Internet DRAFT - draft-pthubert-detnet-ipv6-hbh
draft-pthubert-detnet-ipv6-hbh
DetNet P. Thubert, Ed.
Internet-Draft Cisco Systems
Intended status: Standards Track F. Yang
Expires: 26 August 2022 Huawei Technologies
22 February 2022
IPv6 Options for DetNet
draft-pthubert-detnet-ipv6-hbh-07
Abstract
RFC 8938, the Deterministic Networking Data Plane Framework relies on
the 6-tuple to identify an IPv6 flow. But the full DetNet operations
require also the capabilities to signal meta-information such as a
sequence within that flow, and to transport different types of
packets along the same path with the same treatment, e.g.,
Operations, Administration, and Maintenance packets and/or multiple
flows with fate and resource sharing. This document introduces new
IPv6 options that signal that path and redundancy information to the
intermediate DetNet relay and forwarding nodes.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
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Internet-Drafts are draft documents valid for a maximum of six months
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This Internet-Draft will expire on 26 August 2022.
Copyright Notice
Copyright (c) 2022 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
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and restrictions with respect to this document. Code Components
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 5
3. Applicability . . . . . . . . . . . . . . . . . . . . . . . . 5
4. The DetNet Options . . . . . . . . . . . . . . . . . . . . . 7
4.1. DetNet Redundancy Information Option . . . . . . . . . . 8
4.2. DetNet Path Options . . . . . . . . . . . . . . . . . . . 12
4.2.1. DetNet Strict Path Option . . . . . . . . . . . . . . 12
4.2.2. DetNet Loose Path Option . . . . . . . . . . . . . . 14
4.3. RPL Packet Information . . . . . . . . . . . . . . . . . 15
5. Encapsulation of DetNet Options . . . . . . . . . . . . . . . 15
5.1. IPv6 Network . . . . . . . . . . . . . . . . . . . . . . 15
5.2. Segment Routing over IPv6 Network . . . . . . . . . . . . 17
6. Security Considerations . . . . . . . . . . . . . . . . . . . 18
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 18
7.1. New Subregistry for the Redundancy Type . . . . . . . . . 19
7.2. New Hop-by-Hop Options . . . . . . . . . . . . . . . . . 19
8. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 20
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 20
9.1. Normative References . . . . . . . . . . . . . . . . . . 20
9.2. Informative References . . . . . . . . . . . . . . . . . 21
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 23
1. Introduction
Section 2 of the Deterministic Networking Problem Statement
[DetNet-PBST] introduces the concept of Deterministic Networking
(DetNet) to the IETF. DetNet extends the reach of lower layer
technologies such as Time-Sensitive Networking (TSN) [IEEE 802.1 TSN]
and Timeslotted Channel Hopping (TSCH) [IEEE Std. 802.15.4] over IPv6
and MPLS [RFC8938], to provide bounded latency and reliability
guarantees over an end-to-end layer-3 nailed-down path.
The "Deterministic Networking Architecture" [DetNet-ARCH] details the
contribution of layer-3 protocols, and defines three planes: the
Application (User) Plane, the Controller Plane, and the Network
Plane. [DetNet-ARCH] places an emphasis on the centralized model
whereby a controller instantiates a DetNet state in the routers that
is located based on matching information in the packet.
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The "Deterministic Networking Data Plane Framework" [RFC8938] relies
on the 6-tuple to identify an IPv6 flow. But the full DetNet
operations require also the capabilities to signal meta-information
such as a sequence within that flow, and to transport different types
of packets along the same path with the same treatment. For
instance, it is required that Operations, Administration, and
Maintenance (OAM) [RFC6291] packets and/or multiple flows share the
same fate and resource sharing over the same Track or the same
Traffic Engineered (TE) [RFC3272] DetNet path. This document
proposes a layer-3 signaling that is independent of the upper layer
information, to locate the DetNet state and enable the same
forwarding nehavior for the data flows and the OAM packets.
The "6TiSCH Architecture" [6TiSCH-ARCH] leverages RPL, the "Routing
Protocol for Low Power and Lossy Networks" [RPL] and introduces
concept of a Track as a highly redundant RPL Destination Oriented
Directed Acyclic Graph (DODAG) rooted at the Track Ingress. The
Track is indicative of a layer-3 forwarding behavior (e.g., next
hops)as opposed to indicative of the upper layer content, so it is
more in line with the DetNet needs than the 6-tuple.
A Track may for instance be installed using RPL route projection
[RPL-PDAO]. In that case, the TrackId is an index from a namespace
associated to one IPv6 address of the Track Ingress node, and the
Track that an IPv6 packet follows is signaled by the combination of
the source address (of the Track Ingress node), and the TrackID
placed in a RPL Option [RFC6553] located in an IPv6 Hop-by-Hop (HbH)
Options Header [IPv6] in the IPv6 packet.
The "Reliable and Available Wireless (RAW) Architecture/Framework"
[RAW-ARCH], extends the DetNet Network Plane to accomodate one or
multiple hops of homogeneous or heterogeneous wireless technologies,
e.g. a Wi-Fi6 Mesh or parallel radio access links combining Wi-Fi and
5G. The RAW Architecture reuses the concept of Track and introduces
a new dataplane component, the Path Selection Engine (PSE), to
dynamically select a subpath and maintain the required quality of
service within a Track in the face of the rapid evolution of the
medium properties.
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With [IPv6], the behavior of a router upon an IPv6 packet with a HbH
Options Header has evolved, making the examination of the header by
routers along the path optional, as opposed to previously mandatory.
Additionally, the Option Type for any option in a HbH Options Header
encodes in the leftmost bits whether a router that inspects the
header should drop the packet or ignore the option when encountering
an unknown option. Combined, these capabilities enable a larger use
of the header beyond the boundaries of a limited domain, as
examplified by the change of behavior of the RPL data plane, that was
changed to allow a packet with a RPL option to escape the RPL domain
in the larger Internet [RFC9008].
"IPv6 Hop-by-Hop Options Processing Procedures" [HbH-UPDT] further
specifies the procedures for how IPv6 Hop-by-Hop options are
processed to make their processing even more practical and increase
their use in the Internet. In that context, it makes sense to
consider Hop-by-Hop Options to transport the information that is
relevant to DetNet.
As opposed to the HbH EH, the Destination Option Header (DOH) is only
read by the destination of the packet, which can be one at a time the
collection of nodes listed in a Routing Extension Header (RH) if the
DOH is placed before the RH.
This document introduces new IPv6 Options, the DetNet Redundancy
Information Option and the DetNet Path Options, that signal the
DetNet information to the intermediate DetNet nodes in an abstract
form, that is pure layer-3 and agnostic of the transport layer. The
options are placed in either a HbH EH or in a DOH, which happens when
the next node that needs to process the option is the IPv6
destination in the IPv6 header.
This pure layer-3 technique alines DetNet with the IPv6 architecture
and opens to the progress / extensions done elsewhere for IPv6; e.g.,
if the DetNet path leverages Segment routing (SRv6) [RFC8402] for
some reason - there are plausible ones in RAW -, the Segment Routing
Header (SRH) [RFC8754] is inserted after the HbH and/or DOH by the PE
and both are readily accessible for the on-path routers without the
need of a deeper inspection of the packet (up to and beyond the
transport header).
For instance, the DetNet Redundancy Information Option may be placed
in a DOH before an SRH that signals the exhaustive list of the DetNet
relays along the path of the packet, so every relay can process the
redundancy information therein, while the DetNet Strict Path Option
would be placed in an HbH EH to be read by every DetNet forwarding
node, and intercepted should it strays away from its path.
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2. Terminology
Timestamp semantics and timestamp formats used in this document are
defined in "Guidelines for Defining Packet Timestamps" [RFC8877].
The Deterministic Networking terms used in this document are defined
in the "Deterministic Networking Architecture" [DetNet-ARCH].
The terms Track and TrackID are defined in the "6TiSCH Architecture"
[6TiSCH-ARCH].
3. Applicability
The "Deterministic Networking (DetNet) Data Plane: IP" [RFC8939]
illustrates the need for DetNet Services at the IP network layer in
conformance to the DetNet architecture [DetNet-ARCH] and data plane
framework [RFC8938]). As the specification does not introduce a new
header for DetNet, it also lacks the capability to signal PREOF at
the network layer. Instead, the information of application flows
(the 6-tuple), on which the network layer has no control, is used
directly to makes network layer forwarding decisions. This confuses
the signaling of the application-layer "water" that being transported
and with the network-layer "pipe" that transports it and makes it
problematic to aggregate applications flows and OAM for a equal
treatment. It is thus desirable to introduce a new signaling to
enable PREOF and flow aggregation independently of the application
flow that is more appropriate for network layer operations.
[I-D.varga-detnet-ip-preof] provides a methods for signaling PREOF
over UDP that combines the MPLS PREOF signaling defined in "DetNet
Data Plane: MPLS" [RFC8964] and the mechanisms defined in "DetNet
Data Plane: MPLS over UDP/IP" [RFC9025]. This approach provides IP
version independence, allows to reuse MPLS structures and possibly to
bridge MPLS DetNet flows onto IP with minimal mapping effort. It is
thus specially valuable in environments where flows can be
transported in any combination of MPLS and IP. OTOH, the signaled
information inherits the limitations of MPLS in terms of stack
structure, and is available after the transport header, which can be
harder to reach for a hardware solution, in particular in the
presence of a variable header chain at the network layer.
This draft proposes a native IPv6 solution that transports enriched
DetNet PREOF information in IPv6 Extension Headers. This method
reduces the encapsulation overhead, can be combined with the use of
"IPv6 Segment Routing (SRv6) Header (SRH)" [RFC8754], and simplifies
the access to the PREOF data by placing it early in the network
header chain. The forwarding information (the path) is advertised
independently of the application flow information (observable as the
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6-tuple). This enables any mix and match of flows and OAM data over
the same path with the same treatment. The method is thus suited for
environments that are IPv6-only, where flows can be aggregated over
larger pipes and disaggregated again, but it is harder to combine
with MPLS and requires that all nodes on path can parse at least the
IPv6 Extension Header that signal the path.
Transported in IPv6 Extension Headers, the DetNet options are easier
to reach for a hardware or otherwise constrained implementation. A
DetNet-aware end-system (see section 4.2 of [DetNet-ARCH]) may place
the options in the header chain when constructing the packet, in
which case there is no need of an encapsulation.
Alternatively, the source end system may signal the flow information
some other way, or it may lack the full DetNet awareness; in that
case the DetNet path endpoints are the provider Edge (PE) routers
(see Figure 1 reproducing figure 5 of [DetNet-ARCH]) and the Ingress
PE needs to encapsulate the packets to add the HbH options.
In Figure 1, the DetNet end systems may be f-aware and signal an IPv6
flow using the 6-tuple for the End-to-End service, but may not be
s-aware, and may not sequence the packets for Packet Replication,
Elimination, and Ordering Functions (PREOF), which operate at the
detNet Service Layer. In that case, the Ingress PE will encapsulate
the packets for this and possibly other flows to provide a common
DetNet Service with OAM and PREOF, across the DetNet-1 service
provider network, terminating the tunnel at the Egress PE router.
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_
/ \ +----DetNet-UNI (U) / \
/App\ | /App\
/-----\ | /-----\
| NIC | v ________ | NIC |
+--+--+ _____ / \ DetNet-UNI (U) --+ +--+--+
| / \__/ \ | |
| / +----+ +----+ \_____ | |
| / | | | | \_______ | |
+------U PE +----+ P +----+ \ _ v |
| | | | | | | ___/ \ |
| +--+-+ +----+ | +----+ | / \_ |
\ | | | | | / \ |
\ | +----+ +--+-+ +--+PE |------ U-----+
\ | | | | | | | | | \_ _/
\ +---+ P +----+ P +--+ +----+ | \____/
\___ | | | | /
\ +----+__ +----+ DetNet-1 DetNet-2
| \_____/ \___________/ |
| |
| | End-to-End Service | | | |
<------------------------------------------------------------->
| | DetNet Service | | | |
| <------------------------------------------------> |
| | | | | |
Figure 1: Figure 5 of RFC 8655, Reproduced
4. The DetNet Options
This document defines new IPv6 options for DetNet to signal path and
a reliability information (e.g., sequencing) to the DetNet layers.
Those options are to be placed in the IPv6 HbH Options Header, which
is found right after the outer IPv6 header in the DetNet packet and
immediately reachable for the forwarding engine. The format of the
options follow the generic definition in section 4.2 of [IPv6]. For
each tyoe of option, the draft allows to express the information in
different fashions, depending on the use case, and possibly carrying
an information that plays the same role at another layer, in which
case the format of the information is opaque.
The reliability information may be inherited from another layer as
long as the value is guaranteed to be unique within a reasonable set
of sequential packet so all packets with the same value are
redundant. Timestamping can be used as an alternate sequencing
technique, that avoids maintaining per-path state at the path
ingress, which is feasible for nodes that maintain a very precise
sense of time (e.g., from GPS or PTP) for their DetNet operations.
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As long as the time granularity is in the order of a few bytes
transmission, the system timestamp provides an absolute sense of
ordering over a very long period across all paths for which this node
is ingress, and thus within any of those. Alternatively, the draft
allows to combine a rough time stamp (e.g., from a system clock
synchronized by NTP) and a sequence counter that differntiates the
packets that are stamped within the timer resolution.
If a DetNet Path option (see Section 4.2), including the RPL Option,
is present in the same HbH Option Header as a DetNet Redundancy
Information option (see Section 4.1), then the redundancy information
applies to the signaled path across all flows that traverse that
path; else the redundancy information applies to the flow indicated
by the 6-tuple [RFC8938].
4.1. DetNet Redundancy Information Option
The DetNet Redundancy Information Option helps discriminate copies of
a same packet vs. different packets, and is useful for service-
sublayer Packet Replication Elimination and Ordering Functions
(PREOF). The option may be placed either in an HbH or a DoH EH,
e.g., prior to a Segment Routing Header (SRH) [RFC8754] that lists
the DetNet relays. A sequence counter is probably the most typical
expression of the redundancy information, but it is not the only way
to identify a packet and/or enable reordering, e.g., a timestamp can
be seen as a large sequence counter with gaps.
It is also possible that a packet is divided in elements such as
network-coded fragments. In that case, the pieces are discriminated
with an opaque 8-bit fragment tag. The goal is to retain one copy of
each fragment but not reorder them.
A packet sequence can be expressed uniquely as a wrapping counter,
represented as an unsigned integer in the option. In that case, the
size of the representation MUST be large enough to cover at least 3
times the upper bound on out-of-order packet delivery in terms of
number of packets. The sequence counter may be copied from a field
in another protocol, and it is possible that the value 0 is reserved
when wrapping, to the option offers both possibilities, wrapping to
either 0 or to 1.
This specification also allows to use a time stamp for the packet
redundancy information, in conformance with the recommendations in
[RFC8877]. This can be accomplished by utilizing the Precision Time
Protocol (PTP) format defined in IEEE Std. 1588 [IEEE Std. 1588] or
Network Time Protocol (NTP) [RFC5905] formats. In that case, the
timestamp resolution at the origin node that builds the option MUST
be fine enough to ensure that two consecutive packets are never
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stamped with the same value. There is no requirement for this
particular stamping function that the sense of time at the origin
node is synchronized with the rest of the DetNet network.
IEEEE TSN [IEEE 802.1 TSN] defined a redundancy tag (R-Tag) for the
IEEE Std. 802.1CB Frame Replication and Elimination for Reliability
(FRER). The R-Tag is a structured field and its content is subject
to evolve; but the expectation for this specification is that the
overall size remains 48 bits and that the 48-bit value is different
for a large number of contiguous frames. When transporting TSN
frames in a DetNet packet, it is possible to leverage the R-Tag as
Redundancy information, though it cannot be assumed that the R-Tag is
sequentially incremented; so it can be used for packet duplicate
elimination but it is not suitable not for packet re-ordering.
This specification also allows for an hybrid model with a coarse
grained packet sequence within a coarse grained time stamp. In that
case, both a time stamp option and a wrapping counter options are
found, and the counter is used to compare packets with the same time
stamp and ignored otherwise In that case, the size of the
representation of the counter MUST be large enough to cover at least
3 times the number of packets that may be sent with the same value of
time stamp.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Option Type | Opt Data Len | R.I. Type | Fragment Tag |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
. .
. Redundancy Information (variable Size) .
. .
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 2: Redundancy Information Option Format
Redundancy Information Option fields:
Option Type: 8-bit identifier of the type of option. Value TBD by
IANA; if the processing IPv6 node does not recognize the Option
Type it MUST skip over this option and continue processing the
header (act =00); the Option Data of that option cannot change en
route to the packet's final destination (chg=0). The
Opt Data Len: 8-bit length of the option data.
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Fragment Tag: 8-bit field, set to 0 when the packet is sent in
entirety; packets with the same Redundancy Information and
different fragments tags MUST be considered as different by the
elimination function and are not subject to ordering based on the
Tag.
Redundancy Information Type: 8-bit identifier of the type of
Redundancy information. Value to be confirmed by IANA.
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+=======+============+===============+===========================+
| Seq. | Category | Common Name | Redundancy |
| Type | | | Information Format |
| Value | | | |
+=======+============+===============+===========================+
| 1 | Wrapping | Basic | 32-bit unsigned |
| | Counter | Sequence | integer |
| | | Counter | |
+-------+============+---------------+---------------------------+
| 2 | Wrapping | Zero-avoiding | 32-bit unsigned |
| | Counter | Sequence | integer, wraps to 1 |
| | | Counter | |
+-------+============+---------------+---------------------------+
| 3 | Wrapping | RPL Sequence | 8-bit RPL sequence, |
| | Counter | Counter | see section 7. of |
| | | | [RPL] |
+-------+============+---------------+---------------------------+
| 11 | Time Stamp | Fractional | NTP 64-bit Timestamp |
| | | NTP | Format, see section |
| | | | 4.2.1. of [RFC8877] |
+-------+============+---------------+---------------------------+
| 12 | Time Stamp | Short NTP | NTP 32-bit Timestamp |
| | | | Format, see section |
| | | | 4.2.2. of [RFC8877] |
+-------+============+---------------+---------------------------+
| 13 | Time Stamp | PTP | PTP 80-bit Timestamp |
| | | | Format, see [IEEE |
| | | | Std. 1588] |
+-------+============+---------------+---------------------------+
| 14 | Time Stamp | Short PTP | PTP 64-bit Truncated |
| | | | Timestamp Format, |
| | | | see section 4.3. of |
| | | | [RFC8877] |
+-------+============+---------------+---------------------------+
| 24 | Structured | TSN | 48-bit opaque |
| | Unique Tag | Redundancy | |
| | | Tag | |
+-------+============+---------------+---------------------------+
Table 1: Redundancy Information Type values (suggested)
Redundancy Information: Variable size, as indicated in Table 1.
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4.2. DetNet Path Options
The DetNet Architecture [DetNet-ARCH] assigns a DetNet flow "to
specific paths through a network", but is not specific on how the
path is then signaled in the packet. The DetNet Data Plane Framework
[RFC8938] relies on the 6-tuple to identify an IPv6 flow and
implicitely the path could be indexed by the flow identification.
But this requires to maintain one path per flow and makes it
difficult to assign other traffic such as OAM to the same path.
This draft provides aditional means to signal the path in which the
flow is placed separately from the flow indentification, and
independantly of the transport layer, so a path can be shared between
one or more flows and OAM packets across IP address families. All
the packets that are assigned to the same path are subject to the
same DetNet forwarding treatment.
the DetNet expectation is that a PCE sets up a state at the DetNet
forwarding sublayer to instruct each hop on how to process the DetNet
flows. The DetNet Path Options when present contains information
that MUST be used to select the DetNet state installed and if the
DetNet state does not exist then the packet cannot be forwarded.
4.2.1. DetNet Strict Path Option
In complement to the RPL option, this specification defines a
protocol-independent Strict Path Identifier, which is also taken from
a namespace indicated by the IPv6 source address of the packet.
The DetNet Strict Path Option is to be used in a limited domain to
indicate a routing state that must be present in all nodes to ensure
that the packet is routed along a strictly predefined path, for
instance pointing at a specific next hop with reserved resources for
buffers and bandwidth. For that reason all the routers along the
path are expected to support the option and own a state indexed by
the Strict Path ID indicated therein.
The option is placed in an HbH EH to be seen by all routers on path.
The path indicated therein may also be used by the service sublayer,
to signal the scope where the redundancy information is unique across
a number of packets large enough to ensure that a forwarding node
never has to handle different packets with the same redundancy
information, though the same value may be found for packets with a
different path information.
The typical DetNet path is typically contained under a single
administrative control or within a closed group of administrative
control; these include campus-wide networks and private WANs
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[DetNet-ARCH]. The typical expectation is that all nodes along a
DetNet path are aware of the path and actively maintain a forwarding
state for it. The DetNet Strict Path Option (see Section 4.2.1) is
designed for that environment; if a packet escapes the local domain,
a router that does not support the option will intercept it and
return an error to the source.
In other environments such as RAW, it might be that the service-layer
protection concentrates on just segments of the end-to-end path. In
that case, the service-sublayer protection may require the signaling
of both redundancy and path information, though the path information
is potentially not used by some of the intermediate routers and may
not be used for forwarding at all. The path information may also
relate to segments that are installed along the path using a DetNet
forwarding state as opposed to, say, source routing. In either case
the DetNet Loose Path Option Section 4.2.2 can be used to signal the
path without incurring an ICMP Error from an intermediate node.
An intermediate router that supports the DetNet Strict Path Option
but is missing the necessary state to forward along the indicated
path must drop the packet and return an ICMP error.code 0 pointing at
the offset of the Strict Path ID in the DetNet Strict Path Option.
DetNet can also leverage the RPL Option that signals a Track in the
RPL Packet Information (RPI) [RFC6553]. There are 2 versions of the
RPL option, defined respectively in [RPL] with the act bits [IPv6]
set to dropped the packet when the option is unknown, that defined
in[RFC9008] which let the option be ignored.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Option Type | Opt Data Len | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 3: DetNet Strict Path Option Format
Redundancy Option fields:
Option Type: 8-bit identifier of the type of option. Value TBD by
IANA; if the processing IPv6 node does not recognize the Option
Type it must discard the packet and send an ICMP Parameter
Problem, Code 2, message to the packet's Source Address (act =10);
the Option Data of that option cannot change en route to the
packet's final destination (chg=0).
Opt Data Len: 8-bit length of the option data, set to 2.
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Strict Path ID: 16-bit identifier of the DetNet Path, taken from a
local namespace associated with the IPv6 source address of the
packet.
4.2.2. DetNet Loose Path Option
The DetNet Loose Path Option transports a Loose Path identifier which
is taken from a namespace indicated by the Origin Autonomous System
(AS). When the DetNet path is contained within a single AS, the
Origin Autonomous System field can be left to 0 indicating local AS.
The option may be placed either in an HbH or a DoH EH, but the
preferred method is a DOH that precedes an RH such as SRH.
The DetNet Loose Path Option is to be used to signal a path that may
be loose and may exceed the boundaries of a local domain; a portion
of the hops may traverse routers in the wider internet that will not
leverage the option and are expected to ignore it. For instance, the
path information may signal a specific topology in a multi-topology
network and is only important for nodes that participate to more than
one topology.
An intermediate router that supports the DetNet Loose Path Option but
is missing the necessary state to forward along the indicated path
must ignore the DetNet Loose Path Option, but it should raise a
management alert as this is an unexpected situation with a limited
chance that the packet may loop till TTL.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Option Type | Opt Data Len | Origin Autonomous System |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Loose Path ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 4: DetNet Loose Path Option Format
Redundancy Option fields:
Option Type: 8-bit identifier of the type of option. Value TBD by
IANA; if the processing IPv6 node does not recognize the Option
Type it MUST skip over this option and continue processing the
header (act =00); the Option Data of that option cannot change en
route to the packet's final destination (chg=0).
Opt Data Len: 8-bit length of the option data, set to 6.
Origin Autonomous System: 16-bit identifier of the Autonomous
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Systems (AS) that originates the path. The value of 0 signals a
DetNet path that is constrained within the local AS or the local
administrative DetNet domain.
Loose Path ID: 32-bit identifier of the DetNet Path, taken from a
local namespace associated with the origin AS of the DetNet path.
4.3. RPL Packet Information
6TiSCH [6TiSCH-ARCH] and RAW [RAW-ARCH] signal a Track using a RPL
Option [RFC6553] with a RPLInstanceID used as TrackID. This
specification reuses the RPL option as a method to signal a DetNet
path. In that case, the Projected-Route 'P' flag [RPL-PDAO] MUST be
set to 1, and the O, R, F flags, as well as the Sender Rank field,
MUST be set to 0 by the originator, forwarded as-is, and ignored on
reception.
5. Encapsulation of DetNet Options
In this section, encapsulations of three DetNet Options are specified
separately in the scenarios of pure IPv6 and SRv6.
5.1. IPv6 Network
The DetNet Strict Path Option is intended to be placed in an IPv6 HbH
EH since it must be processed by every DetNet forwarding node along
the path. The DetNet Loose Path Option and the DetNet Redundancy
Information Option may also carried in an IPv6 HbH Option header the
case where the set of routers that need the information does not
match the destinations along a source route path; those options are
intended to be ignored by unaware intermediate routers.
In the specific case where path selection and PREOF are end-to-end
performed between DetNet edge nodes, Redundancy Information Option
can be alternatively placed in IPv6 Destination Option header. The
encapsulation options are shown in Figure 5 and Figure 6.
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+-----------------------------------+
| DetNet App-Flow |
| (original IP) Packet |
+-----------------------------------+
| other EHs |
+-----------------------------------+ <--\
| IPv6 Hop-by-Hop Ex Hdr | |
| (DetNet RI Option) | DetNet Options
| (DetNet Strict/Loose Path Option) | |
+-----------------------------------+ <--/
| IPv6 Header |
+-----------------------------------+
| Data-Link |
+-----------------------------------+
| Physical |
+-----------------------------------+
Figure 5: DetNet IPv6 Option Encapsulation Alternative 1
+-----------------------------------+
| DetNet App-Flow |
| (original IP) Packet |
+-----------------------------------+
| other EHs such as RH |
+-----------------------------------+ <--\
| IPv6 Destination Ext Hdr | |
| (DetNet RI Option) | |
+-----------------------------------+ DetNet Options
| IPv6 Hop-by-Hop Ext Hdr | |
| (DetNet Strict/Loose Path Option) | |
+-----------------------------------+ <--/
| IPv6 Header |
+-----------------------------------+
| Data-Link |
+-----------------------------------+
| Physical |
+-----------------------------------+
Figure 6: DetNet IPv6 Option Encapsulation Alternative 2
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5.2. Segment Routing over IPv6 Network
In SRv6, partial or all of DetNet forwarding and relay nodes may be
represented by SRv6 SIDs to determine a specific path for a DetNet
flow. In the former case, DetNet Strict Path Option would be placed
in an HbH EH to be read by every DetNet forwarding node, and
intercepted should it strays away from its path. In the latter case,
three DetNet Options can be placed either in an HbH EH or in a DOH EH
before an SRH, as two encapsulation options are being functionally
equivalent, as shown in Figure 7 .
+-----------------------------------+
| DetNet App-Flow |
| (original IP) Packet |
+-----------------------------------+
| Segment Routing Header |
+-----------------------------------+ <--\
| IPv6 Hop-by-Hop Ex Hdr | |
| (DetNet RI Option) | DetNet Options
| (DetNet Strict/Loose Path Option) | |
+-----------------------------------+ <--/
| IPv6 Header |
+-----------------------------------+
| Data-Link |
+-----------------------------------+
| Physical |
+-----------------------------------+
Figure 7: DetNet IPv6 Option Encapsulation in SRv6 Alternative 1
In the case where the SRv6 SRH signals the exhaustive list of the
Detnet relays along the path, it is recommended to place the DetNet
Redundancy Information Option in a DOH EH before the SRH, so that it
is processed by every relay node therein without burdening the
intermediate DetNet forwarding nodes, as illustrated in Figure 8 and
Figure 9.
If all the nodes that process the loose path information are also
listed in the SRH, then the DetNet Loose Path Option may also be
placed in the DOH, as shown in Figure 8
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+-----------------------------------+
| DetNet App-Flow |
| (original IP) Packet |
+-----------------------------------+
| Segment Routing Header |
+-----------------------------------+ <--\
| IPv6 Destination Ex Hdr | |
| (DetNet RI Option) | DetNet Options
| (DetNet Loose Path Option) | |
+-----------------------------------+ <--/
| IPv6 Header |
+-----------------------------------+
| Data-Link |
+-----------------------------------+
| Physical |
+-----------------------------------+
Figure 8: DetNet IPv6 Option Encapsulation in SRv6 Alternative 2
Unless the SRH is a strict routing header indicating all the hops on
the path, the DetNet Strict Path Option must remain separate in a HbH
EH, to be observed by all routers on path, as shown in Figure 9
+-----------------------------------+
| DetNet App-Flow |
| (original IP) Packet |
+-----------------------------------+
| Segment Routing Header |
+-----------------------------------+ <--\
| IPv6 Destination Ex Hdr | |
| (DetNet RI Option) | |
+-----------------------------------+ DetNet Options
| IPv6 Hop-by-Hop Ex Hdr | |
| (DetNet Strict Path Option) | |
+-----------------------------------+ <--/
| IPv6 Header |
+-----------------------------------+
| Data-Link |
+-----------------------------------+
| Physical |
+-----------------------------------+
Figure 9: DetNet IPv6 Option Encapsulation in SRv6 Alternative 3
6. Security Considerations
7. IANA Considerations
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7.1. New Subregistry for the Redundancy Type
This specification creates a new Subregistry for the "Redundancy Type
of the Redundancy Option" under the "Internet Protocol Version 6
(IPv6) Parameters" registry [IPV6-PARMS].
* Possible values are 8-bit unsigned integers (0..255).
* Registration procedure is "IETF Review" [RFC8126].
* Initial allocation is as Suggested in Table 2:
+-----------------+--------------------------------+-----------+
| Suggested Value | Meaning | Reference |
+-----------------+--------------------------------+-----------+
| 1 | Basic Sequence Counter | THIS RFC |
+-----------------+--------------------------------+-----------+
| 2 | Zero-avoiding Sequence Counter | THIS RFC |
+-----------------+--------------------------------+-----------+
| 3 | RPL Sequence Counter | THIS RFC |
+-----------------+--------------------------------+-----------+
| 11 | Fractional NTP time stamp | THIS RFC |
+-----------------+--------------------------------+-----------+
| 12 | Short NTP time stamp | THIS RFC |
+-----------------+--------------------------------+-----------+
| 13 | PTP time stamp | THIS RFC |
+-----------------+--------------------------------+-----------+
| 14 | Short PTP time stamp | THIS RFC |
+-----------------+--------------------------------+-----------+
| 24 | TSN Redundancy Tag | THIS RFC |
+-----------------+--------------------------------+-----------+
Table 2: Redundancy Information Type values
7.2. New Hop-by-Hop Options
This specification updates the "Destination Options and Hop-by-Hop
Options" under the "Internet Protocol Version 6 (IPv6) Parameters"
registry [IPV6-PARMS] with the (suggested) values below:
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+------+-----+-----+-------+--------------------+-----------+
| Hexa | act | chg | rest | Description | Reference |
+------+-----+-----+-------+--------------------+-----------+
| 0x12 | 00 | 0 | 10010 | DetNet Redundancy | THIS RFC |
| | | | | Information Option | |
+------+-----+-----+-------+--------------------+-----------+
| 0x93 | 10 | 0 | 10011 | DetNet Strict Path | THIS RFC |
| | | | | Option | |
+------+-----+-----+-------+--------------------+-----------+
| 0x14 | 00 | 0 | 10100 | DetNet Loose Path | THIS RFC |
| | | | | Option | |
+------+-----+-----+-------+--------------------+-----------+
Table 3: DetNet Hop-by-Hop Options
8. Acknowledgments
TBD
9. References
9.1. Normative References
[RPL] Winter, T., Ed., Thubert, P., Ed., Brandt, A., Hui, J.,
Kelsey, R., Levis, P., Pister, K., Struik, R., Vasseur,
JP., and R. Alexander, "RPL: IPv6 Routing Protocol for
Low-Power and Lossy Networks", RFC 6550,
DOI 10.17487/RFC6550, March 2012,
<https://www.rfc-editor.org/info/rfc6550>.
[RFC6553] Hui, J. and JP. Vasseur, "The Routing Protocol for Low-
Power and Lossy Networks (RPL) Option for Carrying RPL
Information in Data-Plane Datagrams", RFC 6553,
DOI 10.17487/RFC6553, March 2012,
<https://www.rfc-editor.org/info/rfc6553>.
[IPv6] Deering, S. and R. Hinden, "Internet Protocol, Version 6
(IPv6) Specification", STD 86, RFC 8200,
DOI 10.17487/RFC8200, July 2017,
<https://www.rfc-editor.org/info/rfc8200>.
[RFC8126] Cotton, M., Leiba, B., and T. Narten, "Guidelines for
Writing an IANA Considerations Section in RFCs", BCP 26,
RFC 8126, DOI 10.17487/RFC8126, June 2017,
<https://www.rfc-editor.org/info/rfc8126>.
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[RFC8877] Mizrahi, T., Fabini, J., and A. Morton, "Guidelines for
Defining Packet Timestamps", RFC 8877,
DOI 10.17487/RFC8877, September 2020,
<https://www.rfc-editor.org/info/rfc8877>.
[HbH-UPDT] Hinden, R. M. and G. Fairhurst, "IPv6 Hop-by-Hop Options
Processing Procedures", Work in Progress, Internet-Draft,
draft-hinden-6man-hbh-processing-01, 2 June 2021,
<https://datatracker.ietf.org/doc/html/draft-hinden-6man-
hbh-processing-01>.
[DetNet-ARCH]
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>.
[RFC9008] Robles, M.I., Richardson, M., and P. Thubert, "Using RPI
Option Type, Routing Header for Source Routes, and IPv6-
in-IPv6 Encapsulation in the RPL Data Plane", RFC 9008,
DOI 10.17487/RFC9008, April 2021,
<https://www.rfc-editor.org/info/rfc9008>.
[6TiSCH-ARCH]
Thubert, P., Ed., "An Architecture for IPv6 over the Time-
Slotted Channel Hopping Mode of IEEE 802.15.4 (6TiSCH)",
RFC 9030, DOI 10.17487/RFC9030, May 2021,
<https://www.rfc-editor.org/info/rfc9030>.
[RAW-ARCH] Thubert, P., Papadopoulos, G. Z., and L. Berger, "Reliable
and Available Wireless Architecture/Framework", Work in
Progress, Internet-Draft, draft-pthubert-raw-architecture-
09, 7 July 2021, <https://datatracker.ietf.org/doc/html/
draft-pthubert-raw-architecture-09>.
9.2. Informative References
[I-D.varga-detnet-ip-preof]
Varga, B., Farkas, J., and A. G. Malis, "Deterministic
Networking (DetNet): DetNet PREOF via MPLS over UDP/IP",
Work in Progress, Internet-Draft, draft-varga-detnet-ip-
preof-02, 1 February 2022,
<https://datatracker.ietf.org/doc/html/draft-varga-detnet-
ip-preof-02>.
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[RPL-PDAO] Thubert, P. and R. A. Jadhav, "Root initiated routing
state in RPL", Work in Progress, Internet-Draft, draft-
ietf-roll-dao-projection-23, 13 January 2022,
<https://datatracker.ietf.org/doc/html/draft-ietf-roll-
dao-projection-23>.
[RFC3272] Awduche, D., Chiu, A., Elwalid, A., Widjaja, I., and X.
Xiao, "Overview and Principles of Internet Traffic
Engineering", RFC 3272, DOI 10.17487/RFC3272, May 2002,
<https://www.rfc-editor.org/info/rfc3272>.
[RFC6291] Andersson, L., van Helvoort, H., Bonica, R., Romascanu,
D., and S. Mansfield, "Guidelines for the Use of the "OAM"
Acronym in the IETF", BCP 161, RFC 6291,
DOI 10.17487/RFC6291, June 2011,
<https://www.rfc-editor.org/info/rfc6291>.
[RFC5905] Mills, D., Martin, J., Ed., Burbank, J., and W. Kasch,
"Network Time Protocol Version 4: Protocol and Algorithms
Specification", RFC 5905, DOI 10.17487/RFC5905, June 2010,
<https://www.rfc-editor.org/info/rfc5905>.
[RFC8402] Filsfils, C., Ed., Previdi, S., Ed., Ginsberg, L.,
Decraene, B., Litkowski, S., and R. Shakir, "Segment
Routing Architecture", RFC 8402, DOI 10.17487/RFC8402,
July 2018, <https://www.rfc-editor.org/info/rfc8402>.
[DetNet-PBST]
Finn, N. and P. Thubert, "Deterministic Networking Problem
Statement", RFC 8557, DOI 10.17487/RFC8557, May 2019,
<https://www.rfc-editor.org/info/rfc8557>.
[RFC8754] Filsfils, C., Ed., Dukes, D., Ed., Previdi, S., Leddy, J.,
Matsushima, S., and D. Voyer, "IPv6 Segment Routing Header
(SRH)", RFC 8754, DOI 10.17487/RFC8754, March 2020,
<https://www.rfc-editor.org/info/rfc8754>.
[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>.
[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>.
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[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>.
[RFC9025] Varga, B., Ed., Farkas, J., Berger, L., Malis, A., and S.
Bryant, "Deterministic Networking (DetNet) Data Plane:
MPLS over UDP/IP", RFC 9025, DOI 10.17487/RFC9025, April
2021, <https://www.rfc-editor.org/info/rfc9025>.
[IEEE Std. 802.15.4]
IEEE standard for Information Technology, "IEEE Std.
802.15.4, Part. 15.4: Wireless Medium Access Control (MAC)
and Physical Layer (PHY) Specifications for Low-Rate
Wireless Personal Area Networks".
[IEEE 802.1 TSN]
IEEE 802.1, "Time-Sensitive Networking (TSN) Task Group",
<http://www.ieee802.org/1/pages/tsn.html>.
[IEEE Std. 1588]
IEEE, "IEEE Standard for a Precision Clock Synchronization
Protocol for Networked Measurement and Control Systems",
IEEE Standard 1588,
<https://ieeexplore.ieee.org/document/4579760/>.
[IPV6-PARMS]
IANA, "Internet Protocol Version 6 (IPv6) Parameters",
<https://www.iana.org/assignments/ipv6-parameters/
ipv6-parameters.xhtml>.
Authors' Addresses
Pascal Thubert (editor)
Cisco Systems, Inc
France
Phone: +33 497 23 26 34
Email: pthubert@cisco.com
Fan Yang
Huawei Technologies
China
Email: shirley.yangfan@huawei.com
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