| RFC 8762 | STAMP | March 2020 |
| Mirsky, et al. | Standards Track | [Page] |
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.¶
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.¶
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Development and deployment of the Two-Way Active Measurement Protocol (TWAMP)[RFC5357] and its extensions (e.g.,[RFC6038], which defines Symmetrical Size for TWAMP)provided invaluable experience. Several independent implementations of bothTWAMP and TWAMP Light exist, have been deployed, and provide important operational performance measurements.¶
At the same time, there has been noticeable interest in using a more straightforwardmechanism for active performance monitoring that can provide deterministicbehavior and inherent separation of control (vendor-specific configuration or orchestration) and test functions. Recent work on "Performance Measurement from IP Edge to Customer Equipment using TWAMP Light"[BBF.TR-390] by theBroadband Forum demonstrates that interoperability amongimplementations of TWAMP Light is difficult because the compositionand operation of TWAMP Light were not sufficiently specified in[RFC5357]. According to[RFC8545], TWAMP Light includes a subset of TWAMP-Testfunctions. Thus, to have a comprehensive tool to measure packet loss and delay requiressupport by other applications that provide, for example, control and security.¶
This document defines an active performance measurement test protocol, SimpleTwo-way Active Measurement Protocol (STAMP), that enables measurement of both one-way and round-trip performance metrics,like delay, delay variation, and packet loss. Support of some optional TWAMP extensions, e.g.,[RFC7750], is discussed in[STAMP-OPTION].¶
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in BCP 14[RFC2119][RFC8174] when, and only when, they appear in all capitals, as shown here.¶
Figure 1 presents the Simple Two-wayActive Measurement Protocol (STAMP) Session-Sender and Session-Reflector with a measurement session. In thisdocument, a measurement session, also referred to as a "STAMP session", is the bidirectionalpacket flow between one specific Session-Sender and one particularSession-Reflector for a time duration.The configuration and management of the STAMP Session-Sender,Session-Reflector, and sessions are outside the scope of thisdocument and can be achieved through various means. A few examples are Command Line Interface, telecommunicationservices' Operational Support System (OSS) / Business Support System (BSS),SNMP, and NETCONF/YANG-based Software-Defined Networking (SDN) controllers.¶
o----------------------------------------------------------o | Configuration and | | Management | o----------------------------------------------------------o || || || || || || +----------------------+ +-------------------------+ | STAMP Session-Sender | <--- STAMP---> | STAMP Session-Reflector | +----------------------+ +-------------------------+
The STAMP Session-Sender transmits test packets over UDP transporttoward the STAMP Session-Reflector. The STAMP Session-Reflectorreceives the Session-Sender's packet and acts according to the configuration. Two modes of the STAMP Session-Reflector characterize the expected behavior and, consequently, performance metrics that can be measured:¶
STAMP supports two authentication modes: unauthenticated and authenticated. Unauthenticated STAMP-Test packets, defined in Sections4.2.1 and4.3.1, ensure interworking between STAMP and TWAMP Light, as described inSection 4.6 regarding packet formats.¶
By default, STAMP uses symmetrical packets, i.e., the size of the packettransmitted by the Session-Reflector equals the size of the packet received by the Session-Reflector.¶
A STAMP Session-SenderMUST useUDP port 862 (TWAMP-Test Receiver Port) as the default destination UDP portnumber. A STAMP implementation of the Session-SenderMUSTbe able to be used as the destination UDP port numbers from the User Ports(aka Registered Ports) and Dynamic Ports (aka Private or Ephemeral Ports)ranges defined in[RFC6335]. Before usingnumbers from the User Ports range, the possible impact on the networkMUST be carefully studied and agreed on by all users of thenetwork domain where the test has been planned.¶
By default, an implementation of the STAMP Session-ReflectorMUST receive STAMP-Test packets on UDP port 862. Animplementation of the Session-Reflector that supports this specificationMUST be able to define theport number to receive STAMP-Test packets from User Ports and Dynamic Ports ranges, which are defined in[RFC6335]. 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.¶
A STAMP Session-Reflector supports the symmetrical size of test packets, as defined inSection 3 of [RFC6038], as the default behavior. A reflected base test packet includes information from the Session-Reflector and, thus, is larger. To maintain the symmetry between base STAMP packets, the base STAMP Session-Sender packet includes the Must-Be-Zero (MBZ) field to match to the size of a base reflected STAMP test packet. Hence, the base STAMP Session-Sender packet has a minimum size of 44 octets in unauthenticated mode (seeFigure 2) and 112 octets in the authenticated mode (seeFigure 4). Generating variable length of a test packet in STAMP is defined in[STAMP-OPTION].¶
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 | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + | | | | | MBZ (30 octets) | | | | | | | | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The fields are defined as following:¶
The Error Estimate field is two octets long with the format displayed inFigure 3:¶
0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |S|Z| Scale | Multiplier | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The S, Scale, and Multiplier fields are interpreted as they are defined inSection 4.1.2 of [RFC4656]. The Z field is interpreted as it is defined inSection 2.3 of [RFC8186]:¶
The default behavior of the STAMP Session-Sender andSession-Reflector is to use the NTP 64-bit timestamp format(Z field value of 0). An operator using configuration/management functionMAY configure the STAMP Session-Sender and Session-Reflectorto use the PTPv2 truncated format of a timestamp (Z field value of 1).Note that an implementation of a Session-Sender that supports this specificationMAY be configured to use the PTPv2 format of a timestamp eventhough the Session-Reflector is configured to use NTP 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Sequence Number | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | | MBZ (12 octets) | | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Timestamp | | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Error Estimate | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + ~ ~ | MBZ (70 octets) | ~ ~ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | | HMAC (16 octets) | | | | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The field definitions are the same as the unauthenticated mode, listed inSection 4.2.1. Also, MBZ fields are used to make the packet length a multiple of 16 octets. The value of the fieldMUST be zeroed on transmission andMUST be ignored on receipt. Note, that both MBZ fields are used to calculate a key hashed message authentication code (HMAC)[RFC2104] hash. Also, the packet includes an HMAC hash at the end of the PDU. The detailed use of the HMAC field is described inSection 4.4.¶
The Session-Reflector receives the STAMP-Test packet and verifies it. If the base STAMP-Test packet is validated, the Session-Reflector that supports this specification prepares and transmits the reflected test packet symmetric to the packet received from the Session-Sender copying the content beyond the size of the base STAMP packet (seeSection 4.2).¶
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 | MBZ | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Receive Timestamp | | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Session-Sender Sequence Number | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Session-Sender Timestamp | | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Session-Sender Error Estimate | MBZ | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |Ses-Sender TTL | MBZ | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Fields are defined as the following:¶
The Sequence Number field is four octets long. The value of the Sequence Number field is set according to the mode of the STAMP Session-Reflector:¶
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 | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + | MBZ (6 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) | | | | | | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The field definitions are the same as the unauthenticated mode, listed inSection 4.3.1. Additionally, the MBZ field is used to make the packet length a multiple of 16 octets. The value of the fieldMUST be zeroed on transmission andMUST be ignored on receipt. Note that the MBZ field is used to calculate the HMAC hash value. Also, the STAMP Session-Reflector test packet format in authenticated mode includes the HMAC[RFC2104] hash at the end of the PDU. The detailed use of the HMAC field is inSection 4.4.¶
Authenticated mode provides integrity protection to each STAMP message by adding Hashed Message Authentication Code (HMAC). STAMP uses HMAC-SHA-256 truncated to 128 bits (similarly to the use of it in IPsec defined in[RFC4868]); hence, the length of the HMAC field is 16 octets. In the authenticated mode, HMAC covers the first six blocks (96 octets). HMAC uses its own key, which may be unique for each STAMP-Test session; key management and the mechanisms to distribute the HMAC key are outside the scope of this specification. One example is to use an orchestrator to configure the HMAC key based on the STAMP YANG data model[STAMP-YANG]. HMACMUST be verified as early as possible to avoid using or propagating corrupted data.¶
Future specifications may define the use of other, more advanced cryptographic algorithms, possibly providing an update to the STAMP YANG data model[STAMP-YANG].¶
If confidentiality protection for STAMP is required, a STAMP-Test sessionMUST use a secured transport. For example, STAMP packets could be transmitted in the dedicated IPsec tunnel or share the IPsec tunnel with the monitored flow. Also, the Datagram Transport Layer Security protocol would provide the desired confidentiality protection.¶
One of the essential requirements to STAMP is the ability to interwork with aTWAMP Light device. Because STAMP and TWAMP use different algorithms inauthenticated mode (HMAC-SHA-256 versus HMAC-SHA-1), interoperability is onlyconsidered for unauthenticated mode. There are two possible combinations forsuch a use case:¶
In the former case, the Session-Sender might not be aware that its Session-Reflector does not support STAMP. For example, a TWAMP Light Session-Reflector may not support the use of UDP port 862, as specified in[RFC8545]. Thus,Section 4 permits a STAMP Session-Sender to use alternative ports. If any of STAMP extensions are used, the TWAMP Light Session-Reflector will view them as the Packet Padding field.¶
In the latter scenario, if a TWAMP Light Session-Sender does not support the use of UDP port 862, the test management systemMUST set the STAMP Session-Reflector to use UDP port number, as permitted bySection 4. The Session-ReflectorMUST be set to use the default format for its timestamps, NTP.¶
A STAMP Session-Reflector that supports this specification will transmit the base packet(Figure 5)if it receives a packet smaller than the STAMP base packet. If the packet received from the TWAMP Session-Sender islarger than the STAMP base packet, the STAMP Session-Reflector that supports this specification will copy thecontent of the remainder of the received packet to transmit a reflected packetof symmetrical size.¶
STAMP is intended to be used on production networks to enablethe operator to assess service level agreements based on packet delay,delay variation, and loss. When using STAMP over the Internet, especiallywhen STAMP-Test packets are transmitted with the destination UDP port number from the User Ports range, the possible impact of the STAMP-Test packetsMUST be thoroughly analyzed. The use of STAMP for each caseMUST be agreed by users of nodes hosting the Session-Sender and Session-Reflector before starting the STAMP-Test session.¶
Also, the use of the well-known port number as the destination UDP port number in STAMP-Test packets transmitted by a Session-Sender would not impede the ability to measure performance in an Equal-Cost Multipath environment, and analysis inSection 5.3 of [RFC8545] fully applies to STAMP.¶
This document has no IANA actions.¶
[RFC5357] does not identify security considerations specific to TWAMP-Test but refers to security considerations identified for OWAMP in[RFC4656]. Since both OWAMP and TWAMP include control-plane and data-plane components, only security considerations related to OWAMP-Test discussed in Sections6.2 and6.3 of[RFC4656] apply to STAMP.¶
STAMP uses the well-known UDP port number allocated for the OWAMP-Test/TWAMP-Test Receiver Port. Thus, the security considerations and measures to mitigate the risk of the attack using the registered port number documented inSection 6 of [RFC8545] equally apply to STAMP. Because of the control and management of a STAMP-Test being outside the scope of this specification, only the more general requirement is set:¶
Use of HMAC-SHA-256 in the authenticated mode protects the data integrityof the STAMP-Test packets.¶
The authors express their appreciation toJose Ignacio Alvarez-Hamelin andBrian Weis for their great insights into thesecurity and identity protection as well as the most helpful and practical suggestions. Also, our sincere thanks toDavid Ball,Rakesh Gandhi, andXiao Min fortheir thorough reviews and helpful comments.¶