 1/draftietfbmwgigpdataplaneconvterm16.txt 20090309 05:12:14.000000000 +0100
+++ 2/draftietfbmwgigpdataplaneconvterm17.txt 20090309 05:12:14.000000000 +0100
@@ 1,454 +1,459 @@
Network Working Group S. Poretsky
Internet Draft Allot Communications
+ Expires: September 08, 2009
Intended Status: Informational Brent Imhoff
Juniper Networks
 October 15, 2008
+ March 08, 2009
Terminology for Benchmarking
LinkState IGP Data Plane Route Convergence


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ABSTRACT
This document describes the terminology for benchmarking 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 ISIS and OSPF.
LinkState IGP Data Plane Route Convergence
Table of Contents
 1. Introduction .................................................2
 2. Existing definitions .........................................3
 3. Term definitions..............................................4
 3.1 Convergence Event.........................................4
 3.2 Route Convergence.........................................4
 3.3 Full Convergence..........................................5
 3.4 Network Convergence.......................................5
 3.5 RouteSpecific Convergence................................6
 3.6 Packet Loss...............................................7
 3.7 Convergence Packet Loss...................................7
 3.8 Convergence Event Instant.................................8
 3.9 Convergence Recovery Instant..............................8
 3.10 First Route Convergence Instant..........................9
 3.11 Convergence Event Transition.............................9
 3.12 Convergence Recovery Transition..........................10
 3.13 RateDerived Convergence Time............................10
 3.14 LossDerived Convergence Time............................11
 3.15 RouteSpecific Convergence Time..........................12
 3.16 Sustained Convergence Validation Time....................13
 3.17 First Route Convergence Time.............................14
 3.18 Reversion Convergence Time...............................15
 3.19 Packet Sampling Interval.................................15
 3.20 Local Interface..........................................16
 3.21 Neighbor Interface.......................................16
 3.22 Remote Interface.........................................17
 3.23 Preferred Egress Interface...............................17
 3.24 NextBest Egress Interface...............................17
 3.25 Stale Forwarding.........................................18
 3.26 Nested Convergence Events................................18
+ 1. Introduction and Scope........................................3
+ 2. Existing Definitions .........................................4
+ 3. Term Definitions..............................................4
+ 3.1 States
+ 3.1.1 Route Convergence....................................4
+ 3.1.2 Full Convergence.....................................5
+ 3.1.3 Network Convergence..................................5
+ 3.1.4 RouteSpecific Convergence...........................6
+ 3.1.5 Stale Forwarding.....................................6
+ 3.2 Events
+ 3.2.1 Convergence Event....................................7
+ 3.2.2 Convergence Event Trigger............................7
+ 3.2.3 Convergence Event Instant............................8
+ 3.2.4 Convergence Recovery Instant.........................8
+ 3.2.5 First Route Convergence Instant......................9
+ 3.2.6 Convergence Event Transition.........................9
+ 3.2.7 Convergence Recovery Transition......................10
+ 3.2.8 Nested Convergence Events............................10
+ 3.3 Interfaces
+ 3.3.1 Local Interface......................................11
+ 3.3.2 Neighbor Interface...................................11
+ 3.3.3 Remote Interface.....................................11
+ 3.3.4 Preferred Egress Interface...........................12
+ 3.3.5 NextBest Egress Interface...........................12
+ 3.4 Benchmarking Method
+ 3.4.1 Packet Loss..........................................13
+ 3.4.2 Convergence Packet Loss..............................13
+ 3.4.3 RateDerived Convergence Method......................14
+ 3.4.4 LossDerived Convergence Method......................14
+ 3.4.5 Packet Sampling Interval.............................15
+ 3.5 Benchmarks
+ 3.5.1 Full Convergence Time................................17
+ 3.5.2 First Route Convergence Time.........................17
+ 3.5.3 RouteSpecific Convergence Time......................17
+ 3.5.4 Sustained Convergence Validation Time................18
+ 3.5.5 Reversion Convergence Time...........................19
4. IANA Considerations...........................................19
5. Security Considerations.......................................19
 6. Acknowledgements..............................................19
 7. References....................................................19
 8. Author's Address..............................................20
+ 6. Acknowledgements..............................................20
+ 7. References....................................................20
+ 8. Author's Address..............................................21
+ LinkState IGP Data Plane Route Convergence
+
+1. Introduction and Scope
1. Introduction
This draft describes the terminology for benchmarking Interior
Gateway Protocol (IGP) Route Convergence. The motivation and
applicability for this benchmarking is provided in [Po07a]. The
methodology to be used for this benchmarking is described in [Po07m].
 The methodology and terminology to be used for benchmarking Route
 Convergence can be applied to any linkstate IGP such as ISIS [Ca90]
 and OSPF [Mo98]. The data plane is measured to obtain blackbox
 (externally observable) convergence benchmarking metrics. The
 purpose of this document is to introduce new terms required to
+ The purpose of this document is to introduce new terms required to
complete execution of the IGP Route Convergence Methodology [Po07m].
These terms apply to IPv4 and IPv6 traffic and IGPs.
 LinkState IGP Data Plane Route Convergence
+ Convergence times are measured at the Tester on the data plane by
+ observing packet loss through the DUT. The methodology and
+ terminology to be used for benchmarking Route Convergence can be
+ applied to any linkstate IGP such as ISIS [Ca90] and OSPF [Mo98].
+ The data plane is measured to obtain blackbox (externally
+ observable) convergence benchmarking metrics. When there is no
+ packer loss observed in the data plane, the convergence time
+ SHALL be reported as zero.
An example of Route Convergence as observed and measured from the
data plane is shown in Figure 1. The graph in Figure 1 shows
Forwarding Rate versus Time. Time 0 on the Xaxis is on the far
right of the graph. The Offered Load to the ingress interface of
 the DUT SHOULD equal the measured maximum Throughput [Ba99][Ma98]
 of the DUT and the Forwarding Rate [Ma98] is measured at the egress
 interfaces of the DUT. The components of the graph and the metrics
 are defined in the Term Definitions section.
+ the DUT SHOULD equal the measured Throughput [Ba99][Ma98] of the DUT
+ and the Forwarding Rate [Ma98] and Convergence Packet Loss is
+ measured at the Preferred and NextBest Egress interfaces of the DUT
+ befire, during, and after a Convergence Event Trigger. These
+ components of the graph are defined in the Term Definitions section.
 Full Convergence,
 Convergence Convergence
 Recovery Event
 Instant Instant Time = 0sec
 Forwarding Rate = ^ ^ ^ Offered Load =
 Offered Load > \ Packet / <Max Throughput
+ Full Convergence> Convergence Convergence
+ Recovery Event Event Time=
+ Instant Instant Trigger 0sec
+ Forwarding Rate= ^ ^ ^ ^ Offered Load=
+ Offered Load > \ Packet / <Max Throughput
\ Loss /<Convergence
Convergence>\ / Event Transition
Recovery Transition \ /
\_____/<Maximum Packet Loss
^
First Route
Convergence Instant
Yaxis = Forwarding Rate
Xaxis = Time (increases right to left to match commercial test
equipment displays)
Figure 1. Convergence Graph
+ LinkState IGP Data Plane Route Convergence
2. Existing definitions

+2. Existing Definitions
This document uses existing terminology defined in other BMWG
work. Examples include, but are not limited to:
Latency [Ref.[Ba91], section 3.8]
Frame Loss Rate [Ref.[Ba91], section 3.6]
Throughput [Ref.[Ba91], section 3.17]
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 3.3.2]
Duplicate Packet [Ref.[Po06], section 3.3.3]
Packet Reordering [Ref.[Mo06], section 3.3]
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.
 LinkState IGP Data Plane Route Convergence

3. Term Definitions
 3.1 Convergence Event

 Definition:
 The occurrence of a planned or unplanned event in the network
 that results in a change in the egress interface of the Device
 Under Test (DUT) for routed packets.

 Discussion:
 Convergence Events include link loss, routing protocol session
 loss, router failure, configuration change, and better nexthop
 learned via a routing protocol.

 Measurement Units:
 N/A

 Issues:
 None

 See Also:
 Convergence Packet Loss
 Convergence Event Instant
 3.2 Route Convergence
+ 3.1 States
+ 3.1.1 Route Convergence
Definition:
The action to update all components of the router with the
most recent route change(s) including the Routing
Information Base (RIB) and Forwarding Information Base (FIB),
along with software and hardware tables, such that forwarding
is successful for one or more route entries.
Discussion:
Route Convergence MUST occur after a Convergence Event.
Route Convergence can be observed externally by the rerouting
of data traffic to the Nextbest Egress Interface. Also,
completion of Route Convergence may or may not be sustained
over time.
 Measurement Units:
 N/A
+ Measurement Units: N/A
 Issues:
 None
+ Issues: None
See Also:
Network Convergence
Full Convergence
Convergence Event
LinkState IGP Data Plane Route Convergence
 3.3 Full Convergence
+ 3.1.2 Full Convergence
Definition:
Route Convergence for an entire FIB in which complete recovery
 from the Convergence Event is indicated by the DUT Throughput
+ from the Convergence Event is indicated by the DUT throughput
equal to the offered load.
Discussion:
When benchmarking convergence, it is useful to measure
the time to converge an entire FIB. For example,
a Convergence Event can be produced for an OSPF table of
5000 routes so that the time to converge routes 1 through
5000 is measured. Completion of Full Convergence is externally
observable from the data plane when the Throughput of the data
plane traffic on the NextBest Egress Interface equals the
offered load.
 Full convergence MAY be measured using RateDerived Convergence
 Time (3.13) or calculated using LossDerived Convergence Time
 (3.14). When performing RouteSpecific Convergence (3.5)
 measurements, Full Convergence may be obtained by measuring the
 maximum Route Specific Convergence Time (3.15). Full
 Convergence may or may not be sustained over time. The
 Sustained Convergence Validation Time (3.16) MUST be applied.
+ Full Convergence MAY be measured using RateDerived Convergence
+ Method or calculated using LossDerived Convergence Method.
+ Full Convergence may or may not be sustained over time. The
+ Sustained Convergence Validation Time MUST be applied.
 Measurement Units:
 N/A
+ Measurement Units: N/A
 Issues:
 None
+ Issues: None
See Also:
Network Convergence
Route Convergence
Convergence Event
 3.4 Network Convergence
+ 3.1.3 Network Convergence
Definition:
The process of updating of all routing tables, including
distributed FIBs, in all routers throughout the network.
Discussion:
Network Convergence requires completion of all Route
Convergence operations for all routers in the network following
a Convergence Event. Completion of Network Convergence can be
observed by recovery of System Under Test (SUT) Throughput to
equal the offered load, with no Stale Forwarding, and no
Blenders [Ca01][Ci03].
 LinkState IGP Data Plane Route Convergence

 Measurement Units:
 N/A
+ Measurement Units: N/A
 Issues:
 None
+ Issues: None
+ LinkState IGP Data Plane Route Convergence
See Also:
Route Convergence
Stale Forwarding
 3.5 RouteSpecific Convergence

+ 3.1.4 RouteSpecific Convergence
Definition:
Route Convergence for one or more specific route entries in
the FIB in which recovery from the Convergence Event is
 indicated by dataplane traffic for a flow [Po06] matching that
 route entry(ies) being routed to the NextBest Egress Interface.
+ indicated when dataplane traffic for the flow [Po06] matching
+ that route entry(ies) is routed to the NextBest Egress
+ Interface.
Discussion:
When benchmarking convergence, it is sometimes useful to
measure the time to converge a single flow [Po06] or group of
flows to benchmark convergence time for one or a few route
entries in the FIB instead of the entire FIB. RouteSpecific
Convergence of a flow is externally observable from the data
plane when the data plane traffic for that flow is routed to
the NextBest Egress Interface.
 Measurement Units:
 N/A
+ Measurement Units: N/A
 Issues:
 None
+ Issues: None
See Also:
Full Convergence
Route Convergence
Convergence Event
+
+ 3.1.5 Stale Forwarding
+ Definition:
+ Forwarding of traffic to route entries that no longer exist
+ or to route entries with nexthops that are no longer preferred.
+
+ Discussion:
+ Stale Forwarding can be caused by a Convergence Event and can
+ manifest as a "blackhole" or microloop that produces packet
+ loss. Stale Forwarding can exist until Network Convergence is
+ completed. Stale Forwarding cannot be observed with a single
+ DUT.
+
+ Measurement Units: N/A
+
+ Issues: None
+
+ See Also:
+ Network Convergence
LinkState IGP Data Plane Route Convergence
 3.6 Packet Loss
+ 3.2 Events
+
+ 3.2.1 Convergence Event
Definition:
 The number of packets that should have been forwarded
 by a DUT under a constant offered load that were
 not forwarded due to lack of resources.
+ The occurrence of a planned or unplanned event in the network
+ that results in a change in the egress interface of the Device
+ Under Test (DUT) for routed packets.
Discussion:
 Packet Loss is a modified version of the term "Frame Loss Rate"
 as defined in [Ba91]. The term "Frame Loss" is intended for
 Ethernet Frames while "Packet Loss" is intended for IP packets.
 Packet Loss can be measured as a reduction in forwarded traffic
 from the Throughput [Ba91] of the DUT.
+ Convergence Events include link loss, routing protocol session
+ loss, router failure, configuration change, and better nexthop
+ learned via a routing protocol.
 Measurement units:
 Number of offered packets that are not forwarded.
+ Measurement Units:
+ N/A
 Issues: None
+ Issues:
+ None
See Also:
Convergence Packet Loss
+ Convergence Event Instant
 3.7 Convergence Packet Loss
+ 3.2.2 Convergence Event Trigger
Definition:
 The number of packets lost due to a Convergence Event
 until Full Convergence completes.
+ An action taken by the Tester to produce a Convergence Event.
Discussion:
 Convergence Packet Loss includes packets that were lost and
 packets that were delayed due to buffering. The Convergence
 Packet Loss observed in a Packet Sampling Interval may or may
 not be equal to the number of packets in the offered load
 during the interval following a Convergence Event (see Figure
 1).
+ The Convergence Event Trigger is introduced by the Tester and
+ may be indicated by link loss, routing protocol session loss,
+ router failure, configuration change, or a better nexthop
+ learned via a routing protocol introduced by the Tester.
Measurement Units:
 number of packets
+ N/A
 Issues: None
+ Issues:
+ None
See Also:
 Packet Loss
 Route Convergence
Convergence Event
 Packet Sampling Interval
+ Convergence Packet Loss
+ Convergence Recovery Instant
LinkState IGP Data Plane Route Convergence
 3.8 Convergence Event Instant
+ 3.2.3 Convergence Event Instant
Definition:
The time instant that a Convergence Event becomes observable in
the data plane.
Discussion:
Convergence Event Instant is observable from the data
plane as the precise time that the device under test begins
 to exhibit packet loss.
+ to exhibit packet loss. The Convergence Event Instant is
+ produced by the Convergence Event Trigger. The Convergence
+ Event Instant always occurs concurrent or subsequent to the
+ Tester introducing the Convergence Event Trigger.
Measurement Units:
hh:mm:ss:nnn:uuu,
where 'nnn' is milliseconds and 'uuu' is microseconds.
 Issues:
 None
+ Issues: None
See Also:
Convergence Event
Convergence Packet Loss
Convergence Recovery Instant
 3.9 Convergence Recovery Instant
+ 3.2.4 Convergence Recovery Instant
Definition:
The time instant that Full Convergence completion is
 measured and then maintained for an interval of duration
 equal to the Sustained Convergence Validation Time.
+ observed.
Discussion:
Convergence Recovery Instant is measurable from the data
 plane as the precise time that the device under test
 completes Full Convergence.
+ plane as the precise time that the device under test completes
+ Full Convergence. The Convergence Recovery Instant MUST be
+ maintained for an interval of duration equal to the Sustained
+ Convergence Validation Time.
Measurement Units:
hh:mm:ss:nnn:uuu,
where 'nnn' is milliseconds and 'uuu' is microseconds.
Issues:
None
See Also:
Sustained Convergence Validation Time
Convergence Packet Loss
Convergence Event Instant
LinkState IGP Data Plane Route Convergence
 3.10 First Route Convergence Instant
+ 3.2.5 First Route Convergence Instant
Definition:
The time instant a first route entry has converged
following a Convergence Event, as observed by receipt of
the first packet from the NextBest Egress Interface.
Discussion:
The First Route Convergence Instant is an indication that the
process to achieve Full Convergence has begun. Any route may
be the first to converge for First Route Convergence Instant.
Measurement on the dataplane enables the First Route
Convergence Instant to be observed without any whitebox
information from the DUT.
 Measurement Units: N/A
+ Measurement Units:
+ hh:mm:ss:nnn:uuu,
+ where 'nnn' is milliseconds and 'uuu' is microseconds.
Issues:
None
See Also:
Route Convergence
Full Convergence
Stale Forwarding
 3.11 Convergence Event Transition
+ 3.2.6 Convergence Event Transition
Definition:
A time interval observed following a Convergence Event in which
Throughput gradually reduces to a minimum value.
Discussion:
The Convergence Event Transition is best observed for Full
Convergence. The egress packet rate observed during a
Convergence Event Transition may not decrease linearly and may
not decrease to zero. Both the offered load and the Packet
Sampling Interval influence the observations of the Convergence
 Event Transition. For example, even if the Convergence Event
 were to cause the Throughput [Ba91] to drop to zero there would
 be some number of packets observed, unless the Packet Sampling
 Interval is exactly aligned with the Convergence Event. This
 is further discussed with the term "Packet Sampling Interval".
+ Event Transition. For example, it is possible that if the
+ Convergence Event were to cause the Throughput [Ba91] to drop
+ to zero then this may not be observed if the Packet Sampling
+ Interval is set too high. This is further discussed with the
+ term "Packet Sampling Interval".
Measurement Units:
seconds
 Issues:
 None
+ Issues: None
+ LinkState IGP Data Plane Route Convergence
See Also:
Convergence Event
Full Convergence
Packet Sampling Interval
 LinkState IGP Data Plane Route Convergence
 3.12 Convergence Recovery Transition
+ 3.2.7 Convergence Recovery Transition
Definition:
The characteristic of the DUT in which Throughput gradually
increases to equal the offered load.
Discussion:
The Convergence Recovery Transition is best observed for
Full Convergence. The egress packet rate observed during
a Convergence Recovery Transition may not increase linearly.
Both the offered load and the Packet Sampling Interval
@@ 458,455 +463,496 @@
Measurement Units:
seconds
Issues: None
See Also:
Full Convergence
Packet Sampling Interval
 3.13 RateDerived Convergence Time
+ 3.2.8 Nested Convergence Events
Definition:
 The amount of time for Convergence Packet Loss to persist upon
 occurrence of a Convergence Event until Full Convergence has
 completed.

 RateDerived Convergence Time can be measured as the time
 difference from the Convergence Event Instant to the
 Convergence Recovery Instant, as shown with Equation 1.

 (Equation 1)
 RateDerived Convergence Time =
 Convergence Recovery Instant  Convergence Event Instant.
+ The occurrence of a Convergence Event while the route
+ table is converging from a prior Convergence Event.
Discussion:
 RateDerived Convergence Time SHOULD be measured at the maximum
 Throughput of the DUT. At least one packet per route in the FIB
 for all routes in the FIB MUST be offered to the DUT within the
 Packet Sampling Interval.
+ The Convergence Events for a Nested Convergence Event
+ MUST occur with different neighbors. A common
+ observation from a Nested Convergence Event will be
+ the withdrawal of routes from one neighbor while the
+ routes of another neighbor are being installed.
 Failure to achieve Full Convergence results in a RateDerived
 Convergence Time benchmark of infinity. It is RECOMMENDED that
 the RateDerived Convergence Time be measured when benchmarking
 Full Convergence.
+ Measurement Units: N/A
+ Issues: None
+
+ See Also:
+ Convergence Event
LinkState IGP Data Plane Route Convergence
 Measurement Units:
 seconds
+ 3.3 Interfaces
+
+ 3.3.1 Local Interface
+
+ Definition:
+ An interface on the DUT.
+
+ Discussion:
+ A failure of the Local Interface indicates that the failure
+ occurred directly on the DUT.
+
+ Measurement Units: N/A
Issues: None
See Also:
 Convergence Packet Loss
 Convergence Recovery Instant
 Convergence Event Instant
 Full Convergence
+ Neighbor Interface
+ Remote Interface
 3.14 LossDerived Convergence Time
+ 3.3.2 Neighbor Interface
Definition:
 The amount of time it takes for Full Convergence to be
 completed as calculated from the amount of Convergence
 Packet Loss. LossDerived Convergence Time can be
 calculated from Convergence Packet Loss as shown with
 Equation 2.
+ The interface on the neighbor router or tester that is
+ directly linked to the DUT's Local Interface.
 Equation 2 
 LossDerived Convergence Time =
 Convergence Packets Loss / Offered Load
 where units are packets / packets/second = seconds
+ Discussion:
+ A failure of a Neighbor Interface indicates that a
+ failure occurred on a neighbor router's interface that
+ directly links the neighbor router to the DUT.
+
+ Measurement Units: N/A
+
+ Issues: None
+
+ See Also:
+ Local Interface
+ Remote Interface
+
+ 3.3.3 Remote Interface
+
+ Definition:
+ An interface on a neighboring router that is not directly
+ connected to any interface on the DUT.
Discussion:
 Optimally, the Convergence Event Transition and Convergence
 Recovery Transition are instantaneous so that the
 RateDerived Convergence Time = LossDerived Convergence Time.
 However, router implementations are less than ideal.
 LossDerived Convergence Time gives a better than
 actual result when converging many routes simultaneously
 because it ignores the Convergence Recovery Transition.
 RateDerived Convergence Time takes the Convergence Recovery
 Transition into account. Equation 2 calculates the average
 convergence time over all routes to which packets have been
 sent. Since this average convergence time is in general
 smaller than the maximum convergence time over all routes,
 LossDerived Convergence Time is not the preferred metric to
 indicate Full Convergence completion. For this reason the
 RECOMMENDED benchmark metric for Full Convergence is the
 RateDerived Convergence Time.
+ A failure of a Remote Interface indicates that the failure
+ occurred on a neighbor router's interface that is not
+ directly connected to the DUT.
LinkState IGP Data Plane Route Convergence
 Guidelines for reporting LossDerived Convergence Time are
 provided in [Po07m].

Measurement Units:
 seconds
+ N/A
Issues:
None
See Also:
 Convergence Event
 Convergence Packet Loss
 RateDerived Convergence Time
 RouteSpecific Convergence
 Convergence Event Transition
 Convergence Recovery Transition
+ Local Interface
+ Neighbor Interface
 3.15 RouteSpecific Convergence Time
+ 3.3.4 Preferred Egress Interface
Definition:
 The amount of time it takes for RouteSpecific Convergence to
 be completed as calculated from the amount of Convergence
 Packet Loss per flow.
+ The outbound interface from the DUT for traffic routed to the
+ preferred nexthop.
 RouteSpecific Convergence Time can be calculated from
 Convergence Packet Loss as shown with Equation 3.
+ Discussion:
+ The Preferred Egress Interface is the egress interface prior
+ to a Convergence Event.
 Equation 3 
 RouteSpecific Convergence Time =
 Convergence Packets Loss / Offered Load
 where units are packets / packets/second = seconds
+ Measurement Units:
+ N/A
+
+ Issues:
+ None
+
+ See Also:
+ NextBest Egress Interface
+
+ 3.3.5 NextBest Egress Interface
+
+ Definition:
+ The outbound interface from the DUT for traffic routed to the
+ secondbest nexthop. It is the same media type and link speed
+ as the Preferred Egress Interface
Discussion:
+ The NextBest Egress Interface becomes the egress interface
+ after a Convergence Event.
 It is possible to provide an offered load that has flows
 matching every route entry in the FIB and benchmarking
 RouteSpecific Convergence Time for all route entries. The
 number of flows that can be measured is dependent upon the flow
 measurement capabilities of the Tester. When benchmarking
 RouteSpecific Convergence, Convergence Packet Loss is measured
 for specific flow(s) and Equation 3 is applied for each flow.
 Each flow has a single destination address matching a different
 route entry. The fastest measurable convergence time is equal
 to the time between two consecutive packets of a flow offered
 by the Tester.
+ Measurement Units:
+ N/A
 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
+ Issues: None
+
+ See Also:
+ Preferred Egress Interface
LinkState IGP Data Plane Route Convergence
+ 3.4 Benchmarking Methods
 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 [Po07m].
+ 3.4.1 Packet Loss
 The RouteSpecific Convergence Time MAY be used to benchmark
 Full Convergence when used in combination with many flows
 matching every FIB entry. In this case
 Full Convergence = max(RouteSpecific Convergence Time).
+ Definition:
+ The number of packets that should have been forwarded
+ by a DUT under a constant offered load that were
+ not forwarded due to lack of resources.
 Measurement Units:
 seconds
+ Discussion:
+ Packet Loss is a modified version of the term "Frame Loss Rate"
+ as defined in [Ba91]. The term "Frame Loss" is intended for
+ Ethernet Frames while "Packet Loss" is intended for IP packets.
+ Packet Loss can be measured as a reduction in forwarded traffic
+ from the Throughput [Ba91] of the DUT.
 Issues:
 None
+ Measurement units:
+ Number of offered packets that are not forwarded.
+
+ Issues: None
See Also:
 Convergence Event
Convergence Packet Loss
 RouteSpecific Convergence
 3.16 Sustained Convergence Validation Time
+ 3.4.2 Convergence Packet Loss
Definition:
 The amount of time for which the completion of Full
 Convergence is maintained without additional packet loss.
+ The number of packets lost due to a Convergence Event
+ until Full Convergence completes.
Discussion:
 The purpose of the Sustained Convergence Validation Time is to
 produce Convergence benchmarks protected against fluctuation
 in Throughput after the completion of Full Convergence is
 observed. The RECOMMENDED Sustained Convergence Validation
 Time to be used is 5 seconds. The BMWG selected 5 seconds
 based upon RFC 2544 [Ba99] which recommends waiting 2 seconds
 for residual frames to arrive and 5 seconds for DUT
 restabilization.
+ Convergence Packet Loss includes packets that were lost and
+ packets that were delayed due to buffering. The Convergence
+ Packet Loss observed in a Packet Sampling Interval may or may
+ not be equal to the number of packets in the offered load
+ during the interval following a Convergence Event (see Figure
+ 1).
Measurement Units:
 seconds
+ number of packets
Issues: None
See Also:
 Full Convergence
 Convergence Recovery Instant
+ Packet Loss
+ Route Convergence
+ Convergence Event
+ Packet Sampling Interval
LinkState IGP Data Plane Route Convergence
 3.17 First Route Convergence Time

+ 3.4.3 RateDerived Convergence Method
Definition:
 The amount of time for Convergence Packet Loss until the
 convergence of a first route entry on the NextBest Egress
 Interface, as indicated by the First Route Convergence
 Instant.

 Discussion:
 The First Route Convergence Time benchmarking metric can be
 measured when benchmarking either Full Convergence or
 RouteSpecific Convergence. When benchmarking Full Convergence,
 First Route Convergence Time can be measured as the time
 difference from the Convergence Event Instant and the First
 Route Convergence Instant, as shown with Equation 4a.
+ The method to calculate convergence time benchmarks from the
+ amount of time that Convergence Packet Loss persists upon
+ occurrence of a Convergence Event.
 (Equation 4a)
 First Route Convergence Time =
 First Route Convergence Instant  Convergence Event Instant
+ RateDerived Convergence Method can be calculated as the time
+ difference from the Convergence Event Instant to the
+ Convergence Recovery Instant, as shown with Equation 1.
 When benchmarking RouteSpecific Convergence, First Route
 Convergence Time can be measured as the minimum RouteSpecific
 Convergence Time, as shown with Equation 4b.
+ (Equation 1)
+ RateDerived Convergence Method =
+ Convergence Recovery Instant  Convergence Event Instant.
 (Equation 4b)
 First Route Convergence Time =
 min(RouteSpecific Convergence Time)
+ Discussion:
+ It is RECOMMENDED that the RateDerived Convergence Method be
+ measured when benchmarking convergence times. The RateDerived
+ Convergence Method SHOULD be measured with an Offered Load at
+ the Throughput of the DUT. At least one packet per route
+ in the FIB for all routes in the FIB MUST be offered to the DUT
+ within the Packet Sampling Interval.
 First Route Convergence Time should be measured at the maximum
 Throughput of the DUT. At least one packet per route in the FIB
 for all routes in the FIB MUST be offered to the DUT within the
 Packet Sampling Interval. Failure to achieve the First Route
 Convergence Instant results in a First Route Convergence Time
 benchmark of infinity.
+ It is possible to measure no packet loss, which results in a
+ RateDerived Convergence Time benchmark of zero. Failure to
+ achieve Full Convergence results in a RateDerived Convergence
+ Time benchmark of infinity.
Measurement Units:
seconds
Issues: None
See Also:
Convergence Packet Loss
 First Route Convergence Instant
 LinkState IGP Data Plane Route Convergence
+ Convergence Recovery Instant
+ Convergence Event Instant
+ Full Convergence
 3.18 Reversion Convergence Time
+ 3.4.4 LossDerived Convergence Method
Definition:
 The amount of time for the DUT to complete Full Convergence
 to the Preferred Egress Interface, instead of the NextBest
 Egress Interface, upon recovery from a Convergence Event.
+ The method to calculate convergence time benchmarks from the
+ amount of Convergence Packet Loss. LossDerived Convergence
+ Method can be calculated from Convergence Packet Loss as shown
+ with Equation 2.
+
+ Equation 2 
+ LossDerived Convergence Method =
+ Convergence Packets Loss / Offered Load
+ where units are packets / packets/second = seconds
+ LinkState IGP Data Plane Route Convergence
Discussion:
 Reversion Convergence Time is the amount of time for Full
 Convergence to the original egress interface. This is
 achieved by recovering from the Convergence Event, such as
 restoring the failed link. Reversion Convergence Time is
 measured using the RateDerived Convergence Time calculation
 technique, as provided in Equation 1. It is possible to have
 the Reversion Convergence Time differ from the RateDerived
 Convergence Time.
+ Ideally, the Convergence Event Transition and Convergence
+ Recovery Transition are instantaneous so that the RateDerived
+ Convergence Method = LossDerived Convergence Method. However,
+ router implementations are less than ideal. LossDerived
+ Convergence Method gives a better than actual result when
+ converging many routes simultaneously because it ignores the
+ transitions. The RateDerived Convergence Method takes the
+ transitions into account.
 Measurement Units: seconds
+ Equation 2 calculates the average convergence time over all
+ routes to which packets have been sent. The average convergence
+ time is often lower than the maximum convergence time
+ over all routes, so it can produce a result that is faster than
+ the actual convergence time.. Therefore, LossDerived
+ Convergence Method is not the preferred method to measure
+ convergence benchmarks. For these reasons the RECOMMENDED
+ method to obtain a benchmark metric for convergence time is the
+ RateDerived Convergence Method.
+
+ Measurement Units:
+ seconds
Issues: None
See Also:
 Preferred Egress Interface
 Convergence Event
 RateDerived Convergence Time
+ Convergence Packet Loss
+ RateDerived Convergence Method
+ RouteSpecific Convergence
+ Convergence Event Transition
+ Convergence Recovery Transition
 3.19 Packet Sampling Interval
+ 3.4.5 Packet Sampling Interval
Definition:
The interval at which the tester (test equipment) polls to make
measurements for arriving packet flows.
Discussion:
At least one packet per route in the FIB for all routes in the
FIB MUST be offered to the DUT within the Packet Sampling
Interval. Metrics measured at the Packet Sampling Interval
MUST include Forwarding Rate and Convergence Packet Loss.
Packet Sampling Interval can influence the Convergence Graph.
This is particularly true when implementations complete Full
 Convergence in less than the Packet Sampling Interval. The
+ Convergence in less time than the Packet Sampling Interval. The
Convergence Event Transition and Convergence Recovery Transition
+ LinkState IGP Data Plane Route Convergence
+
can become exaggerated when the Packet Sampling Interval is too
 long. This will produce a larger than actual RateDerived
 Convergence Time. The recommended value for configuration of
+ long. In this condition, the RateDerived Convergence Method
+ may produce a larger than actual convergence time. In such
+ cases the LossDerived Convergence Method may produce a more
+ accurate result. The recommended value for configuration of
the Packet Sampling Interval is provided in [Po07m].
Measurement Units: seconds
Issues: None
See Also:
Convergence Packet Loss
Convergence Event Transition
Convergence Recovery Transition
 LinkState IGP Data Plane Route Convergence
 3.20 Local Interface
+3.5 Benchmarks
+
+ 3.5.1 Full Convergence Time
Definition:
 An interface on the DUT.
+ The amount of time it takes for Full Convergence to occur.
Discussion:
 A failure of the Local Interface indicates that the failure
 occurred directly on the DUT.
+ Full Convergence Time can be determined using the RateDerived
+ Convergence Method or LossDerived Convergence Method. The
+ RateDerived Convergence Method is RECOMMENDED. When
+ measuring RouteSpecific Convergence Time, there may be
+ conditions in which the maximum Route Specific Convergence Time
+ can be reported as the Full Convergence Time. Full Convergence
+ may or may not be sustained over time. The Sustained
+ Convergence Validation Time MUST be applied.
Measurement Units:
 N/A
+ seconds
 Issues:
 None
+ Issues: None
See Also:
 Neighbor Interface
 Remote Interface
+ Full Convergence
+ RateDerived Convergence Method
+ LossDerived Convergence Method
 3.21 Neighbor Interface
+ 3.5.2 First Route Convergence Time
Definition:
 The interface on the neighbor router or tester that is
 directly linked to the DUT's Local Interface.

 Discussion:
 A failure of a Neighbor Interface indicates that a
 failure occurred on a neighbor router's interface that
 directly links the neighbor router to the DUT.

 Measurement Units:
 N/A

 Issues:
 None
+ The amount of time for Convergence Packet Loss until the
+ convergence of a first route entry on the NextBest Egress
+ Interface, as indicated by the First Route Convergence
+ Instant.
 See Also:
 Local Interface
 Remote Interface
LinkState IGP Data Plane Route Convergence
 3.22 Remote Interface
+ Discussion:
+ The First Route Convergence Time benchmarking metric can be
+ measured when benchmarking either Full Convergence or
+ RouteSpecific Convergence. When benchmarking Full Convergence,
+ First Route Convergence Time can be measured as the time
+ difference from the Convergence Event Instant and the First
+ Route Convergence Instant, as shown with Equation 4a.
 Definition:
 An interface on a neighboring router that is not directly
 connected to any interface on the DUT.
+ (Equation 4a)
+ First Route Convergence Time =
+ First Route Convergence Instant  Convergence Event Instant
 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 DUT.
+ First Route Convergence Time should be measured at the maximum
+ Throughput of the DUT. At least one packet per route in the FIB
+ for all routes in the FIB MUST be offered to the DUT within the
+ Packet Sampling Interval. Failure to achieve the First Route
+ Convergence Instant results in a First Route Convergence Time
+ benchmark of infinity.
Measurement Units:
 N/A
+ seconds
 Issues:
 None
+ Issues: None
See Also:
 Local Interface
 Neighbor Interface
+ Convergence Packet Loss
+ First Route Convergence Instant
 3.23 Preferred Egress Interface
+ 3.5.3 RouteSpecific Convergence Time
Definition:
 The outbound interface from the DUT for traffic routed to the
 preferred nexthop.
+ The amount of time it takes for RouteSpecific Convergence to
+ be completed as calculated from the amount of Convergence
+ Packet Loss for the flow associated to a specific route.
+
+ RouteSpecific Convergence Time can be calculated from
+ Convergence Packet Loss as shown with Equation 3.
+
+ (Equation 3) RouteSpecific Convergence Time =
+ Convergence Packets Loss / Offered Load
+ where units are packets / packets/second = seconds
+ LinkState IGP Data Plane Route Convergence
Discussion:
 The Preferred Egress Interface is the egress interface prior
 to a Convergence Event.
+ It is possible to provide an offered load that has flows
+ matching every route entry in the FIB and benchmarking
+ RouteSpecific Convergence Time for all route entries. The
+ number of flows that can be measured is dependent upon the flow
+ measurement capabilities of the Tester. When benchmarking
+ RouteSpecific Convergence, Convergence Packet Loss is measured
+ for specific flow(s) and Equation 3 is applied for each flow.
+ Each flow has a single destination address matching a different
+ route entry. The fastest measurable convergence time is equal
+ to the time between two consecutive packets of a flow offered
+ by the Tester. In practice, the fastest measurable
+ convergence time is the Packet Sampling Interval of the Tester.
+
+ 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 [Po07m].
Measurement Units:
 N/A
+ seconds
Issues:
None
See Also:
 NextBest Egress Interface

 3.24 NextBest Egress Interface
+ Convergence Event
+ Convergence Packet Loss
+ RouteSpecific Convergence
+ 3.5.4 Sustained Convergence Validation Time
Definition:
 The outbound interface from the DUT for traffic routed to the
 secondbest nexthop. It is the same media type and link speed
 as the Preferred Egress Interface
+ The amount of time for which the completion of Full
+ Convergence is maintained without additional packet loss.
Discussion:
 The NextBest Egress Interface becomes the egress interface
 after a Convergence Event.
+ The purpose of the Sustained Convergence Validation Time is to
+ produce Convergence benchmarks protected against fluctuation
+ in Throughput after the completion of Full Convergence is
+ observed. The RECOMMENDED Sustained Convergence Validation
+ Time to be used is 5 seconds. The BMWG selected 5 seconds
+ based upon RFC 2544 [Ba99] which recommends waiting 2 seconds
+ for residual frames to arrive and 5 seconds for DUT
+ restabilization.
LinkState IGP Data Plane Route Convergence
Measurement Units:
 N/A

 Issues: None

 See Also:
 Preferred Egress Interface

 3.25 Stale Forwarding

 Definition:
 Forwarding of traffic to route entries that no longer exist
 or to route entries with nexthops that are no longer preferred.

 Discussion:
 Stale Forwarding can be caused by a Convergence Event and can
 manifest as a "blackhole" or microloop that produces packet
 loss. Stale Forwarding can exist until Network Convergence is
 completed. Stale Forwarding cannot be observed with a single
 DUT.

 Measurement Units:
 N/A
+ seconds
Issues: None
See Also:
 Network Convergence
+ Full Convergence
+ Convergence Recovery Instant
 3.26 Nested Convergence Events
+ 3.5.5 Reversion Convergence Time
Definition:
 The occurrence of a Convergence Event while the route
 table is converging from a prior Convergence Event.
+ The amount of time for the DUT to complete Full Convergence
+ to the Preferred Egress Interface, instead of the NextBest
+ Egress Interface, upon recovery from a Convergence Event.
Discussion:
 The Convergence Events for a Nested Convergence Event
 MUST occur with different neighbors. A common
 observation from a Nested Convergence Event will be
 the withdrawal of routes from one neighbor while the
 routes of another neighbor are being installed.
+ Reversion Convergence Time is the amount of time for Full
+ Convergence to the original egress interface. This is
+ achieved by recovering from the Convergence Event, such as
+ restoring the failed link. Reversion Convergence Time
+ can be measured using the RateDerived Convergence Method
+ or LossDerived Convergence Method. The RateDerived
+ Convergence Method is RECOMMENDED. It is possible to have
+ the Reversion Convergence Time differ from the Full
+ Convergence Time.
 Measurement Units:
 N/A
+ Measurement Units: seconds
Issues: None
See Also:
+ Preferred Egress Interface
Convergence Event
 LinkState IGP Data Plane Route Convergence
+ RateDerived Convergence Method
4. IANA Considerations
This document requires no IANA considerations.
5. Security Considerations
Documents of this type do not directly affect the security of
 Internet or corporate networks as long as benchmarking
 is not performed on devices or systems connected to production
 networks.
+ Internet or corporate networks as long as benchmarking is not
+ performed on devices or systems connected to production networks.
+ Security threats and how to counter these in SIP and the media
+ layer is discussed in RFC3261, RFC3550, and RFC3711 and various
+ other drafts. This document attempts to formalize a set of
+ common terminology for benchmarking IGP convergence performance
+ in a lab environment.
+
+ LinkState IGP Data Plane Route Convergence
6. Acknowledgements
Thanks to Sue Hares, Al Morton, Kevin Dubray, Ron Bonica, David Ward,
Kris Michielsen and the BMWG for their contributions to this work.
7. References
7.1 Normative References

[Ba91] Bradner, S. "Benchmarking Terminology for Network
Interconnection Devices", RFC1242, July 1991.
[Ba99] Bradner, S. and McQuaid, J., "Benchmarking
Methodology for Network Interconnect Devices",
RFC 2544, March 1999.
[Br97] Bradner, S., "Key words for use in RFCs to Indicate
[Ca90] Callon, R., "Use of OSI ISIS for Routing in TCP/IP and Dual
Environments", RFC 1195, December 1990.
@@ 918,92 +964,45 @@
[Mo06] Morton, A., et al, "Packet Reordering Metrics", RFC 4737,
November 2006.
[Po06] Poretsky, S., et al., "Terminology for Benchmarking
Networklayer Traffic Control Mechanisms", RFC 4689,
November 2006.
[Po07a] Poretsky, S., "Benchmarking Applicability for LinkState
IGP Data Plane Route Convergence",
 draftietfbmwgigpdataplaneconvapp16, work in progress,
 October 2008.
+ draftietfbmwgigpdataplaneconvapp17, work in progress,
+ March 2009.
[Po07m] Poretsky, S. and Imhoff, B., "Benchmarking Methodology for
LinkState IGP Data Plane Route Convergence",
 draftietfbmwgigpdataplaneconvmeth16, work in progress,
 October 2008.

 LinkState IGP Data Plane Route Convergence
+ draftietfbmwgigpdataplaneconvmeth17, work in progress,
+ March 2009.
7.2 Informative References

[Ca01] S. Casner, C. Alaettinoglu, and C. Kuan, "A FineGrained View
of High Performance Networking", NANOG 22, June 2001.
[Ci03] L. Ciavattone, A. Morton, and G. Ramachandran, "Standardized
Active Measurements on a Tier 1 IP Backbone", IEEE
Communications Magazine, pp9097, May 2003.
+ LinkState IGP Data Plane Route Convergence
+
8. Author's Address
Scott Poretsky
Allot Communications
67 South Bedford Street, Suite 400
Burlington, MA 01803
USA
Phone: + 1 508 309 2179
Email: sporetsky@allot.com
Brent Imhoff
Juniper Networks
1194 North Mathilda Ave
Sunnyvale, CA 94089
USA
Phone: + 1 314 378 2571
EMail: bimhoff@planetspork.com

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