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SFC  Working Group                                             G. Mirsky
Internet-Draft                                                 ZTE Corp.
Intended status: Standards Track                             G. Fioccola
Expires: October 25, 2017                                 Telecom Italia
                                                          April 23, 2017


 Performance Measurement (PM) with Alternate Marking Method in Service
                     Function Chaining (SFC) Domain
                       draft-mirsky-sfc-pmamm-00

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

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   This Internet-Draft will expire on October 25, 2017.

Copyright Notice

   Copyright (c) 2017 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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   described in the Simplified BSD License.



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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 . . . . . . . . . . . . . . . . . . . . .   4
     4.1.  Single Mark Enabled Measurement . . . . . . . . . . . . .   4
     4.2.  Double Mark Enabled Measurement . . . . . . . . . . . . .   5
   5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   5
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .   6
   7.  Acknowledgement . . . . . . . . . . . . . . . . . . . . . . .   6
   8.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   6
     8.1.  Normative References  . . . . . . . . . . . . . . . . . .   6
     8.2.  Informative References  . . . . . . . . . . . . . . . . .   6
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   7

1.  Introduction

   [RFC7665] introduced architecture of a Service Function Chain (SFC)
   in the network and defined its components as classifier, Sevice
   Function Forwarder (SFF), and Service Function (SF).
   [I-D.ietf-ippm-alt-mark] describes 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 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

   SFC: Service Function Chain

   SF: Service Function

   SFF: Service Function Forwarder

   SFP: Service Function Path



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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
   [RFC2119].

3.  Mark Field in NSH Base Header

   [I-D.ietf-sfc-nsh] defines format of the Network Service Header
   (NSH).  The format of NSH Base is presented in Figure 1.

      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|R|    TTL    |   Length  |R|R|R|R|MD Type|     Proto     |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


                         Figure 1: NSH Base format

   This document defines two bit long field, referred as Mark field, as
   part of NSH Base and designated for the alternate marking performance
   measurement method [I-D.ietf-ippm-alt-mark].  The Mark field MUST NOT
   be used in defining forwarding and/or quality of service treatment of
   a SFC packet.  The Mark field MUST be used only for the performance
   measurement of data traffic in SFC layer.  Because 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 true example of passive performance
   measurement method.

   The Figure 2 displays format of the Mark field.

    0
    0   1
   +-+-+-+-+
   | S | D |
   +-+-+-+-+

                        Figure 2: Mark field format

   where:

   o  S- Single mark method;

   o  D - Double mark method.




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4.  Theory of Operation

   The marking method can be successfully used in the SFC.  Without
   limiting any generality consider SFC presented in Figure 3.  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
   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 3: 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 [I-D.ietf-ippm-alt-mark], marking can be applied
   to delineate blocks of packets based either on equal number of
   packets in a block or based on equal 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.

   If the Single Mark measurement used, then the D flag MUST be set to
   zero on transmit and ignored by monitoring point.

   The S flag is used to create alternate flows to measure the packet
   loss by switching value of the S flag every N-th packet or at certain
   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.
      value of S flag, changes a component of the SFC can store the
      timestamp of the first/last packet of the block.  The timestamp



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      can be compared with the timestamp of the packet that arrived in
      the same order through a monitoring point at 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
      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 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 single metric for the duration of the block
      and it doesn't give the minimum and maximum delay values.  This
      limitation could be overcome by reducing the duration of the block
      by means of an highly optimized implementation of the method.

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 S flag MUST be
   used to create the alternate flow, i.e. mark larger batches of
   packets.  The D flag MUST be used to mark single packets to measure
   delay jitter.

   The first marking (S flag alternation) is needed for packet loss and
   also for average delay measurement.  The second marking (D flag is
   put to one) creates a new set of marked packets that are fully
   identified over the SFC, so that a componenet can store the
   timestamps of these packets; these timestamps can be compared with
   the timestamps of the same packets on another component 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 frequency of the second marking must be not
   too high in order to avoid out of order issues.  This method is
   useful to have not only the average delay but also the minimum and
   maximum delay values and, in wider terms, to know more about the
   statistic distribution of delay values.

5.  IANA Considerations

   This document requests IANA to register format of the OAM field of
   NSH as the following:




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   +--------------+---------+--------------------------+---------------+
   | Bit Position | Marking | Description              | Reference     |
   +--------------+---------+--------------------------+---------------+
   |      0       |    S    | Single Mark Measurement  | This document |
   |      1       |    D    | Double Mark Measurement  | This document |
   +--------------+---------+--------------------------+---------------+

                     Table 1: OAM field of BIER Header

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.

7.  Acknowledgement

   TBD

8.  References

8.1.  Normative References

   [I-D.ietf-sfc-nsh]
              Quinn, P. and U. Elzur, "Network Service Header", draft-
              ietf-sfc-nsh-12 (work in progress), February 2017.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,
              <http://www.rfc-editor.org/info/rfc2119>.

   [RFC7665]  Halpern, J., Ed. and C. Pignataro, Ed., "Service Function
              Chaining (SFC) Architecture", RFC 7665,
              DOI 10.17487/RFC7665, October 2015,
              <http://www.rfc-editor.org/info/rfc7665>.

8.2.  Informative References

   [I-D.ietf-ippm-alt-mark]
              Fioccola, G., Capello, A., Cociglio, M., Castaldelli, L.,
              Chen, M., Zheng, L., Mirsky, G., and T. Mizrahi,
              "Alternate Marking method for passive performance
              monitoring", draft-ietf-ippm-alt-mark-04 (work in
              progress), March 2017.






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Authors' Addresses

   Greg Mirsky
   ZTE Corp.

   Email: gregimirsky@gmail.com


   Giuseppe Fioccola
   Telecom Italia

   Email: giuseppe.fioccola@telecomitalia.it







































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