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

The fields are defined as follows:¶

STAMP TLV Flags:

An eight-bit-long field. Its format is presented in Figure 6.¶

Type:

A one-octet-long field. Value 1 has been allocated by IANA (Section 5.1).¶

Length:

A two-octet-long 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 [RFC5357]. 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 [RFC8762]. 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.¶

4.2. 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 Section 4 for a malformed 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-long field. Its format is presented in Figure 6.¶

Type:

A one-octet-long field. Value 2 has been allocated by IANA (Section 5.1).¶

Length:

A two-octet-long field equal to the length of the Value field in octets.¶

Destination Port:

A two-octet-long UDP destination port number of the received STAMP packet.¶

Source Port:

A two-octet-long 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.¶

4.3. 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 Section 4 for a malformed 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-long field. Its format is presented in Figure 6.¶

Type:

A one-octet-long field. Value 3 has been allocated by IANA (Section 5.1).¶

Length:

A two-octet-long field, set equal to the length of the Value field in octets (Figure 5).¶

Sync Src In:

A one-octet-long 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) [RFC5905]. Table 7 lists the possible values.¶

Timestamp In:

A one-octet-long 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"). Table 9 lists the possible values.¶

Sync Src Out:

A one-octet-long field that characterizes the source of clock synchronization at the egress of the Session-Reflector. Table 7 lists the possible values.¶

Timestamp Out:

A one-octet-long field that characterizes the method by which the egress of the Session-Reflector obtained the timestamp T3. Table 9 lists the possible values.¶

Optional sub-TLVs:

An optional variable-length field.¶

4.4. 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 Figure 12.¶

    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-long field. Its format is presented in Figure 6.¶

Type:

A one-octet-long field. Value 4 has been allocated by IANA (Section 5.1).¶

Length:

A two-octet-long 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-long field. A Session-Sender MUST set the value of the RP field to 0 on transmission.¶

Reserved:

A 16-bit-long 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.¶

4.5. 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.¶

    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-long field. Its format is presented in Figure 6.¶

Type:

A one-octet-long field. Value 5 has been allocated by IANA (Section 5.1).¶

Length:

A two-octet-long 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-long 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-long 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-long 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.¶

4.6. Access Report TLV

A STAMP Session-Sender MAY include an Access Report TLV (Figure 14) 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
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |STAMP TLV Flags|     Type      |           Length              |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |   ID  |  Resv |  Return Code  |          Reserved             |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

The fields are defined as follows:¶

STAMP TLV Flags:

An eight-bit-long field. Its format is presented in Figure 6.¶

Type:

A one-octet-long field. Value 6 has been allocated by IANA (Section 5.1).¶

Length:

A two-octet-long field, set equal to the value 4.¶

ID (Access ID):

A four-bit-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 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-long field that MUST be zeroed on transmission and ignored on receipt.¶

Return Code:

A one-octet-long 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. Section 5.6 lists the possible values.¶

Reserved:

A two-octet-long 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 [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 only an "SW Local" (see Table 9) 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 Section 4.2 of [RFC8762]), it MUST zero the Sequence Number and Follow-Up 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
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |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-long field. Its format is presented in Figure 6.¶

Type:

A one-octet-long field. Value 7 has been allocated by IANA (Section 5.1).¶

Length:

A two-octet-long field, set equal to the value 16 octets.¶

Sequence Number:

A four-octet-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 of [RFC8762]), it is the Session-Reflector's Sequence Number of the previous reflected packet.¶

Follow-Up Timestamp:

An eight-octet-long 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 Section 4.2.1 of [RFC8762]. It carries the timestamp when the reflected packet with the specified sequence number was sent.¶

Timestamp M(ode):

A one-octet-long field that characterizes the method by which the entity that transmits a reflected STAMP packet obtained the Follow-Up Timestamp. Table 9 lists the possible values.¶

Reserved:

A three-octet-long field. Its value MUST be zeroed on transmission and ignored on receipt.¶

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. All authenticated STAMP base packets (per Sections 4.2.2 and 4.3.2 of [RFC8762]) 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.¶

    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-long field. Its format is presented in Figure 6.¶

Type:

A one-octet-long field. Value 8 has been allocated by IANA (Section 5.1).¶

Length:

A two-octet-long field, set equal to the value 16 octets.¶

HMAC:

A 16-octet-long field that carries the HMAC digest of the text of all preceding TLVs.¶

As defined in [RFC8762], STAMP uses HMAC-SHA-256 truncated to 128 bits (see [RFC4868]). All considerations regarding using the key listed in Section 4.4 of [RFC8762] 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 [RFC8762], including the use of more advanced cryptographic algorithms. HMAC is calculated as defined in [RFC2104] 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.¶

5.1. 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 [RFC8126] described in Table 1.¶

Per this document, IANA has allocated the following values in the "STAMP TLV Types" subregistry:¶

5.2. STAMP TLV Flags Subregistry

IANA has created the "STAMP TLV Flags" subregistry. The registration procedure is "IETF Review" [RFC8126]. The flags are 8 bits. Per this document, IANA has allocated the following bit positions in the "STAMP TLV Flags" subregistry.¶

5.3. 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 [RFC8126] described in Table 4.¶

Per this document, IANA has allocated the following values in the "STAMP Sub-TLV Types" subregistry:¶

5.4. 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 [RFC8126] described in Table 6.¶

Per this document, IANA has allocated the following values in the "STAMP Synchronization Sources" subregistry:¶

5.5. 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 [RFC8126] described in Table 8.¶

Per this document, IANA has allocated the following values in the "STAMP Timestamping Methods" subregistry:¶

5.6. 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 [RFC8126] described in Table 10.¶

Per this document, IANA has allocated the following values in the "STAMP Return Codes" subregistry:¶