Benchmarking Methodology for Link-State IGP Data Plane Route Convergence
draft-ietf-bmwg-igp-dataplane-conv-meth-18

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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.

Table of Contents

1.  Introduction and Scope
2.  Existing Definitions
3.  Test Topologies
    3.1.  Test topology for local changes
    3.2.  Test topology for remote changes
    3.3.  Test topology for local ECMP changes
    3.4.  Test topology for remote ECMP changes
    3.5.  Test topology for Parallel Link changes
4.  Convergence Time and Loss of Connectivity Period
5.  Test Considerations
    5.1.  IGP Selection
    5.2.  Routing Protocol Configuration
    5.3.  IGP Topology
    5.4.  Timers
    5.5.  Interface Types
    5.6.  Offered Load
    5.7.  Measurement Accuracy
    5.8.  Measurement Statistics
    5.9.  Tester Capabilities
6.  Selection of Convergence Time Benchmark Metrics and Methods
    6.1.  Loss-Derived Method
        6.1.1.  Tester capabilities
        6.1.2.  Benchmark Metrics
        6.1.3.  Measurement Accuracy
    6.2.  Rate-Derived Method
        6.2.1.  Tester Capabilities
        6.2.2.  Benchmark Metrics
        6.2.3.  Measurement Accuracy
    6.3.  Route-Specific Loss-Derived Method
        6.3.1.  Tester Capabilities
        6.3.2.  Benchmark Metrics
        6.3.3.  Measurement Accuracy
7.  Reporting Format
8.  Test Cases
    8.1.  Interface failures
        8.1.1.  Convergence Due to Local Interface Failure
        8.1.2.  Convergence Due to Remote Interface Failure
        8.1.3.  Convergence Due to ECMP Member Local Interface Failure
        8.1.4.  Convergence Due to ECMP Member Remote Interface Failure
        8.1.5.  Convergence Due to Parallel Link Interface Failure
    8.2.  Other failures
        8.2.1.  Convergence Due to Layer 2 Session Loss
        8.2.2.  Convergence Due to Loss of IGP Adjacency
        8.2.3.  Convergence Due to Route Withdrawal
    8.3.  Administrative changes
        8.3.1.  Convergence Due to Local Adminstrative Shutdown
        8.3.2.  Convergence Due to Cost Change
9.  Security Considerations
10.  IANA Considerations
11.  Acknowledgements
12.  Normative References
§  Authors' Addresses

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] (Poretsky, S., “Considerations for Benchmarking Link-State IGP Data Plane Route Convergence,” March 2009.). The terminology to be used for this benchmarking is described in [Po09t] (Poretsky, S. and B. Imhoff, “Terminology for Benchmarking Link-State IGP Data Plane Route Convergence,” July 2009.).

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] (Poretsky, S., “Considerations for Benchmarking Link-State IGP Data Plane Route Convergence,” March 2009.). The test cases in this document are black-box tests that emulate the network events that cause convergence, as described in [Po09a] (Poretsky, S., “Considerations for Benchmarking Link-State IGP Data Plane Route Convergence,” March 2009.).

The methodology described in this document can be applied to IPv4 and IPv6 traffic and link-state IGPs such as ISIS [Ca90] (Callon, R., “Use of OSI IS-IS for routing in TCP/IP and dual environments,” December 1990.)[Ho08] (Hopps, C., “Routing IPv6 with IS-IS,” October 2008.), OSPF [Mo98] (Moy, J., “OSPF Version 2,” April 1998.)[Co08] (Coltun, R., Ferguson, D., Moy, J., and A. Lindem, “OSPF for IPv6,” July 2008.), 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] (Bradner, S., “Key words for use in RFCs to Indicate Requirement Levels,” March 1997.). 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 [Po09t] (Poretsky, S. and B. Imhoff, “Terminology for Benchmarking Link-State IGP Data Plane Route Convergence,” July 2009.) and uses existing terminology defined in other BMWG work. Examples include, but are not limited to:

3.  Test Topologies

3.1.  Test topology for local changes

Figure 1 (IGP convergence test topology for local changes) shows the test topology to measure IGP convergence time due to local Convergence Events such as Local Interface failure (Section 8.1.1 (Convergence Due to Local Interface Failure)), layer 2 session failure (Section 8.2.1 (Convergence Due to Layer 2 Session Loss)), and IGP adjacency failure (Section 8.2.2 (Convergence Due to Loss of IGP Adjacency)). This topology is also used to measure IGP convergence time due to the route withdrawal (Section 8.2.3 (Convergence Due to Route Withdrawal)), and route cost change (Section 8.3.2 (Convergence Due to Cost Change)) Convergence Events. IGP adjancencies 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 MAY be established on the Ingress Interface between Tester and DUT.

---------       Ingress Interface         ----------
|       |<--------------------------------|        |
|       |                                 |        |
|       |    Preferred Egress Interface   |        |
|  DUT  |-------------------------------->| Tester |
|       |                                 |        |
|       |-------------------------------->|        |
|       |    Next-Best Egress Interface   |        |
---------                                 ----------

3.2.  Test topology for remote changes

Figure 2 (IGP convergence test topology for remote changes) shows the test topology to measure IGP convergence time due to Remote Interface failure (Section 8.1.2 (Convergence Due to Remote Interface Failure)). 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 adjancencies 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 MAY 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

3.3.  Test topology for local ECMP changes

Figure 3 (IGP convergence test topology for local ECMP change) shows the test topology to measure IGP convergence time due to local Convergence Events with members of an Equal Cost Multipath (ECMP) set (Section 8.1.3 (Convergence Due to ECMP Member Local Interface Failure)). 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 adjancencies 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 MAY be established on the Ingress Interface between Tester and DUT.

---------       Ingress Interface         ----------
|       |<--------------------------------|        |
|       |                                 |        |
|       |     ECMP set interface 1        |        |
|       |-------------------------------->|        |
|  DUT  |               .                 | Tester |
|       |               .                 |        |
|       |               .                 |        |
|       |-------------------------------->|        |
|       |     ECMP set interface N        |        |
---------                                 ----------

3.4.  Test topology for remote ECMP changes

Figure 4 (IGP convergence test topology for remote ECMP convergence) shows the test topology to measure IGP convergence time due to remote Convergence Events with members of an Equal Cost Multipath (ECMP) set (Section 8.1.4 (Convergence Due to ECMP Member Remote Interface Failure)). 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. Route 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 adjancencies 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 MAY 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.

                          ------     ----------
                          |    |     |        |
------      ECMP set      | R2 |---->|        |
|    |------------------->|    |     |        |
|    |      Interface 1   ------     |        |
|    |                               |        |
|    |      ECMP set interface 2     |        |
| R1 |------------------------------>| Tester |
|    |               .               |        |
|    |               .               |        |
|    |               .               |        |
|    |------------------------------>|        |
------      ECMP set interface N     |        |
   ^                                 ----------
   |                                     |
   ---------------------------------------
               Ingress Interface

3.5.  Test topology for Parallel Link changes

Figure 5 (IGP convergence test topology for Parallel Link changes) shows the test topology to measure IGP convergence time due to local Convergence Events with members of a Parallel Link (Section 8.1.5 (Convergence Due to Parallel Link Interface Failure )). 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 adjancencies 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 MAY be established on the Ingress Interface between Tester and DUT.

---------       Ingress Interface         ----------
|       |<--------------------------------|        |
|       |                                 |        |
|       |     Parallel Link Interface 1   |        |
|       |-------------------------------->|        |
|  DUT  |               .                 | Tester |
|       |               .                 |        |
|       |               .                 |        |
|       |-------------------------------->|        |
|       |     Parallel Link Interface N   |        |
---------                                 ----------

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 [Po09t] (Poretsky, S. and B. Imhoff, “Terminology for Benchmarking Link-State IGP Data Plane Route Convergence,” July 2009.) time indicates the period in time between the Convergence Event Instant [Po09t] (Poretsky, S. and B. Imhoff, “Terminology for Benchmarking Link-State IGP Data Plane Route Convergence,” July 2009.) 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 [Po09t] (Poretsky, S. and B. Imhoff, “Terminology for Benchmarking Link-State IGP Data Plane Route Convergence,” July 2009.). 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 [Po09t] (Poretsky, S. and B. Imhoff, “Terminology for Benchmarking Link-State IGP Data Plane Route Convergence,” July 2009.) indicates the time during which traffic to a specific route is lost following a Convergence Event until Full Convergence [Po09t] (Poretsky, S. and B. Imhoff, “Terminology for Benchmarking Link-State IGP Data Plane Route Convergence,” July 2009.) completes. This Route Loss of Connectivity Period can consist of one or more Loss Periods [Ko02] (Koodli, R. and R. Ravikanth, “One-way Loss Pattern Sample Metrics,” August 2002.). 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 need 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. For Convergence Events caused by the Tester, such as an IGP cost change, the Tester may start to drop all traffic received from the Preferred Egress Interface at the Convergence Event Instant to achieve the same result.

A second condition applies to Route Convergence time measurements based on Connectivity Packet Loss [Po09t] (Poretsky, S. and B. Imhoff, “Terminology for Benchmarking Link-State IGP Data Plane Route Convergence,” July 2009.).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.

To measure convergence time without real instantaneous traffic loss at the Convergence Event Instant, such as a reversion of a link failure Convergence Event, the Tester SHOULD collect a timestamp at the time instant traffic starts and a timestamp at the Convergence Event Instant, and only observe packet statistics on the Next-Best Egress Interface.

The Convergence Event Instant together with the receive rate observations on the Next-Best Egress Interface allow to derive the convergence benchmarks using the Rate-Derived Method [Po09t] (Poretsky, S. and B. Imhoff, “Terminology for Benchmarking Link-State IGP Data Plane Route Convergence,” July 2009.).

By observing lost packets on the Next-Best Egress Interface only, the measured packet loss is the number of lost packets between traffic start 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 and Convergence Event Instant must be accounted for

Figure 6 illustrates a Convergence Event without instantaneous traffic loss for all routes. The top graph shows the Forwarding Rate over all routes, the bottem 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'.

     ^
Fwd  |
Rate |-------------                    ............
     |             \                  .
     |              \                .
     |               \              .
     |                \            .
     |.................-.-.-.-.-.-.----------------
     +----+-------+---------------+----------------->
     ^    ^       ^               ^             time
    T0   CEI      Ta              Ta'

     ^
Fwd  |
Rate |-------------               .................
Rta  |            |               .
     |            |               .
     |.............-.-.-.-.-.-.-.-.----------------
     +----+-------+---------------+----------------->
     ^    ^       ^               ^             time
    T0   CEI      Ta              Ta'

     Preferred Egress Interface: ---
     Next-Best Egress Interface: ...

With CEI the Convergence Event Instant; T0 the time instant traffic starts; Ta the time instant traffic loss for route Rta starts; Ta' the time instant traffic loss for route Rta ends.

If only packets received on the Next-Best Egress Interface are observed, the duration of the packet loss period for route Rta observed on the Next-Best Egress Interface 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 substracted 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

convergence time
    = Next-Best Egress Interface packet loss period - (CEI - T0)
    = Ta' - CEI

Equation 2

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''

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.

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 4 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 MUST 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 topology details in Section 3 (Test Topologies). The emulated topology SHOULD only be advertised on the DUT egress interfaces.

The number of IGP routes will impact the measured IGP route 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 approximates 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 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

LSA or LSP retransmission 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. This is because 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] (Bradner, S., “Benchmarking terminology for network interconnection devices,” July 1991.)[Br99] (Bradner, S. and J. McQuaid, “Benchmarking Methodology for Network Interconnect Devices,” March 1999.) 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] (Bradner, S., “Benchmarking terminology for network interconnection devices,” July 1991.) and benchmarked in [Br99] (Bradner, S. and J. McQuaid, “Benchmarking Methodology for Network Interconnect Devices,” March 1999.) 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 minumum 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.

In the Remote Interface failure testcases using topologies 2 (IGP convergence test topology for remote changes) and 4 (IGP convergence test topology for remote ECMP convergence) there is a possibility of a transient microloop between R1 and R2 during convergence. The TTL value of the packets send 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.

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. When packet jitter is much less than the convergence time, it is a negligible source of error and therefor it will be ignored here.

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 insert a timestamp in each data packet's IP payload.
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 [Po09t] (Poretsky, S. and B. Imhoff, “Terminology for Benchmarking Link-State IGP Data Plane Route Convergence,” July 2009.).
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] (Poretsky, S., Perser, J., Erramilli, S., and S. Khurana, “Terminology for Benchmarking Network-layer Traffic Control Mechanisms,” October 2006.).

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:

6.1.  Loss-Derived Method

6.1.1.  Tester capabilities

The Offered Load SHOULD consist of a single Stream [Po06] (Poretsky, S., Perser, J., Erramilli, S., and S. Khurana, “Terminology for Benchmarking Network-layer Traffic Control Mechanisms,” October 2006.). If sending multiple Streams, the measured packet loss statistics for all Streams MUST be added together.

The destination addresses for the Offered Load MUST be distributed such that all routes are matched and each route is offered an equal share of the total Offered Load.

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.

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

TBD

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 destination addresses for the Offered Load MUST be distributed such that all routes are matched and each route is offered an equal share of the total Offered Load.

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 in comparison to the time between the convergence time instants, then the different time instants may not be easily identifiable from the Forwarding Rate observation. The requirements for the Packet Sampling Interval are specified in [Po09t] (Poretsky, S. and B. Imhoff, “Terminology for Benchmarking Link-State IGP Data Plane Route Convergence,” July 2009.). The RECOMMENDED value for the Packet Sampling Interval is 10 milliseconds. The Packet Sampling Interval MUST be reported.

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 Section 4 (Convergence Time and Loss of Connectivity Period)).

6.2.3.  Measurement Accuracy

The measurement accuracy of the Rate-Derived Method for transitions that occur for all routes at the same instant is equal to the Packet Sampling Interval and for other transitions the measurement accuracy is equal to the Packet Sampling Interval plus the time between two consecutive packets to the same destination. The latter is the case 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.

6.3.  Route-Specific Loss-Derived Method

6.3.1.  Tester Capabilities

The Offered Load consists of multiple Streams. To measure Route-Specific Convergence Times, the Tester sends one Stream to each route in the FIB. The Tester MUST measure packet loss for each Stream seperately.

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 (Convergence Time and Loss of Connectivity Period), 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.

6.3.3.  Measurement Accuracy

The measurement accuracy of the Route-Specific Loss-Derived Method is equal to the time between two consecutive packets to the same route.

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 [Po09t] (Poretsky, S. and B. Imhoff, “Terminology for Benchmarking Link-State IGP Data Plane Route Convergence,” July 2009.).

Complete the table below for the initial Convergence Event and the reversion Convergence Event.

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[Po09t] (Poretsky, S. and B. Imhoff, “Terminology for Benchmarking Link-State IGP Data Plane Route Convergence,” July 2009.). 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.
3. Verify traffic is routed correctly.
4. Introduce Convergence Event [Po09t] (Poretsky, S. and B. Imhoff, “Terminology for Benchmarking Link-State IGP Data Plane Route Convergence,” July 2009.).
5. Measure First Route Convergence Time [Po09t] (Poretsky, S. and B. Imhoff, “Terminology for Benchmarking Link-State IGP Data Plane Route Convergence,” July 2009.).
6. Measure Full Convergence Time [Po09t] (Poretsky, S. and B. Imhoff, “Terminology for Benchmarking Link-State IGP Data Plane Route Convergence,” July 2009.).
7. Stop Offered Load.
8. Measure Route-Specific Convergence Times, Loss-Derived Convergence Time, Route LoC Periods, and Loss-Derived LoC Period [Po09t] (Poretsky, S. and B. Imhoff, “Terminology for Benchmarking Link-State IGP Data Plane Route Convergence,” July 2009.).
9. Wait sufficient time for queues to drain.
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.

Procedure

1. Advertise an IGP topology from Tester to DUT using the topology shown in Figure 1 (IGP convergence test topology for local changes).
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] (Poretsky, S., “Considerations for Benchmarking Link-State IGP Data Plane Route Convergence,” March 2009.).

8.1.2.  Convergence Due to Remote Interface Failure

Objective

To obtain the IGP convergence time due to a Remote Interface failure event.

Procedure

1. Advertise an IGP topology from Tester to SUT using the topology shown in Figure 2.
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 [Po09t] (Poretsky, S. and B. Imhoff, “Terminology for Benchmarking Link-State IGP Data Plane Route Convergence,” July 2009.) 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 [Po09t] (Poretsky, S. and B. Imhoff, “Terminology for Benchmarking Link-State IGP Data Plane Route Convergence,” July 2009.) due to a transient microloop between R1 and R2 during convergence, which may increase the measured convergence times and loss of connectivity periods.

8.1.3.  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 3.
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] (Poretsky, S., Perser, J., Erramilli, S., and S. Khurana, “Terminology for Benchmarking Network-layer Traffic Control Mechanisms,” October 2006.) and Duplicate Packets [Po06] (Poretsky, S., Perser, J., Erramilli, S., and S. Khurana, “Terminology for Benchmarking Network-layer Traffic Control Mechanisms,” October 2006.).
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] (Poretsky, S., Perser, J., Erramilli, S., and S. Khurana, “Terminology for Benchmarking Network-layer Traffic Control Mechanisms,” October 2006.) and Duplicate Packets [Po06] (Poretsky, S., Perser, J., Erramilli, S., and S. Khurana, “Terminology for Benchmarking Network-layer Traffic Control Mechanisms,” October 2006.).

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] (Poretsky, S., “Considerations for Benchmarking Link-State IGP Data Plane Route Convergence,” March 2009.).

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 4.
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] (Poretsky, S., Perser, J., Erramilli, S., and S. Khurana, “Terminology for Benchmarking Network-layer Traffic Control Mechanisms,” October 2006.) and Duplicate Packets [Po06] (Poretsky, S., Perser, J., Erramilli, S., and S. Khurana, “Terminology for Benchmarking Network-layer Traffic Control Mechanisms,” October 2006.).
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.
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] (Poretsky, S., Perser, J., Erramilli, S., and S. Khurana, “Terminology for Benchmarking Network-layer Traffic Control Mechanisms,” October 2006.) and Duplicate Packets [Po06] (Poretsky, S., Perser, J., Erramilli, S., and S. Khurana, “Terminology for Benchmarking Network-layer Traffic Control Mechanisms,” October 2006.).

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 [Po09t] (Poretsky, S. and B. Imhoff, “Terminology for Benchmarking Link-State IGP Data Plane Route Convergence,” July 2009.) 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 5.
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 [Po06] (Poretsky, S., Perser, J., Erramilli, S., and S. Khurana, “Terminology for Benchmarking Network-layer Traffic Control Mechanisms,” October 2006.) and Duplicate Packets [Po06] (Poretsky, S., Perser, J., Erramilli, S., and S. Khurana, “Terminology for Benchmarking Network-layer Traffic Control Mechanisms,” October 2006.).
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] (Poretsky, S., Perser, J., Erramilli, S., and S. Khurana, “Terminology for Benchmarking Network-layer Traffic Control Mechanisms,” October 2006.) and Duplicate Packets [Po06] (Poretsky, S., Perser, J., Erramilli, S., and S. Khurana, “Terminology for Benchmarking Network-layer Traffic Control Mechanisms,” October 2006.).

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] (Poretsky, S., “Considerations for Benchmarking Link-State IGP Data Plane Route Convergence,” March 2009.).

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.
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] (Poretsky, S., “Considerations for Benchmarking Link-State IGP Data Plane Route Convergence,” March 2009.).

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.

8.2.2.  Convergence Due to Loss of IGP Adjacency

Objective

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] (Poretsky, S., “Considerations for Benchmarking Link-State IGP Data Plane Route Convergence,” March 2009.).

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.

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. The withdrawal update message MUST be a single unfragmented packet. This is the Convergence Event. 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.
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 MUST be a single unfragmented packet.
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] (Poretsky, S., “Considerations for Benchmarking Link-State IGP Data Plane Route Convergence,” March 2009.).

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.

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 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 execution time, and routing and forwarding tables update time [Po09a] (Poretsky, S., “Considerations for Benchmarking Link-State IGP Data Plane Route Convergence,” March 2009.).

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.
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] (Poretsky, S., “Considerations for Benchmarking Link-State IGP Data Plane Route Convergence,” March 2009.).

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.

9.  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. 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 methodology for benchmarking IGP convergence performance in a lab environment.

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 and the BMWG for their contributions to this work.

12. Normative References

Authors' Addresses