November 2023 - dns-wg - mailman.ripe.net

Draft of RIPE DNS Resolver Best Common Practices
by Shane Kerr 08 Feb '24

08 Feb '24

Colleagues, Here is a draft of the RIPE DNS Resolver Best Common Practices document that the task force of that name has been working on. The intention is to collect feedback during the RIPE 87 meeting and afterwards, and either publish a RIPE document or another draft based on that. Cheers, -- Shane Kerr Chair, RIPE DNS Resolver BCP Task Force # DNS Resolver Recommendations About the DNS Resolver Best Common Practice Task Force https://www.ripe.net/participate/ripe/tf/dns-resolver-best-common-practice-… ## Terminology * Open Resolver: A DNS resolver that accepts queries from any client. Often the result of misconfiguration. * Public Resolver: A resolver intentionally configured to be an open resolver. ## Introduction ### What Is This Document? Who Is It For? This document presents recommendations and best current practices for operating DNS resolvers, both public and non-public ones. It covers technical aspects of operations and provides best practice recommendations for data management, with a particular focus on user privacy, security, and resilience. The document serves as guidance for the wider Internet community, offering input to: * Those running public DNS resolver services, and * Those who want to make informed choices between such services. Its purpose is to provide clear guidance and promote effective practices in DNS resolver operation. The intended audience is not the entire DNS community. Advice here is probably not useful for operators of authoritative servers, domain registrars, and so on. It is also not meant to be an introductory or educational document. There are many documents which cover the basics of DNS and the roles of organizations in it; a good overview is: Addressing the challenges of modern DNS - a comprehensive tutorial by van der Toorn et al. https://ris.utwente.nl/ws/files/282427879/1_s2.0_S1574013722000132_main.pdf The document does not consider how to measure adherence to these recommendations. So it is not intended to be used for certification, although certification created based on the principles here is possible. ### How Is This Document Organized? This document has a number of sections, and specific recommendations in each section. The intent is for each recommendations to have clear guidance at the top, and then background and discussion related to the recommendation afterwards. Each recommendation indicates whether it is mostly for operators of public resolvers or for operators of any resolver. ## System and Network Hardening ### Infrastructure considerations Running any Internet service requires attention to the infrastructure used to operate it. This section discusses various approaches that can be used to run a DNS resolver. Everything applies to both public and non-public DNS resolvers. #### Bare metal or public cloud All DNS resolver software can run either on dedicated servers (rented or colocated), or in virtualized clouds, or in a combination of those. Every approach has pros and cons. Most of these are not specific to running DNS resolvers, however, some of them are. **Running DNS resolver instances as OS level daemons on bare metal hosts:** Pros: - Performance: Bare metal servers have direct access to the underlying hardware, and can offer superior performance/cost balance by avoiding the overhead associated with virtualization. Moreover, you have full control over the server's configurations, down to the hardware level, which can be beneficial for performance and cost optimization once you get the understanding of your typical work load during peak hours. - Data Security: Since you are in control of the physical servers, there is no risk of data leakage that can occur due to vulnerabilities in multi-tenant virtualization platforms, including CPU cache-based side-channel vulnerabilities. It could be argued that attacks targeting such issues are rare, and their impact on a DNS resolver service is low, but potential breaches may have significant privacy impact. It is advised to evaluate this against your organisation's risk model, or to discuss this with your information security compliance experts. - Predictability: Because there is no virtualization layer and no "noisy neighbours" on the host, the performance of your servers is more predictable. Cons: - Cost of failure: If you pick hardware configuration that is not optimal for the workload of your DNS resolver, you may need to upgrade and replace hardware components afterwards. Ways to reduce this risk include renting servers instead of buying them, carrying load testing with data similar to production workloads, and providing limited beta access to the service before it fully enters the production phase. - Scalability: Scaling up with physical servers means acquiring or renting, installing, and configuring new hardware, which will take more time than provisioning new virtual servers in a cloud environment. Moreover, most cloud environments will provide you with cluster autoscaling features, which could barely be achieved in bare metal. - Maintenance: You will be responsible for all server maintenance tasks, including hardware issues, which can require significant effort and specific expertise. - Redundancy: Setting up high availability and disaster recovery strategies can be more complex and time consuming compared to the cloud, where these features are often provided as value added products. See the Redundancy section for more details. **Running DNS resolver instances in containers in a public cloud:** Pros: - Scalability: Clouds excel at scaling applications. You can scale up and down rapidly based on load, which is important for a DNS resolver that needs to handle variable query loads. In case of regional or geographically distributed resolvers, in every region where the resolver would be deployed, daily periodicity is likely to be observed, for example peak hour is likely to occur around 19:00 local time, and off-peak hours may begin at around 01:00-03:00. In a situation like that, using cluster autoscaling features and tools, you can run less instances in the night and more instances throughout the day, which may help to optimize your cloud hosting costs. - Fault Tolerance and High Availability: Most clouds have built-in strategies, features, and products for handling node failures, which can increase your service's availability. - Deployment and Management: Cloud providers offer built-in methods to deploy and manage applications, which can simplify operations and reduce the likelihood of human errors if your infrastructure management department is already familiar with these tools. - Cost: While this largely depends on your specific usage, cloud services can sometimes be more cost-effective than managing your own physical servers, especially when you consider the total cost of ownership, including power, cooling, and maintenance. Cons: - Performance: The virtualization layer of public clouds can impact performance. While this certainly could be mitigated through scaling the number of virtual hosts, the cost would also increase accordingly. - Complexity: Advanced cloud technologies are complex systems which come with a steep learning curve. Without prior experience, properly configuring and managing a cloud-based compute cluster can be challenging. - Cost Variability: While the cloud can be cheaper, it can also be more expensive if not properly managed. Costs can rise unexpectedly based on traffic. Make sure to always set some limits on how much may be spent on hosting in the cloud control panel, and to set up notifications to be sent to you when these thresholds are about to be triggered. - Multi-tenancy Risks: In a public cloud environment, the "noisy neighbour" problem could potentially affect your service's performance. Additionally, even though cloud providers take steps to isolate tenant environments, vulnerabilities could potentially expose sensitive data (see the previous section for a detailed explanation). **Additional considerations** - In today's environments, Kubernetes and Terraform are sometimes used as a substitute for cloud APIs when it comes to production services' management. When running a DNS resolver in a Kubernetes cluster on top of a public cloud environment, all the pros and cons of the public cloud apply; basically, Kubernetes becomes your public cloud provider. If you have significant prior experience running services in Kubernetes in production, you may successfully replicate your experience with the DNS resolver software. Otherwise, we would advise against Kubernetes in this case. - The only reason we may find to run a DNS resolver in a Kubernetes cluster on top of self-hosted dedicated servers is when you have significant hands-on experience with Kubernetes and it is natural for you to manage applications this way. Otherwise, running DNS resolver daemons in containers brings little, if any, benefit. Autoscaling features are not available to you in this case, and neither horizontal nor vertical pod autoscaling is of any use, because DNS resolver software typically scales in-host by itself just fine. - When designing a cluster of resolvers for autoscaling, keep in mind that newly spawned resolver machines would need to populate resolver cache first before they are fully useful. Your DNS resolver software may provide cache replication mechanisms. Otherwise, it is safe to overprovision clusters somewhat under heavy load, and discarding excessive instances once all the caches are populated and the average load of a compute instance decreases. In addition, it may be worthwhile to consider sharing cache data between instances. - It is always advised to prefer environments your infrastructure management team is familiar with. ### Software considerations #### Open Source **Recommendation**: Choose any well-maintained DNS software you are comfortable using. Regardless of which software you choose, ensure you have somewhere to go for support. In the case of open source software, consider providing financial support to ensure continued development. Some open source maintainers take donations, while others offer support contracts. There are both open source and proprietary implementations of DNS resolver software. Mixing these is also possible, for example, by using proprietary extensions with open source software or deploying open source software modified in-house. General observations: - Software licensing is orthogonal to software security. Neither is proprietary software less secure on principle nor are contributions by "unknown" developers more of a risk in open source. Benefits of open source: - Open source allows for inspection, independent auditing, and troubleshooting. - Open source can avoid vendor lock-in. - Open source can aid internet standards development. Widely-deployed open source implementations allow proponents of standards drafts to contribute proof of concept implementations without permission or cooperation of vendors. Drawbacks of open source - Both open source and proprietary software require skilled maintenance, which has costs. Proprietary licensed software or appliances typically come with license fees to cover these. In contrast, open source licenses decouple usage by operators from monetary compensation to developers. It is up to operators to consider the financial sustainability of continued maintenance of the open source DNS software they depend upon. Please also consider deploying different software implementations to ensure diversity, as discussed in the diversity section below. ### Networking considerations #### IPv4 and IPv6 **If available, both IPv4 and IPv6 must be deployed.** Large parts of the authoritative DNS are only accessible via IPv4, so the resolver must be able to originate IPv4 queries. Authoritative DNS that is only accessible via IPv6 is very rare. Depending on the connectivity of clients, a resolver may be IPv4-only, IPv6-only, or support IPv4 and IPv6. #### Addressing **Using multiple IP addresses for the service address should be considered.** Using 2 or more IPv4 addresses and 2 or more IPv6 addresses from different RIR will allow resilience in failure at an RIR, either governance, security, or technical. Note that support for multiple addresses for recursive resolvers varies and some clients perform poorly if any address does not respond normally. There is no need to pick an IPv4 address with all octets the same, like 2.2.2.2 or 11.11.11.11. **Publishing a list of back-end addresses used for resolving should be considered.** Publishing a list of back-end addresses used for resolving can be useful for other network & DNS operators (for example, geo-IP location, making sure data is getting to correct places, and so on). #### Anycasting **Anycasting may be considered** Anycasting means routing the same IP prefix to more than one location. As mentioned above for addressing, client support for multiple addresses is not always good; with anycasting you can use a single IP address and have redundancy from different sites. This will often allow you to place sites close to the user - although it is tricky to get optimal routing with BGP. For a resolver service with a single site there is no benefit. For a resolver service with multiple sites, it may be better to configure clients with different IP addresses rather than use anycasting. [RFC7094](https://www.rfc-editor.org/rfc/rfc7094.html) discusses anycast in detail, including references to various other RFC which discuss anycasting in general and to DNS in particular. If a separate prefix is to be used for anycasting, usually this means a /24 in IPv4 and a /48 in IPv6, as those are the smallest sizes that will be widely propagated in BGP. A common practice is to use a covering prefix (/23 in IPv4 or /47 in IPv6) for fallback, and a more-specific prefix (/24 or /48) for the traffic. The more-specific prefix can then be withdrawn to send traffic to a backup site; this will happen automatically if the site is disconnected from routing. #### Ingress Filtering **Ingress Filtering to follow BCP 38 should be deployed.** DNS normally uses UDP traffic, which makes it a common vector of both [reflection](https://en.wikipedia.org/wiki/Reflection_attack) and [amplification](https://www.cisa.gov/news-events/alerts/2014/01/17/udp-based… attacks. To minimize the amount of spoofed traffic that a resolver responds to, the network should be configured as recommended in [BCP 38](https://www.rfc-editor.org/rfc/rfc2827.html). #### RPKI Sign Advertised Routes **Route Advertisements should be signed using RPKI** Using RPKI to sign any route advertisements - either toward authoritative servers or toward DNS clients - is straightforward to do and will reduce the impact of BGP misconfigurations and some BGP hijacking attempts. RPKI validation is also possible, although the effort is greater. It is possible that the hosting provider or the transit provider for your service validates BGP; asking and making this part of your selection criteria is reasonable. #### (D)DoS measures Denial-of-Service (DoS) attacks, both distributed (DDoS) and not are a threat to any Internet service. Network operators for a service providing any DNS service must be prepared for large amounts of attack traffic. In addition to attacks on the service itself, a resolver may be used both as an attack reflector and as an attack amplifier. Active monitoring of network and service usage, careful logging, and a security team that is able to respond to problem reports is necessary. Mitigation techniques will include filtering or rate-limiting traffic, both on the authoritative and client side of the resolver. ### Capacity planning #### Server capacity If using a model that is easy to scale (cloud based, or Kubernetes based, or similar), then getting server capacity correct is largely a question of budgeting. If using a less-flexible model (bare metal for example), then under-estimating will mean problems delivering service. Hardware performance varies widely, as does operating system and resolver performance. Some lab testing will be necessary to estimate the number of systems needed. #### Network capacity Since DNS is mostly UDP-based, it is often easy to generate large amounts of spoofed traffic to and from DNS servers. DNS traffic is small compared to application traffic (videos and other content), but still significant. Authoritative server operators often build their networks and servers to handle 10 times their normal load. Recursive server operators may need to do the same, although the service only accepts traffic from IP addresses that cannot be spoofed (for example users within a network that operated by the same company) then this can be reduced, for example to 3 times normal load. To estimate expected load, the best approach is to examine historical usage for the actual expected users of the system. ### Resilience #### System Diversity In addition to the software considerations above, operators should consider whether to use different server implementations to provide service. This allows continued operation if a critical vulnerability is found in one implementation, by shifting traffic to other implementations. Placing resolvers and control systems in different physical locations will allow continued operation in the event of a disaster or other problem that impacts a single location. In addition, ensuring diverse connectivity to other networks will prevent single points of failure on the network side. Ensuring network diversity may take some care, as it is not always obvious what fate is shared between any given path; this may be physical, virtual, or organizational, and my sometimes be hidden. #### Security In addition to the DNS-specific security considerations, normal security best practices for any Internet service should be followed, including updating software updated regularly, patching software as soon as possible for any known security vulnerabilities, following CERT announcements and so on. #### Certification It may be useful or required for an organization to follow specific certifications, such as ISO or ITIL. These can be government-defined or industry-defined. For end users there is typically not much direct value, but business customers will often look for services that are operated by organizations meeting such standards. ## DNS configuration knobs The DNS is an old protocol that has a lot of settings that can be tweaked. This section reviews these and provides recommendations on which should be used for a resolver. ### DNSSEC validation **DNSSEC validation should be enabled.** For: All DNS resolver operators. DNSSEC validation is the best way to ensure that the answers from the owner of domain name being queried are returned. The root KSK must be updated when it changes. While [RFC5011](https://www.rfc-editor.org/rfc/rfc5011.html) defines an automated way to do this, a resolver operator will probably either manage this trust anchor directly or have it updated via OS updates. [RFC9364](https://www.rfc-editor.org/rfc/rfc9364.html) provides a lot of useful information, and links to further documents about DNSSEC. However, operators usually do not need to know the details, and can simply ensure that DNSSEC validation is enabled in their software; this is usually enabled by default. Resolver software that does not support DNSSEC validation should be avoided. ### DNS Transport Protocols **UDP and TCP must be supported.** For: ALL DNS resolver operators. UDP is what most clients use, and TCP is necessary for DNS answers that are too large for a single UDP packet. [RFC7766](https://www.rfc-editor.org/rfc/rfc7766.html) explains why TCP is necessary in more detail. ### Packet Fragmentation Avoidance **Servers should be configured to avoid fragmentation.** For: ALL DNS resolver operators. Packet fragmentation can cause issues with DNS over UDP, especially over IPv6. These issues can be minimized by choosing implementations that set IP options to avoid this, and by taking care with EDNS0 message sizes. Recommendations are available in [draft-ietf-dnsop-avoid-fragmentation](https://datatracker.ietf.org/doc/draf…. ### Encrypted DNS **DNS-over-TLS (DoT), DNS-over-HTTPS (DoH), and DNS-over-QUIC (DoQ) should be supported.** For: All DNS resolver operators. DoT, DoH, and DoQ are different technologies that all provide an encrypted channel between the resolver and the authoritative server. DoT is the oldest, and provides encrypted DNS using TLS. DoH uses HTTP over TLS as a way to transmit queries and answers, and is widely supported by web browsers. DoQ is the newest, and provides advanced features such as separate streams for each query, avoiding the "head of line" blocking problem common with all protocols layered on top of TCP (such as DoT and DoH). - DoT - [RFC7858](https://www.rfc-editor.org/rfc/rfc7858.html) - DoH - [RFC8484](https://www.rfc-editor.org/rfc/rfc8484.html) - DoQ - [RFC9250](https://www.rfc-editor.org/rfc/rfc9250.html) **Discovery of DNS Designated Resolvers** There are new mechanisms that allow DNS clients to use DNS records to discover encrypted DNS configurations. Resolvers should publish DNS records to assist clients finding encrypted resolvers. - Discovery of Designated Resolvers - [RFC9462](https://www.rfc-editor.org/rfc/rfc9462.html) QUESTION: Do we need to publish certificate in other ways that via the DDR mechanisms? ### QNAME Minimization **QNAME minimization should be enabled.** For: All DNS resolver operators. Using QNAME minimization, a resolver does not send the full name that it is trying to resolver to authoritative servers higher in the DNS hierarchy. So, for example, when querying "atlas.ripe.net" the servers for ".net" would only be asked for "ripe.net". This improves privacy for the end user querying the name. [RFC7816](https://www.rfc-editor.org/rfc/rfc7816.html) covers QNAME minimization. ### Aggressive NSEC caching **Aggressive NSEC caching should be enabled.** For: Public resolver operators. "Aggressive NSEC caching", meaning negative caching based on NSEC and NSEC3 values, can reduce traffic greatly. It is important to protect against random subdomain attacks. This style of caching takes advantage of the way that NSEC and NSEC3 records cover a range of names in a zone. A resolver can know that a query falls within such a range without sending any further queries, by remembering the NSEC or NSEC3 redords that is has seen as answers to earlier queries. Aggressive NSEC caching is almost always a good idea. However enabling this is less important for DNS resolver operators who have a close relationship with users, since they can stop attacks by blocking users or otherwise directly dealing with the source of abusive queries. [RFC8189](https://www.rfc-editor.org/rfc/rfc8189.html) describes negative caching in detail. ### Local Root **Local root should be used.** For: Public resolver operators. Since the root zone is DNSSEC signed, Running a local root has several benefits, but it is an additional component to maintain. For public resolver operators this is definitely worth the cost, but other resolver operators may choose to simply send all queries to the well-distributed root name servers. [RFC8806](https://www.rfc-editor.org/rfc/rfc8806.html) describes local root, including several example configurations. In the future it will be possible to use ZONEMD to validate the copy of the root zone obtained before using it. This is currently being deployed for the root zone, but not yet available. [RFC8976](https://www.rfc-editor.org/rfc/rfc8976.html) describes ZONEMD. ### DNS Cookies **Interoperable DNS Cookies should be supported.** For: Public resolver operators. DNS cookies provide some improved security over plain UDP, and are designed to be more lightweight than TCP. If more than one server is responding for a given IP address, then the Server Secret must be shared by all servers, and the answer must be constructed in a consistent manner by all server implementations. Since client-side support for DNS cookies is not very widespread, and since managing server-side secrets involves some work, the costs may outweigh the benefits for some non-public resolver operators. [RFC7873](https://www.rfc-editor.org/rfc/rfc7873.html) describes DNS cookies, and [RFC9018](https://www.rfc-editor.org/rfc/rfc9018.html) standardizes shared DNS cookies. ### TTL Recommendations **TTL limits may be adjusted.** For: All DNS resolver operators. Software typically defaults to a maximum stored TTL of 1 or 2 days. This may be lowered to reduce the cache size. A lower TTL will mean removing rarely-used records that have long TTL, and should not have much operational impact from a CPU or network point of view, but may save memory. It is possible to set a minimum TTL in many implementations. This is a violation of the DNS protocol, although may be useful to reduce load from records with very low TTL (less than 5 seconds). Note that software may set different maximum and minimum TTL independent of the results that the resolver returns. That may have a significant impact on queries as well, but resolver operators cannot influence that. ### TTL-based Record Pre-Fetch **TTL record pre-fetch should be enabled when available.** For: All DNS resolver operators. Some resolvers have the ability to look up a record before it has expired from cache, in order to refresh the value and extend the TTL. This way there is never a time when the records are missing from the cache. This is not currently standardized, but a form of this was proposed in the IETF as [DNS Hammer](https://datatracker.ietf.org/doc/html/draft-wkumari-dnsop-hammer-03). We recommend turning this feature on if available. ### EDNS Client Subnet (ECS) **ECS may be enabled.** For: All DNS resolver operators. EDNS Client Subnet (ECS) allows the resolver to include information about the IP address of the client querying it when sending messages to authoritative servers. This may allow authoritative servers to provide different answers which are more appropriate for the client. However, ECS will increase the amount of cache space required by resolvers, may reduce DNS performance, and may have privacy implications. A resolver operator that has clients that are limited to a specific region may see no benefit. A resolver operator that has a widely distributed anycast network may not have much benefit from ECS, since the locations that initiate the query will be close to the client. But a resolver operator that answers client queries only from a few locations, and expects clients to come from a wide area, may provide better service for end-users by supporting ECS. EDNS client subnet is described in [RFC7871](https://www.rfc-editor.org/rfc/rfc7871.html), an informational RFC. ### Extended DNS Errors **Extended DNS errors should be enabled.** For: All DNS resolver operators. DNS traditionally provides very broad error reporting, SERVFAIL being the most common. This makes diagnosing and fixing problems difficult. Extended DNS errors provide extra information about failures, for example expired DNSSEC signatures. They also allow resolver operators to report administrative reasons for DNS failures, such as blocks due to legal requirements. [RFC8914](https://www.rfc-editor.org/rfc/rfc8914.html) defines extended DNS errors. ### Negative Trust Anchors **Negative trust anchors may be deployed.** For: All DNS resolver operators. Negative trust anchors (NTA) allow a resolver operator to handle a case where an authoritative server has a DNSSEC problem and becomes inaccessible. They basically disable DNSSEC checking for a domain. When this is warranted is difficult to know with certainty, and will usually requires some manual checking. Since DNSSEC validation is now widespread, DNSSEC failures on the authoritative side will impact many resolvers. Because of these reasons this document does not recommend NTA, but also does not recommend that a deployment avoid NTA if it makes sense for that environment. Negative trust anchors are documented in [RFC7646](https://www.rfc-editor.org/rfc/rfc7646.html). ### DNS Error Reporting **DNS error reporting may be enabled.** For: All DNS resolver operators. DNS error reporting is a way for resolver operators to let authoritative operators know about problems in authoritative servers or zones. It provides little direct value for the resolver operators, but over time should improve the overall quality of the DNS ecosystem. It is neither widely deployed nor standardized, but hopefully will be both soon. Resolver operators are encouraged to enable DNS error reporting when it is available. DNS error reporting is proposed in [draft-ietf-dnsop-dns-error-reporting](https://datatracker.ietf.org/doc/draf…. ### Trust Anchor Reporting **Trust anchor reporting may be enabled.** For: All DNS resolver operators. Trust anchor reporting is a way for resolver operators to convey their DNSSEC trust anchor configuration to the operator of the zone that it is for. For most resolvers this is only the root zone. This information is intended to be used during a root KSK rollover to ensure that it is safe to proceed. In the future ICANN is planning an algorithm roll for the root KSK, and this information could be helpful. Resolver operators are encouraged to enable trust anchor reporting. [RFC8145](https://www.rfc-editor.org/rfc/rfc8145.html) covers trust anchor reporting, in both possibilities available. ## Privacy, Filtering, Transparency ### Privacy & anonymity Operators are advised to apply [RFC8932](https://www.rfc-editor.org/rfc/rfc8932.html) "Recommendations for DNS Privacy Service Operators" as follows: 1. its operational and policy guidance related to DNS encrypted transports and data handling, by applying all "Threat mitigations" (thereby by meeting its level of "minimally compliant") and additionally by applying the "Optimizations" on EDNS Client Subnet listed in section 5.3.1. 2. its framework on a Recursive operator Privacy Statement, by publishing a privacy statement on their website that is compliant with Section 6. #### Logging considerations 1. Public privacy policy: DNS resolvers are recommended to publish their privacy policies transparently on their website. It can be a brief privacy commitment as well or be more elaborate on how the privacy policy was made. (See for example [Cloudflare's statement](https://developers.cloudflare.com/1.1.1.1/privacy/public-dns-res… or [Quad9's privacy page](https://www.quad9.net/service/privacy/).) 2. Third party access to personal data: it seems that the only critical personal data that DNS resolvers collect are IP addresses and the queries that are resolved. The other meta data collected can be used to have an understanding of for example which user accessed which website which can reveal information about a person’s health, lifestyle and other personal preferences (we call this profiling). For example, resolving the website for alcoholics anonymous may tell you something about the health of a person behind an IP address. IP addresses are personally identifiable information. Follow the applicable privacy laws or privacy principles when receiving third party requests to access. Resolvers should only comply with such requests when balancing legitimate third party interest with other fundamental rights. 3. Access to data for researchers: how it is done, who has access and who can request access, how the resolver makes a decision to give access (validated and credible researchers, what they can access and other issues) 4. Data minimization: do not collect personal information not needed for critical operations. Only retain or use what is being asked (the query). If collecting data to make the service more private and secure, explain the rationale for each piece of data (data collection purpose) 5. Ad policy and encryption: explain the ad policy and how it can potentially affect the users privacy. If data is encrypted, explain how it has been encrypted (DoH, DoT, or so on). 6. Data security and retention: when to delete the data and how it is stored ### Filtering and blocking #### Legal blocking: **Legal requests and blocking and filtering laws:** DNS resolvers should not filter content and block access to web-services. When the local law requires blocking, and the law applies to the resolver, the resolver should transparently disclose a list of blocked websites and services. **Community governance of blocklists:** blocklists, if mandatory, have to be audited and assessed by third parties and there should be a right to appeal for those blocked. The Internet community can vet the blocklists from time to time to avoid blocking access to websites that are mistakenly blocked. During crisis - when mistakes can have drastic effects on accessing a critical service - preferably filtering and blocking should not be used. #### RPZ-based filtering Response Policy Zone (RPZ) allows a way to both document specific modifications that resolvers will make to DNS answers, and send the rules to resolvers. Resolvers can be directed to block or modify answers in various ways. Blocklists may be provided by governments, communities, or other parties (for example security firms) using RPZ. This allows updates to occur very quickly. These source must be highly trusted, as changes to blocklists will usually immediately impact user queries. RPZ is not standardized, but there is an IETF draft, [draft-vixie-dnsop-dns-rpz](https://datatracker.ietf.org/doc/draft-vixie-dns…. #### Opt-in/Opt-out Mechanisms End users may choose to use a DNS resolver that filters specific kinds of traffic. For example, they may wish to avoid potential malware web sites. Or resolver operators may be required to default to filtering but allowed for to provide an unfiltered DNS resolver service. Depending on the specific requirements, a resolver service may publish different IP addresses and what type of filtering applies to each address. It is also possible to perform client authentication and authorization, using IP-based authentication, TSIG keys, or client-side TLS certificates. ### Transparency DNS resolvers usually provide transparency reports once a year. The reports inform the public about disclosure of user information and removal of content required by law enforcement and other government agencies. Transparency reports should (to the extent that the law allows) indicate which government agencies and law enforcement agencies request access on what basis. It should also be clear from the transparency reports what kind of data has been requested and if content removal and content blocking have been requested. Categories of data include: Content Data, Basic Subscriber Data, Other Non-Content Data and Content Blocking. #### Voluntary certificates and standards Some DNS resolvers opt for obtaining certificates in security and privacy. Some also undertake audits on their privacy practices. See for example:https://www.cloudflare.com/trust-hub/compliance-resources/ #### Human rights considerations DNS resolvers can opt for declaring their understanding of their responsibilities regarding human rights from the Universal Declaration of Human Rights. Specifically, Quad9 mentions rights to freedoms without distinction made on the basis of country, no interference with privacy, the right to freedom of opinion and expression, the right to peaceful assembly, and the right to freely participate in the cultural life of the community. See [Quad9's Human Rights Considerations](https://www.quad9.net/privacy/human-rights-considerations/) for the full statement. It also invokes other human rights related solutions other than [UDHR](https://www.un.org/en/universal-declaration-human-rights/) such as Articles 8 and 9 of Resolution 42/15 of the United Nations Human Rights Council on the right to privacy in the digital age of 26 September 2019 more directly define the responsibilities of the private sector toward the furtherance of human rights in modern terms. They also follow the Guidelines for Human Rights Protocol and Architecture Consideration of the Human Rights Protocol Considerations Research Group at Internet Research Task Force. The latest version of the IRTF [Guidelines for HRPC](https://tools.ietf.org/html/draft-irtf-hrpc-guidelines) may be considered for all network operators. ## Appendix A: Why Did RIPE Write This Document? There is increasing concern that large open DNS resolvers will become centralised points of DNS operations on the Internet. In order to address this, the European Commission issued the [DNS4EU](https://hadea.ec.europa.eu/calls-proposals/equipping-backbone-networks-high-performance-and-secure-dns-resolution-infrastructures-works_en) proposal. However, such an initiative could lead to centralised guidance or regulation which might interfere with the decentralised way the Internet infrastructure works - including the DNS. See for reference the [RIPE NCC Open House discussion](https://labs.ripe.net/author/chrisb/dns4eu-ripe-ncc-open-house-… on this topic. Rather than attempting to respond to the EC proposal or organize specific DNS resolver deployments, the RIPE community has decided that it is best able to provide advice and guidance. The RIPE Community is well positioned to provide a set of Best Current Practices that operators of Open DNS Resolvers will be encouraged to subscribe to.

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COM zone operational announcement: DNSSEC algorithm rollover
by Wessels, Duane 28 Nov '23

28 Nov '23

Verisign will soon begin the transition to DNSSEC algorithm 13 (ECDSA) for the COM zone. Over the next few days, algorithm 13 signatures will start to appear in the zone, followed by the algorithm 13 DNSKEY records. We expect the DS record for the COM zone to change from algorithm 8 to algorithm 13 on or around December 7. Additional information can be found at our blog post and DNS-OARC presentation URLs below: https://blog.verisign.com/security/dnssec-algorithm-update/ https://indico.dns-oarc.net/event/47/contributions/1012/ We expect no operational impacts for end users, but please feel free to reach out to us with concerns or any observations of anomalous behavior related to this algorithm rollover. DW

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Candidates for the open co-chair position at the DNS WG
by Joao Luis Silva Damas 28 Nov '23

28 Nov '23

Dear all, The period for expression of support is now closed. Thank you to everyone who provided their input. The chairs will present the final outcome tomorrow morning during the DNS WG meeting session at RIPE 87. I would also like to give a big thank you to the three candidates that have come forward. All excellent in my personal opinion. Regards and see you tomorrow at 9:00am Joao Damas Outgoing co-chair DNS WG

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Candidates for the open co-chair position at the DNS WG
by Joao Luis Silva Damas 27 Nov '23

27 Nov '23

Dear all, I am glad to share with you that we have 3 candidates for the co-chair position that will become vacant soon, at RIPE 87. The DNS WG co-chairs hereby solicit expressions of support for your favourite candidate(s) on this mailing list. We will collect all input from the WG up to Monday 27th November (the first day of the RIPE Meeting) and announce the results during the DNS WG session at RIPE 87. The 3 candidates, with their respective platforms, are, I no particular order: ======================================================================== Doris Houser, nominated by Willem Toroop: ----------------- > I would like to propose Doris Hauser as a candidate for the new DNS Working group co-chair. > > Doris (aka Dodo) is an amazing young lady working at nic.at <http://nic.at/>. Doris and I (Willem) were team-mates in the Port 53 Hackathon during the last RIPE 87 in Rotterdam, which was a constructive and inspiring experience. It would be a joy for me and Moritz, and I am sure also for the working group as a whole, to have Doris as the new DNS Working group co-chair. ======================================================================== David Knight ----------------- Dear colleagues, I would like to volunteer to be a co-chair of the RIPE DNS Working Group. I’ve done it before, enjoyed doing it and think I did a reasonable job. My employer supports the time and travel commitment, I’ve attended every meeting in the last 5 years. Thanks for your consideration, Dave ======================================================================== Matthijs Mekking ---------------------- Hi chairs, I would like to volunteer for co-chairing the RIPE DNS working group. It was in the year 2007 that DNS crossed my path. I applied for a job at NLnet Labs to continue my research on IPv6. I was accepted, but I was also tasked with the maintenance of NSD. Promptly, IPv6 was pushed to the background. I learned that NSD is DNS spelled incorrectly. From there, things escalated quickly. I started writing DNS software, researching DNS projects, and developing DNS standards. The protocol took hold of me. I also started participating in IETF, OARC, and RIPE meetings. I learned a lot by attending these gatherings. These meetings are an important part of our job. Here we bring people together, share our experiences, so we can help each other, and improve the technology that we both love and hate. The Covid years made me realize more than ever how vital these meetings are, and I would be happy to contribute to them. For over 15 years I have been working on DNS and DNSSEC. I hope my broad experience can help the existing chairs (who are doing an excellent job already) keeping the DNS working group relevant for the upcoming years. Best regards, Matthijs Mekking ======================================================================== Regards Joao Damas for the DNS WG chairs

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DNS DevRoom at FOSDEM2024 - Call for Participation
by Pieter Lexis 16 Nov '23

16 Nov '23

Hello DNS enthusiasts and other developers, After four earlier successful and packed DNS devrooms, we are happy to announce a half-day DNS devroom at FOSDEM 2024. As with the previous events, we hope to host talks anywhere from hardcore protocol stuff, to practical sessions for programmers that are not directly involved with DNS but may have to deal with DNS in their day to day coding or system administrators responsible for DNS infrastructure. We have been allotted a room on Saturday the 5th of February 2024, the second half of the day. Probably starting around 13:00 (CET). If you have something you’d like to share with your fellow developers, please head to the submission page at https://fosdem.org/submit . Examples of topics are measuring, monitoring, DNS libraries, anecdotes on how you’ve (ab)used the DNS, and group discussions of upcoming technologies. For the upcoming technologies, we're looking for submissions on Applications Doing DNS (ADD), SVCB/HTTPS records and applications thereof, and stub-resolver configuration. Here’s the 2023 schedule, for your inspiration: https://archive.fosdem.org/2023/schedule/track/dns/ . We expect to schedule 30 minutes per talk, including questions, but if you need more or less time, we can discuss this. The deadline for submissions is December 8th 2023. Reach out to dns-devroom-manager(a)fosdem.org if you run into any trouble. this CfP lives online at https://blog.powerdns.com/2023/11/16/fosdem-2024-dns-developer-room-call-fo… - any important changes will be posted at least there See you there! Cheers, The FOSDEM 2024 DNS Devroom organizers

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RIPE 87 DNS-WG Agenda
by Moritz Müller 09 Nov '23

09 Nov '23

Hi everyone, Here’s the agenda for the meeting of the DNS WG at RIPE 87. We’ll be having our meeting Wednesday, 29 November at 9:00 am. - Kick-off and welcoming our new co-chair (5 min) - DNSSEC Non-deployment. What can be done? - Edward Lewis (25 min) - Introducing DELEG - Dave Lawrence (20 min) - Resolver task force update - Shane Kerr (15 min) - IETF DNSOP update - Tim Wicinski (15 min) - DNS update from the RIPE NCC (10 min) We are looking forward seeing you in Rome or online. Moritz on behalf of the DNS-WG co-chairs

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Revised timeline for DNS WG co chair selection
by Joao Luis Silva Damas 07 Nov '23

07 Nov '23

Dear Colleagues, We are re-issuing the call for volunteers for the soon-to-be-vacant co-chair slot. Note the new dates, with the call for candidates extended by one week to Sunday 12th November ************************************************************************************* Please DO NOT reply to this message if you wish to propose a volunteer. ************************************************************************************* Call for RIPE DNS Working Group Chair ------------------------------------------------------ In accordance with the chair selection process we announce that the term of one of our co-chairs (Joao Damas) will expire at the upcoming RIPE Meeting (RIPE 87, near Rome) and we would like to invite volunteers, or nominations for someone to become a co-chair of the DNS working group. Anyone may volunteer, and anyone may be nominated by someone else (we will check with the person for acceptance). Note that having served two terms, in accordance with the selection process Joao is not eligible. To do this, please send a mail to <dns-wg-chairs AT ripe.net <mailto:dns-wg-chairs@ripe.net>> before end of Sunday 12 November 2023 (UTC). Again, please DO NOT send your volunteer/nomination to the DNS WG mailing but rather the dns-wg-chairs mail alias. It would be helpful for candidates to give some words as to why they think they ought to be a co-chair, what new ideas, or improvements they might bring, and so on. We will publish the list of volunteers, along with anything the volunteers wish to include with their nomination, to this mailing list on Monday 13 November 2023. Discussion and support (or opposition) for each candidate can then be offered on the list. At the DNS working group session at RIPE 87, Moritz and Wilhelm hope to announce consensus based on the mailing list discussion. Timeline ———— Tuesday, 5 September 2023 This call for volunteers posted to the dns-wg mail list ###### Sunday, 12 November 2023 Deadline for volunteers/nominations ###### Monday, 13 November 2023 List of candidates and call for support posted to the mail list Monday, 27 November 2023 Deadline for showing support for candidates/volunteers on the mail list Tuesday, 28 November 2023 DNS WG session at RIPE 87 References ---------- The RIPE working group chair job description is included in ripe-692: https://www.ripe.net/publications/docs/ripe-692 The DNS working group chair selection process is documented here: https://www.ripe.net/participate/ripe/wg/dns/dns-wg-chair-selection-process We have 3 co-chairs so the term is 3 years. The current approach was announced on this mailing list on 2018-07-17: https://www.ripe.net/ripe/mail/archives/dns-wg/2018-July/003566.html As always, please feel free to reach out to any of the chairs directly, to us as a group at dns-wg-chairs AT ripe.net <mailto:dns-wg-chairs@ripe.net>, or discuss this or any other any relevant topic on this mailing list.

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DNS-WG at RIPE 87: Call for presentations
by Moritz Müller 06 Nov '23

06 Nov '23

Dear colleagues, It still might feel far away, but RIPE 87, taking place in the Lazio region, is coming closer. The meeting will be held from 27 November to 1 December 2023. This e-mail is our first official call for topics for the RIPE DNS working group session. If you interested in presenting, please send your proposals to dns-wg-chairs(a)ripe.net. Please also indicate how much time you would need for your presentation including Q&A. As usual, both in-person and remote participation in the working group is possible. We plan to send out a first round of notifications beginning of October. Cheers, Moritz — on behalf of the RIPE DNS WG chairs

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Re: [dns-wg] post-mortem for ripe.net DNSSEC problem on 1 November 2023
by Janos Zsako 05 Nov '23

05 Nov '23

Dear Paul, > Please find below the post mortem for the DNSSEC problem that caused > most of RIPE NCC's services to become unavailable yesterday. Thank you very much for the detailed post-mortem. > Please reach out if you have any questions or feedback. I would like to comment on a single item, see below. > New or changed records were still properly signed (363 of > them), which meant that our monitoring, which checks the signature > validity of the SOA record at the zone apex, missed this issue. It may be a good idea to check for the lowest timestamp of signature validity (of the RRSIG records) in the zone. We monitor this for .hu from the beginning (i.e. since we started signing the zone with DNSSEC). Best regards, Janos

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post-mortem for ripe.net DNSSEC problem on 1 November 2023
by Paul de Weerd 04 Nov '23

04 Nov '23

Dear colleagues, Please find below the post mortem for the DNSSEC problem that caused most of RIPE NCC's services to become unavailable yesterday. Please reach out if you have any questions or feedback. Thanks, Paul de Weerd Manager Global Information Infrastructure team RIPE NCC Summary On 1 November, from 10:45 to 12:15 UTC, most names in the ripe.net zone were bogus due to expired DNSSEC signatures being served. This rendered most of the RIPE NCC’s services unreachable. After investigating the issue, we found a typo in a change to our zone where a record had a TTL that was longer (864,000 seconds instead of 86,400) than the refresh interval for RRSIGs (seven days). This caused our signer to stop refreshing signatures and only sign changes to the zone. We are talking to the vendor of our DNSSEC signing solution about this case to see what can be improved on that end, have implemented a pre-commit check to prevent TTLs longer than a day in the ripe.net zone and are looking at improving monitoring for stale signatures to spot issues like this before they cause problems. Impact DNSSEC signatures in the ripe.net zone are valid for 14 days, with our signers configured to resign them after half that time (seven days). On 1 November at 10:45 UTC the signature on several records in the ripe.net zone expired. These records had last been signed on 18 October and were due to be re-signed on the 25th. However, due to a problem with the TTL on one record, our signer stopped re-signing records in the zone on 25 October. This resulted in the expiry of 11,026 out of 11,389 records on 1 November. New or changed records were still properly signed (363 of them), which meant that our monitoring, which checks the signature validity of the SOA record at the zone apex, missed this issue. Because our internal resolvers are configured for DNSSEC validation, the impact was rather immediate for staff, as many internal services broke due to this issue. After first dismissing some alternative causes, we quickly found the problem was with expired signatures in the ripe.net zone, so we turned our attention to our signers. At the same time, we temporarily disabled DNSSEC validation on our internal resolvers so we could more easily access our own systems while troubleshooting. Resolution While debugging, we found that the rrsig-refresh option that we configured to seven days (half the value of the rrsig-lifetime option of 14 days) was likely involved, logs showed: info: [ripe.net.] DNSSEC, signing zone error: [ripe.net.] DNSSEC, rrsig-refresh too low to prevent expired RRSIGs in resolver caches info: [ripe.net.] DNSSEC, next signing at 2023-10-25T10:02:02+0000 error: [ripe.net.] zone event 're-sign' failed (invalid parameter) At 12:14 UTC we removed that option from our configuration and we could sign the zone again. The freshly signed zone was pushed out and went live a little bit later, which meant that at 12:15 UTC our services were available again for most users. Unfortunately, some users kept seeing problems for several hours after we restored the signatures. Root cause After further investigation we found that the change that triggered this problem introduced a record in the ripe.net zone with a TTL of 864,000 (ten days). Because this TTL is longer than our rrsig-refresh configuration, this could lead to cases where a resolver’s cache contains the record with an expired signature. The signer software rightfully complained about this. We were surprised to find it then stopped refreshing signatures for all records in the zone that didn’t change. Future steps During the incident and the aftermath we identified a few changes that we want to make to improve the resiliency of our setup and allow us to find cases like these before they become problems. Our current RRSIG freshness monitoring did not catch this case, because the records we monitor still had valid and recent signatures, so we are considering what we can do to cover this situation. We have also improved our zone-editing pipeline to catch typos or misconfigurations for TTL values. Next to that, the problem also affected our ability to communicate internally, as our internal chat system was unresolvable too. We have some means of out-of-band communication, but will review how we can improve that. Additionally, while the status.ripe.net website is hosted on separate infrastructure, the fact that it is also in the ripe.net domain meant that it was just as unreachable as our other services. We will evaluate this approach and see how we can improve on it. Timeline (times in UTC) 25 October 08:52 a record was added to the ripe.net zone with a TTL of 10 days 08:53 knot incrementally signs ripe.net successfully 09:02 knot fails to sign the ripe.net zone for the first time 1 November 10:45 ripe.net signatures expire and many records go bogus 11:27 DNSSEC validation on internal resolvers was disabled 12:14 changed configuration and manually re-signed zone 12:15 ripe.net zone has new valid signatures 12:38 DNSSEC validation on internal resolvers is re-enabled 2 November 08:39 typo in TTL fixed, bringing it back to 86,400 seconds as intended 08:39 added check in pipeline to detect too large TTL values

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