Operations, Administration and Maintenance (OAM) for Deterministic Networks (DetNet)
draft-mirsky-detnet-oam-00
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| Author | Greg Mirsky | ||
| Last updated | 2018-06-02 | ||
| Replaced by | draft-mirsky-detnet-mpls-oam, draft-mirsky-detnet-ip-oam | ||
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draft-mirsky-detnet-oam-00
DetNet Working Group G. Mirsky
Internet-Draft ZTE Corp.
Intended status: Informational June 2, 2018
Expires: December 4, 2018
Operations, Administration and Maintenance (OAM) for Deterministic
Networks (DetNet)
draft-mirsky-detnet-oam-00
Abstract
This document lists functional requirements for Operations,
Administration and Maintenance (OAM) toolset in Deterministic
Networks (DetNet) and, using these requirements, and analyzes
possible DetNet data plane solutions.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
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Task Force (IETF). Note that other groups may also distribute
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This Internet-Draft will expire on December 4, 2018.
Copyright Notice
Copyright (c) 2018 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Conventions used in this document . . . . . . . . . . . . . . 2
2.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 2
2.2. Keywords . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Requirements . . . . . . . . . . . . . . . . . . . . . . . . 3
4. DetNet Data Plane in Support of Active OAM . . . . . . . . . 4
4.1. DetNet Active OAM Encapsulation . . . . . . . . . . . . . 6
4.2. DetNet PREF Interaction with Active OAM . . . . . . . . . 6
4.3. Alternative Encapsulation for DetNet . . . . . . . . . . 7
5. Use of Hybrid OAM in DetNet . . . . . . . . . . . . . . . . . 8
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8
7. Security Considerations . . . . . . . . . . . . . . . . . . . 9
8. Acknowledgment . . . . . . . . . . . . . . . . . . . . . . . 9
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 9
9.1. Normative References . . . . . . . . . . . . . . . . . . 9
9.2. Informational References . . . . . . . . . . . . . . . . 10
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 10
1. Introduction
[I-D.ietf-detnet-architecture] introduces and explains Deterministic
Networks (DetNet) architecture and how the Packet Replication and
Elimination function (PREF) can be used to ensure low packet drop
ratio in DetNet domain.
Operations, Administration and Maintenance (OAM) protocols are used
to detect, localize defects in the network, and monitor network
performance. Some OAM functions, e.g., failure detection, work in
the network proactively, while others, e.g., defect localization,
usually performed on-demand. These tasks achieved by a combination
of active and hybrid, as defined in [RFC7799], OAM methods.
This document lists the functional requirements toward OAM for DetNet
domain. The list can further be used to for gap analysis of
available OAM tools to identify possible enhancements of existing or
whether new OAM tools are required to support proactive and on-demand
path monitoring and service validation.
2. Conventions used in this document
2.1. Terminology
The term "DetNet OAM" used in this document interchangeably with
longer version "set of OAM protocols, methods and tools for
Deterministic Networks".
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AC Associated Channel
CW Control Word
DetNet Deterministic Networks
d-CW DetNet Control Word
OAM: Operations, Administration and Maintenance
PREF Packet Replication and Elimination Function
PW Pseudowire
RDI Remote Defect Indication
Underlay Network or Underlay Layer: The network that provides
connectivity between the DetNet nodes. MPLS network providing LSP
connectivity between DetNet nodes is an example of underlay layer.
DetNet Node - a node that is an actor in the DetNet domain. DetNet
domain edge node and node that performs PREF within the domain are
examples of DetNet node.
2.2. Keywords
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.
3. Requirements
This section lists requirements for OAM in DetNet domain:
1. The listed requirements MUST be supported with any type of
underlay network over which a DetNet domain can be realized.
2. It MUST be possible to initiate DetNet OAM session from any
DetNet node towards another DetNet node(s) within given domain.
3. It SHOULD be possible to initialize DetNet OAM session from a
centralized controller.
4. DetNet OAM MUST support proactive and on-demand OAM monitoring
and measurement methods.
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5. DetNet OAM packets MUST be in-band, i.e. follow exactly the same
path as DetNet data plane traffic both for unidirectional and
bi-directional DetNet paths.
6. DetNet OAM MUST support unidirectional OAM methods, continuity
check, connectivity verification, and performance measurement.
7. DetNet OAM MUST support bi-directional OAM methods. Such OAM
methods MAY combine in-band monitoring or measurement in the
forward direction and out-of-bound notification in the reverse
direction, i.e. from egress to ingress end point of the OAM test
session.
8. DetNet OAM MUST support proactive monitoring of a DetNet node
availability in the given DetNet domain.
9. DetNet OAM MUST support Path Maximum Transmission Unit
discovery.
10. DetNet OAM MUST support Remote Defect Indication (RDI)
notification to the DetNet node performing continuity checking.
11. DetNet OAM MUST support performance measurement methods.
12. DetNet OAM MUST support unidirectional performance measurement
methods. Calculated performance metrics MUST include but are
not limited to throughput, loss, delay and delay variation
metrics. [RFC6374] provides great details on performance
measurement and performance metrics.
13. DetNet OAM MUST support defect notification mechanism, like
Alarm Indication Signal. Any DetNet node in the given DetNet
domain MAY originate a defect notification addressed to any
subset of nodes within the domain.
14. DetNet OAM MUST support methods to enable survivability of the
DetNet domain. These recovery methods MAY use protection
switching and restoration.
4. DetNet Data Plane in Support of Active OAM
OAM protocols and mechanisms act within the data plane of the
particular networking layer. And thus it is critical that the data
plane encapsulation supports OAM mechanisms in such a way to comply
with the above-listed requirements. One of such examples that
require special consideration is requirement #5:
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DetNet OAM packets MUST be in-band, i.e. follow exactly the same
path as DetNet data plane traffic both for unidirectional and bi-
directional DetNet paths.
The data plane encapsulation for DetNet specified in
[I-D.ietf-detnet-dp-sol] has been analyzed in details in
[I-D.bryant-detnet-mpls-dp] and [I-D.malis-detnet-ip-dp] for use in
MPLS and IP networks respectively. For the MPLS underlay network
DetNet flows to be encapsulated analogous to pseudowires (PW) over
MPLS packet switched network, as described in [RFC3985], [RFC4385].
Generic PW MPLS Control Word (CW), defined in [RFC4385], for DetNet
displayed in Figure 1.
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 1: DetNet Control Word Format
PREF in the DetNet domain composed by a combination of nodes that
perform replication and elimination sub-functions. The elimination
sub-function always uses packet sequencing information, e.g., value
in the Sequence Number field of DetNet CW (d-CW). The replication
sub-function uses one of two options:
o use S-Label and d-CW information;
o use S-Label information.
For data packets Figure 2 presents an example of PREF in DetNet
domain regardless of how the replication sub-function realized in the
domain.
1111 11111111 111111 112212 112212 132213
CE1----EN1--------R1-------R2-------R3--------EN2----CE2
\2 22222/ 3 /
\2222222 /----+ 3 /
+------R4------------------------+
333333333333333333333333
Figure 2: DetNet Data Plane Based on PW
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4.1. DetNet Active OAM Encapsulation
DetNet OAM, like PW OAM, uses PW Associated Channel Header defined in
[RFC4385]. Figure 3 displays encapsulation of a DetNet active OAM
packet. Figure 4 displays format of the DetNet Associated Channel
(AC).
+---------------------------------+
| |
| DetNet Flow |
| OAM Packet |
| |
+---------------------------------+ <--\
| DetNet Associated Channel | |
+=================================+ +--> DetNet OAM data plane
| S-Label | | MPLS encapsulation
+---------------------------------+ <--/
| T-Label(s) |
+---------------------------------+
| Data-Link |
+---------------------------------+
| Physical |
+---------------------------------+
Figure 3: DetNet PW OAM Packet Encapsulation
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 1|0 0 0 0|0 0 0 0 0 0 0 0| Channel Type |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 4: DetNet Associated Channel Header Format
4.2. DetNet PREF Interaction with Active OAM
Consider the scenario when EN1 injects DetNet active OAM packet with
the same S-Label as the DetNet service reflected in Figure 2. EN1 is
the first node with the replication sub-function. If the replication
uses S-Label information and the sequencing information in d-CW (the
first option), then EN1 will only forward the OAM packet without
replicating it because OAM encapsulation doesn't include d-CW. The
path that active OAM packet traverses through the DetNet domain
presented in Figure 5 with 'O'. The figure clearly demonstrates that
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the DetNet OAM packet does not traverse all the segments that are
traversed by the DetNet data packet as displayed in Figure 2.
O O O O
CE1----EN1--------R1-------R2-------R3--------EN2----CE2
\ / /
\ /----+ /
+------R4------------------------+
Figure 5: OAM in DetNet Data Plane Based on PW
If the replication is based solely on S-Label (the second option),
EN1 node will replicate the OAM packet accordingly. The replicated
packet will be processed by the replication function at R4. As
result, the same OAM packet will be forwarded and another copy
injected into the network. This case displayed in Figure 6. The OAM
packet does traverse all links and nodes that the DetNet data packet
of the monitored flow traverses but the egress node EN2 receives
multiple, three in this example, copies of the same packet because
the elimination function cannot be applied to the DetNet active OAM
packet.
O O OO OO
CE1----EN1--------R1-------R2-------R3--------EN2----CE2
\O O/ O/
\ O/----+ /
+------R4------------------------+
O
Figure 6: Over-Replication of Active OAM Packets
4.3. Alternative Encapsulation for DetNet
Introduction of DetNet header, that includes all necessary
characteristic information to efficiently, among other scenarios, use
multipath underlay, perform PERF, as part of DetNet service layer
encapsulation allows DetNet active OAM packets to be in-band with the
monitored DetNet data flow. Figure 7 presents the format of DetNet
packet with MPLS encapsulation.
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+---------------------------------+
| |
| DetNet Flow |
| Payload or OAM |
| Packet |
+---------------------------------+
| DetNet Header |
~ ~
| |
+=================================+
| S-Label |
+---------------------------------+
| T-Label(s) |
+---------------------------------+
| Data-Link |
+---------------------------------+
| Physical |
+---------------------------------+
Figure 7: DetNet Packet with DetNet Header Encapsulation over MPLS
Underlay
Demultiplexing of type of the payload encapsulated in the DetNet
packet achieved using a field that explicitly identifies, e.g., OAM,
Ethernet, or IPvX.
5. Use of Hybrid OAM in DetNet
Hybrid OAM methods are used in performance monitoring and defined in
[RFC7799] as:
Hybrid Methods are Methods of Measurement that use a combination
of Active Methods and Passive Methods ...
A hybrid measurement method may produce metrics as close to passive
but it still alters something in a data packet even if that is value
of a designated field in the packet encapsulation. One example of
such hybrid measurement method is the Alternate Marking method
described in [RFC8321]. Reserving the field for the Alternate
Marking method in the DetNet Header will enhance available to an
operator set of DetNet OAM tools.
6. IANA Considerations
This document does not propose any IANA consideration. This section
may be removed.
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7. Security Considerations
This document lists the OAM requirements for a DetNet domain and does
not raise any security concerns or issues in addition to ones common
to networking.
8. Acknowledgment
TBD
9. References
9.1. Normative References
[I-D.bryant-detnet-mpls-dp]
Bryant, S. and M. Chen, "Operation of Deterministic
Networks over MPLS", draft-bryant-detnet-mpls-dp-00 (work
in progress), March 2018.
[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-sol]
Korhonen, J., Andersson, L., Jiang, Y., Finn, N., Varga,
B., Farkas, J., Bernardos, C., Mizrahi, T., and L. Berger,
"DetNet Data Plane Encapsulation", draft-ietf-detnet-dp-
sol-04 (work in progress), March 2018.
[I-D.malis-detnet-ip-dp]
Malis, A., Bryant, S., Chen, M., and B. Varga, "DetNet IP
Encapsulation", draft-malis-detnet-ip-dp-00 (work in
progress), March 2018.
[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>.
[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>.
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9.2. Informational References
[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>.
[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>.
[RFC6374] Frost, D. and S. Bryant, "Packet Loss and Delay
Measurement for MPLS Networks", RFC 6374,
DOI 10.17487/RFC6374, September 2011,
<https://www.rfc-editor.org/info/rfc6374>.
[RFC7799] Morton, A., "Active and Passive Metrics and Methods (with
Hybrid Types In-Between)", RFC 7799, DOI 10.17487/RFC7799,
May 2016, <https://www.rfc-editor.org/info/rfc7799>.
[RFC8321] Fioccola, G., Ed., Capello, A., Cociglio, M., Castaldelli,
L., Chen, M., Zheng, L., Mirsky, G., and T. Mizrahi,
"Alternate-Marking Method for Passive and Hybrid
Performance Monitoring", RFC 8321, DOI 10.17487/RFC8321,
January 2018, <https://www.rfc-editor.org/info/rfc8321>.
Author's Address
Greg Mirsky
ZTE Corp.
Email: gregimirsky@gmail.com
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