Network Working Group                                     T. BruijnzeelsInternet-Draft                                                T. de KockIntended status: Best Current Practice                          RIPE NCCExpires: 23 April 2026                                           F. Hill                                                                    ARIN                                                             T. Harrison                                                                   APNIC                                                             J. Snijders                                                                     BSD                                                         20 October 2025             RPKI Publication Server Best Current Practices              draft-ietf-sidrops-publication-server-bcp-05Abstract   This document describes best current practices for operating an RFC   8181 RPKI Publication Server and its rsync (RFC 5781) and RRDP (RFC   8182) public repositories.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 23 April 2026.Copyright Notice   Copyright (c) 2025 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 ComponentsBruijnzeels, et al.       Expires 23 April 2026                 [Page 1]Internet-Draft     RPKI Publication Server Operations       October 2025   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.  Requirements notation . . . . . . . . . . . . . . . . . . . .   2   2.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   3   3.  Glossary  . . . . . . . . . . . . . . . . . . . . . . . . . .   3   4.  Publication Server  . . . . . . . . . . . . . . . . . . . . .   3     4.1.  Self-Hosted Publication Server  . . . . . . . . . . . . .   4     4.2.  Publication Server as a Service . . . . . . . . . . . . .   5     4.3.  Availability  . . . . . . . . . . . . . . . . . . . . . .   5     4.4.  Data Loss . . . . . . . . . . . . . . . . . . . . . . . .   6     4.5.  Publisher Repository Synchronisation  . . . . . . . . . .   6   5.  Hostnames . . . . . . . . . . . . . . . . . . . . . . . . . .   7   6.  IP Address Space and Autonomous Systems . . . . . . . . . . .   7   7.  RRDP Server . . . . . . . . . . . . . . . . . . . . . . . . .   8     7.1.  Same Origin URIs  . . . . . . . . . . . . . . . . . . . .   8     7.2.  Endpoint Protection . . . . . . . . . . . . . . . . . . .   8     7.3.  Bandwidth and Data Usage  . . . . . . . . . . . . . . . .   8     7.4.  Content Availability  . . . . . . . . . . . . . . . . . .   9     7.5.  Limit Notification File Size  . . . . . . . . . . . . . .  10     7.6.  Manifest and CRL Update Times . . . . . . . . . . . . . .  11     7.7.  Consistent Load-Balancing . . . . . . . . . . . . . . . .  11       7.7.1.  Notification File Timing  . . . . . . . . . . . . . .  11       7.7.2.  L4 Load-Balancing . . . . . . . . . . . . . . . . . .  12   8.  Rsync Server  . . . . . . . . . . . . . . . . . . . . . . . .  12     8.1.  Consistent Content  . . . . . . . . . . . . . . . . . . .  12     8.2.  Deterministic Timestamps  . . . . . . . . . . . . . . . .  13     8.3.  Load Balancing and Testing  . . . . . . . . . . . . . . .  14   9.  Acknowledgments . . . . . . . . . . . . . . . . . . . . . . .  14   10. Normative References  . . . . . . . . . . . . . . . . . . . .  14   11. Informative References  . . . . . . . . . . . . . . . . . . .  16   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  161.  Requirements notation   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.Bruijnzeels, et al.       Expires 23 April 2026                 [Page 2]Internet-Draft     RPKI Publication Server Operations       October 20252.  Introduction   [RFC8181] describes the RPKI Publication Protocol used between RPKI   Certification Authorities (CAs) and their Publication Servers.  The   server is responsible for handling publication requests sent by the   CAs, called Publishers in this context, and ensuring that their data   is made available to RPKI Relying Parties (RPs) in (public) rsync and   RRDP [RFC8182] repositories.   In this document, we will describe best current practices based on   the operational experience of several implementers and operators.3.  Glossary           +====================+==============================+           | Term               | Description                  |           +====================+==============================+           | Publication Server | [RFC8181] Publication Server |           +--------------------+------------------------------+           | Publishers         | [RFC8181] Publishers         |           |                    | (Certification Authorities)  |           +--------------------+------------------------------+           | RRDP Server        | Public-facing [RFC8182] RRDP |           |                    | server                       |           +--------------------+------------------------------+           | Rsync Server       | Public-facing rsync server   |           +--------------------+------------------------------+           | rsyncd             | Software daemon package      |           |                    | providing rsync service      |           +--------------------+------------------------------+           | RIR                | Regional Internet Registry   |           +--------------------+------------------------------+           | NIR                | National Internet Registry   |           +--------------------+------------------------------+                                  Table 14.  Publication Server   The Publication Server handles the server side of the [RFC8181]   Publication Protocol.  The Publication Server generates the content   for the public-facing RRDP and Rsync Servers.  It is strongly   RECOMMENDED that these functions are separated from serving the   repository content.Bruijnzeels, et al.       Expires 23 April 2026                 [Page 3]Internet-Draft     RPKI Publication Server Operations       October 20254.1.  Self-Hosted Publication Server   Generally, address holders that want to make use of RPKI will rely on   a CA hosted by the provider of those addresses, typically an RIR or   an NIR.  In some instances, address holders will instead deploy and   manage a CA themselves.  This type of CA is commonly referred to as a   self-hosted CA, or delegated CA.   When operating a self-hosted CA, the address holder must decide how   they will handle publication.  The holder can either deploy their own   Publication Server and associated infrastructure (referred to as a   self-hosted repository), or rely on a third-party Publication Server.   If the holder uses a self-hosted repository, then they are   responsible for ensuring the availability of signed content via RRDP   and rsync as described in section 5 and 6 of this document.   RPs are expected to make use of cached data from a previous,   successful fetch (Section 6 of [RFC9286]).  Therefore, short outages   on the server side do not need to be cause for immediate concern,   provided the server operator restores access availability in a timely   fashion (e.g., before objects expire).   However, in practice, self-hosted repositories tend to have frequent   availability issues when compared with those provided by larger   organisations like RIRs and NIRs.  Additionally, the greater the   number of separate repositories, the greater the chance for negative   impact on RPs.  Therefore, CAs that act as parents of other CAs are   RECOMMENDED to provide a publication service for their child CAs, and   CAs with a parent who offers a publication service are RECOMMENDED to   use that service, instead of running their own.  If a CA's parent   does not offer a publication service, but the CA operator is able to   use a reliable third-party Publication Server, the CA operator SHOULD   make use of that service.   For the case of a 'grandchild' CA, where CA1 is a TA, CA2 is a child   CA of CA1, and CA3 is a child CA of CA2, there are several options   for providing publication service to CA3:   1.  RFC 8183 defines a 'referral' mechanism as part of the out-of-       band CA setup protocol.  If supported by CA1 and CA2, then this       simplifies the process of registering CA3 as a direct publication       client of CA1.   2.  CA1 may support the registration of multiple publishers by CA2,       by using the publisher_request/repository_response XML exchange       defined in RFC 8183.  CA2 would then be able to register a       separate publisher on behalf of CA3.Bruijnzeels, et al.       Expires 23 April 2026                 [Page 4]Internet-Draft     RPKI Publication Server Operations       October 2025   3.  CA2 may operate a publication proxy service (per e.g.       [rpki-publication-proxy]), which acts as the Publication Server       for CA3.  This proxy would set aside part of CA2's namespace at       CA1 for the publication of CA3's objects, adjusting and       forwarding requests from CA3 to CA1 accordingly.   For options 1 and 2, CAs operating as CA1 should consider the   implications of providing direct publication service to CA3 in this   way: for example, CA3 may expect publication service technical   support from CA1 directly.4.2.  Publication Server as a Service   The Publication Server and repository content have different demands   on their availability and reachability.  While the repository content   MUST be highly available to any RP worldwide, only publishers need to   access the Publication Server.  Depending on the specific setup, this   may allow for additional access restrictions in this context.  For   example, the Publication Server can limit access to known source IP   addresses or apply rate limits.   If the Publication Server is unavailable for some reason, this will   prevent Publishers from making updated RPKI objects available.  The   most immediate impact of this is that the publisher cannot distribute   new issuances or revocations of ROAs, ASPAs or BGPsec Router   Certificates for the duration of this outage.  Thus, in effect, it   cannot signal changes in its routing operations.  If the outage   persists for an extended period, then RPKI Manifests, CRLs, and   Signed Objects might became stale, hampering for example BGP Origin   Validation ([RFC6811]).   For this reason, the Publication Server MUST be highly available.   Measuring the availability of the Publication Server in a round-trip   fashion is recommended by monitoring the publication of objects.   Maintenance windows SHOULD be planned and communicated to publishers.   This makes publishers aware of the root cause for disruption in the   Publication Server, as well as supporting them more generally in   their administration of their RPKI CA and associated systems.4.3.  Availability   Short outages of an [RFC8181] Publication Server will not affect RPs   as long as the corresponding RRDP and rsync repositories remain   available.  However, such outages prevent publishers from updating   their ROAs and reissuing their manifests and CRLs in a timely manner.Bruijnzeels, et al.       Expires 23 April 2026                 [Page 5]Internet-Draft     RPKI Publication Server Operations       October 2025   The propagation time between ROA issuance and the ultimate use of the   resulting VRPs in routers is described in table 2 of   [rpki-time-in-flight], as at the time of that study.  That   propagation time was between 15 and 95 minutes for the CAs and   associated repositories that were analysed.  As seen in the study,   the delay between signing and publication can be a major contributor   to long propagation times.   The potential unavailability of a Publication Server adds to this   propagation delay.  Publication Servers SHOULD therefore aim for high   availability of the [RFC8181] publication protocol service.4.4.  Data Loss   Publication Servers MUST aim to minimise data loss.  If a server   restore is needed and a content regression has occurred, then the   server MUST perform an RRDP session reset.   Publishing CAs typically only check in with their Publication Server   when they have changes that need to be published.  As a result, they   may not be aware if the server performed a restore and their content   regressed to an earlier state.  This could result in a number of   problems:   *  The published ROAs no longer reflect the CA's intentions.   *  The CA might not reissue their Manifest or CRL in time, because      they operated under the assumption that the currently-published      Manifest and CRL have not yet became stale.   *  Changes to publishers may not have been persisted.  Newly      registered publishers may not be present, and recently removed      publishers may still be present.   Therefore, the Publication Server SHOULD notify publishing CAs about   this issue if it occurs, so that a full resynchronisation can be   initiated by CAs.4.5.  Publisher Repository Synchronisation   It is RECOMMENDED that publishing CAs always perform a list query as   described in section 2.3 of [RFC8181] before submitting changes to   the Publication Server.  This approach means that any   desynchronisation issue can be resolved at least as soon as the   publisher is aware of updates that it needs to publish.Bruijnzeels, et al.       Expires 23 April 2026                 [Page 6]Internet-Draft     RPKI Publication Server Operations       October 2025   When publishing changes, CAs SHOULD send all of their changes using   multiple PDUs in a single multi-element query message, as described   in section 2.2 and section 3.7.1 of [RFC8181].  This reduces the risk   of change sets that were intended to take effect as a single unit   from taking effect separately.   In addition to the above, the publishing CA MAY perform regular   planned synchronisation events where it issues an [RFC8181] list   query and ensures that the Publication Server has the expected state,   even if the CA has no new content to publish.  For Publication   Servers that serve a large number of CAs (e.g., thousands) this   operation could become costly from a resource consumption   perspective.  Unfortunately, the [RFC8181] protocol has no proper   support for rate limiting.  Therefore, publishers SHOULD NOT perform   this resynchronisation more frequently than once every 10 minutes   unless otherwise agreed with the Publication Server.5.  Hostnames   It is RECOMMENDED that the public RRDP Server URI have a different   hostname from that of the [RFC8181] service_uri used by publishers,   as well as that of any rsync URIs (e.g. sia_base) used by the   relevant Publication Server.   Using a unique hostname will allow the operator to use dedicated   infrastructure and/or a Content Delivery Network (CDN) for its RRDP   content without interfering with the other functions.   If feasible, there is merit in using different TLDs and/or subdomains   for these hostnames, as DNS issues at any level could otherwise be a   single point of failure affecting both RRDP and rsync.  Operators   need to weigh this benefit against potential increased operational   risk and the burden of maintaining multiple domains.  Because the   usefulness of this approach is highly context-dependent, no normative   recommendation is given here.   Furthermore, it is RECOMMENDED that DNSSEC is used in accordance with   best current practice as described in [RFC9364].6.  IP Address Space and Autonomous Systems   To prevent failure scenarios which persist beyond remediation, the   topological placement and reachability of Publication Servers in the   global Internet routing system need to be considered very carefully.   See section 6 of [RFC7115].Bruijnzeels, et al.       Expires 23 April 2026                 [Page 7]Internet-Draft     RPKI Publication Server Operations       October 2025   An example of a problematic scenario would be when a prefix or AS   path related to a repository becomes invalid because of RPKI objects   published in that repository.  As a result, RPs may be unable to   retrieve remediating updates from that repository.   With the above in mind, it is RECOMMENDED to use IP addresses for   RRDP and rsync services from IP address space which is not   subordinate to authorities solely dependent on those service   endpoints.   It is also RECOMMENDED to host RRDP and rsync services in Autonomous   Systems which are not subordinate to authorities publishing through   those same endpoints.   It is RECOMMENDED to host RRDP and rsync services in different   networks.7.  RRDP Server7.1.  Same Origin URIs   Publication Servers need to take note of the normative updates to   [RFC8182] in section 3.1 of [RFC9674].  In short, this means that all   delta and snapshot URIs need to use the same host, and redirects to   other origins are not allowed.7.2.  Endpoint Protection   Repository operators SHOULD use access control to protect their RRDP   endpoints.  For example. if the repository operator knows HTTP GET   parameters are not in use, then all requests containing GET   parameters can be blocked.7.3.  Bandwidth and Data Usage   The bandwidth needed for RRDP evolves over time, and depends on many   parameters.  These consist of three main groups:   1.  RRDP-specific repository properties, such as the size of       notification, delta, and snapshot files.   2.  Properties of the CAs publishing through a particular server,       such as the number of updates, number of objects, and size of       objects.   3.  Relying party behaviour, e.g. using HTTP compression, requiring       timeouts or minimum transfer speed for downloads, and using       conditional HTTP requests for notification.xml.Bruijnzeels, et al.       Expires 23 April 2026                 [Page 8]Internet-Draft     RPKI Publication Server Operations       October 2025   When an RRDP repository server is overloaded, e.g. where the   bandwidth demands exceed capacity, this causes a negative feedback   loop (i.e. the aggregate load increases), and the efficiency of RRDP   degrades.  For example, when an RP attempts to download one or more   delta files, and one fails, it will typically try to download the   snapshot (larger than the sum of the size of the deltas).  If this   also fails, the RP falls back to rsync.  Furthermore, when the RP   tries to use RRDP again on the next run, it typically starts by   downloading the snapshot.   A Publication Server SHOULD attempt to prevent these issues by   closely monitoring performance (e.g. bandwidth, performance on an RP   outside their network, unexpected fallback to snapshot).  Besides   increasing the capacity, we will discuss several other measures to   reduce bandwidth demands.   Publication Servers SHOULD support compression.  As the RRDP XML and   embedded base64 content is highly compressible, this can reduce   transferred data by about 50%. Servers SHOULD at least support either   deflate or gzip content encoding as described in sections 8.4.1.2 and   8.4.1.3 of [RFC9110], in addition to any other popular compression   types that the server can support.7.4.  Content Availability   Publication Servers MUST ensure that their RRDP servers are highly   available.   If possible, it is strongly RECOMMENDED that a CDN is used to serve   the RRDP content.  Care MUST be taken to ensure that the notification   file is not cached for longer than 1 minute unless the backend RRDP   Server is unavailable, in which case it is RECOMMENDED that stale   files are served.   A CDN will likely cache 404s for files not found on the backend   server.  Because of this, the Publication Server SHOULD use   randomised, unpredictable paths for snapshot and delta Files to avoid   the CDN caching such 404s for future updates.  Alternatively, the   Publication Server can clear the CDN cache for any new files it   publishes.   Note that some organisations that run a Publication Server may be   able to attain a similar level of availability themselves without the   use of a third-party CDN.  This document makes no specific   recommendations on achieving this, as this is highly dependent on   local circumstances and operational preferences.Bruijnzeels, et al.       Expires 23 April 2026                 [Page 9]Internet-Draft     RPKI Publication Server Operations       October 2025   Also note that small repositories that serve a single CA, and which   serve a small amount of data that does not change frequently, may   attain high availability using a modest setup.  Short downtime would   not lead to immediate issues for the CA, provided that the service is   restored before their manifest and CRL expire.  This may be   acceptable to the CA operator; however, because this can negatively   impact RPs, it is RECOMMENDED that these CAs instead use a   Publication Server that is provided as a service, e.g. by their RIR   or NIR.7.5.  Limit Notification File Size   Nowadays, most RPs use conditional requests for notification files,   which reduces the traffic for repositories that do not often update   relative to the resynchronisation frequency of RPs.  On the other   hand, for repositories that update frequently, the underlying   snapshot and delta content accounts for most of the traffic.  For   example, for a large repository in January 2024, with a notification   file with 144 deltas covering 14 hours, the requests for the   notification file accounted for 251GB of traffic out of a total of   55.5TB (i.e. less than 0.5% of the total traffic during that period).   However, for some servers, this ratio may be different.  [RFC8182]   stipulates that the sum of the size of deltas MUST not exceed the   snapshot size, in order to avoid RPs downloading more data than   necessary.  However, this does not account for the size of the   notification file that all RPs download.  Keeping many deltas present   may allow RPs to recover more efficiently if they are significantly   out of sync.  Still, including all such deltas can also increase the   total data transfer, because it increases the size of the   notification file.   In order to mitigate potential problems here, the notification file   size SHOULD be reduced by removing from the notification file delta   files that have been available for a long time.  Because some RPs   will only update every 1-2 hours (in 2024), the Publication Server   SHOULD include deltas for at least 4 hours.   Furthermore, it is RECOMMENDED that Publication Servers do not   produce delta files more frequently than once per minute.  A possible   approach for this is that the Publication Server SHOULD publish   changes at a regular (one minute) interval.  The Publication Server   then publishes the updates received from all Publishers in this   interval in a single RRDP delta file.   While the latter may not reduce the amount of data due to changed   objects, this will result in shorter notification files, and will   reduce the number of delta files that RPs need to fetch and process.Bruijnzeels, et al.       Expires 23 April 2026                [Page 10]Internet-Draft     RPKI Publication Server Operations       October 20257.6.  Manifest and CRL Update Times   The manifest and CRL nextUpdate times and validity periods are   determined by the issuing CA rather than the Publication Server.   From the CA's point of view, longer validity periods mean that there   is more time to resolve unforeseen operational issues, since the   current RPKI objects will remain valid for longer.  On the other   hand, longer validity periods also increase the risk of a successful   replay attack.   From the Publication Server's point of view, shorter update times   result in more data churn due to manifest and CRL reissuance.  While   the choice is made by the CAs, in certain modes of operation (e.g.   hosted RPKI services) it may be possible to adjust the timing of   manifest and CRL reissuance.  One large repository has found that   increasing the reissuance cycle from once every 24 hours to once   every 48 hours (still deemed acceptable) reduced the data usage by   approximately 50%, as most changes in the system are due to   reissuance of manifests and CRLs, rather than e.g. ROA changes.7.7.  Consistent Load-Balancing7.7.1.  Notification File Timing   Notification Files MUST NOT be available to RPs before the referenced   snapshot and delta files are available.   As a result, when using a load-balancing setup, care SHOULD be taken   to ensure that RPs that make multiple subsequent requests receive   content from the same node (e.g. consistent hashing).  This way,   clients view the timeline on one node where the referenced snapshot   and delta files are available.  Alternatively, publication   infrastructure SHOULD ensure a particular ordering of the visibility   of the snapshot plus delta and notification file.  All nodes should   receive the new snapshot and delta files before any node receives the   new notification file.   When using a load-balancing setup with multiple backends, each   backend MUST provide a consistent view and MUST update more   frequently than the typical refresh rate for rsync repositories used   by RPs.  When these conditions hold, RPs observe the same RRDP   session with the serial monotonically increasing.  Unfortunately,   [RFC8182] does not specify RP behavior if the serial regresses.  As a   result, some RPs download the snapshot to re-sync if they observe a   serial regression.Bruijnzeels, et al.       Expires 23 April 2026                [Page 11]Internet-Draft     RPKI Publication Server Operations       October 20257.7.2.  L4 Load-Balancing   If an RRDP repository uses L4 load-balancing, some load balancer   implementations will keep in the pool connections to a node that is   no longer active (e.g. one that is disabled because of maintenance).   Due to HTTP keepalive, requests from an RP (or CDN) may continue to   use the disabled node for an extended period.  This issue is   especially prominent with CDNs that use HTTP proxies internally when   connecting to the origin while also load-balancing over multiple   proxies.  As a result, some requests may use a connection to the   disabled server and retrieve stale content, while other connections   retrieve data from another server.  Depending on the exact   configuration - for example, nodes behind the load balancer may have   different RRDP sessions - this can lead to clients observing   inconsistent RRDP repository state.   Because of this issue, it is RECOMMENDED to (1) limit HTTP keepalive   to a short period on the servers in the pool and (2) limit the number   of HTTP requests per connection.  When applying these   recommendations, this issue is limited (and effectively less   impactful when using a CDN due to caching) to a failover between RRDP   sessions, where clients also risk reading a notification file for   which some of the content is unavailable.8.  Rsync Server   In this section, we will elaborate on the following recommendations:   *  Use symlinks to provide consistent content   *  Use deterministic timestamps for files   *  Load balancing and testing8.1.  Consistent Content   A naive implementation of the Rsync Server might change the   repository content while RPs are transferring files.  Even when the   repository is consistent from the repository server's point of view,   clients may read an inconsistent set of files.  Clients may get a   combination of newer and older files.  This "phantom read" can lead   to unpredictable and unreliable results.  While modern RPs will treat   such inconsistencies as a "Failed Fetch" ([RFC9286]), it is best to   avoid this situation altogether, since a failed fetch for one   repository can cause the rejection of delegated certificates and/or   RPKI signed objects for a sub-CA when resources change.Bruijnzeels, et al.       Expires 23 April 2026                [Page 12]Internet-Draft     RPKI Publication Server Operations       October 2025   One way to ensure that rsyncd serves connected clients (RPs) with a   consistent view of the repository is by configuring the rsyncd   'module' path to a path that contains a symlink that the repository-   writing process updates for every repository publication.   Following this process, when an update is published:   1.  write the complete updated repository into a new directory   2.  fix the timestamps of files (see next section)   3.  change the symlink to point to the new directory   Multiple implementations implement this behavior ([krill-sync],   [rpki-core], [rsyncit], the rpki.apnic.net repositories, a supporting   shellscript [rsync-move]).   Because rsyncd resolves this symlink when it chdirs into the module   directory when a client connects, any connected RPs can read a   consistent state.  To limit the amount of disk space a repository   uses, a Rsync Server must clean up copies of the repository; the   timing of these removal operations involves balancing the provision   of service to slow clients against the additional disk space required   to support those clients.   A repository can safely remove old directories when no RP fetching at   a reasonable rate is reading that data.  Since the last moment an RP   can start reading from a copy is when it last "current", the time a   client has to read a copy begins when it was last current (cf. the   time when it was originally written).   Empirical data suggests that Rsync Servers MAY assume it is safe to   remove old instances of repositories after one hour.  We recommend   monitoring for "file has vanished" lines in the rsync log file to   detect how many clients are affected by this cleanup process.8.2.  Deterministic Timestamps   By default, rsync uses the modification time and file size to   determine if it should transfer a file.  Therefore, throughout a   file's lifetime, the modification time SHOULD NOT change unless the   file's content changes.   We RECOMMEND the following deterministic heuristics for objects'   timestamps when written to disk.  These heuristics assume that a CA   is compliant with [RFC9286] and uses "one-time-use" EE certificates:   *  For CRLs, use the value of thisUpdate.   *  For RPKI Signed Objects, use the CMS signing-time (see      ([RFC9589])).Bruijnzeels, et al.       Expires 23 April 2026                [Page 13]Internet-Draft     RPKI Publication Server Operations       October 2025   *  For CA and BGPsec Router Certificates, use the value of notBefore.   *  For directories, use any constant value.8.3.  Load Balancing and Testing   To increase availability during both regular maintenance and   exceptional situations, a rsync repository that strives for high   availability should be deployed on multiple nodes load-balanced by an   L4 load balancer.  Because Rsync sessions use a single TCP connection   per session, there is no need for consistent load-balancing between   multiple rsync servers as long as they each provide a consistent   view.   It is RECOMMENDED that the Rsync Server is load tested to ensure that   it can handle simultaneous requests from all RPs, in case those RPs   need to fall back from using RRDP (as is currently preferred).   We RECOMMEND serving rsync repositories from local storage, so that   the host operating system can optimally use its I/O cache.  Using   network storage is NOT RECOMMENDED, because it may not benefit from   this cache.  For example, when using NFS, the operating system cannot   cache the directory listing(s) of the repository.   We RECOMMENDED setting the "max connections" to a value that allows a   single node to handle simultaneous resynchronisation by that number   of RPs, taking into account the amount of time that RP   implementations usually allow for rsync resychronisation.  Load-   testing results show that machine memory is likely the limiting   factor for large repositories that are not IO limited.   The number of rsync servers needed depends on the number of RPs,   their refresh rate, and the "max connections" used.  These values are   subject to change over time, so we cannot give clear recommendations   here except to restate that we RECOMMEND load-testing rsync and   reevaluating these parameters over time.9.  Acknowledgments   This document is the result of many informal discussions between   implementers.  The authors wish to thank Mike Hollyman for editorial   suggestions.10.  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>.Bruijnzeels, et al.       Expires 23 April 2026                [Page 14]Internet-Draft     RPKI Publication Server Operations       October 2025   [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>.   [RFC7115]  Bush, R., "Origin Validation Operation Based on the              Resource Public Key Infrastructure (RPKI)", BCP 185,              RFC 7115, DOI 10.17487/RFC7115, January 2014,              <https://www.rfc-editor.org/info/rfc7115>.   [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>.   [RFC8181]  Weiler, S., Sonalker, A., and R. Austein, "A Publication              Protocol for the Resource Public Key Infrastructure              (RPKI)", RFC 8181, DOI 10.17487/RFC8181, July 2017,              <https://www.rfc-editor.org/info/rfc8181>.   [RFC8182]  Bruijnzeels, T., Muravskiy, O., Weber, B., and R. Austein,              "The RPKI Repository Delta Protocol (RRDP)", RFC 8182,              DOI 10.17487/RFC8182, July 2017,              <https://www.rfc-editor.org/info/rfc8182>.   [RFC9110]  Fielding, R., Ed., Nottingham, M., Ed., and J. Reschke,              Ed., "HTTP Semantics", STD 97, RFC 9110,              DOI 10.17487/RFC9110, June 2022,              <https://www.rfc-editor.org/info/rfc9110>.   [RFC9286]  Austein, R., Huston, G., Kent, S., and M. Lepinski,              "Manifests for the Resource Public Key Infrastructure              (RPKI)", RFC 9286, DOI 10.17487/RFC9286, June 2022,              <https://www.rfc-editor.org/info/rfc9286>.   [RFC9364]  Hoffman, P., "DNS Security Extensions (DNSSEC)", BCP 237,              RFC 9364, DOI 10.17487/RFC9364, February 2023,              <https://www.rfc-editor.org/info/rfc9364>.   [RFC9589]  Snijders, J. and T. Harrison, "On the Use of the              Cryptographic Message Syntax (CMS) Signing-Time Attribute              in Resource Public Key Infrastructure (RPKI) Signed              Objects", RFC 9589, DOI 10.17487/RFC9589, May 2024,              <https://www.rfc-editor.org/info/rfc9589>.   [RFC9674]  Snijders, J., "Same-Origin Policy for the RPKI Repository              Delta Protocol (RRDP)", RFC 9674, DOI 10.17487/RFC9674,              December 2024, <https://www.rfc-editor.org/info/rfc9674>.Bruijnzeels, et al.       Expires 23 April 2026                [Page 15]Internet-Draft     RPKI Publication Server Operations       October 202511.  Informative References   [krill-sync]              Bruijnzeels, T., "krill-sync", 2023,              <https://github.com/NLnetLabs/krill-sync>.   [rpki-core]              Team, R., "rpki-core", 2023,              <https://github.com/RIPE-NCC/rpki-core>.   [rpki-publication-proxy]              APNIC, "rpki-publication-proxy", 2018,              <https://github.com/APNIC-net/rpki-publication-proxy>.   [rpki-time-in-flight]              Fontugne, R., Phokeer, A., Pelsser, C., Vermeulen, K., and              R. Bush, "RPKI Time-of-Flight: Tracking Delays in the              Management, Control, and Data Planes", 2022,              <https://www.iijlab.net/en/members/romain/pdf/              romain_pam23.pdf>.   [rsync-move]              Snijders, J., "rpki-rsync-move.sh.txt", 2023,              <http://sobornost.net/~job/rpki-rsync-move.sh.txt>.   [rsyncit]  Team, R., "rpki-core", 2023,              <https://github.com/RIPE-NCC/rsyncit>.Authors' Addresses   Tim Bruijnzeels   RIPE NCC   Email: tbruijnzeels@ripe.net   Ties de Kock   RIPE NCC   Email: tdekock@ripe.net   Frank Hill   ARIN   Email: frank@arin.net   Tom Harrison   APNIC   Email: tomh@apnic.netBruijnzeels, et al.       Expires 23 April 2026                [Page 16]Internet-Draft     RPKI Publication Server Operations       October 2025   Job Snijders   BSD Software Development   Amsterdam   Netherlands   Email: job@bsd.nlBruijnzeels, et al.       Expires 23 April 2026                [Page 17]