Internet DRAFT - draft-finn-detnet-architecture
draft-finn-detnet-architecture
DetNet N. Finn
Internet-Draft P. Thubert
Intended status: Standards Track Cisco
Expires: September 22, 2016 M. Johas Teener
Broadcom
March 21, 2016
Deterministic Networking Architecture
draft-finn-detnet-architecture-04
Abstract
Deterministic Networking (DetNet) provides a capability to carry
specified unicast or multicast data flows for real-time applications
with extremely low data loss rates and bounded latency. Techniques
used include: 1) reserving data plane resources for individual (or
aggregated) DetNet flows in some or all of the relay systems (bridges
or routers) along the path of the flow; 2) providing fixed paths for
DetNet flows that do not rapidly change with the network topology;
and 3) sequentializing, replicating, and eliminating duplicate
packets at various points to ensure the availability of at least one
path. The capabilities can be managed by configuration, or by manual
or automatic network management.
Status of This Memo
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Copyright Notice
Copyright (c) 2016 IETF Trust and the persons identified as the
document authors. All rights reserved.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4
2.1. Terms used in this document . . . . . . . . . . . . . . . 4
2.2. IEEE 802 TSN to DetNet dictionary . . . . . . . . . . . . 5
3. Providing the DetNet Quality of Service . . . . . . . . . . . 5
3.1. Zero Congestion Loss . . . . . . . . . . . . . . . . . . 7
3.2. Pinned paths . . . . . . . . . . . . . . . . . . . . . . 8
3.3. Packet replication and deletion . . . . . . . . . . . . . 8
4. DetNet Architecture . . . . . . . . . . . . . . . . . . . . . 9
4.1. Elements of DetNet Architecture . . . . . . . . . . . . . 9
4.2. Traffic Engineering for DetNet . . . . . . . . . . . . . 11
4.2.1. The Application Plane . . . . . . . . . . . . . . . . 13
4.2.2. The Controller Plane . . . . . . . . . . . . . . . . 13
4.2.3. The Network Plane . . . . . . . . . . . . . . . . . . 14
4.3. DetNet flows . . . . . . . . . . . . . . . . . . . . . . 15
4.3.1. Source guarantees . . . . . . . . . . . . . . . . . . 15
4.3.2. Incomplete Networks . . . . . . . . . . . . . . . . . 16
4.4. Queuing, Shaping, Scheduling, and Preemption . . . . . . 16
4.5. Coexistence with normal traffic . . . . . . . . . . . . . 17
4.6. Fault Mitigation . . . . . . . . . . . . . . . . . . . . 18
4.7. Protocol Stack Model . . . . . . . . . . . . . . . . . . 18
4.8. Advertising resources, capabilities and adjacencies . . . 20
4.9. Provisioning model . . . . . . . . . . . . . . . . . . . 20
4.9.1. Centralized Path Computation and Installation . . . . 20
4.9.2. Distributed Path Setup . . . . . . . . . . . . . . . 21
4.10. Scaling to larger networks . . . . . . . . . . . . . . . 21
4.11. Connected islands vs. networks . . . . . . . . . . . . . 21
5. Compatibility with Layer-2 . . . . . . . . . . . . . . . . . 22
6. Open Questions . . . . . . . . . . . . . . . . . . . . . . . 22
6.1. Data plane shapers and schedulers . . . . . . . . . . . . 22
6.2. DetNet flow identification and sequencing . . . . . . . . 22
6.3. Flat vs. hierarchical control . . . . . . . . . . . . . . 23
6.4. Peer-to-peer reservation protocol . . . . . . . . . . . . 23
6.5. Wireless media interactions . . . . . . . . . . . . . . . 24
7. Security Considerations . . . . . . . . . . . . . . . . . . . 24
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 25
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9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 25
10. Access to IEEE 802.1 documents . . . . . . . . . . . . . . . 25
11. Informative References . . . . . . . . . . . . . . . . . . . 25
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 29
1. Introduction
Deterministic Networking (DetNet) is a service that can be offered by
a network to data flows (DetNet flows) that that are limited, at
their source, to a maximum data rate specified by that source.
DetNet provides these flows extremely low packet loss rates and
assured maximum end-to-end delivery latency. This is accomplished by
dedicating network resources such as link bandwidth and buffer space
to DetNet flows and/or classes of DetNet flows. Unused reserved
resources are available to non-DetNet packets.
The Deterministic Networking Problem Statement
[I-D.finn-detnet-problem-statement] introduces Deterministic
Networking, and Deterministic Networking Use Cases
[I-D.ietf-detnet-use-cases] summarizes the need for it.
A goal of DetNet is a converged network in all respects. That is,
the presence of DetNet flows does not preclude non-DetNet flows, and
the benefits offered DetNet flows should not, except in extreme
cases, prevent existing QoS mechanisms from operating in a normal
fashion, subject to the bandwidth required for the DetNet flows. A
single source-destination pair can trade both DetNet and non-DetNet
flows. End systems and applications need not instantiate special
interfaces for DetNet flows. Networks are not restricted to certain
topologies; connectivity is not restricted. Any application that
generates a data flow that can be usefully characterized as having a
maximum bandwidth should be able to take advantage of DetNet, as long
as the necessary resources can be reserved. Reservations can be made
by the application itself, via network management, by an applications
controller, or by other means.
Many applications of interest to Deterministic Networking require the
ability to synchronize the clocks in end systems to a sub-microsecond
accuracy. Some of the queue control techniques defined in
Section 4.4 also require time synchronization among relay systems.
The means used to achieve time synchronization are not addressed in
this document.
The present document is an individual contribution, intended by the
authors for eventual adoption by the DetNet working group. As such,
it expresses the only the opinions of the authors.
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2. Terminology
2.1. Terms used in this document
The following special terms are used in this document in order to
avoid the assumption that a given element in the architecture does or
does not have Internet Protocol stack, functions as a router, bridge,
firewall, or otherwise plays a particular role at Layer-2 or higher.
destination
An end system capable of sinking a DetNet flow.
DetNet domain
The portion of a network that is DetNet aware. It includes
end systems and other DetNet nodes.
DetNet flow
A DetNet flow is a sequence of packets from a single source,
through some number of relay systems to one or more
destinations, that is limited by the source in its maximum
packet size and transmission rate, and can thus be ensured
the DetNet Quality of Service (QoS) from the network.
DetNet node
A DetNet aware end system or relay system. "DetNet" may be
omitted in some text.
end system
Commonly called a "host" or "node" in IETF documents, and an
"end station" is IEEE 802 documents. End systems of interest
to this document are either sources or destinations of L2
and/or L3 DatNet streams. Note that a system that takes non-
DetNet aware traffic and transmits it via a DetNet flow is
also an end system. (For comparison, a Label Edge Router
(LER) would be an MPLS "end system".)
link
A connection between two DetNet nodes. It may be composed of
a physical link or a sub-network technology that can provide
appropriate traffic delivery for DetNet flows.
relay system
A router, transit node, bridge, Label Switch Router (LSR),
firewall, or any other system that forwards packets from one
interface to another.
reservation
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A trail of configuration between source to destination(s)
through relay systems associated with a DetNet flow, required
to deliver the benefits of DetNet.
source
An end system capable of sourcing a DetNet flow.
2.2. IEEE 802 TSN to DetNet dictionary
This section also serves as a dictionary for translating from the
terms used by the IEEE 802 Time-Sensitive Networking (TSN) Task Group
to those of the DetNet WG.
listener
The IEEE 802 term for a destination of a DetNet flow.
stream
The IEEE 802 term for a DetNet flow.
talker
The IEEE 802 term for the source of a DetNet flow.
3. Providing the DetNet Quality of Service
DetNet Quality of Service is expressed in terms of:
o Minimum and maximum end-to-end latency from source to destination;
o Probability of loss of a packet, under various assumptions as to
the operational states of the relay systems and links;
It is a distinction of DetNet that it is concerned solely with worst-
case values for the end-to-end latency. Average, mean, or typical
values are of no interest, because they do not affect the ability of
a real-time system to perform its tasks. In general, a trivial
priority-based queuing scheme will give better average latency to a
data flow than DetNet, but of course, the worst-case latency is
essentially unbounded.
Three techniques are employed by DetNet to achieve these QoS
parameters:
a. Zero congestion loss (Section 3.1). Network resources such as
link bandwidth, buffers, queues, shapers, and scheduled input/
output slots are assigned in each relay system to the use of a
specific DetNet flow or class of DetNet flows. Given a finite
amount of buffer space, zero congestion loss necessarily ensures
a bounded end-to-end latency. Depending on the resources
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employed, a minimum latency, and thus bounded jitter, can also be
achieved.
b. Pinned paths (Section 3.2). Point-to-point paths or point-to-
multipoint trees through the network from a source to one or more
destinations can be established, and DetNet flows assigned to
follow a particular path or tree.
c. Packet replication and deletion (Section 3.3). End systems and/
or relay systems can number packets sequentially, replicate them,
and later eliminate all but one of the replicants, at multiple
points in the network in order to ensure that one (or more)
equipment failure events still leave at least one path intact for
a DetNet flow. This function is a "hitless" version of, e.g.,
the 1+1 linear protection in [RFC6372]. That is, instead of
switching from one flow to the other when a failure of a flow is
detected, DetNet combines both flows, and performs a packet-by-
packet selection of which to discard, based on sequence number.
These techniques address both of the DetNet QoS requirements. Given
that relay nodes have a finite amount of buffer space, zero
congestion loss (Section 3.1) necessarily results in a maximum end-
to-end latency. It also addresses the largest contribution to packet
loss, which is buffer congestion. Packet replication and deletion
mitigates the other most important contributions to packet loss,
namely random media errors and equipment failure.
These three techniques can be applied independently, giving eight
possible combinations, including none (no DetNet), although some
combinations are of wider utility than others. This separation keeps
the protocol stack coherent and maximizes interoperability with
existing and developing standards in this (IETF) and other Standards
Development Organizations. Some examples of typical expected
combinations:
o Pinned paths (a) plus packet replication (b) are exactly the
techniques employed by [HSR-PRP]. Pinned paths are achieved by
limiting the physical topology of the network, and the
sequentialization, replication, and duplicate elimination are
facilitated by packet tags added at the front or the end of
Ethernet frames.
o Zero congestion loss (a) alone is is offered by IEEE 802.1 Audio
Video bridging [IEEE802.1BA-2011]. As long as the network suffers
no failures, zero congestion loss can be achieved through the use
of a reservation protocol (MSRP), shapers in every relay system
(bridge), and a bit of network calculus.
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o Using all three together gives maximum protection.
There are, of course, simpler methods available (and employed, today)
to achieve levels of latency and packet loss that are satisfactory
for many applications. Prioritization and over-provisioning is one
such technique. However, these methods generally work best in the
absence of any significant amount of non-critical traffic in the
network (if, indeed, such traffic is supported at all), or work only
if the critical traffic constitutes only a small portion of the
network's theoretical capacity, or work only if all systems are
functioning properly, or in the absence of actions by end systems
that disrupt the network's operations.
There are any number of methods in use, defined, or in progress for
accomplishing each of the above techniques. It is expected that this
DetNet Architecture will assist various vendors, users, and/or
"vertical" Standards Development Organizations (dedicated to a single
industry) to make selections among the available means of
implementing DetNet networks.
3.1. Zero Congestion Loss
The primary means by which DetNet achieves its QoS assurances is to
completely eliminate congestion at an output port as a cause of
packet loss. Given that a DetNet flow cannot be throttled, this can
be achieved only by the provision of sufficient buffer storage at
each hop through the network to ensure that no packets are dropped
due to a lack of buffer storage.
Ensuring adequate buffering requires, in turn, that the source, and
every relay system along the path to the destination (or nearly every
relay system -- see Section 4.3.2) be careful to regulate its output
to not exceed the data rate for any DetNet flow, except for brief
periods when making up for interfering traffic. Any packet sent
ahead of its time potentially adds to the number of buffers required
by the next hop, and may thus exceed the resources allocated for a
particular DetNet flow.
The low-level mechanisms described in Section 4.4 provide the
necessary regulation of transmissions by an edge system or relay
system to ensure zero congestion loss. The reservation of the
bandwidth and buffers for a DetNet flow requires the provisioning
described in Section 4.9.
A DetNet node may have other resources requiring allocation and/or
scheduling, that might otherwise be over-subscribed and trigger
congestion loss.
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3.2. Pinned paths
In networks controlled by typical peer-to-peer protocols such as IEEE
802.1 ISIS bridged networks or IETF OSPF routed networks, a network
topology event in one part of the network can impact, at least
briefly, the delivery of data in parts of the network remote from the
failure or recovery event. Thus, even redundant paths through a
network, if controlled by the typical peer-to-peer protocols, do not
eliminate the chances of brief losses of contact.
Many real-time networks rely on physical rings or chains of two-port
devices, with a relatively simple ring control protocol. This
supports redundant paths with a minimum of wiring. As an additional
benefit, ring topologies can often utilize different topology
management protocols than those used for a mesh network, with a
consequent reduction in the response time to topology changes. Of
course, this comes at some cost in terms of increased hop count, and
thus latency, for the typical path.
In order to get the advantages of low hop count and still ensure
against even very brief losses of connectivity, DetNet employs pinned
paths, where the path taken by a given DetNet flow does not change,
at least immediately, and likely not at all, in response to network
topology events. When combined with packet replication and deletion
(Section 3.3), this results in a high likelihood of continuous
connectivity. Pinned paths are commonly used in MPLS TE LSPs.
3.3. Packet replication and deletion
After congestion loss has been eliminated, the most important causes
of packet loss are random media and/or memory faults, and equipment
failures. Both causes of packet loss can be greatly reduced by
sending the same packets over multiple paths.
Packet replication and deletion, also known as seamless redundancy
[HSR-PRP], or 1+1 hitless protection, involves three capabilities:
o Providing sequencing information, once, to the packets of a DetNet
flow. This may be done by adding a sequence number or time stamp
as part of DetNet, or may be inherent in the packet, e.g. in a
transport protocol.
o Replicating these packets and, typically, sending them along at
least two different paths to the destination(s). (Often, the
pinned paths of Section 3.2.)
o Discarding duplicated packets.
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In the simplest case, this amounts to replicating each packet in a
source that has two interfaces, and conveying them through the
network, along separate paths, to the similarly dual-homed
destinations, that discard the extras. This ensures that one path
(with zero congestion loss) remains, even if some relay system fails.
The sequence numbers can also be used for loss detection and for re-
ordering.
Alternatively, relay systems in the network can provide replication
and elimination facilities at various points in the network, so that
multiple failures can be accommodated.
This is shown in the following figure, where the two relay systems
each replicate (R) the DetNet flow on input, sending the DetNet flow
to both the other relay system and to the end system, and eliminate
duplicates (E) on the output interface to the right-hand end system.
Any one link in the network can fail, and the Detnet flow can still
get through. Furthermore, two links can fail, as long as they are in
different segments of the network.
> > > > > > > > relay > > > > > > > >
> /------------+ R system E +------------\ >
> / v + ^ \ >
end R + v | ^ + E end
system + v | ^ + system
> \ v + ^ / >
> \------------+ R relay E +------------/ >
> > > > > > > > system > > > > > > > >
Figure 1
Note that packet replication and deletion does not react to and
correct failures; it is entirely passive. Thus, intermittent
failures, mistakenly created access control lists, or misrouted data
is handled just the same as the equipment failures that are detected
handled by typical routing and bridging protocols.
4. DetNet Architecture
4.1. Elements of DetNet Architecture
The DetNet architecture has a number of elements, discussed in the
following sections. Note that not every application requires all of
these elements.
a. A model for the definition, identification, and operation of
DetNet flows (Section 4.3), for use by relay systems to classify
and process individual packets following per-flow rules.
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b. A model for the flow of data out of an end system or through a
relay system that can be used to predict the bounds for that
system's impact on the QoS of a DetNet flow, for use by the
Controllers to configure policing and shaping engines in Network
Systems over the Southbound interface. The model includes:
1. A model for queuing, transmission selection, shaping,
preemption, and timing resources that can be used by an end
system or relay system to control the selection of packets
output on an interface. These models must have sufficiently
well-defined characteristics, both individually and in the
aggregate, to give predictable results for the QoS for DetNet
packets (Section 4.4).
2. A model for identifying misbehaving DetNet flows and
mitigating their impact on properly functioning DetNet flows
(Section 4.6).
c. A model for the relay system to inform the controller(s) of the
information it needs for adequate path computations (Section 4.2)
including:
1. Systems' individual capabilities (e.g. can do replication,
can do precise time).
2. Link capabilities and resources (e.g. bandwidth, transmission
delay, hardware deterministic support to the physical layer,
...)
3. Physical resources (total and available buffers, timers,
queues, etc)
4. Network Adjacencies (neighbors)
d. A model for the provision of a service, by end systems or relay
systems, to replicate and forward a DetNet flow over redundant
paths. The model includes:
1. A model for specifying multiple stable paths across a network
that can perform packet forwarding at both Layer 3 and at
lower layers, to which specific DetNet flows can be assigned
(Section 4.2).
2. A model and data plane format(s) for sequencing and
replicating the packets of a DetNet flow, typically at or
near the source, sending the replicated DetNet flows over
different stable paths, merging and/or re-replicating those
packets at other points in the network, and finally
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eliminating the duplicates, typically at or near the
destination(s), in order to provide high availability
(Section 3.3).
e. The protocol stack model for an end system and/or a relay system
should support the above elements in a manner that maximizes the
applicability of existing standards and protocols to the DetNet
problem, and allows for the creation of new protocols only where
needed, thus making DetNet an add-on feature to existing
networks, rather than a new way to do networking. In particular
this protocol stack supports networks in which the path from
source to destination(s) includes bridges and/or routers in any
order (Section 4.7).
f. A variety of models for the provisioning of DetNet flows can be
envisioned, including orchestration by a central controller or by
a federation of controllers, via control plane protocols running
on relay systems and end systems, by off-line configuration, or
by a combination of these methods. The provisioning models are
similar to existing Layer-2 and Layer-3 models, in order to
minimize the amount of innovation required in this area
(Section 4.9).
4.2. Traffic Engineering for DetNet
Traffic Engineering Architecture and Signaling (TEAS) [TEAS] defines
traffic-engineering architectures for generic applicability across
packet and non-packet networks. From TEAS perspective, Traffic
Engineering (TE) refers to techniques that enable operators to
control how specific traffic flows are treated within their networks.
Because if its very nature of establishing pinned optimized paths,
Deterministic Networking can be seen as a new, specialized branch of
Traffic Engineering, and inherits its architecture with a separation
into planes.
The Deterministic Networking architecture is thus composed of three
planes, a (User) Application Plane, a Controller Plane, and a Network
Plane, which echoes that of Software-Defined Networking (SDN): Layers
and Architecture Terminology [RFC7426] which is represented below:
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SDN Layers and Architecture Terminology per RFC 7426
o--------------------------------o
| |
| +-------------+ +----------+ |
| | Application | | Service | |
| +-------------+ +----------+ |
| Application Plane |
o---------------Y----------------o
|
*-----------------------------Y---------------------------------*
| Network Services Abstraction Layer (NSAL) |
*------Y------------------------------------------------Y-------*
| |
| Service Interface |
| |
o------Y------------------o o---------------------Y------o
| | Control Plane | | Management Plane | |
| +----Y----+ +-----+ | | +-----+ +----Y----+ |
| | Service | | App | | | | App | | Service | |
| +----Y----+ +--Y--+ | | +--Y--+ +----Y----+ |
| | | | | | | |
| *----Y-----------Y----* | | *---Y---------------Y----* |
| | Control Abstraction | | | | Management Abstraction | |
| | Layer (CAL) | | | | Layer (MAL) | |
| *----------Y----------* | | *----------Y-------------* |
| | | | | |
o------------|------------o o------------|---------------o
| |
| CP | MP
| Southbound | Southbound
| Interface | Interface
| |
*------------Y---------------------------------Y----------------*
| Device and resource Abstraction Layer (DAL) |
*------------Y---------------------------------Y----------------*
| | | |
| o-------Y----------o +-----+ o--------Y----------o |
| | Forwarding Plane | | App | | Operational Plane | |
| o------------------o +-----+ o-------------------o |
| Network Device |
+---------------------------------------------------------------+
Figure 2
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4.2.1. The Application Plane
Per [RFC7426], the Application Plane includes both applications and
services. In particular, the Application Plane incorporates the User
Agent, a specialized application that interacts with the end user /
operator and performs requests for Deterministic Networking 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. An abstraction of the flow
called a Traffic Specification (TSpec) provides the representation.
This abstraction is used to place a reservation over the (Northbound)
Service Interface and within the Application plane. It is associated
with an abstraction of location, such as IP addresses and DNS names,
to identify the end systems and eventually specify intermediate relay
systems.
4.2.2. The Controller Plane
The Controller Plane corresponds to the aggregation of the Control
and Management Planes in [RFC7426], though Common Control and
Measurement Plane (CCAMP) [CCAMP] makes an additional distinction
between management and measurement. When the logical separation of
the Control, Measurement and other Management entities is not
relevant, the term Controller Plane is used for simplicity to
represent them all, and the term controller refers to any device
operating in that plane, whether is it a Path Computation entity or a
Network Management entity (NME). The Path Computation Element (PCE)
[PCE] 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.
One or more PCE(s) collaborate to implement the requests from the FME
as Per-fFlow Per-Hop Behaviors installed in the relay systems for
each individual flow. The PCEs place each flow along a deterministic
sequence of relay systems so as to respect per-flow constraints such
as security and latency, and optimize the overall result for metrics
such as an abstract aggregated cost. The deterministic sequence can
typically be more complex than a direct sequence and include
redundancy path, with one or more packet replication and elimination
points.
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4.2.3. The Network 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 Forwarding Plane (data plane), Application, and
Operational Plane (control plane) aspects.
The network Plane comprises the Network Interface Cards (NIC) in the
end systems, which are typically IP hosts, and relay systems, which
are typically IP routers and switches. Network-to-Network Interfaces
such as used for Traffic Engineering path reservation in [RFC5921],
as well as User-to-Network Interfaces (UNI) such as provided by the
Local Management Interface (LMI) between network and end systems, are
both part of the Network Plane, both in the control plane and the
data plane.
A Southbound (Network) Interface enables the entities in the
Controller Plane to communicate with devices in the Network Plane.
This interface leverages and extends TEAS to describe the physical
topology and resources in the Network Plane.
Flow Management Entity
End End
System System
-+-+-+-+-+-+-+ Northbound -+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-
PCE PCE PCE PCE
-+-+-+-+-+-+-+ Southbound -+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-
Relay Relay Relay Relay
System System System System
NIC NIC
Relay Relay Relay Relay
System System System System
Figure 3
The relay systems (and eventually the end systems NIC) expose their
capabilities and physical resources to the controller (the PCE), and
update the PCE with their dynamic perception of the topology, across
the Southbound Interface. In return, the PCE(s) set the per-flow
paths up, providing a Flow Characterization that is more tightly
coupled to the relay system Operation than a TSpec.
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At the Network plane, relay systems may exchange information
regarding the state of the paths, between adjacent systems and
eventually with the end systems, and forward packets within
constraints associated to each flow, or, when unable to do so,
perform a last resort operation such as drop or declassify.
This specification focuses on the Southbound interface and the
operation of the Network Plane.
4.3. DetNet flows
4.3.1. Source guarantees
DetNet flows can by synchronous or asynchronous. In synchronous
DetNet flows, at least the relay systems (and possibly the end
systems) are closely time synchronized, typically to better than 1
microsecond. By transmitting packets from different DetNet flows or
classes of DetNet flows at different times, using repeating schedules
synchronized among the relay systems, resources such as buffers and
link bandwidth can be shared over the time domain among different
DetNet flows. There is a tradeoff among techniques for synchronous
DetNet flows between the burden of fine-grained scheduling and the
benefit of reducing the required resources, especially buffer space.
In contrast, asynchronous DetNet flows are not coordinated with a
fine-grained schedule, so relay and end systems must assume worst-
case interference among DetNet flows contending for buffer resources.
Asynchronous DetNet flows are characterized by:
o A maximum packet size;
o An observation interval; and
o A maximum number of transmissions during that observation
interval.
These parameters, together with knowledge of the protocol stack used
(and thus the size of the various headers added to a packet), limit
the number of bit times per observation interval that the DetNet flow
can occupy the physical medium.
The source promises that these limits will not be exceeded. If the
source transmits less data than this limit allows, the unused
resources such as link bandwidth can be made available by the system
to non-DetNet packets. However, making those resources available to
DetNet packets in other DetNet flows would serve no purpose. Those
other DetNet flows have their own dedicated resources, on the
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assumption that all DetNet flows can use all of their resources over
a long period of time.
Note that there is no provision in DetNet for throttling DetNet flows
(reducing the transmission rate via feedback); the assumption is that
a DetNet flow, to be useful, must be delivered in its entirety. That
is, while any useful application is written to expect a certain
number of lost packets, the real-time applications of interest to
DetNet demand that the loss of data due to the network is
extraordinarily infrequent.
Although DetNet strives to minimize the changes required of an
application to allow it to shift from a special-purpose digital
network to an Internet Protocol network, one fundamental shift in the
behavior of network applications is impossible to avoid--the
reservation of resources before the application starts. 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 unthrottled (though bandwidth
limited) DetNet flows means that bridges and routers have to dedicate
buffer resources to specific DetNet flows or to classes of DetNet
flows. The requirements of each reservation have to be translated
into the parameters that control each system's queuing, shaping, and
scheduling functions and delivered to the hosts, bridges, and
routers.
4.3.2. Incomplete Networks
The presence in the network of relay systems that are not fully
capable of offering DetNet services complicates the ability of the
relay systems and/or controller to allocate resources, as extra
buffering, and thus extra latency, must be allocated at points
downstream from the non-DetNet relay system for a DetNet flow.
4.4. Queuing, Shaping, Scheduling, and Preemption
As described above, DetNet achieves its aims by reserving bandwidth
and buffer resources at every hop along the path of the DetNet flow.
The reservation itself is not sufficient, however. Implementors and
users of a number of proprietary and standard real-time networks have
found that standards for specific data plane techniques are required
to enable these assurances to be made in a multi-vendor network. The
fundamental reason is that latency variation in one system results in
the need for extra buffer space in the next-hop system(s), which in
turn, increases the worst-case per-hop latency.
Standard queuing and transmission selection algorithms allow a
central controller to compute the latency contribution of each relay
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node to the end-to-end latency, to compute the amount of buffer space
required in each relay system for each incremental DetNet flow, and
most importantly, to translate from a flow specification to a set of
values for the managed objects that control each relay or end system.
The IEEE 802 has specified (and is specifying) a set of queuing,
shaping, and scheduling algorithms that enable each relay system
(bridge or router), and/or a central controller, to compute these
values. These algorithms include:
o A credit-based shaper [IEEE802.1Q-2014] Clause 34.
o Time-gated queues governed by a rotating time schedule,
synchronized among all relay nodes [IEEE802.1Qbv].
o Synchronized double (or triple) buffers driven by synchronized
time ticks. [IEEE802.1Qch].
o Pre-emption of an Ethernet packet in transmission by a packet with
a more stringent latency requirement, followed by the resumption
of the preempted packet [IEEE802.1Qbu], [IEEE802.3br].
While these techniques are currently embedded in Ethernet and
bridging standards, we can note that they are all, except perhaps for
packet preemption, equally applicable to other media than Ethernet,
and to routers as well as bridges.
4.5. Coexistence with normal traffic
A DetNet network supports the dedication of a high proportion (e.g.
75%) of the network bandwidth to DetNet flows. But, no matter how
much is dedicated for DetNet flows, it is a goal of DetNet to coexist
with with existing Class of Service schemes (e.g., DiffServ). It is
also important that non-DetNet traffic not disrupt the DetNet flow,
of course (see Section 4.6 and Section 7). For these reasons:
o Bandwidth (transmission opportunities) not utilized by a DetNet
flow are available to non-DetNet packets (though not to other
DetNet flows).
o DetNet flows can be shaped or scheduled, in order to ensure that
the highest-priority non-DetNet packet also is ensured a worst-
case latency (at any given hop).
o When transmission opportunities for DetNet flows are scheduled in
detail, then the algorithm constructing the schedule should leave
sufficient opportunities for non-DetNet packets to satisfy the
needs of the users of the network. Detailed scheduling can also
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permit the time-shared use of buffer resources by different DetNet
flows.
Ideally, the net effect of the presence of DetNet flows in a network
on the non-DetNet packets is primarily a reduction in the available
bandwidth.
4.6. Fault Mitigation
One key to building robust real-time systems is to reduce the
infinite variety of possible failures to a number that can be
analyzed with reasonable confidence. DetNet aids in the process by
providing filters and policers to detect DetNet packets received on
the wrong interface, or at the wrong time, or in too great a volume,
and to then take actions such as discarding the offending packet,
shutting down the offending DetNet flow, or shutting down the
offending interface.
It is also essential that filters and service remarking be employed
at the network edge to prevent non-DetNet packets from being mistaken
for DetNet packets, and thus impinging on the resources allocated to
DetNet packets.
There exist techniques, at present and/or in various stages of
standardization, that can perform these fault mitigation tasks that
deliver a high probability that misbehaving systems will have zero
impact on well-behaved DetNet flows, except of course, for the
receiving interface(s) immediately downstream of the misbehaving
device.
4.7. Protocol Stack Model
[IEEE802.1CB], Annex C, offers a description of the TSN protocol
stack. It may serve as the foundation for the DetNet model which
will be defined by the working group. While this standard is a work
in progress, a consensus around the basic architecture has formed.
This stack is summarized in Figure 4.
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DetNet Protocol Stack
+--------------------------------+
| Upper Layers |
+--------------------------------+
| Sequence generation/recovery |
+--------------------------------+
| DetNet flow splitting/merging |
+--------------------------------+
| Sequence encode/decode |
+--------------------------------+
| DetNet flow encode/decode |
+--------------------------------+
| Lower layers |
+--------------------------------+
Figure 4
Not all layers are required for any given application, or even for
any given network. The layers are, from top to bottom:
Sequence generation/recovery
Supplies the sequence number for packet replication and
deletion (Section 3.3) for packets going down the stack (if
not already present), and discards duplicate packets coming
up the stack.
DetNet flow splitting/merging
Replicates packets going down the stack into two DetNet
flows, and merges DetNet flows together for packets coming up
the stack, based on the packet's DetNet flow identifier.
Needed for packet replication and deletion (Section 3.3).
Sequence encode/decode
Encodes the sequence number into packets going down the
stack, and extracts the sequence number from packets coming
up the stack. This function may or may not be a null
transformation of the packet, and for some protocols, is not
explicitly present, being included in the DetNet flow encode/
decode layer, below.
DetNet flow encode/decode
Encapsulates packets going down the stack, based on the
packet's locally-significant DetNet flow identifier, in order
to identify to which DetNet flow the packet belongs, and
extracts a locally-significant DetNet flow identifier from
packets coming up the stack. This may be a null
transformation (e.g., for DetNet flows identified by IP
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5-tuple) or might be an explicit encapsulation (e.g., for
DetNet flows identified with an MPLS label). DetNet flow
identification is the basis for packet replication and
deletion, for assigning per-flow resources (if any) to
packets and for defense against misbehaving systems
(Section 4.6). When DetNet flows are assigned to pinned
paths, this layer can be indistinguishable from the data
forwarding layer(s).
The reader is likely to notice that Figure 4 does not specify the
relationship between the DetNet layers, the IP layers, and the link
layers. This is intentional, because they can usefully be placed
different places in the stack, and even in mulitple places, depending
on where their peers are placed.
4.8. Advertising resources, capabilities and adjacencies
There are three classes of information that a central controller or
decentralized control plane needs to know that can only be obtained
from the end systems and/or relay systems in the network. When using
a peer-to-peer control plane, some of this information may be
required by a system's neighbors in the network.
o Details of the system's capabilities that are required in order to
accurately allocate that system's resources, as well as other
systems' resources. This includes, for example, which specific
queuing and shaping algorithms are implemented (Section 4.4), the
number of buffers dedicated for DetNet allocation, and the worst-
case forwarding delay.
o The dynamic state of an end or relay system's DetNet resources.
o The identity of the system's neighbors, and the characteristics of
the link(s) between the systems, including the length (in
nanoseconds) of the link(s).
4.9. Provisioning model
4.9.1. Centralized Path Computation and Installation
A centralized routing model, such as provided with a PCE (RFC 4655
[RFC4655]), enables global and per-flow optimizations. (See
Section 4.2.) The model is attractive but a number of issues are
left to be solved. In particular:
o Whether and how the path computation can be installed by 1) an end
device or 2) a Network Management entity,
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o And how the path is set up, either by installing state at each hop
with a direct interaction between the forwarding device and the
PCE, or along a path by injecting a source-routed request at one
end of the path.
4.9.2. Distributed Path Setup
Whether a distributed alternative without a PCE can be valuable
should be studied as well. Such an alternative could for instance
inherit from the Resource ReSerVation Protocol [RFC3209] (RSVP-TE)
flows.
In a Layer-2 only environment, or as part of a layered approach to a
mixed environment, IEEE 802.1 also has work, either completed or in
progress. [IEEE802.1Q-2014] Clause 35 describes SRP, a peer-to-peer
protocol for Layer-2 roughly analogous to RSVP. Almost complete is
[IEEE802.1Qca], which defines how ISIS can provide multiple disjoint
paths or distribution trees. Also in progress is [IEEE802.1Qcc],
which expands the capabilities of SRP.
The integration/interaction of the DetNet control layer an underlying
IEEE 802.1 sub-network control layer will need to be defined.
4.10. Scaling to larger networks
Reservations for individual DetNet flows require considerable state
information in each relay system, especially when adequate fault
mitigation (Section 4.6) is required. The DetNet data plane, in
order to support larger numbers of DetNet flows, must support the
aggregation of DetNet flows into tunnels, which themselves can be
viewed by the relay systems' data planes largely as individual DetNet
flows. Without such aggregation, the per-relay system may limit the
scale of DetNet networks.
4.11. Connected islands vs. networks
Given that users have deployed examples of the IEEE 802.1 TSN TG
standards, which provide capabilities similar to DetNet, it is
obvious to ask whether the IETF DetNet effort can be limited to
providing Layer-2 connections (VPNs) between islands of bridged TSN
networks. While this capability is certainly useful to some
applications, and must not be precluded by DetNet, tunneling alone is
not a sufficient goal for the DetNet WG. As shown in the
Deterministic Networking Use Cases draft [I-D.ietf-detnet-use-cases],
there are already deployments of Layer-2 TSN networks that are
encountering the well-known problems of over-large broadcast domains.
Routed solutions, and combinations routed/bridged solutions, are both
required.
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5. Compatibility with Layer-2
Standards providing similar capabilities for bridged networks (only)
have been and are being generated in the IEEE 802 LAN/MAN Standards
Committee. The present architecture describes an abstract model that
can be applicable both at Layer-2 and Layer-3, and over links not
defined by IEEE 802. It is the intention of the authors (and
hopefully, as this draft progresses, of the DetNet Working Group)
that IETF and IEEE 802 will coordinate their work, via the
participation of common individuals, liaisons, and other means, to
maximize the compatibility of their outputs.
DetNet enabled systems and nodes can be interconnected by sub-
networks, i.e., Layer 2 technologies. These sub-networks will
provide DetNet compatible service for support of DetNet traffic.
Examples of sub-networks include 802.1TSN and a point-to-point OTN
link. Of course, multi-layer DetNet systems may be possible too,
where one DetNet appears as a sub-network, and provides service to, a
higher layer DetNet system.
6. Open Questions
There are a number of architectural questions that will have to be
resolved before this document can be submitted for publication.
Aside from the obvious fact that this present draft is subject to
change, there are specific questions to which the authors wish to
direct the readers' attention.
6.1. Data plane shapers and schedulers
A number of techniques have been defined and are being defined by
IEEE 802 for queuing, shaping, and scheduling transmissions on
EtherNet media, most of which are directly applicable to any other
medium. Specific selections of supported techniques are required,
because minimizing, and even eliminating, congestion losses depends
strongly on the details of the per-hop behavior of sources and relay
systems.
The present authors expect that, at least, the IEEE 802 mechanisms
will be supported.
6.2. DetNet flow identification and sequencing
The techniques to be used for DetNet flow identification must be
settled. The following paragraphs provide a snapshot of the authors'
opinions at the time of writing. These authors anticipate the
submission of drafts in the near future on this subject.
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IEEE 802.1 TSN streams are identified by giving each stream (DetNet
flow) a {VLAN identifier, destination MAC address} pair that is
unique in the bridged network, and that the MAC address must be a
multicast address. If a source is generating, for example, two
unicast UDP flows to the same destination, one DetNet and one not,
the DetNet flow's packets must be transformed at some point to have a
multicast destination MAC address, and perhaps, a different VLAN than
the non-DetNet flow's packets.
A similar provision would apply to DetNet packets that are identified
by MPLS labels; any bridges between the LSRs need a {VLAN identifier,
destination MAC address} pair uniquely identifying the DetNet flow in
the bridged network.
Provision is made in current draft of [IEEE802.1CB] to make these
transformations either in a Layer-2 shim in the source end system, on
the output side of a router or LSR, or in a proxy function in the
first-hop bridge. It remains to be seen whether this provision is
adequate and/or acceptable to the IETF DetNet WG.
There are also questions regarding the sequentialization of packets
for use with packet replication and deletion (Section 3.3).
[IEEE802.1CB] defines an EtherNet tag carrying a sequence number. If
MPLS Pseudowires are used with a control word containing a sequence
number, the relationship and interworking between these two formats
must be defined.
6.3. Flat vs. hierarchical control
Boxes that are solely routers or solely bridges are rare in today's
market. In a multi-tenant data center, multiple users' virtual
Layer-2/Layer-3 topologies exist simultaneously, implemented on a
network whose physical topology bears only accidental resemblance to
the virtual topologies.
While the forwarding topology (the bridges and routers) are an
important consideration for a DetNet Flow Management Entity
(Section 4.2.1), so is the purely physical topology. Ultimately, the
model used by the management entities is based on boxes, queues, and
links. The authors hope that the work of the TEAS WG will help to
clarify exactly what model parameters need to be traded between the
relay systems and the controller(s).
6.4. Peer-to-peer reservation protocol
As described in Section 4.9.2, the DetNet WG needs to decide whether
to support a peer-to-peer protocol for a source and a destination to
reserve resources for a DetNet stream. Assuming that enabling the
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involvement of the source and/or destination is desirable (see
Deterministic Networking Use Cases [I-D.ietf-detnet-use-cases]), it
remains to decide whether the DetNet WG will make it possible to
deploy at least some DetNet capabilities in a network using only a
peer-to-peer protocol, without a central controller.
(Note that a UNI (see Section 4.2.3) between an end system and an
edge relay system, for sources and/or listeners to request DetNet
services, can be either the first hop of a per-to-peer reservation
protocol, or can be deflected by the edge relay system to a central
controller for resolution. Similarly, a decision by a central
controller can be effected by the controller instructing the end
system or edge relay system to initiate a per-to-peer protocol
activity.)
6.5. Wireless media interactions
Deterministic Networking Use Cases [I-D.ietf-detnet-use-cases]
illustrates cases where wireless media are needed in a DetNet
network. Some wireless media in general use, such as IEEE 802.11
[IEEE802.1Q-2014], have significantly higher packet loss rates than
typical wired media, such as Ethernet [IEEE802.3-2012]. IEEE 802.11
includes support for such features as MAC-layer acknowledgements and
retransmissions.
The techniques described in Section 3 are likely to improve the
ability of a mixed wired/wireless network to offer the DetNet QoS
features. The interaction of these techniques with the features of
specific wireless media, although they may be significant, cannot be
addressed in this document. It remains to be decided to what extent
the DetNet WG will address them, and to what extent other WGs, e.g.
6TiSCH, will do so.
7. 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, itself. A man-in-the-middle attack,
for example, can impose, and then systematically 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.
Furthermore, in a control system where millions of dollars of
equipment, or even human lives, can be lost if the DetNet QoS is not
delivered, one must consider not only simple equipment failures,
where the box or wire instantly becomes perfectly silent, but bizarre
errors such as can be caused by software failures. Because there is
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essential no limit to the kinds of failures that can occur,
protecting against realistic equipment failures is indistinguishable,
in most cases, from protecting against malicious behavior, whether
accidental or intentional. See also Section 4.6.
Security must cover:
o the protection of the signaling protocol
o the authentication and authorization of the controlling systems
o the identification and shaping of the DetNet flows
8. IANA Considerations
This document does not require an action from IANA.
9. Acknowledgements
The authors wish to thank Jouni Korhonen, Erik Nordmark, George
Swallow, Rudy Klecka, Anca Zamfir, David Black, Thomas Watteyne,
Shitanshu Shah, Craig Gunther, Rodney Cummings, Wilfried Steiner,
Marcel Kiessling, Karl Weber, Ethan Grossman, Pat Thaler, and Lou
Berger for their various contribution with this work.
10. Access to IEEE 802.1 documents
To access password protected IEEE 802.1 drafts, see the IETF IEEE
802.1 information page at https://www.ietf.org/proceedings/52/slides/
bridge-0/tsld003.htm.
11. Informative References
[AVnu] http://www.avnu.org/, "The AVnu Alliance tests and
certifies devices for interoperability, providing a simple
and reliable networking solution for AV network
implementation based on the Audio Video Bridging (AVB)
standards.".
[CCAMP] IETF, "Common Control and Measurement Plane",
<https://datatracker.ietf.org/doc/charter-ietf-ccamp/>.
[HART] www.hartcomm.org, "Highway Addressable Remote Transducer,
a group of specifications for industrial process and
control devices administered by the HART Foundation".
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[HSR-PRP] IEC, "High availability seamless redundancy (HSR) is a
further development of the PRP approach, although HSR
functions primarily as a protocol for creating media
redundancy while PRP, as described in the previous
section, creates network redundancy. PRP and HSR are both
described in the IEC 62439 3 standard.",
<http://webstore.iec.ch/webstore/webstore.nsf/
artnum/046615!opendocument>.
[I-D.finn-detnet-problem-statement]
Finn, N. and P. Thubert, "Deterministic Networking Problem
Statement", draft-finn-detnet-problem-statement-05 (work
in progress), March 2016.
[I-D.ietf-6tisch-architecture]
Thubert, P., "An Architecture for IPv6 over the TSCH mode
of IEEE 802.15.4", draft-ietf-6tisch-architecture-09 (work
in progress), November 2015.
[I-D.ietf-6tisch-tsch]
Watteyne, T., Palattella, M., and L. Grieco, "Using
IEEE802.15.4e TSCH in an IoT context: Overview, Problem
Statement and Goals", draft-ietf-6tisch-tsch-06 (work in
progress), March 2015.
[I-D.ietf-detnet-use-cases]
Grossman, E., Gunther, C., Thubert, P., Wetterwald, P.,
Raymond, J., Korhonen, J., Kaneko, Y., Das, S., Zha, Y.,
Varga, B., Farkas, J., Goetz, F., and J. Schmitt,
"Deterministic Networking Use Cases", draft-ietf-detnet-
use-cases-08 (work in progress), March 2016.
[I-D.ietf-roll-rpl-industrial-applicability]
Phinney, T., Thubert, P., and R. Assimiti, "RPL
applicability in industrial networks", draft-ietf-roll-
rpl-industrial-applicability-02 (work in progress),
October 2013.
[I-D.svshah-tsvwg-deterministic-forwarding]
Shah, S. and P. Thubert, "Deterministic Forwarding PHB",
draft-svshah-tsvwg-deterministic-forwarding-04 (work in
progress), August 2015.
[IEEE802.11-2012]
IEEE, "Wireless LAN Medium Access Control (MAC) and
Physical Layer (PHY) Specifications", 2012,
<http://standards.ieee.org/getieee802/
download/802.11-2012.pdf>.
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[IEEE802.1AS-2011]
IEEE, "Timing and Synchronizations (IEEE 802.1AS-2011)",
2011, <http://standards.ieee.org/getIEEE802/
download/802.1AS-2011.pdf>.
[IEEE802.1BA-2011]
IEEE, "AVB Systems (IEEE 802.1BA-2011)", 2011,
<http://standards.ieee.org/getIEEE802/
download/802.1BA-2011.pdf>.
[IEEE802.1CB]
IEEE, "Frame Replication and Elimination for Reliability
(IEEE Draft P802.1CB)", 2016,
<http://www.ieee802.org/1/files/private/cb-drafts/>.
[IEEE802.1Q-2014]
IEEE, "MAC Bridges and VLANs (IEEE 802.1Q-2014", 2014,
<http://standards.ieee.org/getieee802/
download/802-1Q-2014.pdf>.
[IEEE802.1Qbu]
IEEE, "Frame Preemption", 2016,
<http://www.ieee802.org/1/files/private/bu-drafts/>.
[IEEE802.1Qbv]
IEEE, "Enhancements for Scheduled Traffic", 2016,
<http://www.ieee802.org/1/files/private/bv-drafts/>.
[IEEE802.1Qca]
IEEE, "Path Control and Reservation", 2015,
<http://www.ieee802.org/1/files/private/ca-drafts/>.
[IEEE802.1Qcc]
IEEE, "Stream Reservation Protocol (SRP) Enhancements and
Performance Improvements", 2016,
<http://www.ieee802.org/1/files/private/cc-drafts/>.
[IEEE802.1Qch]
IEEE, "Cyclic Queuing and Forwarding", 2016,
<http://www.ieee802.org/1/files/private/ch-drafts/>.
[IEEE802.1TSNTG]
IEEE Standards Association, "IEEE 802.1 Time-Sensitive
Networks Task Group", 2013,
<http://www.IEEE802.org/1/pages/avbridges.html>.
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[IEEE802.3-2012]
IEEE, "IEEE Stabdard for Ethernet", 2012,
<http://standards.ieee.org/getieee802/
download/802.3-2012.pdf>.
[IEEE802.3br]
IEEE, "Interspersed Express Traffic", 2016,
<http://www.ieee802.org/3/br/>.
[IEEE802154]
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", June 2011.
[IEEE802154e]
IEEE standard for Information Technology, "IEEE std.
802.15.4e, Part. 15.4: Low-Rate Wireless Personal Area
Networks (LR-WPANs) Amendment 1: MAC sublayer", April
2012.
[ISA100.11a]
ISA/IEC, "ISA100.11a, Wireless Systems for Automation,
also IEC 62734", 2011, < http://www.isa100wci.org/en-
US/Documents/PDF/3405-ISA100-WirelessSystems-Future-broch-
WEB-ETSI.aspx>.
[ISA95] ANSI/ISA, "Enterprise-Control System Integration Part 1:
Models and Terminology", 2000, <https://www.isa.org/
isa95/>.
[ODVA] http://www.odva.org/, "The organization that supports
network technologies built on the Common Industrial
Protocol (CIP) including EtherNet/IP.".
[PCE] IETF, "Path Computation Element",
<https://datatracker.ietf.org/doc/charter-ietf-pce/>.
[Profinet]
http://us.profinet.com/technology/profinet/, "PROFINET is
a standard for industrial networking in automation.",
<http://us.profinet.com/technology/profinet/>.
[RFC2205] Braden, R., Ed., Zhang, L., Berson, S., Herzog, S., and S.
Jamin, "Resource ReSerVation Protocol (RSVP) -- Version 1
Functional Specification", RFC 2205, DOI 10.17487/RFC2205,
September 1997, <http://www.rfc-editor.org/info/rfc2205>.
Finn, et al. Expires September 22, 2016 [Page 28]
Internet-Draft Deterministic Networking Architecture March 2016
[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,
<http://www.rfc-editor.org/info/rfc3209>.
[RFC4655] Farrel, A., Vasseur, J., and J. Ash, "A Path Computation
Element (PCE)-Based Architecture", RFC 4655,
DOI 10.17487/RFC4655, August 2006,
<http://www.rfc-editor.org/info/rfc4655>.
[RFC5673] Pister, K., Ed., Thubert, P., Ed., Dwars, S., and T.
Phinney, "Industrial Routing Requirements in Low-Power and
Lossy Networks", RFC 5673, DOI 10.17487/RFC5673, October
2009, <http://www.rfc-editor.org/info/rfc5673>.
[RFC5921] Bocci, M., Ed., Bryant, S., Ed., Frost, D., Ed., Levrau,
L., and L. Berger, "A Framework for MPLS in Transport
Networks", RFC 5921, DOI 10.17487/RFC5921, July 2010,
<http://www.rfc-editor.org/info/rfc5921>.
[RFC6372] Sprecher, N., Ed. and A. Farrel, Ed., "MPLS Transport
Profile (MPLS-TP) Survivability Framework", RFC 6372,
DOI 10.17487/RFC6372, September 2011,
<http://www.rfc-editor.org/info/rfc6372>.
[RFC7384] Mizrahi, T., "Security Requirements of Time Protocols in
Packet Switched Networks", RFC 7384, DOI 10.17487/RFC7384,
October 2014, <http://www.rfc-editor.org/info/rfc7384>.
[RFC7426] Haleplidis, E., Ed., Pentikousis, K., Ed., Denazis, S.,
Hadi Salim, J., Meyer, D., and O. Koufopavlou, "Software-
Defined Networking (SDN): Layers and Architecture
Terminology", RFC 7426, DOI 10.17487/RFC7426, January
2015, <http://www.rfc-editor.org/info/rfc7426>.
[TEAS] IETF, "Traffic Engineering Architecture and Signaling",
<https://datatracker.ietf.org/doc/charter-ietf-teas/>.
[WirelessHART]
www.hartcomm.org, "Industrial Communication Networks -
Wireless Communication Network and Communication Profiles
- WirelessHART - IEC 62591", 2010.
Authors' Addresses
Finn, et al. Expires September 22, 2016 [Page 29]
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Norman Finn
Cisco Systems
170 W Tasman Dr.
San Jose, California 95134
USA
Phone: +1 408 526 4495
Email: nfinn@cisco.com
Pascal Thubert
Cisco Systems
Village d'Entreprises Green Side
400, Avenue de Roumanille
Batiment T3
Biot - Sophia Antipolis 06410
FRANCE
Phone: +33 4 97 23 26 34
Email: pthubert@cisco.com
Michael Johas Teener
Broadcom Corp.
3151 Zanker Rd.
San Jose, California 95134
USA
Phone: +1 831 824 4228
Email: MikeJT@broadcom.com
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