STAMP Extensions: Simple Two-Way Active Measurement Protocol Optional Extensions
Optional add-on fields that let STAMP test packets carry location, timing, class-of-service and integrity data.
Mirsky, G., Min, X., Nydell, H., Foote, R., Masputra, A., and E. Ruffini, "Simple Two-Way Active Measurement Protocol Optional Extensions", RFC 8972, DOI 10.17487/RFC8972, January 2021, <https://www.rfc-editor.org/info/rfc8972>.
@misc{rfc8972,
series = {Request for Comments},
number = 8972,
howpublished = {RFC 8972},
publisher = {RFC Editor},
doi = {10.17487/RFC8972},
url = {https://www.rfc-editor.org/info/rfc8972},
author = {G. Mirsky and X. Min and H. Nydell and R. Foote and A. Masputra and E. Ruffini},
title = {{Simple Two-Way Active Measurement Protocol Optional Extensions}},
pagetotal = 29,
year = 2021,
month = jan,
} RFC text
Contents
Internet Engineering Task Force (IETF) G. Mirsky
Request for Comments: 8972 X. Min
Updates: 8762 ZTE Corp.
Category: Standards Track H. Nydell
ISSN: 2070-1721 Accedian Networks
R. Foote
Nokia
A. Masputra
Apple Inc.
E. Ruffini
OutSys
January 2021
Simple Two-Way Active Measurement Protocol Optional Extensions
Abstract
This document describes optional extensions to Simple Two-way Active
Measurement Protocol (STAMP) that enable measurement of performance
metrics. The document also defines a STAMP Test Session Identifier
and thus updates RFC 8762.
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/rfc8972.
Copyright Notice
Copyright (c) 2021 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. Acronyms
2.2. Requirements Language
3. STAMP Test Session Identifier
4. TLV Extensions to STAMP
4.1. Extra Padding TLV
4.2. Location TLV
4.2.1. Location Sub-TLVs
4.2.2. Theory of Operation of Location TLV
4.3. Timestamp Information TLV
4.4. Class of Service TLV
4.5. Direct Measurement TLV
4.6. Access Report TLV
4.7. Follow-Up Telemetry TLV
4.8. HMAC TLV
5. IANA Considerations
5.1. STAMP TLV Types Subregistry
5.2. STAMP TLV Flags Subregistry
5.3. STAMP Sub-TLV Types Subregistry
5.4. STAMP Synchronization Sources Subregistry
5.5. STAMP Timestamping Methods Subregistry
5.6. STAMP Return Codes Subregistry
6. Security Considerations
7. References
7.1. Normative References
7.2. Informative References
Acknowledgments
Contributors
Authors' Addresses
1. Introduction
The Simple Two-way Active Measurement Protocol (STAMP) [RFC8762]
defines the STAMP base functionalities. This document specifies the
use of optional extensions that use Type-Length-Value (TLV) encoding.
Such extensions enhance the STAMP base functions, such as measurement
of one-way and round-trip delay, latency, packet loss, packet
duplication, and out-of-order delivery of test packets. This
specification defines optional STAMP extensions, their formats, and
the theory of operation. Also, a STAMP Test Session Identifier is
defined as an update of the base STAMP specification [RFC8762].
2. Conventions Used in This Document
2.1. Acronyms
BDS BeiDou Navigation Satellite System
BITS Building Integrated Timing Supply
CoS Class of Service
DSCP Differentiated Services Code Point
ECN Explicit Congestion Notification
GLONASS Global Orbiting Navigation Satellite System
GPS Global Positioning System [GPS]
HMAC Hashed Message Authentication Code
LORAN-C Long Range Navigation System Version C
MBZ Must Be Zero
NTP Network Time Protocol [RFC5905]
PMF Performance Measurement Function
PTP Precision Time Protocol [IEEE.1588.2008]
RP Reverse Path
SMI Structure of Management Information
SSID STAMP Session Identifier
SSU Synchronization Supply Unit
STAMP Simple Two-way Active Measurement Protocol
TLV Type-Length-Value
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. STAMP Test Session Identifier
The STAMP Session-Sender transmits test packets to the STAMP Session-
Reflector. The STAMP Session-Reflector receives the Session-Sender's
packet and acts according to the configuration and optional control
information communicated in the Session-Sender's test packet. 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. STAMP supports two
modes: unauthenticated and authenticated. Unauthenticated STAMP test
packets are compatible on the wire with unauthenticated TWAMP-Test
[RFC5357] packets.
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.
A STAMP Session is identified by the 4-tuple (source and destination
IP addresses, source and destination UDP port numbers). A STAMP
Session-Sender MAY generate a locally unique STAMP Session Identifier
(SSID). The SSID is a two-octet, non-zero unsigned integer. The
SSID generation policy is implementation specific. [NUM-IDS-GEN]
thoroughly analyzes common algorithms for identifier generation and
their vulnerabilities. For example, an implementation can use the
algorithms described in Section 7.1 of [NUM-IDS-GEN]. An
implementation MUST NOT assign the same identifier to different STAMP
test sessions. A Session-Sender MAY use the SSID to identify a STAMP
test session. If the SSID is used, it MUST be present in each test
packet of the given test session. In the unauthenticated mode, the
SSID is located as displayed in Figure 1.
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 | SSID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| |
| MBZ (28 octets) |
| |
| |
| |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ TLVs ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 1: The Format of an Extended STAMP Session-Sender Test
Packet in Unauthenticated Mode
An implementation of the STAMP Session-Reflector that supports this
specification MUST identify a STAMP Session using the SSID in
combination with elements of the usual 4-tuple for the session.
Before a test session commences, a Session-Reflector MUST be
provisioned with all the elements that identify the STAMP Session. A
STAMP Session-Reflector MUST discard non-matching STAMP test packets.
The means of provisioning the STAMP Session identification is outside
the scope of this specification. A conforming implementation of a
STAMP Session-Reflector MUST copy the SSID value from the received
test packet and put it into the reflected packet, as displayed in
Figure 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 | SSID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Receive Timestamp |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Session-Sender Sequence Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Session-Sender Timestamp |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Session-Sender Error Estimate | MBZ |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Ses-Sender TTL | MBZ |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ TLVs ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 2: The Format of an Extended STAMP Session-Reflector Test
Packet in Unauthenticated Mode
A STAMP Session-Reflector that does not support this specification
will return the zeroed SSID field in the reflected STAMP test packet.
The Session-Sender MAY stop the session if it receives a zeroed SSID
field. An implementation of a Session-Sender MUST support control of
its behavior in such a scenario. If the test session is not stopped,
the Session-Sender can, for example, send a base STAMP packet
[RFC8762] or continue transmitting STAMP test packets with the SSID.
The location of the SSID field in the authenticated mode is shown in
Figures 3 and 4.
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 | SSID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ ~
| MBZ (68 octets) |
~ ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| HMAC (16 octets) |
| |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ TLVs ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 3: The Format of an Extended STAMP Session-Sender Test
Packet 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 | SSID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| MBZ (4 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) |
| |
| |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ TLVs ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 4: The Format of an Extended STAMP Session-Reflector Test
Packet in Authenticated Mode
4. TLV Extensions to STAMP
The Type-Length-Value (TLV) encoding scheme provides a flexible
extension mechanism for optional informational elements. TLV is an
optional field in the STAMP test packet. Multiple TLVs MAY be placed
in a STAMP test packet. Additional TLVs may be enclosed within a
given TLV, subject to the semantics of the (outer) TLV in question.
TLVs have a one-octet STAMP TLV Flags field, a one-octet Type field,
and a two-octet Length field that is equal to the length of the Value
field in octets. If a Type value for a TLV or sub-TLV is in the
range for Private Use [RFC8126], the length MUST be at least 4, and
the first four octets MUST be that vendor's Structure of Management
Information (SMI) Private Enterprise Code, as recorded in IANA's "SMI
Network Management Private Enterprise Codes" subregistry, in network
octet order. The rest of the Value field is private to the vendor.
The following sections describe the use of TLVs for STAMP that extend
the STAMP capability beyond its base specification.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|STAMP TLV Flags| Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ Value ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 5: TLV Format in a STAMP Extended Packet
The fields are defined as follows:
STAMP TLV Flags: An eight-bit field. The detailed format and
interpretation of flags defined in this specification are below.
Type: A one-octet field that characterizes the interpretation of the
Value field. It is allocated by IANA, as specified in
Section 5.1.
Length: A two-octet field equal to the length of the Value field in
octets.
Value: A variable-length field. Its interpretation and encoding are
determined by the value of the Type field.
All multi-byte fields in TLVs defined in this specification are in
network byte order.
The format of the STAMP TLV Flags is displayed in Figure 6, and the
location of flags is defined in Section 5.2.
0 1 2 3 4 5 6 7
+-+-+-+-+-+-+-+-+
|U|M|I|R|R|R|R|R|
+-+-+-+-+-+-+-+-+
Figure 6: STAMP TLV Flags Format
The fields are defined as follows:
U (Unrecognized): A one-bit flag. A Session-Sender MUST set the U
flag to 1 before transmitting an extended STAMP test packet. A
Session-Reflector MUST set the U flag to 1 if the Session-
Reflector has not understood the TLV. Otherwise, the Session-
Reflector MUST set the U flag in the reflected packet to 0.
M (Malformed): A one-bit flag. A Session-Sender MUST set the M flag
to 0 before transmitting an extended STAMP test packet. A
Session-Reflector MUST set the M flag to 1 if the Session-
Reflector determined the TLV is malformed, i.e., the Length field
value is not valid for the particular type, or the remaining
length of the extended STAMP packet is less than the size of the
TLV. Otherwise, the Session-Reflector MUST set the M flag in the
reflected packet to 0.
I (Integrity): A one-bit flag. A Session-Sender MUST set the I flag
to 0 before transmitting an extended STAMP test packet. A
Session-Reflector MUST set the I flag to 1 if the STAMP extensions
have failed HMAC verification (Section 4.8). Otherwise, the
Session-Reflector MUST set the I flag in the reflected packet to
0.
R: Reserved flags for future use. These flags MUST be zeroed on
transmit and ignored on receipt.
A STAMP node, whether Session-Sender or Session-Reflector, receiving
a test packet MUST determine whether the packet is a base STAMP
packet or whether it includes one or more TLVs. The node MUST
compare the value in the Length field of the UDP header and the
length of the base STAMP test packet in the mode, unauthenticated or
authenticated, based on the configuration of the particular STAMP
test session. If the difference between the two values is greater
than the length of the UDP header, then the test packet includes one
or more STAMP TLVs that immediately follow the base STAMP test
packet. A Session-Reflector that does not support STAMP extensions
will not process but copy them into the reflected packet, as defined
in Section 4.3 of [RFC8762]. A Session-Reflector that supports TLVs
will indicate specific TLVs that it did not process by setting the U
flag to 1 in those TLVs.
A STAMP Session-Sender that has received a reflected STAMP test
packet with extension TLVs MUST validate each TLV:
* If the U flag is set, the STAMP system MUST skip the processing of
the TLV.
* If the M flag is set, the STAMP system MUST stop processing the
remainder of the extended STAMP packet.
* If the I flag is set, the STAMP system MUST discard all TLVs and
MUST stop processing the remainder of the extended STAMP packet.
* If an implementation of a Session-Reflector does not recognize the
Type field value, it MUST include a copy of the TLV in the
reflected STAMP packet. The Session-Reflector MUST set the U flag
to 1. The Session-Reflector MUST skip the processing of the
unrecognized TLV.
* If a TLV is malformed, the processing of extension TLVs MUST be
stopped. The Session-Reflector MUST copy the remainder of the
received extended STAMP packet into the reflected STAMP packet.
The Session-Reflector MUST set the M flag to 1.
4.1. Extra Padding TLV
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|STAMP TLV Flags| Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
~ Extra Padding ~
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 7: Extra Padding TLV
The fields are defined as follows:
STAMP TLV Flags: An eight-bit field. Its format is presented in
Figure 6.
Type: A one-octet field. Value 1 has been allocated by IANA
(Section 5.1).
Length: A two-octet field equal to the length of the Extra Padding
field in octets.
Extra Padding: This field SHOULD be filled by a sequence of
pseudorandom numbers. The field MAY be filled with all zeros. An
implementation MUST control the content of the Extra Padding
field.
The Extra Padding TLV is similar to the Packet Padding field in a
TWAMP-Test packet [RFC5357]. The use of the Extra Padding TLV is
RECOMMENDED to perform a STAMP test using test packets that are
larger than the base STAMP packet [RFC8762]. The length of the base
STAMP packet is 44 octets in the unauthenticated mode or 112 octets
in the authenticated mode. The Extra Padding TLV MAY be present more
than one time in an extended STAMP test packet.
4.2. Location TLV
STAMP Session-Senders MAY include the variable-size Location TLV to
query location information from the Session-Reflector. The Session-
Sender MUST NOT fill any information fields except for the STAMP TLV
Flags, Type, and Length fields. The Session-Reflector MUST verify
that the TLV is well formed. If it is not, the Session-Reflector
follows the procedure defined in Section 4 for a malformed TLV.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|STAMP TLV Flags| Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Destination Port | Source Port |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ Sub-TLVs ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 8: Location TLV
The fields are defined as follows:
STAMP TLV Flags: An eight-bit field. Its format is presented in
Figure 6.
Type: A one-octet field. Value 2 has been allocated by IANA
(Section 5.1).
Length: A two-octet field equal to the length of the Value field in
octets.
Destination Port: A two-octet UDP destination port number of the
received STAMP packet.
Source Port: A two-octet UDP source port number of the received
STAMP packet.
Sub-TLVs: A sequence of sub-TLVs, as defined further in this
section. The sub-TLVs are used by the Session-Sender to request
location information with generic sub-TLV types, and the Session-
Reflector responds with the corresponding more-specific sub-TLVs
for the type of address (e.g., IPv4 or IPv6) used at the Session-
Reflector.
Note that all fields not filled by either a Session-Sender or
Session-Reflector are transmitted with all bits set to zero.
4.2.1. Location Sub-TLVs
A sub-TLV in the Location TLV uses the format displayed in Figure 5.
Handling of the U and M flags in the sub-TLV is as defined in
Section 4. The I flag MUST be set by a Session-Sender and Session-
Reflector to 0 before transmission and its value ignored on receipt.
The following types of sub-TLVs for the Location TLV are defined in
this specification (Table 5 lists the Type values):
Source MAC Address sub-TLV: A 12-octet sub-TLV. The Type value is
1. The value of the Length field MUST be equal to 8. The Value
field is an 8-octet MBZ field that MUST be zeroed on transmission
and ignored on receipt.
Source EUI-48 Address sub-TLV: A 12-octet sub-TLV that includes the
EUI-48 source MAC address. The Type value is 2. The value of the
Length field MUST be equal to 8.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| EUI-48 Address |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | MBZ |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 9: The Value Field of the Source EUI-48 Address Sub-TLV
The Value field consists of the following fields (Figure 9):
EUI-48 Address: A six-octet field.
MBZ: A two-octet field. It MUST be zeroed on transmission and
ignored on receipt.
Source EUI-64 Address sub-TLV: A 12-octet sub-TLV that includes the
EUI-64 source MAC address. The Type value is 3. The value of the
Length field MUST be equal to 8. The Value field consists of an
eight-octet EUI-64 field.
Destination IP Address sub-TLV: A 20-octet sub-TLV. The Type value
is 4. The value of the Length field MUST be equal to 16. The
Value field consists of a 16-octet MBZ field that MUST be zeroed
on transmit and ignored on receipt.
Destination IPv4 Address sub-TLV: A 20-octet sub-TLV that includes
the IPv4 destination address. The Type value is 5. The value of
the Length field MUST be equal to 16.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IPv4 Address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ MBZ (12 octets) ~
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 10: IPv4 Address in a Sub-TLV's Value Field
The Value field consists of the following fields (Figure 10):
IPv4 Address: A four-octet field.
MBZ: A 12-octet field. It MUST be zeroed on transmit and ignored
on receipt.
Destination IPv6 Address sub-TLV: A 20-octet sub-TLV that includes
the IPv6 destination address. The Type value is 6. The value of
the Length field MUST be equal to 16. The Value field is a
16-octet IPv6 Address field.
Source IP Address sub-TLV: A 20-octet sub-TLV. The Type value is 7.
The value of the Length field MUST be equal to 16. The Value
field is a 16-octet MBZ field that MUST be zeroed on transmit and
ignored on receipt.
Source IPv4 Address sub-TLV: A 20-octet sub-TLV that includes the
IPv4 source address. The Type value is 8. The value of the
Length field MUST be equal to 16. The Value field consists of the
following fields (Figure 10):
IPv4 Address: A four-octet field.
MBZ: A 12-octet field. It MUST be zeroed on transmit and ignored
on receipt.
Source IPv6 Address sub-TLV: A 20-octet sub-TLV that includes the
IPv6 source address. The Type value is 9. The value of the
Length field MUST be equal to 16. The Value field is a 16-octet
IPv6 Address field.
4.2.2. Theory of Operation of Location TLV
The Session-Reflector that received an extended STAMP packet with the
Location TLV MUST include in the reflected packet the Location TLV
with a length equal to the Location TLV length in the received
packet. Based on the local policy, the Session-Reflector MAY leave
some fields unreported by filling them with zeroes. An
implementation of the stateful Session-Reflector MUST provide control
for managing such policies.
A Session-Sender MAY include the Source MAC Address sub-TLV in the
Location TLV. If the Session-Reflector receives the Location TLV
that includes the Source MAC Address sub-TLV, it MUST include the
Source EUI-48 Address sub-TLV if the source MAC address of the
received extended test packet is in EUI-48 format. And the Session-
Reflector MUST copy the value of the source MAC address in the EUI-48
field. Otherwise, the Session-Reflector MUST use the Source EUI-64
Address sub-TLV and MUST copy the value of the Source MAC Address
from the received packet into the EUI-64 field. If the received
extended STAMP test packet does not have the Source MAC Address, the
Session-Reflector MUST zero the EUI-64 field before transmitting the
reflected packet.
A Session-Sender MAY include the Destination IP Address sub-TLV in
the Location TLV. If the Session-Reflector receives the Location TLV
that includes the Destination IP Address sub-TLV, it MUST include the
Destination IPv4 Address sub-TLV if the source IP address of the
received extended test packet is of the IPv4 address family. And the
Session-Reflector MUST copy the value of the destination IP address
in the IPv4 Address field. Otherwise, the Session-Reflector MUST use
the Destination IPv6 Address sub-TLV and MUST copy the value of the
destination IP address from the received packet into the IPv6 Address
field.
A Session-Sender MAY include the Source IP Address sub-TLV in the
Location TLV. If the Session-Reflector receives the Location TLV
that includes the Source IP Address sub-TLV, it MUST include the
Source IPv4 Address sub-TLV if the source IP address of the received
extended test packet is of the IPv4 address family. And the Session-
Reflector MUST copy the value of the source IP address in the IPv4
Address field. Otherwise, the Session-Reflector MUST use the Source
IPv6 Address sub-TLV and MUST copy the value of the source IP address
from the received packet into the IPv6 Address field.
The Location TLV MAY be used to determine the last-hop IP addresses,
ports, and last-hop MAC address for STAMP packets. The MAC address
can indicate a path switch on the last hop. The IP addresses and UDP
ports will indicate if there is a NAT router on the path. It allows
the Session-Sender to identify the IP address of the Session-
Reflector behind the NAT and detect changes in the NAT mapping that
could result in sending the STAMP packets to the wrong Session-
Reflector.
4.3. Timestamp Information TLV
The STAMP Session-Sender MAY include the Timestamp Information TLV to
request information from the Session-Reflector. The Session-Sender
MUST NOT fill any information fields except for STAMP TLV Flags,
Type, and Length. All other fields MUST be filled with zeroes. The
Session-Reflector MUST validate the Length value of the TLV. If the
value of the Length field is invalid, the Session-Reflector follows
the procedure defined in Section 4 for a malformed TLV.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|STAMP TLV Flags| Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sync Src In | Timestamp In | Sync Src Out | Timestamp Out |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ Optional sub-TLVs ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 11: Timestamp Information TLV
The fields are defined as follows:
STAMP TLV Flags: An eight-bit field. Its format is presented in
Figure 6.
Type: A one-octet field. Value 3 has been allocated by IANA
(Section 5.1).
Length: A two-octet field, set equal to the length of the Value
field in octets (Figure 5).
Sync Src In: A one-octet field that characterizes the source of
clock synchronization at the ingress of a Session-Reflector.
There are several methods for synchronizing the clock, e.g., the
Network Time Protocol (NTP) [RFC5905]. Table 7 lists the possible
values.
Timestamp In: A one-octet field that characterizes the method by
which the ingress of the Session-Reflector obtained the timestamp
T2. A timestamp may be obtained with hardware assistance via a
software API from a local wall clock or from a remote clock (the
latter is referred to as a "control plane"). Table 9 lists the
possible values.
Sync Src Out: A one-octet field that characterizes the source of
clock synchronization at the egress of the Session-Reflector.
Table 7 lists the possible values.
Timestamp Out: A one-octet field that characterizes the method by
which the egress of the Session-Reflector obtained the timestamp
T3. Table 9 lists the possible values.
Optional sub-TLVs: An optional variable-length field.
4.4. Class of Service TLV
The STAMP Session-Sender MAY include a Class of Service (CoS) TLV in
the STAMP test packet. The format of the CoS TLV is presented in
Figure 12.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|STAMP TLV Flags| Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| DSCP1 | DSCP2 |ECN| RP| Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 12: Class of Service TLV
The fields are defined as follows:
STAMP TLV Flags: An eight-bit field. Its format is presented in
Figure 6.
Type: A one-octet field. Value 4 has been allocated by IANA
(Section 5.1).
Length: A two-octet field, set equal to the value 4.
DSCP1: The Differentiated Services Code Point (DSCP) intended by the
Session-Sender to be used as the DSCP value of the reflected test
packet.
DSCP2: The received value in the DSCP field at the ingress of the
Session-Reflector.
ECN: The received value in the ECN field at the ingress of the
Session-Reflector.
RP (Reverse Path): A two-bit field. A Session-Sender MUST set the
value of the RP field to 0 on transmission.
Reserved: A 16-bit field that MUST be zeroed on transmission and
ignored on receipt.
A STAMP Session-Reflector that receives a test packet with the CoS
TLV MUST include the CoS TLV in the reflected test packet. Also, the
Session-Reflector MUST copy the value of the DSCP and ECN fields of
the IP header of the received STAMP test packet into the DSCP2 field
in the reflected test packet. Finally, the Session-Reflector MUST
use the local policy to verify whether the CoS corresponding to the
value of the DSCP1 field is permitted in the domain. If it is, the
Session-Reflector MUST set the DSCP field's value in the IP header of
the reflected test packet equal to the value of the DSCP1 field of
the received test packet. Otherwise, the Session-Reflector MUST use
the DSCP value of the received STAMP packet and set the value of the
RP field to 1. Upon receiving the reflected packet, if the value of
the RP field is 0, the Session-Sender will save the DSCP and ECN
values for analysis of the CoS in the reverse direction. If the
value of the RP field in the received reflected packet is 1, only CoS
in the forward direction can be analyzed.
Re-mapping of CoS can be used to provide multiple services (e.g., 2G,
3G, LTE in mobile backhaul networks) over the same network. But if
it is misconfigured, then it is often difficult to diagnose the root
cause of excessive packet drops of higher-level service while packet
drops for lower service packets are at a normal level. Using a CoS
TLV in STAMP testing helps to troubleshoot the existing problem and
also verify whether Diffserv policies are processing CoS as required
by the configuration.
4.5. Direct Measurement TLV
The Direct Measurement TLV enables collection of the number of in-
profile packets, i.e., packets that form a specific data flow, that
had been transmitted and received by the Session-Sender and Session-
Reflector, respectively. The definition of "in-profile packet" is
outside the scope of this document and is left to the test operators
to determine.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|STAMP TLV Flags| Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Session-Sender Tx counter (S_TxC) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Session-Reflector Rx counter (R_RxC) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Session-Reflector Tx counter (R_TxC) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 13: Direct Measurement TLV
The fields are defined as follows:
STAMP TLV Flags: An eight-bit field. Its format is presented in
Figure 6.
Type: A one-octet field. Value 5 has been allocated by IANA
(Section 5.1).
Length: A two-octet field equal to the length of the Value field in
octets. The Length field value MUST equal 12 octets.
Session-Sender Tx counter (S_TxC): A four-octet field. The Session-
Sender MUST set its value equal to the number of the transmitted
in-profile packets.
Session-Reflector Rx counter (R_RxC): A four-octet field. It MUST
be zeroed by the Session-Sender on transmit and ignored by the
Session-Reflector on receipt. The Session-Reflector MUST fill it
with the value of in-profile packets received.
Session-Reflector Tx counter (R_TxC): A four-octet field. It MUST
be zeroed by the Session-Sender and ignored by the Session-
Reflector on receipt. The Session-Reflector MUST fill it with the
value of the transmitted in-profile packets.
A Session-Sender MAY include the Direct Measurement TLV in a STAMP
test packet. If the received STAMP test packet includes the Direct
Measurement TLV, the Session-Reflector MUST include it in the
reflected test packet. The Session-Reflector MUST copy the value
from the S_TxC field of the received test packet into the same field
of the reflected packet before its transmission.
4.6. Access Report TLV
A STAMP Session-Sender MAY include an Access Report TLV (Figure 14)
to indicate changes to the access network status to the Session-
Reflector. The definition of an access network is outside the scope
of this document.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|STAMP TLV Flags| Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ID | Resv | Return Code | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 14: Access Report TLV
The fields are defined as follows:
STAMP TLV Flags: An eight-bit field. Its format is presented in
Figure 6.
Type: A one-octet field. Value 6 has been allocated by IANA
(Section 5.1).
Length: A two-octet field, set equal to the value 4.
ID (Access ID): A four-bit field that identifies the access network,
e.g., 3GPP (Radio Access Technologies specified by 3GPP) or non-
3GPP (accesses that are not specified by 3GPP) [TS23501]. The
value is one of the following:
1: 3GPP Network
2: Non-3GPP Network
All other values are invalid; a TLV that contains values other
than '1' or '2' MUST be discarded.
Resv: A four-bit field that MUST be zeroed on transmission and
ignored on receipt.
Return Code: A one-octet field that identifies the report signal,
e.g., available or unavailable. The value is supplied to the
STAMP endpoint through some mechanism that is outside the scope of
this document. Section 5.6 lists the possible values.
Reserved: A two-octet field that MUST be zeroed on transmission and
ignored on receipt.
The STAMP Session-Sender that includes the Access Report TLV sets the
value of the Access ID field according to the type of access network
it reports on. Also, the Session-Sender sets the value of the Return
Code field to reflect the operational state of the access network.
The mechanism to determine the state of the access network is outside
the scope of this specification. A STAMP Session-Reflector that
received the test packet with the Access Report TLV MUST include the
Access Report TLV in the reflected test packet. The Session-
Reflector MUST set the value of the Access ID and Return Code fields
equal to the values of the corresponding fields from the test packet
it has received.
The Session-Sender MUST also arm a retransmission timer after sending
a test packet that includes the Access Report TLV. This timer MUST
be disarmed upon reception of the reflected STAMP test packet that
includes the Access Report TLV. In the event the timer expires
before such a packet is received, the Session-Sender MUST retransmit
the STAMP test packet that contains the Access Report TLV. This
retransmission SHOULD be repeated up to four times before the
procedure is aborted. Setting the value for the retransmission timer
is based on local policies and the network environment. The default
value of the retransmission timer for the Access Report TLV SHOULD be
three seconds. An implementation MUST provide control of the
retransmission timer value and the number of retransmissions.
The Access Report TLV is used by the Performance Measurement Function
(PMF) components of the Access Steering, Switching, and Splitting
feature for 5G networks [TS23501]. The PMF component in the User
Equipment acts as the STAMP Session-Sender, and the PMF component in
the User Plane Function acts as the STAMP Session-Reflector.
4.7. Follow-Up Telemetry TLV
A Session-Reflector might be able to put only an "SW Local" (see
Table 9) timestamp in the Follow-Up Timestamp field. But the hosting
system might provide a timestamp closer to the start of the actual
packet transmission even though it is not possible to deliver the
information to the Session-Sender in time for the packet itself.
This timestamp might nevertheless be important for the Session-
Sender, as it improves the accuracy of network delay measurement by
minimizing the impact of egress queuing delays on the measurement.
A STAMP Session-Sender MAY include the Follow-Up Telemetry TLV to
request information from the Session-Reflector. The Session-Sender
MUST set the Follow-Up Telemetry Type and Length fields to their
appropriate values. The Sequence Number and Follow-Up Timestamp
fields MUST be zeroed on transmission by the Session-Sender and
ignored by the Session-Reflector upon receipt of the STAMP test
packet that includes the Follow-Up Telemetry TLV. The Session-
Reflector MUST validate the Length value of the STAMP test packet.
If the value of the Length field is invalid, the Session-Reflector
MUST zero the Sequence Number and Follow-Up Timestamp fields and set
the M flag in the STAMP TLV Flags field in the reflected packet. If
the Session-Reflector is in the stateless mode (defined in
Section 4.2 of [RFC8762]), it MUST zero the Sequence Number and
Follow-Up Timestamp fields.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|STAMP TLV Flags| Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sequence Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Follow-Up Timestamp |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Timestamp M | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 15: Follow-Up Telemetry TLV
The fields are defined as follows:
STAMP TLV Flags: An eight-bit field. Its format is presented in
Figure 6.
Type: A one-octet field. Value 7 has been allocated by IANA
(Section 5.1).
Length: A two-octet field, set equal to the value 16 octets.
Sequence Number: A four-octet field indicating the sequence number
of the last packet reflected in the same STAMP test session.
Since the Session-Reflector runs in the stateful mode (defined in
Section 4.2 of [RFC8762]), it is the Session-Reflector's Sequence
Number of the previous reflected packet.
Follow-Up Timestamp: An eight-octet field, with the format indicated
by the Z flag of the Error Estimate field of the STAMP base
packet, which is contained in this reflected test packet
transmitted by a Session-Reflector, as described in Section 4.2.1
of [RFC8762]. It carries the timestamp when the reflected packet
with the specified sequence number was sent.
Timestamp M(ode): A one-octet field that characterizes the method by
which the entity that transmits a reflected STAMP packet obtained
the Follow-Up Timestamp. Table 9 lists the possible values.
Reserved: A three-octet field. Its value MUST be zeroed on
transmission and ignored on receipt.
4.8. HMAC TLV
The STAMP authenticated mode protects the integrity of data collected
in the STAMP base packet. STAMP extensions are designed to provide
valuable information about the condition of a network, and protecting
the integrity of that data is also essential. All authenticated
STAMP base packets (per Sections 4.2.2 and 4.3.2 of [RFC8762])
compatible with this specification MUST additionally authenticate the
optional TLVs by including the keyed Hashed Message Authentication
Code (HMAC) TLV, with the sole exception of when there is only one
TLV present and it is the Extended Padding TLV. The HMAC TLV MUST
follow all TLVs included in a STAMP test packet except for the Extra
Padding TLV. If the HMAC TLV appears in any other position in a
STAMP extended test packet, then the situation MUST be processed as
HMAC verification failure, as defined below in this section. The
HMAC TLV MAY be used to protect the integrity of STAMP extensions in
the STAMP unauthenticated mode. An implementation of STAMP
extensions MUST provide controls to enable the integrity protection
of STAMP extensions in the STAMP unauthenticated mode.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|STAMP TLV Flags| Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| HMAC |
| |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 16: HMAC TLV
The fields are defined as follows:
STAMP TLV Flags: An eight-bit field. Its format is presented in
Figure 6.
Type: A one-octet field. Value 8 has been allocated by IANA
(Section 5.1).
Length: A two-octet field, set equal to the value 16 octets.
HMAC: A 16-octet field that carries the HMAC digest of the text of
all preceding TLVs.
As defined in [RFC8762], STAMP uses HMAC-SHA-256 truncated to 128
bits (see [RFC4868]). All considerations regarding using the key
listed in Section 4.4 of [RFC8762] are fully applicable to the use of
the HMAC TLV. Key management and the mechanisms to distribute the
HMAC key are outside the scope of this specification. The HMAC TLV
is anticipated to track updates in the base STAMP protocol [RFC8762],
including the use of more advanced cryptographic algorithms. HMAC is
calculated as defined in [RFC2104] over text as the concatenation of
the Sequence Number field of the base STAMP packet and all preceding
TLVs. The digest then MUST be truncated to 128 bits and written into
the HMAC field. If the HMAC TLV is present in the extended STAMP
test packet, e.g., in the authenticated mode, HMAC MUST be verified
before using any data in the included STAMP TLVs. If HMAC
verification by the Session-Reflector fails, then the Session-
Reflector MUST stop processing the received extended STAMP test
packet. The Session-Reflector MUST copy the TLVs from the received
STAMP test packet into the reflected packet. The Session-Reflector
MUST set the I flag in each TLV copied over into the reflected packet
to 1 before transmitting the reflected test packet. If the Session-
Sender receives the extended STAMP test packet with I flag set to 1,
then the Session-Sender MUST stop processing TLVs in the reflected
test packet. If HMAC verification by the Session-Sender fails, then
the Session-Sender MUST stop processing TLVs in the reflected
extended STAMP packet.
5. IANA Considerations
IANA has created the following subregistries under the "Simple Two-
way Active Measurement Protocol (STAMP) TLV Types" registry.
5.1. STAMP TLV Types Subregistry
IANA has created the "STAMP TLV Types" subregistry. The code points
in this registry are allocated according to the registration
procedures [RFC8126] described in Table 1.
+===========+=========================+
| Range | Registration Procedures |
+===========+=========================+
| 1 - 175 | IETF Review |
+-----------+-------------------------+
| 176 - 239 | First Come First Served |
+-----------+-------------------------+
| 240 - 251 | Experimental Use |
+-----------+-------------------------+
| 252 - 254 | Private Use |
+-----------+-------------------------+
Table 1: Registration Procedures
for the STAMP TLV Types Subregistry
Per this document, IANA has allocated the following values in the
"STAMP TLV Types" subregistry:
+=======+=======================+===========+
| Value | Description | Reference |
+=======+=======================+===========+
| 0 | Reserved | RFC 8972 |
+-------+-----------------------+-----------+
| 1 | Extra Padding | RFC 8972 |
+-------+-----------------------+-----------+
| 2 | Location | RFC 8972 |
+-------+-----------------------+-----------+
| 3 | Timestamp Information | RFC 8972 |
+-------+-----------------------+-----------+
| 4 | Class of Service | RFC 8972 |
+-------+-----------------------+-----------+
| 5 | Direct Measurement | RFC 8972 |
+-------+-----------------------+-----------+
| 6 | Access Report | RFC 8972 |
+-------+-----------------------+-----------+
| 7 | Follow-Up Telemetry | RFC 8972 |
+-------+-----------------------+-----------+
| 8 | HMAC | RFC 8972 |
+-------+-----------------------+-----------+
| 255 | Reserved | RFC 8972 |
+-------+-----------------------+-----------+
Table 2: STAMP TLV Types
5.2. STAMP TLV Flags Subregistry
IANA has created the "STAMP TLV Flags" subregistry. The registration
procedure is "IETF Review" [RFC8126]. The flags are 8 bits. Per
this document, IANA has allocated the following bit positions in the
"STAMP TLV Flags" subregistry.
+==============+========+========================+===========+
| Bit position | Symbol | Description | Reference |
+==============+========+========================+===========+
| 0 | U | Unrecognized TLV | RFC 8972 |
+--------------+--------+------------------------+-----------+
| 1 | M | Malformed TLV | RFC 8972 |
+--------------+--------+------------------------+-----------+
| 2 | I | Integrity check failed | RFC 8972 |
+--------------+--------+------------------------+-----------+
Table 3: STAMP TLV Flags
5.3. STAMP Sub-TLV Types Subregistry
IANA has created the "STAMP Sub-TLV Types" subregistry. The code
points in this registry are allocated according to the registration
procedures [RFC8126] described in Table 4.
+===========+=========================+
| Range | Registration Procedures |
+===========+=========================+
| 1 - 175 | IETF Review |
+-----------+-------------------------+
| 176 - 239 | First Come First Served |
+-----------+-------------------------+
| 240 - 251 | Experimental Use |
+-----------+-------------------------+
| 252 - 254 | Private Use |
+-----------+-------------------------+
Table 4: Registration Procedures
for the STAMP Sub-TLV Types
Subregistry
Per this document, IANA has allocated the following values in the
"STAMP Sub-TLV Types" subregistry:
+=======+==========================+==========+===========+
| Value | Description | TLV Used | Reference |
+=======+==========================+==========+===========+
| 0 | Reserved | | RFC 8972 |
+-------+--------------------------+----------+-----------+
| 1 | Source MAC Address | Location | RFC 8972 |
+-------+--------------------------+----------+-----------+
| 2 | Source EUI-48 Address | Location | RFC 8972 |
+-------+--------------------------+----------+-----------+
| 3 | Source EUI-64 Address | Location | RFC 8972 |
+-------+--------------------------+----------+-----------+
| 4 | Destination IP Address | Location | RFC 8972 |
+-------+--------------------------+----------+-----------+
| 5 | Destination IPv4 Address | Location | RFC 8972 |
+-------+--------------------------+----------+-----------+
| 6 | Destination IPv6 Address | Location | RFC 8972 |
+-------+--------------------------+----------+-----------+
| 7 | Source IP Address | Location | RFC 8972 |
+-------+--------------------------+----------+-----------+
| 8 | Source IPv4 Address | Location | RFC 8972 |
+-------+--------------------------+----------+-----------+
| 9 | Source IPv6 Address | Location | RFC 8972 |
+-------+--------------------------+----------+-----------+
| 255 | Reserved | | RFC 8972 |
+-------+--------------------------+----------+-----------+
Table 5: STAMP Sub-TLV Types
5.4. STAMP Synchronization Sources Subregistry
IANA has created the "STAMP Synchronization Sources" subregistry.
The code points in this registry are allocated according to the
registration procedures [RFC8126] described in Table 6.
+===========+=========================+
| Range | Registration Procedures |
+===========+=========================+
| 1 - 127 | IETF Review |
+-----------+-------------------------+
| 128 - 239 | First Come First Served |
+-----------+-------------------------+
| 240 - 249 | Experimental Use |
+-----------+-------------------------+
| 250 - 254 | Private Use |
+-----------+-------------------------+
Table 6: Registration Procedures
for the STAMP Synchronization
Sources Subregistry
Per this document, IANA has allocated the following values in the
"STAMP Synchronization Sources" subregistry:
+=======+=================================+===========+
| Value | Description | Reference |
+=======+=================================+===========+
| 0 | Reserved | RFC 8972 |
+-------+---------------------------------+-----------+
| 1 | NTP | RFC 8972 |
+-------+---------------------------------+-----------+
| 2 | PTP | RFC 8972 |
+-------+---------------------------------+-----------+
| 3 | SSU/BITS | RFC 8972 |
+-------+---------------------------------+-----------+
| 4 | GPS/GLONASS/LORAN-C/BDS/Galileo | RFC 8972 |
+-------+---------------------------------+-----------+
| 5 | Local free-running | RFC 8972 |
+-------+---------------------------------+-----------+
| 255 | Reserved | RFC 8972 |
+-------+---------------------------------+-----------+
Table 7: STAMP Synchronization Sources
5.5. STAMP Timestamping Methods Subregistry
IANA has created the "STAMP Timestamping Methods" subregistry. The
code points in this registry are allocated according to the
registration procedures [RFC8126] described in Table 8.
+===========+=========================+
| Range | Registration Procedures |
+===========+=========================+
| 1 - 127 | IETF Review |
+-----------+-------------------------+
| 128 - 239 | First Come First Served |
+-----------+-------------------------+
| 240 - 249 | Experimental Use |
+-----------+-------------------------+
| 250 - 254 | Private Use |
+-----------+-------------------------+
Table 8: Registration Procedures
for the STAMP Timestamping Methods
Subregistry
Per this document, IANA has allocated the following values in the
"STAMP Timestamping Methods" subregistry:
+=======+===============+===========+
| Value | Description | Reference |
+=======+===============+===========+
| 0 | Reserved | RFC 8972 |
+-------+---------------+-----------+
| 1 | HW Assist | RFC 8972 |
+-------+---------------+-----------+
| 2 | SW Local | RFC 8972 |
+-------+---------------+-----------+
| 3 | Control Plane | RFC 8972 |
+-------+---------------+-----------+
| 255 | Reserved | RFC 8972 |
+-------+---------------+-----------+
Table 9: STAMP Timestamping Methods
5.6. STAMP Return Codes Subregistry
IANA has created the "STAMP Return Codes" subregistry. The code
points in this registry are allocated according to the registration
procedures [RFC8126] described in Table 10.
+===========+=========================+
| Range | Registration Procedures |
+===========+=========================+
| 1 - 127 | IETF Review |
+-----------+-------------------------+
| 128 - 239 | First Come First Served |
+-----------+-------------------------+
| 240 - 249 | Experimental Use |
+-----------+-------------------------+
| 250 - 254 | Private Use |
+-----------+-------------------------+
Table 10: Registration Procedures
for the STAMP Return Codes
Subregistry
Per this document, IANA has allocated the following values in the
"STAMP Return Codes" subregistry:
+=======+=====================+===========+
| Value | Description | Reference |
+=======+=====================+===========+
| 0 | Reserved | RFC 8972 |
+-------+---------------------+-----------+
| 1 | Network available | RFC 8972 |
+-------+---------------------+-----------+
| 2 | Network unavailable | RFC 8972 |
+-------+---------------------+-----------+
| 255 | Reserved | RFC 8972 |
+-------+---------------------+-----------+
Table 11: STAMP Return Codes
6. Security Considerations
This document defines extensions to STAMP [RFC8762] and inherits all
the security considerations applicable to the base protocol.
Additionally, the HMAC TLV is defined in this document. Though the
HMAC TLV protects the integrity of STAMP extensions, it does not
protect against a replay attack. The use of the HMAC TLV is
discussed in detail in Section 4.8.
To protect against a malformed TLV, an implementation of a Session-
Sender and Session-Reflector MUST:
* check the setting of the M flag and
* validate the Length field value.
As this specification defines the mechanism to test DSCP mapping,
this document inherits all the security considerations discussed in
[RFC2474]. Monitoring and optional control of DSCP using the CoS TLV
may be used across the Internet so that the Session-Sender and the
Session-Reflector are located in domains that use different CoS
profiles. Thus, it is essential that an operator verify the set of
CoS values that is used in the Session-Reflector's domain. Also, an
implementation of a Session-Reflector SHOULD support a local policy
to confirm whether the value sent by the Session-Sender can be used
as the value of the DSCP field. Section 4.4 defines the use of that
local policy.
7. References
7.1. Normative References
[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>.
[RFC8126] Cotton, M., Leiba, B., and T. Narten, "Guidelines for
Writing an IANA Considerations Section in RFCs", BCP 26,
RFC 8126, DOI 10.17487/RFC8126, June 2017,
<https://www.rfc-editor.org/info/rfc8126>.
[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>.
[RFC8762] 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>.
7.2. Informative References
[GPS] "Global Positioning System (GPS) Standard Positioning
Service (SPS) Performance Standard", GPS SPS 5th Edition,
April 2020.
[IEEE.1588.2008]
"IEEE Standard for a Precision Clock Synchronization
Protocol for Networked Measurement and Control Systems",
IEEE Std. 1588-2008, DOI 10.1109/IEEESTD.2008.4579760,
July 2008, <https://doi.org/10.1109/IEEESTD.2008.4579760>.
[NUM-IDS-GEN]
Gont, F. and I. Arce, "On the Generation of Transient
Numeric Identifiers", Work in Progress, Internet-Draft,
draft-irtf-pearg-numeric-ids-generation-06, 13 January
2021, <https://tools.ietf.org/html/draft-irtf-pearg-
numeric-ids-generation-06>.
[RFC2474] Nichols, K., Blake, S., Baker, F., and D. Black,
"Definition of the Differentiated Services Field (DS
Field) in the IPv4 and IPv6 Headers", RFC 2474,
DOI 10.17487/RFC2474, December 1998,
<https://www.rfc-editor.org/info/rfc2474>.
[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>.
[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>.
[TS23501] 3GPP, "Technical Specification Group Services and System
Aspects; System Architecture for the 5G System (5GS);
Stage 2 (Release 16)", 3GPP TS 23.501, 2019.
Acknowledgments
The authors very much appreciate the thorough review and thoughtful
comments received from Tianran Zhou, Rakesh Gandhi, Yuezhong Song,
and Yali Wang. The authors express their gratitude to Al Morton for
his comments and valuable suggestions. The authors greatly
appreciate the comments and thoughtful suggestions received from
Martin Duke.
Contributors
The following individual contributed text to this document:
Guo Jun
ZTE Corporation
68# Zijinghua Road
Nanjing
Jiangsu, 210012
China
Phone: +86 18105183663
Email: guo.jun2@zte.com.cn
Authors' Addresses
Greg Mirsky
ZTE Corp.
Email: gregimirsky@gmail.com
Xiao Min
ZTE Corp.
Email: xiao.min2@zte.com.cn
Henrik Nydell
Accedian Networks
Email: hnydell@accedian.com
Richard Foote
Nokia
Email: footer.foote@nokia.com
Adi Masputra
Apple Inc.
One Apple Park Way
Cupertino, CA 95014
United States of America
Email: adi@apple.com
Ernesto Ruffini
OutSys
via Caracciolo, 65
20155 Milan
Italy
Email: eruffini@outsys.org
ISO Plain Language
On this page
§1Optional Extensions to STAMP
The Simple Two-way Active Measurement Protocol (STAMP) (RFC 8762) defines the base STAMP functionality. This document specifies the use of optional extensions that use Type-Length-Value (TLV) encoding. Such extensions enhance the STAMP base functions, such as measurement of one-way and round-trip delay, latency, packet loss, packet duplication, and out-of-order delivery of test packets. The specification defines the optional STAMP extensions, their formats, and the theory of operation. It also defines a STAMP Test Session Identifier as an update of the base STAMP specification.
In STAMP, the Session-Sender transmits test packets to the Session-Reflector. The Session-Reflector receives the packet and acts according to the configuration and the optional control information communicated in the Session-Sender's test packet. STAMP defines two different test packet formats, one for packets transmitted by the Session-Sender and one for packets transmitted by the Session-Reflector, and it supports two modes, unauthenticated and authenticated. Unauthenticated STAMP test packets are compatible on the wire with unauthenticated TWAMP-Test (RFC 5357) packets. By default, STAMP uses symmetrical packets, meaning that the size of the packet transmitted by the Session-Reflector equals the size of the packet it received.
STAMP is a way to measure delay between two points on a network by sending test packets and timing them. RFC 8972 adds optional extra fields to those packets, so a sender can ask the other end for things like its address, how its clock is set, or how a packet was classified, and can have the extra fields signed so nobody can change them.
- Test packet with optional TLVsCarries the sequence number, timestamp, session identifier and any TLVs the sender wants answered.
- Reflected packetSame size by default, with the SSID copied across and the TLVs filled in.
§3The STAMP Session Identifier
A STAMP Session is identified by the 4-tuple of source and destination IP addresses and source and destination UDP port numbers. A Session-Sender MAY generate a locally unique STAMP Session Identifier, the SSID. The SSID is a two-octet, non-zero unsigned integer, and the generation policy is implementation specific. An implementation MUST NOT assign the same identifier to different STAMP test sessions. If the SSID is used, it MUST be present in each test packet of the given test session, and in the unauthenticated mode it sits next to the Error Estimate field in the Session-Sender's packet and in the reflected packet.
An implementation of the Session-Reflector that supports this specification MUST identify a STAMP Session using the SSID together with elements of the usual 4-tuple. Before a test session commences, a Session-Reflector MUST be provisioned with all the elements that identify the session, and it MUST discard non-matching STAMP test packets. How that provisioning happens is outside the scope of this specification. A conforming Session-Reflector MUST copy the SSID value from the received test packet into the reflected packet.
A Session-Reflector that does not support this specification returns the zeroed SSID field in the reflected packet. The Session-Sender MAY stop the session if it receives a zeroed SSID field, and an implementation of a Session-Sender MUST support control of its behaviour in that scenario. If the session is not stopped, the Session-Sender can, for example, send a base STAMP packet or continue transmitting STAMP test packets with the SSID. The location of the SSID field in the authenticated mode is shown in the figures for the extended Session-Sender and Session-Reflector packets.
Two test sessions between the same pair of addresses look the same on the network. The session identifier is a small extra number that tells the reflector which session a packet belongs to. A reflector that does not know about it sends the number back as zero, and the sender can then decide whether to carry on.
| Field | Name | Size | Value | Description |
|---|---|---|---|---|
SEQUENCE-NUMBER | Sequence Number | 4 bytes | Identifies the test packet within the session. | |
TIMESTAMP | Timestamp | 8 bytes | When the sender sent the packet. | |
ERROR-ESTIMATE | Error Estimate | 2 bytes | Bound on the timestamp error, and the format of the timestamp. | |
SSID | SSID | 2 bytes | Two-octet non-zero identifier of the STAMP session. | |
MBZ | MBZ | 28 bytes | Must be zero. Optional TLVs follow the base packet. |
§4The TLV Header and Its Flags
The Type-Length-Value encoding scheme provides a flexible extension mechanism for optional informational elements. A TLV is an optional field in the STAMP test packet, and multiple TLVs MAY be placed in one packet. Additional TLVs may also be enclosed within a given TLV, subject to the semantics of the outer TLV. A TLV has a one-octet STAMP TLV Flags field, a one-octet Type field, and a two-octet Length field equal to the length of the Value field in octets. If a Type value falls in the Private Use range, the length MUST be at least 4 and the first four octets MUST be the vendor's Structure of Management Information Private Enterprise Code in network octet order. All multi-byte fields in the TLVs defined here are in network byte order.
The flags field carries three one-bit flags and five reserved bits. The U flag, for Unrecognized, is set by the Session-Sender to 1 before transmitting, and the Session-Reflector sets it to 1 in a TLV it did not understand, otherwise to 0. The M flag, for Malformed, is set to 0 by the Session-Sender, and the Session-Reflector sets it to 1 when it determines that the TLV is malformed, meaning the Length field is not valid for that type or the remaining length of the packet is less than the size of the TLV. The I flag, for Integrity, is set to 0 by the Session-Sender, and the Session-Reflector sets it to 1 when the STAMP extensions have failed HMAC verification. The reserved flags MUST be zeroed on transmit and ignored on receipt.
A node receiving a test packet MUST determine whether the packet is a base STAMP packet or includes one or more TLVs. It does so by comparing the value in the Length field of the UDP header with the length of the base STAMP test packet in the mode in use. If the difference is greater than the length of the UDP header, the packet includes one or more TLVs that immediately follow the base packet. A Session-Reflector that does not support STAMP extensions will not process them but will copy them into the reflected packet, while one that supports TLVs indicates the specific TLVs it did not process by setting the U flag.
A Session-Sender that receives a reflected packet with extension TLVs MUST validate each one. If the U flag is set, the system MUST skip the processing of that TLV. If the M flag is set, it MUST stop processing the remainder of the packet. If the I flag is set, it MUST discard all TLVs and stop processing the remainder of the packet.
Each optional field starts with a one-byte flags field, a one-byte type number, and a two-byte length. The three flags tell the sender what happened to that field: the reflector did not understand it, it was malformed, or its integrity check failed. A sender stops reading the rest of the packet when it sees the last two of those.
| Field | Name | Size | Value | Description |
|---|---|---|---|---|
FLAGS | STAMP TLV Flags | 1 byte | U for unrecognized, M for malformed, I for integrity failure; five reserved bits. | |
TYPE | Type | 1 byte | One-octet code that says how the Value field is to be read. | |
LENGTH | Length | 2 bytes | Length of the Value field in octets. The Value field follows. |
§4.1Padding, Location and Timestamp TLVs
The Extra Padding TLV, type 1, is similar to the Packet Padding field in a TWAMP-Test packet. It SHOULD be filled with a sequence of pseudorandom numbers and MAY be filled with all zeros. Its use is RECOMMENDED to perform a STAMP test using packets larger than the base STAMP packet, and the length of the base packet is 44 octets in the unauthenticated mode or 112 octets in the authenticated mode. The Extra Padding TLV MAY be present more than once in an extended packet.
The Location TLV, type 2, lets the Session-Sender query location information from the Session-Reflector. The Session-Sender MUST NOT fill any information fields except the flags, type and length. The TLV carries the destination and source UDP port numbers of the received STAMP packet and a sequence of sub-TLVs. The sub-TLVs let the Session-Sender ask for location information with generic types, and the Session-Reflector answers with the more specific type for the address family it uses. The defined sub-TLVs are the Source MAC Address, Source EUI-48 Address, Source EUI-64 Address, Destination IP Address, Destination IPv4 Address, Destination IPv6 Address, Source IP Address, Source IPv4 Address and Source IPv6 Address. For example, if the sender asks for the Source IP Address sub-TLV, the reflector MUST answer with the Source IPv4 Address sub-TLV when the source address of the received packet is IPv4, and with the Source IPv6 Address sub-TLV otherwise.
The Location TLV MAY be used to determine the last-hop IP addresses, ports and last-hop MAC address for STAMP packets. The MAC address can indicate a path switch on the last hop, and the IP addresses and UDP ports indicate whether there is a NAT router on the path. That lets the Session-Sender identify the IP address of the Session-Reflector behind the NAT and detect changes in the NAT mapping that could result in sending STAMP packets to the wrong reflector.
The Timestamp Information TLV, type 3, lets the Session-Sender request information about how the reflector took its timestamps. It has four one-octet fields: the source of clock synchronization at the ingress of the reflector, the method by which the ingress obtained the timestamp T2, the source of clock synchronization at the egress, and the method by which the egress obtained the timestamp T3. The registered synchronization sources are NTP, PTP, SSU/BITS, the satellite systems GPS/GLONASS/LORAN-C/BDS/Galileo, and a local free-running clock. The registered timestamping methods are HW Assist, SW Local and Control Plane. The TLV may also carry optional sub-TLVs.
Three optional fields cover the most common extra questions. Padding makes the test packets bigger, which is useful for testing paths that handle large packets. The Location TLV asks the far end what address the packet arrived with, so a sender can spot a NAT or a change of path. The Timestamp Information TLV asks how the far end took its timestamps, so a reader knows how much of the measured delay is clock error.
§4.4Class of Service, Counters and Access Reports
The Class of Service TLV, type 4, has a fixed length of 4 octets. Its DSCP1 field is the Differentiated Services Code Point the Session-Sender intends the reflector to use in the reflected packet, DSCP2 is the value received in the DSCP field at the ingress of the reflector, and the ECN field is the value received in the ECN field at that ingress. The reflector MUST copy the DSCP and ECN values from the IP header of the received packet into the DSCP2 field of the reflected packet. It then uses local policy to decide whether the class of service named by DSCP1 is permitted in its domain: if it is, the reflector sets the DSCP value in the IP header of the reflected packet to that value, and otherwise it keeps the received DSCP value and sets the RP, or Reverse Path, flag to 1. When the Session-Sender sees RP equal to 0 it can save the DSCP and ECN values for analysis of the class of service in the reverse direction; when RP is 1 only the forward direction can be analysed. Re-mapping of class of service can provide multiple services over the same network, but if it is misconfigured it is often hard to diagnose the root cause of excessive packet drops of a higher-level service. The RFC notes that using the CoS TLV in STAMP testing helps to troubleshoot that problem and to verify that DiffServ policies are processing class of service as the configuration requires.
The Direct Measurement TLV, type 5, collects the number of in-profile packets, meaning packets that form a specific data flow, that the Session-Sender and the Session-Reflector have transmitted and received. The definition of an in-profile packet is outside the scope of the document. The TLV has three four-octet counters: the Session-Sender's transmitted count, and the reflector's received and transmitted counts, each of which the reflector fills in. The reflector MUST copy the value from the sender's counter into the reflected packet before transmitting it.
The Access Report TLV, type 6, indicates changes to the access network status. Its ID field identifies the access network, with the value 1 for a 3GPP network and 2 for a non-3GPP network; a TLV with any other value MUST be discarded. Its Return Code field carries the report signal, with the registered values being Network available and Network unavailable. The reflector MUST include the TLV in the reflected packet with the same field values. The Session-Sender MUST arm a retransmission timer after sending a packet that includes this TLV, and disarm it when the reflected packet arrives. If the timer expires first, the Session-Sender MUST retransmit the packet, and this SHOULD be repeated up to four times before the procedure is aborted. The default value of the retransmission timer SHOULD be three seconds, and an implementation MUST provide control of the timer value and the number of retransmissions.
These three fields answer operational questions rather than timing ones. The class of service field checks that a packet is treated the way the operator intended in each direction. The counter field gives the number of matching packets each side saw. The access report field tells the far end that the user's network is up or down, and it is retransmitted a few times until the far end answers.
§4.8The HMAC TLV
The STAMP authenticated mode protects the integrity of data collected in the base packet. STAMP extensions are designed to give valuable information about the condition of a network, and protecting the integrity of that data is also essential. All authenticated STAMP base packets compatible with this specification MUST additionally authenticate the optional TLVs by including the keyed Hashed Message Authentication Code TLV, with the sole exception of when there is only one TLV present and it is the Extra Padding TLV. The HMAC TLV MUST follow all the other TLVs in the packet, except the Extra Padding TLV. If it appears in any other position, the situation MUST be processed as an HMAC verification failure. The HMAC TLV MAY also be used to protect integrity in the unauthenticated mode, and an implementation of STAMP extensions MUST provide controls to enable that.
The TLV has type 8, a length of 16 octets, and a 16-octet HMAC field carrying the digest of the text of all preceding TLVs. STAMP uses HMAC-SHA-256 truncated to 128 bits (RFC 4868), and the considerations about the key that RFC 8762 lists fully apply. Key management and how the HMAC key is distributed are outside the scope of this specification. HMAC is calculated over text that is the concatenation of the Sequence Number field of the base STAMP packet and all preceding TLVs, and the digest is then truncated to 128 bits and written into the HMAC field.
If the HMAC TLV is present in the extended packet, HMAC MUST be verified before any data in the included TLVs is used. If verification by the Session-Reflector fails, the reflector MUST stop processing the received packet, MUST copy the TLVs into the reflected packet, and MUST set the I flag in each copied TLV to 1 before transmitting it. If the Session-Sender receives the reflected packet with the I flag set to 1, it MUST stop processing TLVs in that packet, and if HMAC verification by the Session-Sender fails it MUST also stop processing the TLVs in the reflected packet.
The HMAC TLV is a fingerprint of everything before it, computed with a key both ends share. A reflector that cannot verify the fingerprint copies the fields back with a flag saying the check failed, and the sender then ignores them. The check protects the contents from being altered, but it does not stop an old packet being replayed.
§5IANA Registries
The document creates six subregistries. The STAMP TLV Types subregistry allocates the type numbers, where 1 to 175 need IETF Review, 176 to 239 are First Come First Served, 240 to 251 are for Experimental Use and 252 to 254 are Private Use. This document allocates 1 for Extra Padding, 2 for Location, 3 for Timestamp Information, 4 for Class of Service, 5 for Direct Measurement, 6 for Access Report, 7 for Follow-Up Telemetry and 8 for HMAC.
The STAMP TLV Flags subregistry records the three flags: bit 0 is U, Unrecognized TLV; bit 1 is M, Malformed TLV; and bit 2 is I, Integrity check failed. The STAMP Sub-TLV Types subregistry allocates the sub-TLV numbers used inside the Location TLV: 1 Source MAC Address, 2 Source EUI-48 Address, 3 Source EUI-64 Address, 4 Destination IP Address, 5 Destination IPv4 Address, 6 Destination IPv6 Address, 7 Source IP Address, 8 Source IPv4 Address and 9 Source IPv6 Address.
The STAMP Synchronization Sources subregistry lists where a clock comes from: 1 NTP, 2 PTP, 3 SSU/BITS, 4 GPS/GLONASS/LORAN-C/BDS/Galileo and 5 Local free-running. The STAMP Timestamping Methods subregistry lists how a timestamp was taken: 1 HW Assist, 2 SW Local and 3 Control Plane. The STAMP Return Codes subregistry lists the access report signals: 1 Network available and 2 Network unavailable.
The RFC registers the numbers it uses so that other specifications can extend the same lists without collisions. The TLV type numbers 1 to 8 are the eight optional fields defined here, and the sub-TLV numbers 1 to 9 are the location questions a sender can ask.
- 1Extra Padding — Pads the test packet; recommended when testing with packets larger than the base packet.
- 2Location — Asks the reflector for the addresses, ports and MAC address of the last hop.
- 3Timestamp Information — Asks how the reflector synchronized its clock and took its timestamps.
- 4Class of Service — Carries the DSCP and ECN values seen and asked for, and the reverse path flag.
- 5Direct Measurement — Carries the in-profile packet counters of both ends.
- 6Access Report — Reports whether the access network is available.
- 7Follow-Up Telemetry — Carries the timestamp of the previously reflected packet.
- 8HMAC — Carries the digest of all preceding TLVs, truncated to 128 bits.
§6Security Considerations
This document defines extensions to STAMP and inherits all the security considerations applicable to the base protocol. The HMAC TLV is defined here as well. Although the HMAC TLV protects the integrity of STAMP extensions, it does not protect against a replay attack.
To protect against a malformed TLV, an implementation of a Session-Sender and Session-Reflector MUST check the setting of the M flag and validate the Length field value.
Because the specification defines a mechanism to test DSCP mapping, it inherits all the security considerations discussed in RFC 2474. Monitoring and optional control of DSCP using the CoS TLV may be used across the Internet, so that the Session-Sender and the Session-Reflector are located in domains that use different CoS profiles. It is therefore essential that an operator verify the set of CoS values used in the Session-Reflector's domain. An implementation of a Session-Reflector SHOULD support a local policy to confirm whether the value sent by the Session-Sender can be used as the value of the DSCP field.
The extra fields inherit the security rules of the base protocol, with one gap: the HMAC protects the fields from being changed but does not stop a captured packet being replayed later. A reader of the results also needs to remember that the two ends may sit in networks with different class-of-service settings.