Simple Two-Way Active Measurement Protocol Optional Extensions

Simple Two-Way Active Measurement Protocol Optional Extensions ZTE Corp.


        gregimirsky@gmail.com


    
      ZTE Corp.
      
        
          
          
          
          
        
        xiao.min2@zte.com.cn
      

    
    
      Accedian Networks
      
        
          
          
          
          
        
        hnydell@accedian.com
      

    
    
      Nokia
      
        footer.foote@nokia.com
      
    
    
      Apple Inc.
      
        
          One Apple Park Way
          Cupertino
          CA
          95014
          United States of America
        
        adi@apple.com
      
    
    
      OutSys
      
        
          via Caracciolo, 65
          Milan
          20155
          Italy
        
        eruffini@outsys.org
      
    
    
    Transport
    IPPM
    IPPM
    Performance Measurement
    
      
	This document describes optional extensions to Simple
	Two-way Active Measurement Protocol (STAMP) that enable
	measurement of performance metrics. The document also defines
	a STAMP Test Session Identifier and thus updates RFC 8762.
      
    
    
      
        Status of This Memo
        
            This is an Internet Standards Track document.
        
        
            This document is a product of the Internet Engineering Task Force
            (IETF).  It represents the consensus of the IETF community.  It has
            received public review and has been approved for publication by
            the Internet Engineering Steering Group (IESG).  Further
            information on Internet Standards is available in Section 2 of 
            RFC 7841.
        
        
            Information about the current status of this document, any
            errata, and how to provide feedback on it may be obtained at
            .
        
      
      
        Copyright Notice
        
            Copyright (c) 2021 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
            () 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
        
          
            .  Introduction
          
          
            .  Conventions Used in This Document
            
              
                .  Acronyms
              
              
                .  Requirements Language
              
            
          
          
            .  STAMP Test Session Identifier
          
          
            .  TLV Extensions to STAMP
            
              
                .  Extra Padding TLV
              
              
                .  Location TLV
                
                  
                    .  Location Sub-TLVs
                  
                  
                    .  Theory of Operation of Location TLV
                  
                
              
              
                .  Timestamp Information TLV
              
              
                .  Class of Service TLV
              
              
                .  Direct Measurement TLV
              
              
                .  Access Report TLV
              
              
                .  Follow-Up Telemetry TLV
              
              
                .  HMAC TLV
              
            
          
          
            .  IANA Considerations
            
              
                .  STAMP TLV Types Subregistry
              
              
                .  STAMP TLV Flags Subregistry
              
              
                .  STAMP Sub-TLV Types Subregistry
              
              
                .  STAMP Synchronization Sources Subregistry
              
              
                .  STAMP Timestamping Methods Subregistry
              
              
                .  STAMP Return Codes Subregistry
              
            
          
          
            .  Security Considerations
          
          
            .  References
            
              
                .  Normative References
              
              
                .  Informative References
              
            
          
          
            Acknowledgments
          
          
            Contributors
          
          
            Authors' Addresses


  
    
      Introduction
      
The Simple Two-way Active Measurement Protocol (STAMP)  defines the STAMP base functionalities.
This document specifies 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, packet duplication, and
   out-of-order delivery of test packets. This specification defines
optional STAMP extensions, their formats, and the theory of operation.
Also, a STAMP Test Session Identifier is defined
as an update of the base STAMP specification .
      
    
    
      Conventions Used in This Document
      
        Acronyms
        
          BDS
          BeiDou Navigation Satellite System
          BITS
          Building Integrated Timing Supply
          CoS
          Class of Service
          DSCP
          Differentiated Services Code Point
          ECN
          Explicit Congestion Notification
          GLONASS
          Global Orbiting Navigation Satellite System
          GPS
          Global Positioning System 
          HMAC
          Hashed Message Authentication Code
          LORAN-C
          Long Range Navigation System Version C
          MBZ
          Must Be Zero
          NTP
          Network Time Protocol 
          PMF
          Performance Measurement Function
          PTP
          Precision Time Protocol 
          RP
          Reverse Path
          SMI
          Structure of Management Information
          SSID
          STAMP Session Identifier
          SSU
          Synchronization Supply Unit
          STAMP
          Simple Two-way Active Measurement Protocol
          TLV
          Type-Length-Value
        
      
      
        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   
    when, and only when, they appear in all capitals, as shown here.
        
      
    
    
      STAMP Test Session Identifier
      
The STAMP Session-Sender transmits test packets to the STAMP Session-Reflector. The STAMP Session-Reflector
receives the 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 
   packets.

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

      
  A STAMP Session is identified by the 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).
  The SSID is a two-octet, non-zero unsigned integer. The SSID generation
   policy is implementation specific.  thoroughly analyzes common algorithms for identifier generation and their vulnerabilities.
   For example, an implementation can use the algorithms described in .
   An implementation MUST NOT assign the same identifier to different STAMP test sessions.
  A Session-Sender MAY use the SSID to identify
  a STAMP test session. If the SSID is used, it MUST be present in each test packet of the given test session.
  In the unauthenticated mode, the SSID is located as displayed in .
      
      
        The Format of an Extended STAMP Session-Sender Test Packet in Unauthenticated Mode
        
    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                        Sequence Number                        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                          Timestamp                            |
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |         Error Estimate        |             SSID              |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                                                               |
   |                                                               |
   |                         MBZ (28 octets)                       |
   |                                                               |
   |                                                               |
   |                                                               |
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   ~                            TLVs                               ~
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

      
      
  An implementation of the STAMP Session-Reflector that supports this specification MUST
   identify a STAMP Session using the SSID in combination with elements of the usual 4-tuple
   for the session. Before a test session commences, a Session-Reflector MUST be provisioned
   with all the elements that identify the STAMP Session. A STAMP Session-Reflector MUST discard
   non-matching STAMP test packets. The means of provisioning the STAMP Session identification
   is outside the scope of this specification.

   A conforming implementation of a STAMP Session-Reflector MUST copy
  the SSID value from the received test packet and put it into the reflected packet,
  as displayed in .
      
      
        The Format of an Extended STAMP Session-Reflector Test Packet in Unauthenticated Mode
        
  0                   1                   2                   3
  0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |                        Sequence Number                        |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |                          Timestamp                            |
 |                                                               |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |         Error Estimate        |           SSID                |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |                          Receive Timestamp                    |
 |                                                               |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |                 Session-Sender Sequence Number                |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |                  Session-Sender Timestamp                     |
 |                                                               |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 | Session-Sender Error Estimate |           MBZ                 |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |Ses-Sender TTL |                   MBZ                         |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 ~                            TLVs                               ~
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

      
      
        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 MAY stop the session if it receives a zeroed SSID field. An implementation
 of a Session-Sender MUST support control of its behavior in such a scenario.
 If the test session is not stopped, the Session-Sender can, for example,
 send a base STAMP packet  or continue transmitting STAMP test packets with the SSID.

      
 The location of the SSID field in the authenticated mode
  is shown in Figures  and .
      
      
        The Format of an Extended STAMP Session-Sender Test Packet 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 (68 octets)                       |
 ~                                                               ~
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |                                                               |
 |                       HMAC (16 octets)                        |
 |                                                               |
 |                                                               |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 ~                            TLVs                               ~
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

      
      
        The Format of an Extended STAMP Session-Reflector Test Packet 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)                         |
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                 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)                       |
   |                                                               |
   |                                                               |
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   ~                            TLVs                               ~
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  
      
    
    
      TLV Extensions to STAMP
      
The 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 a STAMP test packet. Additional TLVs
may be enclosed within a given TLV, subject to the semantics of the
(outer) TLV in question.
 TLVs have a one-octet STAMP TLV Flags field, a one-octet Type field, and
  a two-octet Length field that is equal to the length of the Value field in octets.
   If a Type value for a TLV or sub-TLV is in the range for
   Private Use , the length MUST be at least 4, and the first four octets
   MUST be that vendor's Structure of
   Management Information (SMI) Private Enterprise Code, as recorded in
   IANA's "SMI Network Management Private Enterprise Codes" subregistry, in network octet
   order. The rest of the Value field is private to the vendor.
The following sections describe the use of TLVs for STAMP
that extend the STAMP capability beyond its base specification.
      
      
        TLV Format in a STAMP Extended Packet
        
    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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |STAMP TLV Flags|     Type      |           Length              |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   ~                            Value                              ~
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

      
      
       The fields are defined as follows:
      
      
        STAMP TLV Flags:
        An eight-bit field. The detailed format and interpretation of flags defined in this specification are below.
        Type:
        A one-octet field that characterizes the interpretation of
        the Value field. It is allocated by IANA, as specified in .
        Length:
        A two-octet field equal to the length of the Value field in octets.
        Value:
        A variable-length field. Its interpretation and encoding are determined by the value of the Type field.
      
      
       All multi-byte fields in TLVs defined in this specification are in network byte order.
      
      
The format of the STAMP TLV Flags is displayed in , and the location of flags is defined in .
      
      
        STAMP TLV Flags Format
        
    0 1 2 3 4 5 6 7
   +-+-+-+-+-+-+-+-+
   |U|M|I|R|R|R|R|R|
   +-+-+-+-+-+-+-+-+

      
      
      The fields are defined as follows:
      
      
        U (Unrecognized):
        A one-bit flag.
        A Session-Sender MUST set the U flag to 1 before transmitting an extended STAMP test packet.
        A Session-Reflector MUST set the U flag to 1 if the Session-Reflector has not understood the TLV.
        Otherwise, the Session-Reflector MUST set the U flag in the reflected packet to 0.
        M (Malformed):
        A one-bit flag.
        A Session-Sender MUST set the M flag to 0 before transmitting an extended STAMP test packet.
        A Session-Reflector MUST set the M flag to 1 if the Session-Reflector determined the TLV is malformed,
        i.e., the Length field value is not valid for the particular type, or
        the remaining length of the extended STAMP packet is less than the size of the TLV.
        Otherwise, the Session-Reflector MUST set the M flag in the reflected packet to 0.
        
        I (Integrity):
        A one-bit flag.
        A Session-Sender MUST set the I flag to 0 before transmitting an extended STAMP test packet.
        A Session-Reflector MUST set the I flag to 1 if the STAMP extensions have failed HMAC verification ().
        Otherwise, the Session-Reflector MUST set the I flag in the reflected packet to 0.
        R:
        Reserved flags for future use. These flags MUST be zeroed on transmit and ignored on receipt.
      
      
A STAMP node, whether Session-Sender or Session-Reflector, receiving a test packet MUST
determine whether the packet is a base STAMP packet or whether it 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
greater than the length of the UDP header, then the test packet includes one or more STAMP TLVs
that immediately follow the base STAMP test packet.
A Session-Reflector that does not support STAMP extensions will not process but
copy them into the reflected packet, as defined in .
A Session-Reflector that supports TLVs will indicate specific TLVs that
it did not process by setting the U flag to 1 in those TLVs.

      
A STAMP Session-Sender that has received a reflected STAMP test packet with extension TLVs MUST validate each TLV:

      
        
If the U flag is set, the STAMP system MUST skip the processing of the TLV.

        
If the M flag is set, the STAMP system MUST stop processing the remainder of the extended STAMP packet.

        
If the I flag is set, the STAMP system MUST discard all TLVs and
MUST stop processing the remainder of the extended STAMP packet.

        
If an implementation of a Session-Reflector does not recognize the Type field value,
it MUST include a copy of the TLV in the reflected STAMP packet.
The Session-Reflector MUST set the U flag to 1.
The Session-Reflector MUST skip the processing of the unrecognized TLV.
 
        
If a TLV is malformed, the processing of extension TLVs MUST be
stopped. The Session-Reflector MUST copy the remainder of the received extended STAMP packet into the reflected STAMP packet.
The Session-Reflector MUST set the M flag to 1.

      
      

      
        Extra Padding TLV
        
          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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
   |STAMP TLV Flags|      Type     |           Length              |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                                                               |
   ~                         Extra Padding                         ~
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

        
         
        The fields are defined as follows:
        
        
          STAMP TLV Flags:
          An eight-bit field. Its format is presented in .
          Type:
          A one-octet field. Value 1 has been allocated by IANA ().
          Length:
          A two-octet field equal to the length of the Extra Padding field in octets.
          Extra Padding:
          This field SHOULD be filled by a sequence of pseudorandom numbers. The field MAY be filled with all zeros.
       An implementation MUST control the content of the Extra Padding field.
        
        
  The Extra Padding TLV is similar to the Packet Padding field in a TWAMP-Test packet .
  The use of the Extra Padding TLV is RECOMMENDED to perform a STAMP test using 
  test packets that are larger than the base STAMP packet
  . The length of the base STAMP packet is 44 octets
  in the unauthenticated mode or 112 octets in the authenticated mode.
  The Extra Padding TLV MAY be present more than one time in an extended STAMP test packet.
        
      
      
        Location TLV
        
  STAMP Session-Senders MAY include the variable-size Location TLV to query location information from the Session-Reflector.
  The Session-Sender MUST NOT fill any information fields except for the STAMP TLV Flags, Type, and Length fields.
  The Session-Reflector MUST verify that the TLV is well formed. If it is not, the Session-Reflector follows the procedure defined in 
  for a malformed TLV.
        
        
          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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
   |STAMP TLV Flags|      Type     |           Length              |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |        Destination Port       |          Source Port          |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   ~                         Sub-TLVs                              ~
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

        
         
        The fields are defined as follows:
        
        
          STAMP TLV Flags:
          An eight-bit field. Its format is presented in .
          Type:
          A one-octet field. Value 2 has been allocated by IANA ().
          Length:
          A two-octet field equal to the length of the Value field in octets.
          Destination Port:
          A two-octet UDP destination port number of the received STAMP packet.
          Source Port:
          A two-octet UDP source port number of the received STAMP packet.
          Sub-TLVs:
          A sequence of sub-TLVs, as defined further in this section. The sub-TLVs are used by the
        Session-Sender to request location information with generic sub-TLV types, and the
        Session-Reflector responds with the corresponding more-specific sub-TLVs
        for the type of address (e.g., IPv4 or IPv6) used at the Session-Reflector.
        
        Note that all fields not filled by either a Session-Sender or Session-Reflector are transmitted with all bits set to zero.
        
          Location Sub-TLVs
          
  A sub-TLV in the Location TLV uses the format displayed in .
  Handling of the U and M flags in the sub-TLV is as defined in .
  The I flag MUST be set by a Session-Sender and Session-Reflector to 0 before transmission and its value ignored on receipt.
  The following types of sub-TLVs for the Location TLV are defined in this specification
  ( lists the Type values):
          
          
            Source MAC Address sub-TLV:
            A 12-octet sub-TLV.
  The Type value is 1.
  The value of the Length field MUST be equal to 8.
  The Value field is an 8-octet MBZ field that MUST be zeroed on transmission and ignored on receipt.
  
            
    Source EUI-48 Address sub-TLV:
            
              A 12-octet sub-TLV that includes the EUI-48 source MAC address.
  The Type value is 2.
  The value of the Length field MUST be equal to 8.
              
                The Value Field of the Source EUI-48 Address Sub-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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
|                        EUI-48  Address                        |
+                               +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|                               |            MBZ                |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

              
               
  The Value field consists of the following fields ():
              
              
                EUI-48 Address:
                A six-octet field.
                MBZ:
                A two-octet field. It MUST be zeroed on transmission and ignored on receipt.
              
            
            Source EUI-64 Address sub-TLV:
            A 12-octet sub-TLV that includes the EUI-64 source MAC address.
  The Type value is 3.
  The value of the Length field MUST be equal to 8.
  The Value field consists of an eight-octet EUI-64 field.
  
            
        Destination IP Address sub-TLV:
            A 20-octet sub-TLV.
        The Type value is 4.
        The value of the Length field MUST be equal to 16.
        The Value field consists of a 16-octet  MBZ field that MUST be zeroed on transmit and ignored on receipt.
        
                        
        Destination IPv4 Address sub-TLV:
            
              A 20-octet sub-TLV that includes the IPv4 destination address.
        The Type value is 5.
        The value of the Length field MUST be equal to 16.
              
                IPv4 Address in a Sub-TLV's Value Field
                
 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
|                         IPv4 Address                          |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
~                        MBZ (12 octets)                        ~
|                                                               |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

              
               
        The Value field consists of the following fields ():
              
              
                IPv4 Address:
                A four-octet field.
                MBZ:
                A 12-octet field. It MUST be zeroed on transmit and ignored on receipt.
              
            
            
        Destination IPv6 Address sub-TLV:
            A 20-octet sub-TLV that includes the IPv6 destination address.
        The Type value is 6.
        The value of the Length field MUST be equal to 16.
        The Value field is a 16-octet IPv6 Address field.
        
            
        Source IP Address sub-TLV:
            A 20-octet sub-TLV.
        The Type value is 7.
        The value of the Length field MUST be equal to 16.
        The Value field is a 16-octet MBZ field that MUST be zeroed on transmit and ignored on receipt.
        
            
        Source IPv4 Address sub-TLV:
            
              A 20-octet sub-TLV that includes the IPv4 source address.
        The Type value is 8.
        The value of the Length field MUST be equal to 16.
        The Value field consists of the following fields ():
              
                IPv4 Address:
                A four-octet field.
                MBZ:
                A 12-octet field. It MUST be zeroed on transmit and ignored on receipt.
              
            
            
        Source IPv6 Address sub-TLV:
            A 20-octet sub-TLV that includes the IPv6 source address.
        The Type value is 9.
        The value of the Length field MUST be equal to 16.
        The Value field is a 16-octet IPv6 Address field.
        
          
        
        
          Theory of Operation of Location TLV
          

  The Session-Reflector that received an extended STAMP packet with
  the Location TLV MUST include in the reflected packet the Location TLV with a length equal
  to the Location TLV length in the received packet.
  Based on the local policy, the Session-Reflector MAY leave some fields unreported by filling them with zeroes.
  An implementation of the stateful Session-Reflector MUST provide control for managing such policies.
          
          
  A Session-Sender MAY include the Source MAC Address sub-TLV in the Location TLV.
  If the Session-Reflector receives the Location TLV that includes the Source MAC Address sub-TLV, it
  MUST include the Source EUI-48 Address sub-TLV if the source MAC address of the
  received extended test packet is in EUI-48 format. And the Session-Reflector MUST
  copy the value of the source MAC address in the EUI-48 field.
  Otherwise, the Session-Reflector MUST use the Source EUI-64 Address sub-TLV and MUST copy the value
  of the Source MAC Address from the received packet into the EUI-64 field.
  If the received extended STAMP test packet does not have the Source MAC Address,
  the Session-Reflector MUST zero the EUI-64 field before transmitting the reflected packet.
          
          
  A Session-Sender MAY include the Destination IP Address sub-TLV in the Location TLV.
  If the Session-Reflector receives the Location TLV that includes the Destination IP Address sub-TLV, it
  MUST include the Destination IPv4 Address sub-TLV if the source IP address of the
  received extended test packet is of the IPv4 address family. And the Session-Reflector MUST
  copy the value of the destination IP address in the IPv4 Address field.
  Otherwise, the Session-Reflector MUST use the Destination IPv6 Address sub-TLV and MUST copy the value
  of the destination IP address from the received packet into the IPv6 Address field.
          
          
  A Session-Sender MAY include the Source IP Address sub-TLV in the Location TLV.
  If the Session-Reflector receives the Location TLV that includes the Source IP Address sub-TLV, it
  MUST include the Source IPv4 Address sub-TLV if the source IP address of the
  received extended test packet is of the IPv4 address family. And the Session-Reflector MUST
  copy the value of the source IP address in the IPv4 Address field.
  Otherwise, the Session-Reflector MUST use the Source IPv6 Address sub-TLV and MUST copy the value
  of the source IP address from the received packet into the IPv6 Address field.
          
          
The Location TLV MAY be used to determine the last-hop IP addresses, ports, and
  last-hop MAC address for STAMP packets. The MAC address can indicate a path switch
  on the last hop. The IP addresses and UDP ports will indicate
  if there is a NAT router on the path. It allows the Session-Sender to identify the IP address
  of the Session-Reflector behind the NAT and detect changes in the NAT mapping that could result in sending the STAMP packets to the wrong Session-Reflector.
          
        
      
      
        Timestamp Information TLV
        
  The STAMP Session-Sender MAY include the Timestamp Information TLV to request information from the Session-Reflector.
  The Session-Sender MUST NOT fill any information fields except for STAMP TLV Flags, Type, and Length.
  All other fields MUST be filled with zeroes.
  The Session-Reflector MUST validate the Length value of the TLV.
  If the value of the Length field is invalid, the Session-Reflector follows the procedure defined in  for a malformed TLV.
  
        
        
          Timestamp Information 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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
   |STAMP TLV Flags|      Type     |           Length              |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |  Sync Src In  | Timestamp In  | Sync Src Out  | Timestamp Out |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   ~                    Optional sub-TLVs                          ~
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

        
         
        The fields are defined as follows:
        
        
          STAMP TLV Flags:
          An eight-bit field. Its format is presented in .
          Type:
          A one-octet field. Value 3 has been allocated by IANA ().
          Length:
          A two-octet field, set equal to the length of the Value field in octets ().
          Sync Src In:
          A one-octet field that characterizes the source of clock synchronization at the ingress of a Session-Reflector. 
       There are several methods for synchronizing the clock, e.g., the Network Time Protocol (NTP) .

        lists the possible values.
          Timestamp In:
          A one-octet field that characterizes the
       method by which the ingress of the Session-Reflector obtained the timestamp T2.
       A timestamp may be obtained with hardware assistance via a software API from a local wall clock or from a remote clock (the latter is referred to as a "control plane").
 lists the possible values.
          Sync Src Out:
          A one-octet field that characterizes the source of clock synchronization at the egress of the Session-Reflector. 
 lists the possible values.
          Timestamp Out:
          A one-octet field that characterizes the
       method by which the egress of the Session-Reflector obtained the timestamp T3.
 lists the possible values.
          Optional sub-TLVs:
          An optional variable-length field.
        
      
      
        Class of Service TLV
        
  The STAMP Session-Sender MAY include  a Class of Service (CoS) TLV in the STAMP test packet.
  The format of the CoS TLV is presented in .

        
        
          Class of Service 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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
   |STAMP TLV Flags|      Type     |           Length              |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
   |   DSCP1   |   DSCP2   |ECN| RP|          Reserved             |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

        
         
        The fields are defined as follows:
        
        
          STAMP TLV Flags:
          An eight-bit field. Its format is presented in .
          Type:
          A one-octet field. Value 4 has been allocated by IANA ().
          Length:
          A two-octet field, set equal to the value 4.
          DSCP1:
          The Differentiated Services Code Point (DSCP) intended by the Session-Sender
        to be used as the DSCP value of the reflected test packet.
          DSCP2:
          The received value in the DSCP field at the ingress of the Session-Reflector.
          ECN:
          The received value in the ECN field at the ingress of the Session-Reflector.
          RP (Reverse Path):
          A two-bit field. A Session-Sender MUST set the value of the RP field to 0 on transmission.
          Reserved:
          A 16-bit field that MUST be zeroed on transmission and ignored on receipt.
        
        
  A STAMP Session-Reflector that receives a 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 and ECN fields of the IP header of the received STAMP test packet into the DSCP2 field in
  the reflected test packet. Finally, the Session-Reflector MUST use the local policy to verify whether
  the CoS corresponding to the value of the DSCP1 field is permitted in the domain. If it is, the Session-Reflector
  MUST set the 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. Otherwise, the Session-Reflector MUST use
  the DSCP value of the received STAMP packet and set the value of the RP field to 1.
  Upon receiving the reflected packet, if the value of the RP field is 0,
  the Session-Sender will save the DSCP and ECN values for analysis of the CoS in the reverse direction.
  If the value of the RP field in the received reflected packet is 1, only CoS in the forward direction can be analyzed.
        
        
Re-mapping of CoS can be used to provide multiple services (e.g., 2G, 3G, LTE in mobile backhaul networks)
over the same network.  But if it is misconfigured, then it is often difficult to diagnose the root cause of
excessive packet drops of higher-level service while packet drops
for lower service packets are at a normal level.  Using a CoS TLV in
STAMP testing helps to troubleshoot the existing problem and also verify
whether Diffserv policies are processing CoS as required by the configuration.
        
      
      
        Direct Measurement TLV
        
  The Direct Measurement TLV enables collection of the number of in-profile packets,
  i.e., packets that form a specific data flow, that had been transmitted and received
  by the Session-Sender and Session-Reflector, respectively. The definition of "in-profile packet" is outside the
  scope of this document and is left to the test operators to determine.
        
        
          Direct Measurement 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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
   |STAMP TLV Flags|      Type     |           Length              |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |              Session-Sender Tx counter  (S_TxC)               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |             Session-Reflector Rx counter  (R_RxC)             |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |             Session-Reflector Tx counter  (R_TxC)             |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

        
         
        The fields are defined as follows:
        
        
          STAMP TLV Flags:
          An eight-bit field. Its format is presented in .
          Type:
          A one-octet field. Value 5 has been allocated by IANA ().
          Length:
          A two-octet field equal to the length of the Value field in octets. The Length field value MUST equal 12 octets.
          Session-Sender Tx counter (S_TxC):
          A four-octet field. The Session-Sender MUST set its value equal to the number of the transmitted in-profile packets.
          Session-Reflector Rx counter (R_RxC):
          A four-octet field. It MUST be zeroed  by the Session-Sender on transmit and
       ignored by the Session-Reflector on receipt. The Session-Reflector MUST fill it with the value of in-profile packets received.
          Session-Reflector Tx counter (R_TxC):
          A four-octet field. It MUST be zeroed by the Session-Sender and ignored by the Session-Reflector on receipt.
       The Session-Reflector MUST fill it with the value of the transmitted in-profile packets.
        
        
    A Session-Sender MAY include the Direct Measurement TLV in a STAMP test packet.
    If the received STAMP test packet includes the Direct Measurement TLV, the Session-Reflector MUST include it in the reflected test packet.
    The Session-Reflector MUST copy the value from the S_TxC field of the received test packet into the same field of the reflected packet before its transmission.
        
      
      
        Access Report TLV
        
    A STAMP Session-Sender MAY include an Access Report TLV () 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.
        
        
          Access Report 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
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |STAMP TLV Flags|     Type      |           Length              |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |   ID  |  Resv |  Return Code  |          Reserved             |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

        
         
        The fields are defined as follows:
        
        
          STAMP TLV Flags:
          An eight-bit field. Its format is presented in .
          Type:
          A one-octet field. Value 6 has been allocated by IANA ().
          Length:
          A two-octet field, set equal to the value 4.
          ID (Access ID):
          
            A four-bit 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) .
     The value is one of the following:
            
              1:
              3GPP Network
              2:
              Non-3GPP Network
            
            
     All other values are invalid; a TLV that contains values other than '1' or '2' MUST be discarded.
          
          Resv:
          A four-bit field that MUST be zeroed on transmission
      and ignored on receipt.
          Return Code:
          A one-octet field that identifies the report signal,
     e.g., available or unavailable. The value is supplied to the STAMP
     endpoint through some mechanism that is outside the scope of this document.
 lists the possible values.
          Reserved:
          A two-octet field that MUST be zeroed on transmission
      and ignored on receipt.
        
        
           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 reception of the reflected
   STAMP test packet that includes the 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 and the network environment.
   The default value of the retransmission timer for the 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 .  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.
        
      
      
        Follow-Up Telemetry TLV
        
    A Session-Reflector might be able to put only an "SW Local"
    (see ) timestamp in the Follow-Up Timestamp field. But the hosting
    system might provide a timestamp closer to the start of the actual packet transmission
    even though it is not possible to deliver the information to the Session-Sender in time for the packet itself.
    This timestamp might nevertheless be important for the Session-Sender, as it
    improves the accuracy of network delay measurement 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.
   The Sequence Number and Follow-Up 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 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 the Sequence Number and Follow-Up Timestamp fields and set the M flag in the STAMP TLV Flags field
   in the reflected packet. If the Session-Reflector is in the
   stateless mode (defined in ),
   it MUST zero the Sequence Number and Follow-Up Timestamp fields.
        
        
          Follow-Up Telemetry 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
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |STAMP TLV Flags|      Type     |           Length              |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                        Sequence Number                        |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                      Follow-Up Timestamp                      |
    |                                                               |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |  Timestamp M  |                     Reserved                  |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

        
         
        The fields are defined as follows:
        
        
          STAMP TLV Flags:
          An eight-bit field. Its format is presented in .
          Type:
          A one-octet field. Value 7 has been allocated by IANA ().
          Length:
          A two-octet field, set equal to the value 16 octets.
          
        Sequence Number:
          A four-octet 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 ),
it is the Session-Reflector's Sequence Number of the previous reflected packet.

          
     Follow-Up Timestamp:
          An eight-octet field, with the format indicated by
      the Z flag of the Error Estimate field of the STAMP base packet, which is contained
      in this reflected test packet transmitted by a Session-Reflector,
      as described in .
      It carries the timestamp when the reflected packet with the
      specified sequence number was sent.

          
Timestamp M(ode):
          A one-octet field that characterizes the
method by which the entity that transmits a reflected STAMP packet obtained the Follow-Up Timestamp.
 lists the possible values.

          Reserved:
          A three-octet field. Its value MUST be zeroed on transmission and ignored on receipt.
        
      
      
        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. 
All authenticated STAMP base packets (per Sections  and  of )
compatible with this specification MUST additionally authenticate the
optional TLVs by including the keyed Hashed Message Authentication Code (HMAC) TLV, with the sole exception of when
there is only one TLV present and it is the Extended Padding TLV.
The HMAC TLV MUST follow all TLVs included in a STAMP test packet except for the Extra Padding TLV.
If the HMAC TLV appears in any other position in a STAMP extended test packet, then the situation
MUST be processed as HMAC verification failure, as defined below in this section.
The HMAC TLV MAY be used to protect the integrity of STAMP extensions in the STAMP unauthenticated mode.
An implementation of STAMP extensions MUST provide controls to enable
the integrity protection of STAMP extensions in the STAMP unauthenticated mode.

        
        
        
          HMAC 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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |STAMP TLV Flags|      Type     |             Length            |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                                                               |
   |                              HMAC                             |
   |                                                               |
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

        
         
        The fields are defined as follows:
        
        
          STAMP TLV Flags:
          An eight-bit field. Its format is presented in .
          Type:
          A one-octet field. Value 8 has been allocated by IANA ().
          Length:
          A two-octet field, set equal to the value 16 octets.
          HMAC:
          A 16-octet field that carries the HMAC digest of the text of all preceding TLVs.
        
        
As defined in , STAMP uses HMAC-SHA-256 truncated to 128 bits (see ).
All considerations regarding using the key listed in 
are fully applicable to the use of the HMAC TLV. Key management and the mechanisms to
distribute the HMAC key are outside the scope of this specification.
The HMAC TLV is anticipated to track updates in the base STAMP protocol ,
including the use of more advanced cryptographic algorithms. HMAC is calculated as defined in 
over text as the concatenation of the Sequence Number field of the base STAMP packet and
all  preceding TLVs. The digest then MUST be truncated to 128 bits and written into the HMAC field.
If the HMAC TLV is present in the extended STAMP test packet, e.g., 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 the Session-Reflector MUST stop processing the received extended STAMP test packet.
The Session-Reflector MUST copy the TLVs from the received  STAMP test packet into the
reflected packet. The Session-Reflector MUST set the I flag in each TLV copied over into
the reflected packet to 1 before transmitting the reflected test packet.
If the Session-Sender receives the extended STAMP test packet with I flag set to 1,
then the Session-Sender MUST stop processing TLVs in the reflected test packet.
If HMAC verification by the Session-Sender fails, then the Session-Sender MUST
stop processing TLVs in the reflected extended STAMP packet.

      
    
    
      IANA Considerations
      IANA has created the following subregistries under the "Simple Two-way Active Measurement Protocol (STAMP) TLV Types" registry.
      
        STAMP TLV Types Subregistry
        
   IANA has created the "STAMP TLV Types" subregistry. The code
   points in this registry are allocated according to the registration
   procedures  described in .
        
        Registration Procedures for the STAMP TLV Types Subregistry
          
          
            
              Range
              Registration Procedures
            
          
          
            
              1 - 175
              IETF Review
            
            
              176 - 239
              First Come First Served
            
            
              240 - 251
              Experimental Use
            
            
              252 - 254
              Private Use
            
          
        
        Per this document, IANA has allocated the following values in the "STAMP TLV Types" subregistry:

        STAMP TLV Types
          
          
            
              Value
              Description
              Reference
            
          
          
            
              0
              Reserved
              RFC 8972
            
            
              1
              Extra Padding
              RFC 8972
            
            
              2
              Location
              RFC 8972
            
            
              3
              Timestamp Information
              RFC 8972
            
            
              4
              Class of Service
              RFC 8972
            
            
              5
              Direct Measurement
              RFC 8972
            
            
              6
              Access Report
              RFC 8972
            
            
              7
              Follow-Up Telemetry
              RFC 8972
            
            
              8
              HMAC
              RFC 8972
            
            
              255
              Reserved
              RFC 8972
            
          
        
      
      
        STAMP TLV Flags Subregistry
        
      IANA has created the "STAMP TLV Flags" subregistry.
      The registration procedure is "IETF Review" . The flags are 8 bits.
      Per this document, IANA has allocated the following bit positions in the "STAMP TLV Flags" subregistry.
        
        STAMP TLV Flags
          
          
            
              Bit position
              Symbol
              Description
              Reference
            
          
          
            
              0
              U
              Unrecognized TLV
              RFC 8972
            
            
              1
              M
              Malformed TLV
              RFC 8972
            
            
              2
              I
              Integrity check failed
              RFC 8972
            
          
        
      
      
        STAMP Sub-TLV Types Subregistry
        
   IANA has created the "STAMP Sub-TLV Types" subregistry.
   The code points in this registry are allocated according to the
   registration procedures  described
   in .
        
        Registration Procedures for the STAMP Sub-TLV Types Subregistry
          
          
            
              Range
              Registration Procedures
            
          
          
            
              1 - 175
              IETF Review
            
            
              176 - 239
              First Come First Served
            
            
              240 - 251
              Experimental Use
            
            
              252 - 254
              Private Use
            
          
        
        Per this document, IANA has allocated the following values in the "STAMP Sub-TLV Types" subregistry:
        STAMP Sub-TLV Types
          
          
            
              Value
              Description
              TLV Used
              Reference
            
          
          
            
              0
              Reserved
              
              RFC 8972
            
            
              1
              Source MAC Address
              Location
              RFC 8972
            
            
              2
              Source EUI-48 Address
              Location
              RFC 8972
            
            
              3
              Source EUI-64 Address
              Location
              RFC 8972
            
            
              4
              Destination IP Address
              Location
              RFC 8972
            
            
              5
              Destination IPv4 Address
              Location
              RFC 8972
            
            
              6
              Destination IPv6 Address
              Location
              RFC 8972
            
            
              7
              Source IP Address
              Location
              RFC 8972
            
            
              8
              Source IPv4 Address
              Location
              RFC 8972
            
            
              9
              Source IPv6 Address
              Location
              RFC 8972
            
            
              255
              Reserved
              
              RFC 8972
            
          
        
      
      
        STAMP Synchronization Sources Subregistry
        
   IANA has created the "STAMP Synchronization Sources" subregistry.
The code points in this registry are allocated according
   to the registration procedures
 described in 
.
        
        Registration Procedures for the STAMP Synchronization Sources Subregistry
          
          
            
              Range
              Registration Procedures
            
          
          
            
              1 - 127
              IETF Review
            
            
              128 - 239
              First Come First Served
            
            
              240 - 249
              Experimental Use
            
            
              250 - 254
              Private Use
            
          
        
        Per this document, IANA has allocated the following values in the "STAMP Synchronization Sources" subregistry:

        STAMP Synchronization Sources
          
          
            
              Value
              Description
              Reference
            
          
          
            
              0
              Reserved
              RFC 8972
            
            
              1
              NTP
              RFC 8972
            
            
              2
              PTP
              RFC 8972
            
            
              3
              SSU/BITS
              RFC 8972
            
            
              4
              GPS/GLONASS/LORAN-C/BDS/Galileo
              RFC 8972
            
            
              5
              Local free-running
              RFC 8972
            
            
              255
              Reserved
              RFC 8972
            
          
        
      
      
        STAMP Timestamping Methods Subregistry
        
   IANA has created the "STAMP Timestamping Methods" subregistry.
The code points in this registry are allocated
   according to the registration procedures

described in
.
        
        Registration Procedures for the STAMP Timestamping Methods Subregistry
          
          
            
              Range
              Registration Procedures
            
          
          
            
              1 - 127
              IETF Review
            
            
              128 - 239
              First Come First Served
            
            
              240 - 249
              Experimental Use
            
            
              250 - 254
              Private Use
            
          
        
        Per this document, IANA has allocated the following values in the "STAMP Timestamping Methods" subregistry:
        STAMP Timestamping Methods
          
          
            
              Value
              Description
              Reference
            
          
          
            
              0
              Reserved
              RFC 8972
            
            
              1
              HW Assist
              RFC 8972
            
            
              2
              SW Local
              RFC 8972
            
            
              3
              Control Plane
              RFC 8972
            
            
              255
              Reserved
              RFC 8972
            
          
        
      
      
        STAMP Return Codes Subregistry
        
   IANA has created the "STAMP Return Codes" subregistry.
The code points in this registry are allocated
   according to the registration procedures  described in
.
        
        Registration Procedures for the STAMP Return Codes Subregistry
          
          
            
              Range
              Registration Procedures
            
          
          
            
              1 - 127
              IETF Review
            
            
              128 - 239
              First Come First Served
            
            
              240 - 249
              Experimental Use
            
            
              250 - 254
              Private Use
            
          
        
        Per this document, IANA has allocated the following values in the "STAMP Return Codes" subregistry:
        STAMP Return Codes
          
          
            
              Value
              Description
              Reference
            
          
          
            
              0
              Reserved
              RFC 8972
            
            
              1
              Network available
              RFC 8972
            
            
              2
              Network unavailable
              RFC 8972
            
            
              255
              Reserved
              RFC 8972
            
          
        
      
    
    
      Security Considerations
      
This document defines extensions to STAMP  and inherits all the security considerations
applicable to the base protocol. Additionally, the HMAC TLV is defined in this document.
Though the HMAC TLV protects the integrity of STAMP extensions, it does not protect against a replay attack.
The use of the HMAC TLV is discussed in detail in .
      
      
     To protect against a malformed TLV, an implementation of a Session-Sender and Session-Reflector MUST:
      
      
        check the setting of the M flag and
        validate the Length field value.
      
      
     As this specification defines the mechanism to test DSCP mapping,
   this document inherits all the security considerations discussed in .
   Monitoring and optional control of DSCP using the CoS TLV may be used across the Internet so that
     the Session-Sender and the Session-Reflector are located in domains that use different CoS profiles. Thus,
     it is essential that an operator verify the set of CoS values that is used in the Session-Reflector's domain.
     Also, an implementation of a Session-Reflector SHOULD support a local policy to confirm whether the value sent by the Session-Sender
     can be used as the value of the DSCP field.  defines the use of that local policy.
      
    
  
  
    
    
      References
      
        Normative References
        
          
            HMAC: Keyed-Hashing for Message Authentication
            
              
            
            
              
            
            
              
            
            
            
              This document describes HMAC, a mechanism for message authentication using cryptographic hash functions. HMAC can be used with any iterative cryptographic hash function, e.g., MD5, SHA-1, in combination with a secret shared key.  The cryptographic strength of HMAC depends on the properties of the underlying hash function.  This memo provides information for the Internet community.  This memo does not specify an Internet standard of any kind
            
          
          
          
        
        
          
            Key words for use in RFCs to Indicate Requirement Levels
            
              
            
            
            
              In many standards track documents several words are used to signify the requirements in the specification.  These words are often capitalized. This document defines these words as they should be interpreted in IETF documents.  This document specifies an Internet Best Current Practices for the Internet Community, and requests discussion and suggestions for improvements.
            
          
          
          
          
        
        
          
            Guidelines for Writing an IANA Considerations Section in RFCs
            
              
            
            
              
            
            
              
            
            
            
              Many protocols make use of points of extensibility that use constants to identify various protocol parameters.  To ensure that the values in these fields do not have conflicting uses and to promote interoperability, their allocations are often coordinated by a central record keeper.  For IETF protocols, that role is filled by the Internet Assigned Numbers Authority (IANA).
              To make assignments in a given registry prudently, guidance describing the conditions under which new values should be assigned, as well as when and how modifications to existing values can be made, is needed.  This document defines a framework for the documentation of these guidelines by specification authors, in order to assure that the provided guidance for the IANA Considerations is clear and addresses the various issues that are likely in the operation of a registry.
              This is the third edition of this document; it obsoletes RFC 5226.
            
          
          
          
          
        
        
          
            Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words
            
              
            
            
            
              RFC 2119 specifies common key words that may be used in protocol  specifications.  This document aims to reduce the ambiguity by clarifying that only UPPERCASE usage of the key words have the  defined special meanings.
            
          
          
          
          
        
        
          
            Simple Two-Way Active Measurement Protocol
            
              
            
            
              
            
            
              
            
            
              
            
            
            
              This document describes the Simple Two-way Active Measurement Protocol (STAMP), which enables the measurement of both one-way and round-trip performance metrics, like delay, delay variation, and packet loss.
            
          
          
          
        
      
      
        Informative References
        
          
            Global Positioning System (GPS) Standard Positioning Service (SPS) Performance Standard
            
              
            
            
          
          
        
        
          
            IEEE Standard for a Precision Clock Synchronization Protocol for Networked Measurement and Control Systems
            
              
            
            
          
          
          
        
        
          
            On the Generation of Transient Numeric Identifiers
            
              SI6 Networks
            
            
              Quarkslab
            
            
            
                 This document performs an analysis of the security and privacy
   implications of different types of "transient numeric identifiers"
   used in IETF protocols, and tries to categorize them based on their
   interoperability requirements and their associated failure severity
   when such requirements are not met.  Subsequently, it provides advice
   on possible algorithms that could be employed to satisfy the
   interoperability requirements of each identifier category, while
   minimizing the negative security and privacy implications, thus
   providing guidance to protocol designers and protocol implementers.
   Finally, it describes a number of algorithms that have been employed
   in real implementations to generate transient numeric identifiers,
   and analyzes their security and privacy properties.  This document is
   a product of the Privacy Enhancement and Assessment Research Group
   (PEARG) in the IRTF.

              
            
          
          
          
          Work in Progress
        
        
          
            Definition of the Differentiated Services Field (DS Field) in the IPv4 and IPv6 Headers
            
              
            
            
              
            
            
              
            
            
              
            
            
            
              This document defines the IP header field, called the DS (for differentiated services) field.  [STANDARDS-TRACK]
            
          
          
          
        
        
          
            Using HMAC-SHA-256, HMAC-SHA-384, and HMAC-SHA-512 with IPsec
            
              
            
            
              
            
            
            
              This specification describes the use of Hashed Message Authentication Mode (HMAC) in conjunction with the SHA-256, SHA-384, and SHA-512 algorithms in IPsec.  These algorithms may be used as the basis for data origin authentication and integrity verification mechanisms for the Authentication Header (AH), Encapsulating Security Payload (ESP), Internet Key Exchange Protocol (IKE), and IKEv2 protocols, and also as Pseudo-Random Functions (PRFs) for IKE and IKEv2.  Truncated output lengths are specified for the authentication-related variants, with the corresponding algorithms designated as HMAC-SHA-256-128, HMAC-SHA-384-192, and HMAC-SHA-512-256.  The PRF variants are not truncated, and are called PRF-HMAC-SHA-256, PRF-HMAC-SHA-384, and PRF-HMAC-SHA-512.  [STANDARDS-TRACK]
            
          
          
          
        
        
          
            A Two-Way Active Measurement Protocol (TWAMP)
            
              
            
            
              
            
            
              
            
            
              
            
            
              
            
            
            
              The One-way Active Measurement Protocol (OWAMP), specified in RFC 4656, provides a common protocol for measuring one-way metrics between network devices.  OWAMP can be used bi-directionally to measure one-way metrics in both directions between two network elements.  However, it does not accommodate round-trip or two-way measurements.  This memo specifies a Two-Way Active Measurement Protocol (TWAMP), based on the OWAMP, that adds two-way or round-trip measurement capabilities.  The TWAMP measurement architecture is usually comprised of two hosts with specific roles, and this allows for some protocol simplifications, making it an attractive alternative in some circumstances.  [STANDARDS-TRACK]
            
          
          
          
        
        
          
            Network Time Protocol Version 4: Protocol and Algorithms Specification
            
              
            
            
              
            
            
              
            
            
              
            
            
            
              The Network Time Protocol (NTP) is widely used to synchronize computer clocks in the Internet.  This document describes NTP version 4 (NTPv4), which is backwards compatible with NTP version 3 (NTPv3), described in RFC 1305, as well as previous versions of the protocol. NTPv4 includes a modified protocol header to accommodate the Internet Protocol version 6 address family.  NTPv4 includes fundamental improvements in the mitigation and discipline algorithms that extend the potential accuracy to the tens of microseconds with modern workstations and fast LANs.  It includes a dynamic server discovery scheme, so that in many cases, specific server configuration is not required.  It corrects certain errors in the NTPv3 design and implementation and includes an optional extension mechanism.   [STANDARDS-TRACK]
            
          
          
          
        
        
          
            Technical Specification Group Services and System Aspects; System Architecture for the 5G System (5GS); Stage 2 (Release 16)
            
              3GPP
            
            
          
          
        
      
    
    
      Acknowledgments
      
         The authors very much appreciate the thorough review and thoughtful comments received from , , , and .
         The authors express their gratitude to  for his comments and valuable suggestions.
         The authors greatly appreciate the comments and thoughtful suggestions received from .
      
    
    
      Contributors
      
 The following individual contributed text to this document:
      
      
        ZTE Corporation
        
          
            68# Zijinghua Road
            Nanjing
            Jiangsu
            210012
            China
          
          +86 18105183663
          guo.jun2@zte.com.cn
        
      
    
    
      Authors' Addresses
      
        ZTE Corp.
        
          
            
            
            
            
          
          gregimirsky@gmail.com
        

      
      
        ZTE Corp.
        
          
            
            
            
            
          
          xiao.min2@zte.com.cn
        

      
      
        Accedian Networks
        
          
            
            
            
            
          
          hnydell@accedian.com
        

      
      
        Nokia
        
          footer.foote@nokia.com
        
      
      
        Apple Inc.
        
          
            One Apple Park Way
            Cupertino
            CA
            95014
            United States of America
          
          adi@apple.com
        
      
      
        OutSys
        
          
            via Caracciolo, 65
            Milan
            20155
            Italy
          
          eruffini@outsys.org

Range	Registration Procedures
1 - 175	IETF Review
176 - 239	First Come First Served
240 - 251	Experimental Use
252 - 254	Private Use

Value	Description	Reference
0	Reserved	RFC 8972
1	Extra Padding	RFC 8972
2	Location	RFC 8972
3	Timestamp Information	RFC 8972
4	Class of Service	RFC 8972
5	Direct Measurement	RFC 8972
6	Access Report	RFC 8972
7	Follow-Up Telemetry	RFC 8972
8	HMAC	RFC 8972
255	Reserved	RFC 8972

Bit position	Symbol	Description	Reference
0	U	Unrecognized TLV	RFC 8972
1	M	Malformed TLV	RFC 8972
2	I	Integrity check failed	RFC 8972

Value	Description	TLV Used	Reference
0	Reserved		RFC 8972
1	Source MAC Address	Location	RFC 8972
2	Source EUI-48 Address	Location	RFC 8972
3	Source EUI-64 Address	Location	RFC 8972
4	Destination IP Address	Location	RFC 8972
5	Destination IPv4 Address	Location	RFC 8972
6	Destination IPv6 Address	Location	RFC 8972
7	Source IP Address	Location	RFC 8972
8	Source IPv4 Address	Location	RFC 8972
9	Source IPv6 Address	Location	RFC 8972
255	Reserved		RFC 8972

Range	Registration Procedures
1 - 127	IETF Review
128 - 239	First Come First Served
240 - 249	Experimental Use
250 - 254	Private Use

Value	Description	Reference
0	Reserved	RFC 8972
1	HW Assist	RFC 8972
2	SW Local	RFC 8972
3	Control Plane	RFC 8972
255	Reserved	RFC 8972

Value	Description	Reference
0	Reserved	RFC 8972
1	Network available	RFC 8972
2	Network unavailable	RFC 8972
255	Reserved	RFC 8972