Internet DRAFT - draft-bernardos-detnet-multidomain
draft-bernardos-detnet-multidomain
DetNet CJ. Bernardos
Internet-Draft UC3M
Intended status: Informational A. Mourad
Expires: 26 January 2024 InterDigital
25 July 2023
DETNET multidomain extensions
draft-bernardos-detnet-multidomain-02
Abstract
This document addresses the multi-domain DetNet problem, analyzing
what the technical gaps are and exploring some possible solutions.
Application, control and data plane aspects are in scope. The goal
is to help understanding what might be the next steps towards
enabling DetNet in multi technology and/or administrative domains.
Status of This Memo
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This Internet-Draft will expire on 26 January 2024.
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Table of Contents
1. Introduction and Problem Statement . . . . . . . . . . . . . 2
2. Application plane . . . . . . . . . . . . . . . . . . . . . . 5
3. Controller plane . . . . . . . . . . . . . . . . . . . . . . 5
4. Network/Data plane . . . . . . . . . . . . . . . . . . . . . 7
5. Requirements . . . . . . . . . . . . . . . . . . . . . . . . 7
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7
7. Security Considerations . . . . . . . . . . . . . . . . . . . 7
8. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 8
9. Informative References . . . . . . . . . . . . . . . . . . . 8
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 9
1. Introduction and Problem Statement
The Deterministic Networking (DetNet) Working Group focuses on
deterministic data paths that operate over Layer 2 bridged and Layer
3 routed segments, where such paths can provide bounds on latency,
loss, and packet delay variation (jitter), and high reliability.
The DetNet architecture document [RFC8655] includes the concept of
multi-domain in the DetNet Service reference model (Fig. 5 of
[RFC8655], reproduced here in Figure 1 for convenience. However, the
WG has not yet worked in detail on the necessary protocol operations
to support multi-domain at control and data plane.
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DetNet DetNet
End System End System
_ _
/ \ +----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: DetNet Service Reference Model (Multidomain) (from RFC8655)
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In adddition to the DetNet work, there is also wireless-focused
efforts being explored at the Reliable and Available Wireless (RAW)
WG. Wireless operates on a shared medium, and transmissions cannot
be fully deterministic due to uncontrolled interferences, including
self-induced multipath fading. RAW is an effort to provide
Deterministic Networking on across a path that include a wireless
interface. RAW provides for high reliability and availability for IP
connectivity over a wireless medium. The wireless medium presents
significant challenges to achieve deterministic properties such as
low packet error rate, bounded consecutive losses, and bounded
latency. RAW extends the DetNet Working Group concepts to provide
for high reliability and availability for an IP network utilizing
scheduled wireless segments and other media, e.g., frequency/time-
sharing physical media resources with stochastic traffic: IEEE Std.
802.15.4 timeslotted channel hopping (TSCH), 3GPP 5G ultra-reliable
low latency communications (URLLC), IEEE 802.11ax/be, and L-band
Digital Aeronautical Communications System (LDACS), etc. Similar to
DetNet, RAW technologies aim at staying abstract to the radio layers
underneath, addressing the Layer 3 aspects in support of applications
requiring high reliability and availability.
DetNet defines the Packet Replication, Elimination, and Ordering
Functions (PREOF) as a way to provide service protection. PREOF
involves 4 capabilities:
* Sequencing information, by adding a sequence number or time stamp
as part of DetNet. This is typically done once, at or near the
source.
* Replicating packets into multiple DetNet member flows, and
typically sending them along multiple different paths to the
destination(s).
* Eliminating duplicate packets of a DetNet flow based on the
sequencing information and a history of received packets.
* Reordering DetNet flow's packets that are received out of order.
Packet (hybrid) ARQ, Replication, Elimination and Ordering (PAREO) is
a superset of DetNet's PREOF, defined in RAW, that includes radio-
specific techniques such as short range broadcast, MUMIMO,
constructive interference and overhearing, which can be leveraged
separately or combined to increase the reliability.
There multiple scenarios and use cases that might involve multiple
technology and/or administrative domains in DetNet and RAW. For
example, there are several use cases [I-D.ietf-raw-use-cases] where
reliability and availability are key requirements for wireless
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heterogeneous networks. A couple of relevant examples are (i) the
manufacturing sector, where a plethora of devices are interconnected
and generate data that need to be reliably delivered to the control
and monitoring agents; and (ii) the residential gaming, with eXtended
Reality (XR).
Next sections explore what the main multi-domain aspects for the
application, controller and network/data planes in DetNet and RAW
are, to then identify some existing gaps that would require further
work at the IETF.
2. Application plane
As described in [RFC8655], the Application Plane incorporates the
User Agent, a specialized application that interacts with the end
user and operator and performs requests for DetNet services via an
abstract Flow Management Entity (FME), which may or may not be
collocated with (one of) the end systems. At the Application Plane,
a management interface enables the negotiation of flows between end
systems.
In a multi-domain deployment, the User Agent might be aware of the
existance of multiple domains or it might be unaware. A multi-domain
aware User Agent/application plane could take care of the negotiation
of the flows at all involved domains, whereas a multi-domain unaware
one will have to rely on the network to take care of it
transparently.
3. Controller plane
We refer to the controller plane as the aggregation of the Control
and Management planes. The term "Controller Plane Function (CPF)"
refers to any device operating in that plane, whether it is a Path
Computation Element (PCE) [RFC4655], a Network Management Entity
(NME), or a distributed control protocol. The CPF is a core element
of a controller, in charge of computing deterministic paths to be
applied in the Network Plane. A (Northbound) Service Interface
enables applications in the Application Plane to communicate with the
entities in the Controller Plane.
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In DetNet, one or more CPFs collaborate to implement the requests
from the FME as per-flow, per-hop behaviors installed in the DetNet
nodes for each individual flow. Adding multi-domain support might
require some support at the CPF. For example, CPFs sitting at
different domains need to discover themselves, authenticate and
negotiate per-hop behaviors. Depending on the multi-domain support
provided by the application plane, the controller plane might be
relieved from some reponsibilities (e.g., if the application plane is
taking care of splitting what needs to be provided by each domain).
Let's know take the case of RAW. As introduced in
[I-D.ietf-raw-architecture], RAW separates the path computation time
scale at which a complex path is recomputed from the path selection
time scale at which the forwarding decision is taken for one or a few
packets. RAW operates at the path selection time scale. The RAW
problem is to decide, amongst the redundant solutions that are
proposed by the Patch Computation Element (PCE), which one will be
used for each packet to provide a Reliable and Available service
while minimizing the waste of constrained resources. To that effect,
RAW defines the Path Selection Engine (PSE) that is the counter-part
of the PCE to perform rapid local adjustments of the forwarding
tables within the diversity that the PCE has selected for the Track.
The PSE enables to exploit the richer forwarding capabilities with
Packet (hybrid) ARQ, Replication, Elimination and Ordering (PAREO),
and scheduled transmissions at a faster time scale.
While there exist inter-PCE solutions today, allowing one domain’s
PCE to learn some inter-domain paths, this would not be sufficient,
as the PSE of one domain would not have full visibility nor
capability to act on the other domains (e.g., there are no multi-
domain OAM solutions in place yet), limiting its capability to
guarantee any given SLA. Therefore, there is a need to define inter-
PSE coordination mechanisms across domains.
There exist today standardized solutions, such as the ones in the
context of Path Computation Element (PCE), enabling computing multi-
/inter-domain paths. As an example, the Hierarchical PCE (G-PCE) was
defined in RFC 6805 [RFC6805] and is described hereafter. A parent
PCE maintains a domain topology map that contains the child domains
(seen as vertices in the topology) and their interconnections (links
in the topology). The parent PCE has no information about the
content of the child domains; that is, the parent PCE does not know
about the resource availability within the child domains, nor does it
know about the availability of connectivity across each domain
because such knowledge would violate the confidentiality requirement
and either would require flooding of full information to the parent
(scaling issue) or would necessitate some form of aggregation. The
parent PCE is used to compute a multi-domain path based on the domain
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connectivity information. A child PCE may be responsible for single
or multiple domains and is used to compute the intra-domain path
based on its own domain topology information.
Solutions like the above are not sufficient alone to solve the multi-
domain RAW problem, as the PSEs need to have some additional
information from the other involved domains to be sensitive/reactive
to transient changes, in order to ensure a certain level of
reliability and availability in a multi-domain wireless heterogeneous
mesh network. [I-D.bernardos-raw-multidomain] explores in more
detail the RAW-specific multi-domain problem and proposes some
initial solutions.
4. Network/Data plane
The Network Plane represents the network devices and protocols as a
whole, regardless of the layer at which the network devices operate.
It includes the Data Plane and Operational Plane (e.g., OAM) aspects.
A Southbound (Network) Interface enables the entities in the
Controller Plane to communicate with devices in the Network Plane.
At the Network Plane, DetNet nodes may exchange information regarding
the state of the paths, between adjacent DetNet nodes and possibly
with the end systems. In a multi-domain environment, nodes belonging
to different domains might need to exchange information. This might
require protocol translations and/or abstractions, as the different
domains might not offer the same capabilities nor use the same
network protocols. Additionally, OAM protocols
[I-D.ietf-detnet-oam-framework] might also need to be extended to
support multi-domain operation.
Note as well, that performing PREOF or PAREO across multiple domains
poses additional challenges, as knowledge of all the involved domains
might not be available and/or the data planes at each domain could
also be different.
5. Requirements
TBD.
6. IANA Considerations
TBD.
7. Security Considerations
TBD.
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8. Acknowledgments
This work has been partially supported by the Spanish Ministry of
Economic Affairs and Digital Transformation and the European Union-
NextGenerationEU through the UNICO 5G I+D 6G-DATADRIVEN. This work
has also been partially funded by the European Commission Horizon
Europe SNS JU PREDICT-6G (GA 101095890) Project.
9. Informative References
[I-D.bernardos-raw-multidomain]
Bernardos, C. J. and A. Mourad, "RAW multidomain
extensions", Work in Progress, Internet-Draft, draft-
bernardos-raw-multidomain-02, 13 March 2023,
<https://datatracker.ietf.org/doc/html/draft-bernardos-
raw-multidomain-02>.
[I-D.ietf-detnet-oam-framework]
Mirsky, G., Theoleyre, F., Papadopoulos, G. Z., Bernardos,
C. J., Varga, B., and J. Farkas, "Framework of Operations,
Administration and Maintenance (OAM) for Deterministic
Networking (DetNet)", Work in Progress, Internet-Draft,
draft-ietf-detnet-oam-framework-08, 1 February 2023,
<https://datatracker.ietf.org/doc/html/draft-ietf-detnet-
oam-framework-08>.
[I-D.ietf-raw-architecture]
Thubert, P., "Reliable and Available Wireless
Architecture", Work in Progress, Internet-Draft, draft-
ietf-raw-architecture-13, 10 July 2023,
<https://datatracker.ietf.org/doc/html/draft-ietf-raw-
architecture-13>.
[I-D.ietf-raw-use-cases]
Bernardos, C. J., Papadopoulos, G. Z., Thubert, P., and F.
Theoleyre, "RAW Use-Cases", Work in Progress, Internet-
Draft, draft-ietf-raw-use-cases-11, 17 April 2023,
<https://datatracker.ietf.org/doc/html/draft-ietf-raw-use-
cases-11>.
[RFC4655] Farrel, A., Vasseur, J.-P., and J. Ash, "A Path
Computation Element (PCE)-Based Architecture", RFC 4655,
DOI 10.17487/RFC4655, August 2006,
<https://www.rfc-editor.org/info/rfc4655>.
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[RFC6805] King, D., Ed. and A. Farrel, Ed., "The Application of the
Path Computation Element Architecture to the Determination
of a Sequence of Domains in MPLS and GMPLS", RFC 6805,
DOI 10.17487/RFC6805, November 2012,
<https://www.rfc-editor.org/info/rfc6805>.
[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>.
Authors' Addresses
Carlos J. Bernardos
Universidad Carlos III de Madrid
Av. Universidad, 30
28911 Leganes, Madrid
Spain
Phone: +34 91624 6236
Email: cjbc@it.uc3m.es
URI: http://www.it.uc3m.es/cjbc/
Alain Mourad
InterDigital Europe
Email: Alain.Mourad@InterDigital.com
URI: http://www.InterDigital.com/
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