Internet-Draft JAMES March 2022
Vyncke, et al. Expires 21 September 2022 [Page]
IPv6 Operations
Intended Status:
É. Vyncke
R. Léas
Université de Liège
J. Iurman
Université de Liège

Just Another Measurement of Extension header Survivability (JAMES)


In 2016, RFC7872 has measured the drop of packets with IPv6 extension headers. This document presents a slightly different methodology with more recent results. It is still work in progress.

About This Document

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Table of Contents

1. Introduction

In 2016, [RFC7872] has measured the drop of packets with IPv6 extension headers on their transit over the global Internet. This document presents a slightly different methodology with more recent results. Since then, [I-D.draft-ietf-opsec-ipv6-eh-filtering] has provided some recommendations for filtering transit traffic, so there may be some changes in providers policies.

It is still work in progress, but the authors wanted to present some results at IETF-113 (March 2022). The code is open source and is available at [GITHUB].

2. Methodology

In a first phase, the measurement is done between collaborating IPv6 nodes, a.k.a. vantage points, spread over the Internet and multiple Autonomous Systems (ASs). As seen in Section 3.2, the source/destination/transit ASs include some "tier-1" providers per [TIER1], so, they are probably representative of the global Internet core.

Relying on collaborating nodes has some benefits:

Future phases will send probes to non-collaborating nodes with a much reduced probing speed. The destination will include [ALEXA] top-n websites, popular CDN, as well as random prefix from the IPv6 global routing table. A revision of this IETF draft will describe those experiments.

3. Measurements

3.1. Vantage Points

Several servers were used worldwide (albeit missing Africa and China as the authors were unable to find IPv6 servers in these regions). Table 1 lists all the vantage points together with their AS number and country.

Table 1: All vantage AS
ASN AS Name Country code Location
7195 Edge Uno AG Buenos Aires
12414 NL-SOLCON SOLCON NL Amsterdam
14061 Digital Ocean CA Toronto, ON
14061 Digital Ocean USA New York City, NY
14601 Digital Ocean DE Francfort
14601 Digital Ocean IN Bangalore
14601 Digital Ocean SG Singapore
16276 OVH AU Sydney
16276 OVH PL Warsaw
44684 Mythic Beasts UK Cambridge
47853 Hostinger US Ashville, NC
198644 GO6 SI Ljubljana

3.2. Tested Autonomous Systems

During first phase (traffic among fully-meshed collaborative nodes), Table 2 show the ASs for which our probes have collected data.

Table 2: All AS (source/destination/transit)
AS Number AS Description Comment
174 COGENT-174, US Tier-1
1299 TWELVE99 Twelve99, Telia Carrier, SE Tier-1
3320 DTAG Internet service provider operations, DE Tier-1
3356 LEVEL3, US Tier-1
4637 ASN-TELSTRA-GLOBAL Telstra Global, HK Regional Tier
4755 TATACOMM-AS TATA Communications formerly VSNL is Leading ISP, IN  
5603 SIOL-NET Telekom Slovenije d.d., SI  
6453 Tata Communication Tier-1
6939 HURRICANE, US Regional Tier
8447 A1TELEKOM-AT A1 Telekom Austria AG, AT  
9498 BBIL-AP BHARTI Airtel Ltd., IN  
16276 OVH, FR  
21283 A1SI-AS A1 Slovenija, SI  
34779 T-2-AS AS set propagated by T-2 d.o.o., SI  
44684 MYTHIC Mythic Beasts Ltd, GB  
198644 GO6, SI  

The table attributes some tier qualification to some ASs based on the Wikipedia page [TIER1], but there is no common way to decide who is a tier-1. Based on some CAIDA research, all the above (except GO6, which is a stub network) are transit providers.

While this document lists some operators, the intent is not to build a wall of fame or a wall of shame but more to get an idea about which kind of providers drop packets with extension headers and how widespread the drop policy is enforced and where, i.e., in the access provider or in the core of the Internet.

3.2.1. Drop attribution to AS

Comparing the traceroutes with and without extension headers allows the attribution of a packet drop to one AS. But, this is not an easy task as inter-AS links often use IPv6 address of only one AS (if not using link-local per [RFC7704]). This document uses the following algorithm to attribute the drop to one AS for packet sourced in one AS and then having a path traversing AS#foo just before AS#bar:

  • if the packet drop happens at the first router (i.e., hop limit == 1 does not trigger an ICMP hop-limit exceeded), then the drop is assumed to this AS as it is probably an ingress filter on the first router (i.e., the hosting provider in most of the cases - except if collocated with an IXP).
  • if the packet drop happens in AS#foo after one or more hop(s) in AS#bar, then the drop is assumed to be in AS#foo ingress filter on a router with an interface address in AS#foo
  • if the packet drop happens in AS#bar after one or more hop(s) in AS#bar before going to AS#foo, then the drop is assumed to be in AS#foo ingress filter on a router with an interface address in AS#bar

In several cases, the above algorithm was not possible (e.g., some intermediate routers do not generate an ICMP unreachable hop limit exceeded even in the absence of any extension headers), then the drop is not attributed. Please also note that the goal of this document is not to 'point fingers to operators' but more to evaluate the potential impact. I.e., a tier-1 provider dropping packets with extension headers has a much bigger impact on the Internet traffic than an access provider.

Future revision of this document will use the work of [MLAT_PEERING].

3.3. Tested Extension Headers

In the first phase among collaborating vantage points, packets always contained either a UDP payload or a TCP payload, the latter is sent with only the SYN flag set and with data as permitted by section 3.4 of [RFC793] (2nd paragraph). A usual traceroute is done with only the UDP/TCP payload without any extension header with varying hop-limit in order to learn the traversed routers and ASs. Then, several UDP/TCP probes are sent with a set of extension headers:

  • hop-by-hop and destination options header containing:

    • one PadN option for an extension header length of 8 octets,
    • one unknown option with the "discard" bits for an extension header length of 8 octets,
    • multiple PadN options for an extension header length of 256 octets,
    • one unknown option (two sets with "discard" and "skip" bits) for the destination options header length of 16, 32, 64, and 128 octets,
    • one unknown option (two sets with "discard" and "skip" bits) for an extension header length of 256 and 512 octets.
  • routing header with routing types from 0 to 6 inclusive;
  • atomic fragment header (i.e., M-flag = 0 and offset = 0) of varying frame length 512, 1280, and 1500 octets;
  • non-atomic first fragment header (i.e., M-flag = 1 and offset = 0) of varying frame length 512, 1280, and 1500 octets;
  • authentication header with dummy SPI followed by UDP/TCP header and a 38 octets payload.

In the above, length is the length of the extension header itself except for the fragmentation header where the length is the IP packet length (i.e., including the IPv6, and TCP/UDP headers + payload).

For hop-by-hop and destination options headers, when required multiple PadN options were used in order to bypass some Linux kernels that consider a PadN larger than 8 bytes is an attack, see section 5.3 of [BCP220], even if multiple PadN options violates section of [RFC4942].

In addition to the above extension headers, other probes were sent with next header field of IPv6 header set to:

  • 59, which is "no next header", especially whether extra octets after the no next header as section 4.7 [RFC8200] requires that "those octets must be ignored and passed on unchanged if the packet is forwarded";
  • 143, which is Ethernet payload (see section 10.1 of [RFC8986]).

4. Results

This section presents the current results out of phase 1 (collaborating vantage points) testing. About 4860 experiments were run, one experiment being defined by sending packets between 2 vantage points with hop-limit varying from 1 to the number of hops between the two vantage points and for all the extension headers described in Section 3.3.

4.1. Routing Header

Table 3 lists all routing header types and the percentage of experiments that were successful, i.e., packets with routing header reaching their destination:

Table 3: Per Routing Header Types Transmission
Routing Header Type %-age of packets reaching destination
0 80.9%
1 99.5%
2 99.5%
3 99.5%
4 69.0%
5 99.5%
6 99.3%

Table 4 lists the few ASs that drop packets with the routing header type 0 (the original source routing header, which is now deprecated).

Table 4: AS Dropping Routing Header Type 0
AS Number AS description

It is possibly due to a strict implementation of [RFC5095] but it is expected that no packet with routing header type 0 would be transmitted anymore. So, this is not surprising.

Table 5 lists the few ASs that drop packets with the routing header type 4 (Segment Routing Header [RFC8754]).

Table 5: AS Dropping Routing Header Type 0
AS Number AS description
16276 OVH, FR

This drop of SRH was to be expected as SRv6 is specified to run only in a limited domain.

Other routing header types (1 == deprecated NIMROD [RFC1753], 2 == mobile IPv6 [RFC6275], 3 == RPL [RFC6554], and even 5 == CRH-16 and 6 == CRH-32[I-D.draft-bonica-6man-comp-rtg-hdr]) can be transmitted over the global Internet without being dropped (assuming that the 0.5% of dropped packets are within the measurement error).

4.2. Hop-by-Hop Options Header

Many ASs drop packets containing either hop-by-hop options headers per Table 6 below:

Table 6: Hop-by-hop Transmission
Option Type Length %-age of packets reaching destination
Skip 8 5.8%
Discard 8 0.0%
Skip one large PadN 256 1.9%
Skip multiple PadN 256 0.0%
Discard 256 0.0%
Skip 512 1.9%
Discard 512 0.0%

It appears that hop-by-hop options headers cannot reliably traverse the global Internet; only small headers with 'skipable' options have some chances. If the unknown hop-by-hop option has the 'discard' bits, it is dropped per specification.

4.3. Destination Options Header

Many ASs drop packets containing destination options headers per Table 7:

Table 7: Hop-by-hop Transmission
Length Multiple PadN %-age of packets reaching destination
8 No 99.3%
16 No 99.3%
32 No 93.3%
64 No 41.6%
128 No 4.5%
256 No 2.6%
256 Yes 2.6%
512 No 2.6%

The measurement did not find any impact of the discard/skip bits in the destination headers options, probably because the routers do not look inside the extension headers into the options. The use of a single large PadN or multiple 8-octet PadN options does not influence the result.

The size of the destination options header has a major impact on the drop probability. It appears that extension header larger than 16 octets already causes major drops. It may be because the 40 octets of the IPv6 header + the 16 octets of the extension header (total 56 octets) is still below some router hardware lookup mechanisms while the next measured size (extension header size of 64 octets for a total of 104 octets) is beyond the hardware limit and some AS has a policy to drop packets where the TCP/UDP ports are unknown...

4.4. Fragmentation Header

The propagation of two kinds of fragmentation headers was analysed: atomic fragment (offset == 0 and M-flag == 0) and plain first fragment (offset == 0 and M-flag == 1). The Table 8 displays the propagation differences.

Table 8: IPv6 Fragments Transmission
M-flag %-age of packets reaching destination
0 (atomic) 70.2%
1 99.0%

The size of the overall IP packets (512, 1280, and 1500 octets) does not have any impact on the propagation.

4.5. No extension headers drop at all

Table 9 lists some ASs that do not drop transit traffic (except for routing header type 0) and follow the recommendations of [I-D.draft-ietf-opsec-ipv6-eh-filtering]. This list includes tier-1 transit providers (using the "regional" tag per [TIER1]):

Table 9: ASs Not Dropping Packets with Extension Headers
AS Number AS Description Comment
4637 ASN-TELSTRA-GLOBAL Telstra Global, HK Regional Tier
4755 TATACOMM-AS TATA Communications formerly VSNL is Leading ISP, IN  
21283 A1SI-AS A1 Slovenija, SI  

Some ASs also drop only large (more than 8 octets) destination options headers, see Table 10:

Table 10: ASs Only Dropping Packets with Large Destination Options Headers
AS Number AS Description Largest Forwarded Dest.Opt. Size
6453 Tata Communication   8
1299 TWELVE99 Twelve99, Telia Carrier, SE 8
174 COGENT-174, US 8

4.6. Special Next Headers

Measurements also include two protocol numbers that are mainly new use of IPv6. Table 11 indicates the percentage of packets reaching the destination.

Table 11: Transmission of Special IP Protocols
Next Header %-age of packets reaching destination
NoNextHeader (59) 99.7%
Ethernet (143) 99.2%

The above indicates that those IP protocols can be transmitted over the global Internet without being dropped (assuming that the 0.3-0.8% of dropped packets are within the measurement error).

5. Summary of the collaborating parties measurements

While the analysis has areas of improvement (geographical distribution and impact on latency), it appears that:

Of course, the next phase of measurement with non-collaborating parties will probably give another view.

6. Security Considerations

While active probing of the Internet may be considered as an attack, this measurement was done among collaborating parties and using the probe attribution technique described in [I-D.draft-vyncke-opsec-probe-attribution] to allow external parties to identify the source of the probes if required.

7. IANA Considerations

This document has no IANA actions.

8. References

8.1. Normative References

Postel, J., "Transmission Control Protocol", STD 7, RFC 793, DOI 10.17487/RFC0793, , <>.
Deering, S. and R. Hinden, "Internet Protocol, Version 6 (IPv6) Specification", STD 86, RFC 8200, DOI 10.17487/RFC8200, , <>.

8.2. Informative References

"The top 500 sites on the web", n.d., <>.
Chown, T., Loughney, J., and T. Winters, "IPv6 Node Requirements", BCP 220, RFC 8504, .
Léas, R., "james", n.d., <>.
Bonica, R., Kamite, Y., Alston, A., Henriques, D., and L. Jalil, "The IPv6 Compact Routing Header (CRH)", Work in Progress, Internet-Draft, draft-bonica-6man-comp-rtg-hdr-27, , <>.
Harris, G. and M. C. Richardson, "PCAP Capture File Format", Work in Progress, Internet-Draft, draft-ietf-opsawg-pcap-00, , <>.
Gont, F. and W. (. Liu, "Recommendations on the Filtering of IPv6 Packets Containing IPv6 Extension Headers at Transit Routers", Work in Progress, Internet-Draft, draft-ietf-opsec-ipv6-eh-filtering-08, , <>.
Vyncke, É., Donnet, B., and J. Iurman, "Attribution of Internet Probes", Work in Progress, Internet-Draft, draft-vyncke-opsec-probe-attribution-01, , <>.
Giotsas, V., Zhou, S., Luckie, M., and K. Claffy, "Inferring Multilateral Peering", DOI 10.1145/2535372.2535390, , <>.
Chiappa, N., "IPng Technical Requirements Of the Nimrod Routing and Addressing Architecture", RFC 1753, DOI 10.17487/RFC1753, , <>.
Davies, E., Krishnan, S., and P. Savola, "IPv6 Transition/Co-existence Security Considerations", RFC 4942, DOI 10.17487/RFC4942, , <>.
Abley, J., Savola, P., and G. Neville-Neil, "Deprecation of Type 0 Routing Headers in IPv6", RFC 5095, DOI 10.17487/RFC5095, , <>.
Perkins, C., Ed., Johnson, D., and J. Arkko, "Mobility Support in IPv6", RFC 6275, DOI 10.17487/RFC6275, , <>.
Hui, J., Vasseur, JP., Culler, D., and V. Manral, "An IPv6 Routing Header for Source Routes with the Routing Protocol for Low-Power and Lossy Networks (RPL)", RFC 6554, DOI 10.17487/RFC6554, , <>.
Crocker, D. and N. Clark, "An IETF with Much Diversity and Professional Conduct", RFC 7704, DOI 10.17487/RFC7704, , <>.
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, , <>.
Filsfils, C., Ed., Dukes, D., Ed., Previdi, S., Leddy, J., Matsushima, S., and D. Voyer, "IPv6 Segment Routing Header (SRH)", RFC 8754, DOI 10.17487/RFC8754, , <>.
Filsfils, C., Ed., Camarillo, P., Ed., Leddy, J., Voyer, D., Matsushima, S., and Z. Li, "Segment Routing over IPv6 (SRv6) Network Programming", RFC 8986, DOI 10.17487/RFC8986, , <>.
"Tier 1 network", n.d., <>.


The authors want to thank Sander Steffann and Jan Zorz for allowing the free use of their labs. Other thanks to Fernando Gont who indicated a nice IPv6 hosting provider in South America.

Special thanks as well to Professor Benoit Donnet for his support and advices. This document would not have existed without his support.

Authors' Addresses

Éric Vyncke
De Kleetlaan 64
1831 Diegem
Raphaël Léas
Université de Liège
Justin Iurman
Université de Liège
Institut Montefiore B28
Allée de la Découverte 10
4000 Liège