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Network Working Group                                            M. Chen
Internet-Draft                                                  A. Malis
Intended status: Standards Track                                  Huawei
Expires: April 26, 2019                                 October 23, 2018


          DetNet Packet Loss and Delay Performance Measurement
                    draft-chen-detnet-loss-delay-01

Abstract

   Deterministic Networking (DetNet) is defined to provide end-to-end
   bounded latency and extremely low packet loss rates for critical
   flows.  It's important to measure and monitor the packet loss rates
   and end-to-end delay and delay variation of a DetNet flow path, which
   allows evaluation of whether the Service Level Agreements (SLA) of
   the provided DetNet services are satisfied.  These metrics are also
   useful in network/traffic planning, trouble shooting, and network
   performance evaluation.

   This document defines protocol mechanisms to support passive
   Performance Measurement (PM) for DetNet service.

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
   BCP14 [RFC2119][RFC8174] when, and only when, they appear in all
   capitals, as shown here.

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
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at https://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on April 26, 2019.




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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
   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.  DetNet Control Word based PM  . . . . . . . . . . . . . . . .   3
     2.1.  Packet Loss Measurement . . . . . . . . . . . . . . . . .   4
     2.2.  Packet Delay Measurement  . . . . . . . . . . . . . . . .   5
     2.3.  Alternative Solutions to the "D/L" Bits . . . . . . . . .   6
   3.  PM for IP-based Encapsulation . . . . . . . . . . . . . . . .   6
   4.  Extensions to RFC6374 . . . . . . . . . . . . . . . . . . . .   7
     4.1.  Measurement Interval TLV  . . . . . . . . . . . . . . . .   7
     4.2.  DetNet Control Word TLV . . . . . . . . . . . . . . . . .   7
     4.3.  Service Label TLV . . . . . . . . . . . . . . . . . . . .   8
   5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   9
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .   9
   7.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   9
   8.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   9
     8.1.  Normative References  . . . . . . . . . . . . . . . . . .   9
     8.2.  Informative References  . . . . . . . . . . . . . . . . .  10
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  10

1.  Introduction

   Deterministic Networking (DetNet) [I-D.ietf-detnet-architecture] can
   provide end-to-end bounded latency and extremely low packet loss
   rates for critical flows.  This achieved by dedicating network
   resources (e.g., link bandwidth and queue buffering) to DetNet flows,
   and by replicating packets along multiple paths.

   It's important to measure and monitor the packet loss rate and one-
   way delay and delay variation of a DetNet flow path in order to
   evaluate whether the Service Level Agreements (SLA) of the provided
   DetNet services are satisfied.  These metrics are also useful in




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   network/traffic planning, troubleshooting, and network performance
   evaluation.

   As defined in [RFC7799], performance measurement can be classified
   into Active, Passive and Hybrid measurement.  Active measurement is
   performed by injecting Operations, Administration, and Maintenance
   (OAM) packets to the network to estimate the performance of the
   network by measuring the performance of the OAM packets.  However,
   adding extra traffic can affect the quantities to be measured to some
   degree.  On the other hand, passive measurement monitors the actual
   service traffic, rather than injecting OAM packets to estimate the
   traffic performance.  Therefore, Passive performance measurement will
   not affect the behavior of the real DetNet service, and also provide
   more accurate measurement results.  Accordingly, this document
   defines protocol mechanisms to support Passive PM for DetNet
   services.

   DetNet defines two encapsulations, an MPLS-based encapsulation
   [I-D.ietf-detnet-dp-sol-mpls], and an IP-based encapsulation
   [I-D.ietf-detnet-dp-sol-ip].  For the MPLS based encapsulation, a
   service layer is introduced, which is supported by a DetNet Service
   Label (S-Label) and a DetNet Control Word (d-CW).  The S-Label is
   used to identify a DetNet flow.  The d-CW contains a sequence number
   that is designed for supporting the Packet Replication, Elimination,
   and Ordering Functions (PREOF).  When perform packet loss and delay
   measurements, the sequence number can be used for packet accounting
   and packet count/timestamp correlation as well.

   [RFC6374] defines Loss Measurement (LM) and Delay Measurement (DM)
   messages to communicate packet counts, timestamps, and other relevant
   information between Measurement Points (MPs).  This document defines
   three new TLVs to the [RFC6374] LM message and DM messages.  Which
   are used for communicating the correlation information (e.g.,
   sequence number, measurement interval, and service label) that
   enables the packet loss and packet delay calculation.  The detailed
   definitions of these new TLVs are described in Section 3.

2.  DetNet Control Word based PM

   As discussed above, MPLS-based DetNet encapsulation introduces an
   S-Label and a d-CW.  This document defines two new flags in the d-CW
   (as shown in Figure 1).  The L bit is defined to indicate whether the
   loss measurement is enabled, and the D bit is defined to indicate
   whether the delay measurement is enabled.







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           +-----------------+
           ~  IP/MPLS Tunnel ~
           +-----------------+ <--\
           |  Service Label  |    |
           +-----------------+    +-- Service Layer Header
      +----|  Control Word   |    |
      |    +-----------------+ <--/
      |    |     Payload     |
      |    +-----------------+
      |
      |    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      +--->|0 0 0 0|L|D|                 Sequence Number               |
           +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                     Figure 1: DetNet Control Word

   Where:

   o  L bit: Loss measurement indicator; 1 means the loss measurement is
      enabled, otherwise the loss measurement is not enabled.

   o  D bit: Delay measurement indicator;1 means the delay measurement
      is enabled, otherwise the delay measurement is not enabled.  When
      a node receive a packet with D bit set, it will timestamp the
      packet and copy it for further PM processing.

2.1.  Packet Loss Measurement

   Assume a DetNet service path between node A and node B, where node A
   is the ingress node, and node B is the egress node.  To measure the
   number of packets transmitted at node A but not received at node B
   within a measurement interval, there needs a way to determine which
   packets belong to which measurement interval.  [RFC6374] uses OAM
   packets to demarcate different measurement intervals.  However, an
   OAM packet-based solution cannot work when there is packet mis-
   ordering.  This document uses the sequence number to determine to
   which measurement interval a packet belongs.  Specifically, the
   measurement interval number is calculated as the modulo of the
   sequence number and a pre-configured constant.

   o  Measurement Interval = "Sequence Number" mod "Pre-configured
      constant".

   With this, the ingress and egress nodes can use the sequence number
   of a packet to calculate the measurement interval number.  The
   packets with same interval number belong to the same measurement
   interval.  Then the packet loss can be calculated as below:




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   Loss[n] = A_TxP[n] - B_RxP[n], where:

   o  A_TxP[n] is the number of packets transmitted at node A within the
      No. "n" measurement interval;

   o  B_RxP[n] is the number of packets received at node B within the
      No. "n" measurement interval;

   If the calculation is performed at one side of the path, the A_TxP[n]
   or B_RxP[n] needs to be sent to the other side.  The Loss Measurement
   (LM) message defined in [RFC6374] is used to communicate the counts,
   in order to correlate the counts from the ingress node with the
   counts from the egress node.  The extensions to [RFC6374] to
   communicate the measurement interval are defined in Section 3.

   If the calculation is performed at a centralized controller, then the
   A_TxP[n] and B_RxP[n] need to be sent to the controller.  The
   mechanism for sending counts to a centralized controller is out side
   the scope of this document.

2.2.  Packet Delay Measurement

   To measure the delay of a packet, the D bit of the d-CW MUST be set.
   At the ingress node, record the time when sending the packet, with
   the timestamp indexed by the sequence number.  At the egress node,
   when receiving a packet with D bit set, record the time when the
   packet was received, with the timestamp indexed by the sequence
   number.  Then, with the timestamps from the ingress and egress nodes,
   and the sequence number, the packet delay can be calculated as below:

   Delay[n] = B_RxT[n] - A_TxT[n], where:

   o  B_RxT[n] identifies the timestamp at node B when receiving the No.
      "n" packet;

   o  A_TxT[n] identifies the timestamp at node A when sending the No.
      "n" packet;

   Similar to loss measurement, the Delay Measurement (DM) message
   defined in [RFC6374] is used to communicate the timestamps when
   calculation is performed at either side of a DetNet service path.  In
   order to correlate the timestamps from the ingress node with the
   timestamps from the egress node, extensions to [RFC6374] to
   communicate the sequence number and other relevant information are
   needed.  The detailed definitions of these extensions are described
   in Section 3.





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   The mechanism for sending timestamps to a centralized controller is
   out side the scope of this document.

2.3.  Alternative Solutions to the "D/L" Bits

   Configuration can be used to indicate whether the delay and/or loss
   measurements are enabled on a specific DetNet service flow.  This can
   be done by through the DetNet configuration model
   [I-D.geng-detnet-conf-yang], a PCEP extension, a Command Line
   Interface (CLI), or other means.

   Another way is to use the signalling protocol as the enabler of
   performance measurement.  More detail will be added in the future.

   [Editor notes:

   This document introduces three ways (as summarized below) to enable
   PM on a DetNet flow.  We'd like to solicit more inputs and comments
   from the WG:

   1.  Indicated by the "D/L" bits: A straightforward way to indicate
       when to measure, which packets to measured.  The cost is to take
       two bits (or at least one bit) away from the sequence number.

   2.  Configured by CLI or YANG: Normally, it's easy to enable/disable
       PM on a DetNet flow.  The receiving node may take more time
       (e.g., by matching a local configuration item to determine) to
       determine whether a packet should be counted, whether a packet
       should be timestamped.  And it is difficult to support if only
       partial packets of a flow need to be measured.  This is a common
       case for packet delay measurement, where sample measurement is
       acceptable and reasonable.

   3.  Signalled by control protocol: The pros and cons similar to
       option 2.

   ]

3.  PM for IP-based Encapsulation

   For IP-based encapsulation, since there is no service layer, the d-
   CW-based solution as defined in Section 2 can not be applied.  The
   marking-based solution defined in [RFC8321] can be used.  More detail
   will be added in future versions.







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4.  Extensions to RFC6374

   [RFC6374] defines how to communicate the packet counts and timestamps
   between measurement points.  In order to support passive PM, this
   document defines several new TLVs to carry the correlation
   information.  The correlation information can be used to determine
   with which DetNet service path a packet count/timestamp correlates,
   and with which measurement interval a packet count correlates, and
   with which packet a timestamp correlates.

   Three new TLVs to LM and DM messages [RFC6374] are defined in the
   following sub-sections.

4.1.  Measurement Interval TLV

   This document defines a new TLV which is referred to as Measurement
   Interval TLV to Loss Measurement message [RFC6374].  The Measurement
   Interval TLV carries the measurement interval that is used to
   correlate the packet counts from the ingress node with the packet
   counts from the egress nodes.  Then the packet loss can be calculated
   as described in Section 2.

   The format of the Measurement Interval TLV is as below:

      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
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |             Type (TBD1)       |            Length             |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                     Measurement Interval                      |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                    Figure 2: Measurement Interval TLV

   Where:

   o  The Type field is two octets in length, and the value is TBD1.

   o  The Length field is two octets in length, with a value is 4,
      indicating the length of the Measurement Interval field.

   o  The Measurement Interval field is 4 octets in length, and carries
      the measurement interval.

4.2.  DetNet Control Word TLV

   This document defines a new TLV which is referred to as DetNet
   Control Word TLV to Delay Measurement message [RFC6374].  The
   sequence number of the d-CW is used to correlate the timestamps from



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   the ingress node with the timestamp from the egress node.  Then the
   packet delay can be calculated as described in Section 2.

   The format of the DetNet Control Word TLV is as below:

      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
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |             Type (TBD2)       |            Length             |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                   DetNet Control Word                         |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                    Figure 3: DetNet Control Word TLV

   Where:

   o  The Type field is two octets in length, and the value is TBD2.

   o  The Length field is two octets in length, with a value is 4,
      indicating the length of the DetNet Control Word field.

   o  The DetNet Control Word is 4 octets in length.

4.3.  Service Label TLV

   This document defines a new TLV which is referred to as Service Label
   TLV to Loss Measurement message and Delay Measurement message
   [RFC6374].  The Service Label TLV carries the DetNet S-Label that is
   allocated by the receiving node to the DetNet service path that is
   being measured.  Here, the receiving node can be the egress node, or
   an relay node.  The S-Label is used to determine to which DetNet
   service path the packet counts/timestamps belong.

   The format of the Service Label TLV is as below:

      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
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |             Type (TBD3)       |            Length             |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |       Reserved        |          Service Label                |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                    Figure 4: Service Label TLV

   Where:

   o  The Type field is two octets in length, and the value is TBD3.




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   o  The Length field is two octets in length, with a value is 4,
      indicating the length of the Reserved and the Service Label
      fields.

   o  The Service Label field is 20-bit in length.

5.  IANA Considerations

   IANA is requested to allocate the following TLV types from the "MPLS
   Loss/Delay Measurement TLV Object" sub-registry of the "Generic
   Associated Channel (G-ACh) Parameters" registry:

      Type Description                       Reference
      ---- --------------------------------- ---------
      TBD1 Measurement Interval              This document
      TBD2 DetNet Control Word               This document
      TBD3 DetNet Service Label              This document

6.  Security Considerations

   This document enables the use of Passive monitoring to determine the
   SLA conformance of DetNet service flows, and does not introduce any
   additional Active monitoring packets to the network.  As a result,
   this document introduces no new security considerations beyond those
   already described in Section 8 of [RFC6374] and Section 5 of
   [RFC7799].

7.  Acknowledgements

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>.

   [RFC6374]  Frost, D. and S. Bryant, "Packet Loss and Delay
              Measurement for MPLS Networks", RFC 6374,
              DOI 10.17487/RFC6374, September 2011,
              <https://www.rfc-editor.org/info/rfc6374>.

   [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>.





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8.2.  Informative References

   [I-D.geng-detnet-conf-yang]
              Geng, X., Chen, M., Li, Z., and R. Rahman, "DetNet
              Configuration YANG Model", draft-geng-detnet-conf-yang-06
              (work in progress), October 2018.

   [I-D.ietf-detnet-architecture]
              Finn, N., Thubert, P., Varga, B., and J. Farkas,
              "Deterministic Networking Architecture", draft-ietf-
              detnet-architecture-09 (work in progress), October 2018.

   [I-D.ietf-detnet-dp-sol-ip]
              Korhonen, J. and B. Varga, "DetNet IP Data Plane
              Encapsulation", draft-ietf-detnet-dp-sol-ip-01 (work in
              progress), October 2018.

   [I-D.ietf-detnet-dp-sol-mpls]
              Korhonen, J. and B. Varga, "DetNet MPLS Data Plane
              Encapsulation", draft-ietf-detnet-dp-sol-mpls-01 (work in
              progress), October 2018.

   [I-D.ietf-detnet-use-cases]
              Grossman, E., "Deterministic Networking Use Cases", draft-
              ietf-detnet-use-cases-19 (work in progress), October 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>.

   [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

   Mach(Guoyi) Chen
   Huawei

   Email: mach.chen@huawei.com


   Andrew G. Malis
   Huawei

   Email: agmalis@gmail.com



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