Network Working Group S. Poretsky
InternetDraft Allot Communications
Intended status: Informational B. Imhoff
Expires: August 13, 2011 Juniper Networks
K. Michielsen
Cisco Systems
February 16, 2011
Terminology for Benchmarking LinkState IGP Data Plane Route Convergence
draftietfbmwgigpdataplaneconvterm23
Abstract
This document describes the terminology for benchmarking linkstate
Interior Gateway Protocol (IGP) route convergence. The terminology
is to be used for benchmarking IGP convergence time through
externally observable (black box) data plane measurements. The
terminology can be applied to any linkstate IGP, such as
Intermediate System to Intermediate System (ISIS) and Open Shortest
Path First (OSPF).
Status of this Memo
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This InternetDraft will expire on August 13, 2011.
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Table of Contents
1. Introduction and Scope . . . . . . . . . . . . . . . . . . . . 4
2. Existing Definitions . . . . . . . . . . . . . . . . . . . . . 4
3. Term Definitions . . . . . . . . . . . . . . . . . . . . . . . 4
3.1. Convergence Types . . . . . . . . . . . . . . . . . . . . 4
3.1.1. Route Convergence . . . . . . . . . . . . . . . . . . 5
3.1.2. Full Convergence . . . . . . . . . . . . . . . . . . . 5
3.2. Instants . . . . . . . . . . . . . . . . . . . . . . . . . 6
3.2.1. Traffic Start Instant . . . . . . . . . . . . . . . . 6
3.2.2. Convergence Event Instant . . . . . . . . . . . . . . 6
3.2.3. Convergence Recovery Instant . . . . . . . . . . . . . 7
3.2.4. First Route Convergence Instant . . . . . . . . . . . 7
3.3. Transitions . . . . . . . . . . . . . . . . . . . . . . . 8
3.3.1. Convergence Event Transition . . . . . . . . . . . . . 8
3.3.2. Convergence Recovery Transition . . . . . . . . . . . 9
3.4. Interfaces . . . . . . . . . . . . . . . . . . . . . . . . 9
3.4.1. Local Interface . . . . . . . . . . . . . . . . . . . 9
3.4.2. Remote Interface . . . . . . . . . . . . . . . . . . . 9
3.4.3. Preferred Egress Interface . . . . . . . . . . . . . . 10
3.4.4. NextBest Egress Interface . . . . . . . . . . . . . . 10
3.5. Benchmarking Methods . . . . . . . . . . . . . . . . . . . 11
3.5.1. RateDerived Method . . . . . . . . . . . . . . . . . 11
3.5.2. LossDerived Method . . . . . . . . . . . . . . . . . 13
3.5.3. RouteSpecific LossDerived Method . . . . . . . . . . 14
3.6. Benchmarks . . . . . . . . . . . . . . . . . . . . . . . . 15
3.6.1. Full Convergence Time . . . . . . . . . . . . . . . . 15
3.6.2. First Route Convergence Time . . . . . . . . . . . . . 16
3.6.3. RouteSpecific Convergence Time . . . . . . . . . . . 17
3.6.4. LossDerived Convergence Time . . . . . . . . . . . . 18
3.6.5. Route Loss of Connectivity Period . . . . . . . . . . 19
3.6.6. LossDerived Loss of Connectivity Period . . . . . . . 20
3.7. Measurement Terms . . . . . . . . . . . . . . . . . . . . 21
3.7.1. Convergence Event . . . . . . . . . . . . . . . . . . 21
3.7.2. Convergence Packet Loss . . . . . . . . . . . . . . . 21
3.7.3. Connectivity Packet Loss . . . . . . . . . . . . . . . 22
3.7.4. Packet Sampling Interval . . . . . . . . . . . . . . . 22
3.7.5. Sustained Convergence Validation Time . . . . . . . . 23
3.7.6. Forwarding Delay Threshold . . . . . . . . . . . . . . 24
3.8. Miscellaneous Terms . . . . . . . . . . . . . . . . . . . 24
3.8.1. Impaired Packet . . . . . . . . . . . . . . . . . . . 24
4. Security Considerations . . . . . . . . . . . . . . . . . . . 24
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 25
6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 25
7. Normative References . . . . . . . . . . . . . . . . . . . . . 25
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 26
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1. Introduction and Scope
This document is a companion to [Po11m] which the methodology to be
used for benchmarking linkstate Interior Gateway Protocol (IGP)
Convergence by observing the data plane. The purpose of this
document is to introduce new terms required to complete execution of
the LinkState IGP Data Plane Route Convergence methodology [Po11m].
IGP convergence time is measured by observing the dataplane through
the Device Under Test (DUT) at the Tester. The methodology and
terminology to be used for benchmarking IGP Convergence can be
applied to IPv4 and IPv6 traffic and linkstate IGPs such as
Intermediate System to Intermediate System (ISIS) [Ca90][Ho08], Open
Shortest Path First (OSPF) [Mo98][Co08], and others.
2. Existing Definitions
This document uses existing terminology defined in other IETF
documents. Examples include, but are not limited to:
Throughput [Ref.[Br91], section 3.17]
Offered Load [Ref.[Ma98], section 3.5.2]
Forwarding Rate [Ref.[Ma98], section 3.6.1]
Device Under Test (DUT) [Ref.[Ma98], section 3.1.1]
System Under Test (SUT) [Ref.[Ma98], section 3.1.2]
OutofOrder Packet [Ref.[Po06], section 3.3.4]
Duplicate Packet [Ref.[Po06], section 3.3.5]
Stream [Ref.[Po06], section 3.3.2]
Forwarding Delay [Ref.[Po06], section 3.2.4]
IP Packet Delay Variation (IPDV) [Ref.[De02], section 1.2]
Loss Period [Ref.[Ko02], section 4]
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 BCP 14, RFC 2119
[Br97]. RFC 2119 defines the use of these key words to help make the
intent of standards track documents as clear as possible. While this
document uses these keywords, this document is not a standards track
document.
3. Term Definitions
3.1. Convergence Types
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3.1.1. Route Convergence
Definition:
The process of updating all components of the router, including the
Routing Information Base (RIB) and Forwarding Information Base (FIB),
along with software and hardware tables, with the most recent route
change(s) such that forwarding for a route entry is successful on the
NextBest Egress Interface [Section 3.4.4].
Discussion:
In general IGP convergence does not necessarily result in a change in
forwarding. But the test cases in [Po11m] are specified such that
the IGP convergence results in a change of egress interface for the
measurement dataplane traffic. Due to this property of the test case
specifications, Route Convergence can be observed externally by the
rerouting of the measurement dataplane traffic to the Nextbest
Egress Interface [Section 3.4.4].
Measurement Units: N/A
See Also:
NextBest Egress Interface, Full Convergence
3.1.2. Full Convergence
Definition:
Route Convergence for all routes in the Forwarding Information Base
(FIB).
Discussion:
In general IGP convergence does not necessarily result in a change in
forwarding. But the test cases in [Po11m] are specified such that
the IGP convergence results in a change of egress interface for the
measurement dataplane traffic. Due to this property of the test
cases specifications, Full Convergence can be observed externally by
the rerouting of the measurement dataplane traffic to the Nextbest
Egress Interface [Section 3.4.4].
Measurement Units: N/A
See Also:
NextBest Egress Interface, Route Convergence
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3.2. Instants
3.2.1. Traffic Start Instant
Definition:
The time instant the Tester sends out the first data packet to the
Device Under Test (DUT).
Discussion:
If using the LossDerived Method [Section 3.5.2] or the Route
Specific LossDerived Method [Section 3.5.3] to benchmark IGP
convergence time, and the applied Convergence Event [Section 3.7.1]
does not cause instantaneous traffic loss for all routes at the
Convergence Event Instant [Section 3.2.2] then the Tester SHOULD
collect a timestamp on the Traffic Start Instant in order to measure
the period of time between the Traffic Start Instant and Convergence
Event Instant.
Measurement Units:
seconds (and fractions), reported with resolution sufficient to
distinguish between different instants
See Also:
LossDerived Method, RouteSpecific LossDerived Method, Convergence
Event, Convergence Event Instant
3.2.2. Convergence Event Instant
Definition:
The time instant that a Convergence Event [Section 3.7.1] occurs.
Discussion:
If the Convergence Event [Section 3.7.1] causes instantaneous traffic
loss on the Preferred Egress Interface [Section 3.4.3], the
Convergence Event Instant is observable from the data plane as the
instant that no more packets are received on the Preferred Egress
Interface.
The Tester SHOULD collect a timestamp on the Convergence Event
Instant if it the Convergence Event does not cause instantaneous
traffic loss on the Preferred Egress Interface [Section 3.4.3].
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Measurement Units:
seconds (and fractions), reported with resolution sufficient to
distinguish between different instants
See Also:
Convergence Event, Preferred Egress Interface
3.2.3. Convergence Recovery Instant
Definition:
The time instant that Full Convergence [Section 3.1.2] has completed.
Discussion:
The Full Convergence completed state MUST be maintained for an
interval of duration equal to the Sustained Convergence Validation
Time [Section 3.7.5] in order to validate the Convergence Recovery
Instant.
The Convergence Recovery Instant is observable from the data plane as
the instant the Device Under Test (DUT) forwards traffic to all
destinations over the NextBest Egress Interface [Section 3.4.4]
without impairments.
Measurement Units:
seconds (and fractions), reported with resolution sufficient to
distinguish between different instants
See Also:
Sustained Convergence Validation Time, Full Convergence, NextBest
Egress Interface
3.2.4. First Route Convergence Instant
Definition:
The time instant the first route entry completes Route Convergence
[Section 3.1.1]
Discussion:
Any route may be the first to complete Route Convergence. The First
Route Convergence Instant is observable from the data plane as the
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instant that the first packet that is not an Impaired Packet
[Section 3.8.1] is received from the NextBest Egress Interface
[Section 3.4.4] or, for the test cases with Equal Cost MultiPath
(ECMP) or Parallel Links, the instant that the Forwarding Rate on the
NextBest Egress Interface [Section 3.4.4] starts to increase.
Measurement Units:
seconds (and fractions), reported with resolution sufficient to
distinguish between different instants
See Also:
Route Convergence, Impaired Packet, NextBest Egress Interface
3.3. Transitions
3.3.1. Convergence Event Transition
Definition:
A time interval following a Convergence Event [Section 3.7.1] in
which Forwarding Rate on the Preferred Egress Interface
[Section 3.4.3] gradually reduces to zero.
Discussion:
The Forwarding Rate during a Convergence Event Transition may or may
not decrease linearly.
The Forwarding Rate observed on the Device Under Test (DUT) egress
interface(s) may or may not decrease to zero.
The Offered Load, the number of routes, and the Packet Sampling
Interval [Section 3.7.4] influence the observations of the
Convergence Event Transition using the RateDerived Method
[Section 3.5.1].
Measurement Units: seconds (and fractions)
See Also:
Convergence Event, Preferred Egress Interface, Packet Sampling
Interva, RateDerived Method
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3.3.2. Convergence Recovery Transition
Definition:
A time interval following the First Route Convergence Instant
[Section 3.4.4] in which Forwarding Rate on the Device Under Test
(DUT) egress interface(s) gradually increases to equal the Offered
Load.
Discussion:
The Forwarding Rate observed during a Convergence Recovery Transition
may or may not increase linearly.
The Offered Load, the number of routes, and the Packet Sampling
Interval [Section 3.7.4] influence the observations of the
Convergence Recovery Transition using the RateDerived Method
[Section 3.5.1].
Measurement Units: seconds (and fractions)
See Also:
First Route Convergence Instant, Packet Sampling Interva, Rate
Derived Method
3.4. Interfaces
3.4.1. Local Interface
Definition:
An interface on the Device Under Test (DUT).
Discussion:
A failure of a Local Interface indicates that the failure occurred
directly on the Device Under Test (DUT).
Measurement Units: N/A
See Also: Remote Interface
3.4.2. Remote Interface
Definition:
An interface on a neighboring router that is not directly connected
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to any interface on the Device Under Test (DUT).
Discussion:
A failure of a Remote Interface indicates that the failure occurred
on a neighbor router's interface that is not directly connected to
the Device Under Test (DUT).
Measurement Units: N/A
See Also: Local Interface
3.4.3. Preferred Egress Interface
Definition:
The outbound interface from the Device Under Test (DUT) for traffic
routed to the preferred nexthop.
Discussion:
The Preferred Egress Interface is the egress interface prior to a
Convergence Event [Section 3.7.1].
Measurement Units: N/A
See Also: Convergence Event, NextBest Egress Interface
3.4.4. NextBest Egress Interface
Definition:
The outbound interface or set of outbound interfaces in an Equal Cost
Multipath (ECMP) set or parallel link set of the Device Under Test
(DUT) for traffic routed to the secondbest nexthop.
Discussion:
The NextBest Egress Interface becomes the egress interface after a
Convergence Event [Section 3.4.4].
For the test cases in [Po11m] using test topologies with an ECMP set
or parallel link set, the term Preferred Egress Interface refers to
all members of the link set.
Measurement Units: N/A
See Also: Convergence Event, Preferred Egress Interface
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3.5. Benchmarking Methods
3.5.1. RateDerived Method
Definition:
The method to calculate convergence time benchmarks from observing
Forwarding Rate each Packet Sampling Interval [Section 3.7.4].
Discussion:
Figure 1 shows an example of the Forwarding Rate change in time
during convergence as observed when using the RateDerived Method.
^ Traffic Convergence
Fwd  Start Recovery
Rate  Instant Instant
 Offered ^ ^
 Load > \ /
 \ /< Convergence
 \ Packet / Recovery
 Convergence >\ Loss / Transition
 Event \ /
 Transition \/ < Max Packet Loss

+>
^ ^ time
Convergence First Route
Event Instant Convergence Instant
Figure 1: RateDerived Convergence Graph
To enable collecting statistics of OutofOrder Packets per flow (See
[Th00], Section 3) the Offered Load SHOULD consist of multiple
Streams [Po06] and each Stream SHOULD consist of a single flow . If
sending multiple Streams, the measured traffic statistics for all
Streams MUST be added together.
The destination addresses for the Offered Load MUST be distributed
such that all routes or a statistically representative subset of all
routes are matched and each of these routes is offered an equal share
of the Offered Load. It is RECOMMENDED to send traffic to all
routes, but a statistically representative subset of all routes can
be used if required.
At least one packet per route for all routes matched in the Offered
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Load MUST be offered to the DUT within each Packet Sampling Interval.
For maximum accuracy the value for the Packet Sampling Interval
SHOULD be as small as possible, but the presence of IP Packet Delay
Variation (IPDV) [De02] may enforce using a larger Packet Sampling
Interval.
The Offered Load, IPDV, the number of routes, and the Packet Sampling
Interval influence the observations for the RateDerived Method. It
may be difficult to identify the different convergence time instants
in the RateDerived Convergence Graph. For example, it is possible
that a Convergence Event causes the Forwarding Rate to drop to zero,
while this may not be observed in the Forwarding Rate measurements if
the Packet Sampling Interval is too large.
IPDV causes fluctuations in the number of received packets during
each Packet Sampling Interval. To account for the presence of IPDV
in determining if a convergence instant has been reached, Forwarding
Delay SHOULD be observed during each Packet Sampling Interval. The
minimum and maximum number of packets expected in a Packet Sampling
Interval in presence of IPDV can be calculated with Equation 1.
number of packets expected in a Packet Sampling Interval
in presence of IP Packet Delay Variation
= expected number of packets without IP Packet Delay Variation
+/( (maxDelay  minDelay) * Offered Load)
with minDelay and maxDelay the minimum resp. maximum Forwarding Delay
of packets received during the Packet Sampling Interval
Equation 1
To determine if a convergence instant has been reached the number of
packets received in a Packet Sampling Interval is compared with the
range of expected number of packets calculated in Equation 1.
If packets are going over multiple ECMP members and one or more of
the members has failed then the number of received packets during
each Packet Sampling Interval may vary, even excluding presence of
IPDV. To prevent fluctuation of the number of received packets
during each Packet Sampling Interval for this reason, the Packet
Sampling Interval duration SHOULD be a whole multiple of the time
between two consecutive packets sent to the same destination.
Metrics measured at the Packet Sampling Interval MUST include
Forwarding Rate and Impaired Packet count.
To measure convergence time benchmarks for Convergence Events
[Section 3.7.1] that do not cause instantaneous traffic loss for all
routes at the Convergence Event Instant, the Tester SHOULD collect a
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timestamp of the Convergence Event Instant [Section 3.2.2] and the
Tester SHOULD observe Forwarding Rate separately on the NextBest
Egress Interface.
Since the RateDerived Method does not distinguish between individual
traffic destinations, it SHOULD NOT be used for any route specific
measurements. Therefor RateDerived Method SHOULD NOT be used to
benchmark Route Loss of Connectivity Period [Section 3.6.5].
Measurement Units: N/A
See Also:
Packet Sampling Interval, Convergence Event, Convergence Event
Instant, NextBest Egress Interface, Route Loss of Connectivity
Period
3.5.2. LossDerived Method
Definition:
The method to calculate the LossDerived Convergence Time
[Section 3.6.4] and LossDerived Loss of Connectivity Period
[Section 3.6.6] benchmarks from the amount of Impaired Packets
[Section 3.8.1].
Discussion:
To enable collecting statistics of OutofOrder Packets per flow (See
[Th00], Section 3) the Offered Load SHOULD consist of multiple
Streams [Po06] and each Stream SHOULD consist of a single flow . If
sending multiple Streams, the measured traffic statistics for all
Streams MUST be added together.
The destination addresses for the Offered Load MUST be distributed
such that all routes or a statistically representative subset of all
routes are matched and each of these routes is offered an equal share
of the Offered Load. It is RECOMMENDED to send traffic to all
routes, but a statistically representative subset of all routes can
be used if required.
LossDerived Method SHOULD always be combined with RateDerived
Method in order to observe Full Convergence completion. The total
amount of Convergence Packet Loss is collected after Full Convergence
completion.
To measure convergence time and loss of connectivity benchmarks for
Convergence Events that cause instantaneous traffic loss for all
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routes at the Convergence Event Instant, the Tester SHOULD observe
Impaired Packet count on all DUT egress interfaces (see Connectivity
Packet Loss [Section 3.7.3]).
To measure convergence time benchmarks for Convergence Events that do
not cause instantaneous traffic loss for all routes at the
Convergence Event Instant, the Tester SHOULD collect timestamps of
the Start Traffic Instant and of the Convergence Event Instant, and
the Tester SHOULD observe Impaired Packet count separately on the
NextBest Egress Interface (See Convergence Packet Loss
[Section 3.7.2]).
Since LossDerived Method does not distinguish between traffic
destinations and the Impaired Packet statistics are only collected
after Full Convergence completion, this method can only be used to
measure average values over all routes. For these reasons Loss
Derived Method can only be used to benchmark LossDerived Convergence
Time [Section 3.6.4] and LossDerived Loss of Connectivity Period
[Section 3.6.6].
Note that the LossDerived Method measures an average over all
routes, including the routes that may not be impacted by the
Convergence Event, such as routes via nonimpacted members of ECMP or
parallel links.
Measurement Units: N/A
See Also:
LossDerived Convergence Time, LossDerived Loss of Connectivity
Period, Connectivity Packet Loss, Convergence Packet Loss
3.5.3. RouteSpecific LossDerived Method
Definition:
The method to calculate the RouteSpecific Convergence Time
[Section 3.6.3] benchmark from the amount of Impaired Packets
[Section 3.8.1] during convergence for a specific route entry.
Discussion:
To benchmark RouteSpecific Convergence Time, the Tester provides an
Offered Load that consists of multiple Streams [Po06]. Each Stream
has a single destination address matching a different route entry,
for all routes or a statistically representative subset of all
routes. Each Stream SHOULD consist of a single flow (See [Th00],
Section 3). Convergence Packet Loss is measured for each Stream
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separately.
RouteSpecific LossDerived Method SHOULD always be combined with
RateDerived Method in order to observe Full Convergence completion.
The total amount of Convergence Packet Loss [Section 3.7.2] for each
Stream is collected after Full Convergence completion.
RouteSpecific LossDerived Method is the RECOMMENDED method to
measure convergence time benchmarks.
To measure convergence time and loss of connectivity benchmarks for
Convergence Events that cause instantaneous traffic loss for all
routes at the Convergence Event Instant, the Tester SHOULD observe
Impaired Packet count on all DUT egress interfaces (see Connectivity
Packet Loss [Section 3.7.3]).
To measure convergence time benchmarks for Convergence Events that do
not cause instantaneous traffic loss for all routes at the
Convergence Event Instant, the Tester SHOULD collect timestamps of
the Start Traffic Instant and of the Convergence Event Instant, and
the Tester SHOULD observe packet loss separately on the NextBest
Egress Interface (See Convergence Packet Loss [Section 3.7.2]).
Since RouteSpecific LossDerived Method uses traffic streams to
individual routes, it observes Impaired Packet count as it would be
experienced by a network user. For this reason RouteSpecific Loss
Derived Method is RECOMMENDED to measure RouteSpecific Convergence
Time benchmarks and Route Loss of Connectivity Period benchmarks.
Measurement Units: N/A
See Also:
RouteSpecific Convergence Time, Route Loss of Connectivity Period,
Connectivity Packet Loss, Convergence Packet Loss
3.6. Benchmarks
3.6.1. Full Convergence Time
Definition:
The time duration of the period between the Convergence Event Instant
and the Convergence Recovery Instant as observed using the Rate
Derived Method.
Discussion:
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Using the RateDerived Method, Full Convergence Time can be
calculated as the time difference between the Convergence Event
Instant and the Convergence Recovery Instant, as shown in Equation 2.
Full Convergence Time =
Convergence Recovery Instant  Convergence Event Instant
Equation 2
The Convergence Event Instant can be derived from the Forwarding Rate
observation or from a timestamp collected by the Tester.
For the test cases described in [Po11m], it is expected that Full
Convergence Time equals the maximum RouteSpecific Convergence Time
when benchmarking all routes in FIB using the RouteSpecific Loss
Derived Method.
It is not possible to measure Full Convergence Time using the Loss
Derived Method.
Measurement Units: seconds (and fractions)
See Also:
Full Convergence, RateDerived Method, RouteSpecific LossDerived
Method, Convergence Event Instant, Convergence Recovery Instant
3.6.2. First Route Convergence Time
Definition:
The duration of the period between the Convergence Event Instant and
the First Route Convergence Instant as observed using the Rate
Derived Method.
Discussion:
Using the RateDerived Method, First Route Convergence Time can be
calculated as the time difference between the Convergence Event
Instant and the First Route Convergence Instant, as shown with
Equation 3.
First Route Convergence Time =
First Route Convergence Instant  Convergence Event Instant
Equation 3
The Convergence Event Instant can be derived from the Forwarding Rate
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observation or from a timestamp collected by the Tester.
For the test cases described in [Po11m], it is expected that First
Route Convergence Time equals the minimum RouteSpecific Convergence
Time when benchmarking all routes in FIB using the RouteSpecific
LossDerived Method.
It is not possible to measure First Route Convergence Time using the
LossDerived Method.
Measurement Units: seconds (and fractions)
See Also:
RateDerived Method, RouteSpecific LossDerived Method, Convergence
Event Instant, First Route Convergence Instant
3.6.3. RouteSpecific Convergence Time
Definition:
The amount of time it takes for Route Convergence to be completed for
a specific route, as calculated from the amount of Impaired Packets
[Section 3.8.1] during convergence for a single route entry.
Discussion:
RouteSpecific Convergence Time can only be measured using the Route
Specific LossDerived Method.
If the applied Convergence Event causes instantaneous traffic loss
for all routes at the Convergence Event Instant, Connectivity Packet
Loss should be observed. Connectivity Packet Loss is the combined
Impaired Packet count observed on Preferred Egress Interface and
NextBest Egress Interface. When benchmarking RouteSpecific
Convergence Time, Connectivity Packet Loss is measured and Equation 4
is applied for each measured route. The calculation is equal to
Equation 8 in Section 3.6.5.
RouteSpecific Convergence Time =
Connectivity Packet Loss for specific route/Offered Load per route
Equation 4
If the applied Convergence Event does not cause instantaneous traffic
loss for all routes at the Convergence Event Instant, then the Tester
SHOULD collect timestamps of the Traffic Start Instant and of the
Convergence Event Instant, and the Tester SHOULD observe Convergence
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Packet Loss separately on the NextBest Egress Interface. When
benchmarking RouteSpecific Convergence Time, Convergence Packet Loss
is measured and Equation 5 is applied for each measured route.
RouteSpecific Convergence Time =
Convergence Packet Loss for specific route/Offered Load per route
 (Convergence Event Instant  Traffic Start Instant)
Equation 5
The RouteSpecific Convergence Time benchmarks enable minimum,
maximum, average, and median convergence time measurements to be
reported by comparing the results for the different route entries.
It also enables benchmarking of convergence time when configuring a
priority value for route entry(ies). Since multiple RouteSpecific
Convergence Times can be measured it is possible to have an array of
results. The format for reporting RouteSpecific Convergence Time is
provided in [Po11m].
Measurement Units: seconds (and fractions)
See Also:
RouteSpecific LossDerived Method, Convergence Event, Convergence
Event Instant, Convergence Packet Loss, Connectivity Packet Loss,
Route Convergence
3.6.4. LossDerived Convergence Time
Definition:
The average Route Convergence time for all routes in the Forwarding
Information Base (FIB), as calculated from the amount of Impaired
Packets [Section 3.8.1] during convergence.
Discussion:
LossDerived Convergence Time is measured using the LossDerived
Method.
If the applied Convergence Event causes instantaneous traffic loss
for all routes at the Convergence Event Instant, Connectivity Packet
Loss [Section 3.7.3] should be observed. Connectivity Packet Loss is
the combined Impaired Packet count observed on Preferred Egress
Interface and NextBest Egress Interface. When benchmarking Loss
Derived Convergence Time, Connectivity Packet Loss is measured and
Equation 6 is applied.
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LossDerived Convergence Time =
Connectivity Packet Loss/Offered Load
Equation 6
If the applied Convergence Event does not cause instantaneous traffic
loss for all routes at the Convergence Event Instant, then the Tester
SHOULD collect timestamps of the Start Traffic Instant and of the
Convergence Event Instant and the Tester SHOULD observe Convergence
Packet Loss [Section 3.7.2] separately on the NextBest Egress
Interface. When benchmarking LossDerived Convergence Time,
Convergence Packet Loss is measured and Equation 7 is applied.
LossDerived Convergence Time =
Convergence Packet Loss/Offered Load
 (Convergence Event Instant  Traffic Start Instant)
Equation 7
Measurement Units: seconds (and fractions)
See Also:
Convergence Packet Loss, Connectivity Packet Loss, Route Convergence,
LossDerived Method
3.6.5. Route Loss of Connectivity Period
Definition:
The time duration of packet impairments for a specific route entry
following a Convergence Event until Full Convergence completion, as
observed using the RouteSpecific LossDerived Method.
Discussion:
In general the Route Loss of Connectivity Period is not equal to the
RouteSpecific Convergence Time. If the DUT continues to forward
traffic to the Preferred Egress Interface after the Convergence Event
is applied then the Route Loss of Connectivity Period will be smaller
than the RouteSpecific Convergence Time. This is also specifically
the case after reversing a failure event.
The Route Loss of Connectivity Period may be equal to the Route
Specific Convergence Time if, as a characteristic of the Convergence
Event, traffic for all routes starts dropping instantaneously on the
Convergence Event Instant. See discussion in [Po11m].
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For the test cases described in [Po11m] the Route Loss of
Connectivity Period is expected to be a single Loss Period [Ko02].
When benchmarking Route Loss of Connectivity Period, Connectivity
Packet Loss is measured for each route and Equation 8 is applied for
each measured route entry. The calculation is equal to Equation 4 in
Section 3.6.3.
Route Loss of Connectivity Period =
Connectivity Packet Loss for specific route/Offered Load per route
Equation 8
Route Loss of Connectivity Period SHOULD be measured using Route
Specific LossDerived Method.
Measurement Units: seconds (and fractions)
See Also:
RouteSpecific Convergence Time, RouteSpecific LossDerived Method,
Connectivity Packet Loss
3.6.6. LossDerived Loss of Connectivity Period
Definition:
The average time duration of packet impairments for all routes
following a Convergence Event until Full Convergence completion, as
observed using the LossDerived Method.
Discussion:
In general the LossDerived Loss of Connectivity Period is not equal
to the LossDerived Convergence Time. If the DUT continues to
forward traffic to the Preferred Egress Interface after the
Convergence Event is applied then the LossDerived Loss of
Connectivity Period will be smaller than the LossDerived Convergence
Time. This is also specifically the case after reversing a failure
event.
The LossDerived Loss of Connectivity Period may be equal to the
LossDerived Convergence Time if, as a characteristic of the
Convergence Event, traffic for all routes starts dropping
instantaneously on the Convergence Event Instant. See discussion in
[Po11m].
For the test cases described in [Po11m] each route's Route Loss of
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Connectivity Period is expected to be a single Loss Period [Ko02].
When benchmarking LossDerived Loss of Connectivity Period,
Connectivity Packet Loss is measured for all routes and Equation 9 is
applied. The calculation is equal to Equation 6 in Section 3.6.4.
LossDerived Loss of Connectivity Period =
Connectivity Packet Loss for all routes/Offered Load
Equation 9
LossDerived Loss of Connectivity Period SHOULD be measured using
LossDerived Method.
Measurement Units: seconds (and fractions)
See Also:
LossDerived Convergence Time, LossDerived Method, Connectivity
Packet Loss
3.7. Measurement Terms
3.7.1. Convergence Event
Definition:
The occurrence of an event in the network that will result in a
change in the egress interface of the Device Under Test (DUT) for
routed packets.
Discussion:
All test cases in [Po11m] are defined such that a Convergence Event
results in a change of egress interface of the DUT. Local or remote
triggers that cause a route calculation which does not result in a
change in forwarding are not considered.
Measurement Units: N/A
See Also: Convergence Event Instant
3.7.2. Convergence Packet Loss
Definition:
The number of Impaired Packets [Section 3.8.1] as observed on the
NextBest Egress Interface of the DUT during convergence.
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Discussion:
An Impaired Packet is considered as a lost packet.
Measurement Units: number of packets
See Also:
Connectivity Packet Loss
3.7.3. Connectivity Packet Loss
Definition:
The number of Impaired Packets observed on all DUT egress interfaces
during convergence.
Discussion:
An Impaired Packet is considered as a lost packet. Connectivity
Packet Loss is equal to Convergence Packet Loss if the Convergence
Event causes instantaneous traffic loss for all egress interfaces of
the DUT except for the NextBest Egress Interface.
Measurement Units: number of packets
See Also:
Convergence Packet Loss
3.7.4. Packet Sampling Interval
Definition:
The interval at which the Tester (test equipment) polls to make
measurements for arriving packets.
Discussion:
At least one packet per route for all routes matched in the Offered
Load MUST be offered to the DUT within the Packet Sampling Interval.
Metrics measured at the Packet Sampling Interval MUST include
Forwarding Rate and received packets.
Packet Sampling Interval can influence the convergence graph as
observed with the RateDerived Method. This is particularly true
when implementations complete Full Convergence in less time than the
Packet Sampling Interval. The Convergence Event Instant and First
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Route Convergence Instant may not be easily identifiable and the
RateDerived Method may produce a larger than actual convergence
time.
Using a small Packet Sampling Interval in the presence of IPDV [De02]
may cause fluctuations of the Forwarding Rate observation and can
prevent correct observation of the different convergence time
instants.
The value of the Packet Sampling Interval only contributes to the
measurement accuracy of the RateDerived Method. For maximum
accuracy the value for the Packet Sampling Interval SHOULD be as
small as possible, but the presence of IPDV may enforce using a
larger Packet Sampling Interval.
Measurement Units: seconds (and fractions)
See Also: RateDerived Method
3.7.5. Sustained Convergence Validation Time
Definition:
The amount of time for which the completion of Full Convergence is
maintained without additional Impaired Packets being observed.
Discussion:
The purpose of the Sustained Convergence Validation Time is to
produce convergence benchmarks protected against fluctuation in
Forwarding Rate after the completion of Full Convergence is observed.
The RECOMMENDED Sustained Convergence Validation Time to be used is
the time to send 5 consecutive packets to each destination with a
minimum of 5 seconds. The Benchmarking Methodology Working Group
(BMWG) selected 5 seconds based upon [Br99] which recommends waiting
2 seconds for residual frames to arrive (this is the Forwarding Delay
Threshold for the last packet sent) and 5 seconds for DUT
restabilization.
Measurement Units: seconds (and fractions)
See Also:
Full Convergence, Convergence Recovery Instant
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3.7.6. Forwarding Delay Threshold
Definition:
The maximum waiting time threshold used to distinguish between
packets with very long delay and lost packets that will never arrive.
Discussion:
Applying a Forwarding Delay Threshold allows to consider packets with
a too large Forwarding Delay as being lost, as is required for some
applications (e.g. voice, video, etc.). The Forwarding Delay
Threshold is a parameter of the methodology, and it MUST be reported.
[Br99] recommends waiting 2 seconds for residual frames to arrive.
Measurement Units: seconds (and fractions)
See Also:
Convergence Packet Loss, Connectivity Packet Loss
3.8. Miscellaneous Terms
3.8.1. Impaired Packet
Definition:
A packet that experienced at least one of the following impairments:
loss, excessive Forwarding Delay, corruption, duplication,
reordering.
Discussion:
A lost packet, a packet with a Forwarding Delay exceeding the
Forwarding Delay Threshold, a corrupted packet, a Duplicate Packet
[Po06], and an OutofOrder Packet [Po06] are Impaired Packets.
Packet ordering is observed for each individual flow (See [Th00],
Section 3) of the Offered Load.
Measurement Units: N/A
See Also: Forwarding Delay Threshold
4. Security Considerations
Benchmarking activities as described in this memo are limited to
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technology characterization using controlled stimuli in a laboratory
environment, with dedicated address space and the constraints
specified in the sections above.
The benchmarking network topology will be an independent test setup
and MUST NOT be connected to devices that may forward the test
traffic into a production network, or misroute traffic to the test
management network.
Further, benchmarking is performed on a "blackbox" basis, relying
solely on measurements observable external to the DUT/SUT.
Special capabilities SHOULD NOT exist in the DUT/SUT specifically for
benchmarking purposes. Any implications for network security arising
from the DUT/SUT SHOULD be identical in the lab and in production
networks.
5. IANA Considerations
This document requires no IANA considerations.
6. Acknowledgements
Thanks to Sue Hares, Al Morton, Kevin Dubray, Ron Bonica, David Ward,
Peter De Vriendt, Anuj Dewagan, Adrian Farrel, Stewart Bryant,
Francis Dupont, and the Benchmarking Methodology Working Group for
their contributions to this work.
7. Normative References
[Br91] Bradner, S., "Benchmarking terminology for network
interconnection devices", RFC 1242, July 1991.
[Br97] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[Br99] Bradner, S. and J. McQuaid, "Benchmarking Methodology for
Network Interconnect Devices", RFC 2544, March 1999.
[Ca90] Callon, R., "Use of OSI ISIS for routing in TCP/IP and dual
environments", RFC 1195, December 1990.
[Co08] Coltun, R., Ferguson, D., Moy, J., and A. Lindem, "OSPF for
IPv6", RFC 5340, July 2008.
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[De02] Demichelis, C. and P. Chimento, "IP Packet Delay Variation
Metric for IP Performance Metrics (IPPM)", RFC 3393,
November 2002.
[Ho08] Hopps, C., "Routing IPv6 with ISIS", RFC 5308,
October 2008.
[Ko02] Koodli, R. and R. Ravikanth, "Oneway Loss Pattern Sample
Metrics", RFC 3357, August 2002.
[Ma98] Mandeville, R., "Benchmarking Terminology for LAN Switching
Devices", RFC 2285, February 1998.
[Mo98] Moy, J., "OSPF Version 2", STD 54, RFC 2328, April 1998.
[Po06] Poretsky, S., Perser, J., Erramilli, S., and S. Khurana,
"Terminology for Benchmarking Networklayer Traffic Control
Mechanisms", RFC 4689, October 2006.
[Po11m] Poretsky, S., Imhoff, B., and K. Michielsen, "Benchmarking
Methodology for LinkState IGP Data Plane Route
Convergence", draftietfbmwgigpdataplaneconvmeth23
(work in progress), January 2011.
[Th00] Thaler, D. and C. Hopps, "Multipath Issues in Unicast and
Multicast NextHop Selection", RFC 2991, November 2000.
Authors' Addresses
Scott Poretsky
Allot Communications
67 South Bedford Street, Suite 400
Burlington, MA 01803
USA
Phone: + 1 508 309 2179
Email: sporetsky@allot.com
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Brent Imhoff
Juniper Networks
1194 North Mathilda Ave
Sunnyvale, CA 94089
USA
Phone: + 1 314 378 2571
Email: bimhoff@planetspork.com
Kris Michielsen
Cisco Systems
6A De Kleetlaan
Diegem, BRABANT 1831
Belgium
Email: kmichiel@cisco.com
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