Network Working Group                                          G. Mirsky
Internet-Draft                                                    X. Min
Updates: 8762 (if approved)                                    ZTE Corp.
Intended status: Standards Track                               H. Nydell
Expires: December 14, 2020                             Accedian Networks
                                                                R. Foote
                                                                   Nokia
                                                             A. Masputra
                                                              Apple Inc.
                                                              E. Ruffini
                                                                  OutSys
                                                           June 12, 2020


     Simple Two-way Active Measurement Protocol Optional Extensions
                  draft-ietf-ippm-stamp-option-tlv-05

Abstract

   This document describes optional extensions to Simple Two-way Active
   Measurement Protocol (STAMP) which enable measurement performance
   metrics in addition to ones supported by the STAMP base
   specification.  The document also defines a STAMP Test Session
   Identifier and thus updates RFC 8762.

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 December 14, 2020.

Copyright Notice

   Copyright (c) 2020 IETF Trust and the persons identified as the
   document authors.  All rights reserved.





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   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.  Conventions used in this document . . . . . . . . . . . . . .   3
     2.1.  Terminology . . . . . . . . . . . . . . . . . . . . . . .   3
     2.2.  Requirements Language . . . . . . . . . . . . . . . . . .   3
   3.  STAMP Test Session Identifier . . . . . . . . . . . . . . . .   4
   4.  TLV Extensions to STAMP . . . . . . . . . . . . . . . . . . .   8
     4.1.  Extra Padding TLV . . . . . . . . . . . . . . . . . . . .   9
     4.2.  Location TLV  . . . . . . . . . . . . . . . . . . . . . .  10
     4.3.  Timestamp Information TLV . . . . . . . . . . . . . . . .  11
     4.4.  Class of Service TLV  . . . . . . . . . . . . . . . . . .  12
     4.5.  Direct Measurement TLV  . . . . . . . . . . . . . . . . .  14
     4.6.  Access Report TLV . . . . . . . . . . . . . . . . . . . .  15
     4.7.  Follow-up Telemetry TLV . . . . . . . . . . . . . . . . .  16
     4.8.  HMAC TLV  . . . . . . . . . . . . . . . . . . . . . . . .  18
   5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  19
     5.1.  STAMP TLV Registry  . . . . . . . . . . . . . . . . . . .  19
     5.2.  Synchronization Source Sub-registry . . . . . . . . . . .  20
     5.3.  Timestamping Method Sub-registry  . . . . . . . . . . . .  20
     5.4.  Return Code Sub-registry  . . . . . . . . . . . . . . . .  21
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .  22
   7.  Acknowledgments . . . . . . . . . . . . . . . . . . . . . . .  22
   8.  Contributors  . . . . . . . . . . . . . . . . . . . . . . . .  22
   9.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  22
     9.1.  Normative References  . . . . . . . . . . . . . . . . . .  22
     9.2.  Informative References  . . . . . . . . . . . . . . . . .  23
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  24

1.  Introduction

   Simple Two-way Active Measurement Protocol (STAMP) [RFC8762] supports
   the use of optional extensions that use Type-Length-Value (TLV)
   encoding.  Such extensions enhance the STAMP base functions, such as
   measurement of one-way and round-trip delay, latency, packet loss,
   and the ability to detect packet duplication and out-of- order
   delivery of the test packets.  This specification defines optional
   STAMP extensions, their formats, and the theory of operation.  Also,



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   a STAMP Test Session Identifier is defined as an update of the base
   STAMP specification [RFC8762].

2.  Conventions used in this document

2.1.  Terminology

   STAMP - Simple Two-way Active Measurement Protocol

   DSCP - Differentiated Services Code Point

   ECN - Explicit Congestion Notification

   NTP - Network Time Protocol

   PTP - Precision Time Protocol

   HMAC Hashed Message Authentication Code

   TLV Type-Length-Value

   BITS Building Integrated Timing Supply

   SSU Synchronization Supply Unit

   GPS Global Positioning System

   GLONASS Global Orbiting Navigation Satellite System

   LORAN-C Long Range Navigation System Version C

   MBZ Must Be Zero

   CoS Class of Service

   PMF Performance Measurement Function

   SSID STAMP Session Identifier

2.2.  Requirements Language

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
   "OPTIONAL" in this document are to be interpreted as described in BCP
   14 [RFC2119] [RFC8174] when, and only when, they appear in all
   capitals, as shown here.





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3.  STAMP Test Session Identifier

   STAMP Session-Sender transmits test packets to STAMP Session-
   Reflector.  STAMP Session-Reflector receives Session-Sender's packet
   and acts according to the configuration and optional control
   information communicated in the Session-Sender's test packet.  STAMP
   defines two different test packet formats, one for packets
   transmitted by the STAMP-Session-Sender and one for packets
   transmitted by the STAMP-Session-Reflector.  STAMP supports two
   modes: unauthenticated and authenticated.  Unauthenticated STAMP test
   packets are compatible on the wire with unauthenticated TWAMP-Test
   [RFC5357] packet formats.

   By default, STAMP uses symmetrical packets, i.e., the size of the
   packet transmitted by Session-Reflector equals the size of the packet
   received by the Session-Reflector.

   A STAMP Session is identified using 4-tuple (source and destination
   IP addresses, source and destination UDP port numbers).  A STAMP
   Session-Sender MAY generate a locally unique STAMP Session Identifier
   (SSID).  SSID is two octets long non-zero unsigned integer.  A
   Session-Sender MAY use SSID to identify a STAMP test session.  If
   SSID is used, it MUST be present in each test packet of the given
   test session.  In the unauthenticated mode, SSID is located, as
   displayed in Figure 1.


























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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        |             SSID              |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                                                               |
      |                                                               |
      |                         MBZ (28 octets)                       |
      |                                                               |
      |                                                               |
      |                                                               |
      |                                                               |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |             Type              |           Length              |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      ~                            Value                              ~
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Figure 1: An example of an extended STAMP Session-Sender test packet
                      format in unauthenticated mode

   An implementation of STAMP Session-Reflector that supports this
   specification SHOULD identify a STAMP Session using the SSID in
   combination with elements of the usual 4-tuple for the session.
   Before a test session commenced, a Session-Reflector MUST be
   provisioned with all the elements that identify the STAMP Session.  A
   STAMP Session-Reflector MUST discard the non-matching STAMP test
   packet(s).  The means of provisioning the STAMP Session
   identification is outside the scope of this specification.  A
   conforming implementation of STAMP Session-Reflector MUST copy the
   SSID value from the received test packet and put it into the
   reflected packet, as displayed in Figure 2.














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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        |           SSID                |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                          Receive Timestamp                    |
    |                                                               |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                 Session-Sender Sequence Number                |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                  Session-Sender Timestamp                     |
    |                                                               |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    | Session-Sender Error Estimate |           MBZ                 |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |Ses-Sender TTL |                   MBZ                         |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |             Type              |           Length              |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    ~                            Value                              ~
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

     Figure 2: An example of an extended STAMP Session-Reflector test
                   packet format in unauthenticated mode

   A STAMP Session-Reflector that does not support this specification,
   will return the zeroed SSID field in the reflected STAMP test packet.
   The Session-Sender MUST stop the session if it receives a zeroed SSID
   field.

   In the authenticated mode, location of SSID field is shown in
   Figure 3 and Figure 4.














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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         |            SSID               |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    ~                                                               ~
    |                         MBZ (68 octets)                       |
    ~                                                               ~
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                                                               |
    |                       HMAC (16 octets)                        |
    |                                                               |
    |                                                               |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

         Figure 3: Base STAMP Session-Sender test packet format in
                            authenticated 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                        |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                        MBZ (12 octets)                        |
      |                                                               |
      |                                                               |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                          Timestamp                            |
      |                                                               |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |         Error Estimate        |            SSID               |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                        MBZ (4 octets)                         |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                        Receive Timestamp                      |
      |                                                               |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                        MBZ (8 octets)                         |
      |                                                               |



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      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                 Session-Sender Sequence Number                |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                        MBZ (12 octets)                        |
      |                                                               |
      |                                                               |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                 Session-Sender Timestamp                      |
      |                                                               |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      | Session-Sender Error Estimate |                               |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+                               +
      |                        MBZ (6 octets)                         |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |Ses-Sender TTL |                                               |
      +-+-+-+-+-+-+-+-+                                               +
      |                                                               |
      |                        MBZ (15 octets)                        |
      |                                                               |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                        HMAC (16 octets)                       |
      |                                                               |
      |                                                               |
      |                                                               |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


       Figure 4: Base STAMP Session-Reflector test packet format in
                            authenticated mode

4.  TLV Extensions to STAMP

   Type-Length-Value (TLV) encoding scheme provides a flexible extension
   mechanism for optional informational elements.  TLV is an optional
   field in the STAMP test packet.  Multiple TLVs MAY be placed in the
   STAMP test packet.  A TLV MAY be enclosed in a TLV.  TLVs have the
   two octets long Type field, two octets long Length field that is
   equal to the length of the Value field in octets.  Type values, see
   Section 5.1, less than 32768 identify mandatory TLVs that MUST be
   supported by an implementation.  Type values greater than or equal to
   32768 identify optional TLVs that SHOULD be ignored if the
   implementation does not understand or support them.  If a Type value
   for TLV or sub-TLV is in the range for Vendor Private Use, the Length
   MUST be at least 4, and the first four octets MUST be that vendor's
   the Structure of Management Information (SMI) Private Enterprise
   Number, in network octet order.  The rest of the Value field is
   private to the vendor.  The following sections describe the use of




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   TLVs for STAMP that extend STAMP capability beyond its base
   specification.

   A STAMP node, whether Session-Sender or Session-Reflector, receiving
   a test packet MUST determine whether the packet is a base STAMP
   packet or includes one or more TLVs.  The node MUST compare the value
   in the Length field of the UDP header and the length of the base
   STAMP test packet in the mode, unauthenticated or authenticated based
   on the configuration of the particular STAMP test session.  If the
   difference between the two values is larger than the length of UDP
   header, then the test packet includes one or more STAMP TLVs that
   immediately follow the base STAMP test packet.

   A system that has received a STAMP test packet with extension TLVs
   MUST validate each TLV:

      if the value of the Type field is one from the Mandatory TLV range
      (Table 1) that the system does not support, the processing of the
      TLV MUST be stopped.  If the system is the Session-Reflector, it
      MUST send the ICMP Parameter Problem message with Code set to 0
      and the Pointer referring to the Type field of the TLV;

      fixed-size TLVs are verified that the Length field value equals
      the value defined for the particular type.  If the values are not
      equal, the processing of extension TLVs MUST be stopped.  Also, if
      the system is the Session-Reflector, it MUST send the ICMP
      Parameter Problem message with Code set to 0 and the Pointer
      referring to the Length field of the TLV.

   Detected error events MUST be logged.  Note that transmission of ICMP
   Error messages and logging SHOULD be throttled.

4.1.  Extra Padding TLV

       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
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |      Extra Padding Type       |           Length              |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                                                               |
      ~                         Extra Padding                         ~
      |                                                               |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                        Figure 5: Extra Padding TLV

   where fields are defined as the following:




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   o  Extra Padding Type - TBA1 allocated by IANA Section 5.1

   o  Length - two octets long field equals length on the Extra Padding
      field in octets.

   o  Extra Padding - a pseudo-random sequence of numbers.  The field
      MAY be filled with all zeros.

   The Extra Padding TLV is similar to the Packet Padding field in
   TWAMP-Test packet [RFC5357].  The Extra Padding TLV MUST be used to
   create STAMP test packets of larger size that the base STAMP packet
   [RFC8762].  The length of the base STAMP is 44 octets in the
   unauthenticated mode or 112 octets in the authenticated mode.  The
   Extra Padding TLV MUST be the last TLV in a STAMP test packet.

4.2.  Location TLV

   STAMP Session-Sender MAY include the Location TLV to request
   information from the Session-Reflector.  The Session-Sender SHOULD
   NOT fill any information fields except for Type and Length.  The
   Session-Reflector MUST validate the Length value against the address
   family of the transport encapsulating the STAMP test packet.  If the
   Length field's value is invalid, the Session-Reflector MUST zero all
   fields and MUST NOT return any information to the Session-Sender.
   The Session-Reflector MUST ignore all other fields of the received
   Location TLV.

       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
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |          Location Type        |           Length              |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                          Source MAC                           |
      +                               +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                               |           Reserved            |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      ~                    Destination IP Address                     ~
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      ~                       Source IP Address                       ~
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |        Destination Port       |          Source Port          |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                 Figure 6: Session-Reflector Location TLV

   where fields are defined as the following:

   o  Location Type - TBA2 allocated by IANA Section 5.1



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   o  Length - two octets long field equals the length of the Value
      field in octets.  The Length field value MUST equal 20 octets for
      the IPv4 address family.  For the IPv6 address family, the value
      of the Length field MUST equal 44 octets.  All other values are
      invalid.

   o  Source MAC - 6 octets 48 bits long field.  The Session-Reflector
      MUST copy Source MAC of received STAMP packet into this field.

   o  Reserved - two octets long field.  MUST be zeroed on transmission
      and ignored on reception.

   o  Destination IP Address - IPv4 or IPv6 destination address of the
      packet received by the STAMP Session-Reflector.

   o  Source IP Address - IPv4 or IPv6 source address of the packet
      received by the STAMP Session-Reflector.

   o  Destination Port - two octets long UDP destination port number of
      the received STAMP packet.

   o  Source Port - two octets long UDP source port number of the
      received STAMP packet.

   The Location TLV MAY be used to determine the last-hop addressing for
   STAMP packets including source and destination IP addresses as well
   as the MAC address of the last-hop router.  Last-hop MAC address MAY
   be monitored by the Session-Sender whether there has been a path
   switch on the last hop, closest to the Session-Reflector.  The IP
   addresses and UDP port will indicate if there is a NAT router on the
   path, and allows the Session-Sender to identify the IP address of the
   Session-Reflector behind the NAT, detect changes in the NAT mapping
   that could cause sending the STAMP packets to the wrong Session-
   Reflector.

4.3.  Timestamp Information TLV

   STAMP Session-Sender MAY include the Timestamp Information TLV to
   request information from the Session-Reflector.  The Session-Sender
   SHOULD NOT fill any information fields except for Type and Length.
   The Session-Reflector MUST validate the Length value of the STAMP
   test packet.  If the value of the Length field is invalid, the
   Session-Reflector MUST zero all fields and MUST NOT return any
   information to the Session-Sender.







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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
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |  Timestamp Information Type   |           Length              |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |  Sync. Src In | Timestamp In  | Sync. Src Out | Timestamp Out |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                    Figure 7: Timestamp Information TLV

   where fields are defined as the following:

   o  Timestamp Information Type - TBA3 allocated by IANA Section 5.1

   o  Length - two octets long field, set equal to the value 4.

   o  Sync Src In - one octet long field that characterizes the source
      of clock synchronization at the ingress of Session-Reflector.
      There are several methods to synchronize the clock, e.g., Network
      Time Protocol (NTP) [RFC5905], Precision Time Protocol (PTP)
      [IEEE.1588.2008], Synchronization Supply Unit (SSU) or Building
      Integrated Timing Supply (BITS), or Global Positioning System
      (GPS), Global Orbiting Navigation Satellite System (GLONASS) and
      Long Range Navigation System Version C (LORAN-C).  The value is
      one of those listed in Table 4.

   o  Timestamp In - one octet long field that characterizes the method
      by which the ingress of Session-Reflector obtained the timestamp
      T2.  A timestamp may be obtained with hardware assistance, via
      software API from a local wall clock, or from a remote clock (the
      latter is referred to as "control plane").  The value is one of
      those listed in Table 6.

   o  Sync Src Out - one octet long field that characterizes the source
      of clock synchronization at the egress of Session-Reflector.  The
      value is one of those listed in Table 4.

   o  Timestamp Out - one octet long field that characterizes the method
      by which the egress of Session-Reflector obtained the timestamp
      T3.  The value is one of those listed in Table 6.

4.4.  Class of Service TLV

   The STAMP Session-Sender MAY include Class of Service (CoS) TLV in
   the STAMP test packet.  If the CoS TLV is present in the STAMP test
   packet and the value of the DSCP1 field is zero, then the STAMP
   Session-Reflector MUST copy the values of Differentiated Services
   Code Point (DSCP) ECN fields from the received STAMP test packet into



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   DSCP2 and ECN fields respectively of the CoS TLV of the reflected
   STAMP test packet.  If the value of the DSCP1 field is non-zero, then
   the STAMP Session-Reflector MUST use DSCP1 value from the CoS TLV in
   the received STAMP test packet as DSCP value of STAMP reflected test
   packet and MUST copy DSCP and ECN values of the received STAMP test
   packet into DSCP2 and ECN fields of Class of Service TLV in the STAMP
   reflected a packet.  Upon receiving the reflected packet, the
   Session-Sender,will save the DSCP and ECN values for analysis of the
   CoS in the reverse direction.

       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
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |      Class of Service Type    |           Length              |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |   DSCP1   |   DSCP2   |ECN|            Reserved               |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                      Figure 8: Class of Service TLV

   where fields are defined as the following:

   o  Class of Service Type - TBA4 allocated by IANA Section 5.1

   o  Length - two octets long field, set equal to the value 4.

   o  DSCP1 - The Differentiated Services Code Point (DSCP) intended by
      the Session-Sender.  To be used as the return DSCP from the
      Session-Reflector.

   o  DSCP2 - The received value in the DSCP field at the Session-
      Reflector in the forward direction.

   o  ECN - The received value in the ECN field at the Session-Reflector
      in the forward direction.

   o  Reserved - 18 bits long field, must be zeroed in transmission and
      ignored on receipt.

   A STAMP Session-Sender that includes the CoS TLV sets the value of
   the DSCP1 field and zeroes the value of the DSCP2 field.  A STAMP
   Session-Reflector that received the test packet with the CoS TLV MUST
   include the CoS TLV in the reflected test packet.  Also, the Session-
   Reflector MUST copy the value of the DSCP field of the IP header of
   the received STAMP test packet into the DSCP2 field in the reflected
   test packet.  At last, the Session-Reflector MUST set the value of
   DSCP field's value in the IP header of the reflected test packet
   equal to the value of the DSCP1 field of the received test packet.



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   Re-mapping of CoS in some use cases, for example, in mobile backhaul
   networks is used to provide multiple services, i.e., 2G, 3G, LTE,
   over the same network.  But if it is misconfigured, then it is often
   difficult to diagnose the root cause of the problem that is viewed as
   an excessive packet drop of higher-level service while packet drop
   for lower service packets is at a normal level.  Using CoS TLV in
   STAMP test helps to troubleshoot the existing problem and also verify
   whether DiffServ policies are processing CoS as required by the
   configuration.

4.5.  Direct Measurement TLV

   The Direct Measurement TLV enables collection of "in profile" IP
   packets that had been transmitted and received by the Session-Sender
   and Session-Reflector respectfully.  The definition of "in-profile
   packet" is outside the scope of this document and is left to the test
   operators to determine.

       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
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |    Direct Measurement Type    |           Length              |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |              Session-Sender Tx counter  (S_TxC)               |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |             Session-Reflector Rx counter  (R_RxC)             |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |             Session-Reflector Tx counter  (R_TxC)             |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                     Figure 9: Direct Measurement TLV

   where fields are defined as the following:

   o  Direct Measurement Type - TBA5 allocated by IANA Section 5.1

   o  Length - two octets long field equals length on the Value field in
      octets.  Length field value MUST equal 12 octets.

   o  Session-Sender Tx counter (S_TxC) is four octets long field.

   o  Session-Reflector Rx counter (R_RxC) is four octets long field.
      MUST be zeroed by the Session-Sender and filled by the Session-
      Reflector.

   o  Session-Reflector Tx counter (R_TxC) is four octets long field.
      MUST be zeroed by the Session-Sender and filled by the Session-
      Reflector.



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4.6.  Access Report TLV

   A STAMP Session-Sender MAY include Access Report TLV (Figure 10) to
   indicate changes to the access network status to the Session-
   Reflector.  The definition of an access network is outside the scope
   of this document.

        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
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |       Access Report Type      |           Length              |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |   ID  |  Resv |  Return Code  |          Reserved             |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                       Figure 10: Access Report TLV

   where fields are defined as follows:

   o  Access Report Type - TBA6 allocated by IANA Section 5.1.

   o  Length - two octets long field, set equal to the value 4.

   o  ID (Access ID) - four bits long field that identifies the access
      network, e.g., 3GPP (Radio Access Technologies specified by 3GPP)
      or Non-3GPP (accesses that are not specified by 3GPP) [TS23501].
      The value is one of those listed below:

      *  1 - 3GPP Network

      *  2 - Non-3GPP Network

      All other values are invalid and the TLV that contains it MUST be
      discarded.

   o  Resv - four bits long field, must be zeroed on transmission and
      ignored on receipt.

   o  Return Code - one octet long field that identifies the report
      signal, e.g., available, unavailable.  The value is passed,
      supplied to the STAMP end-point through some mechanism that is
      outside the scope of this document.  The value is one of those
      listed in Section 5.4.

   o  Reserved - two octets long field, must be zeroed on transmission
      and ignored on receipt.





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   The STAMP Session-Sender that includes the Access Report TLV sets the
   value of the Access ID field according to the type of access network
   it reports on.  Also, the Session-Sender sets the value of the Return
   Code field to reflect the operational state of the access network.
   The mechanism to determine the state of the access network is outside
   the scope of this specification.  A STAMP Session-Reflector that
   received the test packet with the Access Report TLV MUST include the
   Access Report TLV in the reflected test packet.  The Session-
   Reflector MUST set the value of the Access ID and Return Code fields
   equal to the values of the corresponding fields from the test packet
   it has received.

   The Session-Sender MUST also arm a retransmission timer after sending
   a test packet that includes the Access Report TLV.  This timer MUST
   be disarmed upon the reception of the reflected STAMP test packet
   that includes Access Report TLV.  In the event the timer expires
   before such a packet is received, the Session-Sender MUST retransmit
   the STAMP test packet that contains the Access Report TLV.  This
   retransmission SHOULD be repeated up to four times before the
   procedure is aborted.  Setting the value for the retransmission timer
   is based on local policies, network environment.  The default value
   of the retransmission timer for Access Report TLV SHOULD be three
   seconds.  An implementation MUST provide control of the
   retransmission timer value and the number of retransmissions.

   The Access Report TLV is used by the Performance Measurement Function
   (PMF) components of the Access Steering, Switching and Splitting
   feature for 5G networks [TS23501].  The PMF component in the User
   Equipment acts as the STAMP Session-Sender, and the PMF component in
   the User Plane Function acts as the STAMP Session-Reflector.

4.7.  Follow-up Telemetry TLV

   A Session-Reflector might be able to put in the Timestamp field only
   an "SW Local" (see Table 6) timestamp.  But the hosting system might
   provide the timestamp closer to the start of the actual packet
   transmission even though when it is not possible to deliver the
   information to the Session-Sender in the packet itself.  This
   timestamp might nevertheless be important for the Session-Sender, as
   it improves the accuracy of measuring network delay by minimizing the
   impact of egress queuing delays on the measurement.

   A STAMP Session-Sender MAY include the Follow-up Telemetry TLV to
   request information from the Session-Reflector.  The Session-Sender
   MUST set the Follow-up Telemetry Type and Length fields to their
   appropriate values.  Sequence Number and Timestamp fields MUST be
   zeroed on transmission by the Session-Sender and ignored by the
   Session-Reflector upon receipt of the STAMP test packet that includes



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   the Follow-up Telemetry TLV.  The Session-Reflector MUST validate the
   Length value of the STAMP test packet.  If the value of the Length
   field is invalid, the Session-Reflector MUST zero Sequence Number and
   Timestamp fields.  If the Session-Reflector is in stateless mode
   (defined in Section 4.2 [RFC8762]), it MUST zero Sequence Number and
   Timestamp fields.

        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
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |   Follow-up Telemetry Type    |           Length              |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                        Sequence Number                        |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                      Follow-up Timestamp                      |
       |                                                               |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |  Timestamp M  |                     Reserved                  |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                    Figure 11: Follow-up Telemetry TLV

   where fields are defined as follows:

   o  Follow-up Telemetry Type - TBA7 allocated by IANA Section 5.1.

   o  Length - two octets long field, set equal to the value 16 octets.

   o  Sequence Number - four octets long field indicating the sequence
      number of the last packet reflected in the same STAMP-test
      session.  Since the Session-Reflector runs in the stateful mode
      (defined in Section 4.2 [RFC8762]), it is the Session-Reflector's
      Sequence Number of the previous reflected packet.

   o  Follow-up Timestamp - eight octets long field, with the format
      indicated by the Z flag of the Error Estimate field of the packet
      transmitted by a Session-Reflector, as described in Section 4.1
      [RFC8762].  It carries the timestamp when the reflected packet
      with the specified sequence number was sent.

   o  Timestamp M(ode) - one octet long field that characterizes the
      method by which the entity that transmits a reflected STAMP packet
      obtained the Follow-up Timestamp.  The value is one of those
      listed in Table 6.

   o  Reserved - the three octets-long field.  Its value MUST be zeroed
      on transmission and ignored on receipt.




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4.8.  HMAC TLV

   The STAMP authenticated mode protects the integrity of data collected
   in the STAMP base packet.  STAMP extensions are designed to provide
   valuable information about the condition of a network, and protecting
   the integrity of that data is also essential.  The keyed Hashed
   Message Authentication Code (HMAC) TLV MUST be included in a STAMP
   test packet in the authenticated mode, excluding when the only TLV
   present is Extra Padding TLV.  The HMAC TLV MUST follow all TLVs
   included in a STAMP test packet, except for the Extra Padding TLV.
   The HMAC TLV MAY be used to protect the integrity of STAMP extensions
   in STAMP 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
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |            HMAC Type          |             Length            |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                                                               |
      |                              HMAC                             |
      |                                                               |
      |                                                               |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                            Figure 12: HMAC TLV

   where fields are defined as follows:

   o  HMAC Type - is two octets long field, value TBA8 allocated by IANA
      Section 5.1.

   o  Length - two octets long field, set equal to the value 16 octets.

   o  HMAC - is 16 octets long field that carries HMAC digest of the
      text of all preceding TLVs.

   As defined in [RFC8762], STAMP uses HMAC-SHA-256 truncated to 128
   bits ([RFC4868]).  All considerations regarding using the key and key
   distribution and management listed in Section 4.4 of [RFC8762] are
   fully applicable to the use of the HMAC TLV.  HMAC is calculated as
   defined in [RFC2104] over text as the concatenation of all preceding
   TLVs.  The digest then MUST be truncated to 128 bits and written into
   the HMAC field.  In the authenticated mode, HMAC MUST be verified
   before using any data in the included STAMP TLVs.  If HMAC
   verification by the Session-Reflector fails, then an ICMP Parameter
   Problem message MUST be generated (with consideration of limiting the
   rate of error messages).  The Code value MUST be set to 0 and the
   Pointer identifying HMAC Type.  Also, both Session-Sender and



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   Session-Reflector SHOULD log the notification that HMAC verification
   of STAMP TLVs failed.  The packet that failed HMAC verification MUST
   be dropped.

5.  IANA Considerations

5.1.  STAMP TLV Registry

   IANA is requested to create the STAMP TLV Type registry.  All code
   points in the range 1 through 32759 in this registry shall be
   allocated according to the "IETF Review" procedure as specified in
   [RFC8126].  Code points in the range 32760 through 65279 in this
   registry shall be allocated according to the "First Come First
   Served" procedure as specified in [RFC8126].  Remaining code points
   are allocated according to Table 1:

   +---------------+-------------------------+-------------------------+
   | Value         |       Description       | Reference               |
   +---------------+-------------------------+-------------------------+
   | 0             |         Reserved        | This document           |
   | 1- 32767      |      Mandatory TLV,     | IETF Review             |
   |               |        unassigned       |                         |
   | 32768 - 65279 |      Optional TLV,      | First Come First Served |
   |               |        unassigned       |                         |
   | 65280 - 65519 |       Experimental      | This document           |
   | 65520 - 65534 |       Private Use       | This document           |
   | 65535         |         Reserved        | This document           |
   +---------------+-------------------------+-------------------------+

                     Table 1: STAMP TLV Type Registry

   This document defines the following new values in the Mandatory TLV
   range of the STAMP TLV Type registry:

             +-------+-----------------------+---------------+
             | Value |      Description      | Reference     |
             +-------+-----------------------+---------------+
             | TBA1  |     Extra Padding     | This document |
             | TBA2  |        Location       | This document |
             | TBA3  | Timestamp Information | This document |
             | TBA4  |    Class of Service   | This document |
             | TBA5  |   Direct Measurement  | This document |
             | TBA6  |     Access Report     | This document |
             | TBA7  |  Follow-up Telemetry  | This document |
             | TBA8  |          HMAC         | This document |
             +-------+-----------------------+---------------+

                           Table 2: STAMP Types



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5.2.  Synchronization Source Sub-registry

   IANA is requested to create Synchronization Source sub-registry as
   part of the STAMP TLV Type registry.  All code points in the range 1
   through 127 in this registry shall be allocated according to the
   "IETF Review" procedure as specified in [RFC8126].  Code points in
   the range 128 through 239 in this registry shall be allocated
   according to the "First Come First Served" procedure as specified in
   [RFC8126].  Remaining code points are allocated according to Table 1:

          +-----------+--------------+-------------------------+
          | Value     | Description  | Reference               |
          +-----------+--------------+-------------------------+
          | 0         |   Reserved   | This document           |
          | 1- 127    |  Unassigned  | IETF Review             |
          | 128 - 239 |  Unassigned  | First Come First Served |
          | 240 - 249 | Experimental | This document           |
          | 250 - 254 | Private Use  | This document           |
          | 255       |   Reserved   | This document           |
          +-----------+--------------+-------------------------+

               Table 3: Synchronization Source Sub-registry

   This document defines the following new values in the Synchronization
   Source sub-registry:

              +-------+---------------------+---------------+
              | Value |     Description     | Reference     |
              +-------+---------------------+---------------+
              | 1     |         NTP         | This document |
              | 2     |         PTP         | This document |
              | 3     |       SSU/BITS      | This document |
              | 4     | GPS/GLONASS/LORAN-C | This document |
              | 5     |  Local free-running | This document |
              +-------+---------------------+---------------+

                     Table 4: Synchronization Sources

5.3.  Timestamping Method Sub-registry

   IANA is requested to create Timestamping Method sub-registry as part
   of the STAMP TLV Type registry.  All code points in the range 1
   through 127 in this registry shall be allocated according to the
   "IETF Review" procedure as specified in [RFC8126].  Code points in
   the range 128 through 239 in this registry shall be allocated
   according to the "First Come First Served" procedure as specified in
   [RFC8126].  Remaining code points are allocated according to Table 1:




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          +-----------+--------------+-------------------------+
          | Value     | Description  | Reference               |
          +-----------+--------------+-------------------------+
          | 0         |   Reserved   | This document           |
          | 1- 127    |  Unassigned  | IETF Review             |
          | 128 - 239 |  Unassigned  | First Come First Served |
          | 240 - 249 | Experimental | This document           |
          | 250 - 254 | Private Use  | This document           |
          | 255       |   Reserved   | This document           |
          +-----------+--------------+-------------------------+

                 Table 5: Timestamping Method Sub-registry

   This document defines the following new values in the Timestamping
   Methods sub-registry:

                 +-------+---------------+---------------+
                 | Value |  Description  | Reference     |
                 +-------+---------------+---------------+
                 | 1     |   HW Assist   | This document |
                 | 2     |    SW local   | This document |
                 | 3     | Control plane | This document |
                 +-------+---------------+---------------+

                       Table 6: Timestamping Methods

5.4.  Return Code Sub-registry

   IANA is requested to create Return Code sub-registry as part of STAMP
   TLV Type registry.  All code points in the range 1 through 127 in
   this registry shall be allocated according to the "IETF Review"
   procedure as specified in [RFC8126].  Code points in the range 128
   through 239 in this registry shall be allocated according to the
   "First Come First Served" procedure as specified in [RFC8126].
   Remaining code points are allocated according to Table 7:

          +-----------+--------------+-------------------------+
          | Value     | Description  | Reference               |
          +-----------+--------------+-------------------------+
          | 0         |   Reserved   | This document           |
          | 1- 127    |  Unassigned  | IETF Review             |
          | 128 - 239 |  Unassigned  | First Come First Served |
          | 240 - 249 | Experimental | This document           |
          | 250 - 254 | Private Use  | This document           |
          | 255       |   Reserved   | This document           |
          +-----------+--------------+-------------------------+

                     Table 7: Return Code Sub-registry



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   This document defines the following new values in the Return Code
   sub-registry:

              +-------+---------------------+---------------+
              | Value |     Description     | Reference     |
              +-------+---------------------+---------------+
              | 1     |  Network available  | This document |
              | 2     | Network unavailable | This document |
              +-------+---------------------+---------------+

                           Table 8: Return Codes

6.  Security Considerations

   This document defines extensions to STAMP [RFC8762] and inherits all
   the security considerations applicable to the base protocol.
   Additionally, the HMAC TLV is defined in this document to protect the
   integrity of optional STAMP extensions.  The use of HMAC TLV is
   discussed in detail in Section 4.8.

7.  Acknowledgments

   Authors much appreciate the thorough review and thoughtful comments
   received from Tianran Zhou, Rakesh Gandhi, Yuezhong Song and Yali
   Wang.  Authors express their gratitude to Al Morton for his comments
   and the most valuable suggestions.

8.  Contributors

   The following people contributed text to this document:

      Guo Jun
      ZTE Corporation
      68# Zijinghua Road
      Nanjing, Jiangsu  210012
      P.R.China

      Phone: +86 18105183663
      Email: guo.jun2@zte.com.cn

9.  References

9.1.  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>.



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   [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>.

   [RFC8126]  Cotton, M., Leiba, B., and T. Narten, "Guidelines for
              Writing an IANA Considerations Section in RFCs", BCP 26,
              RFC 8126, DOI 10.17487/RFC8126, June 2017,
              <https://www.rfc-editor.org/info/rfc8126>.

   [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>.

   [RFC8762]  Mirsky, G., Jun, G., Nydell, H., and R. Foote, "Simple
              Two-Way Active Measurement Protocol", RFC 8762,
              DOI 10.17487/RFC8762, March 2020,
              <https://www.rfc-editor.org/info/rfc8762>.

9.2.  Informative References

   [IEEE.1588.2008]
              "Standard for a Precision Clock Synchronization Protocol
              for Networked Measurement and Control Systems",
              IEEE Standard 1588, March 2008.

   [RFC2104]  Krawczyk, H., Bellare, M., and R. Canetti, "HMAC: Keyed-
              Hashing for Message Authentication", RFC 2104,
              DOI 10.17487/RFC2104, February 1997,
              <https://www.rfc-editor.org/info/rfc2104>.

   [RFC4868]  Kelly, S. and S. Frankel, "Using HMAC-SHA-256, HMAC-SHA-
              384, and HMAC-SHA-512 with IPsec", RFC 4868,
              DOI 10.17487/RFC4868, May 2007,
              <https://www.rfc-editor.org/info/rfc4868>.

   [RFC5905]  Mills, D., Martin, J., Ed., Burbank, J., and W. Kasch,
              "Network Time Protocol Version 4: Protocol and Algorithms
              Specification", RFC 5905, DOI 10.17487/RFC5905, June 2010,
              <https://www.rfc-editor.org/info/rfc5905>.

   [TS23501]  3GPP (3rd Generation Partnership Project), "Technical
              Specification Group Services and System Aspects; System
              Architecture for the 5G System; Stage 2 (Release 16)",
              3GPP TS23501, 2019.






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Authors' Addresses

   Greg Mirsky
   ZTE Corp.

   Email: gregimirsky@gmail.com


   Xiao Min
   ZTE Corp.

   Email: xiao.min2@zte.com.cn


   Henrik Nydell
   Accedian Networks

   Email: hnydell@accedian.com


   Richard Foote
   Nokia

   Email: footer.foote@nokia.com


   Adi Masputra
   Apple Inc.
   One Apple Park Way
   Cupertino, CA  95014
   USA

   Email: adi@apple.com


   Ernesto Ruffini
   OutSys
   via Caracciolo, 65
   Milano  20155
   Italy

   Email: eruffini@outsys.org









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