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rfc:rfc8305

Internet Engineering Task Force (IETF) D. Schinazi Request for Comments: 8305 T. Pauly Obsoletes: 6555 Apple Inc. Category: Standards Track December 2017 ISSN: 2070-1721

  Happy Eyeballs Version 2: Better Connectivity Using Concurrency

Abstract

 Many communication protocols operating over the modern Internet use
 hostnames.  These often resolve to multiple IP addresses, each of
 which may have different performance and connectivity
 characteristics.  Since specific addresses or address families (IPv4
 or IPv6) may be blocked, broken, or sub-optimal on a network, clients
 that attempt multiple connections in parallel have a chance of
 establishing a connection more quickly.  This document specifies
 requirements for algorithms that reduce this user-visible delay and
 provides an example algorithm, referred to as "Happy Eyeballs".  This
 document obsoletes the original algorithm description in RFC 6555.

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 7841.
 Information about the current status of this document, any errata,
 and how to provide feedback on it may be obtained at
 https://www.rfc-editor.org/info/rfc8305.

Schinazi & Pauly Standards Track [Page 1] RFC 8305 Happy Eyeballs v2 December 2017

Copyright Notice

 Copyright (c) 2017 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 Components extracted from this document must
 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  . . . . . . . . . . . . . . . . . . . . . . . .   3
   1.1.  Requirements Language . . . . . . . . . . . . . . . . . .   3
 2.  Overview  . . . . . . . . . . . . . . . . . . . . . . . . . .   4
 3.  Hostname Resolution Query Handling  . . . . . . . . . . . . .   4
   3.1.  Handling Multiple DNS Server Addresses  . . . . . . . . .   5
 4.  Sorting Addresses . . . . . . . . . . . . . . . . . . . . . .   6
 5.  Connection Attempts . . . . . . . . . . . . . . . . . . . . .   7
 6.  DNS Answer Changes during Happy Eyeballs Connection Setup . .   8
 7.  Supporting IPv6-Only Networks with NAT64 and DNS64  . . . . .   8
   7.1.  IPv4 Address Literals . . . . . . . . . . . . . . . . . .   8
   7.2.  Hostnames with Broken AAAA Records  . . . . . . . . . . .   9
   7.3.  Virtual Private Networks  . . . . . . . . . . . . . . . .  10
 8.  Summary of Configurable Values  . . . . . . . . . . . . . . .  10
 9.  Limitations . . . . . . . . . . . . . . . . . . . . . . . . .  11
   9.1.  Path Maximum Transmission Unit Discovery  . . . . . . . .  11
   9.2.  Application Layer . . . . . . . . . . . . . . . . . . . .  11
   9.3.  Hiding Operational Issues . . . . . . . . . . . . . . . .  11
 10. Security Considerations . . . . . . . . . . . . . . . . . . .  12
 11. IANA Considerations . . . . . . . . . . . . . . . . . . . . .  12
 12. References  . . . . . . . . . . . . . . . . . . . . . . . . .  12
   12.1.  Normative References . . . . . . . . . . . . . . . . . .  12
   12.2.  Informative References . . . . . . . . . . . . . . . . .  13
 Appendix A.  Differences from RFC 6555  . . . . . . . . . . . . .  14
 Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . .  15
 Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  15

Schinazi & Pauly Standards Track [Page 2] RFC 8305 Happy Eyeballs v2 December 2017

1. Introduction

 Many communication protocols operating over the modern Internet use
 hostnames.  These often resolve to multiple IP addresses, each of
 which may have different performance and connectivity
 characteristics.  Since specific addresses or address families (IPv4
 or IPv6) may be blocked, broken, or sub-optimal on a network, clients
 that attempt multiple connections in parallel have a chance of
 establishing a connection more quickly.  This document specifies
 requirements for algorithms that reduce this user-visible delay and
 provides an example algorithm.
 This document defines the algorithm for "Happy Eyeballs", a technique
 for reducing user-visible delays on dual-stack hosts.  This
 definition obsoletes the original description in [RFC6555].  Now that
 this approach has been deployed at scale and measured for several
 years, the algorithm specification can be refined to improve its
 reliability and general applicability.
 The Happy Eyeballs algorithm of racing connections to resolved
 addresses has several stages to avoid delays to the user whenever
 possible, while preferring the use of IPv6.  This document discusses
 how to handle DNS queries when starting a connection on a dual-stack
 client, how to create an ordered list of destination addresses to
 which to attempt connections, and how to race the connection
 attempts.

1.1. Requirements Language

 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
 [RFC2119] [RFC8174] when, and only when, they appear in all capitals,
 as shown here.

Schinazi & Pauly Standards Track [Page 3] RFC 8305 Happy Eyeballs v2 December 2017

2. Overview

 This document defines a method of connection establishment, named the
 "Happy Eyeballs Connection Setup".  This approach has several
 distinct phases:
 1.  Initiation of asynchronous DNS queries [Section 3]
 2.  Sorting of resolved destination addresses [Section 4]
 3.  Initiation of asynchronous connection attempts [Section 5]
 4.  Establishment of one connection, which cancels all other attempts
     [Section 5]
 Note that this document assumes that the preference policy for the
 host destination address favors IPv6 over IPv4.  IPv6 has many
 desirable properties designed to be improvements over IPv4 [RFC8200].
 If the host is configured to have a different preference, the
 recommendations in this document can be easily adapted.

3. Hostname Resolution Query Handling

 When a client has both IPv4 and IPv6 connectivity and is trying to
 establish a connection with a named host, it needs to send out both
 AAAA and A DNS queries.  Both queries SHOULD be made as soon after
 one another as possible, with the AAAA query made first and
 immediately followed by the A query.
 Implementations SHOULD NOT wait for both families of answers to
 return before attempting connection establishment.  If one query
 fails to return or takes significantly longer to return, waiting for
 the second address family can significantly delay the connection
 establishment of the first one.  Therefore, the client SHOULD treat
 DNS resolution as asynchronous.  Note that if the platform does not
 offer an asynchronous DNS API, this behavior can be simulated by
 making two separate synchronous queries on different threads, one per
 address family.
 The algorithm proceeds as follows: if a positive AAAA response (a
 response with at least one valid AAAA record) is received first, the
 first IPv6 connection attempt is immediately started.  If a positive
 A response is received first due to reordering, the client SHOULD
 wait a short time for the AAAA response to ensure that preference is
 given to IPv6 (it is common for the AAAA response to follow the A
 response by a few milliseconds).  This delay will be referred to as
 the "Resolution Delay".  The recommended value for the Resolution
 Delay is 50 milliseconds.  If a positive AAAA response is received

Schinazi & Pauly Standards Track [Page 4] RFC 8305 Happy Eyeballs v2 December 2017

 within the Resolution Delay period, the client immediately starts the
 IPv6 connection attempt.  If a negative AAAA response (no error, no
 data) is received within the Resolution Delay period or the AAAA
 response has not been received by the end of the Resolution Delay
 period, the client SHOULD proceed to sorting addresses (see
 Section 4) and staggered connection attempts (see Section 5) using
 any IPv4 addresses returned so far.  If the AAAA response arrives
 while these connection attempts are in progress but before any
 connection has been established, then the newly received IPv6
 addresses are incorporated into the list of available candidate
 addresses (see Section 6) and the process of connection attempts will
 continue with the IPv6 addresses added, until one connection is
 established.

3.1. Handling Multiple DNS Server Addresses

 If multiple DNS server addresses are configured for the current
 network, the client may have the option of sending its DNS queries
 over IPv4 or IPv6.  In keeping with the Happy Eyeballs approach,
 queries SHOULD be sent over IPv6 first (note that this is not
 referring to the sending of AAAA or A queries, but rather the address
 of the DNS server itself and IP version used to transport DNS
 messages).  If DNS queries sent to the IPv6 address do not receive
 responses, that address may be marked as penalized and queries can be
 sent to other DNS server addresses.
 As native IPv6 deployments become more prevalent and IPv4 addresses
 are exhausted, it is expected that IPv6 connectivity will have
 preferential treatment within networks.  If a DNS server is
 configured to be accessible over IPv6, IPv6 should be assumed to be
 the preferred address family.
 Client systems SHOULD NOT have an explicit limit to the number of DNS
 servers that can be configured, either manually or by the network.
 If such a limit is required by hardware limitations, the client
 SHOULD use at least one address from each address family from the
 available list.

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4. Sorting Addresses

 Before attempting to connect to any of the resolved destination
 addresses, the client should define the order in which to start the
 attempts.  Once the order has been defined, the client can use a
 simple algorithm for racing each option after a short delay (see
 Section 5).  It is important that the ordered list involve all
 addresses from both families that have been received by this point,
 as this allows the client to get the racing effect of Happy Eyeballs
 for the entire list, not just the first IPv4 and first IPv6
 addresses.
 First, the client MUST sort the addresses received up to this point
 using Destination Address Selection ([RFC6724], Section 6).
 If the client is stateful and has a history of expected round-trip
 times (RTTs) for the routes to access each address, it SHOULD add a
 Destination Address Selection rule between rules 8 and 9 that prefers
 addresses with lower RTTs.  If the client keeps track of which
 addresses it used in the past, it SHOULD add another Destination
 Address Selection rule between the RTT rule and rule 9, which prefers
 used addresses over unused ones.  This helps servers that use the
 client's IP address during authentication, as is the case for TCP
 Fast Open [RFC7413] and some Hypertext Transport Protocol (HTTP)
 cookies.  This historical data MUST NOT be used across different
 network interfaces and SHOULD be flushed whenever a device changes
 the network to which it is attached.
 Next, the client SHOULD modify the ordered list to interleave address
 families.  Whichever address family is first in the list should be
 followed by an address of the other address family; that is, if the
 first address in the sorted list is IPv6, then the first IPv4 address
 should be moved up in the list to be second in the list.  An
 implementation MAY want to favor one address family more by allowing
 multiple addresses of that family to be attempted before trying the
 other family.  The number of contiguous addresses of the first
 address family will be referred to as the "First Address Family
 Count" and can be a configurable value.  This is performed to avoid
 waiting through a long list of addresses from a given address family
 if connectivity over that address family is impaired.
 Note that the address selection described in this section only
 applies to destination addresses; Source Address Selection
 ([RFC6724], Section 5) is performed once per destination address and
 is out of scope of this document.

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5. Connection Attempts

 Once the list of addresses received up to this point has been
 constructed, the client will attempt to make connections.  In order
 to avoid unreasonable network load, connection attempts SHOULD NOT be
 made simultaneously.  Instead, one connection attempt to a single
 address is started first, followed by the others in the list, one at
 a time.  Starting a new connection attempt does not affect previous
 attempts, as multiple connection attempts may occur in parallel.
 Once one of the connection attempts succeeds (generally when the TCP
 handshake completes), all other connections attempts that have not
 yet succeeded SHOULD be canceled.  Any address that was not yet
 attempted as a connection SHOULD be ignored.  At that time, the
 asynchronous DNS query MAY be canceled as new addresses will not be
 used for this connection.  However, the DNS client resolver SHOULD
 still process DNS replies from the network for a short period of time
 (recommended to be 1 second), as they will populate the DNS cache and
 can be used for subsequent connections.
 A simple implementation can have a fixed delay for how long to wait
 before starting the next connection attempt.  This delay is referred
 to as the "Connection Attempt Delay".  One recommended value for a
 default delay is 250 milliseconds.  A more nuanced implementation's
 delay should correspond to the time when the previous attempt is
 sending its second TCP SYN, based on the TCP's retransmission timer
 [RFC6298].  If the client has historical RTT data gathered from other
 connections to the same host or prefix, it can use this information
 to influence its delay.  Note that this algorithm should only try to
 approximate the time of the first SYN retransmission, and not any
 further retransmissions that may be influenced by exponential timer
 back off.
 The Connection Attempt Delay MUST have a lower bound, especially if
 it is computed using historical data.  More specifically, a
 subsequent connection MUST NOT be started within 10 milliseconds of
 the previous attempt.  The recommended minimum value is 100
 milliseconds, which is referred to as the "Minimum Connection Attempt
 Delay".  This minimum value is required to avoid congestion collapse
 in the presence of high packet-loss rates.  The Connection Attempt
 Delay SHOULD have an upper bound, referred to as the "Maximum
 Connection Attempt Delay".  The current recommended value is 2
 seconds.

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6. DNS Answer Changes during Happy Eyeballs Connection Setup

 If, during the course of connection establishment, the DNS answers
 change by either adding resolved addresses (for example due to DNS
 push notifications [DNS-PUSH]) or removing previously resolved
 addresses (for example, due to expiry of the TTL on that DNS record),
 the client should react based on its current progress.
 If an address is removed from the list that already had a connection
 attempt started, the connection attempt SHOULD NOT be canceled, but
 rather be allowed to continue.  If the removed address had not yet
 had a connection attempt started, it SHOULD be removed from the list
 of addresses to try.
 If an address is added to the list, it should be sorted into the list
 of addresses not yet attempted according to the rules above (see
 Section 4).

7. Supporting IPv6-Only Networks with NAT64 and DNS64

 While many IPv6 transition protocols have been standardized and
 deployed, most are transparent to client devices.  The combined use
 of NAT64 [RFC6146] and DNS64 [RFC6147] is a popular solution that is
 being deployed and requires changes in client devices.  One possible
 way to handle these networks is for the client device networking
 stack to implement 464XLAT [RFC6877]. 464XLAT has the advantage of
 not requiring changes to user space software; however, it requires
 per-packet translation if the application is using IPv4 literals and
 does not encourage client application software to support native
 IPv6.  On platforms that do not support 464XLAT, the Happy Eyeballs
 engine SHOULD follow the recommendations in this section to properly
 support IPv6-only networks with NAT64 and DNS64.
 The features described in this section SHOULD only be enabled when
 the host detects one of these networks.  A simple heuristic to
 achieve that is to check if the network offers routable IPv6
 addressing, does not offer routable IPv4 addressing, and offers a DNS
 resolver address.

7.1. IPv4 Address Literals

 If client applications or users wish to connect to IPv4 address
 literals, the Happy Eyeballs engine will need to perform NAT64
 address synthesis for them.  The solution is similar to "Bump-in-the-
 Host" [RFC6535] but is implemented inside the Happy Eyeballs library.

Schinazi & Pauly Standards Track [Page 8] RFC 8305 Happy Eyeballs v2 December 2017

 When an IPv4 address is passed into the library instead of a
 hostname, the device queries the network for the NAT64 prefix using
 "Discovery of the IPv6 Prefix Used for IPv6 Address Synthesis"
 [RFC7050] and then synthesizes an appropriate IPv6 address (or
 several) using the encoding described in "IPv6 Addressing of IPv4/
 IPv6 Translators" [RFC6052].  The synthesized addresses are then
 inserted into the list of addresses as if they were results from DNS
 queries; connection attempts follow the algorithm described above
 (see Section 5).

7.2. Hostnames with Broken AAAA Records

 At the time of writing, there exist a small but non-negligible number
 of hostnames that resolve to valid A records and broken AAAA records,
 which we define as AAAA records that contain seemingly valid IPv6
 addresses but those addresses never reply when contacted on the usual
 ports.  These can be, for example, caused by:
 o  Mistyping of the IPv6 address in the DNS zone configuration
 o  Routing black holes
 o  Service outages
 While an algorithm complying with the other sections of this document
 would correctly handle such hostnames on a dual-stack network, they
 will not necessarily function correctly on IPv6-only networks with
 NAT64 and DNS64.  Since DNS64 recursive resolvers rely on the
 authoritative name servers sending negative ("no error no answer")
 responses for AAAA records in order to synthesize, they will not
 synthesize records for these particular hostnames and will instead
 pass through the broken AAAA record.
 In order to support these scenarios, the client device needs to query
 the DNS for the A record and then perform local synthesis.  Since
 these types of hostnames are rare and, in order to minimize load on
 DNS servers, this A query should only be performed when the client
 has given up on the AAAA records it initially received.  This can be
 achieved by using a longer timeout, referred to as the "Last Resort
 Local Synthesis Delay"; the delay is recommended to be 2 seconds.
 The timer is started when the last connection attempt is fired.  If
 no connection attempt has succeeded when this timer fires, the device
 queries the DNS for the IPv4 address and, on reception of a valid A
 record, treats it as if it were provided by the application (see
 Section 7.1).

Schinazi & Pauly Standards Track [Page 9] RFC 8305 Happy Eyeballs v2 December 2017

7.3. Virtual Private Networks

 Some Virtual Private Networks (VPNs) may be configured to handle DNS
 queries from the device.  The configuration could encompass all
 queries or a subset such as "*.internal.example.com".  These VPNs can
 also be configured to only route part of the IPv4 address space, such
 as 192.0.2.0/24.  However, if an internal hostname resolves to an
 external IPv4 address, these can cause issues if the underlying
 network is IPv6-only.  As an example, let's assume that
 "www.internal.example.com" has exactly one A record, 198.51.100.42,
 and no AAAA records.  The client will send the DNS query to the
 company's recursive resolver and that resolver will reply with these
 records.  The device now only has an IPv4 address to connect to and
 no route to that address.  Since the company's resolver does not know
 the NAT64 prefix of the underlying network, it cannot synthesize the
 address.  Similarly, the underlying network's DNS64 recursive
 resolver does not know the company's internal addresses, so it cannot
 resolve the hostname.  Because of this, the client device needs to
 resolve the A record using the company's resolver and then locally
 synthesize an IPv6 address, as if the resolved IPv4 address were
 provided by the application (Section 7.1).

8. Summary of Configurable Values

 The values that may be configured as defaults on a client for use in
 Happy Eyeballs are as follows:
 o  Resolution Delay (Section 3): The time to wait for a AAAA response
    after receiving an A response.  Recommended to be 50 milliseconds.
 o  First Address Family Count (Section 4): The number of addresses
    belonging to the first address family (such as IPv6) that should
    be attempted before attempting another address family.
    Recommended to be 1; 2 may be used to more aggressively favor a
    particular address family.
 o  Connection Attempt Delay (Section 5): The time to wait between
    connection attempts in the absence of RTT data.  Recommended to be
    250 milliseconds.
 o  Minimum Connection Attempt Delay (Section 5): The minimum time to
    wait between connection attempts.  Recommended to be 100
    milliseconds.  MUST NOT be less than 10 milliseconds.
 o  Maximum Connection Attempt Delay (Section 5): The maximum time to
    wait between connection attempts.  Recommended to be 2 seconds.

Schinazi & Pauly Standards Track [Page 10] RFC 8305 Happy Eyeballs v2 December 2017

 o  Last Resort Local Synthesis Delay (Section 7.2): The time to wait
    after starting the last IPv6 attempt and before sending the A
    query.  Recommended to be 2 seconds.
 The delay values described in this section were determined
 empirically by measuring the timing of connections on a very wide set
 of production devices.  They were picked to reduce wait times noticed
 by users while minimizing load on the network.  As time passes, it is
 expected that the properties of networks will evolve.  For that
 reason, it is expected that these values will change over time.
 Implementors should feel welcome to use different values without
 changing this specification.  Since IPv6 issues are expected to be
 less common, the delays SHOULD be increased with time as client
 software is updated.

9. Limitations

 Happy Eyeballs will handle initial connection failures at the TCP/IP
 layer; however, other failures or performance issues may still affect
 the chosen connection.

9.1. Path Maximum Transmission Unit Discovery

 Since Happy Eyeballs is only active during the initial handshake and
 TCP does not pass the initial handshake, issues related to MTU can be
 masked and go unnoticed during Happy Eyeballs.  Solving this issue is
 out of scope of this document.  One solution is to use "Packetization
 Layer Path MTU Discovery" [RFC4821].

9.2. Application Layer

 If the DNS returns multiple addresses for different application
 servers, the application itself may not be operational and functional
 on all of them.  Common examples include Transport Layer Security
 (TLS) and HTTP.

9.3. Hiding Operational Issues

 It has been observed in practice that Happy Eyeballs can hide issues
 in networks.  For example, if a misconfiguration causes IPv6 to
 consistently fail on a given network while IPv4 is still functional,
 Happy Eyeballs may impair the operator's ability to notice the issue.
 It is recommended that network operators deploy external means of
 monitoring to ensure functionality of all address families.

Schinazi & Pauly Standards Track [Page 11] RFC 8305 Happy Eyeballs v2 December 2017

10. Security Considerations

 Note that applications should not rely upon a stable hostname-to-
 address mapping to ensure any security properties, since DNS results
 may change between queries.  Happy Eyeballs may make it more likely
 that subsequent connections to a single hostname use different IP
 addresses.

11. IANA Considerations

 This document does not require any IANA actions.

12. References

12.1. 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>.
 [RFC4821]  Mathis, M. and J. Heffner, "Packetization Layer Path MTU
            Discovery", RFC 4821, DOI 10.17487/RFC4821, March 2007,
            <https://www.rfc-editor.org/info/rfc4821>.
 [RFC6052]  Bao, C., Huitema, C., Bagnulo, M., Boucadair, M., and X.
            Li, "IPv6 Addressing of IPv4/IPv6 Translators", RFC 6052,
            DOI 10.17487/RFC6052, October 2010,
            <https://www.rfc-editor.org/info/rfc6052>.
 [RFC6146]  Bagnulo, M., Matthews, P., and I. van Beijnum, "Stateful
            NAT64: Network Address and Protocol Translation from IPv6
            Clients to IPv4 Servers", RFC 6146, DOI 10.17487/RFC6146,
            April 2011, <https://www.rfc-editor.org/info/rfc6146>.
 [RFC6147]  Bagnulo, M., Sullivan, A., Matthews, P., and I. van
            Beijnum, "DNS64: DNS Extensions for Network Address
            Translation from IPv6 Clients to IPv4 Servers", RFC 6147,
            DOI 10.17487/RFC6147, April 2011,
            <https://www.rfc-editor.org/info/rfc6147>.
 [RFC6298]  Paxson, V., Allman, M., Chu, J., and M. Sargent,
            "Computing TCP's Retransmission Timer", RFC 6298,
            DOI 10.17487/RFC6298, June 2011,
            <https://www.rfc-editor.org/info/rfc6298>.

Schinazi & Pauly Standards Track [Page 12] RFC 8305 Happy Eyeballs v2 December 2017

 [RFC6535]  Huang, B., Deng, H., and T. Savolainen, "Dual-Stack Hosts
            Using "Bump-in-the-Host" (BIH)", RFC 6535,
            DOI 10.17487/RFC6535, February 2012,
            <https://www.rfc-editor.org/info/rfc6535>.
 [RFC6555]  Wing, D. and A. Yourtchenko, "Happy Eyeballs: Success with
            Dual-Stack Hosts", RFC 6555, DOI 10.17487/RFC6555, April
            2012, <https://www.rfc-editor.org/info/rfc6555>.
 [RFC6724]  Thaler, D., Ed., Draves, R., Matsumoto, A., and T. Chown,
            "Default Address Selection for Internet Protocol Version 6
            (IPv6)", RFC 6724, DOI 10.17487/RFC6724, September 2012,
            <https://www.rfc-editor.org/info/rfc6724>.
 [RFC7050]  Savolainen, T., Korhonen, J., and D. Wing, "Discovery of
            the IPv6 Prefix Used for IPv6 Address Synthesis",
            RFC 7050, DOI 10.17487/RFC7050, November 2013,
            <https://www.rfc-editor.org/info/rfc7050>.
 [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>.

12.2. Informative References

 [DNS-PUSH] Pusateri, T. and S. Cheshire, "DNS Push Notifications",
            Work in Progress, draft-ietf-dnssd-push-13, October 2017.
 [RFC6877]  Mawatari, M., Kawashima, M., and C. Byrne, "464XLAT:
            Combination of Stateful and Stateless Translation",
            RFC 6877, DOI 10.17487/RFC6877, April 2013,
            <https://www.rfc-editor.org/info/rfc6877>.
 [RFC7413]  Cheng, Y., Chu, J., Radhakrishnan, S., and A. Jain, "TCP
            Fast Open", RFC 7413, DOI 10.17487/RFC7413, December 2014,
            <https://www.rfc-editor.org/info/rfc7413>.
 [RFC8200]  Deering, S. and R. Hinden, "Internet Protocol, Version 6
            (IPv6) Specification", STD 86, RFC 8200,
            DOI 10.17487/RFC8200, July 2017,
            <https://www.rfc-editor.org/info/rfc8200>.

Schinazi & Pauly Standards Track [Page 13] RFC 8305 Happy Eyeballs v2 December 2017

Appendix A. Differences from RFC 6555

 "Happy Eyeballs: Success with Dual-Stack Hosts" [RFC6555] mostly
 concentrates on how to stagger connections to a hostname that has a
 AAAA and an A record.  This document additionally discusses:
 o  how to perform DNS queries to obtain these addresses
 o  how to handle multiple addresses from each address family
 o  how to handle DNS updates while connections are being raced
 o  how to leverage historical information
 o  how to support IPv6-only networks with NAT64 and DNS64
 Note that a simple implementation of the algorithm described in this
 document is still compliant with the previous specification
 [RFC6555].  Implementations should take the new considerations into
 account when applicable to optimize their behavior.

Schinazi & Pauly Standards Track [Page 14] RFC 8305 Happy Eyeballs v2 December 2017

Acknowledgments

 The authors thank Dan Wing, Andrew Yourtchenko, and everyone else who
 worked on the original Happy Eyeballs design [RFC6555], Josh
 Graessley, Stuart Cheshire, and the rest of team at Apple that helped
 implement and instrument this algorithm, and Jason Fesler and Paul
 Saab who helped measure and refine this algorithm.  The authors would
 also like to thank Fred Baker, Nick Chettle, Lorenzo Colitti, Igor
 Gashinsky, Geoff Huston, Jen Linkova, Paul Hoffman, Philip Homburg,
 Warren Kumari, Erik Nygren, Jordi Palet Martinez, Rui Paulo, Stephen
 Strowes, Jinmei Tatuya, Dave Thaler, Joe Touch, and James Woodyatt
 for their input and contributions.

Authors' Addresses

 David Schinazi
 Apple Inc.
 1 Infinite Loop
 Cupertino, California  95014
 United States of America
 Email: dschinazi@apple.com
 Tommy Pauly
 Apple Inc.
 1 Infinite Loop
 Cupertino, California  95014
 United States of America
 Email: tpauly@apple.com

Schinazi & Pauly Standards Track [Page 15]

/data/webs/external/dokuwiki/data/pages/rfc/rfc8305.txt · Last modified: 2017/12/21 17:53 by 127.0.0.1

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