RFC 8762 PROPOSED STANDARD MEASUREMENT · PERFORMANCE · OAM
STAMP: Simple Two-Way Active Measurement Protocol
A simple, interoperable way to send test packets between two endpoints and measure delay, delay variation and loss.
RFC EDITOR
Mirsky, G., Jun, G., Nydell, H., and R. Foote, "Simple Two-Way Active Measurement Protocol", RFC 8762, DOI 10.17487/RFC8762, March 2020, <https://www.rfc-editor.org/info/rfc8762>.
BIBTEX
@misc{rfc8762,
series = {Request for Comments},
number = 8762,
howpublished = {RFC 8762},
publisher = {RFC Editor},
doi = {10.17487/RFC8762},
url = {https://www.rfc-editor.org/info/rfc8762},
author = {G. Mirsky and G. Jun and H. Nydell and R. Foote},
title = {{Simple Two-Way Active Measurement Protocol}},
pagetotal = 15,
year = 2020,
month = mar,
} RFC text
Contents
Internet Engineering Task Force (IETF) G. Mirsky
Request for Comments: 8762 G. Jun
Category: Standards Track ZTE Corp.
ISSN: 2070-1721 H. Nydell
Accedian Networks
R. Foote
Nokia
March 2020
Simple Two-Way Active Measurement Protocol
Abstract
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.
Status of This Memo
This is an Internet Standards Track document.
This document is a product of the Internet Engineering Task Force
(IETF). It represents the consensus of the IETF community. It has
received public review and has been approved for publication by the
Internet Engineering Steering Group (IESG). Further information on
Internet Standards is available in Section 2 of RFC 7841.
Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
https://www.rfc-editor.org/info/rfc8762.
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. Conventions Used in This Document
2.1. Terminology
2.2. Requirements Language
3. Operation and Management of Performance Measurement Based on
STAMP
4. Theory of Operation
4.1. UDP Port Numbers in STAMP Testing
4.2. Session-Sender Behavior and Packet Format
4.2.1. Session-Sender Packet Format in Unauthenticated Mode
4.2.2. Session-Sender Packet Format in Authenticated Mode
4.3. Session-Reflector Behavior and Packet Format
4.3.1. Session-Reflector Packet Format in Unauthenticated Mode
4.3.2. Session-Reflector Packet Format in Authenticated Mode
4.4. Integrity Protection in STAMP
4.5. Confidentiality Protection in STAMP
4.6. Interoperability with TWAMP Light
5. Operational Considerations
6. IANA Considerations
7. Security Considerations
8. References
8.1. Normative References
8.2. Informative References
Acknowledgments
Authors' Addresses
1. Introduction
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 both TWAMP 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
straightforward mechanism for active performance monitoring that can
provide deterministic behavior 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 the Broadband Forum
demonstrates that interoperability among implementations of TWAMP
Light is difficult because the composition and operation of TWAMP
Light were not sufficiently specified in [RFC5357]. According to
[RFC8545], TWAMP Light includes a subset of TWAMP-Test functions.
Thus, to have a comprehensive tool to measure packet loss and delay
requires support by other applications that provide, for example,
control and security.
This document defines an active performance measurement test
protocol, Simple Two-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].
2. Conventions Used in This Document
2.1. Terminology
STAMP: Simple Two-way Active Measurement Protocol
NTP: Network Time Protocol
PTP: Precision Time Protocol
HMAC: Hashed Message Authentication Code
OWAMP: One-Way Active Measurement Protocol
TWAMP: Two-Way Active Measurement Protocol
MBZ: Must be Zero
PDU: Protocol Data Unit
2.2. Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in
BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here.
3. Operation and Management of Performance Measurement Based on STAMP
Figure 1 presents the Simple Two-way Active Measurement Protocol
(STAMP) Session-Sender and Session-Reflector with a measurement
session. In this document, a measurement session, also referred to
as a "STAMP session", is the bidirectional packet flow between one
specific Session-Sender and one particular Session-Reflector for a
time duration. The configuration and management of the STAMP
Session-Sender, Session-Reflector, and sessions are outside the scope
of this document and can be achieved through various means. A few
examples are Command Line Interface, telecommunication services'
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 |
+----------------------+ +-------------------------+
Figure 1: STAMP Reference Model
4. Theory of Operation
The STAMP Session-Sender transmits test packets over UDP transport
toward the STAMP Session-Reflector. The STAMP Session-Reflector
receives 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:
Stateless:
The STAMP Session-Reflector does not maintain test state and will
use the value in the Sequence Number field in the received packet
as the value for the Sequence Number field in the reflected
packet. As a result, values in the Sequence Number and Session-
Sender Sequence Number fields are the same, and only round-trip
packet loss can be calculated while the reflector is operating in
stateless mode.
Stateful:
STAMP Session-Reflector maintains the test state, thus allowing
the Session-Sender to determine directionality of loss using the
combination of gaps recognized in the Session Sender Sequence
Number and Sequence Number fields, respectively. As a result,
both near-end (forward) and far-end (backward) packet loss can be
computed. That implies that the STAMP Session-Reflector MUST
maintain a state for each configured STAMP-Test session, thereby
uniquely associating STAMP-Test packets with one such session
instance and, thus, enabling the addition of a sequence number in
the test reply that is individually incremented by one on a per-
session basis.
STAMP supports two authentication modes: unauthenticated and
authenticated. Unauthenticated STAMP-Test packets, defined in
Sections 4.2.1 and 4.3.1, ensure interworking between STAMP and TWAMP
Light, as described in Section 4.6 regarding packet formats.
By default, STAMP uses symmetrical packets, i.e., the size of the
packet transmitted by the Session-Reflector equals the size of the
packet received by the Session-Reflector.
4.1. UDP Port Numbers in STAMP Testing
A STAMP Session-Sender MUST use UDP port 862 (TWAMP-Test Receiver
Port) as the default destination UDP port number. A STAMP
implementation of the Session-Sender MUST be 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 using numbers from the User Ports
range, the possible impact on the network MUST be carefully studied
and agreed on by all users of the network domain where the test has
been planned.
By default, an implementation of the STAMP Session-Reflector MUST
receive STAMP-Test packets on UDP port 862. An implementation of the
Session-Reflector that supports this specification MUST be able to
define the port 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.
4.2. Session-Sender Behavior and Packet Format
A STAMP Session-Reflector supports the symmetrical size of test
packets, as defined in Section 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 (see
Figure 2) and 112 octets in the authenticated mode (see Figure 4).
Generating variable length of a test packet in STAMP is defined in
[STAMP-OPTION].
4.2.1. Session-Sender Packet Format in Unauthenticated Mode
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sequence Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Timestamp |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Error Estimate | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
| |
| |
| MBZ (30 octets) |
| |
| |
| |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 2: STAMP Session-Sender Test Packet Format in
Unauthenticated Mode
The fields are defined as following:
* The Sequence Number field is four octets long. For each new
session, its value starts at zero and is incremented by one with
each transmitted packet.
* The Timestamp field is eight octets long. The STAMP node MUST
support the Network Time Protocol (NTP) version 4 64-bit timestamp
format [RFC5905], the format used in [RFC5357]. The STAMP node
MAY support the IEEE 1588v2 Precision Time Protocol (PTP)
truncated 64-bit timestamp format [IEEE.1588.2008], the format
used in [RFC8186]. The use of the specific format, NTP or PTP, is
part of configuration of the Session-Sender or the particular test
session.
* The Error Estimate field is two octets long with the format
displayed in Figure 3:
0 1
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|S|Z| Scale | Multiplier |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 3: Error Estimate Format
The S, Scale, and Multiplier fields are interpreted as they are
defined in Section 4.1.2 of [RFC4656]. The Z field is interpreted
as it is defined in Section 2.3 of [RFC8186]:
0: NTP 64-bit format of a timestamp
1: PTPv2 truncated format of a timestamp
The default behavior of the STAMP Session-Sender and Session-
Reflector is to use the NTP 64-bit timestamp format (Z field value
of 0). An operator using configuration/management function MAY
configure the STAMP Session-Sender and Session-Reflector to use
the PTPv2 truncated format of a timestamp (Z field value of 1).
Note that an implementation of a Session-Sender that supports this
specification MAY be configured to use the PTPv2 format of a
timestamp even though the Session-Reflector is configured to use
NTP format.
* The MBZ field in the Session-Sender unauthenticated packet is 30
octets long. It MUST be all zeroed on the transmission and MUST
be ignored on receipt.
4.2.2. Session-Sender Packet Format in Authenticated Mode
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sequence Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| MBZ (12 octets) |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Timestamp |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Error Estimate | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
~ ~
| MBZ (70 octets) |
~ ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| HMAC (16 octets) |
| |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 4: STAMP Session-Sender Test Packet Format in
Authenticated Mode
The field definitions are the same as the unauthenticated mode,
listed in Section 4.2.1. Also, MBZ fields are used to make the
packet length a multiple of 16 octets. The value of the field MUST
be zeroed on transmission and MUST 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 in Section 4.4.
4.3. Session-Reflector Behavior and Packet Format
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 (see
Section 4.2).
4.3.1. Session-Reflector Packet Format in Unauthenticated Mode
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sequence Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Timestamp |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Error Estimate | MBZ |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Receive Timestamp |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Session-Sender Sequence Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Session-Sender Timestamp |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Session-Sender Error Estimate | MBZ |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Ses-Sender TTL | MBZ |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 5: STAMP Session-Reflector Test Packet Format in
Unauthenticated Mode
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:
- In the stateless mode, the Session-Reflector copies the value
from the received STAMP-Test packet's Sequence Number field.
- In the stateful mode, the Session-Reflector counts the
transmitted STAMP-Test packets. It starts with zero and is
incremented by one for each subsequent packet for each test
session. The Session-Reflector uses that counter to set the
value of the Sequence Number field.
* The Timestamp and Receive Timestamp fields are each eight octets
long. The format of these fields, NTP or PTPv2, is indicated by
the Z field of the Error Estimate field, as described in
Section 4.2.1. Receive Timestamp is the time the test packet was
received by the Session-Reflector. Timestamp is the time taken by
the Session-Reflector at the start of transmitting the test
packet.
* The Error Estimate field has the same size and interpretation as
described in Section 4.2.1. It is applicable to both Timestamp
and Receive Timestamp.
* The Session-Sender Sequence Number, Session-Sender Timestamp, and
Session-Sender Error Estimate fields are copies of the
corresponding fields in the STAMP-Test packet sent by the Session-
Sender.
* The Session-Sender TTL field is one octet long, and its value is
the copy of the TTL field in IPv4 (or Hop Limit in IPv6) from the
received STAMP-Test packet.
* The MBZ fields are used to achieve alignment of fields within the
packet on a four-octet boundary. The value of each MBZ field MUST
be zeroed on transmission and MUST be ignored on receipt.
4.3.2. Session-Reflector Packet Format in Authenticated Mode
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sequence Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| MBZ (12 octets) |
| |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Timestamp |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Error Estimate | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
| 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) |
| |
| |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 6: STAMP Session-Reflector Test Packet Format in
Authenticated Mode
The field definitions are the same as the unauthenticated mode,
listed in Section 4.3.1. Additionally, the MBZ field is used to make
the packet length a multiple of 16 octets. The value of the field
MUST be zeroed on transmission and MUST 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 in Section 4.4.
4.4. Integrity Protection in STAMP
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]. HMAC MUST 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].
4.5. Confidentiality Protection in STAMP
If confidentiality protection for STAMP is required, a STAMP-Test
session MUST 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.
4.6. Interoperability with TWAMP Light
One of the essential requirements to STAMP is the ability to
interwork with a TWAMP Light device. Because STAMP and TWAMP use
different algorithms in authenticated mode (HMAC-SHA-256 versus HMAC-
SHA-1), interoperability is only considered for unauthenticated mode.
There are two possible combinations for such a use case:
* STAMP Session-Sender with TWAMP Light Session-Reflector
* TWAMP Light Session-Sender with STAMP Session-Reflector
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 system MUST set
the STAMP Session-Reflector to use UDP port number, as permitted by
Section 4. The Session-Reflector MUST 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 is larger than the STAMP base packet, the STAMP
Session-Reflector that supports this specification will copy the
content of the remainder of the received packet to transmit a
reflected packet of symmetrical size.
5. Operational Considerations
STAMP is intended to be used on production networks to enable the
operator to assess service level agreements based on packet delay,
delay variation, and loss. When using STAMP over the Internet,
especially when STAMP-Test packets are transmitted with the
destination UDP port number from the User Ports range, the possible
impact of the STAMP-Test packets MUST be thoroughly analyzed. The
use of STAMP for each case MUST 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 in Section 5.3 of [RFC8545] fully
applies to STAMP.
6. IANA Considerations
This document has no IANA actions.
7. Security Considerations
[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 Sections 6.2 and 6.3 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 in Section 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:
To mitigate the possible attack vector, the control and management
of a STAMP-Test session MUST use the secured transport.
The load of the STAMP-Test packets offered to a network MUST be
carefully estimated, and the possible impact on the existing
services MUST be thoroughly analyzed before launching the test
session. Section 3.1.5 of [RFC8085] provides guidance on handling
network load for UDP-based protocol. While the characteristic of
test traffic depends on the test objective, it is highly
recommended to stay in the limits, as provided in [RFC8085].
Use of HMAC-SHA-256 in the authenticated mode protects the data
integrity of the STAMP-Test packets.
8. References
8.1. Normative References
[IEEE.1588.2008]
IEEE, "IEEE Standard for a Precision Clock Synchronization
Protocol for Networked Measurement and Control Systems",
IEEE Standard 1588, July 2008.
[RFC2104] Krawczyk, H., Bellare, M., and R. Canetti, "HMAC: Keyed-
Hashing for Message Authentication", RFC 2104,
DOI 10.17487/RFC2104, February 1997,
<https://www.rfc-editor.org/info/rfc2104>.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.
[RFC4656] Shalunov, S., Teitelbaum, B., Karp, A., Boote, J., and M.
Zekauskas, "A One-way Active Measurement Protocol
(OWAMP)", RFC 4656, DOI 10.17487/RFC4656, September 2006,
<https://www.rfc-editor.org/info/rfc4656>.
[RFC5357] Hedayat, K., Krzanowski, R., Morton, A., Yum, K., and J.
Babiarz, "A Two-Way Active Measurement Protocol (TWAMP)",
RFC 5357, DOI 10.17487/RFC5357, October 2008,
<https://www.rfc-editor.org/info/rfc5357>.
[RFC5905] Mills, D., Martin, J., Ed., Burbank, J., and W. Kasch,
"Network Time Protocol Version 4: Protocol and Algorithms
Specification", RFC 5905, DOI 10.17487/RFC5905, June 2010,
<https://www.rfc-editor.org/info/rfc5905>.
[RFC6038] Morton, A. and L. Ciavattone, "Two-Way Active Measurement
Protocol (TWAMP) Reflect Octets and Symmetrical Size
Features", RFC 6038, DOI 10.17487/RFC6038, October 2010,
<https://www.rfc-editor.org/info/rfc6038>.
[RFC6335] Cotton, M., Eggert, L., Touch, J., Westerlund, M., and S.
Cheshire, "Internet Assigned Numbers Authority (IANA)
Procedures for the Management of the Service Name and
Transport Protocol Port Number Registry", BCP 165,
RFC 6335, DOI 10.17487/RFC6335, August 2011,
<https://www.rfc-editor.org/info/rfc6335>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>.
[RFC8186] Mirsky, G. and I. Meilik, "Support of the IEEE 1588
Timestamp Format in a Two-Way Active Measurement Protocol
(TWAMP)", RFC 8186, DOI 10.17487/RFC8186, June 2017,
<https://www.rfc-editor.org/info/rfc8186>.
[RFC8545] Morton, A., Ed. and G. Mirsky, Ed., "Well-Known Port
Assignments for the One-Way Active Measurement Protocol
(OWAMP) and the Two-Way Active Measurement Protocol
(TWAMP)", RFC 8545, DOI 10.17487/RFC8545, March 2019,
<https://www.rfc-editor.org/info/rfc8545>.
8.2. Informative References
[BBF.TR-390]
Broadband Forum, "Performance Measurement from IP Edge to
Customer Equipment using TWAMP Light", TR-390 Issue 1, May
2017.
[RFC4868] Kelly, S. and S. Frankel, "Using HMAC-SHA-256, HMAC-SHA-
384, and HMAC-SHA-512 with IPsec", RFC 4868,
DOI 10.17487/RFC4868, May 2007,
<https://www.rfc-editor.org/info/rfc4868>.
[RFC7750] Hedin, J., Mirsky, G., and S. Baillargeon, "Differentiated
Service Code Point and Explicit Congestion Notification
Monitoring in the Two-Way Active Measurement Protocol
(TWAMP)", RFC 7750, DOI 10.17487/RFC7750, February 2016,
<https://www.rfc-editor.org/info/rfc7750>.
[RFC8085] Eggert, L., Fairhurst, G., and G. Shepherd, "UDP Usage
Guidelines", BCP 145, RFC 8085, DOI 10.17487/RFC8085,
March 2017, <https://www.rfc-editor.org/info/rfc8085>.
[STAMP-OPTION]
Mirsky, G., Xiao, M., Nydell, H., Foote, R., Masputra, A.,
and E. Ruffini, "Simple Two-way Active Measurement
Protocol Optional Extensions", Work in Progress, Internet-
Draft, draft-ietf-ippm-stamp-option-tlv-03, 21 February
2020, <https://tools.ietf.org/html/draft-ietf-ippm-stamp-
option-tlv-03>.
[STAMP-YANG]
Mirsky, G., Xiao, M., and W. Luo, "Simple Two-way Active
Measurement Protocol (STAMP) Data Model", Work in
Progress, Internet-Draft, draft-ietf-ippm-stamp-yang-05,
25 October 2019, <https://tools.ietf.org/html/draft-ietf-
ippm-stamp-yang-05>.
Acknowledgments
The authors express their appreciation to Jose Ignacio Alvarez-
Hamelin and Brian Weis for their great insights into the security and
identity protection as well as the most helpful and practical
suggestions. Also, our sincere thanks to David Ball, Rakesh Gandhi,
and Xiao Min for their thorough reviews and helpful comments.
Authors' Addresses
Greg Mirsky
ZTE Corp.
Email: gregimirsky@gmail.com
Guo Jun
ZTE Corp.
68# Zijinghua Road
Nanjing
Jiangsu, 210012
China
Phone: +86 18105183663
Email: guo.jun2@zte.com.cn
Henrik Nydell
Accedian Networks
Email: hnydell@accedian.com
Richard Foote
Nokia
Email: footer.foote@nokia.com
AI ELI5
On this page
PROBLEMTWAMP Light implementations were hard to make interoperate because RFC 5357 did not specify them well enough, and operators wanted a simpler test protocol with test and control kept separate.
MECHANISMA Session-Sender sends UDP test packets with a sequence number and timestamp to a Session-Reflector, which sends back a reply carrying its own receive and transmit timestamps. The packets can be unauthenticated or protected with an HMAC.
WHY IT MATTERSSTAMP measures one-way and round-trip delay, delay variation and packet loss, and unauthenticated mode interworks with TWAMP Light. It is a Proposed Standard that has since been updated by RFC 8972.
§1Why STAMP Exists
The Two-Way Active Measurement Protocol (TWAMP, RFC 5357) and its extensions gave operators useful experience, and several independent implementations of TWAMP and TWAMP Light have been deployed. At the same time there was interest in a more straightforward mechanism that behaves deterministically and keeps the test function separate from control, which is vendor-specific configuration or orchestration.
The RFC points out that work by the Broadband Forum showed interoperability among TWAMP Light implementations is difficult, because RFC 5357 did not specify TWAMP Light sufficiently. STAMP, the Simple Two-way Active Measurement Protocol, is the answer: an active test protocol that measures both one-way and round-trip performance metrics, such as delay, delay variation and packet loss.
Different companies built their own versions of a network speed-test and they did not always work together. STAMP is a simpler, clearer version everyone can follow.
§4Sender, Reflector and Sessions
A STAMP session is the two-way packet flow between one Session-Sender and one Session-Reflector for some period of time. How sessions and endpoints are configured and managed is out of scope; the RFC lists a command line interface, OSS/BSS systems, SNMP and NETCONF/YANG controllers as examples.
The Session-Sender sends test packets over UDP to the Session-Reflector. The sender MUST use UDP port 862 as the default destination port, and it must also be able to use ports from the User Ports and Dynamic Ports ranges. The reflector MUST listen on port 862 by default and be able to use other ports from those ranges. By default the packets are symmetrical: the reply is the same size as the request.
The reflector works in one of two modes. In stateless mode it keeps no test state and copies the received sequence number, so only round-trip loss can be calculated. In stateful mode it keeps state for each session and numbers its replies itself, which lets the sender tell forward loss from backward loss.
One kid throws numbered balls and another throws them back. If the thrower keeps a tally, they can tell whether the balls got lost on the way there or on the way back.
Session-SenderSession-Reflector
- Test packetUDP, default destination port 862; carries sequence number and timestamp.
- Reflected packetAdds receive timestamp and its own timestamp; copies the sender's fields.
| Mode | Reflector keeps state? | Sequence Number in reply | Loss that can be computed |
|---|---|---|---|
| Stateless | No | Copied from the received packet | Round-trip only |
| Stateful | Yes, per session | Reflector's own counter, plus one each packet | Near-end (forward) and far-end (backward) |
§4.2The Session-Sender Test Packet
The base sender packet is 44 octets in unauthenticated mode and 112 octets in authenticated mode. It carries a 4-octet Sequence Number that starts at zero for each new session and goes up by one per packet, an 8-octet Timestamp, and a 2-octet Error Estimate. The rest is Must-Be-Zero (MBZ) padding, which makes the sender packet match the size of the larger reflected packet.
Nodes MUST support the NTP version 4 64-bit timestamp format and MAY support the IEEE 1588v2 PTP truncated 64-bit format. The Z bit in the Error Estimate says which one is in use: 0 for NTP, 1 for PTPv2. NTP is the default. MBZ fields MUST be zero when sent and ignored on receipt.
In authenticated mode the packet is padded with MBZ fields to a multiple of 16 octets and ends with a 16-octet HMAC.
Each test packet is a numbered postcard with the exact time written on it, plus some blank space so the reply can be the same size.
| Field | Name | Size | Value | Description |
|---|---|---|---|---|
SEQ | Sequence Number | 4 bytes | Starts at zero for a new session, plus one per packet. | |
TIMESTAMP | Timestamp | 8 bytes | NTP 64-bit format by default; PTP truncated format optional. | |
ERR | Error Estimate | 2 bytes | S, Z, Scale and Multiplier; Z says NTP (0) or PTPv2 (1). | |
MBZ | MBZ | 30 bytes | 30 octets, zero on send and ignored on receipt. |
§4.3The Session-Reflector Reply
If the reflector validates the base test packet, it sends back a reply of symmetrical size, copying any content beyond the base packet. The reply carries its own Sequence Number, Timestamp (taken at the start of transmitting) and Receive Timestamp (when the test packet arrived), plus copies of the sender's sequence number, timestamp and error estimate.
It also includes a 1-octet Session-Sender TTL field, which is a copy of the TTL (IPv4) or Hop Limit (IPv6) of the received packet. The other bytes are MBZ fields that keep fields aligned on four-octet boundaries. As with the sender, authenticated mode adds more MBZ padding and a 16-octet HMAC at the end.
The friend writes back on the same postcard: when it arrived, when it was sent back, and a copy of what you wrote, so you can do the math.
| Field | Name | Size | Value | Description |
|---|---|---|---|---|
SEQ | Sequence Number | 4 bytes | Copied from the sender (stateless) or counted by the reflector (stateful). | |
TIMESTAMP | Timestamp | 8 bytes | Taken by the reflector at the start of transmitting. | |
ERR | Error Estimate | 2 bytes | Same size and meaning as in the sender packet. | |
MBZ1 | MBZ | 2 bytes | Zero on send, ignored on receipt. | |
RX-TS | Receive Timestamp | 8 bytes | When the test packet arrived at the reflector. | |
SS-SEQ | Session-Sender Sequence Number | 4 bytes | Copy of the sender's sequence number. | |
SS-TS | Session-Sender Timestamp | 8 bytes | Copy of the sender's timestamp. | |
SS-ERR | Session-Sender Error Estimate | 2 bytes | Copy of the sender's error estimate. | |
MBZ2 | MBZ | 2 bytes | Zero on send, ignored on receipt. | |
TTL | Session-Sender TTL | 1 byte | Copy of the TTL or Hop Limit of the received packet. | |
MBZ3 | MBZ | 3 bytes | Zero on send, ignored on receipt. |
§4.4Integrity and Confidentiality
Authenticated mode protects each STAMP message with an HMAC. STAMP uses HMAC-SHA-256 truncated to 128 bits, so the HMAC field is 16 octets. It covers the first six blocks (96 octets) of the packet, and it MUST be verified as early as possible so corrupted data is not used or passed on.
The HMAC uses its own key, which may differ for each test session. Key management and key distribution are outside the scope of the RFC; it suggests an orchestrator configuring the key through the STAMP YANG data model as one example. Future specifications may define stronger algorithms.
STAMP itself does not encrypt anything. If confidentiality is required, a session MUST use a secured transport, for example an IPsec tunnel or Datagram Transport Layer Security.
A secret stamp on each postcard shows nobody changed it on the way. If you want nobody to read it, you put it in a locked box.
§4.6Working With TWAMP Light
Interworking with TWAMP Light devices was an essential requirement. Because STAMP uses HMAC-SHA-256 in authenticated mode while TWAMP uses HMAC-SHA-1, interoperability is considered only for unauthenticated mode. Two combinations are possible: a STAMP sender with a TWAMP Light reflector, and a TWAMP Light sender with a STAMP reflector.
A TWAMP Light reflector may not support port 862, so a STAMP sender may use another port. Any STAMP extensions are seen by TWAMP Light as the Packet Padding field. When the sender is TWAMP Light and cannot use port 862, the test management system MUST set the STAMP reflector to another permitted port and to the default NTP timestamp format.
A STAMP reflector answers a packet smaller than the base packet with the base reply, and answers a larger one by copying the extra content to keep the sizes symmetrical.
STAMP can play catch with the older game's players, as long as nobody uses the secret stamp, since the two games stamp differently.
§7Operational and Security Considerations
STAMP is meant for production networks, so operators can assess service level agreements based on delay, delay variation and loss. The load of test packets MUST be carefully estimated and its impact on existing services thoroughly analyzed. When using the Internet, especially with User Ports, the use MUST be agreed by the users of the nodes hosting the sender and reflector before a session starts. Guidance on UDP load comes from RFC 8085.
Security considerations come from OWAMP-Test (RFC 4656) and from the use of the well-known port, covered in RFC 8545. Because configuration and management are out of scope, the RFC sets one general rule: control and management of a STAMP session MUST use secured transport. HMAC-SHA-256 in authenticated mode protects the integrity of test packets. The document has no IANA actions.
Test packets use up some of the road, so you have to ask the road's owners first and not send too many.
§8References
[RFC5357]RFC 5357Hedayat, K., Krzanowski, R., Morton, A., Yum, K., and J. Babiarz, "A Two-Way Active Measurement Protocol (TWAMP)", RFC 5357, October 2008.October 2008[RFC4656]RFC 4656Shalunov, S., Teitelbaum, B., Karp, A., Boote, J., and M. Zekauskas, "A One-way Active Measurement Protocol (OWAMP)", RFC 4656, September 2006.September 2006[RFC8545]RFC 8545Morton, A., Ed. and G. Mirsky, Ed., "Well-Known Port Assignments for the One-Way Active Measurement Protocol (OWAMP) and the Two-Way Active Measurement Protocol (TWAMP)", RFC 8545, March 2019.March 2019[RFC6038]RFC 6038Morton, A. and L. Ciavattone, "Two-Way Active Measurement Protocol (TWAMP) Reflect Octets and Symmetrical Size Features", RFC 6038, October 2010.October 2010[RFC8186]RFC 8186Mirsky, G. and I. Meilik, "Support of the IEEE 1588 Timestamp Format in a Two-Way Active Measurement Protocol (TWAMP)", RFC 8186, June 2017.June 2017[RFC2104]RFC 2104Krawczyk, H., Bellare, M., and R. Canetti, "HMAC: Keyed-Hashing for Message Authentication", RFC 2104, February 1997.February 1997[RFC8085]RFC 8085Eggert, L., Fairhurst, G., and G. Shepherd, "UDP Usage Guidelines", BCP 145, RFC 8085, March 2017.March 2017