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Versions: 00 01 02 03

IP Performance Measurement Group                                 Y. Wang
Internet-Draft                                                   T. Zhou
Intended status: Standards Track                                  Huawei
Expires: May 19, 2021                                            H. Yang
                                                            China Mobile
                                                                  C. Liu
                                                            China Unicom
                                                       November 15, 2020


Simple Two-way Active Measurement Protocol Extensions for Hop-by-Hop OAM
                            Data Collection
                draft-wang-ippm-stamp-hbh-extensions-02

Abstract

   This document defines optional TLVs which are carried in Simple Two-
   way Active Measurement Protocol (STAMP) test packets to enhance the
   STAMP base functions.  Such extensions to STAMP enable OAM data
   measurement and collection at every node and link along a STAMP test
   packet's delivery path without maintaining a state for each
   configured STAMP-Test session at every devices.

Requirements Language

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in RFC 2119 [RFC2119].

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 May 19, 2021.






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Copyright Notice

   Copyright (c) 2020 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.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   3
   3.  TLV Extensions to STAMP . . . . . . . . . . . . . . . . . . .   3
     3.1.  IOAM Tracing Data TLV . . . . . . . . . . . . . . . . . .   3
     3.2.  Forward HbH Delay TLV . . . . . . . . . . . . . . . . . .   5
     3.3.  Backward HbH Delay TLV  . . . . . . . . . . . . . . . . .   7
     3.4.  HbH Packet Loss TLV . . . . . . . . . . . . . . . . . . .   9
     3.5.  HbH Bandwidth Utilization TLV . . . . . . . . . . . . . .  11
     3.6.  HbH Timestamp Information TLV . . . . . . . . . . . . . .  12
   4.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  14
   5.  Security Considerations . . . . . . . . . . . . . . . . . . .  14
   6.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  15
   7.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  15
     7.1.  Normative References  . . . . . . . . . . . . . . . . . .  15
     7.2.  Informative References  . . . . . . . . . . . . . . . . .  15
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  15

1.  Introduction

   Simple Two-way Active Measurement Protocol (STAMP) [RFC8762] enables
   the measurement of both one-way and round-trip performance metrics,
   such as delay, delay variation, and packet loss.  In the STAMP
   session, the bidirectional packet flow is transmitted between STAMP
   Session-Sender and STAMP Session-Reflector.  The STAMP Session-
   Reflector receives test packets transmitted from Session-Sender and
   acts according to the configuration.  However, the performance of
   intermediate nodes and links that STAMP test packets traverse are
   invisible.  In addition, the STAMP instance must be configured at
   every intermediate node to measure the performance per node and link
   that test packets traverse, which increases the complexity of OAM in
   large-scale networks.



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   STAMP Extensions have defined several optional TLVs to enhance the
   STAMP base functions.  These optional TLVs are defined as updates of
   the STAMP Optional Extensions [I-D.ietf-ippm-stamp-option-tlv].  This
   document extents optional TLVs to STAMP, which enables performance
   measurement at every intermediate node and link along a STAMP test
   packet's delivery path, such as measurement of delay, delay
   variation, packet loss, and record of route information.  The
   following sections describe the use of TLVs for STAMP that extend
   STAMP capability beyond its base specification.

2.  Terminology

   Following are abbreviations used in this document:

   STAMP: Simple Two-way Active Measurement Protocol.

   IOAM: In-situ OAM.

   HbH: Hop-by-Hop.

3.  TLV Extensions to STAMP

3.1.  IOAM Tracing Data TLV

   STAMP Session-Sender MAY place the IOAM Tracing Data TLV in Session-
   Sender test packets to record the IOAM tracing data at every IOAM
   capable node along the Session-Sender test packet's forward-delivery
   path.  As STAMP uses symmetrical packets, the Session-Sender MUST set
   the Length value as a multiple of 4 octets according to the number of
   nodes and the IOAM-Trace-Type (i.e. a 24-bit identifier which
   specifies which data types are used in the node data list
   [I-D.ietf-ippm-ioam-data]).  And the node-data-copied-list fields
   MUST be set to zero upon Session-Sender test packets transmission and
   ignored upon receipt.

   The IOAM Tracing Data TLV has the following format:















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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
   +-------------------------------+-------------------------------+
   |   IOAM-Tracing-Data Type      |            Length             |
   +---------------------------------------------------------------+
   |                    node data copied list [0]                  |
   +---------------------------------------------------------------+
   |                    node data copied list [1]                  |
   +---------------------------------------------------------------+
   ~                               ...                             ~
   +---------------------------------------------------------------+
   |                    node data copied list [n]                  |
   +---------------------------------------------------------------+


                    Fig. 1 IOAM Tracing Data TLV Format

   where fields are defined as the following:

   o  IOAM-Tracing-Data Type: To be assigned by IANA.

   o  Length: A 2-octet field that indicates the length of the value
      field in octets and equal to a multiple of 4 octets dependent on
      the number of nodes and IOAM-Trace-Type bits.

   o  node data copied list [0..n]: A variable-length field, which
      record the copied content of each node data element determined by
      the IOAM-Trace-Type.  The order of packing the data fields in each
      node data element follows the bit order of the IOAM-Trace-Type
      field (see section 4.4.1 of [I-D.ietf-ippm-ioam-data]).  The last
      node data element in this list is the node data of the first IOAM
      trace capable node in the path.

   In an IOAM domain, the STAMP Session-Sender and the STAMP Session-
   Reflector MAY be configured as the IOAM encapsulating node and the
   IOAM decapsulating node.  The STAMP Session-Sender (i.e. the IOAM
   encapsulating node) generates the test packet with the IOAM Tracing
   Data TLV.  For applying the IOAM Trace-Option functionalities to the
   Session-Sender test packet, the Session-Sender must inserts the
   "trace option header" and allocate an node-data-list array
   [I-D.ietf-ippm-ioam-data] into "option data" fields of Hop-by-Hop
   Options header in IPv6 packets [I-D.ietf-ippm-ioam-ipv6-options], and
   sets the corresponding bits in the IOAM-Trace-Type.  Also, the STAMP
   Session-Sender allocates a node-data-copied-list array in the
   optional IOAM Tracing Data TLV to store OAM data retrieved from every
   IOAM transit node along the Session-Sender test packet's delivery
   path.




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   When the STAMP Session-Reflector (i.e. the IOAM decapsulating node)
   received the STAMP Session-Sender test packet with the IOAM-Tracing-
   Data TLV, it MUST copy the node-data-list array into the node-data-
   copied-list array carried in the Session-Reflector test packet before
   transmission and MUST remove the IOAM-Data-Fields.  Hence, carrying
   IOAM-Tracing-Data TLV in STAMP test packets enables OAM data
   collection and measurement at every node and link.

   Also the STAMP Session-Reflector MAY be configured as IOAM
   encapsulating node to apply the IOAM Trace-Option functionalities to
   the Session-Reflector test packet.  Hence, OAM data collection and
   measurement can be also enabled at every node and link along the
   Session-Reflector test packet's backward delivery path.  When the
   reflected packet arrives at the Session-Sender, it can be either
   locally processed or sent to the centralized controller.

   In addition to IOAM, other telemetry data (e.g. alternate marking)
   could be transmitted by STAMP optional TLV extensions.  The draft
   will keep the option open for future augmentations.

3.2.  Forward HbH Delay TLV

   STAMP Session-Sender MAY place the Forward HbH Delay TLV in Session-
   Sender test packets to record the ingress timestamp and the egress
   timestamp at every intermediate nodes along the Session-Sender test
   packet's forward path.  The Session-Sender MUST set the Length value
   according to the number of explicitly listed intermediate nodes in
   the forward path and the timestamp formats.  There are several
   methods to synchronize the clock, e.g., Network Time Protocol (NTP)
   [RFC5905] and IEEE 1588v2 Precision Time Protocol (PTP)
   [IEEE.1588.2008].  For example, if a 64-bit timestamp format defined
   in NTP is used, the Length value MUST be set as a multiple of 16
   octets.  The Timestamp Tuple list [1..n] fields MUST be set to zero
   upon Session-Sender test packets transmission.

   The Forward HbH Delay TLV has the following format:















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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
   +-------------------------------+---------------+---------------+
   |   Forward HbH Delay Type      |     Length    |    Node Left  |
   +-------------------------------+---------------+---------------+
   |                                                               |
   |                     Timestamp Tuple list [1]                  |
   |                                                               |
   |                                                               |
   +---------------------------------------------------------------+
   ~                              ...                              ~
   +---------------------------------------------------------------+
   |                                                               |
   |                     Timestamp Tuple list [n]                  |
   |                                                               |
   |                                                               |
   +---------------------------------------------------------------+

                    Fig. 2 Forward HbH Delay TLV Format

   where fields are defined as the following:

   o  Forward HbH Delay Type: To be assigned by IANA.

   o  Length: A 8-bit field that indicates the length of the value
      portion in octets and MUST be a multiple of 16 octets according to
      the number of explicitly listed intermediate nodes in the forward
      path.

   o  Node Left: A 8-bit unsigned integer, which indicates the number of
      intermediate nodes remaining.  That is, number of explicitly
      listed intermediate nodes still to be visited before reaching the
      destination node in the forward path.  The Node Left field is set
      to n-1, where n is the number of intermediate nodes.

   o  Timestamp Tuple list [1..n]: A variable-length field, which record
      the timestamp when the Session-Sender test packet is received at
      the ingress of the n-th intermediate node Ingress Timestamp [n]
      and the timestamp when the Session-Sender test packet is sent at
      egress of the n-th intermediate node Egress Timestamp [n].  For
      example, if a 64-bit timestamp format defined in NTP is used, the
      length of each Timestamp tuple (Ingress Timestamp [n], Egress
      Timestamp [n]) must be 16 octets.  The Timestamp Tuple list is
      encoded starting from the last intermediate node which is
      explicitly listed.  That is, the first element of the Timestamp
      Tuple list [1] records the timestamps when the Session-Sender test
      packet received and forwarded at the last intermediate node of a
      explicit path, the second element records the penultimate



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      Timestamp Tuple when the Session-Sender test packet received and
      forwarded at the penultimate intermediate node of a explicit path,
      and so on.

   In the following reference topology, Node N1, N2, N3, N4 and N5 are
   SRv6 capable nodes.  Node N1 is the STAMP Session-Sender and Node N5
   is the STAMP Session-Reflector.  T1 is the Timestamp taken by the
   Session-Sender (i.e.  N1) at the start of transmitting the test
   packet.  T2 is the Receive Timestamp when the test packet was
   received by the Session-Reflector (i.e.  N5).  T3 is the Timestamp
   taken by the Session-Reflector at the start of transmitting the test
   packet.  T4 is the Receive Timestamp when the test packet was
   received by the Session-Sender.  Timestamp tuples (t1,t2), (t3,t4)
   and (t5,t6) are the timestamps when the test packet received and
   transmitted by sequence of intermediate nodes in the forward path.
   Timestamp Tuples (t7,t8), (t9,t10) and (t11,t12) are the timestamps
   when the test packet received and transmitted by sequence of
   intermediate nodes in the backward path.


   ======          ======          ======          ======         ======
   |    | T1--->t1 |    | t2--->t3 |    | t4--->t5 |    | t6--->T2|    |
   | N1 |==========| N2 |==========| N3 |==========| N4 |=========| N5 |
   |    | T4<---t12|    |t11<---t10|    | t9<---t8 |    | t7<---T3|    |
   ======          ======          ======          ======         ======

                         Fig. 3 Reference Topology

   The STAMP Session-Sender (i.e.  Node N1) generates the STAMP test
   packet with the Forward HbH Delay TLV.  When an intermediate node
   receives the STAMP test packet, the node punts the packet to control
   plane and fills the Ingress Timestamp [n] filed in the Timestamp
   Tuple list [n].  Then the time taken by the intermediate node
   transmitting the test packet is recorded in to Egress Timestamp [n]
   field.  The mechanism of timestamping and punting packet to control
   plane is outside the scope of this specification.

   When the STAMP Session-Reflector received the test packet with the
   Forward HbH Delay TLV, it MUST copy the Forward HbH Delay TLV into
   the Session-Reflector test packet before its transmission.  Using
   Forward HbH Delay TLV in STAMP testing enables delay measurement per
   link in the forward path.

3.3.  Backward HbH Delay TLV

   STAMP Session-Sender MAY place the Backward HbH Delay TLV in Session-
   Sender test packets to record the ingress timestamp and egress
   timestamp when Session-Reflector test packets are received and sent



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   at every intermediate nodes in the backward path.  The Session-Sender
   MUST set the Length value according to the number of explicitly
   listed intermediate nodes in the backward path and the timestamp
   formats.  There are several methods to synchronize the clock, e.g.,
   Network Time Protocol (NTP) [RFC5905] and IEEE 1588v2 Precision Time
   Protocol (PTP) [IEEE.1588.2008].  For example, if a 64-bit timestamp
   format defined in NTP is used, the Length value MUST be set as a
   multiple of 16 octets.  The Timestamp Tuple list [1..n] fields MUST
   be set to zero upon Session-Sender test packets transmission and
   ignored upon receipt.

   The Backward HbH Delay TLV has the following format:

    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
   +-------------------------------+---------------+---------------+
   |   Backward HbH Delay Type     |     Length    |    Node Left  |
   +-------------------------------+---------------+---------------+
   |                                                               |
   |                     Timestamp Tuple list [1]                  |
   |                                                               |
   |                                                               |
   +---------------------------------------------------------------+
   ~                              ...                              ~
   +---------------------------------------------------------------+
   |                                                               |
   |                     Timestamp Tuple list [n]                  |
   |                                                               |
   |                                                               |
   +---------------------------------------------------------------+


                   Fig. 4 Backward HbH Delay TLV Format

   where fields are defined as the following:

   o  Backward HbH Delay Type: To be assigned by IANA.

   o  Length: A 8-bit field that indicates the length of the value
      portion in octets and will be a multiple of 16 octets dependent on
      the number of explicitly listed intermediate nodes in the backward
      path.

   o  Node Left: A 8-bit unsigned integer, which indicates the number of
      intermediate nodes remaining.  That is, number of explicitly
      listed intermediate nodes still to be visited before reaching the
      destination node in the backward path.  The Node Left field is set
      to n-1, where n is the number of intermediate nodes.



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   o  Timestamp Tuple list [1..n]: A variable-length field, which record
      the timestamp when the reflected test packet is received at the
      ingress of the n-th intermediate node and the timestamp when the
      reflected test packet is sent at egress of the n-th intermediate
      node.  For example, if a 64-bit timestamp format defined in NTP is
      used, the length of each Timestamp tuple (Ingress Timestamp [n],
      Egress Timestamp [n]) must be 16 octets.  The Timestamp Tuple list
      is encoded starting from the last intermediate node which is
      explicitly listed.  That is, the first element of the Timestamp
      Tuple list [1] records the timestamps when the reflected test
      packet received and forwarded at the last intermediate node of a
      explicit path, the second element records the penultimate
      Timestamp Tuple when the reflected test packet received and
      forwarded at the penultimate intermediate node of a explicit path,
      and so on.

   When the STAMP Session-Reflector received the Session-Sender test
   packet with the Backward HbH Delay TLV, it MUST copy the Backward HbH
   Delay TLV into the Session-Reflector test packet.

   When an intermediate node receives the reflected test packet, the
   node sends the packet to control plane and fills the Ingress
   Timestamp [n] filed of Backward HbH Delay TLV.  Then the time taken
   by the intermediate node transmitting the test packet is recorded in
   to Egress Timestamp [n] field of Backward HbH Delay TLV.  Using
   Backward HbH Delay TLV in STAMP testing enables delay measurement per
   link in the backward path.

3.4.  HbH Packet Loss TLV

   STAMP Session-Sender MAY place the HbH Packet Loss TLV in Session-
   Sender test packets to record the number of Session-Sender test
   packets received at and transmitted by every intermediate nodes along
   the forward path.  The Session-Sender MUST set the Length value
   according to the number of explicitly listed intermediate nodes in
   the forward path.  A Counter Tuple is composed of a 64-bit Receive
   Counter field and a 64-bit Transmit Counter field.  The Counter Tuple
   list [1..n] fields MUST be set to zero upon Session-Sender test
   packets transmission.

   The HbH Packet Loss TLV has the following format:










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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
   +-------------------------------+---------------+---------------+
   |     HbH Packet Loss Type      |     Length    |    Node Left  |
   +-------------------------------+---------------+---------------+
   |                                                               |
   |                     Counter Tuple list [1]                    |
   |                                                               |
   |                                                               |
   +---------------------------------------------------------------+
   ~                              ...                              ~
   +---------------------------------------------------------------+
   |                                                               |
   |                     Counter Tuple list [n]                    |
   |                                                               |
   |                                                               |
   +---------------------------------------------------------------+


                     Fig. 5 HbH Packet Loss TLV Format

   where fields are defined as the following:

   o  HbH Packet Loss Type: To be assigned by IANA.

   o  Length: A 8-bit field that indicates the length of the value
      portion in octets and will be a multiple of 16 octets dependent on
      the number of explicitly listed intermediate nodes in the forward
      path.

   o  Node Left: A 8-bit unsigned integer, which indicates the number of
      intermediate nodes remaining.  That is, number of explicitly
      listed intermediate nodes still to be visited before reaching the
      destination node in the forward path.  The Node Left field is set
      to n-1, where n is the number of intermediate nodes.

   o  Counter Tuple list [1..n]: A variable-length field, which record
      the Receive Counter and the Transmit Counter when the test packet
      is received at and transmitted by the n-th intermediate node.  The
      Counter Tuple list is encoded starting from the last intermediate
      node which is explicitly listed.  That is, the first element of
      the Counter Tuple list [1] records the Receive Counter and the
      Transmit Counter when the test packet is received at and
      transmitted by the last intermediate node of a explicit path, the
      second element records the penultimate Counter Tuple when the test
      packet received and forwarded at the penultimate intermediate node
      of a explicit path, and so on.




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   The STAMP Session-Sender generates the STAMP test packet with the HbH
   Packet Loss TLV.  When an intermediate node receives the STAMP test
   packet, the node punts the packet to control plane and writes the
   Receive Counter and the Transmit Counter at the Counter Tuple list
   [n] in the Session-Sender test packet.  The mechanism of punting
   packet to control plane is outside the scope of this specification.

   When the STAMP Session-Reflector received the test packet with the
   HbH Packet Loss TLV, it MUST copy the HbH Packet Loss TLV into the
   Session-Reflector test packet before its transmission.  Using HbH
   Packet Loss TLV in STAMP testing enables packet loss measurement per
   node/link in the forward path.

3.5.  HbH Bandwidth Utilization TLV

   STAMP Session-Sender MAY place the HbH Bandwidth Utilization TLV in
   Session-Sender test packets to record the ingress and egress
   bandwidth utilization at every intermediate nodes along the forward
   path.  The Session-Sender MUST set the Length value according to the
   number of explicitly listed intermediate nodes in the forward path.
   A BW Utilization Tuple is composed of a 32-bit ingress bandwidth
   utilization field and a 32-bit egress bandwidth utilization field.
   The BW Utilization Tuple list [1..n] fields MUST be set to zero upon
   Session-Sender test packets transmission.

   The HbH Bandwidth Utilization TLV has the following format:

    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
   +-------------------------------+---------------+---------------+
   |    HbH BW Utilization Type    |     Length    |    Node Left  |
   +-------------------------------+---------------+---------------+
   |                BW Utilization Tuple list [1]                  |
   |                                                               |
   +---------------------------------------------------------------+
   ~                              ...                              ~
   +---------------------------------------------------------------+
   |                BW Utilization Tuple list [n]                  |
   |                                                               |
   +---------------------------------------------------------------+


                Fig. 6 HbH Bandwidth Utilization TLV Format

   where fields are defined as the following:

   o  HbH BW Utilization Type: To be assigned by IANA.




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   o  Length: A 8-bit field that indicates the length of the value
      portion in octets and will be a multiple of 8 octets dependent on
      the number of explicitly listed intermediate nodes in the forward
      path.

   o  Node Left: A 8-bit unsigned integer, which indicates the number of
      intermediate nodes remaining.  That is, number of explicitly
      listed intermediate nodes still to be visited before reaching the
      destination node in the forward path.  The Node Left field is set
      to n-1, where n is the number of intermediate nodes.

   o  BW Utilization Tuple list [1..n]: A variable-length field, which
      record the ingress and egress bandwidth utilization when the test
      packet is received at and transmitted by the n-th intermediate
      node.  The BW Utilization Tuple list is encoded starting from the
      last intermediate node which is explicitly listed.  That is, the
      first element of the BW Utilization Tuple list [1] records the
      ingress and the egress bandwidth utilization when the test packet
      is received at and transmitted by the last intermediate node of a
      explicit path, the second element records the penultimate BW
      Utilization Tuple when the test packet received at and transmitted
      by the penultimate intermediate node of a explicit path, and so
      on.

   The STAMP Session-Sender generates the STAMP test packet with the HbH
   BW Utilization TLV.  When an intermediate node receives the STAMP
   test packet, the node punts the packet to control plane and writes
   the ingress and egress bandwidth utilization at the BW Utilization
   Tuple list [n] in the Session-Sender test packet.  The mechanism of
   punting packet to control plane is outside the scope of this
   specification.

   When the STAMP Session-Reflector received the test packet with the
   HbH BW Utilization TLV, it MUST copy the HbH BW Utilization TLV into
   the Session-Reflector test packet before its transmission.  The HbH
   BW Utilization TLV carried in STAMP test packet is usable to detect
   and troubleshoot the link congestion in the forward path.

3.6.  HbH Timestamp Information TLV

   STAMP Session-Sender MAY place the HbH Timestamp Information TLV in
   Session-Sender test packets to query the ingress and egress Timestamp
   Information at every intermediate nodes along the forward path.  The
   Timestamp Information includes the source of clock synchronization
   and the method of timestamp obtainment.  There are several types of
   clock synchronization source, e.g., NTP, PTP.  The method of
   timestamp obtainment may be from control plane (e.g.  NTP) or from
   data plane (e.g.  PTP).  A Timestamp Info Tuple is composed of a



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   8-bit ingress clock source field, a 8-bit ingress timestamp
   obtainment field, a 8-bit egress clock source field, and a 8-bit
   egress timestamp obtainment field.  The Session-Sender MUST set the
   Length value according to the number of explicitly listed
   intermediate nodes in the forward path.  The Timestamp Info Tuple
   list [1..n] fields MUST be set to zero upon Session-Sender test
   packets transmission.

   The HbH Timestamp Information TLV has the following format:

    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
   +-------------------------------+---------------+---------------+
   |    HbH Timestamp Info Type    |     Length    |    Node Left  |
   +-------------------------------+---------------+---------------+
   |                Timestamp Info Tuple list [1]                  |
   +---------------------------------------------------------------+
   ~                              ...                              ~
   +---------------------------------------------------------------+
   |                Timestamp Info Tuple list [n]                  |
   +---------------------------------------------------------------+


                Fig. 6 HbH Timestamp Information TLV Format

   where fields are defined as the following:

   o  HbH Timestamp Info Type: To be assigned by IANA.

   o  Length: A 8-bit field that indicates the length of the value
      portion in octets and will be a multiple of 4 octets dependent on
      the number of explicitly listed intermediate nodes in the forward
      path.

   o  Node Left: A 8-bit unsigned integer, which indicates the number of
      intermediate nodes remaining.  That is, number of explicitly
      listed intermediate nodes still to be visited before reaching the
      destination node in the forward path.  The Node Left field is set
      to n-1, where n is the number of intermediate nodes.

   o  Timestamp Info Tuple list [1..n]: A variable-length field, which
      record the source of clock synchronization and the method of
      timestamp obtainment at the ingress and egress when the test
      packet is received at and transmitted by the n-th intermediate
      node.  The Timestamp Info Tuple list is encoded starting from the
      last intermediate node which is explicitly listed.  That is, the
      first element of the Timestamp Info Tuple list [1] records the
      source of clock synchronization and the method of timestamp



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      obtainment at the ingress and egress when the test packet is
      received at and transmitted by the last intermediate node of a
      explicit path, the second element records the penultimate
      Timestamp Info Tuple when the test packet received at and
      transmitted by the penultimate intermediate node of a explicit
      path, and so on.

   The STAMP Session-Sender generates the STAMP test packet with the HbH
   Timestamp Information TLV.  When an intermediate node receives the
   STAMP test packet, the node punts the packet to control plane and
   writes the source of clock synchronization and the method of
   timestamp obtainment at the Timestamp Info Tuple list [n] in the
   Session-Sender test packet.  The mechanism of punting packet to
   control plane is outside the scope of this specification.

   When the STAMP Session-Reflector received the test packet with the
   HbH Timestamp Information TLV, it MUST copy the HbH Timestamp
   Information TLV into the Session-Reflector test packet before its
   transmission.  The HbH Timestamp Information TLV carried in STAMP
   test packet is usable to query timestamp information from every nodes
   in the forward path.

   Note that the source of clock synchronization, NTP or PTP, is part of
   configuration of the Session-Sender/Reflector or a particular test
   session [RFC8762].  This draft recommends every intermediate nodes to
   be configured to use the same source of clock synchronization.

4.  IANA Considerations

   IANA is requested to allocate values for the following TLV Type from
   the "STAMP TLV Type" registry [I-D.ietf-ippm-stamp-option-tlv].

      +------------+-------------------------------+---------------+
      | Code Point | Description                   | Reference     |
      +------------+-------------------------------+---------------+
      | TBA1       | IOAM Tracing Data TLV         | This document |
      | TBA2       | Forward HbH Delay TLV         | This document |
      | TBA3       | Backward HbH Delay TLV        | This document |
      | TBA4       | HbH Packet Loss TLV           | This document |
      | TBA5       | HbH BW Utilization TLV        | This document |
      | TBA6       | HbH Timestamp Information TLV | This document |
      +------------+-------------------------------+---------------+

5.  Security Considerations

   This document extensions new optional TLVs to STAMP.  It does not
   introduce any new security risks to STAMP.




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6.  Acknowledgements

   The authors would like to thank Hongwei Yang, Giuseppe Fioccola and
   Chang Liu for the reviews and comments.

7.  References

7.1.  Normative References

   [I-D.ietf-ippm-ioam-data]
              "Data Fields for In-situ OAM",
              <https://datatracker.ietf.org/doc/draft-ietf-ippm-ioam-
              data/>.

   [I-D.ietf-ippm-ioam-ipv6-options]
              "In-situ OAM IPv6 Options",
              <https://datatracker.ietf.org/doc/draft-ietf-ippm-ioam-
              ipv6-options/>.

   [I-D.ietf-ippm-stamp-option-tlv]
              "Simple Two-way Active Measurement Protocol Optional
              Extensions", <https://datatracker.ietf.org/doc/draft-ietf-
              ippm-stamp-option-tlv/>.

   [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>.

   [RFC8762]  "Simple Two-Way Active Measurement Protocol",
              <https://datatracker.ietf.org/doc/rfc8762/>.

7.2.  Informative References

   [IEEE.1588.2008]
              "IEEE Standard for a Precision Clock Synchronization
              Protocol for Networked Measurement and Control Systems",
              <https://ieeexplore.ieee.org/document/4579760>.

   [RFC5905]  "Network Time Protocol Version 4: Protocol and Algorithms
              Specification", <https://www.rfc-editor.org/info/rfc5905>.

Authors' Addresses








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   Yali Wang
   Huawei
   156 Beijing Rd., Haidian District
   Beijing
   China

   Email: wangyali11@huawei.com


   Tianran Zhou
   Huawei
   156 Beijing Rd., Haidian District
   Beijing
   China

   Email: zhoutianran@huawei.com


   Hongwei Yang
   China Mobile
   Beijing
   China

   Email: yanghongwei@chinamobile.com


   Chang Liu
   China Unicom
   Beijing
   China

   Email: liuc131@chinaunicom.cn



















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