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SFC  Working Group                                             G. Mirsky
Internet-Draft                                                 ZTE Corp.
Intended status: Standards Track                             G. Fioccola
Expires: April 13, 2019                              Huawei Technologies
                                                              T. Mizrahi
                                        Huawei Network.IO Innovation Lab
                                                        October 10, 2018


 Performance Measurement (PM) with Alternate Marking Method in Service
                     Function Chaining (SFC) Domain
                       draft-mirsky-sfc-pmamm-06

Abstract

   This document describes how the alternate marking method be used as
   the passive performance measurement method 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
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   This Internet-Draft will expire on April 13, 2019.

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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   include Simplified BSD License text as described in Section 4.e of



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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 . . . . . . . . . . . . . .   2
     2.1.  Terminology . . . . . . . . . . . . . . . . . . . . . . .   2
     2.2.  Requirements Language . . . . . . . . . . . . . . . . . .   3
   3.  Mark Field in NSH Base Header . . . . . . . . . . . . . . . .   3
   4.  Theory of Operation . . . . . . . . . . . . . . . . . . . . .   3
     4.1.  Single Mark Enabled Measurement . . . . . . . . . . . . .   4
     4.2.  Double Mark Enabled Measurement . . . . . . . . . . . . .   5
     4.3.  Multiplexed Mark Enabled Measurement  . . . . . . . . . .   5
     4.4.  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 . . . . . . . . . . . . . . . . . . .   6
   7.  Acknowledgment  . . . . . . . . . . . . . . . . . . . . . . .   7
   8.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   7
     8.1.  Normative References  . . . . . . . . . . . . . . . . . .   7
     8.2.  Informative References  . . . . . . . . . . . . . . . . .   7
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   7

1.  Introduction

   [RFC7665] introduced architecture of a Service Function Chain (SFC)
   in the network and defined its components as classifier, Service
   Function Forwarder (SFF), and Service Function (SF).  [RFC8321]
   describes the passive 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 method often referred to as Alternate Marking Method
   (AMM).

   This document defines how the alternate marking method can be used to
   measure packet loss and delay metrics of a service flow over e2e or
   any segment of the SFC.

2.  Conventions used in this document

2.1.  Terminology

   MM: Marking Method

   OAM: Operations, Administration and Maintenance




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   SFC: Service Function Chain

   SF: Service Function

   SFF: Service Function Forwarder

   SFP: Service Function Path

   NSH: Network Service Header

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  |R|R|R|R|MD Type|     Proto     |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                         Figure 1: NSH Base format

   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 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.
   Because the setting of the field to any value does not affect
   forwarding and/or quality of service treatment of a packet, the
   alternate marking method in SFC layer can be viewed as a real example
   of passive performance measurement method.

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 component of the SFC at either ingress or egress




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   point to perform node, link, segment or end-to-end measurement to
   detect performance degradation defect and localize it efficiently.


                   +---+  +---+   +---+  +---+   +---+  +---+
                   |SF1|  |SF2|   |SF3|  |SF4|   |SF5|  |SF6|
                   +---+  +---+   +---+  +---+   +---+  +---+
                      \   /          \  /           \  /
      +----------+   +----+         +----+         +----+
      |Classifier|---|SFF1|---------|SFF2|---------|SFF3|
      +----------+   +----+         +----+         +----+


                           Figure 2: SFC network

   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.

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 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 Loss flag is used to create alternate flows to measure the packet
   loss by switching the value of the Loss 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:

   o  First/Last Packet Delay calculation: whenever the marking, i.e.,
      the value of Loss 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 order of arrival, this method is
      sensitive to packet loss and re-ordering of packets

   o  Average Packet Delay calculation: an average delay is calculated
      by considering the average arrival time of the packets within a
      single block.  A component of the SFC may collect timestamps for



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      each packet received within a single block.  Average of the
      timestamp 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
      also to 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.  Double Mark Enabled Measurement

   Double Mark method allows measurement of minimum and maximum delays
   for the monitored flow, but it requires more nodal and network
   resources.  If the Double Mark method used, then the Loss flag MUST
   be used to create the alternate flow, i.e., mark larger batches of
   packets.  The Delay flag MUST be used to denote single packets to
   measure delay jitter.

   The first marking (Loss flag alternation) is needed for packet loss
   and also for average delay measurement.  The second marking (Delay
   flag is put to one) creates a new set of marked packets that are
   fully identified over the SFC, so that a component can store the
   timestamps of these packets; these timestamps can be compared with
   the timestamps of the same packets on another element of the SFC to
   compute packet delay values for each packet.  The number of
   measurements can be easily increased by changing the frequency of the
   second marking.  But the rate of the second marking must be not too
   high to avoid out of order issues.  This method supports the
   calculation of not only the average delay but also the minimum and
   maximum delay values and, in broader terms, to know more about the
   statistic distribution of delay values.

4.3.  Multiplexed Mark Enabled Measurement

   There is also a scheme that provides the benefits of Double Mark
   method, but uses only one bit like Single Mark.  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 L flag, a single packet has the L flag inverted.  So, by
   examining the stream, the packets with the inverted bit can be easily
   identified and employed for delay measurement.  This Alternate
   Marking variation is advantageous because it requires only one bit
   from each packet, and such bits are always in short supply.






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4.4.  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 of SFFs that compose 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 measurement period, as well as mean,
   median, percentile.  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 SFC end-
   to-end.  For example, the alternate marking method 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

6.  Security Considerations

   This document lists the OAM requirement for SFC domain and does not
   raise any security concerns or issues in addition to ones common to
   networking and SFC.








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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.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",
              draft-mizrahi-ippm-compact-alternate-marking-03 (work in
              progress), October 2018.

   [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>.

   [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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   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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