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Versions: 00 01

IPPM Working Group                                                X. Min
Internet-Draft                                                D. Zhanwei
Intended status: Standards Track                                     ZTE
Expires: April 15, 2018                                 October 12, 2017


              TWAMP Extensions for Direct Loss Measurement
                draft-xiao-ippm-twamp-ext-direct-loss-01

Abstract

   This document describes an optional extension for Two-Way Active
   Measurement Protocol (TWAMP) allowing direct loss measurement of IP
   traffic with the TWAMP-Test protocol.

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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   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 15, 2018.

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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   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.





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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Conventions Used in This Document . . . . . . . . . . . .   2
       1.1.1.  Terminology . . . . . . . . . . . . . . . . . . . . .   2
       1.1.2.  Requirements Language . . . . . . . . . . . . . . . .   3
   2.  TWAMP-Control Extension . . . . . . . . . . . . . . . . . . .   3
     2.1.  Connection Setup with Direct Loss Measurement Mode  . . .   3
   3.  TWAMP-Test Extensions . . . . . . . . . . . . . . . . . . . .   3
     3.1.  Sender Test Packet Format and Content . . . . . . . . . .   4
     3.2.  Reflector Test Packet Format and Content  . . . . . . . .   6
     3.3.  Traffic Loss Calculation  . . . . . . . . . . . . . . . .  10
   4.  Operational Guide . . . . . . . . . . . . . . . . . . . . . .  11
   5.  Security Considerations . . . . . . . . . . . . . . . . . . .  11
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  11
   7.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  11
   8.  Normative References  . . . . . . . . . . . . . . . . . . . .  11
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  12

1.  Introduction

   The Two-Way Active Measurement Protocol (TWAMP) [RFC5357] is an
   extension of the One-Way Active Measurement Protocol (OWAMP)
   [RFC4656].  The TWAMP is a well-defined protocol which is widely used
   for measurement of two-way or round-trip metrics, in addition to the
   one-way metrics of OWAMP.

   When TWAMP or OWAMP is used for measurement of metric loss, it
   actually measures the loss of test packets, so it's a kind of
   "synthetic" loss measurement.  In some cases, considering the IP
   traffic loss characteristics of short-time burst loss, it's expected
   to get more accurate loss measurement results when measuring the
   direct loss of IP traffic instead of test packets.

   To address this, this document describes an optional and simple
   feature for TWAMP, which allows TWAMP-Test protocol to be used for
   direct loss measurement of IP traffic.

1.1.  Conventions Used in This Document

1.1.1.  Terminology

   DSCP: Differentiated Services Code Point

   IPPM: IP Performance Metrics

   TWAMP: Two-Way Active Measurement Protocol




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   OWAMP: One-Way Active Measurement Protocol

   UDP: User Datagram Protocol

1.1.2.  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.

2.  TWAMP-Control Extension

   TWAMP connection establishment follows the procedure defined in
   Section 3.1 of [RFC4656] and Section 3.1 of [RFC5357] where the Modes
   field is used to identify and select specific communication
   capabilities.  At the same time, the Modes field is recognized and
   used as an extension mechanism [RFC6038].  The new feature requires a
   new flag, Direct Loss Measurement flag, to identify the ability of
   both Session-Sender and Session-Reflector to perform direct loss
   measurement, and to support the new Session-Sender packet format and
   the new Session-Reflector packet format in the TWAMP-Test protocol.
   See Section 6 for details on the assigned bit position.

2.1.  Connection Setup with Direct Loss Measurement Mode

   The Server sets the Direct Loss Measurement flag in the Modes field
   of the Server Greeting message to indicate its capability and
   willingness to perform it.  If the Control-Client agrees to perform
   direct loss measurement on some or all test sessions invoked with
   this control connection, it MUST set the Direct Loss Measurement flag
   in the Modes field in the Setup Response message.

3.  TWAMP-Test Extensions

   The TWAMP-Test protocol is similar to the OWAMP [RFC4656] test
   protocol with the exception that the Session-Reflector transmits test
   packets to the Session-Sender in response to each test packet it
   receives.  TWAMP, see Section 4 of [RFC5357], defines two additional
   test packet formats for packets transmitted by the Session-Reflector.
   The appropriate format depends on the security mode chosen.  The new
   mode specified in this document adds counter(s) of IP traffic packets
   into each test packet format.

   When the Server and Control-Client have agreed to use the direct loss
   measurement mode during control connection setup, then the Session-




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   Sender and the Session-Reflector SHOULD all conform to the
   requirements of that mode, as identified below.

3.1.  Sender Test Packet Format and Content

   Formats of the test packet transmitted by the Session-Sender in
   unauthenticated, authenticated, and encrypted modes have been defined
   in Section 4.1.2 of [RFC4656] (as indicated in Section 4.1.2 of
   [RFC5357]).  For the Session-Sender that supports direct loss
   measurement, these formats are displayed in Figures 1 and 2.

   For unauthenticated mode:


    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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                        Sequence Number                        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                          Timestamp                            |
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |        Error Estimate         |           MBZ                 |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                     Sender Tx Couter(S_TxC)                   |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   .                                                               .
   .                         Packet Padding                        .
   .                                                               .
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


       Figure 1: Session-Sender Test Packet Format with direct loss
                    measurement in Unauthenticated Mode

   For authenticated and encrypted modes:














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    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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                        Sequence Number                        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                                                               |
   |                        MBZ (12 octets)                        |
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                          Timestamp                            |
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |        Error Estimate         |                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+                               +
   |                         MBZ (6 octets)                        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                  Sender Tx Counter(S_TxC)                     |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                                                               |
   |                        MBZ (12 octets)                        |
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                                                               |
   |                       HMAC (16 octets)                        |
   |                                                               |
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                                                               |
   .                                                               .
   .                        Packet Padding                         .
   .                                                               .
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


       Figure 2: Session-Sender Test Packet Format with Direct Loss
             Measurement in Authenticated and Encrypted Modes

   The Sender Tx Counter (S_TxC) is set to the number of IP packets of
   the particular monitored flow transmitted towards the Reflector.
   Section 4 provides operational guide on how to determine the scope of
   IP traffic packets that need to be counted.  Note that the Sender
   test packets are not counted.

   In authenticated and encrypted modes, the S_TxC is followed by a new
   12 octets MBZ (MUST be zero) field to make it 16-octet aligned, which
   is required for authentication and encryption.




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   The intention of embedding S_TxC in the Session-Sender test packets
   is for the Session-Sender to calculate direct loss of IP traffic, and
   the loss calculation algorithm is described in Section 3.3.

   The new direct loss measurement mode defined in this document and the
   two extended TWAMP modes defined in [RFC6038] can be selected
   simultaneously.

   When the Symmetrical Size mode defined in [RFC6038] is also selected,
   S_TxC SHOULD be embedded in the Session-Sender Packet formatted in
   Section 5.1.4 of [RFC6038], with the same position as depicted in
   Figure 1.

   When the Reflect Octets mode defined in [RFC6038] is also selected,
   S_TxC SHOULD be embedded in the Session-Sender Packet formatted in
   Section 5.1.2 of [RFC6038], with the same position as depicted in
   Figure 1.

   When both the Symmetrical Size mode and the Reflect Octets mode are
   also selected, S_TxC SHOULD be embedded in the Session-Sender Packet
   formatted in Section 5.1.5 of [RFC6038], with the same position as
   depicted in Figure 1.

3.2.  Reflector Test Packet Format and Content

   Formats of the test packet transmitted by the Session-Reflector in
   unauthenticated, authenticated, and encrypted modes have been defined
   in Section 4.2.1 of [RFC5357].  For the Session-Reflector that
   supports direct loss measurement, these formats are displayed in
   Figures 3 and 4.

   For unauthenticated mode:



















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   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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                        Sequence Number                        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                          Timestamp                            |
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |         Error Estimate        |           MBZ                 |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                       Receive Timestamp                       |
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                     Sender Sequence Number                    |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                       Sender Timestamp                        |
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |      Sender Error Estimate    |           MBZ                 |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |  Sender TTL   |                MBZ                            |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-|
   |                    Sender Tx couter(S_TxC )                   |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-|
   |                   Reflector Rx couter(R_RxC)                  |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-|
   |                   Reflector Tx couter(R_TxC)                  |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-|
   .                                                               .
   .                         Packet Padding                        .
   .                                                               .
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


      Figure 3: Session-Reflector Test Packet Format with direct loss
                    measurement in Unauthenticated Mode

   For authenticated and encrypted modes:


   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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                        Sequence Number                        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                        MBZ (12 octets)                        |
   |                                                               |



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   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                          Timestamp                            |
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |         Error Estimate        |                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+                               +
   |                        MBZ (6 octets)                         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                        Receive Timestamp                      |
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                        MBZ (8 octets)                         |
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                     Sender Sequence Number                    |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                        MBZ (12 octets)                        |
   |                                                               |
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                      Sender Timestamp                         |
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |      Sender Error Estimate    |                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+                               +
   |                        MBZ (6 octets)                         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |  Sender TTL   |                                               |
   +-+-+-+-+-+-+-+-+                                               +
   |                                                               |
   |                                                               |
   |                        MBZ (15 octets)                        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                 Sender Tx Counter(S_TxC)                      |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                                                               |
   |                        MBZ (12 octets)                        |
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                Reflector Rx Counter(R_RxC)                    |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                                                               |
   |                        MBZ (12 octets)                        |
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                Reflector Tx Counter(R_TxC)                    |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+



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   |                                                               |
   |                        MBZ (12 octets)                        |
   |                                                               |
   +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
   |                        HMAC (16 octets)                       |
   |                                                               |
   |                                                               |
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-|
   .                                                               .
   .                         Packet Padding                        .
   .                                                               .
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


      Figure 4: Session-Reflector Test Packet Format with Direct Loss
             Measurement in Authenticated and Encrypted Modes

   The Sender Tx Counter (S_TxC) is copied from the received Sender Test
   Packet.

   The Reflector Rx Counter (R_RxC) is set to the number of IP traffic
   packets received by the Reflector.  Section 4 provides operational
   guide on how to determine the scope of IP traffic packets that need
   to be counted.  Note that the Sender test packets are not counted.

   The Reflector Tx Counter (R_TxC) is set to the number of IP traffic
   packets transmitted towards the Sender.  Section 4 provides
   operational guide on how to determine the scope of IP traffic packets
   that need to be counted.  Note that the Reflector test packets are
   not counted.

   In authenticated and encrypted modes, the S_TxC, R_RxC and R_TxC are
   respectively followed by a new 12 octets MBZ (MUST be zero) field to
   make it 16-octet aligned, which is required for authentication and
   encryption.

   The intention of embedding S_TxC, R_RxC and R_TxC in the Session-
   Reflector test packets is for the Session-Sender to calculate direct
   loss of IP traffic, and the loss calculation algorithm is described
   in Section 3.3.

   When the Symmetrical Size mode defined in [RFC6038] is also selected,
   basing on what's specified in Section 5.2.2 of [RFC6038], the
   Session-Reflector packet format would follow Figure 3.





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   When the Reflect Octets mode defined in [RFC6038] is also selected,
   S_TxC, R_RxC and R_TxC SHOULD be embedded in the Session-Reflector
   Packet formatted in Section 5.2.1 of [RFC6038], with the same
   position as depicted in Figure 3.

   When both the Symmetrical Size mode and the Reflect Octets mode are
   also selected, S_TxC, R_RxC and R_TxC SHOULD be embedded in the
   Session- Reflector Packet formatted in Section 5.2.1 of [RFC6038],
   with the same position as depicted in Figure 3.

3.3.  Traffic Loss Calculation

   Upon receiving a Reflector Test Packet, the Session-Sender uses the
   following values to make loss calculation:

   o Received S_TxC, R_RxC and R_TxC values embedded in Reflector Test
   Packet and local counter S_RxC value at the time this Reflector Test
   Packet was received.  These values are represented as S_TxC[n],
   R_RxC[n], R_TxC[n], and S_RxC[n], where n is the reception time of
   the current Reflector Test Packet.

   o Previous Received S_TxC, R_RxC and R_TxC values embedded in
   Reflector Test Packet and local counter S_RxC value at the time the
   previous Reflector Test Packet was received.  These values are
   represented as S_TxC[n-1], R_RxC[n-1], R_TxC[n-1], and S_RxC[n-1],
   where n-1 is the reception time of the previous Reflector Test
   Packet.

   The formulas for calculating the far-end loss, near-end loss, far-end
   loss rate and near-end loss rate are as following:

   o Far-end loss: F_Loss[n-1,n] = (S_TxC[n]-S_TxC[n-1])-(R_RxC[n]-
   R_RxC[n-1])

   o Near-end loss: N_Loss[n-1,n] = (R_TxC[n]-R_TxC[n-1])-(S_RxC[n]-
   S_RxC[n-1])

   o Far-end loss rate: F_LossRate[n-1,n] = F_Loss[n-1,n]/(S_TxC[n]-
   S_TxC[n-1])

   o Near-end loss rate: N_LossRate[n-1,n] = N_Loss[n-1,n]/(R_TxC[n]-
   R_TxC[n-1])

   Here far-end means the direction from the Session-Sender to the
   Session-Reflector and near-end means the direction from the Session-
   Reflector to the Session-Sender.





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4.  Operational Guide

   In order to make meaningful loss measurement, in general, the scope
   of IP traffic packets that need to be counted, i.e. the IP traffic
   packets counting rules, should be provisioned before starting Test
   Sessions, and the provisioned arguments usually include ingress port,
   source IP address, destination IP address, IP DSCP and UDP port
   number.  For the scenarios where the exact source/destination IP
   address and IP DSCP of IP traffic can be known, such as mobile
   backhaul, the Test Packets should use the same source/destination IP
   address and IP DSCP as IP traffic, and it shall result in more
   accurate measurements.

5.  Security Considerations

   Use of direct loss measurement in a test session does not appear to
   introduce any additional security threat to hosts that communicate
   with TWAMP as defined in [RFC5357].  The security considerations that
   apply to any active measurement of live networks are relevant here as
   well.  See the Security Considerations sections in [RFC4656] and
   [RFC5357].

6.  IANA Considerations

   In the TWAMP-Modes registry defined in [RFC5618], a new Direct Loss
   Measurement Capability is requested from IANA as follows:

   +--------+--------------------------+------------------+------------+
   | Bit    | Description              | Semantics        | Reference  |
   | Pos    |                          | Definition       |            |
   +--------+--------------------------+------------------+------------+
   | 10     | Direct Loss Measurement  | Section 2        | This       |
   |        | Capability               |                  | Document   |
   +--------+--------------------------+------------------+------------+

              Table 1: New Direct Loss Measurement Capability

7.  Acknowledgements

   The authors would like to thank Greg Mirsky and Guo Jun for their
   valuable comments.

8.  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>.



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   [RFC4656]  Shalunov, S., Teitelbaum, B., Karp, A., Boote, J., and M.
              Zekauskas, "A One-way Active Measurement Protocol
              (OWAMP)", RFC 4656, DOI 10.17487/RFC4656, September 2006,
              <https://www.rfc-editor.org/info/rfc4656>.

   [RFC5357]  Hedayat, K., Krzanowski, R., Morton, A., Yum, K., and J.
              Babiarz, "A Two-Way Active Measurement Protocol (TWAMP)",
              RFC 5357, DOI 10.17487/RFC5357, October 2008,
              <https://www.rfc-editor.org/info/rfc5357>.

   [RFC5618]  Morton, A. and K. Hedayat, "Mixed Security Mode for the
              Two-Way Active Measurement Protocol (TWAMP)", RFC 5618,
              DOI 10.17487/RFC5618, August 2009,
              <https://www.rfc-editor.org/info/rfc5618>.

   [RFC6038]  Morton, A. and L. Ciavattone, "Two-Way Active Measurement
              Protocol (TWAMP) Reflect Octets and Symmetrical Size
              Features", RFC 6038, DOI 10.17487/RFC6038, October 2010,
              <https://www.rfc-editor.org/info/rfc6038>.

   [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>.

Authors' Addresses

   Xiao Min
   ZTE
   Nanjing
   CN

   Phone: +86 25 88016576
   Email: xiao.min2@zte.com.cn


   Dou Zhanwei
   ZTE
   Nanjing
   CN

   Phone: +86 25 52874656
   Email: dou.zhanwei@zte.com.cn









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