draft-ietf-dnsop-dns-tcp-requirements-02.txt   draft-ietf-dnsop-dns-tcp-requirements-03.txt 
Domain Name System Operations J. Kristoff Domain Name System Operations J. Kristoff
Internet-Draft DePaul University Internet-Draft DePaul University
Updates: 1123 (if approved) D. Wessels Updates: 1123 (if approved) D. Wessels
Intended status: Best Current Practice Verisign Intended status: Best Current Practice Verisign
Expires: November 17, 2018 May 16, 2018 Expires: July 6, 2019 January 2, 2019
DNS Transport over TCP - Operational Requirements DNS Transport over TCP - Operational Requirements
draft-ietf-dnsop-dns-tcp-requirements-02 draft-ietf-dnsop-dns-tcp-requirements-03
Abstract Abstract
This document encourages the practice of permitting DNS messages to This document encourages the practice of permitting DNS messages to
be carried over TCP on the Internet. It also considers the be carried over TCP on the Internet. It also considers the
consequences with this form of DNS communication and the potential consequences with this form of DNS communication and the potential
operational issues that can arise when this best common practice is operational issues that can arise when this best common practice is
not upheld. not upheld.
Status of This Memo Status of This Memo
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Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
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material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on November 17, 2018. This Internet-Draft will expire on July 6, 2019.
Copyright Notice Copyright Notice
Copyright (c) 2018 IETF Trust and the persons identified as the Copyright (c) 2019 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
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described in the Simplified BSD License. described in the Simplified BSD License.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Requirements Language . . . . . . . . . . . . . . . . . . 3 1.1. Requirements Language . . . . . . . . . . . . . . . . . . 3
2. Background . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Background . . . . . . . . . . . . . . . . . . . . . . . . . 3
2.1. Uneven Transport Usage and Preference . . . . . . . . . . 3 2.1. Uneven Transport Usage and Preference . . . . . . . . . . 4
2.2. Waiting for Large Messages and Reliability . . . . . . . 4 2.2. Waiting for Large Messages and Reliability . . . . . . . 4
2.3. EDNS0 . . . . . . . . . . . . . . . . . . . . . . . . . . 4 2.3. EDNS0 . . . . . . . . . . . . . . . . . . . . . . . . . . 5
2.4. Fragmentation and Truncation . . . . . . . . . . . . . . 5 2.4. Fragmentation and Truncation . . . . . . . . . . . . . . 5
2.5. "Only Zone Transfers Use TCP" . . . . . . . . . . . . . . 6 2.5. "Only Zone Transfers Use TCP" . . . . . . . . . . . . . . 6
3. DNS over TCP Requirements . . . . . . . . . . . . . . . . . . 6 3. DNS over TCP Requirements . . . . . . . . . . . . . . . . . . 7
4. Network and System Considerations . . . . . . . . . . . . . . 8 4. Network and System Considerations . . . . . . . . . . . . . . 8
4.1. Connection Admission . . . . . . . . . . . . . . . . . . 8 4.1. Connection Admission . . . . . . . . . . . . . . . . . . 8
4.2. Connection Management . . . . . . . . . . . . . . . . . . 9 4.2. Connection Management . . . . . . . . . . . . . . . . . . 9
4.3. Connection Termination . . . . . . . . . . . . . . . . . 9 4.3. Connection Termination . . . . . . . . . . . . . . . . . 10
5. DNS over TCP Filtering Risks . . . . . . . . . . . . . . . . 10 5. DNS over TCP Filtering Risks . . . . . . . . . . . . . . . . 10
5.1. DNS Wedgie . . . . . . . . . . . . . . . . . . . . . . . 10 5.1. DNS Wedgie . . . . . . . . . . . . . . . . . . . . . . . 11
5.2. DNS Root Zone KSK Rollover . . . . . . . . . . . . . . . 11 5.2. DNS Root Zone KSK Rollover . . . . . . . . . . . . . . . 11
5.3. DNS-over-TLS . . . . . . . . . . . . . . . . . . . . . . 11 5.3. DNS-over-TLS . . . . . . . . . . . . . . . . . . . . . . 11
6. Logging and Monitoring . . . . . . . . . . . . . . . . . . . 11 6. Logging and Monitoring . . . . . . . . . . . . . . . . . . . 12
7. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 12 7. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 12
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 12 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 12
9. Security Considerations . . . . . . . . . . . . . . . . . . . 12 9. Security Considerations . . . . . . . . . . . . . . . . . . . 12
10. Privacy Considerations . . . . . . . . . . . . . . . . . . . 12 10. Privacy Considerations . . . . . . . . . . . . . . . . . . . 13
11. References . . . . . . . . . . . . . . . . . . . . . . . . . 13 11. References . . . . . . . . . . . . . . . . . . . . . . . . . 13
11.1. Normative References . . . . . . . . . . . . . . . . . . 13 11.1. Normative References . . . . . . . . . . . . . . . . . . 13
11.2. Informative References . . . . . . . . . . . . . . . . . 13 11.2. Informative References . . . . . . . . . . . . . . . . . 13
Appendix A. Standards Related to DNS Transport over TCP . . . . 17 Appendix A. Standards Related to DNS Transport over TCP . . . . 18
A.1. TODO - additional, relevant RFCs . . . . . . . . . . . . 17 A.1. TODO - additional, relevant RFCs . . . . . . . . . . . . 18
A.2. IETF RFC 5936 - DNS Zone Transfer Protocol (AXFR) . . . . 17 A.2. IETF RFC 5936 - DNS Zone Transfer Protocol (AXFR) . . . . 18
A.3. IETF RFC 6304 - AS112 Nameserver Operations . . . . . . . 17 A.3. IETF RFC 6304 - AS112 Nameserver Operations . . . . . . . 18
A.4. IETF RFC 6762 - Multicast DNS . . . . . . . . . . . . . . 17 A.4. IETF RFC 6762 - Multicast DNS . . . . . . . . . . . . . . 18
A.5. IETF RFC 6950 - Architectural Considerations on A.5. IETF RFC 6950 - Architectural Considerations on
Application Features in the DNS . . . . . . . . . . . . . 18 Application Features in the DNS . . . . . . . . . . . . . 18
A.6. IETF RFC 7477 - Child-to-Parent Synchronization in DNS . 18 A.6. IETF RFC 7477 - Child-to-Parent Synchronization in DNS . 18
A.7. IETF RFC 7720 - DNS Root Name Service Protocol and A.7. IETF RFC 7720 - DNS Root Name Service Protocol and
Deployment Requirements . . . . . . . . . . . . . . . . . 18 Deployment Requirements . . . . . . . . . . . . . . . . . 19
A.8. IETF RFC 7766 - DNS Transport over TCP - Implementation A.8. IETF RFC 7766 - DNS Transport over TCP - Implementation
Requirements . . . . . . . . . . . . . . . . . . . . . . 18 Requirements . . . . . . . . . . . . . . . . . . . . . . 19
A.9. IETF RFC 7828 - The edns-tcp-keepalive EDNS0 Option . . . 18 A.9. IETF RFC 7828 - The edns-tcp-keepalive EDNS0 Option . . . 19
A.10. IETF RFC 7858 - Specification for DNS over Transport A.10. IETF RFC 7858 - Specification for DNS over Transport
Layer Security (TLS) . . . . . . . . . . . . . . . . . . 18 Layer Security (TLS) . . . . . . . . . . . . . . . . . . 19
A.11. IETF RFC 7873 - Domain Name System (DNS) Cookies . . . . 19 A.11. IETF RFC 7873 - Domain Name System (DNS) Cookies . . . . 19
A.12. IETF RFC 7901 - CHAIN Query Requests in DNS . . . . . . . 19 A.12. IETF RFC 7901 - CHAIN Query Requests in DNS . . . . . . . 20
A.13. IETF RFC 8027 - DNSSEC Roadblock Avoidance . . . . . . . 19 A.13. IETF RFC 8027 - DNSSEC Roadblock Avoidance . . . . . . . 20
A.14. IETF RFC 8094 - DNS over Datagram Transport Layer A.14. IETF RFC 8094 - DNS over Datagram Transport Layer
Security (DTLS) . . . . . . . . . . . . . . . . . . . . . 19 Security (DTLS) . . . . . . . . . . . . . . . . . . . . . 20
A.15. IETF RFC 8162 - Using Secure DNS to Associate A.15. IETF RFC 8162 - Using Secure DNS to Associate
Certificates with Domain Names for S/MIME . . . . . . . . 19 Certificates with Domain Names for S/MIME . . . . . . . . 20
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 20 A.16. IETF RFC 8324 - DNS Privacy, Authorization, Special Uses,
Encoding, Characters, Matching, and Root Structure: Time
for Another Look? . . . . . . . . . . . . . . . . . . . . 20
A.17. IETF RFC 8467 - Padding Policies for Extension Mechanisms
for DNS (EDNS(0)) . . . . . . . . . . . . . . . . . . . . 21
A.18. IETF RFC 8483 - Yeti DNS Testbed . . . . . . . . . . . . 21
A.19. IETF RFC 8484 - DNS Queries over HTTPS (DoH) . . . . . . 21
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 21
1. Introduction 1. Introduction
DNS messages may be delivered using UDP or TCP communications. While DNS messages may be delivered using UDP or TCP communications. While
most DNS transactions are carried over UDP, some operators have been most DNS transactions are carried over UDP, some operators have been
led to believe that any DNS over TCP traffic is unwanted or led to believe that any DNS over TCP traffic is unwanted or
unnecessary for general DNS operation. As usage and features have unnecessary for general DNS operation. As usage and features have
evolved, TCP transport has become increasingly important for correct evolved, TCP transport has become increasingly important for correct
and safe operation of the Internet DNS. Reflecting modern usage, the and safe operation of the Internet DNS. Reflecting modern usage, the
DNS standards were recently updated to declare support for TCP is now DNS standards were recently updated to declare support for TCP is now
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resources. If the number and frequency of these truncated answers resources. If the number and frequency of these truncated answers
are sufficiently high, we refer to the steady-state of lost resources are sufficiently high, we refer to the steady-state of lost resources
as a result a "DNS" wedgie". A DNS wedgie is often not easily or as a result a "DNS" wedgie". A DNS wedgie is often not easily or
completely mitigated by the affected DNS resolver operator. completely mitigated by the affected DNS resolver operator.
5.2. DNS Root Zone KSK Rollover 5.2. DNS Root Zone KSK Rollover
Recent plans for a new root zone DNSSEC KSK have highlighted a Recent plans for a new root zone DNSSEC KSK have highlighted a
potential problem in retrieving the keys [LEWIS]. Some packets in potential problem in retrieving the keys [LEWIS]. Some packets in
the KSK rollover process will be larger than 1280 bytes, the IPv6 the KSK rollover process will be larger than 1280 bytes, the IPv6
minimum MTU for links carrying IPv6 traffic.[RFC2460] While studies minimum MTU for links carrying IPv6 traffic.[RFC2460] While studies
have shown that problems due to fragment filtering or an inability to have shown that problems due to fragment filtering or an inability to
generate and receive these larger messages are negligible, any DNS generate and receive these larger messages are negligible, any DNS
server that is unable to receive large DNS over UDP messages or server that is unable to receive large DNS over UDP messages or
perform DNS over TCP may experience severe disruption of DNS service perform DNS over TCP may experience severe disruption of DNS service
if performing DNSSEC validation. if performing DNSSEC validation.
TODO: Is this "overcome by events" now? We've had 1414 byte DNSKEY TODO: Is this "overcome by events" now? We've had 1414 byte DNSKEY
responses at the three ZSK rollover periods since KSK-2017 became responses at the three ZSK rollover periods since KSK-2017 became
published in the root zone. published in the root zone.
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[RFC8094] Reddy, T., Wing, D., and P. Patil, "DNS over Datagram [RFC8094] Reddy, T., Wing, D., and P. Patil, "DNS over Datagram
Transport Layer Security (DTLS)", RFC 8094, Transport Layer Security (DTLS)", RFC 8094,
DOI 10.17487/RFC8094, February 2017, DOI 10.17487/RFC8094, February 2017,
<https://www.rfc-editor.org/info/rfc8094>. <https://www.rfc-editor.org/info/rfc8094>.
[RFC8162] Hoffman, P. and J. Schlyter, "Using Secure DNS to [RFC8162] Hoffman, P. and J. Schlyter, "Using Secure DNS to
Associate Certificates with Domain Names for S/MIME", Associate Certificates with Domain Names for S/MIME",
RFC 8162, DOI 10.17487/RFC8162, May 2017, RFC 8162, DOI 10.17487/RFC8162, May 2017,
<https://www.rfc-editor.org/info/rfc8162>. <https://www.rfc-editor.org/info/rfc8162>.
[RFC8324] Klensin, J., "DNS Privacy, Authorization, Special Uses,
Encoding, Characters, Matching, and Root Structure: Time
for Another Look?", RFC 8324, DOI 10.17487/RFC8324,
February 2018, <https://www.rfc-editor.org/info/rfc8324>.
[RFC8467] Mayrhofer, A., "Padding Policies for Extension Mechanisms
for DNS (EDNS(0))", RFC 8467, DOI 10.17487/RFC8467,
October 2018, <https://www.rfc-editor.org/info/rfc8467>.
[RFC8483] Song, L., Ed., Liu, D., Vixie, P., Kato, A., and S. Kerr,
"Yeti DNS Testbed", RFC 8483, DOI 10.17487/RFC8483,
October 2018, <https://www.rfc-editor.org/info/rfc8483>.
[RFC8484] Hoffman, P. and P. McManus, "DNS Queries over HTTPS
(DoH)", RFC 8484, DOI 10.17487/RFC8484, October 2018,
<https://www.rfc-editor.org/info/rfc8484>.
[RRL] Vixie, P. and V. Schryver, "DNS Response Rate Limiting [RRL] Vixie, P. and V. Schryver, "DNS Response Rate Limiting
(DNS RRL)", ISC-TN 2012-1 Draft1, April 2012. (DNS RRL)", ISC-TN 2012-1 Draft1, April 2012.
[Stevens] Stevens, W., Fenner, B., and A. Rudoff, "UNIX Network [Stevens] Stevens, W., Fenner, B., and A. Rudoff, "UNIX Network
Programming Volume 1, Third Edition: The Sockets Programming Volume 1, Third Edition: The Sockets
Networking API", November 2003. Networking API", November 2003.
[TDNS] Zhu, L., Heidemann, J., Wessels, D., Mankin, A., and N. [TDNS] Zhu, L., Heidemann, J., Wessels, D., Mankin, A., and N.
Somaiya, "Connection-oriented DNS to Improve Privacy and Somaiya, "Connection-oriented DNS to Improve Privacy and
Security", 2015. Security", 2015.
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A.15. IETF RFC 8162 - Using Secure DNS to Associate Certificates with A.15. IETF RFC 8162 - Using Secure DNS to Associate Certificates with
Domain Names for S/MIME Domain Names for S/MIME
This experimental specification [RFC8162] describes a technique to This experimental specification [RFC8162] describes a technique to
authenticate user X.509 certificates in an S/MIME system via the DNS. authenticate user X.509 certificates in an S/MIME system via the DNS.
The document points out that the new experimental resource record The document points out that the new experimental resource record
types are expected to carry large payloads, resulting in the types are expected to carry large payloads, resulting in the
suggestion that "applications SHOULD use TCP -- not UDP -- to perform suggestion that "applications SHOULD use TCP -- not UDP -- to perform
queries for the SMIMEA resource record." queries for the SMIMEA resource record."
A.16. IETF RFC 8324 - DNS Privacy, Authorization, Special Uses,
Encoding, Characters, Matching, and Root Structure: Time for
Another Look?
An informational document [RFC8324] that briefly discusses the common
role and challenges of DNS over TCP throughout the history of DNS.
A.17. IETF RFC 8467 - Padding Policies for Extension Mechanisms for DNS
(EDNS(0))
An experimental document [RFC8467] reminds implementers to consider
the underlying transport protocol (e.g. TCP) when calculating the
padding length when artificially increasing the DNS message size with
an EDNS(0) padding option.
A.18. IETF RFC 8483 - Yeti DNS Testbed
This informational document [RFC8483] describes a testbed environment
that highlights some DNS over TCP behaviors, including issues
involving packet fragmentation and operational requirements for TCP
stream assembly in order to conduct DNS measurement and analysis.
A.19. IETF RFC 8484 - DNS Queries over HTTPS (DoH)
This standards track document [RFC8484] defines a protocol for
sending DNS queries and responses over HTTPS. This specification
assumes TLS and TCP for the underlying security and transport layers
respectively. Self-described as a a technique that more closely
resembles a tunneling mechanism, DoH nevertheless likely implies DNS
over TCP in some sense if not directly.
Authors' Addresses Authors' Addresses
John Kristoff John Kristoff
DePaul University DePaul University
Chicago, IL 60604 Chicago, IL 60604
US US
Phone: +1 312 493 0305 Phone: +1 312 493 0305
Email: jtk@depaul.edu Email: jtk@depaul.edu
URI: https://aharp.iorc.depaul.edu URI: https://aharp.iorc.depaul.edu
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