Internet-Draft Probes Attribution May 2023
Vyncke, et al. Expires 26 November 2023 [Page]
Operational Security Capabilities for IP Network Infrastructure
Intended Status:
E. Vyncke
B. Donnet
Université de Liège
J. Iurman
Université de Liège

Attribution of Internet Probes


Active measurements can target either collaborating parties or non-collaborating ones. Sometimes these measurements are viewed as unwelcome or aggressive. This document proposes some simple techniques allowing any party or organization to understand what this unsolicited packet is, what is its purpose, and more importantly who to contact.

About This Document

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Table of Contents

1. Introduction

Active measurements can target either collaborating parties or non-collaborating ones. Such measurements include [LARGE_SCALE] and [RFC7872].

Sending unsolicited probes should obviously be done at a rate low enough to not unduly impact the other parties resources. But even at a low rate, those probes could trigger an alarm that will request some investigation by either the party receiving the probe (i.e., when the probe destination address is one address assigned to the receiving party) or by a third party having some devices where those probes are transiting (e.g., an Internet transit router).

This document suggests some simple techniques to allow any party or organization to understand:

Note: it is expected that only researchers with good intentions will use these techniques, although anyone might use them. This is discussed in Section 7.

2. Probe Description

2.1. Probe Description URI

This document defines a probe description URI as a URI pointing to either:

  • a probe description file (see Section 2.2) as defined in Section 8: "";
  • an email address, e.g., "";
  • a phone number, e.g., "tel:+1-201-555-0123".

2.2. Probe Description File

As defined in Section 8, the probe description file must be made available at "". The probe description file must follow the format defined in section 4 of [RFC9116] and should contain the following fields defined in section 2 of [RFC9116]:

  • Canonical
  • Contact
  • Expires
  • Preferred-Languages

A new field "Description" should also be included to describe the measurement. To match the format defined in section 4 of [RFC9116], this field must be a one line string.

2.2.1. Example

    # Canonical URI (if any)

    # Contact address

    # Validity
    Expires: 2023-12-31T18:37:07z

    # Languages
    Preferred-Languages: en, es, fr

    # Probe/Measurement description
    Description: This is a one-line string description of the
    measurement, with no line break.

3. Out-of-band Probe Attribution

An alternative to URI inclusion is to build a specific URI based on the source address of the probe packet, following [RFC8615]. For example, with a probe source address 2001:db8::dead, the following URI is built:

The built URI must be a reference to the probe description file (see Section 2.2).

As an example, the UK National Cyber Security Centre [NCSC] uses a similar attribution. They scan for vulnerabilities across internet-connected systems in the UK and publish information on their scanning ([NCSC_SCAN_INFO]), providing the address of the webpage in reverse DNS.

4. In-band Probe Attribution

When the measurement allows for it, a probe description URI should be included in the payload of all probes sent. This could be:

The probe description URI must start at the first octet of the payload and must be terminated by an octet of 0x00, i.e., it must be null terminated. If the probe description URI cannot be placed at the beginning of the payload, then it must be preceded by an octet of 0x00. Inserting the probe description URI could obviously bias the measurement itself if the probe packet becomes larger than the path MTU.

Note: the above techniques produce a valid and legitimate packet for all the nodes forwarding the probe, except maybe for a hop-by-hop options header with a PadN option containing the probe description URI. As for the receiver, it may or may not process the packet, depending on where the probe description URI is included (e.g., TCP SYN flag with the probe description URI included in data, destination options header with a PadN option containing the probe description URI). As a consequence, a response may not be received. The choice of the probe description URI location is important and highly depends on the context, which is why multiple possibilities are proposed in this document.

For the record, the in-band probe attribution was used in [I-D.draft-vyncke-v6ops-james].

5. Operational and Technical Considerations

Using either the out-of-band or in-band technique, or even both combined, highly depends on will or context. This section describes the upsides and downsides of each technique, so that probe owners or probe makers can freely decide what works best for their cases.

The advantages of using the out-of-band technique are that the probing measurement is not impacted by the probe attribution but also that it is easy to setup, i.e., by running a web server on a probe device to describe the measurements. Unfortunately, there are some disadvantages too. In some cases, using the out-of-band technique might not be possible due to several conditions: the presence of a NAT, too many endpoints to run a web server on, the probe source IP address cannot be known (e.g., RIPE Atlas [RIPE_ATLAS] probes are sent from IP addresses not owned by the probe owner), dynamic source addresses, etc.

The primary advantage of using the in-band technique is that it covers the cases where the out-of-band technique is not feasible (as described above). The primary disadvantage is that it potentially biases the measurements, since packets with the Probe Description URI might be discarded.

Having both the out-of-band and in-band techniques combined also has a big advantage, i.e., it could be used as an indirect means of "authenticating" the Probe Description URI in the in-band probe, thanks to a correlation with the out-of-band technique (e.g., a reverse DNS lookup). While the out-of-band technique alone is less prone to spoofing, the combination with the in-band technique offers a more complete solution.

6. Ethical Considerations

Executing measurement experiences over the global Internet obviously requires ethical consideration, especially when transit/destination unsolicited parties are involved.

This document proposes a common way to identity the source and the purpose of active probing in order to reduce the potential burden on the unsolicited parties.

But there are other considerations to be taken into account: from the payload content (e.g., is the encoding valid ?) to the transmission rate (see also [IPV6_TOPOLOGY] and [IPV4_TOPOLOGY] for some probing speed impacts). Those considerations are out of scope of this document.

7. Security Considerations

It is expected that only researchers with good intentions will use these techniques, which will simplify and reduce the time to identify probes across the Internet.

This information is provided to identify the source and intent of specific probes, but there is no authentication possible for the inline information. Therefore, a malevolent actor could provide false information while conducting the probes, so that the action is attributed to a third party. In that case, not only this third party would be wrongly accused, but it might also be exposed to unwanted solicitations (e.g., angry emails or phone calls, if the malevolent actor used someone else's email address or phone number). As a consequence, the recipient of this information cannot trust it without confirmation. If a recipient cannot confirm the information or does not wish to do so, it should treat the flows as if there were no attribution.

8. IANA Considerations

The "Well-Known URIs" registry should be updated with the following additional values (using the template from [RFC8615]):

9. References

9.1. Normative References

Conta, A., Deering, S., and M. Gupta, Ed., "Internet Control Message Protocol (ICMPv6) for the Internet Protocol Version 6 (IPv6) Specification", STD 89, RFC 4443, DOI 10.17487/RFC4443, , <>.
Postel, J., "User Datagram Protocol", STD 6, RFC 768, DOI 10.17487/RFC0768, , <>.
Postel, J., "Internet Control Message Protocol", STD 5, RFC 792, DOI 10.17487/RFC0792, , <>.
Deering, S. and R. Hinden, "Internet Protocol, Version 6 (IPv6) Specification", STD 86, RFC 8200, DOI 10.17487/RFC8200, , <>.
Nottingham, M., "Well-Known Uniform Resource Identifiers (URIs)", RFC 8615, DOI 10.17487/RFC8615, , <>.
Foudil, E. and Y. Shafranovich, "A File Format to Aid in Security Vulnerability Disclosure", RFC 9116, DOI 10.17487/RFC9116, , <>.
Eddy, W., Ed., "Transmission Control Protocol (TCP)", STD 7, RFC 9293, DOI 10.17487/RFC9293, , <>.

9.2. Informative References

Vyncke, E., Léas, R., and J. Iurman, "Just Another Measurement of Extension header Survivability (JAMES)", Work in Progress, Internet-Draft, draft-vyncke-v6ops-james-03, , <>.
Beverly, R., "Yarrp'ing the Internet Randomized High-Speed Active Topology Discovery", DOI 10.1145/2987443.2987479, , <>.
Beverly, R., Durairajan, R., Plonka, D., and J. P. Rohrer, "In the IP of the Beholder Strategies for Active IPv6 Topology Discovery", DOI 10.1145/3278532.3278559, , <>.
Donnet, B., Raoult, P., Friedman, T., and M. Crovella, "Efficient Algorithms for Large-Scale Topology Discovery", DOI 10.1145/1071690.1064256, , <>.
"The National Cyber Security Centre", n.d., <>.
"NCSC Scanning information", n.d., <>.
Davies, E., Krishnan, S., and P. Savola, "IPv6 Transition/Co-existence Security Considerations", RFC 4942, DOI 10.17487/RFC4942, , <>.
Gont, F., Linkova, J., Chown, T., and W. Liu, "Observations on the Dropping of Packets with IPv6 Extension Headers in the Real World", RFC 7872, DOI 10.17487/RFC7872, , <>.
"RIPE Atlas", n.d., <>.


The authors would like to thank Alain Fiocco, Fernando Gont, Ted Hardie, Mehdi Kouhen, and Mark Townsley for helpful discussions as well as Raphael Leas for an early implementation.

The authors would also like to gracefully acknowledge useful review and comments received from Jen Linkova, Prapanch Ramamoorthy, Warren Kumari, and Andrew Shaw.

Authors' Addresses

Éric Vyncke
De Kleetlaan 64
1831 Diegem
Benoît Donnet
Université de Liège
Justin Iurman
Université de Liège