DetNet Working Group G. Mirsky
Internet-Draft ZTE Corp.
Intended status: Standards Track M. Chen
Expires: November 23, 2019 Huawei
May 22, 2019
Operations, Administration and Maintenance (OAM) for Deterministic
Networks (DetNet)
draft-mirsky-detnet-oam-03
Abstract
This document lists functional requirements for Operations,
Administration and Maintenance (OAM) toolset in Deterministic
Networks (DetNet) and, using these requirements; defines format and
use principals of the DetNet service Associated Channel.
Status of This Memo
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the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Conventions used in this document . . . . . . . . . . . . . . 3
2.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3
2.2. Keywords . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Requirements . . . . . . . . . . . . . . . . . . . . . . . . 4
4. DetNet Data Plane in Support of Active OAM . . . . . . . . . 5
4.1. MPLS Encapsulation . . . . . . . . . . . . . . . . . . . 5
4.1.1. DetNet Active OAM Encapsulation . . . . . . . . . . . 6
4.1.2. IP Encapsulation . . . . . . . . . . . . . . . . . . 8
4.2. DetNet Replication, Elimination, and Ordering Sub-
functions Interaction with Active OAM . . . . . . . . . . 8
5. Use of Hybrid OAM in DetNet . . . . . . . . . . . . . . . . . 8
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9
7. Security Considerations . . . . . . . . . . . . . . . . . . . 9
8. Acknowledgment . . . . . . . . . . . . . . . . . . . . . . . 9
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 9
9.1. Normative References . . . . . . . . . . . . . . . . . . 9
9.2. Informational References . . . . . . . . . . . . . . . . 10
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 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 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.
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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".
CW Control Word
DetNet Deterministic Networks
d-ACH DetNet Associated Channel Header
d-CW DetNet Control Word
DNH DetNet Header
GAL Generic Associated Channel Label
G-ACh Generic Associated Channel
OAM: Operations, Administration and Maintenance
PREF Packet Replication and Elimination Function
POF Packet Ordering 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 the 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.
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3. Requirements
This section lists requirements for OAM in DetNet domain:
1. The listed requirements MUST be supported for 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.
5. DetNet OAM packets MUST be in-band, i.e., follow precisely 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 MAY support hybrid performance measurement methods.
13. DetNet OAM MUST support unidirectional performance measurement
methods. Calculated performance metrics MUST include but are
not limited to throughput, packet loss, delay and delay
variation metrics. [RFC6374] provides excellent details on
performance measurement and performance metrics.
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14. 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.
15. DetNet OAM MUST support methods to enable survivability of the
DetNet domain. These recovery methods MAY use protection
switching and restoration.
16. DetNet OAM MUST support the discovery of Packet Replication,
Elimination, and Order preservation sub-functions locations in
the domain.
17. DetNet OAM MUST support testing of Packet Replication,
Elimination, and Order preservation sub-functions in the domain.
18. DetNet OAM MUST support monitoring any sub-set of paths
traversed through the DetNet domain by the DetNet flow.
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:
DetNet OAM packets MUST be in-band, i.e., follow precisely the
same path as DetNet data plane traffic both for unidirectional and
bi-directional DetNet paths.
4.1. MPLS Encapsulation
The Det Net data plane encapsulation in transport network with MPLS
and IP encapsulations specified in [I-D.ietf-detnet-dp-sol-mpls] and
[I-D.ietf-detnet-dp-sol-ip] 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.
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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 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 the S-Label and packet sequencing
information, e.g., the value in the Sequence Number field of DetNet
CW (d-CW). The replication sub-function uses the S-Label information
only. For data packets Figure 2 presents an example of PREF in
DetNet 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
4.1.1. DetNet Active OAM Encapsulation
DetNet OAM, like PW OAM, uses PW Associated Channel Header defined in
[RFC4385]. Figure 3 displays the encapsulation of a DetNet active
OAM packet.
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+---------------------------------+
| |
| DetNet Flow |
| OAM Packet |
| |
+---------------------------------+ <--\
| DetNet Associated Channel Header| |
+=================================+ +--> DetNet OAM data plane
| S-Label | | MPLS encapsulation
+---------------------------------+ <--/
| T-Label(s) |
+---------------------------------+
| Data-Link |
+---------------------------------+
| Physical |
+---------------------------------+
Figure 3: DetNet active 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|Version|Sequence Number| Channel Type |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 4: DetNet Associated Channel Header Format
Figure 4 displays the format of the DetNet Associated Channel Header
(d-ACH). The meanings of the fields in the d-ACH are:
Bits 0..3 MUST be 0b0001. This value of the first nibble allows
the packet to be distinguished from an IP packet [RFC4928] and a
DetNet data packet [I-D.ietf-detnet-dp-sol-mpls].
Version: this is the version number of the d-ACH. This
specification defines version 0.
Sequence Number: this is unsigned eight bits-long field. The
originating DetNet node MUST set the value of the Sequence Number
field to a non-zero before packet being transmitted. The
originating node MUST monotonically increase the value of the
Sequence Number field for the every next active OAM packet.
Channel Type: the value of DetNet Associated Channel Type is one
of values defined in the IANA PW Associated Channel Type registry.
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The DetNet flow, according to [I-D.ietf-detnet-dp-sol-mpls], is
identified by the S-label that MUST be at the bottom of the stack.
Active OAM packet MUST have d-ACH immediately following the S-label.A
DetNet node originating an OAM packet MUST ensure that the value of
the Sequence Number field in d-ACH is monotonically increasing for
the given value of the Channel Type field.
The Generic Associated Channel Label (GAL), defined in [RFC5586] and
[RFC6423], provides a generalized label-based exception mechanism to
indicate that the packet is on a Generic Associated Channel (G-ACh)
and that ACH immediately follows the label stack. For the DetNet
domain in MPLS transport network, GAL MAY be used. If GAL is used,
it MUST precede S-Label on the label stack, and the S-Label MUST be
followed by d-ACH.
4.1.2. IP Encapsulation
[Author's Note: This will be defined based on the DetNet Flow ID
specification for IP underlay in [I-D.ietf-detnet-dp-sol-ip].]
4.2. DetNet Replication, Elimination, and Ordering Sub-functions
Interaction with Active OAM
At the DetNet service layer, special functions MAY be applied to the
particular DetNet flow - PREF to potentially lower packet loss,
improve the probability of on-time packet delivery and Packet
Ordering Function (POF) to ensure in-order packet delivery. As data
and the active OAM packets have the same Flow ID, S-label, sub-
functions that rely on sequencing information in the DetNet service
layer MUST process 28 MSBs of the d-ACH as the source of the
sequencing information for the OAM packet.
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 the
value of a designated field in the packet encapsulation. One example
of such a 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.
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6. IANA Considerations
TBA
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
Authors extend their appreciation to Pascal Thubert for his
insightful comments and productive discussion that helped to improve
the document.
9. References
9.1. Normative References
[I-D.ietf-detnet-architecture]
Finn, N., Thubert, P., Varga, B., and J. Farkas,
"Deterministic Networking Architecture", draft-ietf-
detnet-architecture-13 (work in progress), May 2019.
[I-D.ietf-detnet-dp-sol-ip]
Korhonen, J. and B. Varga, "DetNet IP Data Plane
Encapsulation", draft-ietf-detnet-dp-sol-ip-02 (work in
progress), March 2019.
[I-D.ietf-detnet-dp-sol-mpls]
Korhonen, J. and B. Varga, "DetNet MPLS Data Plane
Encapsulation", draft-ietf-detnet-dp-sol-mpls-02 (work in
progress), March 2019.
[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>.
[RFC5586] Bocci, M., Ed., Vigoureux, M., Ed., and S. Bryant, Ed.,
"MPLS Generic Associated Channel", RFC 5586,
DOI 10.17487/RFC5586, June 2009,
<https://www.rfc-editor.org/info/rfc5586>.
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[RFC6423] Li, H., Martini, L., He, J., and F. Huang, "Using the
Generic Associated Channel Label for Pseudowire in the
MPLS Transport Profile (MPLS-TP)", RFC 6423,
DOI 10.17487/RFC6423, November 2011,
<https://www.rfc-editor.org/info/rfc6423>.
[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>.
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>.
[RFC4928] Swallow, G., Bryant, S., and L. Andersson, "Avoiding Equal
Cost Multipath Treatment in MPLS Networks", BCP 128,
RFC 4928, DOI 10.17487/RFC4928, June 2007,
<https://www.rfc-editor.org/info/rfc4928>.
[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>.
Authors' Addresses
Greg Mirsky
ZTE Corp.
Email: gregimirsky@gmail.com
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Mach(Guoyi) Chen
Huawei
Email: mach.chen@huawei.com
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