Network Working Group T. King Internet-Draft C. Dietzel Intended status: Standards Track D. Kopp Expires: January 24, 2020 DE-CIX A. Lambrianidis AMS-IX July 23, 2019 Signaling Prefix Origin Validation Results from an RPKI Origin Validating BGP Speaker to BGP Peers draft-ietf-sidrops-validating-bgp-speaker-03 Abstract This document describes the use of BGP large communities, as well as its usage, to signal prefix origin validation results from an RPKI Origin validating BGP speaker to other BGP peers. Upon reception of prefix origin validation results, peers can use this information in their local routing decision process. 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. 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 January 24, 2020. King, et al. Expires January 24, 2020 [Page 1] Internet-DraSignaling Prefix Origin Validation Results from a July 2019 Copyright Notice Copyright (c) 2019 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 2. EBGP Prefix Origin Validation Large Community . . . . . . . . 3 3. BGP Prefix Origin Validation State Utilized at Validating Peers . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 4. Signaling Prefix Origin Validation Results from a Validating Peer to Peers . . . . . . . . . . . . . . . . . . . . . . . . 4 5. Operational Recommendations . . . . . . . . . . . . . . . . . 5 5.1. Local Routing Decision Process . . . . . . . . . . . . . 5 5.2. Validating Peers Receiving the EBGP Prefix Origin Validation State Large Community . . . . . . . . . . . . 5 5.3. Information about Validity of a BGP Prefix Origin Not Available at a Validating Peer . . . . . . . . . . . . . 6 5.4. Error Handling at Peers . . . . . . . . . . . . . . . . . 6 6. Security Considerations . . . . . . . . . . . . . . . . . . . 6 7. References . . . . . . . . . . . . . . . . . . . . . . . . . 6 7.1. Normative References . . . . . . . . . . . . . . . . . . 7 7.2. Informative References . . . . . . . . . . . . . . . . . 7 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 7 1. Introduction RPKI-based prefix origin validation [RFC6480] can be a significant operational burden for BGP peers to implement and adopt. To facilitate acceptance and usage of prefix origin validation and ultimately increase the security of the Internet routing system, Autonomous Systems may provide RPKI-based prefix origin validation at certain vantage points. The result of this prefix origin validation is signaled to peers by using the EBGP Prefix Origin Validation State Large Community as introduced in this document. King, et al. Expires January 24, 2020 [Page 2] Internet-DraSignaling Prefix Origin Validation Results from a July 2019 Peers receiving a prefix origin validation result from the validating EBGP peer can use this information in their local routing decision process for acceptance, rejection, preference, or other traffic engineering purposes of a particular route. 2. EBGP Prefix Origin Validation Large Community The origin validation state large community 12-octet function specific large community [RFC8092] with the following encoding: 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Global Administrator | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | TBD1 (Sub-Type) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Validation State | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 1 The value of the field TBD1 (Sub-Type) has to be assigned. The Global Administrator field MUST be set to the AS number of the validating BGP speaker conducting the prefix origin validation. The last field of the large community is an unsigned integer that gives the route's validation state as described in Section 4. If the validating BGP speaker is configured to support the extensions defined in this document, it SHOULD attach the origin validation state large community to BGP UPDATE messages sent to EBGP peers by mapping the computed validation state in the last field of the large community. A receiving BGP speaker, in the absence of a local validation state, SHOULD derive a validation state from the last field of the received large community, if present. An implementation SHOULD NOT send more than one instance of the origin validation state large community. However, if more than one instance is received, an implementation MUST disregard all instances other than the one with the numerically greatest validation state value. If the value received is greater than the largest specified value (2), the implementation MUST apply a strategy similar to attribute discard [RFC7606] by discarding the erroneous community and logging the error for further analysis. King, et al. Expires January 24, 2020 [Page 3] Internet-DraSignaling Prefix Origin Validation Results from a July 2019 3. BGP Prefix Origin Validation State Utilized at Validating Peers A validating BGP speaker that is aware of a BGP Prefix Origin Validation state (see Section 4) for a certain route can handle this information in one of the following modes of operation, attaching validation state to routes as discussed in Section 2: Simple Tagging: In this mode of operation, the BGP best path selection algorithm is executed. The prefix origin validation state is tagged accordingly. Dropping and Tagging: Routes for which the prefix origin validation state is "invalid" (according to [RFC6811]) are dropped by the validating BGP speaker. Based on the remaining set of routes, the BGP best path selection algorithm is executed. The prefix origin validation state of "not found" or "valid" (according to [RFC6811]) is tagged accordingly. Strict Dropping and Tagging: Routes for which the prefix origin validation state is "invalid" or "not found" (according to [RFC6811]) are dropped by the validating BGP speaker. Based on the remaining set of routes, the BGP best path selection algorithm is executed. The prefix origin validation state of "valid" is tagged to the advertised route. A validating BGP speaker MUST support the Dropping and Tagging operation mode. Other modes of operation are OPTIONAL. The mode of operation MAY be configured by the validating BGP speaker operator for all connected peers, or for each BGP session with a peer separately. Path hiding, as originally discussed in [RFC7947], may impact end-to- end connectivity for peers receiving prefixes via validating BGP speakers, if the best path selected contains a prefix with a prefix origin validation state which is subsequently dropped. However, these modes of operation might be used in combination with any options discussed in Section 2.3.2 of [RFC7947] in order to allow a peer to receive one or more routes and take the routing decision by itself, or with implementations who support sending the next best available path. 4. Signaling Prefix Origin Validation Results from a Validating Peer to Peers The EBGP Prefix Origin Validation State Community is utilized for signaling prefix origin validation result from a validating BGP speaker to other peers. King, et al. Expires January 24, 2020 [Page 4] Internet-DraSignaling Prefix Origin Validation Results from a July 2019 This draft proposes an encoding of the prefix origin validation result [RFC6811] as follows: +-------+-----------------------------+ | Value | Meaning | +-------+-----------------------------+ | 0 | Lookup result = "valid" | | 1 | Lookup result = "not found" | | 2 | Lookup result = "invalid" | +-------+-----------------------------+ Table 1 This encoding is re-used. Validating peers providing RPKI-based prefix origin validation set the validation state according to the prefix origin validation result (see [RFC6811]). 5. Operational Recommendations 5.1. Local Routing Decision Process A peer receiving prefix origin validation results from the route server MAY use the information in its own local routing decision process. The local routing decision process SHOULD apply to the rules as described in Section 5 [RFC6811]. A peer receiving a prefix origin validation result from the route server MAY redistribute this information within its own AS. In cases where multiple ASes are being administered by the same authority, peers MAY also redistribute this information across EBGP boundaries of the authority in question. 5.2. Validating Peers Receiving the EBGP Prefix Origin Validation State Large Community A validating BGP speaker receiving routes from peers containing the EBGP Prefix Origin Validation State Large Community MUST remove the large community before the route is re-distributed to its peers. This is required regardless of whether the validating BGP speaker is executing prefix origin validation or not. Failure to do so would allow opportunistic peers to advertise routes tagged with arbitrary prefix origin validation results via validating peers, influencing maliciously the decision process of other, non- validating BGP speakers. King, et al. Expires January 24, 2020 [Page 5] Internet-DraSignaling Prefix Origin Validation Results from a July 2019 5.3. Information about Validity of a BGP Prefix Origin Not Available at a Validating Peer In case information about the validity of a BGP prefix origin is not available at the validating BGP speaker (e.g., error in the ROA cache, CPU overload) the validating BGP speaker MUST NOT add the EBGP Prefix Origin Validation State Large Community to the route. 5.4. Error Handling at Peers A route sent by a validating BGP speaker SHOULD only contain none or one EBGP Prefix Origin Validation State Large Community. A peer receiving a route from a validating BGP speaker containing more than one EBGP Prefix Origin Validation State Large Community SHOULD only consider the largest value (as described in Table 1) in the validation result field and disregard the other values. Values larger than two in the validation result field MUST be disregarded. 6. Security Considerations All security considerations described in RFC6811 [RFC6811] fully apply to this document. Additionally, threat agents polluting ROA cache server(s) run by AS operators could cause significant operational impact, since multiple validating BGP speaker clients could be affected. Peers should be vigilant as to the integrity and authenticity of the origin validation results as they are provided by a third party, namely the AS operator hosting both the validating BGP speaker as well as any ROA cache server(s). Therefore, a validating BGP speaker could be misused to spread malicious prefix origin validation results. However, in the case of IXPs, peers already trust the route server for the collection, filtering (e.g., IRR database filtering), and redistribution of BGP routing information to other peers. To facilitate trust and support with peers establishing appropriate controls in mitigating the risks mentioned above, AS operators SHOULD provide out-of-band means for peers to ensure that the ROA validation process has not been compromised or corrupted. 7. References King, et al. Expires January 24, 2020 [Page 6] Internet-DraSignaling Prefix Origin Validation Results from a July 2019 7.1. 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, . [RFC6811] Mohapatra, P., Scudder, J., Ward, D., Bush, R., and R. Austein, "BGP Prefix Origin Validation", RFC 6811, DOI 10.17487/RFC6811, January 2013, . [RFC7153] Rosen, E. and Y. Rekhter, "IANA Registries for BGP Extended Communities", RFC 7153, DOI 10.17487/RFC7153, March 2014, . [RFC7606] Chen, E., Ed., Scudder, J., Ed., Mohapatra, P., and K. Patel, "Revised Error Handling for BGP UPDATE Messages", RFC 7606, DOI 10.17487/RFC7606, August 2015, . [RFC8092] Heitz, J., Ed., Snijders, J., Ed., Patel, K., Bagdonas, I., and N. Hilliard, "BGP Large Communities Attribute", RFC 8092, DOI 10.17487/RFC8092, February 2017, . [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, May 2017, . 7.2. Informative References [RFC6480] Lepinski, M. and S. Kent, "An Infrastructure to Support Secure Internet Routing", RFC 6480, DOI 10.17487/RFC6480, February 2012, . [RFC7947] Jasinska, E., Hilliard, N., Raszuk, R., and N. Bakker, "Internet Exchange BGP Route Server", RFC 7947, DOI 10.17487/RFC7947, September 2016, . Authors' Addresses King, et al. Expires January 24, 2020 [Page 7] Internet-DraSignaling Prefix Origin Validation Results from a July 2019 Thomas King DE-CIX Management GmbH Lichtstrasse 43i Cologne 50825 DE Email: thomas.king@de-cix.net Christoph Dietzel DE-CIX Management GmbH Lichtstrasse 43i Cologne 50825 DE Email: christoph.dietzel@de-cix.net Daniel Kopp DE-CIX Management GmbH Lichtstrasse 43i Cologne 50825 DE Email: daniel.kopp@de-cix.net Aristidis Lambrianidis Amsterdam Internet Exchange Frederiksplein 42 Amsterdam 1017 XN NL Email: aristidis.lambrianidis@ams-ix.net King, et al. Expires January 24, 2020 [Page 8]