IETFDetNet]
IETF, "Deterministic Networking (detnet)",
<https://datatracker.ietf.org/wg/detnet/charter/>.
[RFC3444] Pras, A. and J. Schoenwaelder, "On the Difference between
Information Models and Data Models", RFC 3444,
DOI 10.17487/RFC3444, January 2003,
<https://www.rfc-editor.org/info/rfc3444>.
[RFC8938] Varga, B., Ed., Farkas, J., Berger, L., Malis, A., and S.
Bryant, "Deterministic Networking (DetNet) Data Plane
Framework", RFC 8938, DOI 10.17487/RFC8938, November 2020,
<https://www.rfc-editor.org/info/rfc8938>.
Authors' Addresses
Balázs Varga
Ericsson
Budapest
Magyar Tudosok krt. 11.
1117
Hungary
Email: balazs.a.varga@ericsson.com
János Farkas
Ericsson
Budapest
Magyar Tudosok krt. 11.
1117
Hungary
Email: janos.farkas@ericsson.com
Rodney Cummings
National Instruments
Bldg. C
11500 N. Mopac Expwy
Austin, TX 78759-3504
United States of America
Email: rodney.cummings@ni.com
Yuanlong Jiang
Huawei
Bantian, Longgang district
Shenzhen
518129
China
Email: jiangyuanlong@huawei.com
Don Fedyk
LabN Consulting, L.L.C.
Email: dfedyk@labn.net
