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The edns-tcp-keepalive EDNS0 Option (RFC7828) Disclosure Number: IPCOM000245780D
Original Publication Date: 2016-Apr-01
Included in the Prior Art Database: 2016-Apr-07
Document File: 22 page(s) / 24K

Publishing Venue

Internet Society Requests For Comment (RFCs)

Related People

P. Wouters: AUTHOR [+4]


DNS messages between clients and servers may be received over either UDP or TCP [RFC1035]. Historically, DNS clients used APIs that only facilitated sending and receiving a single query over either UDP or TCP. New APIs and deployment of DNSSEC validating resolvers on hosts that in the past were using stub resolving only is increasing the DNS client base that prefer using long-lived TCP connections. Long-lived TCP connections can result in lower request latency than the case where UDP transport is used and truncated responses are received. This is because clients that retry over TCP following a truncated UDP response typically only use the TCP session for a single (request, response) pair, continuing with UDP transport for subsequent queries.

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Internet Engineering Task Force (IETF)                        P. Wouters Request for Comments: 7828                                       Red Hat Category: Standards Track                                       J. Abley ISSN: 2070-1721                                                Dyn, Inc.                                                             S. Dickinson                                                                  Sinodun                                                                R. Bellis                                                                      ISC                                                               April 2016

                   The edns-tcp-keepalive EDNS0 Option


   DNS messages between clients and servers may be received over either    UDP or TCP.  UDP transport involves keeping less state on a busy    server, but can cause truncation and retries over TCP.  Additionally,    UDP can be exploited for reflection attacks.  Using TCP would reduce    retransmits and amplification.  However, clients commonly use TCP    only for retries and servers typically use idle timeouts on the order    of seconds.

   This document defines an EDNS0 option ("edns-tcp-keepalive") that    allows DNS servers to signal a variable idle timeout.  This    signalling encourages the use of long-lived TCP connections by    allowing the state associated with TCP transport to be managed    effectively with minimal impact on the DNS transaction time.

Status of This Memo

   This is an Internet Standards Track document.

   This document is a product of the Internet Engineering Task Force    (IETF).  It represents the consensus of the IETF community.  It has    received public review and has been approved for publication by the    Internet Engineering Steering Group (IESG).  Further information on    Internet Standards is available in Section 2 of RFC 5741.

   Information about the current status of this document, any errata,    and how to provide feedback on it may be obtained at

Wouters, et al.              Standards Track                    [Page 1]
 RFC 7828           The edns-tcp-keepalive EDNS0 Option        April 2016

 Copyright Notice

   Copyright (c) 2016 IETF Trust and the persons identified as the    document authors.  All rights reserved.

   This document is subject to BCP 78 and...