Internet DRAFT - draft-baker-bmwg-testing-eyeball-happiness
draft-baker-bmwg-testing-eyeball-happiness
Benchmarking Methodology F. Baker
Internet-Draft Cisco Systems
Intended status: Informational August 15, 2011
Expires: February 16, 2012
Testing Eyeball Happiness
draft-baker-bmwg-testing-eyeball-happiness-05
Abstract
The amount of time it takes to establish 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 establish 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.
Requirements
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119].
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 February 16, 2012.
Copyright Notice
Copyright (c) 2011 IETF Trust and the persons identified as the
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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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the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Measuring Eyeball Happiness . . . . . . . . . . . . . . . . . 4
2.1. Happy Eyeballs test bed configuration . . . . . . . . . . 4
2.2. Happy Eyeballs test procedure . . . . . . . . . . . . . . 6
2.3. Happy Eyeballs metrics . . . . . . . . . . . . . . . . . . 7
2.3.1. Metric: Session Setup Interval . . . . . . . . . . . . 7
2.3.2. Metric: Maximum Session Setup Interval . . . . . . . . 8
2.3.3. Metric: Minimum Session Setup Interval . . . . . . . . 9
2.3.4. Descriptive Metric: Attempt pattern . . . . . . . . . 9
3. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10
4. Security Considerations . . . . . . . . . . . . . . . . . . . 10
5. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 10
6. Change Log . . . . . . . . . . . . . . . . . . . . . . . . . . 10
7. References . . . . . . . . . . . . . . . . . . . . . . . . . . 10
7.1. Normative References . . . . . . . . . . . . . . . . . . . 10
7.2. Informative References . . . . . . . . . . . . . . . . . . 11
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 11
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1. Introduction
The Happy Eyeballs [I-D.ietf-v6ops-happy-eyeballs] specification
notes 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 possible
solutions.
In a dual stack network (i.e., one that contains both IPv4 [RFC0791]
and IPv6 [RFC2460] prefixes and routes), or in an IPv6-only network
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 establishing 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 establishing a session far longer than human patience
normally allows.
This has the effect of discouraging users from enabling IPv6 in their
equipment, or content providers from offering AAAA records for their
services.
This note describes a test to determine how quickly an application
can reliably open sessions 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
application and its host system as a black box. The "happy eyeballs"
question is this: how long does it take an application to open a
session with a server or peer, under best case and worst case
conditions?
The methods defined here make the assumption that the initial
communication set-up of many applications can be summarized by the
measuring the DNS query/response and transport layer handshaking,
because no application-layer communication takes place without these
steps.
The methods and metrics defined in this note are ideally suited for
Laboratory operation, as this affords the greatest degree of control
to modify configurations quickly and produce consistent results.
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However, if the device under test is operated as a single user with
limited query and stream generation, then there's no concern about
overloading production network devices with a single "set of
eyeballs". Therefore, these procedures and metrics MAY be applicable
to production network application, as long as the injected traffic
represents a single user's typical traffic load, and the testers
adhere to the precautions of the relevant network with respect to re-
configuration of devices in production.
2. Measuring Eyeball Happiness
This measurement determines the amount of time it takes an
application to establish 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 lengthy session setup times - in
various application and OS combinations anywhere from multi-second to
half an hour - 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; users will expect this time to be
consistent with their current experience (else, happiness is at
risk).
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 |
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Figure 1: Generic Test Environment
Alice is the unit being measured, the computer running the process
that will establish 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 silently drops datagrams to Bob,
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.
o Path MTU issues
The Path MTU Discovery [RFC1191][RFC1981] matter requires some
explanation. With IPv6, and with IPv4 when "Do Not Fragment" is set,
a router with a message too large for an interface discards it and
replies with an ICMPv4 "Destination Unreachable: Datagram Too Big" or
ICMPv6 "Packet Too Big". If this packet is lost, the source doesn't
know what size to fragment to and has no indication that
fragmentation is required. A configuration for this scenario would
set the MTU on 203.0.113.0/24 or 2001:DB8:0:3::/64 to the smallest
allowed by the address family (576 or 1280) and disable generation of
the indicated ICMP message. Note that [RFC4821] is intended to
address these issues.
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
differently to a TCP RST than to a silent packet loss. Each of these
scenarios should be tested; if doing so is too difficult, the most
important is the silent packet loss case, as it is the worst case.
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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. Bob's
are in DNS, where Alice can find them; Alice's and others may be
there as well, but are not relevant to the test. Routers 1 and 2 are
configured to route the relevant prefixes. Different measurement
trials revise 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 establishment
of 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 establish
a session. This includes the time from Alice's initial DNS request
through one or more attempts to establish a session to the session
being established, 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. |---198.51.100.1---------->| |
4. |---2001:DB8:0:2::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. |---198.51.100.1---------->| |
4. |---2001:DB8:0:2::1------->| |
5. | | |
6. | |--UDP Request, IPv6-->X|<---------
7. | |--UDP Request, IPv6-->X| first
8. | |--UDP Request, IPv6-->X| request/
9. | | | response
10. | |--UDP Request, IPv4--->| success
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 have been
established, 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.
ALL measurement events on the sending and receiving of messages SHALL
be observed at the "Alice" attachment point and time stamps SHOULD be
applied upon reception of the last bit of the IP information field.
Use of a alternate timing reference SHALL be noted.
2.3.1. Metric: Session Setup Interval
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Name: Session Setup Interval
Description: The session setup interval MUST be the time beginning
with the first DNS query sent (observed at Alice's attachment),
and ending with successful transport connection establishment (as
indicated in line 12 of Figure 2, and line 11 of Figure 3). This
interval is defined as the session setup interval.
This test will be run several times, once for each possible
combination of destination address (configured on Bob) and failure
mode (configured on Router 1).
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. If the session is not successfully
opened, possibly due to Alice aborting the attempt, the Session
Setup Interval is considered to be infinite.
Units: Session setup time is measured in milliseconds.
Measurement Point(s): The measurement point is at Alice's LAN
interface, both sending and receiving, observed using a program
such as tcpdump running on Alice or an external analyzer.
Timing: The measurement program or external analyzer MUST run for a
duration sufficient to capture the entire message flow as
described in Section 2.2. Measurement precision MUST be
sufficient to maintain no more than 0.1 ms error over a 60 second
interval. 1 ppm precision would suffice.
2.3.2. 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 establishment of a session as
described in Section 2.3.1.
Methodology: see Session Setup Interval.
Units: Session setup time is measured in milliseconds.
Measurement Point(s): see Session Setup Interval.
Timing: The measurement program or external analyzer MUST run for a
duration sufficient to capture the entire message flow as
described in Section 2.2. Measurement precision MUST be
sufficient to maintain no more than 0.1 ms error over a 60 second
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interval. 1 ppm precision would suffice.
2.3.3. 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 establishment of a session.
Methodology: see Session Setup Interval.
Units: Session setup time is measured in milliseconds.
Measurement Point(s): see Session Setup Interval.
Timing: The measurement program or external analyzer MUST run for a
duration sufficient to capture the entire message flow as
described in Section 2.2. Measurement precision MUST be
sufficient to maintain no more than 0.1 ms error over a 60 second
interval. 1 ppm precision would suffice.
2.3.4. Descriptive Metric: Attempt pattern
Name: Attempt pattern
Description: The Attempt Pattern is a description of the observed
pattern of attempts to establish 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 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: The measurement program or external analyzer MUST run for a
duration sufficient to capture the entire message flow as
described in Section 2.2. Measurement precision MUST be
sufficient to maintain no more than 0.1 ms error over a 60 second
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interval. 1 ppm precision would suffice.
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, Sarah Banks, and Tore Anderson made comments.
6. Change Log
-00: Initial version - November, 2010
-01: Rewritten per suggestions by Al Morton, David Newman, and Sarah
Banks.
-02: Clean-up per working group comments.
-03: Updated per Al Morton's and Tore Anderson's comments.
7. References
7.1. Normative References
[I-D.ietf-v6ops-happy-eyeballs]
Wing, D. and A. Yourtchenko, "Happy Eyeballs: Success with
Dual-Stack Hosts", draft-ietf-v6ops-happy-eyeballs-03
(work in progress), July 2011.
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[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
7.2. Informative References
[RFC0791] Postel, J., "Internet Protocol", STD 5, RFC 791,
September 1981.
[RFC1191] Mogul, J. and S. Deering, "Path MTU discovery", RFC 1191,
November 1990.
[RFC1981] McCann, J., Deering, S., and J. Mogul, "Path MTU Discovery
for IP version 6", RFC 1981, August 1996.
[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.
[RFC4821] Mathis, M. and J. Heffner, "Packetization Layer Path MTU
Discovery", RFC 4821, March 2007.
[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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