



Internet Engineering Task Force (IETF)                           R. Bush
Request for Comments: 9324               IIJ Research Lab & Arrcus, Inc.
Updates: 8481                                                   K. Patel
Category: Standards Track                                   Arrcus, Inc.
ISSN: 2070-1721                                                 P. Smith
                                        PFS Internet Development Pty Ltd
                                                                M. Tinka
                                                                  SEACOM
                                                           December 2022


 Policy Based on the Resource Public Key Infrastructure (RPKI) without
                             Route Refresh

Abstract

   A BGP speaker performing policy based on the Resource Public Key
   Infrastructure (RPKI) should not issue route refresh to its neighbors
   because it has received new RPKI data.  This document updates RFC
   8481 by describing how to avoid doing so by either keeping a full
   Adj-RIB-In or saving paths dropped due to ROV (Route Origin
   Validation) so they may be reevaluated with respect to new RPKI data.

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/rfc9324.

Copyright Notice

   Copyright (c) 2022 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
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   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
     1.1.  Requirements Language
   2.  Related Work
   3.  ROV Experience
   4.  Keeping Partial Adj-RIB-In Data
   5.  Operational Recommendations
   6.  Security Considerations
   7.  IANA Considerations
   8.  References
     8.1.  Normative References
     8.2.  Informative References
   Acknowledgements
   Authors' Addresses

1.  Introduction

   Memory constraints in early BGP speakers caused classic BGP
   implementations [RFC4271] to not keep a full Adj-RIB-In (Section 1.1
   of [RFC4271]).  When doing RPKI-based Route Origin Validation (ROV)
   [RFC6811] [RFC8481] and similar RPKI-based policy, if such a BGP
   speaker receives new RPKI data, it might not have kept paths
   previously marked as Invalid, etc.  Such an implementation must then
   request a route refresh [RFC2918] [RFC7313] from its neighbors to
   recover the paths that might be covered by these new RPKI data.  This
   will be perceived as rude by those neighbors as it passes a serious
   resource burden on to them.  This document recommends implementations
   keep and mark paths affected by RPKI-based policy, so route refresh
   is no longer needed.

1.1.  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.

2.  Related Work

   It is assumed that the reader understands BGP [RFC4271], route
   refresh [RFC7313], the RPKI [RFC6480], Route Origin Authorizations
   (ROAs) [RFC6482], the Resource Public Key Infrastructure (RPKI) to
   Router Protocol [RPKI-ROUTER-PROT-v2], RPKI-Based Prefix Validation
   [RFC6811], and Origin Validation Clarifications [RFC8481].

   Note that the term "RPKI-based Route Origin Validation" in this
   document means the same as the term "Prefix Origin Validation" used
   in [RFC6811].

3.  ROV Experience

   As Route Origin Validation dropping Invalids has deployed, some BGP
   speaker implementations have been found that, when receiving new RPKI
   data (Validated ROA Payloads (VRPs) [RPKI-ROUTER-PROT-v2]), issue a
   BGP route refresh [RFC7313] to all sending BGP peers so that they can
   reevaluate the received paths against the new data.

   In actual deployment, this has been found to be very destructive,
   transferring a serious resource burden to the unsuspecting peers.  In
   reaction, RPKI-based Route Origin Validation (ROV) has been turned
   off.  There have been actual de-peerings.

   As RPKI registration and ROA creation have steadily increased, this
   problem has increased, not just proportionally, but on the order of
   the in-degree of ROV implementing BGP speakers.  As Autonomous System
   Provider Authorization (ASPA) [AS_PATH-VER] becomes used, the problem
   will increase.

   Other mechanisms, such as automated policy provisioning, which have
   flux rates similar to ROV (i.e., on the order of minutes), could very
   well cause similar problems.

   Therefore, this document updates [RFC8481] by describing how to avoid
   this problem.

4.  Keeping Partial Adj-RIB-In Data

   If new RPKI data arrive that cause operator policy to invalidate the
   best route and the BGP speaker did not keep the dropped routes, then
   the BGP speaker would issue a route refresh, which this feature aims
   to prevent.

   A route that is dropped by operator policy due to ROV is, by nature,
   considered ineligible to compete for the best route and MUST be kept
   in the Adj-RIB-In for potential future evaluation.

   Ameliorating the route refresh problem by keeping a full Adj-RIB-In
   can be a problem for resource-constrained BGP speakers.  In reality,
   only some data need be retained.  If an implementation chooses not to
   retain the full Adj-RIB-In, it MUST retain at least routes dropped
   due to ROV for potential future evaluation.

   As storing these routes could cause problems in resource-constrained
   devices, there MUST be a global operation, CLI, YANG, or other
   mechanism that allows the operator to enable this feature and store
   the dropped routes.  Such an operator control MUST NOT be per peer,
   as this could cause inconsistent behavior.

   As a side note, policy that may drop routes due to RPKI-based checks
   such as ROV (and ASPA, BGPsec [RFC8205], etc., in the future) MUST be
   run and the dropped routes saved per this section, before non-RPKI
   policies are run, as the latter may change path attributes.

5.  Operational Recommendations

   Operators deploying ROV and/or other RPKI-based policies should
   ensure that the BGP speaker implementation is not causing route
   refresh requests to neighbors.

   BGP speakers MUST either keep the full Adj-RIB-In or implement the
   specification in Section 4.  Conformance to this behavior is an
   additional, mandatory capability for BGP speakers performing ROV.

   If the BGP speaker does not implement these recommendations, the
   operator should enable the vendor's control to keep the full Adj-RIB-
   In, sometimes referred to as "soft reconfiguration inbound".  The
   operator should then measure to ensure that there are no unnecessary
   route refresh requests sent to neighbors.

   If the BGP speaker's equipment has insufficient resources to support
   either of the two proposed options (keeping a full AdjRibIn or at
   least the dropped routes), the equipment SHOULD either be replaced
   with capable equipment or SHOULD NOT be used for ROV.

   The configuration setting in Section 4 should only be used in very
   well-known and controlled circumstances where the scaling issues are
   well understood and anticipated.

   Operators using the specification in Section 4 should be aware that a
   misconfigured neighbor might erroneously send a massive number of
   paths, thus consuming a lot of memory.  Hence, pre-policy filtering
   such as described in [MAXPREFIX-INBOUND] could be used to reduce this
   exposure.

   If route refresh has been issued toward more than one peer, the order
   of receipt of the refresh data can cause churn in both best route
   selection and outbound signaling.

   Internet Exchange Points (IXPs) that provide route servers [RFC7947]
   should be aware that some members could be causing an undue route
   refresh load on the route servers and take appropriate administrative
   and/or technical measures.  IXPs using BGP speakers as route servers
   should ensure that they are not generating excessive route refresh
   requests.

6.  Security Considerations

   This document describes a denial of service that Route Origin
   Validation or other RPKI policy may place on a BGP neighbor and
   describes how it may be ameliorated.

   Otherwise, this document adds no additional security considerations
   to those already described by the referenced documents.

7.  IANA Considerations

   This document has no IANA actions.

8.  References

8.1.  Normative References

   [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>.

   [RFC2918]  Chen, E., "Route Refresh Capability for BGP-4", RFC 2918,
              DOI 10.17487/RFC2918, September 2000,
              <https://www.rfc-editor.org/info/rfc2918>.

   [RFC4271]  Rekhter, Y., Ed., Li, T., Ed., and S. Hares, Ed., "A
              Border Gateway Protocol 4 (BGP-4)", RFC 4271,
              DOI 10.17487/RFC4271, January 2006,
              <https://www.rfc-editor.org/info/rfc4271>.

   [RFC6811]  Mohapatra, P., Scudder, J., Ward, D., Bush, R., and R.
              Austein, "BGP Prefix Origin Validation", RFC 6811,
              DOI 10.17487/RFC6811, January 2013,
              <https://www.rfc-editor.org/info/rfc6811>.

   [RFC7313]  Patel, K., Chen, E., and B. Venkatachalapathy, "Enhanced
              Route Refresh Capability for BGP-4", RFC 7313,
              DOI 10.17487/RFC7313, July 2014,
              <https://www.rfc-editor.org/info/rfc7313>.

   [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>.

   [RFC8481]  Bush, R., "Clarifications to BGP Origin Validation Based
              on Resource Public Key Infrastructure (RPKI)", RFC 8481,
              DOI 10.17487/RFC8481, September 2018,
              <https://www.rfc-editor.org/info/rfc8481>.

8.2.  Informative References

   [AS_PATH-VER]
              Azimov, A., Bogomazov, E., Bush, R., Patel, K., Snijders,
              J., and K. Sriram, "BGP AS_PATH Verification Based on
              Resource Public Key Infrastructure (RPKI) Autonomous
              System Provider Authorization (ASPA) Objects", Work in
              Progress, Internet-Draft, draft-ietf-sidrops-aspa-
              verification-11, 24 October 2022,
              <https://datatracker.ietf.org/doc/html/draft-ietf-sidrops-
              aspa-verification-11>.

   [MAXPREFIX-INBOUND]
              Aelmans, M., Stucchi, M., and J. Snijders, "BGP Maximum
              Prefix Limits Inbound", Work in Progress, Internet-Draft,
              draft-sas-idr-maxprefix-inbound-04, 19 January 2022,
              <https://datatracker.ietf.org/doc/html/draft-sas-idr-
              maxprefix-inbound-04>.

   [RFC6480]  Lepinski, M. and S. Kent, "An Infrastructure to Support
              Secure Internet Routing", RFC 6480, DOI 10.17487/RFC6480,
              February 2012, <https://www.rfc-editor.org/info/rfc6480>.

   [RFC6482]  Lepinski, M., Kent, S., and D. Kong, "A Profile for Route
              Origin Authorizations (ROAs)", RFC 6482,
              DOI 10.17487/RFC6482, February 2012,
              <https://www.rfc-editor.org/info/rfc6482>.

   [RFC7947]  Jasinska, E., Hilliard, N., Raszuk, R., and N. Bakker,
              "Internet Exchange BGP Route Server", RFC 7947,
              DOI 10.17487/RFC7947, September 2016,
              <https://www.rfc-editor.org/info/rfc7947>.

   [RFC8205]  Lepinski, M., Ed. and K. Sriram, Ed., "BGPsec Protocol
              Specification", RFC 8205, DOI 10.17487/RFC8205, September
              2017, <https://www.rfc-editor.org/info/rfc8205>.

   [RPKI-ROUTER-PROT-v2]
              Bush, R. and R. Austein, "The Resource Public Key
              Infrastructure (RPKI) to Router Protocol, Version 2", Work
              in Progress, Internet-Draft, draft-ietf-sidrops-8210bis-
              10, 16 June 2022, <https://datatracker.ietf.org/doc/html/
              draft-ietf-sidrops-8210bis-10>.

Acknowledgements

   The authors wish to thank Alvaro Retana, Ben Maddison, Derek Yeung,
   John Heasley, John Scudder, Matthias Waehlisch, Nick Hilliard, Saku
   Ytti, and Ties de Kock.

Authors' Addresses

   Randy Bush
   IIJ Research Lab & Arrcus, Inc.
   1856 SW Edgewood Dr
   Portland, OR 97210
   United States of America
   Email: randy@psg.com


   Keyur Patel
   Arrcus, Inc.
   2077 Gateway Place, Suite #400
   San Jose, CA 95119
   United States of America
   Email: keyur@arrcus.com


   Philip Smith
   PFS Internet Development Pty Ltd
   PO Box 1908
   Milton QLD 4064
   Australia
   Email: pfsinoz@gmail.com


   Mark Tinka
   SEACOM
   Building 7, Design Quarter District
   Leslie Avenue, Magaliessig
   Fourways, Gauteng
   2196
   South Africa
   Email: mark@tinka.africa
