IP Performance Measurement Group Y. Wang Internet-Draft T. Zhou Intended status: Standards Track Huawei Expires: May 19, 2021 H. Yang China Mobile C. Liu China Unicom November 15, 2020 Simple Two-way Active Measurement Protocol Extensions for Hop-by-Hop OAM Data Collection draft-wang-ippm-stamp-hbh-extensions-02 Abstract This document defines optional TLVs which are carried in Simple Two- way Active Measurement Protocol (STAMP) test packets to enhance the STAMP base functions. Such extensions to STAMP enable OAM data measurement and collection at every node and link along a STAMP test packet's delivery path without maintaining a state for each configured STAMP-Test session at every devices. Requirements Language The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in RFC 2119 [RFC2119]. Status of This Memo This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet- Drafts is at https://datatracker.ietf.org/drafts/current/. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." This Internet-Draft will expire on May 19, 2021. Wang, et al. Expires May 19, 2021 [Page 1] Internet-Draft draft-wang-ippm-stamp-hbh-extensions-02 November 2020 Copyright Notice Copyright (c) 2020 IETF Trust and the persons identified as the document authors. All rights reserved. This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (https://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3 3. TLV Extensions to STAMP . . . . . . . . . . . . . . . . . . . 3 3.1. IOAM Tracing Data TLV . . . . . . . . . . . . . . . . . . 3 3.2. Forward HbH Delay TLV . . . . . . . . . . . . . . . . . . 5 3.3. Backward HbH Delay TLV . . . . . . . . . . . . . . . . . 7 3.4. HbH Packet Loss TLV . . . . . . . . . . . . . . . . . . . 9 3.5. HbH Bandwidth Utilization TLV . . . . . . . . . . . . . . 11 3.6. HbH Timestamp Information TLV . . . . . . . . . . . . . . 12 4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 14 5. Security Considerations . . . . . . . . . . . . . . . . . . . 14 6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 15 7. References . . . . . . . . . . . . . . . . . . . . . . . . . 15 7.1. Normative References . . . . . . . . . . . . . . . . . . 15 7.2. Informative References . . . . . . . . . . . . . . . . . 15 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 15 1. Introduction Simple Two-way Active Measurement Protocol (STAMP) [RFC8762] enables the measurement of both one-way and round-trip performance metrics, such as delay, delay variation, and packet loss. In the STAMP session, the bidirectional packet flow is transmitted between STAMP Session-Sender and STAMP Session-Reflector. The STAMP Session- Reflector receives test packets transmitted from Session-Sender and acts according to the configuration. However, the performance of intermediate nodes and links that STAMP test packets traverse are invisible. In addition, the STAMP instance must be configured at every intermediate node to measure the performance per node and link that test packets traverse, which increases the complexity of OAM in large-scale networks. Wang, et al. Expires May 19, 2021 [Page 2] Internet-Draft draft-wang-ippm-stamp-hbh-extensions-02 November 2020 STAMP Extensions have defined several optional TLVs to enhance the STAMP base functions. These optional TLVs are defined as updates of the STAMP Optional Extensions [I-D.ietf-ippm-stamp-option-tlv]. This document extents optional TLVs to STAMP, which enables performance measurement at every intermediate node and link along a STAMP test packet's delivery path, such as measurement of delay, delay variation, packet loss, and record of route information. The following sections describe the use of TLVs for STAMP that extend STAMP capability beyond its base specification. 2. Terminology Following are abbreviations used in this document: STAMP: Simple Two-way Active Measurement Protocol. IOAM: In-situ OAM. HbH: Hop-by-Hop. 3. TLV Extensions to STAMP 3.1. IOAM Tracing Data TLV STAMP Session-Sender MAY place the IOAM Tracing Data TLV in Session- Sender test packets to record the IOAM tracing data at every IOAM capable node along the Session-Sender test packet's forward-delivery path. As STAMP uses symmetrical packets, the Session-Sender MUST set the Length value as a multiple of 4 octets according to the number of nodes and the IOAM-Trace-Type (i.e. a 24-bit identifier which specifies which data types are used in the node data list [I-D.ietf-ippm-ioam-data]). And the node-data-copied-list fields MUST be set to zero upon Session-Sender test packets transmission and ignored upon receipt. The IOAM Tracing Data TLV has the following format: Wang, et al. Expires May 19, 2021 [Page 3] Internet-Draft draft-wang-ippm-stamp-hbh-extensions-02 November 2020 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-------------------------------+-------------------------------+ | IOAM-Tracing-Data Type | Length | +---------------------------------------------------------------+ | node data copied list [0] | +---------------------------------------------------------------+ | node data copied list [1] | +---------------------------------------------------------------+ ~ ... ~ +---------------------------------------------------------------+ | node data copied list [n] | +---------------------------------------------------------------+ Fig. 1 IOAM Tracing Data TLV Format where fields are defined as the following: o IOAM-Tracing-Data Type: To be assigned by IANA. o Length: A 2-octet field that indicates the length of the value field in octets and equal to a multiple of 4 octets dependent on the number of nodes and IOAM-Trace-Type bits. o node data copied list [0..n]: A variable-length field, which record the copied content of each node data element determined by the IOAM-Trace-Type. The order of packing the data fields in each node data element follows the bit order of the IOAM-Trace-Type field (see section 4.4.1 of [I-D.ietf-ippm-ioam-data]). The last node data element in this list is the node data of the first IOAM trace capable node in the path. In an IOAM domain, the STAMP Session-Sender and the STAMP Session- Reflector MAY be configured as the IOAM encapsulating node and the IOAM decapsulating node. The STAMP Session-Sender (i.e. the IOAM encapsulating node) generates the test packet with the IOAM Tracing Data TLV. For applying the IOAM Trace-Option functionalities to the Session-Sender test packet, the Session-Sender must inserts the "trace option header" and allocate an node-data-list array [I-D.ietf-ippm-ioam-data] into "option data" fields of Hop-by-Hop Options header in IPv6 packets [I-D.ietf-ippm-ioam-ipv6-options], and sets the corresponding bits in the IOAM-Trace-Type. Also, the STAMP Session-Sender allocates a node-data-copied-list array in the optional IOAM Tracing Data TLV to store OAM data retrieved from every IOAM transit node along the Session-Sender test packet's delivery path. Wang, et al. Expires May 19, 2021 [Page 4] Internet-Draft draft-wang-ippm-stamp-hbh-extensions-02 November 2020 When the STAMP Session-Reflector (i.e. the IOAM decapsulating node) received the STAMP Session-Sender test packet with the IOAM-Tracing- Data TLV, it MUST copy the node-data-list array into the node-data- copied-list array carried in the Session-Reflector test packet before transmission and MUST remove the IOAM-Data-Fields. Hence, carrying IOAM-Tracing-Data TLV in STAMP test packets enables OAM data collection and measurement at every node and link. Also the STAMP Session-Reflector MAY be configured as IOAM encapsulating node to apply the IOAM Trace-Option functionalities to the Session-Reflector test packet. Hence, OAM data collection and measurement can be also enabled at every node and link along the Session-Reflector test packet's backward delivery path. When the reflected packet arrives at the Session-Sender, it can be either locally processed or sent to the centralized controller. In addition to IOAM, other telemetry data (e.g. alternate marking) could be transmitted by STAMP optional TLV extensions. The draft will keep the option open for future augmentations. 3.2. Forward HbH Delay TLV STAMP Session-Sender MAY place the Forward HbH Delay TLV in Session- Sender test packets to record the ingress timestamp and the egress timestamp at every intermediate nodes along the Session-Sender test packet's forward path. The Session-Sender MUST set the Length value according to the number of explicitly listed intermediate nodes in the forward path and the timestamp formats. There are several methods to synchronize the clock, e.g., Network Time Protocol (NTP) [RFC5905] and IEEE 1588v2 Precision Time Protocol (PTP) [IEEE.1588.2008]. For example, if a 64-bit timestamp format defined in NTP is used, the Length value MUST be set as a multiple of 16 octets. The Timestamp Tuple list [1..n] fields MUST be set to zero upon Session-Sender test packets transmission. The Forward HbH Delay TLV has the following format: Wang, et al. Expires May 19, 2021 [Page 5] Internet-Draft draft-wang-ippm-stamp-hbh-extensions-02 November 2020 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-------------------------------+---------------+---------------+ | Forward HbH Delay Type | Length | Node Left | +-------------------------------+---------------+---------------+ | | | Timestamp Tuple list [1] | | | | | +---------------------------------------------------------------+ ~ ... ~ +---------------------------------------------------------------+ | | | Timestamp Tuple list [n] | | | | | +---------------------------------------------------------------+ Fig. 2 Forward HbH Delay TLV Format where fields are defined as the following: o Forward HbH Delay Type: To be assigned by IANA. o Length: A 8-bit field that indicates the length of the value portion in octets and MUST be a multiple of 16 octets according to the number of explicitly listed intermediate nodes in the forward path. o Node Left: A 8-bit unsigned integer, which indicates the number of intermediate nodes remaining. That is, number of explicitly listed intermediate nodes still to be visited before reaching the destination node in the forward path. The Node Left field is set to n-1, where n is the number of intermediate nodes. o Timestamp Tuple list [1..n]: A variable-length field, which record the timestamp when the Session-Sender test packet is received at the ingress of the n-th intermediate node Ingress Timestamp [n] and the timestamp when the Session-Sender test packet is sent at egress of the n-th intermediate node Egress Timestamp [n]. For example, if a 64-bit timestamp format defined in NTP is used, the length of each Timestamp tuple (Ingress Timestamp [n], Egress Timestamp [n]) must be 16 octets. The Timestamp Tuple list is encoded starting from the last intermediate node which is explicitly listed. That is, the first element of the Timestamp Tuple list [1] records the timestamps when the Session-Sender test packet received and forwarded at the last intermediate node of a explicit path, the second element records the penultimate Wang, et al. Expires May 19, 2021 [Page 6] Internet-Draft draft-wang-ippm-stamp-hbh-extensions-02 November 2020 Timestamp Tuple when the Session-Sender test packet received and forwarded at the penultimate intermediate node of a explicit path, and so on. In the following reference topology, Node N1, N2, N3, N4 and N5 are SRv6 capable nodes. Node N1 is the STAMP Session-Sender and Node N5 is the STAMP Session-Reflector. T1 is the Timestamp taken by the Session-Sender (i.e. N1) at the start of transmitting the test packet. T2 is the Receive Timestamp when the test packet was received by the Session-Reflector (i.e. N5). T3 is the Timestamp taken by the Session-Reflector at the start of transmitting the test packet. T4 is the Receive Timestamp when the test packet was received by the Session-Sender. Timestamp tuples (t1,t2), (t3,t4) and (t5,t6) are the timestamps when the test packet received and transmitted by sequence of intermediate nodes in the forward path. Timestamp Tuples (t7,t8), (t9,t10) and (t11,t12) are the timestamps when the test packet received and transmitted by sequence of intermediate nodes in the backward path. ====== ====== ====== ====== ====== | | T1--->t1 | | t2--->t3 | | t4--->t5 | | t6--->T2| | | N1 |==========| N2 |==========| N3 |==========| N4 |=========| N5 | | | T4<---t12| |t11<---t10| | t9<---t8 | | t7<---T3| | ====== ====== ====== ====== ====== Fig. 3 Reference Topology The STAMP Session-Sender (i.e. Node N1) generates the STAMP test packet with the Forward HbH Delay TLV. When an intermediate node receives the STAMP test packet, the node punts the packet to control plane and fills the Ingress Timestamp [n] filed in the Timestamp Tuple list [n]. Then the time taken by the intermediate node transmitting the test packet is recorded in to Egress Timestamp [n] field. The mechanism of timestamping and punting packet to control plane is outside the scope of this specification. When the STAMP Session-Reflector received the test packet with the Forward HbH Delay TLV, it MUST copy the Forward HbH Delay TLV into the Session-Reflector test packet before its transmission. Using Forward HbH Delay TLV in STAMP testing enables delay measurement per link in the forward path. 3.3. Backward HbH Delay TLV STAMP Session-Sender MAY place the Backward HbH Delay TLV in Session- Sender test packets to record the ingress timestamp and egress timestamp when Session-Reflector test packets are received and sent Wang, et al. Expires May 19, 2021 [Page 7] Internet-Draft draft-wang-ippm-stamp-hbh-extensions-02 November 2020 at every intermediate nodes in the backward path. The Session-Sender MUST set the Length value according to the number of explicitly listed intermediate nodes in the backward path and the timestamp formats. There are several methods to synchronize the clock, e.g., Network Time Protocol (NTP) [RFC5905] and IEEE 1588v2 Precision Time Protocol (PTP) [IEEE.1588.2008]. For example, if a 64-bit timestamp format defined in NTP is used, the Length value MUST be set as a multiple of 16 octets. The Timestamp Tuple list [1..n] fields MUST be set to zero upon Session-Sender test packets transmission and ignored upon receipt. The Backward HbH Delay TLV has the following format: 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-------------------------------+---------------+---------------+ | Backward HbH Delay Type | Length | Node Left | +-------------------------------+---------------+---------------+ | | | Timestamp Tuple list [1] | | | | | +---------------------------------------------------------------+ ~ ... ~ +---------------------------------------------------------------+ | | | Timestamp Tuple list [n] | | | | | +---------------------------------------------------------------+ Fig. 4 Backward HbH Delay TLV Format where fields are defined as the following: o Backward HbH Delay Type: To be assigned by IANA. o Length: A 8-bit field that indicates the length of the value portion in octets and will be a multiple of 16 octets dependent on the number of explicitly listed intermediate nodes in the backward path. o Node Left: A 8-bit unsigned integer, which indicates the number of intermediate nodes remaining. That is, number of explicitly listed intermediate nodes still to be visited before reaching the destination node in the backward path. The Node Left field is set to n-1, where n is the number of intermediate nodes. Wang, et al. Expires May 19, 2021 [Page 8] Internet-Draft draft-wang-ippm-stamp-hbh-extensions-02 November 2020 o Timestamp Tuple list [1..n]: A variable-length field, which record the timestamp when the reflected test packet is received at the ingress of the n-th intermediate node and the timestamp when the reflected test packet is sent at egress of the n-th intermediate node. For example, if a 64-bit timestamp format defined in NTP is used, the length of each Timestamp tuple (Ingress Timestamp [n], Egress Timestamp [n]) must be 16 octets. The Timestamp Tuple list is encoded starting from the last intermediate node which is explicitly listed. That is, the first element of the Timestamp Tuple list [1] records the timestamps when the reflected test packet received and forwarded at the last intermediate node of a explicit path, the second element records the penultimate Timestamp Tuple when the reflected test packet received and forwarded at the penultimate intermediate node of a explicit path, and so on. When the STAMP Session-Reflector received the Session-Sender test packet with the Backward HbH Delay TLV, it MUST copy the Backward HbH Delay TLV into the Session-Reflector test packet. When an intermediate node receives the reflected test packet, the node sends the packet to control plane and fills the Ingress Timestamp [n] filed of Backward HbH Delay TLV. Then the time taken by the intermediate node transmitting the test packet is recorded in to Egress Timestamp [n] field of Backward HbH Delay TLV. Using Backward HbH Delay TLV in STAMP testing enables delay measurement per link in the backward path. 3.4. HbH Packet Loss TLV STAMP Session-Sender MAY place the HbH Packet Loss TLV in Session- Sender test packets to record the number of Session-Sender test packets received at and transmitted by every intermediate nodes along the forward path. The Session-Sender MUST set the Length value according to the number of explicitly listed intermediate nodes in the forward path. A Counter Tuple is composed of a 64-bit Receive Counter field and a 64-bit Transmit Counter field. The Counter Tuple list [1..n] fields MUST be set to zero upon Session-Sender test packets transmission. The HbH Packet Loss TLV has the following format: Wang, et al. Expires May 19, 2021 [Page 9] Internet-Draft draft-wang-ippm-stamp-hbh-extensions-02 November 2020 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-------------------------------+---------------+---------------+ | HbH Packet Loss Type | Length | Node Left | +-------------------------------+---------------+---------------+ | | | Counter Tuple list [1] | | | | | +---------------------------------------------------------------+ ~ ... ~ +---------------------------------------------------------------+ | | | Counter Tuple list [n] | | | | | +---------------------------------------------------------------+ Fig. 5 HbH Packet Loss TLV Format where fields are defined as the following: o HbH Packet Loss Type: To be assigned by IANA. o Length: A 8-bit field that indicates the length of the value portion in octets and will be a multiple of 16 octets dependent on the number of explicitly listed intermediate nodes in the forward path. o Node Left: A 8-bit unsigned integer, which indicates the number of intermediate nodes remaining. That is, number of explicitly listed intermediate nodes still to be visited before reaching the destination node in the forward path. The Node Left field is set to n-1, where n is the number of intermediate nodes. o Counter Tuple list [1..n]: A variable-length field, which record the Receive Counter and the Transmit Counter when the test packet is received at and transmitted by the n-th intermediate node. The Counter Tuple list is encoded starting from the last intermediate node which is explicitly listed. That is, the first element of the Counter Tuple list [1] records the Receive Counter and the Transmit Counter when the test packet is received at and transmitted by the last intermediate node of a explicit path, the second element records the penultimate Counter Tuple when the test packet received and forwarded at the penultimate intermediate node of a explicit path, and so on. Wang, et al. Expires May 19, 2021 [Page 10] Internet-Draft draft-wang-ippm-stamp-hbh-extensions-02 November 2020 The STAMP Session-Sender generates the STAMP test packet with the HbH Packet Loss TLV. When an intermediate node receives the STAMP test packet, the node punts the packet to control plane and writes the Receive Counter and the Transmit Counter at the Counter Tuple list [n] in the Session-Sender test packet. The mechanism of punting packet to control plane is outside the scope of this specification. When the STAMP Session-Reflector received the test packet with the HbH Packet Loss TLV, it MUST copy the HbH Packet Loss TLV into the Session-Reflector test packet before its transmission. Using HbH Packet Loss TLV in STAMP testing enables packet loss measurement per node/link in the forward path. 3.5. HbH Bandwidth Utilization TLV STAMP Session-Sender MAY place the HbH Bandwidth Utilization TLV in Session-Sender test packets to record the ingress and egress bandwidth utilization at every intermediate nodes along the forward path. The Session-Sender MUST set the Length value according to the number of explicitly listed intermediate nodes in the forward path. A BW Utilization Tuple is composed of a 32-bit ingress bandwidth utilization field and a 32-bit egress bandwidth utilization field. The BW Utilization Tuple list [1..n] fields MUST be set to zero upon Session-Sender test packets transmission. The HbH Bandwidth Utilization TLV has the following format: 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-------------------------------+---------------+---------------+ | HbH BW Utilization Type | Length | Node Left | +-------------------------------+---------------+---------------+ | BW Utilization Tuple list [1] | | | +---------------------------------------------------------------+ ~ ... ~ +---------------------------------------------------------------+ | BW Utilization Tuple list [n] | | | +---------------------------------------------------------------+ Fig. 6 HbH Bandwidth Utilization TLV Format where fields are defined as the following: o HbH BW Utilization Type: To be assigned by IANA. Wang, et al. Expires May 19, 2021 [Page 11] Internet-Draft draft-wang-ippm-stamp-hbh-extensions-02 November 2020 o Length: A 8-bit field that indicates the length of the value portion in octets and will be a multiple of 8 octets dependent on the number of explicitly listed intermediate nodes in the forward path. o Node Left: A 8-bit unsigned integer, which indicates the number of intermediate nodes remaining. That is, number of explicitly listed intermediate nodes still to be visited before reaching the destination node in the forward path. The Node Left field is set to n-1, where n is the number of intermediate nodes. o BW Utilization Tuple list [1..n]: A variable-length field, which record the ingress and egress bandwidth utilization when the test packet is received at and transmitted by the n-th intermediate node. The BW Utilization Tuple list is encoded starting from the last intermediate node which is explicitly listed. That is, the first element of the BW Utilization Tuple list [1] records the ingress and the egress bandwidth utilization when the test packet is received at and transmitted by the last intermediate node of a explicit path, the second element records the penultimate BW Utilization Tuple when the test packet received at and transmitted by the penultimate intermediate node of a explicit path, and so on. The STAMP Session-Sender generates the STAMP test packet with the HbH BW Utilization TLV. When an intermediate node receives the STAMP test packet, the node punts the packet to control plane and writes the ingress and egress bandwidth utilization at the BW Utilization Tuple list [n] in the Session-Sender test packet. The mechanism of punting packet to control plane is outside the scope of this specification. When the STAMP Session-Reflector received the test packet with the HbH BW Utilization TLV, it MUST copy the HbH BW Utilization TLV into the Session-Reflector test packet before its transmission. The HbH BW Utilization TLV carried in STAMP test packet is usable to detect and troubleshoot the link congestion in the forward path. 3.6. HbH Timestamp Information TLV STAMP Session-Sender MAY place the HbH Timestamp Information TLV in Session-Sender test packets to query the ingress and egress Timestamp Information at every intermediate nodes along the forward path. The Timestamp Information includes the source of clock synchronization and the method of timestamp obtainment. There are several types of clock synchronization source, e.g., NTP, PTP. The method of timestamp obtainment may be from control plane (e.g. NTP) or from data plane (e.g. PTP). A Timestamp Info Tuple is composed of a Wang, et al. Expires May 19, 2021 [Page 12] Internet-Draft draft-wang-ippm-stamp-hbh-extensions-02 November 2020 8-bit ingress clock source field, a 8-bit ingress timestamp obtainment field, a 8-bit egress clock source field, and a 8-bit egress timestamp obtainment field. The Session-Sender MUST set the Length value according to the number of explicitly listed intermediate nodes in the forward path. The Timestamp Info Tuple list [1..n] fields MUST be set to zero upon Session-Sender test packets transmission. The HbH Timestamp Information TLV has the following format: 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-------------------------------+---------------+---------------+ | HbH Timestamp Info Type | Length | Node Left | +-------------------------------+---------------+---------------+ | Timestamp Info Tuple list [1] | +---------------------------------------------------------------+ ~ ... ~ +---------------------------------------------------------------+ | Timestamp Info Tuple list [n] | +---------------------------------------------------------------+ Fig. 6 HbH Timestamp Information TLV Format where fields are defined as the following: o HbH Timestamp Info Type: To be assigned by IANA. o Length: A 8-bit field that indicates the length of the value portion in octets and will be a multiple of 4 octets dependent on the number of explicitly listed intermediate nodes in the forward path. o Node Left: A 8-bit unsigned integer, which indicates the number of intermediate nodes remaining. That is, number of explicitly listed intermediate nodes still to be visited before reaching the destination node in the forward path. The Node Left field is set to n-1, where n is the number of intermediate nodes. o Timestamp Info Tuple list [1..n]: A variable-length field, which record the source of clock synchronization and the method of timestamp obtainment at the ingress and egress when the test packet is received at and transmitted by the n-th intermediate node. The Timestamp Info Tuple list is encoded starting from the last intermediate node which is explicitly listed. That is, the first element of the Timestamp Info Tuple list [1] records the source of clock synchronization and the method of timestamp Wang, et al. Expires May 19, 2021 [Page 13] Internet-Draft draft-wang-ippm-stamp-hbh-extensions-02 November 2020 obtainment at the ingress and egress when the test packet is received at and transmitted by the last intermediate node of a explicit path, the second element records the penultimate Timestamp Info Tuple when the test packet received at and transmitted by the penultimate intermediate node of a explicit path, and so on. The STAMP Session-Sender generates the STAMP test packet with the HbH Timestamp Information TLV. When an intermediate node receives the STAMP test packet, the node punts the packet to control plane and writes the source of clock synchronization and the method of timestamp obtainment at the Timestamp Info Tuple list [n] in the Session-Sender test packet. The mechanism of punting packet to control plane is outside the scope of this specification. When the STAMP Session-Reflector received the test packet with the HbH Timestamp Information TLV, it MUST copy the HbH Timestamp Information TLV into the Session-Reflector test packet before its transmission. The HbH Timestamp Information TLV carried in STAMP test packet is usable to query timestamp information from every nodes in the forward path. Note that the source of clock synchronization, NTP or PTP, is part of configuration of the Session-Sender/Reflector or a particular test session [RFC8762]. This draft recommends every intermediate nodes to be configured to use the same source of clock synchronization. 4. IANA Considerations IANA is requested to allocate values for the following TLV Type from the "STAMP TLV Type" registry [I-D.ietf-ippm-stamp-option-tlv]. +------------+-------------------------------+---------------+ | Code Point | Description | Reference | +------------+-------------------------------+---------------+ | TBA1 | IOAM Tracing Data TLV | This document | | TBA2 | Forward HbH Delay TLV | This document | | TBA3 | Backward HbH Delay TLV | This document | | TBA4 | HbH Packet Loss TLV | This document | | TBA5 | HbH BW Utilization TLV | This document | | TBA6 | HbH Timestamp Information TLV | This document | +------------+-------------------------------+---------------+ 5. Security Considerations This document extensions new optional TLVs to STAMP. It does not introduce any new security risks to STAMP. Wang, et al. Expires May 19, 2021 [Page 14] Internet-Draft draft-wang-ippm-stamp-hbh-extensions-02 November 2020 6. Acknowledgements The authors would like to thank Hongwei Yang, Giuseppe Fioccola and Chang Liu for the reviews and comments. 7. References 7.1. Normative References [I-D.ietf-ippm-ioam-data] "Data Fields for In-situ OAM", . [I-D.ietf-ippm-ioam-ipv6-options] "In-situ OAM IPv6 Options", . [I-D.ietf-ippm-stamp-option-tlv] "Simple Two-way Active Measurement Protocol Optional Extensions", . [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997, . [RFC8762] "Simple Two-Way Active Measurement Protocol", . 7.2. Informative References [IEEE.1588.2008] "IEEE Standard for a Precision Clock Synchronization Protocol for Networked Measurement and Control Systems", . [RFC5905] "Network Time Protocol Version 4: Protocol and Algorithms Specification", . Authors' Addresses Wang, et al. Expires May 19, 2021 [Page 15] Internet-Draft draft-wang-ippm-stamp-hbh-extensions-02 November 2020 Yali Wang Huawei 156 Beijing Rd., Haidian District Beijing China Email: wangyali11@huawei.com Tianran Zhou Huawei 156 Beijing Rd., Haidian District Beijing China Email: zhoutianran@huawei.com Hongwei Yang China Mobile Beijing China Email: yanghongwei@chinamobile.com Chang Liu China Unicom Beijing China Email: liuc131@chinaunicom.cn Wang, et al. Expires May 19, 2021 [Page 16]