wdiff rfc8557.original rfc8557.txt

DetNet
Internet Engineering Task Force (IETF) N. Finn
Internet-Draft
Request for Comments: 8557 Huawei Technologies Co. Ltd
Intended status:
Category: Informational P. Thubert
Expires: June 21, 2019
ISSN: 2070-1721 Cisco
December 18, 2018
May 2019

Deterministic Networking Problem Statement
draft-ietf-detnet-problem-statement-09

Abstract

This paper documents the needs in various industries to establish
multi-hop paths for characterized flows with deterministic
properties.

Status of This Memo

This Internet-Draft document is submitted in full conformance with the
provisions of BCP 78 and BCP 79.

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This Internet-Draft will expire on June 21, 2019.
https://www.rfc-editor.org/info/rfc8557.

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Table of Contents

1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 ....................................................2
2. On Deterministic Networking . . . . . . . . . . . . . . . . . 3 .....................................4
3. Problem Statement . . . . . . . . . . . . . . . . . . . . . . 6 ...............................................6
3.1. Supported topologies . . . . . . . . . . . . . . . . . . 6 Topologies .......................................6
3.2. Flow Characterization . . . . . . . . . . . . . . . . . . 6 ......................................6
3.3. Centralized Path Computation and Installation . . . . . . 6 ..............7
3.4. Distributed Path Setup . . . . . . . . . . . . . . . . . 7 .....................................8
3.5. Duplicated data format . . . . . . . . . . . . . . . . . 8 Data Format .....................................8
4. Security Considerations . . . . . . . . . . . . . . . . . . . 8 .........................................9
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9 .............................................9
6. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 9
7. Informative References . . . . . . . . . . . . . . . . . . . 9 .........................................10
Acknowledgments ...................................................11
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 10 ................................................11

1. Introduction

The Deterministic

"Deterministic Networking Use Cases [I-D.ietf-detnet-use-cases]
document Cases" [RFC8578] illustrates that
beyond the classical case of industrial
automation Industrial Automation and control systems (IACS), Control
Systems (IACSs) there are in fact multiple industries with strong strong,
and yet relatively similar similar, needs for deterministic network services with
latency guarantees and ultra-low packet loss.

The generalization of the needs for more deterministic networks have has
led to the IEEE 802.1 AVB Audio Video Bridging (AVB) Task Group becoming
the Time-Sensitive Networking (TSN) [IEEE802.1TSNTG] [IEEE-802.1TSNTG] Task Group
(TG), with a much-
expanded much-expanded constituency from the industrial and
vehicular markets.

Along with this expansion, the networks in consideration considered here are becoming
larger and structured, requiring deterministic forwarding beyond the
LAN boundaries. For instance, an IACS segregates the network along
the broad lines of the Purdue Enterprise Reference Architecture
(PERA) [ISA95], typically using deterministic local area networks LANs for Purdue level 2
control systems, whereas public infrastructures such as Electricity
Automation electricity
automation require deterministic properties over the Wide Area. The
realization is now coming wide area.
Implementers have come to realize that the convergence of IT and Operational
Operation Technology (OT) networks requires Layer-3, Layer 3, as well as Layer-2,
Layer 2, capabilities.

While the initial user base has focused almost entirely on Ethernet
physical media and Ethernet-based bridging protocol protocols from several
Standards Development Organizations, Organizations (SDOs), the need for Layer-3 Layer 3, as
expressed above, must not be confined to Ethernet and Ethernet-like
media. While such media must be encompassed by any useful
Deterministic Networking (DetNet) Architecture, architecture, cooperation between
the IETF and other SDOs must not be limited to the IEEE or the
IEEE 802. 802 organizations. Furthermore, while the
work both completed and
ongoing work in other SDOs, and in IEEE 802 in particular, provide provides
an obvious starting point for a DetNet architecture, we must not
assume that these other SDOs' work confines the space in which the
DetNet architecture progresses.

The properties of deterministic networks will have specific
requirements for the use of routed networks to support these
applications
applications, and a new model must be proposed to integrate this
determinism in IT technology. implementations. The proposed model should enable
a fully scheduled operation orchestrated by a central controller, controller and
may support a more distributed operation with probably lesser (probably lesser)
capabilities. In At any fashion, rate, the model should not compromise the
ability of a network to keep carrying the sorts of traffic that is
already carried today in conjunction with new, more deterministic
flows. Forward note: The DetNet Architecture
[I-D.ietf-detnet-architecture] is the document Note: "Deterministic Networking Architecture" [DetNet-Arch]
was produced by the DetNet
WG Working Group to describe that model.

At the time of this writing, the expectation it is expected that

o once the abstract model is agreed upon, the IETF will specify
(1) the signaling elements to be used to establish a path and
(2) the tagging elements to be used to identify the flows that are
to be forwarded along that path.
The expectation is also that path

o the IETF will specify the necessary
protocols, protocols or protocol
additions, based on relevant IETF technologies, to implement the
selected model. model

A desirable outcome of the work is the capability ability to establish a
multi-hop path over the IP or MPLS network, network for a particular flow with
given timing and precise throughput requirements, requirements and to carry this
particular flow along the multi-hop path with such characteristics as
low latency and ultra-low jitter, reordering and/or replication and
elimination of packets over non-congruent paths for a higher delivery
ratio, and/or zero congestion loss, regardless of the amount of other
flows in the network.

Depending on the network capabilities and on the current state, requests
to establish a path by an end-node end node or a network management entity may
be granted or rejected, an existing path may be moved or removed, and
DetNet flows exceeding their contract may face packet
declassification and drop.

2. On Deterministic Networking

The Internet is not the only digital network that has grown
dramatically over the last 30-40 years. Video and audio
entertainment, and as well as control systems for machinery,
manufacturing processes, and vehicles vehicles, are also ubiquitous, ubiquitous and are
now based almost entirely on digital technologies. Over the past
10 years, engineers in these fields have come to realize that
significant advantages in both cost and in the ability to accelerate
growth can be obtained by basing all of these disparate digital
technologies on packet networks.

The goals of Deterministic Networking are to (1) enable the migration
of applications with critical timing and reliability issues that
currently use special-purpose fieldbus technologies (HDMI, CANbus,
ProfiBus, etc... (High-Definition
Multimedia Interface (HDMI), Controller Area Network (CAN bus),
PROFIBUS [PROFIBUS], etc. ... even RS-232!) to packet technologies in general,
general and
the Internet Protocol to IP in particular, particular and to (2) support both these new
applications,
applications and existing packet network applications, applications over the same
physical network. In other words, a Deterministic Network deterministic network is
backwards compatible with (capable of transporting) statistically
multiplexed traffic while preserving the properties of the accepted
deterministic flows.

The Deterministic Networking Use Cases [I-D.ietf-detnet-use-cases]
document

[RFC8578] indicates that applications in multiple fields need some or
all of a suite of features that includes:

1. Time synchronization of all host and network nodes (routers and/
or
and/or bridges), accurate to something between 10 nanoseconds and
10 microseconds, depending on the application.

2. Support for Deterministic deterministic packet flows that:

* Can be unicast or multicast; multicast.

* Need absolute guarantees of minimum and maximum latency end-
to-end
end to end across the network; sometimes a tight jitter is
required as well; well.

* Need a packet loss ratio beyond the classical range for a
particular medium, in the range of 10^-9 to 10^-12, 10^-12 or better, better
on Ethernet, Ethernet and in on the order of 10^-5 in Wireless Sensor Mesh
Networks; wireless sensor mesh
networks.

* Can, in total, absorb more than half of the network's
available bandwidth (that is, massive over-provisioning is
ruled out as a solution); solution).

* Cannot suffer throttling, congestion feedback, or any other
network-imposed transmission delay, although the flows can be
meaningfully characterized either by either (1) a fixed, repeating
transmission schedule, schedule or by (2) a maximum bandwidth and packet
size;
size.

3. Multiple methods to schedule, shape, limit, for scheduling, shaping, limiting, and otherwise control
controlling the transmission of critical packets at each hop
through the network data plane; plane.

4. Robust defenses against misbehaving hosts, routers, or bridges,
both
in both the data plane and the control planes, plane, with guarantees
that a critical flow within its guaranteed resources cannot be
affected by other flows flows, whatever the pressures on the network - network.
For more on the specific threats against DetNet in the DetNet DetNet, see
"Deterministic Networking (DetNet) Security
Considerations [I-D.ietf-detnet-security] document; Considerations"
[DetNet-Security].

5. One or more methods to reserve for reserving resources in bridges and
routers to carry these flows.

Time synchronization

Time-synchronization techniques need not be addressed by an IETF
Working Group;
working group; there are a number of standards available for this
purpose, including IEEE 1588, 1588 [IEEE-1588], IEEE 802.1AS, 802.1AS [IEEE-8021AS],
and more.

The needs related to multicast, latency, loss ratio, and non-throttling needs are made
necessary by throttling
avoidance exist because the algorithms employed by the applications. applications
demand it. They are not simply the transliteration of fieldbus needs
to a packet-based fieldbus simulation, but simulation; they also reflect fundamental
mathematics of the control of a physical system.

With classical forwarding latency- of latency-sensitive and loss-sensitive
packets across a network, interactions among different critical flows
introduce fundamental uncertainties in delivery schedules. The
details of the queuing, shaping, and scheduling algorithms employed
by each bridge or router to control the output sequence on a given
port affect the detailed makeup of the output stream, e.g. e.g., how
finely a given flow's packets are mixed among those of other flows.

This, in turn, has a strong effect on the buffer requirements, and
hence the latency guarantees deliverable, by the next bridge or
router along the path. For this reason, the IEEE 802.1 Time-
Sensitive Networking Task Group TSN TG has
defined a new set of queuing, shaping, and scheduling algorithms that
enable each bridge or router to compute the exact number of buffers
to be allocated for each flow or class of flows.

Robustness is a common

Networking protocols commonly need for networking protocols, but robustness. Note that robustness
plays a
more particularly important part in real-time control networks,
where expensive equipment, and even lives, can be lost due to
misbehaving equipment.

Reserving resources before packet transmission is the one fundamental
shift in the behavior of network applications that is impossible to
avoid. In the first place, a network cannot deliver finite latency
and practically zero packet loss to an arbitrarily high offered load.
Secondly, achieving practically zero packet loss for un-throttled unthrottled
(though bandwidth limited) bandwidth-limited) flows means that bridges and routers have
to dedicate buffer resources to specific flows or to classes of flows.
The requirements of each reservation have to be translated into the
parameters that control each host's, bridge's, and router's queuing,
shaping, and scheduling functions and delivered to the hosts,
bridges, and routers.

3. Problem Statement

3.1. Supported topologies Topologies

In some use cases, the end point which run that runs the application is
involved in the deterministic networking operation, Deterministic Networking operation -- for instance instance,
by controlling certain aspects of its throughput throughput, such as rate or
precise time of emission. In that such a case, the deterministic path is end-to-end
end to end from application host to application host.

On the other end, the deterministic portion of a path may be a tunnel
between an ingress point and an egress router. In any case, routers
and switches in between should not need to be aware of whether the
path is
end-to-end end to end or a tunnel.

While it is clear that DetNet does not aim at setting to set up deterministic
paths over the global Internet, there is still a lack of clarity on
regarding the limits of a domain where a deterministic path can be
set up. These limits may depend in on the technology that is used to
set the path up, whether it is centralized or distributed.

3.2. Flow Characterization

Deterministic forwarding can only apply on to flows with such
well-defined characteristics such as periodicity and burstiness. Before a
path can be established to serve them, the expression of those
characteristics, and how the network can serve them, for instance them (for instance, in
shaping and forwarding operations, operations), must be specified.

3.3. Centralized Path Computation and Installation

A centralized routing model, such as that provided with a Path
Computation Element (PCE) (see [RFC4655]), enables global and
per-flow optimizations. The This type of model is attractive attractive, but a
number of issues are
left remain to be solved. In solved -- in particular:

o whether and how the path computation can be installed by 1)

* an end device or 2)

* a Network Management entity,
o network management entity

and

o how the path is set up, up -- either

* by installing state at each hop with a direct interaction
between the forwarding device and the
PCE, PCE or

* along a path by injecting a source-routed request at one end of
the path path, following classical Traffic Engineering (TE)
models. models

To enable a centralized model, DetNet should produce a description of
the high level high-level interaction and data models to:

o report the topology and device capabilities to the central
controller;
controller

o establish a direct interface between the centralized PCE to and each
device under its control in order to enable a vertical signaling

o request a path setup for a new flow with particular
characteristics over the service interface and control it through
its life cycle; cycle

o provide support for life cycle life-cycle management for a path
(instantiate/modify/update/delete)

o provide support for adaptability to cope with such various events such
as loss of a link, etc... link

o expose the status of the path to the end devices (UNI interface) (User-Network
Interfaces (UNIs))
o provide additional reliability through redundancy, in particular particularly
with packet Packet Replication, Elimination Elimination, and Ordering Functions
(PREOF)
(PREOF), where the former redundant paths may generate an out-of-order delivery
that deliver packets out of order
and PREOF may need to be corrected corrected by correct the latter; ordering

o indicate the flows and packet sequences in-band with the flows,
this flows.
This is needed for flows that require PREOF in order to isolate
duplicates and reorder in packets at the end; end of the sequence

3.4. Distributed Path Setup

Whether a distributed alternative without a PCE can be valuable could
be studied as well. Such an alternative could could, for instance inherit
from the instance, build
upon Resource ReSerVation Reservation Protocol [RFC3209] - TE (RSVP-TE) flows. flows [RFC3209].
But the focus of the work should be to deliver the centralized
approach first.

To enable a RSVP-TE like functionality, functionality similar to that of RSVP-TE, the following
steps would take place:

1. Neighbors and their capabilities are would be discovered and exposed
to compute a path that fits would fit the DetNet constraints, constraints --
typically those of latency, time precision precision, and resource
availability.

2. A constrained path is would be calculated with an improved version
of Constrained Shortest Path First (CSPF) that is aware of
DetNet.

3. The path may be installed using a control protocol such as RSVP-
TE, associated with
RSVP-TE, extended to enable flow identification, identification and install new
per-hop behavior such as Packet Replication and Replication, Elimination, and blocked resources.
Ordering, and to reserve physical resources for the flow. In
that case, traffic flows can could be transported through an MPLS-TE
tunnel, using the reserved resources for this flow at each hop.

3.5. Duplicated data format Data Format

In some cases cases, the duplication and elimination of packets over non-
congruent
non-congruent paths is are required to achieve a sufficiently high
delivery ratio to meet application needs. In these cases, a small
number of packet formats and supporting protocols are required (preferably,
(preferably just one) one of each) to serialize the packets of a DetNet
stream at one point in the network, replicate them at one or more
points in the network, and discard duplicates at one or more other
points in the network, including perhaps the destination host. Using
an existing solution would be preferable to inventing a new one.

4. Security Considerations

Security in the context of Deterministic Networking has an added
dimension; the time of delivery of a packet can be just as important
as the contents of the packet, packet itself. A man-in-the-middle attack,
for example, can impose, impose and then systematically adjust, adjust additional
delays into a link, and thus disrupt or subvert a real-time
application without having to crack any encryption methods employed.
See [RFC7384] for an exploration of this issue in a related context.

Typical control networks today rely on complete physical isolation to
prevent rogue access to network resources. DetNet enables the
virtualization of those networks over a converged IT/OT
infrastructure. Doing so, DetNet introduces an additional risk that of
flows interact interacting and interfere interfering with one another as they share
physical resources such as Ethernet trunks and the radio spectrum.
The requirement is that there is no possible data leak from and into
a deterministic flow, and in a flow. Stated more general fashion generally, there is no possible
influence whatsoever from the outside on a deterministic flow. The
expectation is that physical resources are effectively associated
with a given flow at a given point of in time. In that model, Time Sharing the
time-sharing of physical resources becomes transparent to the
individual flows, as these flows which have no clue regarding whether or
not the resources are used by other flows at other times.

The overall security of a deterministic system must cover:

o the protection of the signaling protocol

o the authentication and authorization of the controlling nodes nodes,
including plug-and-play participating end systems. systems

o the identification and shaping of the flows

o the isolation of flows from leakage and other influences from any
activity sharing physical resources. resources

The specific threats against DetNet are further discussed in the
DetNet Security Considerations [I-D.ietf-detnet-security] document.
[DetNet-Security].

5. IANA Considerations

This document does not require an action from IANA. has no IANA actions.

6. Acknowledgments

The authors wish to thank Lou Berger, Pat Thaler, Jouni Korhonen,
Janos Farkas, Stewart Bryant, Andrew Malis, Ethan Grossman, Patrick
Wetterwald, Subha Dhesikan, Matthew Miller, Erik Nordmark, George
Swallow, Rodney Cummings, Ines Robles, Shwetha Bhandari, Rudy Klecka,
Anca Zamfir, David Black, Thomas Watteyne, Shitanshu Shah, Kiran
Makhijani, Craig Gunther, Warren Kumari, Wilfried Steiner, Marcel
Kiessling, Karl Weber, Alissa Cooper, and Benjamin Kaduk for their
various contributions to this work.

7. Informative References

[I-D.ietf-detnet-architecture]

[DetNet-Arch]
Finn, N., Thubert, P., Varga, B., and J. Farkas,
"Deterministic Networking Architecture", draft-ietf-
detnet-architecture-09 (work Work in progress), October 2018.

[I-D.ietf-detnet-security]
Progress, draft-ietf-detnet-architecture-13, May 2019.

[DetNet-Security]
Mizrahi, T., Grossman, E., Ed., Hacker, A., Das, S.,
Dowdell, J., Austad, H., Stanton, K., and N. Finn,
"Deterministic Networking (DetNet) Security
Considerations", draft-ietf-
detnet-security-03 (work Work in progress), October 2018.

[I-D.ietf-detnet-use-cases]
Grossman, E., "Deterministic Networking Use Cases", draft-
ietf-detnet-use-cases-19 (work in progress), October 2018.

[IEEE802.1TSNTG] Progress,
draft-ietf-detnet-security-04, March 2019.

[IEEE-1588]
IEEE, "IEEE Standard for a Precision Clock Synchronization
Protocol for Networked Measurement and Control Systems",
IEEE Standard 1588-2008, <https://standards.ieee.org/
findstds/standard/1588-2008.html>.

[IEEE-802.1TSNTG]
IEEE Standards Association, "IEEE 802.1 Time-Sensitive
Networks
Networking Task Group", 2013,
<http://www.ieee802.org/1/pages/avbridges.html>.

[IEEE-8021AS]
IEEE, "IEEE Standard for Local and Metropolitan Area
Networks - Timing and Synchronization for Time-Sensitive
Applications in Bridged Local Area Networks",
IEEE 802.1AS-2011,
<http://www.ieee802.org/1/pages/802.1as.html>.

[ISA95] ANSI/ISA, "Enterprise-Control System Integration - Part 1:
Models and Terminology", 2000, <https://www.isa.org/isa95/>.

[PROFIBUS]
IEC, "PROFIBUS Standard - DP Specification (IEC 61158
Type 3)", <https://www.profibus.com/>.

[RFC3209] Awduche, D., Berger, L., Gan, D., Li, T., Srinivasan, V.,
and G. Swallow, "RSVP-TE: Extensions to RSVP for LSP
Tunnels", RFC 3209, DOI 10.17487/RFC3209, December 2001,
<https://www.rfc-editor.org/info/rfc3209>.

[RFC4655] Farrel, A., Vasseur, J., 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>.

[RFC7384] Mizrahi, T., "Security Requirements of Time Protocols in
Packet Switched Networks", RFC 7384, DOI 10.17487/RFC7384,
October 2014, <https://www.rfc-editor.org/info/rfc7384>.

[RFC8578] Grossman, E., Ed., "Deterministic Networking Use Cases",
RFC 8578, DOI 10.17487/RFC8578, May 2019,
<https://www.rfc-editor.org/info/rfc8578>.

Acknowledgments

Authors' Addresses

Norman Finn
Huawei Technologies Co. Ltd
3755 Avocado Blvd.
PMB 436
La Mesa, California 91941
US
United States of America

Phone: +1 925 980 6430
Email: norman.finn@mail01.huawei.com

Pascal Thubert
Cisco Systems
Village d'Entreprises Green Side
400, Avenue de Roumanille
Batiment T3
Biot Systems, Inc.
Building D, 45 Allee des Ormes - BP1200
Mougins - Sophia Antipolis 06410
FRANCE 06254
France

Phone: +33 497 232 634 4 97 23 26 34
Email: pthubert@cisco.com