Network Working Group S. Poretsky
Internet-Draft Allot Communications
Intended status: Informational B. Imhoff
Expires: May 12, 2011 Juniper Networks
K. Michielsen
Cisco Systems
November 8, 2010
Benchmarking Methodology for Link-State IGP Data Plane Route Convergence
draft-ietf-bmwg-igp-dataplane-conv-meth-22
Abstract
This document describes the methodology for benchmarking Link-State
Interior Gateway Protocol (IGP) Route Convergence. The methodology
is to be used for benchmarking IGP convergence time through
externally observable (black box) data plane measurements. The
methodology can be applied to any link-state IGP, such as ISIS and
OSPF.
Status of this Memo
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Table of Contents
1. Introduction and Scope . . . . . . . . . . . . . . . . . . . . 5
2. Existing Definitions . . . . . . . . . . . . . . . . . . . . . 5
3. Test Topologies . . . . . . . . . . . . . . . . . . . . . . . 5
3.1. Test topology for local changes . . . . . . . . . . . . . 6
3.2. Test topology for remote changes . . . . . . . . . . . . . 7
3.3. Test topology for local ECMP changes . . . . . . . . . . . 8
3.4. Test topology for remote ECMP changes . . . . . . . . . . 9
3.5. Test topology for Parallel Link changes . . . . . . . . . 10
4. Convergence Time and Loss of Connectivity Period . . . . . . . 11
4.1. Convergence Events without instant traffic loss . . . . . 12
4.2. Loss of Connectivity . . . . . . . . . . . . . . . . . . . 14
5. Test Considerations . . . . . . . . . . . . . . . . . . . . . 15
5.1. IGP Selection . . . . . . . . . . . . . . . . . . . . . . 15
5.2. Routing Protocol Configuration . . . . . . . . . . . . . . 15
5.3. IGP Topology . . . . . . . . . . . . . . . . . . . . . . . 15
5.4. Timers . . . . . . . . . . . . . . . . . . . . . . . . . . 16
5.5. Interface Types . . . . . . . . . . . . . . . . . . . . . 16
5.6. Offered Load . . . . . . . . . . . . . . . . . . . . . . . 16
5.7. Measurement Accuracy . . . . . . . . . . . . . . . . . . . 17
5.8. Measurement Statistics . . . . . . . . . . . . . . . . . . 17
5.9. Tester Capabilities . . . . . . . . . . . . . . . . . . . 17
6. Selection of Convergence Time Benchmark Metrics and Methods . 18
6.1. Loss-Derived Method . . . . . . . . . . . . . . . . . . . 18
6.1.1. Tester capabilities . . . . . . . . . . . . . . . . . 18
6.1.2. Benchmark Metrics . . . . . . . . . . . . . . . . . . 19
6.1.3. Measurement Accuracy . . . . . . . . . . . . . . . . . 19
6.2. Rate-Derived Method . . . . . . . . . . . . . . . . . . . 19
6.2.1. Tester Capabilities . . . . . . . . . . . . . . . . . 19
6.2.2. Benchmark Metrics . . . . . . . . . . . . . . . . . . 20
6.2.3. Measurement Accuracy . . . . . . . . . . . . . . . . . 20
6.3. Route-Specific Loss-Derived Method . . . . . . . . . . . . 21
6.3.1. Tester Capabilities . . . . . . . . . . . . . . . . . 21
6.3.2. Benchmark Metrics . . . . . . . . . . . . . . . . . . 21
6.3.3. Measurement Accuracy . . . . . . . . . . . . . . . . . 22
7. Reporting Format . . . . . . . . . . . . . . . . . . . . . . . 22
8. Test Cases . . . . . . . . . . . . . . . . . . . . . . . . . . 23
8.1. Interface failures . . . . . . . . . . . . . . . . . . . . 24
8.1.1. Convergence Due to Local Interface Failure . . . . . . 24
8.1.2. Convergence Due to Remote Interface Failure . . . . . 25
8.1.3. Convergence Due to ECMP Member Local Interface
Failure . . . . . . . . . . . . . . . . . . . . . . . 27
8.1.4. Convergence Due to ECMP Member Remote Interface
Failure . . . . . . . . . . . . . . . . . . . . . . . 28
8.1.5. Convergence Due to Parallel Link Interface Failure . . 29
8.2. Other failures . . . . . . . . . . . . . . . . . . . . . . 30
8.2.1. Convergence Due to Layer 2 Session Loss . . . . . . . 30
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8.2.2. Convergence Due to Loss of IGP Adjacency . . . . . . . 31
8.2.3. Convergence Due to Route Withdrawal . . . . . . . . . 33
8.3. Administrative changes . . . . . . . . . . . . . . . . . . 34
8.3.1. Convergence Due to Local Adminstrative Shutdown . . . 34
8.3.2. Convergence Due to Cost Change . . . . . . . . . . . . 36
9. Security Considerations . . . . . . . . . . . . . . . . . . . 37
10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 38
11. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 38
12. Normative References . . . . . . . . . . . . . . . . . . . . . 38
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 39
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1. Introduction and Scope
This document describes the methodology for benchmarking Link-State
Interior Gateway Protocol (IGP) convergence. The motivation and
applicability for this benchmarking is described in [Po09a]. The
terminology to be used for this benchmarking is described in [Po10t].
IGP convergence time is measured on the data plane at the Tester by
observing packet loss through the DUT. All factors contributing to
convergence time are accounted for by measuring on the data plane, as
discussed in [Po09a]. The test cases in this document are black-box
tests that emulate the network events that cause convergence, as
described in [Po09a].
The methodology described in this document can be applied to IPv4 and
IPv6 traffic and link-state IGPs such as ISIS [Ca90][Ho08], OSPF
[Mo98][Co08], and others.
2. Existing Definitions
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.
This document uses much of the terminology defined in [Po10t] and
uses existing terminology defined in other BMWG work. Examples
include, but are not limited to:
Throughput [Ref.[Br91], section 3.17]
Device Under Test (DUT) [Ref.[Ma98], section 3.1.1]
System Under Test (SUT) [Ref.[Ma98], section 3.1.2]
Out-of-Order Packet [Ref.[Po06], section 3.3.4]
Duplicate Packet [Ref.[Po06], section 3.3.5]
Stream [Ref.[Po06], section 3.3.2]
Loss Period [Ref.[Ko02], section 4]
Forwarding Delay [Ref.[Po06], section 3.2.4]
IP Packet Delay Variation (IPDV) [Ref.[De02], section 1.2]
3. Test Topologies
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3.1. Test topology for local changes
Figure 1 shows the test topology to measure IGP convergence time due
to local Convergence Events such as Local Interface failure
(Section 8.1.1), layer 2 session failure (Section 8.2.1), and IGP
adjacency failure (Section 8.2.2). This topology is also used to
measure IGP convergence time due to the route withdrawal
(Section 8.2.3), and route cost change (Section 8.3.2) Convergence
Events. IGP adjacencies MUST be established between Tester and DUT,
one on the Preferred Egress Interface and one on the Next-Best Egress
Interface. For this purpose the Tester emulates two routers, each
establishing one adjacency with the DUT. An IGP adjacency SHOULD be
established on the Ingress Interface between Tester and DUT.
--------- Ingress Interface ----------
| |<--------------------------------| |
| | | |
| | Preferred Egress Interface | |
| DUT |-------------------------------->| Tester |
| | | |
| |-------------------------------->| |
| | Next-Best Egress Interface | |
--------- ----------
Figure 1: IGP convergence test topology for local changes
Figure 2 shows the test topology to measure IGP convergence time due
to local Convergence Events with a non-ECMP Preferred Egress
Interface and ECMP Next-Best Egress Interfaces (Section 8.1.1). In
this topology, the DUT is configured with each Next-Best Egress
interface as a member of a single ECMP set. The Preferred Egress
Interface is not a member of an ECMP set. The Tester emulates N+1
next-hop routers, one router for the Preferred Egress Interface and N
routers for the members of the ECMP set. IGP adjacencies MUST be
established between Tester and DUT, one on the Preferred Egress
Interface, an one on each member of the ECMP set. For this purpose
each of the N+1 routers emulated by the Tester establishes one
adjacency with the DUT. An IGP adjacency SHOULD be established on
the Ingress Interface between Tester and DUT. When the test
specifies to observe the Next-Best Egress Interface statistics, the
combined statistics for all ECMP members should be observed.
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--------- Ingress Interface ----------
| |<--------------------------------| |
| | Preferred Egress Interface | |
| |-------------------------------->| |
| | ECMP set interface 1 | |
| DUT |-------------------------------->| Tester |
| | . | |
| | . | |
| |-------------------------------->| |
| | ECMP set interface N | |
--------- ----------
Figure 2: IGP convergence test topology for local changes with non-
ECMP to ECMP convergence
3.2. Test topology for remote changes
Figure 3 shows the test topology to measure IGP convergence time due
to Remote Interface failure (Section 8.1.2). In this topology the
two routers R1 and R2 are considered System Under Test (SUT) and
SHOULD be identically configured devices of the same model. IGP
adjacencies MUST be established between Tester and SUT, one on the
Preferred Egress Interface and one on the Next-Best Egress Interface.
For this purpose the Tester emulates one or two routers. An IGP
adjacency SHOULD be established on the Ingress Interface between
Tester and SUT. In this topology there is a possibility of a
transient microloop between R1 and R2 during convergence.
------ ----------
| | Preferred | |
------ | R2 |--------------------->| |
| |-->| | Egress Interface | |
| | ------ | |
| R1 | | Tester |
| | Next-Best | |
| |------------------------------>| |
------ Egress Interface | |
^ ----------
| |
---------------------------------------
Ingress Interface
Figure 3: IGP convergence test topology for remote changes
Figure 4 shows the test topology to measure IGP convergence time due
to remote Convergence Events with a non-ECMP Preferred Egress
Interface and ECMP Next-Best Egress Interfaces (Section 8.1.2). In
this topology the two routers R1 and R2 are considered System Under
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Test (SUT) and MUST be identically configured devices of the same
model. Router R1 is configured with each Next-Best Egress interface
as a member of the same ECMP set. The Preferred Egress Interface of
R1 is not a member of an ECMP set. The Tester emulates N+1 next-hop
routers, one for R2 and one for each member of the ECMP set. IGP
adjacencies MUST be established between Tester and SUT, one on each
egress interface of SUT. For this purpose each of the N+1 routers
emulated by the Tester establishes one adjacency with the SUT. An
IGP adjacency SHOULD be established on the Ingress Interface between
Tester and SUT. In this topology there is a possibility of a
transient microloop between R1 and R2 during convergence. When the
test specifies to observe the Next-Best Egress Interface statistics,
the combined statistics for all ECMP members should be observed.
------ ----------
| | | |
------ Preferred | R2 |---->| |
| |------------------->| | | |
| | Egress Interface ------ | |
| | | |
| | ECMP set interface 1 | |
| R1 |------------------------------>| Tester |
| | . | |
| | . | |
| | . | |
| |------------------------------>| |
------ ECMP set interface N | |
^ ----------
| |
---------------------------------------
Ingress Interface
Figure 4: IGP convergence test topology for remote changes with non-
ECMP to ECMP convergence
3.3. Test topology for local ECMP changes
Figure 5 shows the test topology to measure IGP convergence time due
to local Convergence Events of a member of an Equal Cost Multipath
(ECMP) set (Section 8.1.3). In this topology, the DUT is configured
with each egress interface as a member of a single ECMP set and the
Tester emulates N next-hop routers, one router for each member. IGP
adjacencies MUST be established between Tester and DUT, one on each
member of the ECMP set. For this purpose each of the N routers
emulated by the Tester establishes one adjacency with the DUT. An
IGP adjacency SHOULD be established on the Ingress Interface between
Tester and DUT. When the test specifies to observe the Next-Best
Egress Interface statistics, the combined statistics for all ECMP
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members except the one affected by the Convergence Event, should be
observed.
--------- Ingress Interface ----------
| |<--------------------------------| |
| | | |
| | ECMP set interface 1 | |
| |-------------------------------->| |
| DUT | . | Tester |
| | . | |
| | . | |
| |-------------------------------->| |
| | ECMP set interface N | |
--------- ----------
Figure 5: IGP convergence test topology for local ECMP changes
3.4. Test topology for remote ECMP changes
Figure 6 shows the test topology to measure IGP convergence time due
to remote Convergence Events of a member of an Equal Cost Multipath
(ECMP) set (Section 8.1.4). In this topology the two routers R1 and
R2 are considered System Under Test (SUT) and MUST be identically
configured devices of the same model. Router R1 is configured with
each egress interface as a member of a single ECMP set and the Tester
emulates N next-hop routers, one router for each member. IGP
adjacencies MUST be established between Tester and SUT, one on each
egress interface of SUT. For this purpose each of the N routers
emulated by the Tester establishes one adjacency with the SUT. An
IGP adjacency SHOULD be established on the Ingress Interface between
Tester and SUT. In this topology there is a possibility of a
transient microloop between R1 and R2 during convergence. When the
test specifies to observe the Next-Best Egress Interface statistics,
the combined statistics for all ECMP members except the one affected
by the Convergence Event, should be observed.
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------ ----------
| | | |
------ ECMP set | R2 |---->| |
| |------------------->| | | |
| | Interface 1 ------ | |
| | | |
| | ECMP set interface 2 | |
| R1 |------------------------------>| Tester |
| | . | |
| | . | |
| | . | |
| |------------------------------>| |
------ ECMP set interface N | |
^ ----------
| |
---------------------------------------
Ingress Interface
Figure 6: IGP convergence test topology for remote ECMP changes
3.5. Test topology for Parallel Link changes
Figure 7 shows the test topology to measure IGP convergence time due
to local Convergence Events with members of a Parallel Link
(Section 8.1.5). In this topology, the DUT is configured with each
egress interface as a member of a Parallel Link and the Tester
emulates the single next-hop router. IGP adjacencies MUST be
established on all N members of the Parallel Link between Tester and
DUT. For this purpose the router emulated by the Tester establishes
N adjacencies with the DUT. An IGP adjacency SHOULD be established
on the Ingress Interface between Tester and DUT. When the test
specifies to observe the Next-Best Egress Interface statistics, the
combined statistics for all Parallel Link members except the one
affected by the Convergence Event, should be observed.
--------- Ingress Interface ----------
| |<--------------------------------| |
| | | |
| | Parallel Link Interface 1 | |
| |-------------------------------->| |
| DUT | . | Tester |
| | . | |
| | . | |
| |-------------------------------->| |
| | Parallel Link Interface N | |
--------- ----------
Figure 7: IGP convergence test topology for Parallel Link changes
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4. Convergence Time and Loss of Connectivity Period
Two concepts will be highlighted in this section: convergence time
and loss of connectivity period.
The Route Convergence [Po10t] time indicates the period in time
between the Convergence Event Instant [Po10t] and the instant in time
the DUT is ready to forward traffic for a specific route on its Next-
Best Egress Interface and maintains this state for the duration of
the Sustained Convergence Validation Time [Po10t]. To measure Route
Convergence time, the Convergence Event Instant and the traffic
received from the Next-Best Egress Interface need to be observed.
The Route Loss of Connectivity Period [Po10t] indicates the time
during which traffic to a specific route is lost following a
Convergence Event until Full Convergence [Po10t] completes. This
Route Loss of Connectivity Period can consist of one or more Loss
Periods [Ko02]. For the testcases described in this document it is
expected to have a single Loss Period. To measure Route Loss of
Connectivity Period, the traffic received from the Preferred Egress
Interface and the traffic received from the Next-Best Egress
Interface need to be observed.
The Route Loss of Connectivity Period is most important since that
has a direct impact on the network user's application performance.
In general the Route Convergence time is larger than or equal to the
Route Loss of Connectivity Period. Depending on which Convergence
Event occurs and how this Convergence Event is applied, traffic for a
route may still be forwarded over the Preferred Egress Interface
after the Convergence Event Instant, before converging to the Next-
Best Egress Interface. In that case the Route Loss of Connectivity
Period is shorter than the Route Convergence time.
At least one condition needs to be fulfilled for Route Convergence
time to be equal to Route Loss of Connectivity Period. The condition
is that the Convergence Event causes an instantaneous traffic loss
for the measured route. A fiber cut on the Preferred Egress
Interface is an example of such a Convergence Event.
A second condition applies to Route Convergence time measurements
based on Connectivity Packet Loss [Po10t]. This second condition is
that there is only a single Loss Period during Route Convergence.
For the testcases described in this document this is expected to be
the case.
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4.1. Convergence Events without instant traffic loss
To measure convergence time benchmarks for Convergence Events caused
by a Tester, such as an IGP cost change, the Tester MAY start to
discard all traffic received from the Preferred Egress Interface at
the Convergence Event Instant, or MAY separately observe packets
received from the Preferred Egress Interface prior to the Convergence
Event Instant. This way these Convergence Events can be treated the
same as Convergence Events that cause instantaneous traffic loss.
To measure convergence time benchmarks without instantaneous traffic
loss (either real or induced by the Tester) at the Convergence Event
Instant, such as a reversion of a link failure Convergence Event, the
Tester SHALL only observe packet statistics on the Next-Best Egress
Interface. If using the Rate-Derived method to benchmark convergence
times for such Convergence Events, the Tester MUST collect a
timestamp at the Convergence Event Instant. If using a loss-derived
method to benchmark convergence times for such Convergence Events,
the Tester MUST measure the period in time between the Start Traffic
Instant and the Convergence Event Instant. To measure this period in
time the Tester can collect timestamps at the Start Traffic Instant
and the Convergence Event Instant.
The Convergence Event Instant together with the receive rate
observations on the Next-Best Egress Interface allow to derive the
convergence time benchmarks using the Rate-Derived Method [Po10t].
By observing lost packets on the Next-Best Egress Interface only, the
observed packet loss is the number of lost packets between Traffic
Start Instant and Convergence Recovery Instant. To measure
convergence times using a loss-derived method, packet loss between
the Convergence Event Instant and the Convergence Recovery Instant is
needed. The time between Traffic Start Instant and Convergence Event
Instant must be accounted for. An example may clarify this.
Figure 8 illustrates a Convergence Event without instantaneous
traffic loss for all routes. The top graph shows the Forwarding Rate
over all routes, the bottom graph shows the Forwarding Rate for a
single route Rta. Some time after the Convergence Event Instant,
Forwarding Rate observed on the Preferred Egress Interface starts to
decrease. In the example, route Rta is the first route to experience
packet loss at time Ta. Some time later, the Forwarding Rate
observed on the Next-Best Egress Interface starts to increase. In
the example, route Rta is the first route to complete convergence at
time Ta'.
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^
Fwd |
Rate |------------- ............
| \ .
| \ .
| \ .
| \ .
|.................-.-.-.-.-.-.----------------
+----+-------+---------------+----------------->
^ ^ ^ ^ time
T0 CEI Ta Ta'
^
Fwd |
Rate |------------- .................
Rta | | .
| | .
|.............-.-.-.-.-.-.-.-.----------------
+----+-------+---------------+----------------->
^ ^ ^ ^ time
T0 CEI Ta Ta'
Preferred Egress Interface: ---
Next-Best Egress Interface: ...
With T0 the Start Traffic Instant; CEI the Convergence Event Instant;
Ta the time instant traffic loss for route Rta starts; Ta' the time
instant traffic loss for route Rta ends.
Figure 8
If only packets received on the Next-Best Egress Interface are
observed, the duration of the packet loss period for route Rta can be
calculated from the received packets as in Equation 1. Since the
Convergence Event Instant is the start time for convergence time
measurement, the period in time between T0 and CEI needs to be
subtracted from the calculated result to become the convergence time,
as in Equation 2.
Next-Best Egress Interface packet loss period
= (packets transmitted
- packets received from Next-Best Egress Interface) / tx rate
= Ta' - T0
Equation 1
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convergence time
= Next-Best Egress Interface packet loss period - (CEI - T0)
= Ta' - CEI
Equation 2
4.2. Loss of Connectivity
Route Loss of Connectivity Period SHOULD be measured using the Route-
Specific Loss-Derived Method. Since the start instant and end
instant of the Route Loss of Connectivity Period can be different for
each route, these can not be accurately derived by only observing
global statistics over all routes. An example may clarify this.
Following a Convergence Event, route Rta is the first route for which
packet loss starts, the Route Loss of Connectivity Period for route
Rta starts at time Ta. Route Rtb is the last route for which packet
loss starts, the Route Loss of Connectivity Period for route Rtb
starts at time Tb with Tb>Ta.
^
Fwd |
Rate |-------- -----------
| \ /
| \ /
| \ /
| \ /
| ---------------
+------------------------------------------>
^ ^ ^ ^ time
Ta Tb Ta' Tb'
Tb'' Ta''
Figure 9: Example Route Loss Of Connectivity Period
If the DUT implementation would be such that Route Rta would be the
first route for which traffic loss ends at time Ta' with Ta'>Tb.
Route Rtb would be the last route for which traffic loss ends at time
Tb' with Tb'>Ta'. By using only observing global traffic statistics
over all routes, the minimum Route Loss of Connectivity Period would
be measured as Ta'-Ta. The maximum calculated Route Loss of
Connectivity Period would be Tb'-Ta. The real minimum and maximum
Route Loss of Connectivity Periods are Ta'-Ta and Tb'-Tb.
Illustrating this with the numbers Ta=0, Tb=1, Ta'=3, and Tb'=5,
would give a LoC Period between 3 and 5 derived from the global
traffic statistics, versus the real LoC Period between 3 and 4.
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If the DUT implementation would be such that route Rtb would be the
first for which packet loss ends at time Tb'' and route Rta would be
the last for which packet loss ends at time Ta'', then the minimum
and maximum Route Loss of Connectivity Periods derived by observing
only global traffic statistics would be Tb''-Ta, and Ta''-Ta. The
real minimum and maximum Route Loss of Connectivity Periods are
Tb''-Tb and Ta''-Ta. Illustrating this with the numbers Ta=0, Tb=1,
Ta''=5, Tb''=3, would give a LoC Period between 3 and 5 derived from
the global traffic statistics, versus the real LoC Period between 2
and 5.
The two implementation variations in the above example would result
in the same derived minimum and maximum Route Loss of Connectivity
Periods when only observing the global packet statistics, while the
real Route Loss of Connectivity Periods are different.
5. Test Considerations
5.1. IGP Selection
The test cases described in Section 8 MAY be used for link-state
IGPs, such as ISIS or OSPF. The IGP convergence time test
methodology is identical.
5.2. Routing Protocol Configuration
The obtained results for IGP convergence time may vary if other
routing protocols are enabled and routes learned via those protocols
are installed. IGP convergence times SHOULD be benchmarked without
routes installed from other protocols.
5.3. IGP Topology
The Tester emulates a single IGP topology. The DUT establishes IGP
adjacencies with one or more of the emulated routers in this single
IGP topology emulated by the Tester. See test topology details in
Section 3. The emulated topology SHOULD only be advertised on the
DUT egress interfaces.
The number of IGP routes and number of nodes in the topology, and the
type of topology will impact the measured IGP convergence time. To
obtain results similar to those that would be observed in an
operational network, it is RECOMMENDED that the number of installed
routes and nodes closely approximate that of the network (e.g.
thousands of routes with tens or hundreds of nodes).
The number of areas (for OSPF) and levels (for ISIS) can impact the
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benchmark results.
5.4. Timers
There are timers that may impact the measured IGP convergence times.
The benchmark metrics MAY be measured at any fixed values for these
timers. To obtain results similar to those that would be observed in
an operational network, it is RECOMMENDED to configure the timers
with the values as configured in the operational network.
Examples of timers that may impact measured IGP convergence time
include, but are not limited to:
Interface failure indication
IGP hello timer
IGP dead-interval or hold-timer
LSA or LSP generation delay
LSA or LSP flood packet pacing
SPF delay
5.5. Interface Types
All test cases in this methodology document MAY be executed with any
interface type. The type of media may dictate which test cases may
be executed. Each interface type has a unique mechanism for
detecting link failures and the speed at which that mechanism
operates will influence the measurement results. All interfaces MUST
be the same media and Throughput [Br91][Br99] for each test case.
All interfaces SHOULD be configured as point-to-point.
5.6. Offered Load
The Throughput of the device, as defined in [Br91] and benchmarked in
[Br99] at a fixed packet size, needs to be determined over the
preferred path and over the next-best path. The Offered Load SHOULD
be the minimum of the measured Throughput of the device over the
primary path and over the backup path. The packet size is selectable
and MUST be recorded. Packet size is measured in bytes and includes
the IP header and payload.
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
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of the Offered Load. It is RECOMMENDED to send traffic matching all
routes, but a statistically representative subset of all routes can
be used if required.
In the Remote Interface failure testcases using topologies 3, 4, and
6 there is a possibility of a transient microloop between R1 and R2
during convergence. The TTL or Hop Limit value of the packets sent
by the Tester may influence the benchmark measurements since it
determines which device in the topology may send an ICMP Time
Exceeded Message for looped packets.
The duration of the Offered Load MUST be greater than the convergence
time plus the Sustained Convergence Validation Time.
Offered load should send a packet to each destination before sending
another packet to the same destination. It is RECOMMENDED that the
packets are transmitted in a round-robin fashion with a uniform
interpacket delay.
5.7. Measurement Accuracy
Since packet loss is observed to measure the Route Convergence Time,
the time between two successive packets offered to each individual
route is the highest possible accuracy of any packet loss based
measurement. The higher the traffic rate offered to each route the
higher the possible measurement accuracy.
Also see Section 6 for method-specific measurement accuracy.
5.8. Measurement Statistics
The benchmark measurements may vary for each trial, due to the
statistical nature of timer expirations, cpu scheduling, etc.
Evaluation of the test data must be done with an understanding of
generally accepted testing practices regarding repeatability,
variance and statistical significance of a small number of trials.
5.9. Tester Capabilities
It is RECOMMENDED that the Tester used to execute each test case has
the following capabilities:
1. Ability to establish IGP adjacencies and advertise a single IGP
topology to one or more peers.
2. Ability to measure Forwarding Delay, Duplicate Packets and Out-
of-Order Packets.
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3. An internal time clock to control timestamping, time
measurements, and time calculations.
4. Ability to distinguish traffic load received on the Preferred and
Next-Best Interfaces [Po10t].
5. Ability to disable or tune specific Layer-2 and Layer-3 protocol
functions on any interface(s).
The Tester MAY be capable to make non-data plane convergence
observations and use those observations for measurements. The Tester
MAY be capable to send and receive multiple traffic Streams [Po06].
Also see Section 6 for method-specific capabilities.
6. Selection of Convergence Time Benchmark Metrics and Methods
Different convergence time benchmark methods MAY be used to measure
convergence time benchmark metrics. The Tester capabilities are
important criteria to select a specific convergence time benchmark
method. The criteria to select a specific benchmark method include,
but are not limited to:
Tester capabilities: Sampling Interval, number of
Stream statistics to collect
Measurement accuracy: Sampling Interval, Offered Load,
number of routes
Test specification: number of routes
DUT capabilities: Throughput, IP Packet Delay
Variation
6.1. Loss-Derived Method
6.1.1. Tester capabilities
The Offered Load SHOULD consist of a single Stream [Po06]. If
sending multiple Streams, the measured packet loss statistics for all
Streams MUST be added together.
In order to verify Full Convergence completion and the Sustained
Convergence Validation Time, the Tester MUST measure Forwarding Rate
each Packet Sampling Interval.
The total number of packets lost between the start of the traffic and
the end of the Sustained Convergence Validation Time is used to
calculate the Loss-Derived Convergence Time.
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6.1.2. Benchmark Metrics
The Loss-Derived Method can be used to measure the Loss-Derived
Convergence Time, which is the average convergence time over all
routes, and to measure the Loss-Derived Loss of Connectivity Period,
which is the average Route Loss of Connectivity Period over all
routes.
6.1.3. Measurement Accuracy
The actual value falls within the accuracy interval [-(number of
destinations/Offered Load), +(number of destinations/Offered Load)]
around the value as measured using the Loss-Derived Method.
6.2. Rate-Derived Method
6.2.1. Tester Capabilities
The Offered Load SHOULD consist of a single Stream. If sending
multiple Streams, the measured traffic rate statistics for all
Streams MUST be added together.
The Tester measures Forwarding Rate each Sampling Interval. The
Packet Sampling Interval influences the observation of the different
convergence time instants. If the Packet Sampling Interval is large
compared to the time between the convergence time instants, then the
different time instants may not be easily identifiable from the
Forwarding Rate observation. 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 Packet Sampling Interval MUST be larger than or equal to the time
between two consecutive packets to the same destination. 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. The Packet Sampling Interval MUST
be reported.
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 3.
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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 3
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 3.
6.2.2. Benchmark Metrics
The Rate-Derived Method SHOULD be used to measure First Route
Convergence Time and Full Convergence Time. It SHOULD NOT be used to
measure Loss of Connectivity Period (see Section 4).
6.2.3. Measurement Accuracy
The measurement accuracy interval of the Rate-Derived Method depends
on the metric being measured or calculated and the characteristics of
the related transition. IPDV [De02] adds uncertainty to the amount
of packets received in a Packet Sampling Interval and this
uncertainty adds to the measurement error. The effect of IPDV is not
accounted for in the calculation of the accuracy intervals below.
IPDV is of importance for the convergence instants were a variation
in Forwarding Rate needs to be observed (Convergence Recovery Instant
and for topologies with ECMP also Convergence Event Instant and First
Route Convergence Instant).
If the Convergence Event Instant is observed on the dataplane using
the Rate Derived Method, it needs to be instantaneous for all routes
(see Section 4.1). The actual value of the Convergence Event Instant
falls within the accuracy interval [-(Packet Sampling Interval +
1/Offered Load), +0] around the value as measured using the Rate-
Derived Method.
If the Convergence Recovery Transition is non-instantaneous for all
routes then the actual value of the First Route Convergence Instant
falls within the accuracy interval [-(Packet Sampling Interval + time
between two consecutive packets to the same destination), +0] around
the value as measured using the Rate-Derived Method, and the actual
value of the Convergence Recovery Instant falls within the accuracy
interval [-(2 * Packet Sampling Interval), -(Packet Sampling Interval
- time between two consecutive packets to the same destination)]
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around the value as measured using the Rate-Derived Method.
The term "time between two consecutive packets to the same
destination" is added in the above accuracy intervals since packets
are sent in a particular order to all destinations in a stream and
when part of the routes experience packet loss, it is unknown where
in the transmit cycle packets to these routes are sent. This
uncertainty adds to the error.
The accuracy intervals of the derived metrics First Route Convergence
Time and Rate-Derived Convergence Time are calculated from the above
convergence instants accuracy intervals. The actual value of First
Route Convergence Time falls within the accuracy interval [-(Packet
Sampling Interval + time between two consecutive packets to the same
destination), +(Packet Sampling Interval + 1/Offered Load)] around
the calculated value. The actual value of Rate-Derived Convergence
Time falls within the accuracy interval [-(2 * Packet Sampling
Interval), +(time between two consecutive packets to the same
destination + 1/Offered Load)] around the calculated value.
6.3. Route-Specific Loss-Derived Method
6.3.1. Tester Capabilities
The Offered Load consists of multiple Streams. The Tester MUST
measure packet loss for each Stream separately.
In order to verify Full Convergence completion and the Sustained
Convergence Validation Time, the Tester MUST measure packet loss each
Packet Sampling Interval. This measurement at each Packet Sampling
Interval MAY be per Stream.
Only the total packet loss measured per Stream at the end of the
Sustained Convergence Validation Time is used to calculate the
benchmark metrics with this method.
6.3.2. Benchmark Metrics
The Route-Specific Loss-Derived Method SHOULD be used to measure
Route-Specific Convergence Times. It is the RECOMMENDED method to
measure Route Loss of Connectivity Period.
Under the conditions explained in Section 4, First Route Convergence
Time and Full Convergence Time as benchmarked using Rate-Derived
Method, may be equal to the minimum resp. maximum of the Route-
Specific Convergence Times.
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6.3.3. Measurement Accuracy
The actual value falls within the accuracy interval [-(number of
destinations/Offered Load), +(number of destinations/Offered Load)]
around the value as measured using the Route-Specific Loss-Derived
Method.
7. Reporting Format
For each test case, it is recommended that the reporting tables below
are completed and all time values SHOULD be reported with resolution
as specified in [Po10t].
Parameter Units
----------------------------------- ---------------------------
Test Case test case number
Test Topology Test Topology Figure number
IGP (ISIS, OSPF, other)
Interface Type (GigE, POS, ATM, other)
Packet Size offered to DUT bytes
Offered Load packets per second
IGP Routes advertised to DUT number of IGP routes
Nodes in emulated network number of nodes
Number of Parallel or ECMP links number of links
Number of Routes measured number of routes
Packet Sampling Interval on Tester seconds
Forwarding Delay Threshold seconds
Timer Values configured on DUT:
Interface failure indication delay seconds
IGP Hello Timer seconds
IGP Dead-Interval or hold-time seconds
LSA Generation Delay seconds
LSA Flood Packet Pacing seconds
LSA Retransmission Packet Pacing seconds
SPF Delay seconds
Test Details:
If the Offered Load matches a subset of routes, describe how this
subset is selected.
Describe how the Convergence Event is applied; does it cause
instantaneous traffic loss or not.
Complete the table below for the initial Convergence Event and the
reversion Convergence Event.
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Parameter Units
------------------------------------------ ----------------------
Conversion Event (initial or reversion)
Traffic Forwarding Metrics:
Total number of packets offered to DUT number of Packets
Total number of packets forwarded by DUT number of Packets
Connectivity Packet Loss number of Packets
Convergence Packet Loss number of Packets
Out-of-Order Packets number of Packets
Duplicate Packets number of Packets
Convergence Benchmarks:
Rate-Derived Method:
First Route Convergence Time seconds
Full Convergence Time seconds
Loss-Derived Method:
Loss-Derived Convergence Time seconds
Route-Specific Loss-Derived Method:
Route-Specific Convergence Time[n] array of seconds
Minimum R-S Convergence Time seconds
Maximum R-S Convergence Time seconds
Median R-S Convergence Time seconds
Average R-S Convergence Time seconds
Loss of Connectivity Benchmarks:
Loss-Derived Method:
Loss-Derived Loss of Connectivity Period seconds
Route-Specific Loss-Derived Method:
Route LoC Period[n] array of seconds
Minimum Route LoC Period seconds
Maximum Route LoC Period seconds
Median Route LoC Period seconds
Average Route LoC Period seconds
8. Test Cases
It is RECOMMENDED that all applicable test cases be performed for
best characterization of the DUT. The test cases follow a generic
procedure tailored to the specific DUT configuration and Convergence
Event [Po10t]. This generic procedure is as follows:
1. Establish DUT and Tester configurations and advertise an IGP
topology from Tester to DUT.
2. Send Offered Load from Tester to DUT on ingress interface.
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3. Verify traffic is routed correctly. Verify if traffic is
forwarded without drops, without Out-of-Order Packets, and
without exceeding the Forwarding Delay Threshold [Po06].
4. Introduce Convergence Event [Po10t].
5. Measure First Route Convergence Time [Po10t].
6. Measure Full Convergence Time [Po10t].
7. Stop Offered Load.
8. Measure Route-Specific Convergence Times, Loss-Derived
Convergence Time, Route LoC Periods, and Loss-Derived LoC Period
[Po10t].
9. Wait sufficient time for queues to drain. The duration of this
time period is equal to the Forwarding Delay Threshold. In
absence of a Forwarding Delay Threshold specification the
duration of this time period is 2 seconds [Br99].
10. Restart Offered Load.
11. Reverse Convergence Event.
12. Measure First Route Convergence Time.
13. Measure Full Convergence Time.
14. Stop Offered Load.
15. Measure Route-Specific Convergence Times, Loss-Derived
Convergence Time, Route LoC Periods, and Loss-Derived LoC
Period.
8.1. Interface failures
8.1.1. Convergence Due to Local Interface Failure
Objective
To obtain the IGP convergence times due to a Local Interface failure
event. The Next-Best Egress Interface can be a single interface
(Figure 1) or an ECMP set (Figure 2). The test with ECMP topology
(Figure 2) is OPTIONAL.
Procedure
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1. Advertise an IGP topology from Tester to DUT using the topology
shown in Figure 1 or 2.
2. Send Offered Load from Tester to DUT on ingress interface.
3. Verify traffic is forwarded over Preferred Egress Interface.
4. Remove link on DUT's Preferred Egress Interface. This is the
Convergence Event.
5. Measure First Route Convergence Time.
6. Measure Full Convergence Time.
7. Stop Offered Load.
8. Measure Route-Specific Convergence Times and Loss-Derived
Convergence Time.
9. Wait sufficient time for queues to drain.
10. Restart Offered Load.
11. Restore link on DUT's Preferred Egress Interface.
12. Measure First Route Convergence Time.
13. Measure Full Convergence Time.
14. Stop Offered Load.
15. Measure Route-Specific Convergence Times, Loss-Derived
Convergence Time, Route LoC Periods, and Loss-Derived LoC
Period.
Results
The measured IGP convergence time may be influenced by the link
failure indication time, LSA/LSP delay, LSA/LSP generation time, LSA/
LSP flood packet pacing, SPF delay, SPF execution time, and routing
and forwarding tables update time [Po09a].
8.1.2. Convergence Due to Remote Interface Failure
Objective
To obtain the IGP convergence time due to a Remote Interface failure
event. The Next-Best Egress Interface can be a single interface
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(Figure 3) or an ECMP set (Figure 4). The test with ECMP topology
(Figure 4) is OPTIONAL.
Procedure
1. Advertise an IGP topology from Tester to SUT using the topology
shown in Figure 3 or 4.
2. Send Offered Load from Tester to SUT on ingress interface.
3. Verify traffic is forwarded over Preferred Egress Interface.
4. Remove link on Tester's interface [Po10t] connected to SUT's
Preferred Egress Interface. This is the Convergence Event.
5. Measure First Route Convergence Time.
6. Measure Full Convergence Time.
7. Stop Offered Load.
8. Measure Route-Specific Convergence Times and Loss-Derived
Convergence Time.
9. Wait sufficient time for queues to drain.
10. Restart Offered Load.
11. Restore link on Tester's interface connected to DUT's Preferred
Egress Interface.
12. Measure First Route Convergence Time.
13. Measure Full Convergence Time.
14. Stop Offered Load.
15. Measure Route-Specific Convergence Times, Loss-Derived
Convergence Time, Route LoC Periods, and Loss-Derived LoC
Period.
Results
The measured IGP convergence time may be influenced by the link
failure indication time, LSA/LSP delay, LSA/LSP generation time, LSA/
LSP flood packet pacing, SPF delay, SPF execution time, and routing
and forwarding tables update time. This test case may produce Stale
Forwarding [Po10t] due to a transient microloop between R1 and R2
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during convergence, which may increase the measured convergence times
and loss of connectivity periods.
8.1.3. Convergence Due to ECMP Member Local Interface Failure
Objective
To obtain the IGP convergence time due to a Local Interface link
failure event of an ECMP Member.
Procedure
1. Advertise an IGP topology from Tester to DUT using the test
setup shown in Figure 5.
2. Send Offered Load from Tester to DUT on ingress interface.
3. Verify traffic is forwarded over the DUT's ECMP member interface
that will be failed in the next step.
4. Remove link on one of the DUT's ECMP member interfaces. This is
the Convergence Event.
5. Measure First Route Convergence Time.
6. Measure Full Convergence Time.
7. Stop Offered Load.
8. Measure Route-Specific Convergence Times and Loss-Derived
Convergence Time. At the same time measure Out-of-Order Packets
[Po06] and Duplicate Packets [Po06].
9. Wait sufficient time for queues to drain.
10. Restart Offered Load.
11. Restore link on DUT's ECMP member interface.
12. Measure First Route Convergence Time.
13. Measure Full Convergence Time.
14. Stop Offered Load.
15. Measure Route-Specific Convergence Times, Loss-Derived
Convergence Time, Route LoC Periods, and Loss-Derived LoC
Period. At the same time measure Out-of-Order Packets [Po06]
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and Duplicate Packets [Po06].
Results
The measured IGP Convergence time may be influenced by link failure
indication time, LSA/LSP delay, LSA/LSP generation time, LSA/LSP
flood packet pacing, SPF delay, SPF execution time, and routing and
forwarding tables update time [Po09a].
8.1.4. Convergence Due to ECMP Member Remote Interface Failure
Objective
To obtain the IGP convergence time due to a Remote Interface link
failure event for an ECMP Member.
Procedure
1. Advertise an IGP topology from Tester to DUT using the test
setup shown in Figure 6.
2. Send Offered Load from Tester to DUT on ingress interface.
3. Verify traffic is forwarded over the DUT's ECMP member interface
that will be failed in the next step.
4. Remove link on Tester's interface to R2. This is the
Convergence Event Trigger.
5. Measure First Route Convergence Time.
6. Measure Full Convergence Time.
7. Stop Offered Load.
8. Measure Route-Specific Convergence Times and Loss-Derived
Convergence Time. At the same time measure Out-of-Order Packets
[Po06] and Duplicate Packets [Po06].
9. Wait sufficient time for queues to drain.
10. Restart Offered Load.
11. Restore link on Tester's interface to R2.
12. Measure First Route Convergence Time.
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13. Measure Full Convergence Time.
14. Stop Offered Load.
15. Measure Route-Specific Convergence Times, Loss-Derived
Convergence Time, Route LoC Periods, and Loss-Derived LoC
Period. At the same time measure Out-of-Order Packets [Po06]
and Duplicate Packets [Po06].
Results
The measured IGP convergence time may influenced by the link failure
indication time, LSA/LSP delay, LSA/LSP generation time, LSA/LSP
flood packet pacing, SPF delay, SPF execution time, and routing and
forwarding tables update time. This test case may produce Stale
Forwarding [Po10t] due to a transient microloop between R1 and R2
during convergence, which may increase the measured convergence times
and loss of connectivity periods.
8.1.5. Convergence Due to Parallel Link Interface Failure
Objective
To obtain the IGP convergence due to a local link failure event for a
member of a parallel link. The links can be used for data load
balancing
Procedure
1. Advertise an IGP topology from Tester to DUT using the test
setup shown in Figure 7.
2. Send Offered Load from Tester to DUT on ingress interface.
3. Verify traffic is forwarded over the parallel link member that
will be failed in the next step.
4. Remove link on one of the DUT's parallel link member interfaces.
This is the Convergence Event.
5. Measure First Route Convergence Time.
6. Measure Full Convergence Time.
7. Stop Offered Load.
8. Measure Route-Specific Convergence Times and Loss-Derived
Convergence Time. At the same time measure Out-of-Order Packets
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[Po06] and Duplicate Packets [Po06].
9. Wait sufficient time for queues to drain.
10. Restart Offered Load.
11. Restore link on DUT's Parallel Link member interface.
12. Measure First Route Convergence Time.
13. Measure Full Convergence Time.
14. Stop Offered Load.
15. Measure Route-Specific Convergence Times, Loss-Derived
Convergence Time, Route LoC Periods, and Loss-Derived LoC
Period. At the same time measure Out-of-Order Packets [Po06]
and Duplicate Packets [Po06].
Results
The measured IGP convergence time may be influenced by the link
failure indication time, LSA/LSP delay, LSA/LSP generation time, LSA/
LSP flood packet pacing, SPF delay, SPF execution time, and routing
and forwarding tables update time [Po09a].
8.2. Other failures
8.2.1. Convergence Due to Layer 2 Session Loss
Objective
To obtain the IGP convergence time due to a local layer 2 loss.
Procedure
1. Advertise an IGP topology from Tester to DUT using the topology
shown in Figure 1.
2. Send Offered Load from Tester to DUT on ingress interface.
3. Verify traffic is routed over Preferred Egress Interface.
4. Remove Layer 2 session from DUT's Preferred Egress Interface.
This is the Convergence Event.
5. Measure First Route Convergence Time.
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6. Measure Full Convergence Time.
7. Stop Offered Load.
8. Measure Route-Specific Convergence Times, Loss-Derived
Convergence Time, Route LoC Periods, and Loss-Derived LoC
Period.
9. Wait sufficient time for queues to drain.
10. Restart Offered Load.
11. Restore Layer 2 session on DUT's Preferred Egress Interface.
12. Measure First Route Convergence Time.
13. Measure Full Convergence Time.
14. Stop Offered Load.
15. Measure Route-Specific Convergence Times, Loss-Derived
Convergence Time, Route LoC Periods, and Loss-Derived LoC
Period.
Results
The measured IGP Convergence time may be influenced by the Layer 2
failure indication time, LSA/LSP delay, LSA/LSP generation time, LSA/
LSP flood packet pacing, SPF delay, SPF execution time, and routing
and forwarding tables update time [Po09a].
Discussion
Configure IGP timers such that the IGP adjacency does not time out
before layer 2 failure is detected.
To measure convergence time, traffic SHOULD start dropping on the
Preferred Egress Interface on the instant the layer 2 session is
removed. Alternatively the Tester SHOULD record the time the instant
layer 2 session is removed and traffic loss SHOULD only be measured
on the Next-Best Egress Interface. For loss-derived benchmarks the
time of the Start Traffic Instant SHOULD be recorded as well. See
Section 4.1.
8.2.2. Convergence Due to Loss of IGP Adjacency
Objective
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To obtain the IGP convergence time due to loss of an IGP Adjacency.
Procedure
1. Advertise an IGP topology from Tester to DUT using the topology
shown in Figure 1.
2. Send Offered Load from Tester to DUT on ingress interface.
3. Verify traffic is routed over Preferred Egress Interface.
4. Remove IGP adjacency from the Preferred Egress Interface while
the layer 2 session MUST be maintained. This is the Convergence
Event.
5. Measure First Route Convergence Time.
6. Measure Full Convergence Time.
7. Stop Offered Load.
8. Measure Route-Specific Convergence Times, Loss-Derived
Convergence Time, Route LoC Periods, and Loss-Derived LoC
Period.
9. Wait sufficient time for queues to drain.
10. Restart Offered Load.
11. Restore IGP session on DUT's Preferred Egress Interface.
12. Measure First Route Convergence Time.
13. Measure Full Convergence Time.
14. Stop Offered Load.
15. Measure Route-Specific Convergence Times, Loss-Derived
Convergence Time, Route LoC Periods, and Loss-Derived LoC
Period.
Results
The measured IGP Convergence time may be influenced by the IGP Hello
Interval, IGP Dead Interval, LSA/LSP delay, LSA/LSP generation time,
LSA/LSP flood packet pacing, SPF delay, SPF execution time, and
routing and forwarding tables update time [Po09a].
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Discussion
Configure layer 2 such that layer 2 does not time out before IGP
adjacency failure is detected.
To measure convergence time, traffic SHOULD start dropping on the
Preferred Egress Interface on the instant the IGP adjacency is
removed. Alternatively the Tester SHOULD record the time the instant
the IGP adjacency is removed and traffic loss SHOULD only be measured
on the Next-Best Egress Interface. For loss-derived benchmarks the
time of the Start Traffic Instant SHOULD be recorded as well. See
Section 4.1.
8.2.3. Convergence Due to Route Withdrawal
Objective
To obtain the IGP convergence time due to route withdrawal.
Procedure
1. Advertise an IGP topology from Tester to DUT using the topology
shown in Figure 1. The routes that will be withdrawn MUST be a
set of leaf routes advertised by at least two nodes in the
emulated topology. The topology SHOULD be such that before the
withdrawal the DUT prefers the leaf routes advertised by a node
"nodeA" via the Preferred Egress Interface, and after the
withdrawal the DUT prefers the leaf routes advertised by a node
"nodeB" via the Next-Best Egress Interface.
2. Send Offered Load from Tester to DUT on Ingress Interface.
3. Verify traffic is routed over Preferred Egress Interface.
4. The Tester withdraws the set of IGP leaf routes from nodeA.
This is the Convergence Event. The withdrawal update message
SHOULD be a single unfragmented packet. If the routes cannot be
withdrawn by a single packet, the messages SHOULD be sent using
the same pacing characteristics as the DUT. The Tester MAY
record the time it sends the withdrawal message(s).
5. Measure First Route Convergence Time.
6. Measure Full Convergence Time.
7. Stop Offered Load.
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8. Measure Route-Specific Convergence Times, Loss-Derived
Convergence Time, Route LoC Periods, and Loss-Derived LoC
Period.
9. Wait sufficient time for queues to drain.
10. Restart Offered Load.
11. Re-advertise the set of withdrawn IGP leaf routes from nodeA
emulated by the Tester. The update message SHOULD be a single
unfragmented packet. If the routes cannot be advertised by a
single packet, the messages SHOULD be sent using the same pacing
characteristics as the DUT. The Tester MAY record the time it
sends the update message(s).
12. Measure First Route Convergence Time.
13. Measure Full Convergence Time.
14. Stop Offered Load.
15. Measure Route-Specific Convergence Times, Loss-Derived
Convergence Time, Route LoC Periods, and Loss-Derived LoC
Period.
Results
The measured IGP convergence time is influenced by SPF or route
calculation delay, SPF or route calculation execution time, and
routing and forwarding tables update time [Po09a].
Discussion
To measure convergence time, traffic SHOULD start dropping on the
Preferred Egress Interface on the instant the routes are withdrawn by
the Tester. Alternatively the Tester SHOULD record the time the
instant the routes are withdrawn and traffic loss SHOULD only be
measured on the Next-Best Egress Interface. For loss-derived
benchmarks the time of the Start Traffic Instant SHOULD be recorded
as well. See Section 4.1.
8.3. Administrative changes
8.3.1. Convergence Due to Local Adminstrative Shutdown
Objective
To obtain the IGP convergence time due to taking the DUT's Local
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Interface administratively out of service.
Procedure
1. Advertise an IGP topology from Tester to DUT using the topology
shown in Figure 1.
2. Send Offered Load from Tester to DUT on ingress interface.
3. Verify traffic is routed over Preferred Egress Interface.
4. Take the DUT's Preferred Egress Interface administratively out
of service. This is the Convergence Event.
5. Measure First Route Convergence Time.
6. Measure Full Convergence Time.
7. Stop Offered Load.
8. Measure Route-Specific Convergence Times, Loss-Derived
Convergence Time, Route LoC Periods, and Loss-Derived LoC
Period.
9. Wait sufficient time for queues to drain.
10. Restart Offered Load.
11. Restore Preferred Egress Interface by administratively enabling
the interface.
12. Measure First Route Convergence Time.
13. Measure Full Convergence Time.
14. Stop Offered Load.
15. Measure Route-Specific Convergence Times, Loss-Derived
Convergence Time, Route LoC Periods, and Loss-Derived LoC
Period.
16. It is possible that no measured packet loss will be observed for
this test case.
Results
The measured IGP Convergence time may be influenced by LSA/LSP delay,
LSA/LSP generation time, LSA/LSP flood packet pacing, SPF delay, SPF
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execution time, and routing and forwarding tables update time
[Po09a].
8.3.2. Convergence Due to Cost Change
Objective
To obtain the IGP convergence time due to route cost change.
Procedure
1. Advertise an IGP topology from Tester to DUT using the topology
shown in Figure 1.
2. Send Offered Load from Tester to DUT on ingress interface.
3. Verify traffic is routed over Preferred Egress Interface.
4. The Tester, emulating the neighbor node, increases the cost for
all IGP routes at DUT's Preferred Egress Interface so that the
Next-Best Egress Interface becomes preferred path. The update
message advertising the higher cost MUST be a single
unfragmented packet. This is the Convergence Event. The Tester
MAY record the time it sends the update message advertising the
higher cost on the Preferred Egress Interface.
5. Measure First Route Convergence Time.
6. Measure Full Convergence Time.
7. Stop Offered Load.
8. Measure Route-Specific Convergence Times, Loss-Derived
Convergence Time, Route LoC Periods, and Loss-Derived LoC
Period.
9. Wait sufficient time for queues to drain.
10. Restart Offered Load.
11. The Tester, emulating the neighbor node, decreases the cost for
all IGP routes at DUT's Preferred Egress Interface so that the
Preferred Egress Interface becomes preferred path. The update
message advertising the lower cost MUST be a single unfragmented
packet.
12. Measure First Route Convergence Time.
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13. Measure Full Convergence Time.
14. Stop Offered Load.
15. Measure Route-Specific Convergence Times, Loss-Derived
Convergence Time, Route LoC Periods, and Loss-Derived LoC
Period.
Results
The measured IGP Convergence time may be influenced by SPF delay, SPF
execution time, and routing and forwarding tables update time
[Po09a].
Discussion
To measure convergence time, traffic SHOULD start dropping on the
Preferred Egress Interface on the instant the cost is changed by the
Tester. Alternatively the Tester SHOULD record the time the instant
the cost is changed and traffic loss SHOULD only be measured on the
Next-Best Egress Interface. For loss-derived benchmarks the time of
the Start Traffic Instant SHOULD be recorded as well. See Section
4.1.
9. Security Considerations
Benchmarking activities as described in this memo are limited to
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 "black-box" 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.
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10. IANA Considerations
This document requires no IANA considerations.
11. Acknowledgements
Thanks to Sue Hares, Al Morton, Kevin Dubray, Ron Bonica, David Ward,
Peter De Vriendt, Anuj Dewagan and the BMWG for their contributions
to this work.
12. 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 IS-IS 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.
[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 IS-IS", RFC 5308,
October 2008.
[Ko02] Koodli, R. and R. Ravikanth, "One-way 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 Network-layer Traffic Control
Mechanisms", RFC 4689, October 2006.
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[Po09a] Poretsky, S., "Considerations for Benchmarking Link-State
IGP Data Plane Route Convergence",
draft-ietf-bmwg-igp-dataplane-conv-app-17 (work in
progress), March 2009.
[Po10t] Poretsky, S., Imhoff, B., and K. Michielsen, "Terminology
for Benchmarking Link-State IGP Data Plane Route
Convergence", draft-ietf-bmwg-igp-dataplane-conv-term-20
(work in progress), March 2010.
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
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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