draft-ietf-v6ops-happy-eyeballs-00.txt   draft-ietf-v6ops-happy-eyeballs-01.txt 
v6ops D. Wing v6ops D. Wing
Internet-Draft A. Yourtchenko Internet-Draft A. Yourtchenko
Intended status: Standards Track Cisco Intended status: Standards Track Cisco
Expires: September 4, 2011 March 3, 2011 Expires: September 15, 2011 March 14, 2011
Happy Eyeballs: Trending Towards Success with Dual-Stack Hosts Happy Eyeballs: Trending Towards Success with Dual-Stack Hosts
draft-ietf-v6ops-happy-eyeballs-00 draft-ietf-v6ops-happy-eyeballs-01
Abstract Abstract
This document describes how a dual-stack client can determine the This document describes how a dual-stack client can determine the
functioning path to a dual-stack server. This provides a seamless functioning path to a dual-stack server. This provides a seamless
user experience during initial deployment of dual-stack networks and user experience during initial deployment of dual-stack networks and
during outages of IPv4 or outages of IPv6. during outages of IPv4 or outages of IPv6.
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
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/. Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
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 September 4, 2011. This Internet-Draft will expire on September 15, 2011.
Copyright Notice Copyright Notice
Copyright (c) 2011 IETF Trust and the persons identified as the Copyright (c) 2011 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of (http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents publication of this document. Please review these documents
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Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Notational Conventions . . . . . . . . . . . . . . . . . . . . 4 2. Notational Conventions . . . . . . . . . . . . . . . . . . . . 4
3. Problem Statement . . . . . . . . . . . . . . . . . . . . . . 4 3. Problem Statement . . . . . . . . . . . . . . . . . . . . . . 4
3.1. URIs and hostnames . . . . . . . . . . . . . . . . . . . . 4 3.1. URIs and hostnames . . . . . . . . . . . . . . . . . . . . 4
3.2. IPv6 connectivity . . . . . . . . . . . . . . . . . . . . 4 3.2. IPv6 connectivity . . . . . . . . . . . . . . . . . . . . 4
4. Client Recommendations . . . . . . . . . . . . . . . . . . . . 5 4. Client Recommendations . . . . . . . . . . . . . . . . . . . . 5
4.1. Dualstack behavior . . . . . . . . . . . . . . . . . . . . 5 4.1. Dualstack behavior . . . . . . . . . . . . . . . . . . . . 5
4.2. Implementation details . . . . . . . . . . . . . . . . . . 6 4.2. Implementation details . . . . . . . . . . . . . . . . . . 6
4.3. Additional Considerations . . . . . . . . . . . . . . . . 8 4.2.1. Applications that use address records . . . . . . . . 6
4.3.1. Additional Network and Host Traffic . . . . . . . . . 8 4.2.2. Applications that use the SRV records . . . . . . . . 8
4.3.2. Abandon Non-Winning Connections . . . . . . . . . . . 9 5. Additional Considerations . . . . . . . . . . . . . . . . . . 9
4.3.3. Flush or Expire Cache . . . . . . . . . . . . . . . . 9 5.1. Additional Network and Host Traffic . . . . . . . . . . . 9
4.3.4. Determining Address Type . . . . . . . . . . . . . . . 9 5.2. Abandon Non-Winning Connections . . . . . . . . . . . . . 10
4.3.5. Debugging and Troubleshooting . . . . . . . . . . . . 9 5.3. Flush or Expire Cache . . . . . . . . . . . . . . . . . . 10
4.3.6. DNS Behavior . . . . . . . . . . . . . . . . . . . . . 10 5.4. Determining Address Type . . . . . . . . . . . . . . . . . 10
4.3.7. Middlebox Issues . . . . . . . . . . . . . . . . . . . 10 5.5. Debugging and Troubleshooting . . . . . . . . . . . . . . 10
4.3.8. Multiple Interfaces . . . . . . . . . . . . . . . . . 11 5.6. DNS Behavior . . . . . . . . . . . . . . . . . . . . . . . 11
4.4. Content Provider Recommendations . . . . . . . . . . . . . 11 5.7. Middlebox Issues . . . . . . . . . . . . . . . . . . . . . 11
4.5. Security Considerations . . . . . . . . . . . . . . . . . 11 5.8. Multiple Interfaces . . . . . . . . . . . . . . . . . . . 12
4.6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . 11 6. Content Provider Recommendations . . . . . . . . . . . . . . . 12
4.7. IANA Considerations . . . . . . . . . . . . . . . . . . . 12 7. Security Considerations . . . . . . . . . . . . . . . . . . . 12
5. References . . . . . . . . . . . . . . . . . . . . . . . . . . 12 8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 12
5.1. Normative References . . . . . . . . . . . . . . . . . . . 12 9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 13
5.2. Informational References . . . . . . . . . . . . . . . . . 12 10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 13 10.1. Normative References . . . . . . . . . . . . . . . . . . . 13
10.2. Informational References . . . . . . . . . . . . . . . . . 13
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 14
1. Introduction 1. Introduction
In order to use HTTP successfully over IPv6, it is necessary that the In order to use HTTP successfully over IPv6, it is necessary that the
user enjoys nearly identical performance as compared to IPv4. A user enjoys nearly identical performance as compared to IPv4. A
combination of today's applications, IPv6 tunneling and IPv6 service combination of today's applications, IPv6 tunneling and IPv6 service
providers, and some of today's content providers all cause the user providers, and some of today's content providers all cause the user
experience to suffer (Section 3). For IPv6, a content provider may experience to suffer (Section 3). For IPv6, a content provider may
ensure a positive user experience by using a DNS white list of IPv6 ensure a positive user experience by using a DNS white list of IPv6
service providers who peer directly with them, e.g. [whitelist]. service providers who peer directly with them, e.g. [whitelist].
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systems to improve the user experience. systems to improve the user experience.
Reasons for such failure include no connection to the IPv6 Internet, Reasons for such failure include no connection to the IPv6 Internet,
broken 6to4 or Teredo tunnels, and broken IPv6 peering. broken 6to4 or Teredo tunnels, and broken IPv6 peering.
DNS Server Client Server DNS Server Client Server
| | | | | |
1. |<--www.example.com A?-----| | 1. |<--www.example.com A?-----| |
2. |<--www.example.com AAAA?--| | 2. |<--www.example.com AAAA?--| |
3. |---192.0.2.1------------->| | 3. |---192.0.2.1------------->| |
4. |---2001:dba::1----------->| | 4. |---2001:db8::1----------->| |
5. | | | 5. | | |
6. | |--TCP SYN, IPv6--->X | 6. | |--TCP SYN, IPv6--->X |
7. | |--TCP SYN, IPv6--->X | 7. | |--TCP SYN, IPv6--->X |
8. | |--TCP SYN, IPv6--->X | 8. | |--TCP SYN, IPv6--->X |
9. | | | 9. | | |
10. | |--TCP SYN, IPv4------->| 10. | |--TCP SYN, IPv4------->|
11. | |<-TCP SYN+ACK, IPv4----| 11. | |<-TCP SYN+ACK, IPv4----|
12. | |--TCP ACK, IPv4------->| 12. | |--TCP ACK, IPv4------->|
Figure 1: Existing behavior message flow Figure 1: Existing behavior message flow
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If a TCP client supports IPv6 and IPv4 and is connected to IPv4 and If a TCP client supports IPv6 and IPv4 and is connected to IPv4 and
IPv6 networks, it can perform the procedures described in this IPv6 networks, it can perform the procedures described in this
section. section.
DNS Server Client Server DNS Server Client Server
| | | | | |
1. |<--www.example.com A?-----| | 1. |<--www.example.com A?-----| |
2. |<--www.example.com AAAA?--| | 2. |<--www.example.com AAAA?--| |
3. |---192.0.2.1------------->| | 3. |---192.0.2.1------------->| |
4. |---2001:dba::1----------->| | 4. |---2001:db8::1----------->| |
5. | | | 5. | | |
6. | |==TCP SYN, IPv6===>X | 6. | |==TCP SYN, IPv6===>X |
7. | |--TCP SYN, IPv4------->| 7. | |--TCP SYN, IPv4------->|
8. | |<-TCP SYN+ACK, IPv4----| 8. | |<-TCP SYN+ACK, IPv4----|
9. | |--TCP ACK, IPv4------->| 9. | |--TCP ACK, IPv4------->|
10. | |==TCP SYN, IPv6===>X | 10. | |==TCP SYN, IPv6===>X |
Figure 2: Happy Eyeballs flow 1, IPv6 broken Figure 2: Happy Eyeballs flow 1, IPv6 broken
In the diagram above, the client sends two TCP SYNs at the same time In the diagram above, the client sends two TCP SYNs at the same time
over IPv6 (6) and IPv4 (7). In the diagram, the IPv6 path is broken over IPv6 (6) and IPv4 (7). In the diagram, the IPv6 path is broken
but has little impact to the user because there is no long delay but has little impact to the user because there is no long delay
before using IPv4. The IPv6 path is retried until the application before using IPv4. The IPv6 path is retried until the application
gives up (10). gives up (10).
DNS Server Client Server DNS Server Client Server
| | | | | |
1. |<--www.example.com A?-----| | 1. |<--www.example.com A?-----| |
2. |<--www.example.com AAAA?--| | 2. |<--www.example.com AAAA?--| |
3. |---192.0.2.1------------->| | 3. |---192.0.2.1------------->| |
4. |---2001:dba::1----------->| | 4. |---2001:db8::1----------->| |
5. | | | 5. | | |
6. | |==TCP SYN, IPv6=======>| 6. | |==TCP SYN, IPv6=======>|
7. | |--TCP SYN, IPv4------->| 7. | |--TCP SYN, IPv4------->|
8. | |<=TCP SYN+ACK, IPv6====| 8. | |<=TCP SYN+ACK, IPv6====|
9. | |<-TCP SYN+ACK, IPv4----| 9. | |<-TCP SYN+ACK, IPv4----|
10. | |==TCP ACK, IPv6=======>| 10. | |==TCP ACK, IPv6=======>|
11. | |--TCP ACK, IPv4------->| 11. | |--TCP ACK, IPv4------->|
12. | |--TCP RST, IPv4------->| 12. | |--TCP RST, IPv4------->|
Figure 3: Happy Eyeballs flow 2, IPv6 working Figure 3: Happy Eyeballs flow 2, IPv6 working
The diagram above shows a case where both IPv6 and IPv4 are working, The diagram above shows a case where both IPv6 and IPv4 are working,
and IPv4 is abandoned (12). and IPv4 is abandoned (12).
4.2. Implementation details 4.2. Implementation details
4.2.1. Applications that use address records
This section details how to provide robust dual stack service for This section details how to provide robust dual stack service for
both IPv6 and IPv4, so that the user perceives very fast application both IPv6 and IPv4, so that the user perceives very fast application
response. response.
The TCP client application is configured with one application-wide The TCP client application is configured with one application-wide
value of P. A positive value indicates a preference for IPv6 and a value of P. A positive value indicates a preference for IPv6 and a
negative value indicates a preference for IPv4. A value of 0 negative value indicates a preference for IPv4. A value of 0
indicates equal weight, which means the A and AAAA queries and indicates equal weight, which means the A and AAAA queries and
associated connection attempts will be sent as quickly as possible. associated connection attempts will be sent as quickly as possible.
The absolute value of P is the measure of a delay before initiating a The absolute value of P is the measure of a delay before initiating a
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* if P>0, wait for p*10 milliseconds * if P>0, wait for p*10 milliseconds
* send DNS query for A * send DNS query for A
* wait until DNS response is received * wait until DNS response is received
* Attempt to connect over IPv4 using TCP * Attempt to connect over IPv4 using TCP
The first thread that succeeds returns the completed connection to The first thread that succeeds returns the completed connection to
the parent code and aborts the other thread (Section 4.3.2). the parent code and aborts the other thread (Section 5.2).
After a connection is successful, we want to adjust the application- After a connection is successful, we want to adjust the application-
wide preference and the per-destination preference. The value of P wide preference and the per-destination preference. The value of P
is incremented (decremented) each time an IPv6 (IPv4) connection wins is incremented (decremented) each time an IPv6 (IPv4) connection wins
the race.. When a connection using the less-preferred address family the race.. When a connection using the less-preferred address family
is successful, it indicates the wrong address family was used and the is successful, it indicates the wrong address family was used and the
value of P is halved: value of P is halved:
o If P>0 (indicating IPv6 is preferred over IPv4) and the first o If P>0 (indicating IPv6 is preferred over IPv4) and the first
thread to finish was the IPv6 thread it indicates the IPv6 thread to finish was the IPv6 thread it indicates the IPv6
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that even smaller value (around 0.5 seconds) may be practical. that even smaller value (around 0.5 seconds) may be practical.
More extensive testing would be useful to find the best upper More extensive testing would be useful to find the best upper
boundary that still ensures a good user experience. boundary that still ensures a good user experience.
Editor's Note 02: A strict implementation of the above steps Editor's Note 02: A strict implementation of the above steps
results in "P" being adjusted if there are no AAAA records or are results in "P" being adjusted if there are no AAAA records or are
no A records. This is undesirable. Thus, a future version of no A records. This is undesirable. Thus, a future version of
this specification is expected to recommend that "P" only be this specification is expected to recommend that "P" only be
adjusted if there was both an A and AAAA record. adjusted if there was both an A and AAAA record.
4.3. Additional Considerations 4.2.2. Applications that use the SRV records
For the purposes of this section, "client" is defined as the entity
initiating the connection.
For protocols which support DNS SRV [RFC2782], the client performs
the IN SRV query (e.g. IN SRV _xmpp-client._tcp.example.com) as
normal. The client MUST perform the following steps:
1. Sort all SRV records according to priority (lowest priority
first)
2. Process all of the SRV targets of the same priority with a weight
greater than 0:
A. Perform A/AAAA queries for each SRV target in parallel, as
described in Section 4.2.1
B. Connect to the IPv4/IPv6 addresses
C. If at least one connection succeeds, stop processing SRV
records
3. If there is no connection, process all of the SRV targets of the
same priority with a weight of 0, as per steps 2.1 through 2.3
above
4. Repeat steps 2.1 through 2.3 for the next priority, until a
connection is established or all SRV records have been exhausted
5. If there is still no connection, fallback to using the domain
(e.g. example.com), following steps 2.1 through 2.3 above
It is RECOMMENDED, but not required, for the client to cache the
winning connection's address information and reuse it on subsequent
connections. If a significant network event occurs (e.g. network
interface is activated/deactivated, IP address changes), the client
MUST forget the cached address information and perform all of the
steps from above. The definition of "significant network event" is
intentionally vague.
5. Additional Considerations
This section discusses considerations and requirements that are This section discusses considerations and requirements that are
common to new technology deployment. common to new technology deployment.
4.3.1. Additional Network and Host Traffic 5.1. Additional Network and Host Traffic
Additional network traffic and additional server load is created due Additional network traffic and additional server load is created due
to these recommendations and mitigated by application-wide and per- to these recommendations and mitigated by application-wide and per-
destination timer adjustments. The procedures described in this destination timer adjustments. The procedures described in this
document retain a quality user experience while transitioning from document retain a quality user experience while transitioning from
IPv4-only to dual stack. The quality user experience benefits the IPv4-only to dual stack. The quality user experience benefits the
user but to the detriment of the network and server that are serving user but to the detriment of the network and server that are serving
the user. the user.
4.3.2. Abandon Non-Winning Connections 5.2. Abandon Non-Winning Connections
It is RECOMMENDED that the non-winning connections be abandoned, even It is RECOMMENDED that the non-winning connections be abandoned, even
though they could be used to download content. This is because some though they could be used to download content. This is because some
web sites provide HTTP clients with cookies (after logging in) that web sites provide HTTP clients with cookies (after logging in) that
incorporate the client's IP address, or use IP addresses to identify incorporate the client's IP address, or use IP addresses to identify
users. If some connections from the same HTTP client are arriving users. If some connections from the same HTTP client are arriving
from different IP addresses, such HTTP applications will break. It's from different IP addresses, such HTTP applications will break. It's
also important to abandon connections to avoid consuming server or also important to abandon connections to avoid consuming server or
middlebox (e.g., NAT) resources (file descriptors, memory, TCP middlebox (e.g., NAT) resources (file descriptors, memory, TCP
control blocks) and avoid sending TCP or application-level keepalives control blocks) and avoid sending TCP or application-level keepalives
on otherwise unused connections. on otherwise unused connections.
4.3.3. Flush or Expire Cache 5.3. Flush or Expire Cache
Because every network has different characteristics (e.g., working or Because every network has different characteristics (e.g., working or
broken IPv6 connectivity) the IPv6/IPv4 preference value (P) SHOULD broken IPv6 connectivity) the IPv6/IPv4 preference value (P) SHOULD
be reset to its default whenever the host is connected to a new be reset to its default whenever the host is connected to a new
network ([cx-osx], [cx-win]). However, in some instances the network ([cx-osx], [cx-win]). However, in some instances the
application and the host are unaware the network connectivity has application and the host are unaware the network connectivity has
changed so it is RECOMMENDED that per-destination values expire after changed so it is RECOMMENDED that per-destination values expire after
10 minutes of inactivity. 10 minutes of inactivity.
4.3.4. Determining Address Type 5.4. Determining Address Type
For some transitional technologies such as a dual-stack host, it is For some transitional technologies such as a dual-stack host, it is
easy for the application to recognize the native IPv6 address easy for the application to recognize the native IPv6 address
(learned via a AAAA query) and the native IPv4 address (learned via (learned via a AAAA query) and the native IPv4 address (learned via
an A query). For other transitional technologies [RFC2766] it is an A query). For other transitional technologies [RFC2766] it is
impossible for the host to differentiate a transitional technology impossible for the host to differentiate a transitional technology
IPv6 address from a native IPv6 address (see Section 4.1 of IPv6 address from a native IPv6 address (see Section 4.1 of
[RFC4966]). Replacement transitional technologies are attempting to [RFC4966]). Replacement transitional technologies are attempting to
bridge this gap. It is necessary for applications to distinguish bridge this gap. It is necessary for applications to distinguish
between native and transitional addresses in order to provide the between native and transitional addresses in order to provide the
most seamless user experience. most seamless user experience.
Application awareness of transitional technologies, if implemented, Application awareness of transitional technologies, if implemented,
SHOULD provide a facility to give the preference only to native IPv6 SHOULD provide a facility to give the preference only to native IPv6
addresses. addresses.
4.3.5. Debugging and Troubleshooting 5.5. Debugging and Troubleshooting
This mechanism is aimed at ensuring a reliable user experience This mechanism is aimed at ensuring a reliable user experience
regardless of connectivity problems affecting any single transport. regardless of connectivity problems affecting any single transport.
However, this naturally means that applications employing these However, this naturally means that applications employing these
techniques are by default less useful for diagnosing issues with any techniques are by default less useful for diagnosing issues with any
particular transport. To assist in that regard, the applications particular transport. To assist in that regard, the applications
implementing the proposal in this document SHOULD also provide a implementing the proposal in this document SHOULD also provide a
mechanism to revert the behavior to that of a default provided by the mechanism to revert the behavior to that of a default provided by the
operating system - the [RFC3484]. operating system - the [RFC3484].
[[[ To be discussed. [[[ To be discussed.
Some sites may wish to be informed when the the hosts adjust their Some sites may wish to be informed when the the hosts adjust their
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these sites, a strawman proposal is to send a syslog message or these sites, a strawman proposal is to send a syslog message or
other notification to an address that may be configured by a site other notification to an address that may be configured by a site
administrator in a centralized fashion. (The exact method TBD - administrator in a centralized fashion. (The exact method TBD -
DHCP option, domain name, etc.) This syslog message should be DHCP option, domain name, etc.) This syslog message should be
sent only first N times that the host expects to prefer IPv6 but sent only first N times that the host expects to prefer IPv6 but
has to use IPv4. I.e. the first N times it decreases the value of has to use IPv4. I.e. the first N times it decreases the value of
P. N - TBD. P. N - TBD.
]]] ]]]
4.3.6. DNS Behavior 5.6. DNS Behavior
Unique to DNS AAAA queries are the problems described in [RFC4074] Unique to DNS AAAA queries are the problems described in [RFC4074]
which, if they still persist, require applications to perform an A which, if they still persist, require applications to perform an A
query before the AAAA query. query before the AAAA query.
[[Editor's Note 03: It is believed these defective DNS servers [[Editor's Note 03: It is believed these defective DNS servers
have long since been upgraded. If so, we can remove this have long since been upgraded. If so, we can remove this
section.]] section.]]
4.3.7. Middlebox Issues 5.7. Middlebox Issues
Some devices are known to exhibit what amounts to a bug, when the A Some devices are known to exhibit what amounts to a bug, when the A
and AAAA requests are sent back-to-back over the same 4-tuple, and and AAAA requests are sent back-to-back over the same 4-tuple, and
drop one of the requests or replies [DNS-middlebox]. However, in drop one of the requests or replies [DNS-middlebox]. However, in
some cases fixing this behaviour may not be possible either due to some cases fixing this behaviour may not be possible either due to
the architectural limitations or due to the administrative the architectural limitations or due to the administrative
constraints (location of the faulty device is unknown to the end constraints (location of the faulty device is unknown to the end
hosts or not controlled by the end hosts). The algorithm described hosts or not controlled by the end hosts). The algorithm described
in this draft, in the case of this erroneous behaviour will in this draft, in the case of this erroneous behaviour will
eventually pace the queries such that this issue is will be avoided. eventually pace the queries such that this issue is will be avoided.
The algorithm described in this draft also avoids calling the The algorithm described in this draft also avoids calling the
operating system's getaddrinfo() with "any", which should prevent the operating system's getaddrinfo() with "any", which should prevent the
operating system from sending the A and AAAA queries on the same operating system from sending the A and AAAA queries on the same
port. port.
For the large part, these issues are believed to be fixed, in which For the large part, these issues are believed to be fixed, in which
case the getaddrinfo() with AF_UNSPEC as the address family in its case the getaddrinfo() with AF_UNSPEC as the address family in its
hints. hints.
4.3.8. Multiple Interfaces 5.8. Multiple Interfaces
Interaction of the suggestions in this document with multiple Interaction of the suggestions in this document with multiple
interfaces, and interaction with the MIF working group, is for interfaces, and interaction with the MIF working group, is for
further study. further study ([I-D.chen-mif-happy-eyeballs-extension] is devoted to
this).
4.4. Content Provider Recommendations 6. Content Provider Recommendations
Content providers SHOULD provide both AAAA and A records for servers Content providers SHOULD provide both AAAA and A records for servers
using the same DNS name for both IPv4 and IPv6. using the same DNS name for both IPv4 and IPv6.
4.5. Security Considerations 7. Security Considerations
[[Placeholder.]] [[Placeholder.]]
See Section 4.3.2. See Section 5.2.
4.6. Acknowledgements 8. Acknowledgements
The mechanism described in this paper was inspired by Stuart The mechanism described in this paper was inspired by Stuart
Cheshire's discussion at the IAB Plenary at IETF72, the author's Cheshire's discussion at the IAB Plenary at IETF72, the author's
understanding of Safari's operation with SRV records, Interactive understanding of Safari's operation with SRV records, Interactive
Connectivity Establishment (ICE [RFC5245]), and the current IPv4/IPv6 Connectivity Establishment (ICE [RFC5245]), and the current IPv4/IPv6
behavior of SMTP mail transfer agents. behavior of SMTP mail transfer agents.
Thanks to Fred Baker, Jeff Kinzli, Christian Kuhtz, and Iljitsch van Thanks to Fred Baker, Jeff Kinzli, Christian Kuhtz, and Iljitsch van
Beijnum for fostering the creation of this document. Beijnum for fostering the creation of this document.
Thanks to Scott Brim, Rick Jones, Stig Venaas, Erik Kline, Bjoern Thanks to Scott Brim, Rick Jones, Stig Venaas, Erik Kline, Bjoern
Zeeb for providing feedback on the document. Zeeb, Matt Miller for providing feedback on the document.
Thanks to Javier Ubillos, Simon Perreault and Mark Andrews for the Thanks to Javier Ubillos, Simon Perreault and Mark Andrews for the
active feedback and the experimental work on the independent active feedback and the experimental work on the independent
practical implementations that they created. practical implementations that they created.
Also the authors would like to thank the following individuals who Also the authors would like to thank the following individuals who
participated in various email discussions on this topic: Mohacsi participated in various email discussions on this topic: Mohacsi
Janos, Pekka Savola, Ted Lemon, Carlos Martinez-Cagnazzo, Simon Janos, Pekka Savola, Ted Lemon, Carlos Martinez-Cagnazzo, Simon
Perreault, Jack Bates, Jeroen Massar, Fred Baker, Javier Ubillos, Perreault, Jack Bates, Jeroen Massar, Fred Baker, Javier Ubillos,
Teemu Savolainen, Scott Brim, Erik Kline, Cameron Byrne, Daniel Teemu Savolainen, Scott Brim, Erik Kline, Cameron Byrne, Daniel
Roesen, Guillaume Leclanche, Cameron Byrne, Mark Smith, Gert Doering, Roesen, Guillaume Leclanche, Cameron Byrne, Mark Smith, Gert Doering,
Martin Millnert, Tim Durack. Martin Millnert, Tim Durack, Matthew Palmer.
4.7. IANA Considerations 9. IANA Considerations
This document has no IANA actions. This document has no IANA actions.
5. References 10. References
5.1. Normative References 10.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997. Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC2782] Gulbrandsen, A., Vixie, P., and L. Esibov, "A DNS RR for
specifying the location of services (DNS SRV)", RFC 2782,
February 2000.
[RFC3484] Draves, R., "Default Address Selection for Internet [RFC3484] Draves, R., "Default Address Selection for Internet
Protocol version 6 (IPv6)", RFC 3484, February 2003. Protocol version 6 (IPv6)", RFC 3484, February 2003.
5.2. Informational References 10.2. Informational References
[Andrews] Andrews, M., "How to connect to a multi-homed server over [Andrews] Andrews, M., "How to connect to a multi-homed server over
TCP", January 2011, <http://www.isc.org/community/blog/ TCP", January 2011, <http://www.isc.org/community/blog/
201101/how-to-connect-to-a-multi-h omed-server-over-tcp>. 201101/how-to-connect-to-a-multi-h omed-server-over-tcp>.
[DNS-middlebox] [DNS-middlebox]
Various, "DNS middlebox behavior with multiple queries Various, "DNS middlebox behavior with multiple queries
over same source port", June 2009, over same source port", June 2009,
<https://bugzilla.redhat.com/show_bug.cgi?id=505105>. <https://bugzilla.redhat.com/show_bug.cgi?id=505105>.
[I-D.chen-mif-happy-eyeballs-extension]
Chen, G., "Happy Eyeballs Extension for Multiple
Interfaces", draft-chen-mif-happy-eyeballs-extension-00
(work in progress), March 2011.
[Perreault] [Perreault]
Perreault, S., "Happy Eyeballs in Erlang", February 2011, Perreault, S., "Happy Eyeballs in Erlang", February 2011,
<http://www.viagenie.ca/news/ <http://www.viagenie.ca/news/
index.html#happy_eyeballs_erlang>. index.html#happy_eyeballs_erlang>.
[RFC1671] Carpenter, B., "IPng White Paper on Transition and Other [RFC1671] Carpenter, B., "IPng White Paper on Transition and Other
Considerations", RFC 1671, August 1994. Considerations", RFC 1671, August 1994.
[RFC2766] Tsirtsis, G. and P. Srisuresh, "Network Address [RFC2766] Tsirtsis, G. and P. Srisuresh, "Network Address
Translation - Protocol Translation (NAT-PT)", RFC 2766, Translation - Protocol Translation (NAT-PT)", RFC 2766,
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