Network Working Group W. Kumari Internet-Draft Google Intended status: Informational P. Hoffman Expires: May 15, 2015 VPN Consortium November 11, 2014 Decreasing Access Time to Root Servers by Running One on Loopback draft-wkumari-dnsop-root-loopback-01 Abstract Some DNS recursive resolvers have longer-than-desired round trip times to the closest DNS root server. Such resolvers can greatly decrease the round trip time by running a copy of the full root zone on a loopback address (such as 127.0.0.1). This document shows how to start and maintain such a copy of the root zone in a manner that is secure for the operator of the recursive resolver and does not pose a threat to other users of the DNS. 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 http://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 May 15, 2015. Copyright Notice Copyright (c) 2014 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 (http://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must Kumari & Hoffman Expires May 15, 2015 [Page 1] Internet-Draft Running Root on Loopback November 2014 include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 1.1. Requirements Notation . . . . . . . . . . . . . . . . . . 3 2. Requirements . . . . . . . . . . . . . . . . . . . . . . . . 3 3. Operation of the Root Zone on the Loopback Address . . . . . 3 4. Using the Root Zone Server on the Loopback Address . . . . . 4 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4 6. Security Considerations . . . . . . . . . . . . . . . . . . . 4 7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 4 8. Normative References . . . . . . . . . . . . . . . . . . . . 5 Appendix A. Current Sources of the Root Zone . . . . . . . . . . 5 Appendix B. Example Configurations of Common Implementations . . 5 B.1. Example Configuration: BIND 9.9 . . . . . . . . . . . . . 5 B.2. Example Configuration: Unbound 1.4 and NSD 4 . . . . . . 6 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 7 1. Introduction DNS recursive resolvers have to answer all queries from their customers, even those which are for domain names that do not exist. For each queried name that has a top level domain (TLD) that is not in the recursive resolver's cache, the resolver must send a query to a root server to get the information for that TLD, or to find out that the TLD does not exist. If there is a slow path between the recursive resolver and the closest root server, getting slow responses to these queries has a negative effect on the resolver's customers. This document describes a method for the operator of a recursive resolver to greatly speed these queries. The basic idea is to create an up-to-date root zone server on a loopback address on the same host as the recursive server, and that server is used when the recursive resolver uses for looking up root information. The recursive resolver validates all responses from the root server on the loopback address, just as it would all responses from a remote root server. The primary goal of this design is to provide faster negative responses to stub resolver queries that contain junk queries. This design will probably have little effect on getting faster positive responses to stub resolver for good queries on TLDs, because the data for those zones is usually long-lived and already in the cache of the recursive resolver; thus, getting faster positive responses is a non- goal of this design. Kumari & Hoffman Expires May 15, 2015 [Page 2] Internet-Draft Running Root on Loopback November 2014 This design explicitly only allows the new root zone server to be run on a loopback address. This prevents the server from serving authoritative answers to any system other than the recursive resolver. This design requires the addition of authoritative name server software running on the same machine as the recursive resolver. Thus, recursive resolver software such as BIND will not need to add much new functionality, but recursive resolver software such as Unbound will need to be able to talk to an authoritative server (such as NSD) running on the same host. 1.1. Requirements Notation The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in [RFC2119]. 2. Requirements In the discussion below, the term "legacy operation" means the way that a recursive resolver acts when it is not using the mechanism describe in this document, namely as a normal validating recursive resolver with no other special features. In order to implement the mechanism described in this document: o The system MUST be able to validate a zone with DNSSEC. o The system MUST have an up-to-date copy of the DNS root key. o The system MUST be able to retrieve a copy of the entire root zone (including all DNSSEC-related records). o The system MUST be able to run an authoritative server on one of the IPv4 loopback addresses (that is, an address in the range 127/8). 3. Operation of the Root Zone on the Loopback Address The operation of an authoritative server for the root in the system described here can be done separately from the operation of the recursive resolver. The steps to set up the root zone are: 1. Retrieve a copy of the root zone. (See Appendix A for some current locations of sources.) Kumari & Hoffman Expires May 15, 2015 [Page 3] Internet-Draft Running Root on Loopback November 2014 2. Start the authoritative server with the root zone on a loopback address that is not in use. This would typically be 127.0.0.1, but if that address is in use, any address in 127/8 is acceptable. The contents of the root zone must be refreshed using the timers from the SOA record in root zone, as described in [RFC1035]. If the contents of the zone cannot be refreshed before the expire time, the server MUST return a SERVFAIL error response for all queries until the zone can be successfully be set up again. 4. Using the Root Zone Server on the Loopback Address A recursive resolver that wants to use a root zone server operating as described in Section 3 simply specifies the local address as the place to look when it is looking for information from the root. All responses from the rootserver on localhost must be validated using DNSSEC. Note that using this configuration will cause the recursive resolver to fail if the local root zone server fails. 5. IANA Considerations This document requires no action from the IANA. 6. Security Considerations A system that does not follow the DNSSEC-related requirements given in Section 2 can be fooled into giving bad responses in the same way as any recursive resolver that does not do DNSSEC validation on responses from a remote root server. 7. Acknowledgements The editors fully acknowledge that this is not a new concept, and that we have chatted with many people about this. In fact, this concept may already have been implemented without the knowledge of the authors. For example, Bill Manning described something similar in his doctoral dissertation in 2013. Evan Hunt contributed greatly by finding some flaws in the logic in the -00 draft, and by offering a BIND configuration that works with the requirements. Kumari & Hoffman Expires May 15, 2015 [Page 4] Internet-Draft Running Root on Loopback November 2014 8. Normative References [RFC1035] Mockapetris, P., "Domain names - implementation and specification", STD 13, RFC 1035, November 1987. [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. Appendix A. Current Sources of the Root Zone The root zone can be retrieved from anywhere as long as it comes with all the DNSSEC records needed for validation. Currently, there are three sources of the root zone supported by ICANN: o From ICANN via FTP at ftp://rs.internic.net/domain/root.zone o From ICANN via HTTP at http://www.internic.net/domain/root.zone o From ICANN by AXFR from DNS servers at xfr.lax.dns.icann.org and xfr.cjr.dns.icann.org Currently, the root can be retrieved by zone transfer from the following root server operators: o b.root-servers.net o c.root-servers.net o f.root-servers.net o g.root-servers.net o k.root-servers.net Appendix B. Example Configurations of Common Implementations This section shows fragments of configurations for some popular recursive server software that is believed to correctly implement the requirements given in this document. B.1. Example Configuration: BIND 9.9 Kumari & Hoffman Expires May 15, 2015 [Page 5] Internet-Draft Running Root on Loopback November 2014 view root { match-destinations { 127.12.12.12; }; zone "." { type slave; file "rootzone.db"; notify no; masters { 192.228.79.201; # b.root-servers.net 192.33.4.12; # c.root-servers.net 192.5.5.241; # f.root-servers.net 192.112.36.4; # g.root-servers.net 193.0.14.129; # k.root-servers.net }; }; }; view recursive { dnssec-validation auto; allow-recursion { any; }; recursion yes; zone "." { type static-stub; server-addresses { 127.12.12.12; }; }; }; B.2. Example Configuration: Unbound 1.4 and NSD 4 Kumari & Hoffman Expires May 15, 2015 [Page 6] Internet-Draft Running Root on Loopback November 2014 # Configuration for Unbound server: do-not-query-localhost: no stub-zone: name: "." stub-prime: no stub-addr: 127.12.12.12 # Configuration for NSD server: ip-address: 127.12.12.12 zone: name: "." request-xfr: 192.228.79.201 NOKEY # b.root-servers.net request-xfr: 192.33.4.12 NOKEY # c.root-servers.net request-xfr: 192.5.5.241 NOKEY # f.root-servers.net request-xfr: 192.112.36.4 NOKEY # g.root-servers.net request-xfr: 193.0.14.129 NOKEY # k.root-servers.net Authors' Addresses Warren Kumari Google Email: Warren@kumari.net Paul Hoffman VPN Consortium Email: paul.hoffman@vpnc.org Kumari & Hoffman Expires May 15, 2015 [Page 7]