Identification of Overlay Operations, Administration, and Maintenance (OAM)
draft-mirsky-rtgwg-oam-identify-00
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| Last updated | 2018-06-28 | ||
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draft-mirsky-rtgwg-oam-identify-00
RTGWG Working Group G. Mirsky
Internet-Draft ZTE Corp.
Intended status: Informational June 28, 2018
Expires: December 30, 2018
Identification of Overlay Operations, Administration, and Maintenance
(OAM)
draft-mirsky-rtgwg-oam-identify-00
Abstract
This document analyzes how the presence of Operations,
Administration, and Maintenance (OAM) control command and/or special
data is identified in some overlay networks, and an impact on the
choice of identification may have on OAM functionality.
Status of This Memo
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This Internet-Draft will expire on December 30, 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. Overlay Network Encapsulations . . . . . . . . . . . . . . . 3
3.1. Encapsulations with Meta-data . . . . . . . . . . . . . . 3
3.2. Fixed-size Encapsulations . . . . . . . . . . . . . . . . 5
3.3. Source Information Availability . . . . . . . . . . . . . 5
3.4. On-path OAM . . . . . . . . . . . . . . . . . . . . . . . 6
4. Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . 6
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6
6. Security Considerations . . . . . . . . . . . . . . . . . . . 7
7. Acknowledgment . . . . . . . . . . . . . . . . . . . . . . . 7
8. References . . . . . . . . . . . . . . . . . . . . . . . . . 7
8.1. Normative References . . . . . . . . . . . . . . . . . . 7
8.2. Informational References . . . . . . . . . . . . . . . . 7
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 9
1. Introduction
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, passive, and hybrid OAM methods, as defined in [RFC7799].
This document analyzes how the presence of Operations,
Administration, and Maintenance (OAM) control command and/or special
data, i.e., OAM packet, is identified in some overlay networks, and
an impact the choice of identification may have on OAM functionality
of active and hybrid OAM methods for the respective overlay network
encapsulation.
2. Conventions used in this document
2.1. Terminology
AMM Alternate Marking method
BIER Bit Indexed Explicit Replication
DetNet Deterministic Networks
GUE Generic UDP Encapsulation
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HTS Hybrid Two-step
NSH Network Service Header
NVO3 Network Virtualization Overlays
OAM Operations, Administration and Maintenance
SFC Service Function Chaining
TLV Type-Length-Value
VXLAN-GPE Generic Protocol Extension for VXLAN
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.
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. Overlay Network Encapsulations
New overlay network encapsulations analyzed in two groups:
o encapsulations that support optional meta-data;
o fixed-size encapsulations.
3.1. Encapsulations with Meta-data
Number of the new encapsulation protocols (e.g., Geneve
[I-D.ietf-nvo3-geneve], GUE [I-D.ietf-intarea-gue], and SFC NSH
[RFC8300]) support use of Type-Length-Value (TLV) encoding to include
optional information into the header. The identification of OAM in
these protocols is as the following:
Geneve:
O (1 bit): OAM packet. This packet contains a control message
instead of a data payload. Endpoints MUST NOT forward the
payload and transit devices MUST NOT attempt to interpret or
process it. Since these are infrequent control messages, it is
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RECOMMENDED that endpoints direct these packets to a high
priority control queue (for example, to direct the packet to a
general purpose CPU from a forwarding ASIC or to separate out
control traffic on a NIC). Transit devices MUST NOT alter
forwarding behavior on the basis of this bit, such as ECMP link
selection.
GUE:
Undefined.
SFC NSH:
O bit: Setting this bit indicates an OAM packet.
Common between Geneve and NSH is the use of the dedicated flag to
identify the OAM packet and, at the same time, the presence of the
field that identifies the protocol of the payload that immediately
follows after the encapsulation header. [RFC8393] points that if the
value of that field interpreted as none, i.e., no payload follows the
header, then OAM may be included in TLVs, thus creating an active OAM
packet. The problem with this mechanism to support active OAM
methods may be a limitation of the size of data that can be included
in a TLV. For example, the maximum size of data in an NSH Meta-data
Type 2, as defined in section 2.5.1 [RFC8300], is 512 octets. The
maximum length of data in Geneve Option, per section 3.5
[I-D.ietf-nvo3-geneve], is 128 octets. Thus, using one TLV as active
OAM packet, would not allow creating test packets of larger size,
which is useful when measuring packet loss and latency with synthetic
traffic as part of service activation procedure.
[I-D.ietf-sfc-oam-framework] suggests that the O bit used to identify
OAM packet and the Next Protocol field identifies the OAM function:
While the presence of OAM marker in the overlay header (e.g., O
bit in the NSH header) indicates it as OAM packet, it is not
sufficient to indicate what OAM function the packet is intended
for.
At the same time, some of in-situ OAM proposals, e.g.,
[I-D.ietf-sfc-ioam-nsh], suggest using TLV to communicate hybrid OAM
commands and data. The proposed resolution of using the combination
of O bit and the Next Protocol field:
... the O bit MUST NOT be set for regular customer traffic which
also carries IOAM data and the O bit MUST be set for OAM packets
which carry only IOAM data without any regular data payload.
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implies that the O bit only identifies the active OAM packet and not
set when hybrid OAM methods used.
3.2. Fixed-size Encapsulations
Number of the new encapsulation protocols (e.g., VXLAN-GPE
[I-D.ietf-nvo3-vxlan-gpe], BIER [RFC8296]) suse fixed-size header.
The identification of OAM in these protocols is as the following:
VXLAN-GPE:
OAM Flag Bit (O bit): The O bit is set to indicate that the
packet is an OAM packet.
BIER:
OAM packet identified by the value of the Next Protocol field.
IANA BIER Next Protocol Identifiers registry includes the
identifier for OAM (5).
VXLAN-GPE use of a combination of OAM Flag Bit and the Next Protocol
field requires clarification of the header interpretation when the
OAM Flag Bit is set and the value of the Next Protocol field is one
of defined in section 3.2 of [I-D.ietf-nvo3-vxlan-gpe].
BIER encapsulation, defined in [RFC8296], identifies OAM message
immediately following the BIER header by the value of the Next
Protocol field.
3.3. Source Information Availability
Availability of the packet originator's source information is
required for active two-way OAM, e.g., echo request/reply. In cases
when the underlay network is IPv4/IPv6 the source information will be
provided by the encapsulation of the underlay. But when using MPLS
underlay network encapsulation of an active OAM packet have to follow
certain rules:
o if available, use Sender ID in the overlay domain (example BFIR ID
in BIER [RFC8296];
o use IP/UDP encapsulation of an OAM packet in overlay (similar to
Section 4.3 [RFC8029]).
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3.4. On-path OAM
In addition to active methods, OAM toolset may include methods that
don't use specially constructed and injected in the network test
packets. [RFC7799] defines OAM methods that are neither entirely
active nor passive but are combine both as hybrid methods.
One of the examples of the hybrid OAM method, in-situ OAM, mentioned
in Section 3.1. Another example, Alternate Marking method (AMM)
[RFC8321], enables on-path OAM functions, e.g., delay and loss
measurements, using the data traffic. Because AMM impact on the
network can be minimized, measured metrics can be correlated to the
network conditions experienced by the specific service. Of all
listed in Section 3, BIER allocated the field that may be used for
AMM, as discussed in [I-D.ietf-bier-pmmm-oam]. Applicability of AMM
to other overlay protocols, i.e. SFC NSH discussed in
[I-D.mirsky-sfc-pmamm] and Geneve [I-D.fmm-nvo3-pm-alt-mark], been
actively discussed.
Hybrid Two-step (HTS), defined in [I-D.mirsky-ippm-hybrid-two-step],
is provides on-path collection and transport of the telemetry
information. HTS enables accurate and consistent measurements by
separating the measurement action from the transport while ensuring
that the follow-up packet that carries the telemetry information does
follow the data packet that had triggered the measurement.
4. Conclusions
OAM control commands and data may be present as part of the overlay
encapsulation header or as a payload that follows the overlay network
header. The recommendations:
o OAM in the overlay header, if supported by the overlay network,
identified by the dedicated flag. Use of this method as active
OAM is possible but functionality is limited.
o OAM that follows the overlay header identified as payload type,
e.g. by the value of the Next Protocol field.
5. IANA Considerations
This document does not propose any IANA consideration. This section
may be removed.
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6. 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.
7. Acknowledgment
TBD
8. References
8.1. Normative References
[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>.
8.2. Informational References
[I-D.fmm-nvo3-pm-alt-mark]
Fioccola, G., Mirsky, G., and T. Mizrahi, "Performance
Measurement (PM) with Alternate Marking in Network
Virtualization Overlays (NVO3)", draft-fmm-nvo3-pm-alt-
mark-02 (work in progress), June 2018.
[I-D.ietf-bier-pmmm-oam]
Mirsky, G., Zheng, L., Chen, M., and G. Fioccola,
"Performance Measurement (PM) with Marking Method in Bit
Index Explicit Replication (BIER) Layer", draft-ietf-bier-
pmmm-oam-04 (work in progress), June 2018.
[I-D.ietf-intarea-gue]
Herbert, T., Yong, L., and O. Zia, "Generic UDP
Encapsulation", draft-ietf-intarea-gue-05 (work in
progress), December 2017.
[I-D.ietf-nvo3-geneve]
Gross, J., Ganga, I., and T. Sridhar, "Geneve: Generic
Network Virtualization Encapsulation", draft-ietf-
nvo3-geneve-06 (work in progress), March 2018.
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[I-D.ietf-nvo3-vxlan-gpe]
Maino, F., Kreeger, L., and U. Elzur, "Generic Protocol
Extension for VXLAN", draft-ietf-nvo3-vxlan-gpe-06 (work
in progress), April 2018.
[I-D.ietf-sfc-ioam-nsh]
Brockners, F., Bhandari, S., Govindan, V., Pignataro, C.,
Gredler, H., Leddy, J., Youell, S., Mizrahi, T., Mozes,
D., Lapukhov, P., and R. Chang, "NSH Encapsulation for In-
situ OAM Data", draft-ietf-sfc-ioam-nsh-00 (work in
progress), May 2018.
[I-D.ietf-sfc-oam-framework]
Aldrin, S., Pignataro, C., Kumar, N., Akiya, N., Krishnan,
R., and A. Ghanwani, "Service Function Chaining (SFC)
Operation, Administration and Maintenance (OAM)
Framework", draft-ietf-sfc-oam-framework-04 (work in
progress), March 2018.
[I-D.mirsky-ippm-hybrid-two-step]
Mirsky, G., Lingqiang, W., and G. Zhui, "Hybrid Two-Step
Performance Measurement Method", draft-mirsky-ippm-hybrid-
two-step-00 (work in progress), February 2018.
[I-D.mirsky-sfc-pmamm]
Mirsky, G., Fioccola, G., and T. Mizrahi, "Performance
Measurement (PM) with Alternate Marking Method in Service
Function Chaining (SFC) Domain", draft-mirsky-sfc-pmamm-03
(work in progress), June 2018.
[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>.
[RFC8029] Kompella, K., Swallow, G., Pignataro, C., Ed., Kumar, N.,
Aldrin, S., and M. Chen, "Detecting Multiprotocol Label
Switched (MPLS) Data-Plane Failures", RFC 8029,
DOI 10.17487/RFC8029, March 2017,
<https://www.rfc-editor.org/info/rfc8029>.
[RFC8296] Wijnands, IJ., Ed., Rosen, E., Ed., Dolganow, A.,
Tantsura, J., Aldrin, S., and I. Meilik, "Encapsulation
for Bit Index Explicit Replication (BIER) in MPLS and Non-
MPLS Networks", RFC 8296, DOI 10.17487/RFC8296, January
2018, <https://www.rfc-editor.org/info/rfc8296>.
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[RFC8300] Quinn, P., Ed., Elzur, U., Ed., and C. Pignataro, Ed.,
"Network Service Header (NSH)", RFC 8300,
DOI 10.17487/RFC8300, January 2018,
<https://www.rfc-editor.org/info/rfc8300>.
[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>.
[RFC8393] Farrel, A. and J. Drake, "Operating the Network Service
Header (NSH) with Next Protocol "None"", RFC 8393,
DOI 10.17487/RFC8393, May 2018,
<https://www.rfc-editor.org/info/rfc8393>.
Author's Address
Greg Mirsky
ZTE Corp.
Email: gregimirsky@gmail.com
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