DetNet J. Korhonen, Ed.
Internet-Draft
Intended status: Standards Track B. Varga, Ed.
Expires: January 1, 2019 Ericsson
June 30, 2018
DetNet MPLS Data Plane Encapsulation
draft-ietf-detnet-dp-sol-mpls-00
Abstract
This document specifies Deterministic Networking data plane
encapsulation solutions. The described data plane solutions is
applied over an MPLS Packet Switched Networks.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
2.1. Terms used in this document . . . . . . . . . . . . . . . 4
2.2. Abbreviations . . . . . . . . . . . . . . . . . . . . . . 4
3. Requirements language . . . . . . . . . . . . . . . . . . . . 6
4. MPLS DetNet data plane overview . . . . . . . . . . . . . . . 6
4.1. DetNet data plane encapsulation requirements . . . . . . 12
5. DetNet encapsulation . . . . . . . . . . . . . . . . . . . . 13
5.1. End-system specific considerations . . . . . . . . . . . 13
5.2. DetNet domain specific considerations . . . . . . . . . . 15
5.2.1. DetNet Layer Two Service . . . . . . . . . . . . . . 15
5.2.2. DetNet Routing Service (IP over MPLS) . . . . . . . . 16
5.3. DetNet Inter-Working Function (DN-IWF) . . . . . . . . . 17
5.3.1. Networks with multiple technology segments . . . . . 17
5.3.2. DN-IWF related considerations . . . . . . . . . . . . 18
6. MPLS-based DetNet data plane solution . . . . . . . . . . . . 19
6.1. DetNet over MPLS Encapsulation Components . . . . . . . . 19
6.2. MPLS data plane encapsulation . . . . . . . . . . . . . . 21
6.3. DetNet control word . . . . . . . . . . . . . . . . . . . 22
6.4. Flow Identification . . . . . . . . . . . . . . . . . . . 23
6.5. Indication of the DetNet Payload Type . . . . . . . . . . 23
6.6. OAM Indication . . . . . . . . . . . . . . . . . . . . . 24
6.7. Flow Aggregation . . . . . . . . . . . . . . . . . . . . 24
6.7.1. Aggregation at the LSP . . . . . . . . . . . . . . . 25
6.7.2. Aggregating DetNet flows as a new DetNet flow . . . . 25
6.7.3. Simple Aggregation at the DetNet layer . . . . . . . 26
6.8. Service Layer Considerations . . . . . . . . . . . . . . 27
6.8.1. Edge node processing . . . . . . . . . . . . . . . . 27
6.8.2. Relay node processing . . . . . . . . . . . . . . . . 28
6.9. Other DetNet data plane considerations . . . . . . . . . 29
6.9.1. Class of Service . . . . . . . . . . . . . . . . . . 29
6.9.2. Quality of Service . . . . . . . . . . . . . . . . . 30
6.9.3. Cross-DetNet flow resource aggregation . . . . . . . 31
6.9.4. Layer 2 addressing and QoS Considerations . . . . . . 32
6.9.5. Time Synchronization . . . . . . . . . . . . . . . . 32
7. Management and control considerations . . . . . . . . . . . . 33
7.1. MPLS-based data plane . . . . . . . . . . . . . . . . . . 33
7.1.1. S-Label assignment and distribution . . . . . . . . . 33
7.1.2. Explicit routes . . . . . . . . . . . . . . . . . . . 33
7.2. Packet replication and elimination . . . . . . . . . . . 34
7.3. Congestion protection and latency control . . . . . . . . 35
7.4. Bidirectional traffic . . . . . . . . . . . . . . . . . . 35
7.5. Flow aggregation control . . . . . . . . . . . . . . . . 35
8. DetNet IP Operation over DetNet MPLS Service . . . . . . . . 35
9. IEEE 802.1 TSN Interconnection over DetNet MPLS Service . . . 36
10. DetNet MPLS Transport Layer Operation over IEEE 802.1 TSN
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Sub-Networks . . . . . . . . . . . . . . . . . . . . . . . . 36
11. DetNet MPLS Transport Layer Operation over IP DetNet PSNs . . 36
12. Security considerations . . . . . . . . . . . . . . . . . . . 38
13. IANA considerations . . . . . . . . . . . . . . . . . . . . . 38
14. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 39
15. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 41
16. References . . . . . . . . . . . . . . . . . . . . . . . . . 41
16.1. Normative references . . . . . . . . . . . . . . . . . . 41
16.2. Informative references . . . . . . . . . . . . . . . . . 44
Appendix A. Example of DetNet data plane operation . . . . . . . 45
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 46
1. Introduction
Deterministic Networking (DetNet) is a service that can be offered by
a network to DetNet flows. DetNet provides these flows with a low
packet loss rates and assured maximum end-to-end delivery latency.
General background and concepts of DetNet can be found in
[I-D.ietf-detnet-architecture].
This document specifies the DetNet data plane and the on-wire
encapsulation of DetNet flows over an MPLS-based Packet Switched
Network (PSN). The specified encapsulation provides the building
blocks to enable the DetNet service layer functions and allow flow
identification as described in the DetNet Architecture.
The DetNet transport layer functionality that provides congestion
protection for DetNet flows is assumed to be in place in a DetNet
node.
Furthermore, this document also describes how DetNet flows are
identified, and how a DetNet Relay/Edge/Transit nodes works. It also
describes the function and operation of the Packet Replication (PRF)
Packet Elimination (PEF) and Packet Ordering (POF) functions in the
MPLS data plane.
This document does not define the associated control plane functions,
or Operations, Administration, and Maintenance (OAM). It also does
not specify traffic handling capabilities required to deliver
congestion protection and latency control for DetNet flows at the
DetNet transport layer.
2. Terminology
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2.1. Terms used in this document
This document uses the terminology established in the DetNet
architecture [I-D.ietf-detnet-architecture] and the DetNet Data Plane
Solution Alternatives [I-D.ietf-detnet-dp-alt].
T-Label A label used to identify the LSP used to transport a
DetNet flow across an MPLS PSN, e.g., a hop-by-hop
label used between label switching routers (LSR).
S-Label A DetNet "service" label that is used between DetNet
nodes that implement also the DetNet service layer
functions. An S-Label is also used to identify a
DetNet flow at DetNet service layer.
PEF A Packet Elimination Function (PEF) eliminates
duplicate copies of packets received by an edge or a
relay node to prevent excess packets flooding the
network, or to prevent duplicate packets being sent out
of the DetNet domain.
PRF A Packet Replication Function (PRF) replicates DetNet
flow packets in an edge or a relay node and forwards
them to one or more next hops in the DetNet domain.
The number of packet copies sent to each next hop is a
DetNet Flow specific parameter at the node doing the
replication.
POF A Packet Order Function (POF) re-orders packets within
a DetNet flow that are received out of order. This
function may be implemented at an edge or a relay node.
PREOF Collective name for Packet Replication, Elimination,
and Ordering Functions.
d-CW A DetNet Control Word (d-CW) is used for sequencing and
identifying duplicate packets of a DetNet flow at the
DetNet service layer.
2.2. Abbreviations
The following abbreviations used in this document:
AC Attachment Circuit.
CE Customer Edge equipment.
CoS Class of Service.
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CW Control Word.
d-CW DetNet Control Word.
DetNet Deterministic Networking.
DF DetNet Flow.
DN-IWF DetNet Inter-Working Function.
L2 Layer 2.
L2VPN Layer 2 Virtual Private Network.
L3 Layer 3.
LSR Label Switching Router.
MPLS Multiprotocol Label Switching.
MPLS-TE Multiprotocol Label Switching - Traffic Engineering.
MPLS-TP Multiprotocol Label Switching - Transport Profile.
MS-PW Multi-Segment PseudoWire (MS-PW).
NSP Native Service Processing.
OAM Operations, Administration, and Maintenance.
PE Provider Edge.
PEF Packet Elimination Function.
PRF Packet Replication Function.
PREOF Packet Replication, Elimination and Ordering Functions.
POF Packet Ordering Function.
PSN Packet Switched Network.
PW PseudoWire.
QoS Quality of Service.
S-PE Switching Provider Edge.
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T-PE Terminating Provider Edge.
TSN Time-Sensitive Network.
3. Requirements language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in BCP
14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here.
4. MPLS DetNet data plane overview
This document describes how DetNet flows are carried over MPLS
networks. The DetNet Architecture, [I-D.ietf-detnet-architecture],
decomposes the DetNet data plane into two layers: a service layer and
a transport layer. The basic approach defined in this document
supports the DetNet service layer based on existing pseudowire (PW)
encapsulations and mechanisms, and supports the DetNet transport
layer based on existing MPLS Traffic Engineering encapsulations and
mechanisms. Background on PWs can be found in [RFC3985] and
[RFC3031].
DetNet MPLS
.
.
+-----------+
| Service | d-CW, S-Label
+-----------+
| Transport | T-Label(s)
+-----------+
.
.
Figure 1: DetNet adaptation to MPLS data plane
The MPLS DetNet data plane approach defined in this document is shown
in Figure 1. The service layer is supported by a DetNet control word
(d-CW) which conforms to the Generic PW MPLS Control Word (PWMCW)
defined in [RFC4385]. A d-CW identifying service label (S-Label) is
also used. The transport layer is supported by one or labels
(T-Labels).
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TSN Edge Transit Edge TSN
End System Node Node Node End System
(T-PE) (LSR) (T-PE)
+---------+ +.........+ +.........+ +---------+
| Appl. |<--:Svc Proxy:--End to End Svc.--:Svc Proxy:-->| Appl. |
+---------+ +---------+ +---------+ +---------+
| TSN | |TSN| |Svc|<-- DetNet flow -->: Service :-->| TSN |
+---------+ +---+ +---+ +---------+ +---------+ +---------+
|Transport| |Trp| |Trp| |Transport| |Trp| |Trp| |Transport|
+-------.-+ +--.+ +-.-+ +--.----.-+ +-.-+ +-.-+ +---.-----+
: Link : / ,-----. \ : Link : / ,-----. \
+........+ +-[ Sub ]-+ +........+ +-[ Sub ]-+
[Network] [Network]
`-----' `-----'
|<- TSN ->| |<----- DetNet MPLS ---->| |<-- TSN --->|
Figure 2: A TSN over DetNet MPLS Enabled Network
Figure 2 shows several node types defined in
[I-D.ietf-detnet-architecture]. DetNet Edge Nodes sit at the
boundary of a DetNet domain. They are responsible for mapping non-
DetNet aware traffic to DetNet services. They also support the
imposition and disposition of the required DetNet encapsulation.
These are functionally similar to pseudowire (PW) Terminating
Provider Edge (T-PE) nodes which use MPLS-TE LSPs.
Transit nodes are normal MPLS Label Switching Routers (LSRs). They
are generally unaware of the special requirements of DetNet flows,
although they need to provide traffic engineering services and proper
QoS to the LSPs associated with DetNet flows to enhance the prospect
of the LSPs meeting the DetNet service requirements. Some
implementations of transit nodes may be DetNet aware, but such nodes
just support the DetNet transport layer.
The MPLS LSP may be provided by any MPLS method (provisioned, RSVP-
TE, MPLS- TP, or MPLS Segment Routing (SR)).
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IP DetNet Relay Transit Relay IP DetNet
End System Node Node Node End System
(T-PE) (LSR) (T-PE)
+---------+ +---------+
| Appl. |<--------------- End to End Service ---------->| Appl. |
+---------+ .....-----+ +-----..... +---------+
| Service |<---: Service |-- DetNet flow ---| Service :-->| Service |
+---------+ +---------+ +---------+ +---------+ +---------+
|Transport| |Trp| |Trp| |Transport| |Trp| |Trp| |Transport|
+-------.-+ +-.-+ +-.-+ +---.---.-+ +-.-+ +-.-+ +---.-----+
: Link : / ,-----. \ : Link : / ,-----. \
+........+ +-[ Sub ]-+ +........+ +-[ Sub ]-+
[Network] [Network]
`-----' `-----'
|<-DN IP->| |<---- DetNet MPLS ---->| |<-DN IP->|
Figure 3: DetNet (DN) IP Over MPLS Network
Figure 3 and Figure 4, show different cases where relay nodes may be
used. Relay nodes are similar to edge nodes in that both are aware
of the needs of particular DetNet flows and take care to process them
in accordance with the required performance needs. They differ in
that relay nodes sit within a DetNet domain while edge nodes always
sit at DetNet domain boundaries. Both node types can enhance the
reliability of delivery by enabling the replication of packets so
that multiple copies, possibly over multiple paths are forwarded
through the DetNet domain. They also reduce the impact of
replication by eliminating surplus copies of DetNet packets. Relay
nodes may sit the boundary of an MPLS domain when the non-MPLS domain
is DetNet aware. Relay nodes are functionally similar to PW S-PEs
or, when at the edge of an MPLS network, T-PEs [RFC6073].
Figure 4 illustrates how DetNet can provide services for IEEE
802.1TSN end systems, CE1 and CE2, over a DetNet enabled network.
The edge nodes, E1 and E2, insert and remove required DetNet data
plane encapsulation. The 'X' in the edge nodes and relay node, R1,
represent a potential DetNet flow packet replication and elimination
point. This conceptually parallels L2VPN services, and could
leverage existing related solutions as discussed below.
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TSN |<------- End to End DetNet Service ------>| TSN
Service | Transit Transit | Service
TSN (AC) | |<-Tnl->| |<-Tnl->| | (AC) TSN
End | V V 1 V V 2 V V | End
System | +--------+ +--------+ +--------+ | System
+---+ | | E1 |=======| R1 |=======| E2 | | +---+
| |--|----|._X_....|..DF1..|.._ _...|..DF3..|...._X_.|---|---| |
|CE1| | | \ | | X | | / | | |CE2|
| | | \_.|..DF2..|._/ \_..|..DF4..|._/ | | |
+---+ | |=======| |=======| | +---+
^ +--------+ +--------+ +--------+ ^
| Edge Node Relay Node Edge Node |
| (T-PE) (S-PE) (T-PE) |
| |
|<--TSN--> <---- TSN Over DetNet MPLS ----> <--TSN-->|
| |
|<--- Emulated Time Sensitive Networking (TSN) Service --->|
DFx = DetNet Flow x
Figure 4: IEEE 802.1TSN over DetNet
Figure 5 illustrates how an end to end MPLS-based DetNet service is
provided in a more detail. In this case, the end systems, CE1 and
CE2, are able to send and receive DetNet flows, and R1 and R2 are
relay nodes as they sit in the middle of a DetNet network. For
example, an end system sends data encapsulated in MPLS. The 'X' in
the end systems, and relay nodes represents potential DetNet flow
packet replication and elimination points. Here the relay nodes may
change the underlying transport, for example tunneling MPLS over IP
Section 11, or simply interconnect network segments.
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DetNet DetNet
MPLS Service Transit Transit Service MPLS
DetNet | |<-Tnl->| |<-Tnl->| | DetNet
End | V 1 V V 2 V | End
System | +--------+ +--------+ +--------+ | System
+---+ | | R1 |=======| R2 |=======| R3 | | +---+
| X...DFa...|._X_....|..DF1..|.__ ___.|..DF3..|...._X_.|.DFa..|.X |
|CE1|========| \ | | X | | / |======|CE2|
| | | | \_.|..DF2..|._/ \__.|..DF4..|._/ | | | |
+---+ | |=======| |=======| | +---+
^ +--------+ +--------+ +--------+ ^
| Relay Node Relay Node Relay Node |
| (S-PE) (S-PE) (S-PE) |
| |
|<---------------------- DetNet MPLS --------------------->|
| |
|<--------------- End to End DetNet Service -------------->|
Figure 5: MPLS-Based Native DetNet
Figure 6 illustrates how an end to end MPLS-based DetNet service is
provided where the end systems are not able to send and receive
DetNet flows. In this example, the nodes labeled CE1 and CE2 could
be non-DetNet aware IP routers or hosts. Note that E1 and E2 are
edge nodes as they sit boundaries of the DetNet enabled domain.
IP IP
Non Service Transit Transit Service Non
DetNet |<-Tnl->| |<-Tnl->| DetNet
End | V 1 V V 2 V | End
System | +--------+ +--------+ +--------+ | System
+---+ | | E1 |=======| R2 |=======| E3 | | +---+
| |--------|._X_....|..DF1..|.__ ___.|..DF3..|...._X_.|------| |
|CE1| | | \ | | X | | / | | |CE2|
| | | | \_.|..DF2..|._/ \__.|..DF4..|._/ | | | |
+---+ | |=======| |=======| | +---+
+--------+ +--------+ +--------+
^ Edge Node Relay Node Edge Node^
| (T-PE) (S-PE) (T-PE) |
| |
<--IP-->| <----- IP Over DetNet MPLS ----> |<--IP-->
| |
|<------ End to End DetNet Service ------->|
Figure 6: MPLS-Based DetNet (non-MPLS End System)
Figure 7 illustrates how end to end DetNet service is provided where
the end systems are able to send and receive IP DetNet flows, e.g.,
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per [I-D.ietf-detnet-dp-sol-ip], and the MPLS nodes optionally
provide service protection. In this case R1 and R3 are T-PEs and R2
is an S-PE and the DetNet service is end-to-end.
DetNet DetNet
IP Service Transit Transit Service IP
DetNet |<-Tnl->| |<-Tnl->| DetNet
End | V 1 V V 2 V | End
System | +--------+ +--------+ +--------+ | System
+---+ | | R1 |=======| R2 |=======| R3 | | +---+
| |--------|._X_....|..DF1..|.__ ___.|..DF3..|...._X_.|------| |
|CE1| | | \ | | X | | / | | |CE2|
| | | | \_.|..DF2..|._/ \__.|..DF4..|._/ | | | |
+---+ | |=======| |=======| | +---+
^ +--------+ +--------+ +--------+ ^
| Relay Node Relay Node Relay Node |
| (T-PE) (S-PE) (T-PE) |
| |
|<-DN IP-> <------ DetNet MPLS ------> <-DN IP->|
| |
|<--------------- End to End DetNet Service -------------->|
Figure 7: DetNet IP over DetNet (DN) MPLS
An example MPLS DetNet network fragment and packet flow is
illustrated in Figure 8.
1 1.1 1.1 1.2.1 1.2.1 1.2.2
CE1----EN1--------R1-------R2-------R3--------EN2-----CE2
\ 1.2.1 / /
\1.2 /-----+ /
+------R4------------------------+
1.2.2
Figure 8: Example Packet flow in DetNet Enabled MPLS Network
In Figure 8 the numbers are used to identify the instance of a
packet. Packet 1 is the original packet, and packets 1.1, and 1.2
are two first generation copies of packet 1. Packet 1.2.1 is a
second generation copy of packet 1.2 etc. Note that these numbers
never appear in the packet, and are not to be confused with sequence
numbers, labels or any other identifier that appears in the packet.
They simply indicate the generation number of the original packet so
that its passage through the network fragment can be identified to
the reader.
Customer Equipment CE1 sends a packet into the DetNet enabled MPLS
network. This is packet (1). Edge Node EN1 encapsulates the packet
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as a DetNet Packet and sends it to Relay node R1 (packet 1.1). EN1
makes a copy of the packet (1.2), encapsulates it and sends this copy
to Relay node R4.
Note that along the MPLS path from EN1 to R1 there may be zero or
more LSRs which, for clarity, are not shown. The same is true for
any other path between two DetNet entities shown in Figure 8.
Relay node R4 has been configured to send one copy of the packet to
Relay Node R2 (packet 1.2.1) and one copy to Edge Node EN2 (packet
1.2.2).
R2 receives packet copy 1.2.1 before packet copy 1.1 arrives, and,
having been configured to perform packet elimination on this DetNet
flow, forwards packet 1.2.1 to Relay Node R3. Packet copy 1.1 is of
no further use and so is discarded by R2.
Edge Node EN2 receives packet copy 1.2.2 from R4 before it receives
packet copy 1.2.1 from R2 via relay Node R3. EN2 therefore strips
any DetNet encapsulation from packet copy 1.2.2 and forwards the
packet to CE2. When EN2 receives the later packet copy 1.2.1 this is
discarded.
The above is of course illustrative of many network scenarios that
can be configured. Between a pair of relay nodes there may be one or
more transport nodes that simply forward the DetNet traffic, but
these are omitted for clarity.
4.1. DetNet data plane encapsulation requirements
Two major groups of scenarios can be distinguished which require flow
identification during transport:
1. DetNet function related scenarios:
* Congestion protection and latency control: usage of allocated
resources (queuing, policing, shaping).
* Explicit routes: select/apply the flow specific path.
* Service protection: recognize DetNet compound and member flows
for replication an elimination.
2. OAM function related scenarios:
* troubleshooting (e.g., identify misbehaving flows, etc.)
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* recognize flow(s) for analytics (e.g., increase counters,
etc.)
* correlate events with flows (e.g., volume above threshold,
etc.)
* etc.
The DetNet data plane allows for the aggregation of DetNet flows,
e.g., via MPLS hierarchical LSPs, to improved scaling. When DetNet
flows are aggregated, transit nodes may have limited ability to
provide service on per-flow DetNet identifiers. Therefore,
identifying each individual DetNet flow on a transit node may not be
achieved in some network scenarios, but DetNet service can still be
assured in these scenarios through resource allocation and control.
A node operating on a DetNet flow in the Detnet layer, i.e. a node
processing a DetNet packet which has the S-label as top of stack uses
the local context associated with that S-label to determine what
local operation(s) are applied to that packet. The S-label has to be
unique on each edge and relay node, which is achieved by using a
label taken from the platform label space [RFC3031].
5. DetNet encapsulation
5.1. End-system specific considerations
Data-flows requiring DetNet service are generated and terminated on
end-systems. Encapsulation depends on application and its
preferences. In a DetNet (or even a TSN) domain the DN (TSN)
functions use at most two flow parameters, namely Flow-ID and
Sequence Number. However, an application may exchange further flow
related parameters (e.g., time-stamp), which are not considered by DN
functions.
Two types of end-systems are distinguished:
o L2 (Ethernet) end-system: application directly over L2.
o L3 (IP) end-system: application over L3.
In case of Ethernet end-systems the application data is encapsulated
directly in L2. From the DN domain perspective no upper layer
protocols are visible. The Data-flow uses only Ethernet tag(s) and
further flow specific parameters (if needed) are hidden inside the
protocol data unit (PDU).
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The IP end-system scenario is different. Data-flows are encapsulated
directly in L3 (i.e., IP) and the application may use further upper
layer protocols (e.g., Real-time Transport Protocol (RTP)). Many
valid combinations exist, and it may be application specific how the
IP header fields are used. Also, usage of further upper layer
protocols depends on application requirements (e.g., time-stamp).
See [I-D.ietf-detnet-dp-sol-ip] more details.
[Editor's note: IP solution document does not really detail
anything beyond 6-tuple.]
As a general rule, DetNet domains MUST be capable of forwarding any
Data-flows and the DetNet domain MUST NOT mandate the end-system
encapsulation format.
Furthermore, no application-level-proxy function is envisioned inside
the DetNet domain, so end-systems peer with end-systems using the
same application encapsulation format (see figure below):
o L2 end-systems peer with L2 end-systems and
o L3 end-systems peer with L3 end-systems.
+-----+
| X | +-----+
+-----+ | X |
| Eth | ________ +-----+
+-----+ _____ / \ | Eth |
\ / \__/ \___ +-----+
\ / \ /
0======== tunnel-1 ========0_
| \
\ |
0========= tunnel-2 =========0
/ \ __/ \
+-----+ \__ DetNet domain / \
| X | \ __ / +-----+
+-----+ \_______/ \_____/ | X |
| IP | +-----+
+-----+ | IP |
+-----+
Figure 9: End-systems and the DetNet domain
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5.2. DetNet domain specific considerations
From a connection type perspective, three scenarios are
distinguished:
1. Directly attached: end-system is directly connected to an edge
node.
2. Indirectly attached: end-system is behind a (L2-TSN / L3-DetNet)
sub-network.
3. DN integrated: end-system is part of the DetNet domain.
L3 end-systems may use any of these connection types, however L2 end-
systems may use only the first two (directly or indirectly attached).
DetNet domain MUST allow communication between any end-systems of the
same type (L2-L2, L3-L3), independent of their connection type and
DetNet capability. However directly attached and indirectly attached
end-systems have no knowledge about the DetNet domain and its
encapsulation format at all. See Figure 10 for L3 end-system
scenarios.
____+----+
+----+ _____ / | ES3|
| ES1|____ / \__/ +----+___
+----+ \ / \
+ |
____ \ _/
+----+ __/ \ +__ DetNet domain /
| ES2|____/ L2/L3 |___/ \ __ __/
+----+ \_______/ \_______/ \___/
Figure 10: Connection types of L3 end-systems
5.2.1. DetNet Layer Two Service
The simplest DetNet service is to provide tunneling for layer two,
where the connected hosts are in the same broadcast (BC) domain.
Forwarding over the DetNet domain is based on L2 (MAC) addresses
(i.e. dst-MAC), or on received interface [RFC3985]. In both cases
the L2 headers MUST either be kept, or provision must be made for
their reconstruction at egress from the DetNet domain.
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+------+
| X |
+------+ +------+
| X | | IP |
+------+ +------+
End-system | L2 | | L2 |
+-----+======+-+======+--+------+
DetNet tunnel | Shim |
+------+
| MPLS |
+------+
| L2 |
+------+
Examples:
+------+ +------+
| X | | X |
+------+ +------+ +------+
| X | | IP | | IP |
+------+ +------+ +------+
| L2 | | L2 | | L2 |
+-----+======+--+======+--+======+-----+
| d-CW | | d-CW | | d-CW |
+------+ +------+ +------+
| MPLS | | MPLS | | MPLS |
+------+ +------+ +------+
| L2 | | L2 | | UDP |
+------+ +------+ +------+
| IP |
+------+
| L2 |
+------+
Figure 11: Encapsulation format for DetNet Layer Two Service
As shown in Figure 11 both L2 and L3 end-systems can be served by
such a DetNet L2 encapsulation service. This encapsulation service
may be carried over MPLS natively Section 6.2, of over MPLS over IP
Section 11.
5.2.2. DetNet Routing Service (IP over MPLS)
IP traffic and IP DetNet flows, see [I-D.ietf-detnet-dp-sol-ip], can
be carried over a DetNet MPLS domain. In such cases, the IP headers
are modified per standard router behavior, e.g., TTL handling.
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Figure 12 shows the encapsulation of an IP flow over MPLS as well as
when MPLS is carried over an IP PSN, see Section 11.
+------+
| X |
+------+
End-system | IP |
+-----+======+--+------+
DetNet tunnel | Shim |
+------+
| MPLS |
+------+
| L2 |
+------+
Examples:
+------+ +------+
| X | | X |
+------+ +------+
| IP | | IP |
+-----+======+--+======+-----+
| d-CW | | d-CW |
+------+ +------+
| MPLS | | MPLS |
+------+ +------+
| L2 | | UDP |
+------+ +------+
| IP |
+------+
| L2 |
+------+
Figure 12: Encapsulation format for DetNet Routing in MPLS PSN for L3
end-systems
5.3. DetNet Inter-Working Function (DN-IWF)
5.3.1. Networks with multiple technology segments
There are networking scenarios, where the DetNet domain contains
multiple technology segments (IP, MPLS, ..) and all those segments
are under the same administrative control (see Figure 13).
Furthermore, DetNet nodes may be interconnected via TSN segments.
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An important aspect of DetNet network design is the placement of
DetNet functions across the domain. Designs based on segment-by-
segment optimization can provide only sub-optimal solutions. In
order to achieve global optimized Inter-Working Functions (DN-IWF)
can be placed at segment edge nodes, which stitch together DetNet
flows across connected segments.
DN-IWF may ensure that flow attributes are correlated across segment
edges. For example, there are two DetNet functions which require
Sequence Numbers: (1) PEF: removes duplications from flows and (2)
POF: ensures in-order-delivery of packet in a flow. Stitching flows
together and correlating attributes means for example that
replication of packets can happen in one segment and elimination of
duplicates in a different one.
______
____ / \__
____ / \__/ \___ ______
+----+ __/ +======+ +==+ \ +----+
|src |__/ Seg1 ) | | \ Seg3 \____| dst|
+----+ \_______+ \ Segment-2 | \+_____/ +----+
\======+_ _+===/
\ __ __/
\_______/ \___/
+------------+
+---------------E----+ | |
+----+ | | +----R---+ | +----+
|src |-------R +---+ | E----------+ dst|
+----+ | | E--------+ +----+
+-----------R |
+-----------------+
Figure 13: Optimal replication and elimination placement across
technology segments example
5.3.2. DN-IWF related considerations
The goal of DN-IWF is to (1) match and (2) translate segment specific
flow attributes. The DN-IWF ensures that segment specific attributes
comprise per domain unique attributes for the whole DetNet domain.
This characteristic can ensure that DetNet functions can be based on
per domain attributes and not per segment attributes.
The two DetNet specific attributes have the following
characteristics:
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o Flow-ID: it is same in all packets of a flow
o Sequence Number: it is different packet-by-packet
For the Flow-ID the DN-IWF can implement a static mapping. The
situation is more complicated for Sequence Number as it is different
packet-by-packet, so it may need more sophisticated translation
unless its format is exactly the same in the two technology segments.
In this later case the DN-IWF can simple copy the Sequence Number
field between the tunneling encapsulation of the two technology
segments.
In case of three technology segments (IP, MPLS and TSN) three DN-IWF
functions can be specified. In the rest of this section the focus is
on the (1) IP - MPLS network scenario. Note: the use-cases are out-
of-scope for (2) TSN - IP, (3) TSN - MPLS.
Simplest implementation of DN-IWF is provided if the flow attributes
have the same format. Such a common denominator of the tunnel
encapsulation format is the pseudowire encapsulation over both IP and
MPLS.
+--------+
| |
| X X |
| ____ |
| / \ |
| |
|/\/\/\/\|
Oops!
404 Not Found
Figure 14: FIGURE Placeholder PW over X
[Editor's note: Where is the text describing how 802.1 TSN Streams
are mapping to DetNet services/flows. i.e., EVPN+]
6. MPLS-based DetNet data plane solution
6.1. DetNet over MPLS Encapsulation Components
To carry DetNet over MPLS the following is required:
1. A method of identifying the MPLS payload type.
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2. A method of identifying the DetNet flow group to the processing
element.
3. A method of distinguishing DetNet OAM packets from DetNet data
packets.
4. A method of carrying the DetNet sequence number.
5. A suitable LSP to deliver the packet to the egress PE.
6. A method of carrying queuing and forwarding indication.
In this design an MPLS service label (the S-Label), similar to a
pseudowire (PW) label [RFC3985], is used to identify both the DetNet
flow identity and the payload MPLS payload type satisfying (1) and
(2) in the list above. OAM traffic discrimination happens through
the use of the Associated Channel method described in [RFC4385]. The
sequence number is carried in the DetNet Control word which carries
the Data/OAM discriminator. The LSP used to transport the DetNet
packet may be of any type (MPLS-LDP, MPLS-TE, MPLS-TP [RFC5921], or
MPLS-SR [I-D.ietf-spring-segment-routing-mpls]). The LSP (T-Label)
label and/or the S-Label may be used to indicate the queue processing
as well as the forwarding parameters.
To simplify implementation and to maximize interoperability two
sequence number sizes are supported: a 16 bit sequence number and a
28 bit sequence number. The 16 bit sequence number is needed to
support some types of legacy clients. The 28 bit sequence number is
used in situations where it is necessary ensure that in high speed
networks the sequence number space does not wrap whilst packets are
in flight. In addition it must be possible to send a packet with a
zero length sequence number, to support the case where sequence
numbers are not required by a particular DetNet flow.
Note that the concept of a zero length sequence number is not to be
confused with a sequence number of zero. For example, were the
sequence number size is 16 bits, the sequence will contain: 65535, 0,
1. In this case zero is an ordinary sequence number. Unlike
[RFC4448] a sequence number of zero does not indicate that no
sequence number is in use. Where sequence numbers are not in use,
and thus a zero length sequence number is in used, the sequence
number field in the packet is sent as zero. The DetNet packet
forwarder knows which of these cases applies through configuration
parameters associated with each specific DetNet flow.
Note that when the network consists only of DetNet enabled nodes with
no aggregation, Penultimate Hop Popping (PHP) means that the only
label in the label stack may be the S-label.
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6.2. MPLS data plane encapsulation
Figure 15 illustrates a DetNet data plane MPLS encapsulation. The
MPLS-based encapsulation of the DetNet flows is a good fit for the
Layer-2 interconnect deployment cases (see Figure 4). Furthermore,
end to end DetNet service i.e., native DetNet deployment (see
Figure 5) is also possible if DetNet end systems are capable of
initiating and termination MPLS encapsulated packets.
The MPLS-based DetNet data plane encapsulation consists of:
o DetNet control word (d-CW) containing sequencing information for
packet replication and duplicate elimination purposes, and the OAM
indicator. There MUST be a separate sequence number space for
each DetNet flow.
o DetNet service Label (S-label) that identifies a DetNet flow to
the peer node that is to process it. The S-Label is allocated
from the platform label space [RFC3031].
o Zero or more MPLS transport LSP label(s) (T-label) used to direct
the packet along the label switched path (LSP) to the next peer
node along the path. When Penultimate Hop Popping is in use there
may be no label T-label in the protocol stack on the final hop.
o The necessary data-link encapsulation is then applied prior to
transmission over the physical media.
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DetNet MPLS-based encapsulation
+---------------------------------+
| |
| DetNet Flow |
| Payload Packet |
| |
+---------------------------------+ <--\
| DetNet Control Word | |
+---------------------------------+ +--> DetNet data plane
| S-Label | | MPLS encapsulation
+---------------------------------+ <--/
| T-Label(s) |
+---------------------------------+
| Data-Link |
+---------------------------------+
| Physical |
+---------------------------------+
Figure 15: Encapsulation of a DetNet flow in an MPLS(-TP) PSN
6.3. DetNet control word
A DetNet control word (d-CW) conforms to the Generic PW MPLS Control
Word (PWMCW) defined in [RFC4385] and is illustrated in Figure 16.
The upper nibble of the d-CW MUST be set to zero (0). Two sequence
number sizes are supported: 16 bits and 28 bits. The sequence number
size in use for the d-CW associated with a DetNet flow (S-Label) is
configured either by a control plane or manually for each DetNet
flow. The sequence number is aligned to the right (least significant
bits) and unused bits MUST be set to zero (0). Each DetNet flow MUST
have its own sequence number counter. The sequence number is
incremented by one for each new packet.
As discussed in Section 6, zero is an ordinary sequence number with
no special meaning. Also as discussed therein, where no sequence
number is used by a particular DetNet flow, the sequence number field
in the d-CW is set to zero.
The d-CW MUST always be present in a packet. In a case where the
sequence number is not used (e.g., for DetNet-t-flows) a zero length
sequence number is used and the sequence number MUST be set to zero
(0).
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0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0 0 0 0| Sequence Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 16: DetNet Control Word
6.4. Flow Identification
DetNet flow identification at a DetNet service layer is realized by
an S-label. The S-label is allocated from the platform label space
[RFC3031] which means that the DetNet flow is correctly identified
and matched to the flow parameters, including the flow history,
regardless of which input interface the packet arrives on. The
S-label MUST be at the bottom label of the label stack for a DetNet-
s- or DetNet-st-flow and MUST precede the d-CW.
The S-label for a specific DetNet flow is unique to that DetNet flow
on a specific node, but is not required to be identical with the
S-label for that DetNet flow in any other node within the DetNet
domain. Thus the S-label can only be used to identify the DetNet
flow at the intended receiving node.
6.5. Indication of the DetNet Payload Type
The only nodes that needs to know the payload type of a flow are the
DetNet ingress node and the DetNet egress nodes. The ingress node
has to know how to process the packet it receives from the ingress AC
or IP flow, and the egress edge node has to know how to prepare the
packet for transmission to the next hop.
On ingress a DetNet edge node has to classify the packets into those
that are for transmission as Detnet packets and those that are for
transmission as "normal" packets at one of more lower priorities.
The packet type is indicated to the egress edge node through the
value of the S-label. Thus, when the egress edge node looks up the
S-label one of the parameters returned is the packet type which in
turn tells the egress edge node how to prepare the packet for
transmission to a next hop.
The consequence of this approach is that if multiple packet
encapsulations are processed on a node pair, each encapsulation will
need its own S-Label. That is not generally a problems, since it is
anticipated that only one encapsulation type will be present for each
DetNet flow. Of course, if for some reason the multiple
encapsulations are needed to support a single DetNet service,
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multiple S-labels will be required for that service. Note that in
the unlikely case that Ipv4 and IPv6 will map to the same DetNet
flow, different S-labels will be needed to differentiate between the
versions of IP.
6.6. OAM Indication
OAM follows the procedures set out in [RFC5085] with the restriction
that only Virtual Circuit Connectivity Verification (VCCV) type 1 is
supported.
As shown in Figure 3 of [RFC5085] when the first nibble of the d-CW
is 0x0 the payload following the d-CW is normal user data. However,
when the first nibble of the d-CW is 0X1, the payload that follows
the d-DW is an OAM payload with the OAM type indicated by the value
in the d-CW Channel Type field.
The reader is referred to [RFC5085] for a more detailed description
of the Associated Channel mechanism, and to the DetNet work on OAM
for more information DetNet OAM.
6.7. Flow Aggregation
1. Aggregate at the LSP (Transport)
2. Aggregating DetNet flows as a new DetNet flow
3. Simple Aggregation at the DetNet layer
A further method of using SR to perform aggregation is for further
study.
The resource control and management aspects of aggregation (including
the queuing/shaping/ policing implications) will be covered in other
documents.
The ability to aggregate individual flows, and their associated
resource control, into a larger aggregate is an important technique
for improving scaling of control in the data, management and control
planes. The DetNet data plane allows for the aggregation of DetNet
flows, to improved scaling. There are three methods of introducing
flow aggregation:
The following review comments were received when this section was
committed to github.
General comment: We should points to the major issue of aggregation,
namely the Seq.Num related problem. The aggregated flows have their
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own Seq.Num and those are independent. We should consider to group
the aggregation techniques as per their impact on what DetNet
functions they allow on a DetNet flow. (E.g., aggregation without
new Aggregate.Seq.Num would prohibit usage of FR, EF and in-order-
delivery function on the aggregate flow).
SR based aggregation can be treated as a form of H-LSP aggregation.
Should we differentiate them? What are the differences?
What are the issues when aggregating of different payload types?
Should we add an editor note on this?
Simple-aggregation-at-the-detnet-layer: is this not the same as
H-LSP? The A-label can be treated just as an additional T-label.
End of review comment.
6.7.1. Aggregation at the LSP
DetNet flows transported via MPLS can leverage MPLS-TE?s existing
support for hierarchical LSPs (H-LSPs), see [RFC4206]. H-LSPs are
typically used to aggregate control and resources, they may also be
used to provide OAM or protection for the aggregated LSPs. Arbitrary
levels of aggregation naturally falls out of the definition for
hierarchy and the MPLS label stack [RFC3032]. DetNet nodes which
support aggregation (LSP hierarchy) map one or more LSPs (labels)
into and from an H-LSP. Both carried LSPs and H-LSPs may or may not
use the TC field, i.e., L-LSPs or E-LSPs. Such nodes will need to
ensure that traffic from aggregated LSPs are placed (shaped/policed/
enqueued) onto the H-LSPs in a fashion that ensures the required
DetNet service is preserved.
Additional details of the traffic control capabilities needed at a
DetNet-aware node may be covered in the new service descriptions
mentioned above or in separate future documents. Management and
control plane mechanisms will also need to ensure that the service
required on the aggregate flow (H-LSP or DSCP) are provided, which
may include the discarding or remarking mentioned in the previous
sections.
6.7.2. Aggregating DetNet flows as a new DetNet flow
An aggregate can be built by layering DetNet flows as shown below:
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+---------------------------------+
| |
| DetNet Flow |
| Payload Packet |
| |
+---------------------------------+ <--\
| DetNet Control Word | |
+=================================+ |
| S-Label | |
+---------------------------------+ +----DetNet data plane
| DetNet Control Word | | MPLS encapsulation
+=================================+ |
| A-Label | |
+---------------------------------+ <--/
| T-Label(s) |
+---------------------------------+
| Data-Link |
+---------------------------------+
| Physical |
+---------------------------------+
Both the Aggregation (A) label and the S-label have their MPLS S bit
set indicating bottom of stack, and the d-CW allows the PREOF to
work.
It is a property of the A-label that what follows is d-CW followed by
an S-label. A relay node processing the A-label would not know the
underlying payload type. This would only be known to a node that was
a peer of the node imposing the S-label. However there is no real
need for it to know the payload type during aggregation processing.
6.7.3. Simple Aggregation at the DetNet layer
Another approach would be not to include a d-CW for the aggregated
flow. This would be functionally similar to aggregation at the
transport layer using H-LSPs, but would confine knowledge of the
aggregation to the DetNet layer. Such an approach shares the
disadvantage that PREOF operations would not be possible. OAM
operation in this mode is for further study.
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+---------------------------------+
| |
| DetNet Flow |
| Payload Packet |
| |
+---------------------------------+ <--\
| DetNet Control Word | |
+=================================+ |
| S-Label | +----DetNet data plane
+---------------------------------+ | MPLS encapsulation
| A-Label | |
+---------------------------------+ <--/
| T-Label(s) |
+---------------------------------+
| Data-Link |
+---------------------------------+
| Physical |
+---------------------------------+
6.8. Service Layer Considerations
The edge and relay node internal procedures related to PREOF are
implementation specific. The order of a packet elimination or
replication is out of scope in this specification. However, care
should be taken that the replication function does not actually
loopback packets as "replicas". Looped back packets include
artificial delay when the node that originally initiated the packet
receives it again. Also, looped back packets may make the network
condition to look healthier than it actually is (in some cases link
failures are not reflected properly because looped back packets make
the situation appear better than it actually is).
It is important that the DetNet layer is configured such that a
DetNet node never receives its own replicated packets. If it were to
receive such packets the replication function would make the loop
more destructive of bandwidth than a conventional unicast loop.
Ultimately the TTL in the S-Label will cause the packet to die during
a transient, but given the sensitivity of applications to packet
latency the impact on the DetNet application would be severe.
6.8.1. Edge node processing
An edge node is resposable for matching ingress packets to the
service they require and encapsulating them accordingly.An edge node
may participate in the packet replication and duplication
elimination.
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The DetNet-aware forwarder selects the egress DetNet member flow
segment based on the flow identification. The mapping of ingress
DetNet member flow segment to egress DetNet member flow segment may
be statically or dynamically configured. Additionally the DetNet-
aware forwarder does duplicate frame elimination based on the flow
identification and the sequence number combination. The packet
replication is also done within the DetNet-aware forwarder. During
elimination and the replication process the sequence number of the
DetNet member flow MUST be preserved and copied to the egress DetNet
member flow.
The internal design of a relay node is out of scope of this document.
However the reader's attention is drawn to the need to make any PREOF
state available to the packet processor(s) dealing with packets to
which the PREOF functions must be applied, and to maintain that state
is such as way that it is available to the packet processor operation
on the next packet in the DetNet flow (which may be a duplicate, a
late packet, or the next packet in sequence.
[Editor's note: I think the rest of this section belongs in a new
"802.1 TSN (island Interconnect) over MPLS DetNet" section.]
This may be done in the DetNet layer, or where the native service
processing (NSP) [RFC3985] is IEEE 802.1CB [IEEE8021CB] capable, the
packet replication and duplicate elimination MAY entirely be done in
the NSP, bypassing the DetNet flow encapsulation and logic entirely.
This enables operating over unmodified implementations and
deployments. The NSP approach works only between edge nodes and
cannot make use of relay nodes.
The NSP approach is useful end to end tunnel and for for "island
interconnect" scenarios. However, when there is a need to do PREOF
in a middle of the network, such plain edge to edge operation is not
sufficient.
The extended forwarder MAY copy the sequencing information from the
native DetNet packet into the DetNet sequence number field and vice
versa. If there is no existing sequencing information available in
the native packet or the forwarder chose not to copy it from the
native packet, then the extended forwarder MUST maintain a sequence
number counter for each DetNet flow (indexed by the DetNet flow
identification).
6.8.2. Relay node processing
A DetNet Relay node operates in the DetNet transport layer . This
processing is done within an extended forwarder function. Whether an
ingress DetNet member flow receives DetNet specific processing
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depends on how the forwarding is programmed. Some relay nodes may be
DetNet service aware, while others may be unmodified LSRs that only
understand how to swicth MPLS-TE LSPs.
It is also possible to treat the relay node as a transit node, see
Section 6.9.3. Again, this is entirely up to how the forwarding has
been programmed.
6.9. Other DetNet data plane considerations
6.9.1. Class of Service
[Editor's note: this section needs to updated to discuss how DetNet
service is mapped to E- and L-LSPs. Perhaps this gets merged with
the aggregation section or dropped?]
Class and quality of service, i.e., CoS and QoS, are terms that are
often used interchangeably and confused with each other. In the
context of DetNet, CoS is used to refer to mechanisms that provide
traffic forwarding treatment based on aggregate group basis and QoS
is used to refer to mechanisms that provide traffic forwarding
treatment based on a specific DetNet flow basis. Examples of
existing network level CoS mechanisms include DiffServ which is
enabled by IP header differentiated services code point (DSCP) field
[RFC2474] and MPLS label traffic class field [RFC5462], and at Layer-
2, by IEEE 802.1p priority code point (PCP).
CoS for DetNet flows carried in PWs and MPLS is provided using the
existing MPLS Differentiated Services (DiffServ) architecture
[RFC3270]. Both E-LSP and L-LSP MPLS DiffServ modes MAY be used to
support DetNet flows. The Traffic Class field (formerly the EXP
field) of an MPLS label follows the definition of [RFC5462] and
[RFC3270]. The Uniform, Pipe, and Short Pipe DiffServ tunneling and
TTL processing models are described in [RFC3270] and [RFC3443] and
MAY be used for MPLS LSPs supporting DetNet flows. MPLS ECN MAY also
be used as defined in ECN [RFC5129] and updated by [RFC5462].
CoS for DetNet flows carried in IPv6 is provided using the standard
differentiated services code point (DSCP) field [RFC2474] and related
mechanisms. The 2-bit explicit congestion notification (ECN)
[RFC3168] field MAY also be used.
One additional consideration for DetNet nodes which support CoS
services is that they MUST ensure that the CoS service classes do not
impact the congestion protection and latency control mechanisms used
to provide DetNet QoS. This requirement is similar to requirement
for MPLS LSRs to that CoS LSPs do not impact the resources allocated
to TE LSPs via [RFC3473].
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6.9.2. Quality of Service
Quality of Service (QoS) mechanisms for flow specific traffic
treatment typically includes a guarantee/agreement for the service,
and allocation of resources to support the service. Example QoS
mechanisms include discrete resource allocation, admission control,
flow identification and isolation, and sometimes path control,
traffic protection, shaping, policing and remarking. Example
protocols that support QoS control include Resource ReSerVation
Protocol (RSVP) [RFC2205] (RSVP) and RSVP-TE [RFC3209] and [RFC3473].
The existing MPLS mechanisms defined to support CoS [RFC3270] can
also be used to reserve resources for specific traffic classes.
In addition to explicit routes, and packet replication and
elimination, described in Section 6 above, DetNet provides zero
congestion loss and bounded latency and jitter. As described in
[I-D.ietf-detnet-architecture], there are different mechanisms that
maybe used separately or in combination to deliver a zero congestion
loss service. These mechanisms are provided by the either the MPLS
or IP layers, and may be combined with the mechanisms defined by the
underlying network layer such as 802.1TSN.
A baseline set of QoS capabilities for DetNet flows carried in PWs
and MPLS can provided by MPLS with Traffic Engineering (MPLS-TE)
[RFC3209] and [RFC3473]. TE LSPs can also support explicit routes
(path pinning). Current service definitions for packet TE LSPs can
be found in "Specification of the Controlled Load Quality of
Service", [RFC2211], "Specification of Guaranteed Quality of
Service", [RFC2212], and "Ethernet Traffic Parameters", [RFC6003].
Additional service definitions are expected in future documents to
support the full range of DetNet services. In all cases, the
existing label-based marking mechanisms defined for TE-LSPs and even
E-LSPs are use to support the identification of flows requiring
DetNet QoS.
Packets that are marked with a DetNet Class of Service value, but
that have not been the subject of a completed reservation, can
disrupt the QoS offered to properly reserved DetNet flows by using
resources allocated to the reserved flows. Therefore, the network
nodes of a DetNet network:
o MUST defend the DetNet QoS by discarding or remarking (to a non-
DetNet CoS) packets received that are not the subject of a
completed reservation.
o MUST NOT use a DetNet reserved resource, e.g. a queue or shaper
reserved for DetNet flows, for any packet that does not carry a
DetNet Class of Service marker.
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6.9.3. Cross-DetNet flow resource aggregation
[Editor's NOTE: keep and extend this section.]
The ability to aggregate individual flows, and their associated
resource control, into a larger aggregate is an important technique
for improving scaling of control in the data, management and control
planes. This document identifies the traffic identification related
aspects of aggregation of DetNet flows. The resource control and
management aspects of aggregation (including the queuing/shaping/
policing implications) will be covered in other documents. The data
plane implications of aggregation are independent for PW/MPLS and IP
encapsulated DetNet flows.
DetNet flows transported via MPLS can leverage MPLS-TE's existing
support for hierarchical LSPs (H-LSPs), see [RFC4206]. H-LSPs are
typically used to aggregate control and resources, they may also be
used to provide OAM or protection for the aggregated LSPs. Arbitrary
levels of aggregation naturally falls out of the definition for
hierarchy and the MPLS label stack [RFC3032]. DetNet nodes which
support aggregation (LSP hierarchy) map one or more LSPs (labels)
into and from an H-LSP. Both carried LSPs and H-LSPs may or may not
use the TC field, i.e., L-LSPs or E-LSPs. Such nodes will need to
ensure that traffic from aggregated LSPs are placed (shaped/policed/
enqueued) onto the H-LSPs in a fashion that ensures the required
DetNet service is preserved.
DetNet flows transported via IP have more limited aggregation
options, due to the available traffic flow identification fields of
the IP solution. One available approach is to manage the resources
associated with a DSCP identified traffic class and to map (remark)
individually controlled DetNet flows onto that traffic class. This
approach also requires that nodes support aggregation ensure that
traffic from aggregated LSPs are placed (shaped/policed/enqueued) in
a fashion that ensures the required DetNet service is preserved.
In both the MPLS and IP cases, additional details of the traffic
control capabilities needed at a DetNet-aware node may be covered in
the new service descriptions mentioned above or in separate future
documents. Management and control plane mechanisms will also need to
ensure that the service required on the aggregate flow (H-LSP or
DSCP) are provided, which may include the discarding or remarking
mentioned in the previous sections.
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6.9.4. Layer 2 addressing and QoS Considerations
[Editor's NOTE: review and simplify this section.]
The Time-Sensitive Networking (TSN) Task Group of the IEEE 802.1
Working Group have defined (and are defining) a number of amendments
to IEEE 802.1Q [IEEE8021Q] that provide zero congestion loss and
bounded latency in bridged networks. IEEE 802.1CB [IEEE8021CB]
defines packet replication and elimination functions that should
prove both compatible with and useful to, DetNet networks.
As is the case for DetNet, a Layer 2 network node such as a bridge
may need to identify the specific DetNet flow to which a packet
belongs in order to provide the TSN/DetNet QoS for that packet. It
also will likely need a CoS marking, such as the priority field of an
IEEE Std 802.1Q VLAN tag, to give the packet proper service.
Although the flow identification methods described in IEEE 802.1CB
[IEEE8021CB] are flexible, and in fact, include IP 5-tuple
identification methods, the baseline TSN standards assume that every
Ethernet frame belonging to a TSN stream (i.e. DetNet flow) carries
a multicast destination MAC address that is unique to that flow
within the bridged network over which it is carried. Furthermore,
IEEE 802.1CB [IEEE8021CB] describes three methods by which a packet
sequence number can be encoded in an Ethernet frame.
Ensuring that the proper Ethernet VLAN tag priority and destination
MAC address are used on a DetNet/TSN packet may require further
clarification of the customary L2/L3 transformations carried out by
routers and edge label switches. Edge nodes may also have to move
sequence number fields among Layer 2, PW, and IPv6 encapsulations.
6.9.5. Time Synchronization
[Editor's Note: A detailed discussion of time synchronization is
outside the scope of this document, and the production of a
specialist text discussing this topic is encouraged. This section
will be updated/removed if such a document is available before
publication of this text.]
Time synchronization is important both from the perspective of
operating the DetNet network itself and from the perspective of
transferring time across the network between client applications.
Some clients may be able to use the DetNet as their provider of time
and frequency, others may require the DetNet to transfer time between
a client clock source and a client clock user.
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The reader's attention is drawn to [RFC8169] which describes a method
of recording the packet queuing time in an MPLS LSR on a packet by
per packet basis and forwarding this information to the egress edge
system. This allows compensation for any variable packet queuing
delay to be applied at the packet receiver. The mechanism described
in [RFC8169] may have wider application than basic time transfer in a
DetNet.
A more detailed discussion of time synchronization is outside the
scope of this document.
7. Management and control considerations
[Editor's note: This section needs to be different for MPLS and IP
solutions. Most solutions are technology dependant. Currently most
text in this section is just a draft and may have bits that are
already moved to other places/documents.]
While management plane and control planes are traditionally
considered separately, from the Data Plane perspective there is no
practical difference based on the origin of flow provisioning
information. This document therefore does not distinguish between
information provided by a control plane protocol, e.g., RSVP-TE
[RFC3209] and [RFC3473], or by a network management mechanisms, e.g.,
RestConf [RFC8040] and YANG [RFC7950].
[Editor's note: This section is a work in progress. discuss here
what kind of enhancements are needed for DetNet and specifically for
PREOF and DetNet zero congest loss and latency control. Need to
cover both traffic control (queuing) and connection control (control
plane).]
7.1. MPLS-based data plane
7.1.1. S-Label assignment and distribution
[Editor's note: Outdated and needs more work.]
The DetNet S-Label distribution follows the same mechanisms specified
for XYZ . The details of the control plane protocol solution required
for the label distribution and the management of the label number
space are out of scope of this document.
7.1.2. Explicit routes
It is necessary to consider explicit routes both at the DetNet layer
and in the MPLS layer. In the DetNet layer the explicit route
consists of the set of Relay Nodes that the DetNet flow must
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traverse. In the MPLS layer the explicit route consists of the set
of LSRs, links, and possibly link bundle members and queues that the
DetNet packets of a flow must traverse between nodes in the DetNet
layer (i.e. between a specific Edge Node and the next hop Relay Node,
between specific Relay Nodes, and between a specific Relay node and
the egress Edge Node. This detailed steering is needed to ensure
that packets are routed through the resources that have been reserved
for them, and hence provide the DetNet application with the required
performance.
Whether configuring, calculating and instantiating this is a multi-
stage process, or a single stage process is out of scope of this
document.
The one method of explicitly setting up the explicit path at the
DetNet layer is through the use of the management controller.
[Editor's note: a method of setting up a graph through the DetNet
Nodes using the IGP has been proposed. A reference is needed to
e.g., RFC 7813 IS-IS Path Control and Reservation.]
There are a number of approaches that can be taken to provide
explicit routes/paths in the MPLS layer:
o The path can be explicitly set up by the management controller
calculating the path and explicitly configuring each node along
that path.
o The LSP can be set up using RSVP-TE. Such an approach confines
the packet to the explicit path.
o The path can be implemented using segment routing.
Where the DetNet traffic is carried over IP Section 11 explicit paths
may need to be provided in the IP layer. This is for further study.
7.2. Packet replication and elimination
[Editor's note: Outdated and at the functional level technology
independent.. but needs more work.]
The control plane protocol solution required for managing the PREOF
processing is outside the scope of this document.
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7.3. Congestion protection and latency control
[Editor's note: TBD]
7.4. Bidirectional traffic
[Editor's NOTE: this section needs to be updated to have its scope
limited to management and control.]
Some DetNet applications generate bidirectional traffic. Using MPLS
definitions [RFC5654] there are associated bidirectional flows, and
co-routed bidirectional flows. MPLS defines a point-to-point
associated bidirectional LSP as consisting of two unidirectional
point-to-point LSPs, one from A to B and the other from B to A, which
are regarded as providing a single logical bidirectional transport
path. This would be analogous of standard IP routing, or PWs running
over two reciprocal unidirection LSPs. MPLS defines a point-to-point
co-routed bidirectional LSP as an associated bidirectional LSP which
satisfies the additional constraint that its two unidirectional
component LSPs follow the same path (in terms of both nodes and
links) in both directions. An important property of co-routed
bidirectional LSPs is that their unidirectional component LSPs share
fate. In both types of bidirectional LSPs, resource allocations may
differ in each direction. The concepts of associated bidirectional
flows and co-routed bidirectional flows can be applied to DetNet
flows as well whether IPv6 or MPLS is used.
While the IPv6 and MPLS data planes must support bidirectional DetNet
flows, there are no special bidirectional features with respect to
the data plane other than need for the two directions take the same
paths. Fate sharing and associated vs co-routed bidirectional flows
can be managed at the control level. Note, that there is no stated
requirement for bidirectional DetNet flows to be supported using the
same IPv6 Flow Labels or MPLS Labels in each direction. Control
mechanisms will need to support such bidirectional flows for both
IPv6 and MPLS, but such mechanisms are out of scope of this document.
An example control plane solution for MPLS can be found in [RFC7551].
7.5. Flow aggregation control
[TBD]
8. DetNet IP Operation over DetNet MPLS Service
[Editor's note: this is a place holder section. A standalone section
on operation of IP flows over DetNet MPLS data plane. Includes
RFC2119 Language.]
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9. IEEE 802.1 TSN Interconnection over DetNet MPLS Service
[Editor's note: this is a place holder section. A standalone section
on TSN "island" interconnect over DetNet". Includes RFC2119
Language.]
10. DetNet MPLS Transport Layer Operation over IEEE 802.1 TSN Sub-
Networks
[Editor's note: this is a place holder section. A standalone section
on MPLS over IEEE 802.1 TSN. Includes RFC2119 Language.]
11. DetNet MPLS Transport Layer Operation over IP DetNet PSNs
This section specifies the DetNet encapsulation over an IP transport
network. The approach is modeled on the operation of MPLS and
PseudoWires (PW) over an IP Packet Switched Network (PSN)
[RFC3985][RFC4385][RFC7510]. It is also based on the MPLS data plane
encapsulation described in Section 6.2.
To carry DetNet with full functionality at the DetNet layer over an
IP transport network, the following components are required (these
are a subset of the requirements for MPLS encapsulation listed in
Section 6.1):
1. A method of identifying the DetNet flow group to the processing
element.
2. A method of carrying the DetNet sequence number.
3. A method of distinguishing DetNet OAM packets from DetNet data
packets.
4. A method of carrying queuing and forwarding indication.
These requirements are satisfied by the DetNet over MPLS
Encapsulation described in Section 6.2.
To simplify operations and implementations, rather than inventing a
new encapsulation, the IP encapsulation takes advantage of the MPLS
encapsulation. By using the specification of MPLS over UDP and IP in
[RFC7510], the T-Label(s) shown in Figure 15 in Section 6.2 can be
replaced by UDP and IP, resulting in the following encapsulation:
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+---------------------------------+
| |
| DetNet Flow |
| Payload Packet |
| |
+---------------------------------+ <--\
| DetNet Control Word | |
+---------------------------------+ +--> DetNet data plane
| S-Label | | MPLS encapsulation
+---------------------------------+ <--/
| UDP Header |
+---------------------------------+
| IP Header |
+---------------------------------+
| Data-Link |
+---------------------------------+
| Physical |
+---------------------------------+
Figure 17: IP Encapsulation of DetNet
Where the UDP header is used as defined in Section 3 of [RFC7510].
As in Section 6.2, the S-Label is used to identify a DetNet flow to
the peer node that processes it, in this case the node addressed by
the IP Header in Figure 17. The S-Label is allocated from the
receiving node?s platform label space [RFC3031].
In ingress Edge Nodes, the encapsulation in Figure 17 will be imposed
on Detnet Flow Payload Packets as received from DetNet End Systems,
and the encapsulation will be removed in egress Edge Nodes as they
transmit the Payload Packets to the End Systems.
Note that this encapsulation works equally well with IPv4 and IPv6.
This encapsulation can also be used in conjunction with segment
routing as specified in [I-D.ietf-spring-segment-routing-mpls]. In
this case, the T-Label(s) in Figure 17 should be retained, and at
each hop, the top T-label is popped and mapped to a corresponding
UDP/IP tunnel, resulting in the following encapsulation:
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+---------------------------------+
| |
| DetNet Flow |
| Payload Packet |
| |
+---------------------------------+ <--\
| DetNet Control Word | |
+---------------------------------+ +--> DetNet data plane
| S-Label | | MPLS encapsulation
+---------------------------------+ <--/
| T-Label(s) |
+---------------------------------+
| UDP Header |
+---------------------------------+
| IP Header |
+---------------------------------+
| Data-Link |
+---------------------------------+
| Physical |
+---------------------------------+
Figure 18: IP Encapsulation of DetNet with MPLS-SR
Again, the UDP header is used as defined in Section 3 of [RFC7510].
Note that if required in both the case of IP Encapsulation of DetNet
Figure 17, and of IP Encapsulation of DetNet with MPLS-SR Figure 18,
it is possible to omit the UDP header if required. Operation of MPLS
directly over IP is described in [RFC4023]. In this case DetNet
Service can be provided on a per IP flow basis as described in
[I-D.ietf-detnet-dp-sol-ip].
12. Security considerations
The security considerations of DetNet in general are discussed in
[I-D.ietf-detnet-architecture] and [I-D.sdt-detnet-security]. Other
security considerations will be added in a future version of this
draft.
13. IANA considerations
This document makes no IANA requests.
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14. Contributors
RFC7322 limits the number of authors listed on the front page of a
draft to a maximum of 5, far fewer than the 20 individuals below who
made important contributions to this draft. The editor wishes to
thank and acknowledge each of the following authors for contributing
text to this draft. See also Section 15.
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Loa Andersson
Huawei
Email: loa@pi.nu
Yuanlong Jiang
Huawei
Email: jiangyuanlong@huawei.com
Norman Finn
Huawei
3101 Rio Way
Spring Valley, CA 91977
USA
Email: norman.finn@mail01.huawei.com
Janos Farkas
Ericsson
Magyar Tudosok krt. 11.
Budapest 1117
Hungary
Email: janos.farkas@ericsson.com
Carlos J. Bernardos
Universidad Carlos III de Madrid
Av. Universidad, 30
Leganes, Madrid 28911
Spain
Email: cjbc@it.uc3m.es
Tal Mizrahi
Marvell
6 Hamada st.
Yokneam
Israel
Email: talmi@marvell.com
Lou Berger
LabN Consulting, L.L.C.
Email: lberger@labn.net
Stewart Bryant
Huawei Technologies
Email: stewart.bryant@gmail.com
Mach Chen
Huawei Technologies
Email: mach.chen@huawei.com
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15. Acknowledgements
The author(s) ACK and NACK.
The following people were part of the DetNet Data Plane Solution
Design Team:
Jouni Korhonen
Janos Farkas
Norman Finn
Balazs Varga
Loa Andersson
Tal Mizrahi
David Mozes
Yuanlong Jiang
Carlos J. Bernardos
The DetNet chairs serving during the DetNet Data Plane Solution
Design Team:
Lou Berger
Pat Thaler
Thanks for Stewart Bryant for his extensive review of the previous
versions of the document.
16. References
16.1. Normative references
[I-D.ietf-spring-segment-routing-mpls]
Bashandy, A., Filsfils, C., Previdi, S., Decraene, B.,
Litkowski, S., and R. Shakir, "Segment Routing with MPLS
data plane", draft-ietf-spring-segment-routing-mpls-14
(work in progress), June 2018.
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[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.
[RFC2211] Wroclawski, J., "Specification of the Controlled-Load
Network Element Service", RFC 2211, DOI 10.17487/RFC2211,
September 1997, <https://www.rfc-editor.org/info/rfc2211>.
[RFC2212] Shenker, S., Partridge, C., and R. Guerin, "Specification
of Guaranteed Quality of Service", RFC 2212,
DOI 10.17487/RFC2212, September 1997,
<https://www.rfc-editor.org/info/rfc2212>.
[RFC2474] Nichols, K., Blake, S., Baker, F., and D. Black,
"Definition of the Differentiated Services Field (DS
Field) in the IPv4 and IPv6 Headers", RFC 2474,
DOI 10.17487/RFC2474, December 1998,
<https://www.rfc-editor.org/info/rfc2474>.
[RFC3031] Rosen, E., Viswanathan, A., and R. Callon, "Multiprotocol
Label Switching Architecture", RFC 3031,
DOI 10.17487/RFC3031, January 2001,
<https://www.rfc-editor.org/info/rfc3031>.
[RFC3032] Rosen, E., Tappan, D., Fedorkow, G., Rekhter, Y.,
Farinacci, D., Li, T., and A. Conta, "MPLS Label Stack
Encoding", RFC 3032, DOI 10.17487/RFC3032, January 2001,
<https://www.rfc-editor.org/info/rfc3032>.
[RFC3168] Ramakrishnan, K., Floyd, S., and D. Black, "The Addition
of Explicit Congestion Notification (ECN) to IP",
RFC 3168, DOI 10.17487/RFC3168, September 2001,
<https://www.rfc-editor.org/info/rfc3168>.
[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>.
[RFC3270] Le Faucheur, F., Wu, L., Davie, B., Davari, S., Vaananen,
P., Krishnan, R., Cheval, P., and J. Heinanen, "Multi-
Protocol Label Switching (MPLS) Support of Differentiated
Services", RFC 3270, DOI 10.17487/RFC3270, May 2002,
<https://www.rfc-editor.org/info/rfc3270>.
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[RFC3443] Agarwal, P. and B. Akyol, "Time To Live (TTL) Processing
in Multi-Protocol Label Switching (MPLS) Networks",
RFC 3443, DOI 10.17487/RFC3443, January 2003,
<https://www.rfc-editor.org/info/rfc3443>.
[RFC3473] Berger, L., Ed., "Generalized Multi-Protocol Label
Switching (GMPLS) Signaling Resource ReserVation Protocol-
Traffic Engineering (RSVP-TE) Extensions", RFC 3473,
DOI 10.17487/RFC3473, January 2003,
<https://www.rfc-editor.org/info/rfc3473>.
[RFC4023] Worster, T., Rekhter, Y., and E. Rosen, Ed.,
"Encapsulating MPLS in IP or Generic Routing Encapsulation
(GRE)", RFC 4023, DOI 10.17487/RFC4023, March 2005,
<https://www.rfc-editor.org/info/rfc4023>.
[RFC4206] Kompella, K. and Y. Rekhter, "Label Switched Paths (LSP)
Hierarchy with Generalized Multi-Protocol Label Switching
(GMPLS) Traffic Engineering (TE)", RFC 4206,
DOI 10.17487/RFC4206, October 2005,
<https://www.rfc-editor.org/info/rfc4206>.
[RFC4385] Bryant, S., Swallow, G., Martini, L., and D. McPherson,
"Pseudowire Emulation Edge-to-Edge (PWE3) Control Word for
Use over an MPLS PSN", RFC 4385, DOI 10.17487/RFC4385,
February 2006, <https://www.rfc-editor.org/info/rfc4385>.
[RFC5085] Nadeau, T., Ed. and C. Pignataro, Ed., "Pseudowire Virtual
Circuit Connectivity Verification (VCCV): A Control
Channel for Pseudowires", RFC 5085, DOI 10.17487/RFC5085,
December 2007, <https://www.rfc-editor.org/info/rfc5085>.
[RFC5129] Davie, B., Briscoe, B., and J. Tay, "Explicit Congestion
Marking in MPLS", RFC 5129, DOI 10.17487/RFC5129, January
2008, <https://www.rfc-editor.org/info/rfc5129>.
[RFC5462] Andersson, L. and R. Asati, "Multiprotocol Label Switching
(MPLS) Label Stack Entry: "EXP" Field Renamed to "Traffic
Class" Field", RFC 5462, DOI 10.17487/RFC5462, February
2009, <https://www.rfc-editor.org/info/rfc5462>.
[RFC6003] Papadimitriou, D., "Ethernet Traffic Parameters",
RFC 6003, DOI 10.17487/RFC6003, October 2010,
<https://www.rfc-editor.org/info/rfc6003>.
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[RFC7510] Xu, X., Sheth, N., Yong, L., Callon, R., and D. Black,
"Encapsulating MPLS in UDP", RFC 7510,
DOI 10.17487/RFC7510, April 2015,
<https://www.rfc-editor.org/info/rfc7510>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>.
16.2. Informative references
[I-D.ietf-detnet-architecture]
Finn, N., Thubert, P., Varga, B., and J. Farkas,
"Deterministic Networking Architecture", draft-ietf-
detnet-architecture-05 (work in progress), May 2018.
[I-D.ietf-detnet-dp-alt]
Korhonen, J., Farkas, J., Mirsky, G., Thubert, P.,
Zhuangyan, Z., and L. Berger, "DetNet Data Plane Protocol
and Solution Alternatives", draft-ietf-detnet-dp-alt-00
(work in progress), October 2016.
[I-D.ietf-detnet-dp-sol-ip]
Korhonen, J., Varga, B., "DetNet IP Data Plane
Encapsulation", 2018.
[I-D.sdt-detnet-security]
Mizrahi, T., Grossman, E., Hacker, A., Das, S.,
"Deterministic Networking (DetNet) Security
Considerations, draft-sdt-detnet-security, work in
progress", 2017.
[IEEE8021CB]
Finn, N., "Draft Standard for Local and metropolitan area
networks - Seamless Redundancy", IEEE P802.1CB
/D2.1 P802.1CB, December 2015,
<http://www.ieee802.org/1/files/private/cb-drafts/
d2/802-1CB-d2-1.pdf>.
[IEEE8021Q]
IEEE 802.1, "Standard for Local and metropolitan area
networks--Bridges and Bridged Networks (IEEE Std 802.1Q-
2014)", 2014, <http://standards.ieee.org/about/get/>.
[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, <https://www.rfc-editor.org/info/rfc2205>.
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[RFC3985] Bryant, S., Ed. and P. Pate, Ed., "Pseudo Wire Emulation
Edge-to-Edge (PWE3) Architecture", RFC 3985,
DOI 10.17487/RFC3985, March 2005,
<https://www.rfc-editor.org/info/rfc3985>.
[RFC4448] Martini, L., Ed., Rosen, E., El-Aawar, N., and G. Heron,
"Encapsulation Methods for Transport of Ethernet over MPLS
Networks", RFC 4448, DOI 10.17487/RFC4448, April 2006,
<https://www.rfc-editor.org/info/rfc4448>.
[RFC5654] Niven-Jenkins, B., Ed., Brungard, D., Ed., Betts, M., Ed.,
Sprecher, N., and S. Ueno, "Requirements of an MPLS
Transport Profile", RFC 5654, DOI 10.17487/RFC5654,
September 2009, <https://www.rfc-editor.org/info/rfc5654>.
[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,
<https://www.rfc-editor.org/info/rfc5921>.
[RFC6073] Martini, L., Metz, C., Nadeau, T., Bocci, M., and M.
Aissaoui, "Segmented Pseudowire", RFC 6073,
DOI 10.17487/RFC6073, January 2011,
<https://www.rfc-editor.org/info/rfc6073>.
[RFC7551] Zhang, F., Ed., Jing, R., and R. Gandhi, Ed., "RSVP-TE
Extensions for Associated Bidirectional Label Switched
Paths (LSPs)", RFC 7551, DOI 10.17487/RFC7551, May 2015,
<https://www.rfc-editor.org/info/rfc7551>.
[RFC7950] Bjorklund, M., Ed., "The YANG 1.1 Data Modeling Language",
RFC 7950, DOI 10.17487/RFC7950, August 2016,
<https://www.rfc-editor.org/info/rfc7950>.
[RFC8040] Bierman, A., Bjorklund, M., and K. Watsen, "RESTCONF
Protocol", RFC 8040, DOI 10.17487/RFC8040, January 2017,
<https://www.rfc-editor.org/info/rfc8040>.
[RFC8169] Mirsky, G., Ruffini, S., Gray, E., Drake, J., Bryant, S.,
and A. Vainshtein, "Residence Time Measurement in MPLS
Networks", RFC 8169, DOI 10.17487/RFC8169, May 2017,
<https://www.rfc-editor.org/info/rfc8169>.
Appendix A. Example of DetNet data plane operation
[Editor's note: Add a simplified example of DetNet data plane and how
labels etc work in the case of MPLS-based PSN and utilizing PREOF.
Korhonen & Varga Expires January 1, 2019 [Page 45]
Internet-Draft DetNet MPLS Data Plane June 2018
The figure is subject to change depending on the further DT decisions
on the label handling..]
Authors' Addresses
Jouni Korhonen (editor)
Email: jouni.nospam@gmail.com
Balazs Varga (editor)
Ericsson
Magyar Tudosok krt. 11.
Budapest 1117
Hungary
Email: balazs.a.varga@ericsson.com
Korhonen & Varga Expires January 1, 2019 [Page 46]
