IPv6 Hop-by-hop and Destination Options Forwarding In Routers

Status of This Memo

This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79.¶

Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet-Drafts is at https://datatracker.ietf.org/drafts/current/.¶

Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress."¶

This Internet-Draft will expire on 5 September 2024.¶

Copyright Notice

Copyright (c) 2024 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 Revised BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Revised BSD License.¶

Table of Contents

1. Introduction

It has become well known that packets containing IPv6 [RFC8200] Extension Headers (EHs), especially Hop-by-Hop Options, are often dropped when traversing the Internet. However, the question still remains as to what are the primary contributors to these packet drops and under what circumstances are the packets dropped. Some of the potential culprits include ACLs, firewalls, routers, load balancers, and more. It also is not known whether these packets are dropped intentionally (e.g., ACLs) or unintentionally (e.g., firmware bugs).¶

This document describes the research conducted and results of isolating routers to better understand what role they may play, if any, in the dropping of EHs. Specifically, this research is aiming to understand whether or not router implementations may be the cause of dropped packets containing EHs.¶

2. Layer 3 Topology

The layer 3 topology used for these experiments can be seen below in Figure 1. Layer 3 is specifically noted because layer 2 switches exist in the topology as well as some components being virtualized, however, this is not expected to have an effect on the traversal of packets containing EHs.¶

+--------+     +--------+     +--------+
| Client |-----| Router |-----| Server |
+--------+     +--------+     +--------+

Both client and server are virtual machines running Ubuntu 22.04 and are configured to inject EHs into all egress packets. Additionally, the server has an out-of-the-box installation of an apache2 web server. Details of the routers used can be found below in Section 3.¶

3. Routers Under Test (RUTs)

Six routers in total were tested and are comprised of three major router manufacturers. Of the six routers, five are physical and the sixth is virtual. Due to confidentiality requirements, the specific manufacturers and models of the routers tested cannot be disclosed, therefore, the routers will be referred to with a numerical value from here on.¶

4. Experiments

For all experiments, both the client and server are configured to inject varying EHs into all egress packets. A single HTTP request is then made from the client to the server and it was observed that the client received an HTTP reply containing the expected EHs. This indicates that the RUT properly forwarded all packets associated with both the HTTP request and reply that contained EHs without dropping the packets or stripping the EHs from them [I-D.herbert-eh-inflight-removal]. To execute the HTTP request, the curl utility was used.¶

5. Results and Findings

The following section reports on the findings of these experiments. Tables in this section will denote whether the router properly forwarded packets containing the EH(s) or not. Scenarios in which the router forwards the packets will be denoted with a check mark (✓) and scenarios where the router does not forward the packets will be denoted with an X (X).¶

6. Conclusion

Even though this research was conducted on a relatively small sample size of manufacturers and routers, the results indicate that router implementations in general are likely not the culprits for dropping packets containing HBH or DO EHs. One router did face limitations when processing larger EHs, however, EH chains of that size may not be practical when used in a real-world network and therefore may not be a concern. The most surprising finding was that a layer 2 switch was the cause of dropped packets containing 512-byte HBH options.¶

7. Future Work

8. Security Considerations

This document has no security considerations.¶

9. Privacy Considerations

This document has no privacy considerations.¶

10. IANA Considerations

This document has no IANA actions.¶

Acknowledgments

The author would like to acknowledge and thank the following individuals. Nalini Elkins and Michael Ackermann for their guidance and support throughout this research. Balajinaidu V, Amogh Umesh, and Chinmaya Sharma for developing and providing access to their PDM DO implementation. Justin Iurman for developing and providing access to their IPv6 Extension Headers Injection with eBPF project. Michayla Newcombe and Ben Patton for their review and feedback of this document.¶

Author's Address