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draft-ietf-detnet-dp-sol-ip-01.xml
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<?xml version="1.0" encoding="US-ASCII"?>
<!DOCTYPE rfc SYSTEM "rfc2629.dtd" [
]>
<?xml-stylesheet type='text/xsl' href='rfc2629.xslt' ?>
<?rfc toc="yes"?>
<?rfc symrefs="yes"?>
<?rfc sortrefs="yes"?>
<?rfc iprnotified="no"?>
<?rfc strict="yes"?>
<?rfc compact="yes"?>
<?rfc subcompact="no"?>
<rfc category="std"
docName="draft-ietf-detnet-dp-sol-ip-01"
ipr="trust200902"
submissionType="IETF">
<front>
<title abbrev="DetNet IP Data Plane">
DetNet IP Data Plane Encapsulation</title>
<author role="editor" fullname="Jouni Korhonen" initials="J." surname="Korhonen">
<!--organization abbrev="Nordic">Nordic Semiconductor</organization-->
<address>
<email>[email protected]</email>
</address>
</author>
<author role="editor" fullname="Balázs Varga" initials="B." surname="Varga">
<organization>Ericsson</organization>
<address>
<postal>
<street>Magyar Tudosok krt. 11.</street>
<city>Budapest</city>
<country>Hungary</country>
<code>1117</code>
</postal>
<email>[email protected]</email>
</address>
</author>
<!--author fullname="Donald Fauntleroy Duck" initials="D. F." surname="Duck">
<organization abbrev="Royal Bros.">Royal Bros.</organization>
<address>
<postal>
<street>13 Paradise Road</street>
<city>Duckburg</city>
<region>Calisota</region>
<country>USA</country>
</postal>
</address>
</author-->
<date />
<workgroup>DetNet</workgroup>
<abstract>
<t>
This document specifies Deterministic Networking data plane
operation for IP encapsulated user data.
</t>
</abstract>
</front>
<middle>
<section title="Introduction" anchor="sec_intro">
<t>
Deterministic Networking (DetNet) is a service that can be offered by a network to DetNet flows.
DetNet provides these flows extremely low packet loss rates and assured maximum end-to-end
delivery latency. General background and concepts of DetNet can
be found in the DetNet Architecture <xref target="I-D.ietf-detnet-architecture"/>.
</t>
<t>
This document specifies the DetNet data plane operation for IP
hosts and routers that provide DetNet service to IP encapsulated
data. No DetNet specific encapsulation is defined to support IP
flows, rather existing IP and higher layer protocol header information is used to support
flow identification and DetNet service delivery.
</t>
<t>
The DetNet Architecture decomposes the DetNet related data plane
functions into two layers: a service layer and a transport
layer. The service layer is used to provide DetNet service
protection and reordering. The transport layer is used to
provides congestion protection (low loss, assured latency, and
limited reordering). As no DetNet specific headers are added to
support IP DetNet flows, only the transport layer functions are
supported using the IP DetNet defined by this document. Service
protection can be provided on a per sub-net
basis using technologies such as MPLS <xref
target="I-D.ietf-detnet-dp-sol-mpls"/> and IEEE802.1 TSN.
</t>
<t>
This document provides an overview of the DetNet IP data plane
in <xref target="sec_dt_dp"/>, considerations that apply to
providing DetNet services via the DetNet IP data plane in <xref
target="dn-gen-encap-solution"/> and <xref
target="m-cp-considerations"/>. <xref target="ip-procs"/>
provides the procedures for hosts and routers that support
IP-based DetNet services. Finally, <xref target="mapping-tsn"/>
provides rules for mapping IP-based DetNet flows to IEEE 802.1
TSN streams.
</t>
</section>
<section title="Terminology">
<section title="Terms used in this document">
<t>
This document uses the terminology and concepts established in
the DetNet architecture <xref
target="I-D.ietf-detnet-architecture"/> the reader is assumed
to be familiar with that document.
</t>
</section>
<section title="Abbreviations">
<t>
The following abbreviations used in this document:
<!-- [JiK] Update later -->
<list style="hanging" hangIndent="14">
<t hangText="CE">Customer Edge equipment.</t>
<t hangText="CoS">Class of Service.</t>
<t hangText="DetNet">Deterministic Networking.</t>
<t hangText="DF">DetNet Flow.</t>
<t hangText="L2">Layer-2.</t>
<t hangText="L3">Layer-3.</t>
<t hangText="LSP">Label-switched path.</t>
<t hangText="MPLS">Multiprotocol Label Switching.</t>
<t hangText="OAM">Operations, Administration, and Maintenance.</t>
<t hangText="PE">Provider Edge.</t>
<t hangText="PREOF">Packet Replication, Ordering and Elimination Function.</t>
<t hangText="PSN">Packet Switched Network.</t>
<t hangText="PW">Pseudowire.</t>
<t hangText="QoS">Quality of Service.</t>
<t hangText="TE">Traffic Engineering.</t>
<t hangText="TSN">Time-Sensitive Networking, TSN is a Task Group of the IEEE
802.1 Working Group.</t>
</list>
</t>
</section>
<section title="Requirements language">
<t>
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 <xref target="RFC2119"/> <xref
target="RFC8174"/> when, and only when, they appear in all
capitals, as shown here.
</t>
</section>
</section>
<section title="DetNet IP Data Plane Overview" anchor="sec_dt_dp">
<!-- LB: this section should provide the overview related to:
<section title="Simplified IP related DetNet data plane solution" anchor="simple-ip-solution">
<t>
This section is the placeholder for the conclusion discussed during IETF 101 and 102.
</t>
<t>
[Editor's note: describe the 6 tuple way of identifying DetNet service flows. Also stress
that PREOF is per network segment as described in <xref target="nwsegments"/>
<list style="symbols">
<t>DetNet flows are recognized based on 6 tuple.</t>
<t>No end to end DN Sequence Number present in the packet.</t>
<t>Links / sub nets may use their technology specific methods to achieve DN service.</t>
<t>TE information does not travel with the packet (e.g., nailed down path ensured via Policy-Based-Routing).</t>
<t>etc.</t>
</list>
]
</t>
<t>
<xref target="simplifiedip"/> illustrated the case for DetNet simplified IP data plane solution.
</t>
</section>
-->
<t>
This document describes how IP is used by DetNet nodes, i.e.,
hosts and routers, to identify DetNet flows and provide a DetNet
service. From a data plane perspective, an end-to-end IP model
is followed. As mentioned above, existing IP and higher layer
protocol header information is used to support flow
identification and DetNet service delivery.
</t>
<t>
DetNet uses "6-tuple" based flow identification, where "6-tuple"
refers to information carried in IP and higher layer protocol
headers. General background on the use of IP headers, and
"5-tuples", to identify flows and support Quality of Service
(QoS) can be found in <xref target="RFC3670"/>. <xref
target="RFC7657"/> also provides useful background on the
delivery differentiated services (DiffServ) and "6-tuple" based
flow identification.
</t>
<t>
DetNet flow aggregation may be enabled via the use of
wildcards, masks, prefixes and ranges. IP tunnels may also be
used to support flow aggregation. In these cases, it is
expected that DetNet aware intermediate nodes will provide
DetNet service assurance on the aggregate through resource
allocation and congestion control mechanisms.
</t>
<figure align="center" anchor="fig_ip_detnet_simple"
title="A Simple DetNet (DN) Enabled IP Network">
<artwork><![CDATA[
IP DetNet Relay Relay IP DetNet
End System Node Node End System
+---------+ +---------+
| Appl. |<--------------- End to End Service ---------->| Appl. |
+---------+ ........... ........... +---------+
| Service |<---: Service :-- DetNet flow ---: Service :-->| Service |
+---------+ +---------+ +---------+ +---------+
|Transport| |Transport| |Transport| |Transport|
+-------.-+ +-.-----.-+ +-.-----.-+ +---.-----+
: Link : \ ,-----. / / ,-----. \
+........+ +-----[ Sub ]----+ +-[ Sub ]-+
[Network] [Network]
`-----' `-----'
|<--------------------- DetNet IP -------------------->|
]]></artwork>
</figure>
<t>
<xref target="fig_ip_detnet_simple"/> illustrates a DetNet enabled IP
network. The DetNet enabled end systems originate IP encapsulated
traffic that is identified as DetNet flows, relay nodes understand the
transport requirements of the DetNet flow and ensure that node,
interface and sub-network resources are allocated to ensure DetNet
service requirements. The dotted line around the Service component of
the Relay Nodes indicates that the transit routers are DetNet service
aware but do not perform any DetNet service layer function, e.g., PREOF.
IEEE 802.1 TSN is an example sub-network type which can provide support
for DetNet flows and service. The mapping of IP DetNet flows to TSN
streams and TSN protection mechanisms is covered in <xref
target="mapping-tsn"/>.
</t>
<t>
Note: The sub-network can represent a TSN, MPLS or IP network
segment.
</t>
<figure align="center" anchor="fig_ip_detnet"
title="DetNet (DN) IP Over MPLS Network">
<artwork><![CDATA[
IP DetNet Relay Transit Relay IP DetNet
End System Node Node Node End System
+---------+ +---------+
| Appl. |<--------------- End to End Service ---------->| Appl. |
+---------+ .....-----+ +-----..... +---------+
| Service |<---: Service |-- DetNet flow ---| Service :-->| Service |
| | : |<- DN MPLS flow ->| : | |
+---------+ +---------+ +---------+ +---------+ +---------+
|Transport| |Trp| |Trp| |Transport| |Trp| |Trp| |Transport|
+-------.-+ +-.-+ +-.-+ +---.---.-+ +-.-+ +-.-+ +---.-----+
: Link : / ,-----. \ : Link : / ,-----. \
+........+ +-[ Sub ]-+ +........+ +--[ Sub ]--+
[Network] [Network]
`-----' `-----'
|<---- DetNet MPLS ---->|
|<--------------------- DetNet IP -------------------->|
]]></artwork>
</figure>
<t>
<xref target="fig_ip_detnet"/> illustrates a variant of <xref
target="fig_ip_detnet_simple"/>, with an MPLS based DetNet
network as a sub-network between the relay nodes. It shows a
more complex DetNet enabled IP network where an IP flow is
mapped to one or more PWs and MPLS (TE) LSPs. The end systems
still originate IP encapsulated traffic that is identified as
DetNet flows. The relay nodes follow procedures defined in
<xref target="I-D.ietf-detnet-dp-sol-mpls"/> to map each DetNet
flow to MPLS LSPs. While not shown, relay nodes can provide
service layer functions such as PREOF over the MPLS transport
layer, and this is indicated by the solid line for the MPLS
facing portion of the Service component. Note that the Transit
node is MPLS (TE) LSP aware and performs switching based on MPLS
labels, and need not have any specific knowledge of the DetNet
service or the corresponding DetNet flow identification. See
<xref target="I-D.ietf-detnet-dp-sol-mpls"/> for details on the
mapping of IP flows to MPLS as well as general support for
DetNet services using MPLS.
</t>
<figure align="center" anchor="fig_non_detnet_ip"
title="Non-DetNet aware IP end systems with IP DetNet Domain">
<artwork><![CDATA[
IP Edge Edge IP
End System Node Node End System
+---------+ +.........+ +.........+ +---------+
| Appl. |<---:Svc Proxy:-- E2E Service ---:Svc Proxy:-->| Appl. |
+---------+ +.........+ +.........+ +---------+
| IP |<---:IP : :Svc:----- IP flow ----:Svc: :IP :-->| IP |
+---------+ +---+ +---+ +---+ +---+ +---------+
|Transport| |Trp| |Trp| |Trp| |Trp| |Transport|
+-------.-+ +-.-+ +-.-+ +-.-+ +-.-+ +---.-----+
: Link : \ ,-----. / / ,-----. \
+........+ +-----[ Sub ]----+ +--[ Sub ]--+
[Network] [Network]
`-----' `-----'
|<--- IP --->| |<------ DetNet IP ------->| |<--- IP --->|
]]></artwork>
</figure>
<t>
<xref target="fig_non_detnet_ip"/> illustrates another variant of <xref
target="fig_ip_detnet_simple"/> where the end systems are not DetNet
aware. In this case, edge nodes sit at the boundary of the DetNet
domain and provide DetNet service proxies for the end applications by
initiating and terminating DetNet service for the application's IP
flows. The existing header information or an approach such as described
in <xref target="aggregation"/> can be used to support DetNet flow
identification.
</t>
<t>
Non-DetNet and DetNet IP packets are identical on the wire. From
data plane perspective, the only difference is that there is
flow-associated DetNet information on each DetNet node that
defines the flow related characteristics and required forwarding
behavior. As shown above, edge nodes provide a Service Proxy
function that "associates" one or more IP flows with the
appropriate DetNet flow-specific information and ensures that
the receives the proper traffic treatment within the domain.
</t>
<t>
Note: The operation of IEEE802.1 TSN end systems over DetNet
enabled IP networks is not described in this document. While
TSN flows could be encapsulated in IP packets by an IP End
System or DetNet Edge Node in order to produce DetNet IP flows,
the details of such are out of scope of this document.
</t>
</section>
<!-- ================================================================= -->
<!-- =================== General Encap considerations ================ -->
<!-- ================================================================= -->
<section title="DetNet IP Data Plane Considerations" anchor="dn-gen-encap-solution">
<t>
This section provides informative considerations related to
providing DetNet service to flows which are identified
based on their header information. At a high level, the
following are provided on a per flow basis:
<list style="hanging">
<t hangText="Congestion protection and latency control:">
<vspace blankLines="1"/>
Usage of allocated resources (queuing, policing, shaping) to ensure
that the congestion-related loss and latency/jitter requirements of
a DetNet flow are met.
</t>
<t hangText="Explicit routes:">
<vspace blankLines="1"/>
Use of a specific path for a flow. This limits
miss-ordering and can improve delivery of deterministic latency.
</t>
<t hangText="Service protection:">
<vspace blankLines="1"/>
Which in the case of this document
translates to changing the explicit path after a failure is
detected in order to restore delivery of the required DetNet service
characteristics. Path changes, even in the case of failure
recovery, can lead to the out of order delivery of data.
</t>
<t>
Note: DetNet PREOF is not provided by the mechanisms defined in
this document.
</t>
<t hangText="Load sharing:">
<vspace blankLines="1"/>
Generally, distributing packets of the same DetNet flow over
multiple paths is not recommended. Such load sharing,
e.g., via ECMP or UCMP, impacts ordering and end-to-end jitter.
</t>
<t hangText="Troubleshooting:"> <vspace blankLines="1"/>
For example, to support identification of misbehaving flows.
</t>
<t hangText="Recognize flow(s) for analytics:"><vspace blankLines="1"/>
For example, increase counters.
</t>
<t hangText="Correlate events with flows:"><vspace blankLines="1"/>
For example, unexpected loss.
</t>
</list>
</t>
<section title="End-system specific considerations">
<t>
Data-flows requiring DetNet service are generated and terminated on
end systems. This document deals only with IP end systems. The
protocols used by an IP end system are specific to an application
and end systems peer with end systems using the same application
encapsulation format. This said, DetNet's use of 6-tuple IP flow
identification means that DetNet must be aware of not only the
format of the IP header, but also of the next protocol carried
within an IP packet.
</t>
<t>
When IP end systems are DetNet aware, no application-level or
service-level proxy functions are needed inside the DetNet domain.
For DetNet unaware IP end systems service-level proxy functions are
needed inside the DetNet domain.
</t>
<t>
End systems need to ensure that DetNet service requirements are met
when processing packets associated with a DetNet flow. When
transporting packets, this means that packets are
appropriately shaped on transmission and received appropriate traffic
treatment on the connected sub-network, see <xref target="QoS"/> and
<xref target="detrouting"/> for more details. When receiving packets,
this means that there are appropriate local node resources,
e.g., buffers, to receive and process a DetNet flow packets.
</t>
</section>
<section title="DetNet domain specific considerations">
<t>
As a general rule, DetNet IP domains need to be able to forward any
DetNet flow identified by the IP 6-tuple. Doing otherwise would limit
end system encapsulation format. From a practical standpoint this
means that all nodes along the end-to-end path of a DetNet flows need
to agree on what fields are used for flow identification, and the
transport protocols (e.g., TCP/UDP/IPsec) which can be used to
identify 6-tuple protocol ports.
</t>
<t>
From a connection type perspective two scenarios are identified:
<list style="numbers">
<t>
DN attached: end system is directly connected to an edge node or
end system is behind a sub-network. (See ES1 and ES2 in figure
below)
</t>
<t>
DN integrated: end system is part of the DetNet domain. (See ES3
in figure below)
</t>
</list>
</t>
<t>
L3 (IP) end systems may use any of these connection types. DetNet
domain MUST allow communication between any end-systems using the
same encapsulation format, independent of their connection type and
DetNet capability. DN attached end systems have no knowledge about
the DetNet domain and its encapsulation format. See <xref
target="fig_es_con_types"/> for L3 end system connection scenarios.
</t>
<figure title="Connection types of L3 end systems" anchor="fig_es_con_types">
<artwork align="center"><![CDATA[
____+----+
+----+ _____ / | ES3|
| ES1|____ / \__/ +----+___
+----+ \ / \
+ |
____ \ _/
+----+ __/ \ +__ DetNet domain /
| ES2|____/ L2/L3 |___/ \ __ __/
+----+ \_______/ \_______/ \___/
]]>
</artwork></figure>
<section title="DetNet Routers" anchor="detrouting">
<t>
Within a DetNet domain, the DetNet enabled IP Routers
interconnect links and sub-networks to support end-to-end
delivery of DetNet flows. From a DetNet architecture
perspective, these routers are DetNet relays, as they must
be DetNet service aware. Such routers identify DetNet flows
based on the IP 6-tuple, and ensure that the DetNet service
required traffic treatment is provided both on the node and
on any attached sub-network.
</t>
<t>
This solution provides DetNet functions end to end, but does so on
a per link and sub-network basis. Congestion protection and
latency control and the resource allocation (queuing, policing,
shaping) are supported using the underlying link / sub net
specific mechanisms. However, service protections (packet
replication and packet elimination functions) are not provided at
the DetNet layer end to end. But such service protection can be
provided on a per underlying L2 link and sub-network basis.
</t>
<figure title="Encapsulation of DetNet Routing in simplified IP service L3 end-systems"
anchor="fig_simple_iprouting">
<artwork align="center"><![CDATA[
+------+ +------+
| X | | X |
+======+ +------+
End-system | IP | | IP |
-----+------+-------+======+--- --+======+--
DetNet |L2/SbN| |L2/SbN|
+------+ +------+
]]>
</artwork></figure>
<t>
The DetNet Service Flow MUST be mapped to the link / sub-network
specific resources using an underlying system specific
means. This implies each DetNet aware node on path MUST look
into the transported DetNet Service Flow packet and utilize
e.g., a 5- (or 6-) tuple to find out the required mapping within
a node.
</t>
<t>
As noted earlier, the Service Protection is done within each
link / sub-network independently using the domain specific
mechanisms (due the lack of a unified end to end sequencing
information that would be available for intermediate nodes).
Therefore, service protection (if any) cannot be provided
end-to-end, only within sub-networks. This is shown for a three
sub-network scenario in <xref target="fig_pref_in_subnets"/>,
where each sub-network can provide service protection between
its borders.
</t>
<figure title="Replication and elimination in sub-networks for DetNet IP networks" anchor="fig_pref_in_subnets">
<artwork align="center">
<![CDATA[
______
____ / \__
____ / \__/ \___ ______
+----+ __/ +====+ +==+ \ +----+
|src |__/ SubN1 ) | | \ SubN3 \____| dst|
+----+ \_______/ \ Sub-Network2 | \______/ +----+
\_ _/
\ __ __/
\_______/ \___/
+---+ +---------E--------+ +-----+
+----+ | | | | | | | +----+
|src |----R E--------R +---+ E------R E------+ dst|
+----+ | | | | | | | +----+
+---+ +-----R------------+ +-----+
]]>
</artwork></figure>
<t>
If end to end service protection is desired that can be
implemented, for example, by the DetNet end systems using
Layer-4 (L4) transport protocols or application
protocols. However, these are out of scope of this document.
</t>
</section>
</section>
<section title="Networks with multiple technology segments" anchor="nwsegments">
<!-- alternate title:
"Mapping IP DetNet Flows to Sub-Networks and Links">
-->
<t>
There are network scenarios, where the DetNet domain contains
multiple technology segments (IEEE 802.1 TSN, MPLS) and all those
segments are under the same administrative control (see <xref
target="fig_pref_xcrs_segments"/>). Furthermore, DetNet nodes may be
interconnected via TSN segments.
</t>
<t>
DetNet routers ensure that detnet service requirements are
met per hop by allocating local resources, both receive and
transmit, and by mapping the service requirements of each
flow to appropriate sub-network mechanisms. Such mapping is
sub-network technology specific. The mapping of IP DetNet
Flows to MPLS is covered <xref
target="I-D.ietf-detnet-dp-sol-mpls"/>. The mapping of IP
DetNet Flows to IEEE 802.1 TSN is covered in <xref
target="mapping-tsn"/>.
</t>
<figure title="DetNet domains and multiple technology segments" anchor="fig_pref_xcrs_segments">
<artwork align="center"><![CDATA[
______
_____ / \__
____ / \__/ \___ ______
+----+ __/ +======+ +==+ \ +----+
|src |__/ Seg1 ) | | \ Seg3 \__| dst|
+----+ \_______+ \ Segment-2 | \+_____/ +----+
\======+__ _+===/
\ __ __/
\_______/ \___/
]]>
</artwork></figure>
</section>
<section title="OAM">
<t>
[Editor's note: This section is TBD. OAM may be dropped from
this document and left for future study.]
</t>
</section>
<section title="Class of Service">
<t>
Class and quality of service, i.e., CoS and QoS, are terms that are
often used interchangeably and confused. In the context of DetNet,
CoS is used to refer to mechanisms that provide traffic forwarding
treatment based on aggregate group basis and QoS is used to refer
to mechanisms that provide traffic forwarding treatment based on a
specific DetNet flow basis. Examples of existing network level CoS
mechanisms include DiffServ which is enabled by IP header
differentiated services code point (DSCP) field <xref
target="RFC2474"/> and MPLS label traffic class field <xref
target="RFC5462"/>, and at Layer-2, by IEEE 802.1p priority code
point (PCP).
</t>
<t>
CoS for DetNet flows carried in IPv6 is provided using the standard
differentiated services code point (DSCP) field <xref
target="RFC2474"/> and related mechanisms. The 2-bit explicit
congestion notification (ECN) <xref target="RFC3168"/> field MAY
also be used.
</t>
<t>
One additional consideration for DetNet nodes which support CoS
services is that they MUST ensure that the CoS service classes do
not impact the congestion protection and latency control mechanisms
used to provide DetNet QoS. This requirement is similar to
requirement for MPLS LSRs to that CoS LSPs do not impact the
resources allocated to TE LSPs via <xref target="RFC3473"/>.
</t>
</section>
<section title="Quality of Service" anchor="QoS">
<t>
Quality of Service (QoS) mechanisms for flow specific traffic
treatment typically includes a guarantee/agreement for the service,
and allocation of resources to support the service. Example QoS
mechanisms include discrete resource allocation, admission control,
flow identification and isolation, and sometimes path control, traffic
protection, shaping, policing and remarking. Example protocols that
support QoS control include <xref target="RFC2205">Resource
ReSerVation Protocol (RSVP)</xref> (RSVP) and RSVP-TE <xref
target="RFC3209"/> and <xref target="RFC3473"/>. The existing MPLS
mechanisms defined to support CoS <xref target="RFC3270"/> can also be
used to reserve resources for specific traffic classes.
</t>
<t>
In addition to explicit routes, and packet replication and
elimination, DetNet provides zero congestion loss and bounded latency
and jitter. As described in <xref
target="I-D.ietf-detnet-architecture"/>, there are different
mechanisms that maybe used separately or in combination to deliver a
zero congestion loss service. These mechanisms are provided by the
either the MPLS or IP layers, and may be combined with the mechanisms
defined by the underlying network layer such as 802.1TSN.
</t>
<t>
A baseline set of QoS capabilities for DetNet flows carried in PWs
and MPLS can provided by MPLS with Traffic Engineering (MPLS-TE)
<xref target="RFC3209"/> and <xref target="RFC3473"/>. TE LSPs can
also support explicit routes (path pinning). Current service
definitions for packet TE LSPs can be found in "Specification of
the Controlled Load Quality of Service", <xref target="RFC2211"/>,
"Specification of Guaranteed Quality of Service", <xref
target="RFC2212"/>, and "Ethernet Traffic Parameters", <xref
target="RFC6003"/>. Additional service definitions are expected in
future documents to support the full range of DetNet services.
In all cases, the existing label-based marking mechanisms defined
for TE-LSPs and even E-LSPs are use to support the identification
of flows requiring DetNet QoS.
</t>
<t>
QoS for DetNet service flows carried in IP MUST be provided locally by
the DetNet-aware hosts and routers supporting DetNet flows. Such
support will leverage the underlying network layer such as
802.1TSN. The traffic control mechanisms used to deliver QoS for
IP encapsulated DetNet flows are expected to be defined in a future
document. From an encapsulation perspective, the combination of the "6 tuple" i.e.,
the typical 5 tuple enhanced with the DSCP code, uniquely identifies a DetNet
service flow.
</t>
<t>
Packets that are marked with a DetNet Class of Service value, but that have not been
the subject of a completed reservation, can disrupt the QoS offered to properly
reserved DetNet flows by using resources allocated to the reserved flows. Therefore,
the network nodes of a DetNet network must:
<list style="symbols">
<t>
Defend the DetNet QoS by discarding or remarking (to a non-DetNet CoS)
packets received that are not the subject of a completed reservation.
</t><t>
Not use a DetNet reserved resource, e.g. a queue or shaper reserved for
DetNet flows, for any packet that does not carry a DetNet Class of Service
marker.
</t>
</list>
</t>
</section>
<section title="Cross-DetNet flow resource aggregation" anchor="aggregation">
<t>
The ability to aggregate individual flows, and their associated
resource control, into a larger aggregate is an important technique
for improving scaling of control in the data, management and
control planes. This document identifies the traffic identification
related aspects of aggregation of DetNet flows. The resource
control and management aspects of aggregation (including the
queuing/shaping/policing implications) will be covered in other
documents. The data plane implications of aggregation are
independent for PW/MPLS and IP encapsulated DetNet flows.
</t>
<t>
DetNet flows transported via IP have more limited aggregation
options, due to the available traffic flow identification fields of
the IP solution.
One available approach is to manage the resources
associated with a DSCP identified traffic class and to map (remark)
individually controlled DetNet flows onto that traffic class. This
approach also requires that nodes support aggregation ensure that
traffic from aggregated LSPs are placed (shaped/policed/enqueued)
in a fashion that ensures the required DetNet service is preserved.
</t>
<t>
In both the MPLS and IP cases, additional details of the traffic control
capabilities needed at a DetNet-aware node may be covered in the
new service descriptions mentioned above or in separate future
documents. Management and control plane mechanisms will also need
to ensure that the service required on the aggregate flow (H-LSP or
DSCP) are provided, which may include the discarding or remarking
mentioned in the previous sections.
</t>
</section>
<!-- ===================================================================== -->
<section title="Time synchronization">
<t>
While time synchronization can be important both from the perspective of
operating the DetNet network itself and from the perspective of
DetNet-based applications, time synchronization is outside the
scope of this document. This said, a DetNet node can also support
time synchronization or distribution mechanisms.
</t>
<t>
For example, <xref target="RFC8169"/> describes a method
of recording the packet queuing time in an MPLS LSR on a packet by
per packet basis and forwarding this information to the egress edge
system. This allows compensation for any variable packet queuing
delay to be applied at the packet receiver. Other mechanisms for
IP networks are
defined based on IEEE Standard 1588 <xref target="IEEE1588"/>,
such as ITU-T <xref target="G.8275.1"/> and <xref target="G.8275.2"/>.
</t>
<t>
A more detailed discussion of time synchronization is outside the
scope of this document.
</t>
</section>
</section>
<!-- ===================================================================== -->
<section title="Management and control plane considerations" anchor="m-cp-considerations">
<t>
[Editor's note: This section needs to be different for MPLS and
IP solutions. Most solutions are technology dependent.]
</t>
<t>
While management plane and control plane are traditionally
considered separately, from the Data Plane perspective there is no
practical difference based on the origin of flow provisioning
information. This document therefore does not distinguish between
information provided by a control plane protocol, e.g., RSVP-TE <xref
target="RFC3209"/> and <xref target="RFC3473"/>, or by a network
management mechanisms, e.g., RestConf <xref target="RFC8040"/> and
YANG <xref target="RFC7950"/>.
</t>
<t>
[Editor's note: This section is a work in progress.
discuss here what kind of enhancements are needed for DetNet
and specifically for PREOF and DetNet zero congest loss and latency
control. Need to cover both traffic control (queuing) and connection
control (control plane).]
</t>
<!-- section title="IP-based data plane">
<t>
[Editor's note: Merge with earlier text.]
</t -->
<section title="Explicit routes">
<t>
[Editor's note: this is TBD.]
</t>
</section>
<section title="Service protection">
<t>
[Editor's note: this is TBD.]
</t>
</section>
<!-- /section -->
<section title="Congestion protection and latency control">
<t>
[Editor's note: this is TBD.]
</t>
</section>
<section title="Flow aggregation control">
<t>
[Editor's note: this is TBD.]
</t>
</section>
<section title="Bidirectional traffic">
<t>
[Editor's note: This is managed at the management plane or controller
level.]
</t>
<t>
Some DetNet applications generate bidirectional traffic. While the
DetNet data plane must support bidirectional DetNet flows, there are
no special bidirectional features with respect to the data plane
other than need for the two directions take the same paths. That is
to say that bidirectional DetNet flows are solely represented at the
management and control plane levels, without specific support or
knowledge within the DetNet data plane. Fate sharing and associated
vs co-routed bidirectional flows can be managed at the control
level. Note, that there is no stated requirement for bidirectional
DetNet flows to be supported using the same 6-tuple in each
direction. Control mechanisms will need to support such
bidirectional flows but such mechanisms are out of scope of this
document. An example control plane solution for MPLS can be found
in <xref target="RFC7551"/>.
</t>
</section>
</section>
<!-- ===================================================================== -->
<section anchor="ip-procs" title="DetNet IP Data Plane Procedures">
<t>
This section provides DetNet IP data plane procedures. These
procedures have been divided into the following areas: flow
identification, forwarding and traffic treatment. Flow
identification includes those procedures related to matching IP
and higher layer protocol header information to DetNet flow
(state) information and service requirements. Flow
identification is also sometimes called Traffic classification,
for example see <xref target="RFC5777"/>. Forwarding includes
those procedures related to next hop selection and
delivery. Traffic treatment includes those procedures related to
providing an identified flow with the required DetNet service.
</t>
<t>
DetNet IP data plane procedures also have implications on the
control and management of DetNet flows and these are also
covered in this section. Specifically this section identifies a
number of information elements that will require support via the
management and control interfaces supported by a DetNet node.
The specific mechanism used for such support is out of the scope
of this document. A summary of the management and control
related information requirements is included. Conformance
language is not used in the summary as it applies to future
mechanisms such as those that may be provided in YANG models
[YANG-REF-TBD].
</t>
<section anchor="ip-flow-id"
title="DetNet IP Flow Identification Procedures">
<t>
IP and higher layer protocol header information is used to
identify DetNet flows. All DetNet implementations that support
this document MUST identify individual DetNet flows based on
the set of information identified in this section. Note, that
additional flow identification requirements, e.g., to support
other higher layer protocols, may be defined in future.
</t>
<t>
The configuration and control information used to identify an
individual DetNet flow MUST be ordered by an implementation.
Implementations MUST support a fixed order when identifying
flows, and MUST identify a DetNet flow by the first set of
matching flow information.
</t>
<t>
Implementations of this document MUST support DetNet flow
identification when the implementation is acting as a
DetNet end systems, a relay node or as an edge node.
</t>
<section title="IP Header Information">
<t>
Implementations of this document MUST support DetNet flow
identification based on IP header information. The IPv4
header is defined in <xref target="RFC0791"/> and the IPv6
is defined in <xref target="RFC8200"/>.
</t>
<section title="Source Address Field">
<t>
Implementations of this document MUST support DetNet flow
identification based on the Source Address field of an IP
packet. Implementations SHOULD support longest prefix
matching for this field, see <xref target="RFC1812"/> and
<xref target="RFC7608"/>. Note that a prefix length of
zero (0) effectively means that the field is ignored.
</t>
</section>
<section title="Destination Address Field">
<t>
Implementations of this document MUST support DetNet flow
identification based on the Destination Address field of an IP
packet. Implementations SHOULD support longest prefix
matching for this field, see <xref target="RFC1812"/> and
<xref target="RFC7608"/>. Note that a prefix length of
zero (0) effectively means that the field is ignored.
</t>
<t>
Note: using IP multicast destination address is also allowed.
</t>
</section>
<section anchor="nxt-proto-field"
title="IPv4 Protocol and IPv6 Next Header Fields">
<t>
Implementations of this document MUST support DetNet flow
identification based on the IPv4 Protocol field when
processing IPv4 packets, and the IPv6 Next Header Field
when processing IPv6 packets. An implementation MUST
support flow identification based based the next protocol
values defined in <xref target="nxt-proto"/>. Other,
non-zero values, SHOULD be used for flow identification.
Implementations SHOULD allow for these fields to be
ignored for a specific DetNet flow.
</t>
</section>
<section title="IPv4 Type of Service and IPv6 Traffic Class Fields">
<t>
These fields are used to support Differentiated Services
<xref target="RFC2474"/> and Explicit Congestion
Notification <xref target="RFC3168"/>. Implementations of
this document MUST support DetNet flow identification
based on the IPv4 Type of Service field when processing
IPv4 packets, and the IPv6 Traffic Class Field when
processing IPv6 packets. Implementations MUST support
bimask based matching, where one (1) values in the bitmask
indicate which subset of the bits in the field are to be
used in determining a match. Note that a zero (0) value as
a bitmask effectively means that these fields are ignored.
</t>
</section>
<section title="IPv6 Flow Label Field">
<t>
[Authors note: the use of the IPv6 flow label is TBD this
section requires discussion. Flow label based mapping requires
src/dst adress mapping as well.]
</t>
<t>
Implementations of this document SHOULD support
identification of DetNet flows based on the IPv6 Flow
Label field. Implementations that support matching based
on this field MUST allow for this fields to be ignored for
a specific DetNet flow. When this fields is used to
identify a specific DetNet flow, implementations MAY
exclude the IPv6 Next Header field and next header
information as part of DetNet flow identification.
</t>
</section>
</section>
<section anchor="nxt-proto" title="Other Protocol Header Information">
<t>
Implementations of this document MUST support DetNet flow
identification based on header information identified in this
section. Support for TCP, UDP and IPsec flows are defined.
Future documents are expected to define support for other
protocols.
</t>
<t>
[Authors note: Other candidate protocols include
IP in IP, GRE, DCCP - should and of these be required
supported?]
</t>
<section title="TCP and UDP">
<t>
DetNet flow identification for TCP <xref
target="RFC0793"/> and UDP <xref target="RFC0768"/> is
done based on the Source and Destination
Port fields carried in each protocol's header. These
fields share a common format and common DetNet flow
identification procedures.
</t>
<section title="Source Port Field">
<t>
Implementations of this document MUST support DetNet flow
identification based on the Source Port field of a TCP or
UDP packet. Implementations MUST support flow
identification based on a particular value carried in the
field, i.e., an exact. Implementations SHOULD support
range-based port matching. Implementation MUST also allow
for the field to be ignored for a specific DetNet flow.
</t>
</section>
<section title="Destination Port Field">
<t>