Simple Two-way Active Measurement Protocol Extensions for Hop-by-Hop OAM Data Collection

STAMP Session-Sender can 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 ). 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:

where fields are defined as the following: IOAM-Tracing-Data Type: To be assigned by IANA. 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. 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 ). 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 into "option data" fields of Hop-by-Hop Options header in IPv6 packets , 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. 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.

STAMP Session-Sender can 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) and IEEE 1588v2 Precision Time Protocol (PTP) . 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:

where fields are defined as the following: Forward HbH Delay Type: To be assigned by IANA. 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. 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. 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 and the timestamp when the Session-Sender 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 Session-Sender test packet received and forwarded at the last intermediate node of a explicit path, the second element records the penultimate 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 | | t2--->t3 | | t4--->t5 | | t6--->T2| | | N1 |==========| N2 |==========| N3 |==========| N4 |=========| N5 | | | T4<---t12| |t11<---t10| | t9<---t8 | | t7<---T3| | ====== ====== ====== ====== ====== ]]> 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.

STAMP Session-Sender can 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 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) and IEEE 1588v2 Precision Time Protocol (PTP) . 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:

where fields are defined as the following: Backward HbH Delay Type: To be assigned by IANA. 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. 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. 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.

STAMP Session-Sender can place the HbH Direct 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 Direct Loss TLV has the following format:

where fields are defined as the following: HbH Direct Loss Type: To be assigned by IANA. 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. 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. 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. The STAMP Session-Sender generates the STAMP test packet with the HbH Direct Loss TLV. When an intermediate node receives the STAMP test packet, the node punts the packet to control plane and writes the Receive Counter [n] and the Transmit Counter [n] 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 Direct Loss TLV, it MUST copy the HbH Direct Loss TLV into the Session-Reflector test packet before its transmission. Using HbH Direct Loss TLV in STAMP testing enables packet loss measurement per node/link in the forward path.

STAMP Session-Sender can place the HbH Bandwidth Utilization (BW Utilization) TLV in Session-Sender test packets to record the ingress and egress BW 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 BW Utilization field and a 32-bit egress BW 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:

where fields are defined as the following: HbH BW Utilization Type: To be assigned by IANA. 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. 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. 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.

STAMP Session-Sender can place the HbH Timestamp Information TLV in Session-Sender test packets to record 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 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:

where fields are defined as the following: HbH Timestamp Info Type: To be assigned by IANA. 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. 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. 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 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 . This draft recommends every intermediate nodes to be configured to use the same source of clock synchronization.

STAMP Session-Sender can place the HbH Interface Errors TLV in Session-Sender test packets to record the errors detected on the interface of every intermediate node used to receive the packet along the forward path. The record of interface errors indicates the quality of the interfaces along the forward path and is helpful to analyze the performance degrades associated with the flow. A Interface Errors is a 32 bits unsigned integer field. This field records the Bit Error Rate (BER) or number of packet drop due to Cyclic Redundancy Check (CRC) errors. The Session-Sender MUST set the Length value according to the number of explicitly listed intermediate nodes in the forward path. The Interface Errors list [1..n] fields MUST be set to zero upon Session-Sender test packets transmission. The HbH Timestamp Information TLV has the following format:

where fields are defined as the following: HbH Interface Errors Type: To be assigned by IANA. 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. 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. Interface Errors list [1..n]: A variable-length field, which record the errors detected on the interface of the n-th intermediate node used to receive the packet along the forward path. The Interface Errors list is encoded starting from the last intermediate node which is explicitly listed. That is, the first element of the Interface Errors list [1] records the interface errors when the test packet is received at the last intermediate node of a explicit path, the second element records the penultimate interface errors when the test packet received at the penultimate intermediate node of a explicit path, and so on. The STAMP Session-Sender generates the STAMP test packet with the HbH Interface Errors TLV. When an intermediate node receives the STAMP test packet, the node punts the packet to control plane and writes the errors at the Interface Errors 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 Interface Errors TLV, it MUST copy the HbH Interface Errors TLV into the Session-Reflector test packet before its transmission. The HbH Interface Errors TLV carried in STAMP test packet is usable to detect interface errors from every intermediate nodes along the forward path.