One document matched: draft-baker-bmwg-testing-eyeball-happiness-01.txt
Differences from draft-baker-bmwg-testing-eyeball-happiness-00.txt
IPv6 Operations F. Baker
Internet-Draft Cisco Systems
Intended status: Standards Track December 3, 2010
Expires: June 6, 2011
Testing Eyeball Happiness
draft-baker-bmwg-testing-eyeball-happiness-01
Abstract
The amount of time it takes to open a session using common transport
APIs in dual stack networks and networks with filtering such as
proposed in BCP 38 is a barrier to IPv6 deployment. This note
describes a test that can be used to determine whether an application
can reliably open sessions quickly in a complex environment such as
dual stack (IPv4+IPv6) deployment or IPv6 deployment with multiple
prefixes and upstream ingress filtering. This test is not a test of
a specific algorithm, but of the external behavior of the system as a
black box. Any algorithm that has the intended external behavior
will be accepted by it.
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
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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 June 6, 2011.
Copyright Notice
Copyright (c) 2010 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
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carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
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described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Measuring eyeball happiness . . . . . . . . . . . . . . . . . . 3
2.1. Happy Eyeballs test bed configuration . . . . . . . . . . . 4
2.2. Happy Eyeballs test procedure . . . . . . . . . . . . . . . 5
2.3. Happy Eyeballs metrics . . . . . . . . . . . . . . . . . . 6
2.3.1. Metric: Maximum Session Setup Interval . . . . . . . . 6
2.3.2. Metric: Minimum Session Setup Interval . . . . . . . . 7
2.3.3. Descriptive Metric: Attempt pattern . . . . . . . . . . 7
3. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 8
4. Security Considerations . . . . . . . . . . . . . . . . . . . . 8
5. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 8
6. Change Log . . . . . . . . . . . . . . . . . . . . . . . . . . 8
7. References . . . . . . . . . . . . . . . . . . . . . . . . . . 9
7.1. Normative References . . . . . . . . . . . . . . . . . . . 9
7.2. Informative References . . . . . . . . . . . . . . . . . . 9
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 9
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1. Introduction
The Happy Eyeballs [I-D.wing-v6ops-happy-eyeballs-ipv6] specification
observes on an issue in deployed multi-prefix IPv6-only and dual
stack networks, and proposes a correction. [RFC5461] similarly looks
at TCP's response to so-called "soft errors" (ICMP host and network
unreachable messages), pointing out an issue and a set of solutions.
In a network that contains both IPv4 [RFC0791] and IPv6 [RFC2460]
prefixes and routes or that uses multiple prefixes allocated by
upstream providers that implement BCP 38 Ingress Filtering [RFC2827],
the fact that two hosts that need to communicate have addresses using
the same architecture does not imply that the network has usable
routes connecting them, or that those addresses are useful to the
applications in question. In addition, the process of opening a
session using the Sockets API [RFC3493] is generally described in
terms of obtaining a list of possible addresses for a peer (which
will normally include both IPv4 and IPv6 addresses) using
getaddrinfo() and trying them in sequence until one succeeds or all
have failed. This naive algorithm, if implemented as described, has
the side-effect of making the worst case delay in opening a session
far longer than human patience normally allows.
This note describes a test that can be used to determine whether an
application can reliably open sessions quickly in a complex
environment such as dual stack (IPv4+IPv6) deployment or IPv6
deployment with multiple prefixes and upstream ingress filtering.
This is not a test of a specific algorithm, but a measurement of the
external behavior of the system as a black box. The question is how
long it takes an application, best case and worst case, to open a
session with a server or peer.
2. Measuring eyeball happiness
This measurement determines the amount of time it takes an
application to open a session with a peer in the presence of at least
one IPv4 and multiple IPv6 prefixes and a variety of network
behaviors. ISPs are reporting that a host (MacOSX, Windows, Linux,
FreeBSD, etc) that has more than one address (an IPv4 and an IPv6
address, two global IPv6 addresses, etc) may serially try addresses,
allowing each TCP setup to expire, taking several seconds for each
attempt. There have been reports of a session setup taking as long
as 40 seconds as a result. The amount of time necessary to establish
communication between two entities should be approximately the same
regardless of the type of address chosen or the viability of routing
in the specific network.
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2.1. Happy Eyeballs test bed configuration
The configuration of equipment and applications is as shown in
Figure 1.
+--------+ | |198.51.100.0/24
|Protocol| |192.0.2.0/24 |2001:DB8:0:2::/64
|Analyzer+-+2001:DB8:1:0::/64 |2001:DB8:1:4::/64
+--------+ |2001:DB8:0:1::/64 |2001:DB8:2:4::/64
| |
+-----+ | | +-----+
|Alice+-+ +-+ Bob |
+-----+ | +-------+ +-------+ | +-----+
+-+Router1| |Router2+-+
+-----+ | +-----+-+ +-+-----+ |
| DNS +-+ | | |
+-----+ | -+------+- |
| 203.0.113.0/24 |
| 2001:DB8:0:3::/64 |
Figure 1: Generic Test Environment
Alice is the unit being measured, the computer running the process
that will open a session with Bob for the application in question.
DNS is represented in the diagram as a separate system, as is the
protocol analyzer that will watch Alice's traffic. This is not
absolutely necessary; If one computer can run tcpdump and a DNS
server process - and for that matter subsume the routers - that is
acceptable. The units are separated in the test for purposes of
clarity.
On each test run, configuration is performed in Router 1 to permit
only one route to work. There are various ways this can be
accomplished, including but not limited to installing
o a filter that drops datagrams to Bob resulting in an ICMP
"administratively prohibited",
o a filter that drops datagrams to Bob silently,
o a null route or removing the route to one of Bob's prefixes,
resulting in an ICMP "destination unreachable", and
o a middleware program that responds with a TCP RST.
The tester should try different methods to determine whether
differences in this configuration make a difference in the test. For
example, one might find that the application under test responds
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differently to a TCP RST than to a silent packet loss.
2.2. Happy Eyeballs test procedure
Consider a network as described in Section 2.1. Alice and Bob each
have a set of one or more IPv4 and two or more IPv6 addresses in DNS,
and routers 1 and 2 are configured to route the relevant prefixes.
The measurement plays with an access list or null route in Router 1
that would prevent traffic Alice->Bob using each of Bob's addresses.
If Bob has a total of N addresses, we run the measurement at least N
times, permitting exactly one of the addresses to enjoy end to end
communication each time. If the DNS service randomizes the order of
the addresses, this may not result in a test requiring opening a
connection to all of the addresses; in this case, the test will have
to be run repeatedly until in at least one instance a TCP SYN or its
equivalent is seen for each relevant address. The tester should
either flush the resolver cache between iterations, to force repeated
DNS resolution, or should wait for at least the DNS RR TTL on each
resource record. In the latter case, the tester should also observe
DNS re-resolving; if not, the application is not correctly using DNS.
This specification assumes common LAN technology with no competing
traffic and nominal propagation delays, so that they are not a factor
in the measurement.
The objective is to measure the amount of time required to open a
session. This includes the time from Alice's initial DNS request
through one or more attempts to open a session to the session being
opened, as seen in the LAN trace. The simplest way to measure this
will be to put a traffic analyzer on Alice's point of attachment and
capture the messages exchanged by Alice.
DNS Server Alice Bob
| | |
1. |<--www.example.com A------| |
2. |<--www.example.com AAAA---| |
3. |---192.0.2.1------------->| |
4. |---2001:dba::1----------->| |
5. | | |
6. | |--TCP SYN, IPv6--->X |<***********
7. | |--TCP SYN, IPv6--->X | |
8. | |--TCP SYN, IPv6--->X | TCP 3wHS
9. | | | Time
10. | |--TCP SYN, IPv4------->|(any family)
11. | |<-TCP SYN+ACK, IPv4----| |
12. | |--TCP ACK, IPv4------->|<***********
Figure 2: Message flow using TCP
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In a TCP-based application (Figure 2), that would be from the DNS
request on line 1 through the first completion of a TCP three-way
handshake, the transmission on line 12.
DNS Server Alice Bob
| | |
1. |<--www.example.com A------| |
2. |<--www.example.com AAAA---| |
3. |---192.0.2.1------------->| |
4. |---2001:dba::1----------->| |
5. | | |
6. | |--UDP Request, IPv6-->X|
7. | |--UDP Request, IPv6-->X|
8. | |--UDP Request, IPv6-->X|
9. | | |
10. | |--UDP Request, IPv4--->|
11. | |<-UDP Response, IPv4---|
Figure 3: Message flow using UDP
In a UDP-based application (Figure 3), that would be from the DNS
request (line 1) through one or more UDP Requests (lines 6-10) until
a UDP Response is seen (line 11).
When using other transports, the methodology will have to be
specified in context; it should measure the same event.
2.3. Happy Eyeballs metrics
The measurements taken are the duration of the interval from the
initial DNS request until the session is seen to be open, as
described in Section 2.2. We are interested in the shortest and
longest durations (which will most likely be those that send one SYN
and succeed and those that send a SYN to each possible address before
succeeding in one of the attempts), and the pattern of attempts sent
to different addresses. The pattern may be to simply send an attempt
every <time interval>, or may be more complex; as a result, this is
in part descriptive.
2.3.1. Metric: Maximum Session Setup Interval
Name: Maximum Session Setup Interval
Description: The maximum session setup interval is the longest
period of time observed for the opening of a session.
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Methodology: In the LAN analyzer trace, note the times of the
initial DNS request and the confirmation that the session is open
as described in Section 2.2. Several instances of the test will
be run, in at least one of which an attempt is seen to each of
Bob's addresses. The setup interval is the difference between
those times, and the maximum setup interval is the largest of
those intervals.
Units: Session setup time is measured in milliseconds.
Measurement Point(s): The measurement point is at Alice's LAN
interface, observed using a program such as tcpdump running on
Alice or an external analyzer.
Timing: Continuous.
2.3.2. Metric: Minimum Session Setup Interval
Name: Minimum Session Setup Interval
Description: The minimum session setup interval is the shortest
period of time observed for the opening of a session.
Methodology: In the LAN analyzer trace, note the times of the
initial DNS request and the confirmation that the session is open
as described in Section 2.2. Several instances of the test will
be run, in at least one of which an attempt is seen to exactly one
of Bob's addresses. The setup interval is the difference between
those times, and the minimum setup interval is the smallest of
those intervals.
Units: Session setup time is measured in milliseconds.
Measurement Point(s): The measurement point is at Alice's LAN
interface, observed using a program such as tcpdump running on
Alice or an external analyzer.
Timing: Continuous.
2.3.3. Descriptive Metric: Attempt pattern
Name: Attempt pattern
Description: The Attempt Pattern is a description of the observed
pattern of attempts to open the session. In simple cases, it may
be something like "Initial TCP SYNs to a new address were observed
every <so many> milliseconds"; in more complex cases, it might be
something like "Initial TCP SYNs in IPv6 were observed every <so
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many> milliseconds, and other TCP SYNs using IPv4 were observed
every <so many> milliseconds, but the two sequences were
independent." It may also comment on retransmission patterns if
observed.
Methodology: The traffic trace is analyzed to determine the pattern
of initiation.
Units: milliseconds.
Measurement Point(s): The measurement point is at Alice's LAN
interface, observed using a program such as tcpdump running on
Alice or an external analyzer.
Timing: Continuous.
3. IANA Considerations
This memo asks the IANA for no new parameters.
Note to RFC Editor: This section will have served its purpose if it
correctly tells IANA that no new assignments or registries are
required, or if those assignments or registries are created during
the RFC publication process. From the author"s perspective, it may
therefore be removed upon publication as an RFC at the RFC Editor"s
discretion.
4. Security Considerations
This note doesn't address security-related issues.
5. Acknowledgements
This note was discussed with Dan Wing, Andrew Yourtchenko, and
Fernando Gont. In the Benchmark Methodology Working Group, Al
Morton, David Newman, and Sarah Banks made comments.
6. Change Log
-00 Version: Initial version - November, 2010
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-01 Version: Rewritten per suggestions by Al Morton and David
Newman.
7. References
7.1. Normative References
[I-D.wing-v6ops-happy-eyeballs-ipv6]
Wing, D. and A. Yourtchenko, "Happy Eyeballs: Trending
Towards Success with Dual-Stack Hosts",
draft-wing-v6ops-happy-eyeballs-ipv6-01 (work in
progress), October 2010.
7.2. Informative References
[RFC0791] Postel, J., "Internet Protocol", STD 5, RFC 791,
September 1981.
[RFC2460] Deering, S. and R. Hinden, "Internet Protocol, Version 6
(IPv6) Specification", RFC 2460, December 1998.
[RFC2827] Ferguson, P. and D. Senie, "Network Ingress Filtering:
Defeating Denial of Service Attacks which employ IP Source
Address Spoofing", BCP 38, RFC 2827, May 2000.
[RFC3493] Gilligan, R., Thomson, S., Bound, J., McCann, J., and W.
Stevens, "Basic Socket Interface Extensions for IPv6",
RFC 3493, February 2003.
[RFC5461] Gont, F., "TCP's Reaction to Soft Errors", RFC 5461,
February 2009.
Author's Address
Fred Baker
Cisco Systems
Santa Barbara, California 93117
USA
Email: fred@cisco.com
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