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

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
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   Drafts is at https://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months
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   material or to cite them other than as "work in progress."

   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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   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents (https://trustee.ietf.org/
   license-info) in effect on the date of publication of this document.
   Please review these documents carefully, as they describe your rights
   and restrictions with respect to this document.  Code Components
   extracted from this document must include Simplified BSD License text
   as described in Section 4.e of 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.  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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