Internet DRAFT - draft-mirsky-sfc-pmamm
draft-mirsky-sfc-pmamm
SFC Working Group G. Mirsky
Internet-Draft Ericsson
Intended status: Experimental G. Fioccola
Expires: 28 March 2022 Huawei Technologies
T. Mizrahi
Huawei Network.IO Innovation Lab
24 September 2021
Performance Measurement (PM) with Alternate Marking Method in Service
Function Chaining (SFC) Domain
draft-mirsky-sfc-pmamm-14
Abstract
This document describes how the alternate marking method can be used
as the efficient performance measurement method taking advantage of
the actual data flows in a Service Function Chaining (SFC) domain.
Status of This Memo
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This Internet-Draft will expire on 28 March 2022.
Copyright Notice
Copyright (c) 2021 IETF Trust and the persons identified as the
document authors. All rights reserved.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Conventions used in this document . . . . . . . . . . . . . . 3
2.1. Acronyms . . . . . . . . . . . . . . . . . . . . . . . . 3
2.2. Requirements Language . . . . . . . . . . . . . . . . . . 3
3. Mark Field in NSH Base Header . . . . . . . . . . . . . . . . 3
4. Theory of Operation . . . . . . . . . . . . . . . . . . . . . 4
4.1. Single Mark Enabled Measurement . . . . . . . . . . . . . 5
4.2. Multiplexed Mark Enabled Measurement . . . . . . . . . . 5
4.3. Residence Time Measurement with the Alternate Marking
Method . . . . . . . . . . . . . . . . . . . . . . . . . 6
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6
5.1. Mark Field in NSH Base Header . . . . . . . . . . . . . . 6
6. Security Considerations . . . . . . . . . . . . . . . . . . . 7
7. Acknowledgment . . . . . . . . . . . . . . . . . . . . . . . 7
8. References . . . . . . . . . . . . . . . . . . . . . . . . . 7
8.1. Normative References . . . . . . . . . . . . . . . . . . 7
8.2. Informative References . . . . . . . . . . . . . . . . . 7
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 8
1. Introduction
[RFC7665] introduced the architecture of a Service Function Chain
(SFC) in the network and defined its components. These include
Classifier, Service Function Forwarder (SFF), Service Function (SF),
and Service Function proxy. [RFC8924] provides a reference framework
for Operations, Administration and Maintenance (OAM) for SFC.
[RFC8321] describes the hybrid performance measurement method, which
can be used to measure packet loss, latency, and jitter on live
traffic. Because this method is based on marking consecutive batches
of packets, the procedure is often referred to as Alternate Marking
Method (AMM).
This document defines how packet loss and delay metrics of a service
flow over end-to-end (E2E) Service Function Path (SFP) or any SFP
segment can be measured using AMM. This document is aligned with the
SFC OAM Performance Measurement requirements defined in [RFC8924].
It states that any SFC-aware network device must have the ability to
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perform loss and delay measurements over the service function chain
as a unit, i.e., E2E, or to a specific segment of service function
through the SFC. Besides, AMM can be used in combination with
[I-D.ietf-sfc-ioam-nsh] complementing it in achieving the SFC
performance measurement objective.
2. Conventions used in this document
2.1. Acronyms
AMM: Alternate Marking Method
OAM: Operations, Administration and Maintenance
SFC: Service Function Chain
SFP: Service Function Path
SF: Service Function
SFF: Service Function Forwarder
SPI: Service Path Identifier
NSH: Network Service Header
E2E end-to-end
2.2. 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.
3. Mark Field in NSH Base Header
[RFC8300] defines the format of the Network Service Header (NSH).
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Ver|O|M| TTL | Length |U|U|U|U|MD Type| Proto |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 1: NSH Base format
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This document defines the one-bit long field, referred to as Mark
field (M in Figure 1, as part of NSH Base and designated for the
alternate marking performance measurement method [RFC8321]. The Mark
field MUST be set to 0 at initialization of NSH and ignored on the
receipt when the method is not in use. The Mark field MUST NOT be
used in defining forwarding and/or quality of service treatment of an
SFC packet. The Mark field MUST be used only for the performance
measurement of data traffic in the SFC layer. Though the setting of
the field to any value likely not affect forwarding and/or quality of
service treatment of a packet, the alternate marking method in the
SFC layer is characterized as an example of a hybrid performance
measurement method according to [RFC7799].
4. Theory of Operation
The marking method can be successfully used in the SFC. Without
limiting any generality consider SFC presented in Figure 2. Any
combination of markings, Loss and/or Delay, can be applied to a
service flow by any SFC component at either ingress or egress point
to perform node, link, segment, or E2E measurement to detect
performance degradation defects and localize them efficiently.
+---+ +---+ +---+ +---+ +---+ +---+
|SF1| |SF2| |SF3| |SF4| |SF5| |SF6|
+---+ +---+ +---+ +---+ +---+ +---+
\ / \ / \ /
+----------+ +----+ +----+ +----+
|Classifier|---|SFF1|---------|SFF2|---------|SFF3|
+----------+ +----+ +----+ +----+
Figure 2: SFC network
An SFP might include a Re-classifier. Processing of an SFC packet by
the Re-classifier might result in that packet being directed to a
different SFP identified, for example, by Service Path Identifier's
(SPI) value A'. In that case, the Re-classifier MUST set the value
of the Mark field according to the local AMM policy defined for the
SPI's value A'. Note that the default AMM policy is to set the value
of the Mark field to 0.
Using the marking method, a component of the SFC creates distinct
sub-flows in the particular service traffic over SFC. Each sub-flow
consists of consecutive blocks that are unambiguously recognizable by
a monitoring point at any component of the SFC and can be measured to
calculate packet loss and/or packet delay metrics.
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4.1. Single Mark Enabled Measurement
As explained in the [RFC8321], marking can be applied to delineate
blocks of packets based either on the equal number of packets in a
block or based on the same time interval. The latter method offers
better control as it allows a better account for capabilities of
downstream nodes to report statistics related to batches of packets
and, at the same time, time resolution that affects defect detection
interval.
The Mark flag is used to create distinctive flows to measure the
packet loss by switching the value of the Mark flag every N-th packet
or at specified time intervals. Delay metrics MAY be calculated with
the alternate flow using any of the following methods:
* First/Last Packet Delay calculation: whenever the marking, i.e.,
the value of Mark flag changes a component of the SFC can store
the timestamp of the first/last packet of the block. The
timestamp can be compared with the timestamp of the packet that
arrived in the same order through a monitoring point at a
downstream component of the SFC to compute packet delay. Because
timestamps collected based on the order of arrival, this method is
sensitive to packet loss and re-ordering of packets
* Average Packet Delay calculation: an average delay is calculated
by considering the packets' average arrival time within a single
block. A component of the SFC may collect timestamps for each
packet received within a single block. The timestamp average is
the sum of all the timestamps divided by the total number of
packets received. Then the difference between averages calculated
at two monitoring points is the average packet delay on that
segment. This method is robust to out-of-order packets and packet
loss (only a small error is introduced). This method only
provides a single metric for the duration of the block, and it
doesn't give the minimum and maximum delay values. Highly
optimized implementation of the method can reduce the duration of
the block and thus overcome the limitation.
4.2. Multiplexed Mark Enabled Measurement
There is also a scheme that method allows measurement of minimum and
maximum delays for the monitored flow using a single marking flag.
This methodology is described in
[I-D.mizrahi-ippm-compact-alternate-marking]. The concept is that in
the middle of each block of packets with a certain value of the M
flag, a single packet has the M flag inverted. By examining the
stream, the packets with the inverted bit can be easily identified
and employed for delay measurement. This variation of AMM is
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advantageous because it requires only one bit from each packet, and
such bits are always in short supply.
4.3. Residence Time Measurement with the Alternate Marking Method
Residence time is the variable part of the propagation delay that a
packet experiences while traversing a network, e.g., SFC. Residence
Time over an SFC is the sum of the nodal residence times, i.e.,
periods that the packet spent in each SFF that composes the SFC. The
nodal residence time in SFC itself is the sum of sub-nodal residence
times that the packet spent in each of SFs that are part of the given
SFC and are mapped to the SFF. The residence time and deviation of
the residence time metrics may include any combination of minimum,
maximum values over the measurement period. It also may include
mean, median, and percentiles calculated values. These metrics may
be used to evaluate the performance of the SFC and its elements
before and during its operation.
Use of the specially marked packets simplifies residence time
measurement and correlation of the measured metrics over the E2E SFC.
For example, AMM may be used as described in Section 4.2 to identify
packets in the data flow to be used to measure the residence time.
The nodal and sub-nodal residence time metrics can be locally
calculated and then collected using either in-band or out-band OAM
mechanisms.
5. IANA Considerations
5.1. Mark Field in NSH Base Header
This document requests IANA to allocate the one-bit field from NSH
Base Header Bits [RFC8300] as the Mark field of NSH as the following:
+==============+=============+===============+
| Bit Position | Description | Reference |
+==============+=============+===============+
| TBA | Mark field | This document |
+--------------+-------------+---------------+
Table 1: Mark field of SFC NSH
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6. Security Considerations
This document defines the use of AMM in an SFC domain and thus all
security considerations specific to SFC discussed in [RFC7665] and
[RFC8300] are applicable. By introducing AMM into the SFC
environment, it inherits all security considerations discussed in
[RFC8321]. A new Mark flag is defined in this specification to be
used by AMM. Processing of AMM does require additional computational
resources and creates a certain amount of state information per AMM
flow performance metrics. An implementation MUST provide control
over the number of concurrent AMM flows that a node process.
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>.
[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>.
8.2. Informative References
[I-D.ietf-sfc-ioam-nsh]
Brockners, F. and S. Bhandari, "Network Service Header
(NSH) Encapsulation for In-situ OAM (IOAM) Data", Work in
Progress, Internet-Draft, draft-ietf-sfc-ioam-nsh-06, 31
July 2021, <https://datatracker.ietf.org/doc/html/draft-
ietf-sfc-ioam-nsh-06>.
[I-D.mizrahi-ippm-compact-alternate-marking]
Mizrahi, T., Arad, C., Fioccola, G., Cociglio, M., Chen,
M., Zheng, L., and G. Mirsky, "Compact Alternate Marking
Methods for Passive and Hybrid Performance Monitoring",
Work in Progress, Internet-Draft, draft-mizrahi-ippm-
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compact-alternate-marking-05, 6 July 2019,
<https://datatracker.ietf.org/doc/html/draft-mizrahi-ippm-
compact-alternate-marking-05>.
[RFC7665] Halpern, J., Ed. and C. Pignataro, Ed., "Service Function
Chaining (SFC) Architecture", RFC 7665,
DOI 10.17487/RFC7665, October 2015,
<https://www.rfc-editor.org/info/rfc7665>.
[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>.
[RFC8924] Aldrin, S., Pignataro, C., Ed., Kumar, N., Ed., Krishnan,
R., and A. Ghanwani, "Service Function Chaining (SFC)
Operations, Administration, and Maintenance (OAM)
Framework", RFC 8924, DOI 10.17487/RFC8924, October 2020,
<https://www.rfc-editor.org/info/rfc8924>.
Authors' Addresses
Greg Mirsky
Ericsson
Email: gregimirsky@gmail.com
Giuseppe Fioccola
Huawei Technologies
Email: giuseppe.fioccola@huawei.com
Tal Mizrahi
Huawei Network.IO Innovation Lab
Israel
Email: tal.mizrahi.phd@gmail.com
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