RFC 4061

Benchmarking Basic OSPF Single Router Control Plane Convergence

📅 published April 2005, from ietf

Benchmarking Basic OSPF Single Router Control Plane Convergence 🎀

Okay bestie, this is RFC 4061 📜✨ and it's giving measurement science. The title is "Benchmarking Basic OSPF Single Router Control Plane Convergence," and it's an Informational doc, so it's sharing info with the Internet community and it is not a standard 🙈. It's dated April 2005 🌸

The authors are three people: V. Manral from SiNett Corp., R. White from Cisco Systems, and A. Shaikh from AT&T Labs (Research) 💅 The title block doesn't list anything it obsoletes or updates, so this one stands on its own.

Status of This Memo 🦋

Okay so this part is the legal-ish bit. This memo is just here to give information to the Internet community. It doesn't specify an Internet standard of any kind, and distribution is unlimited 💜

Copyright (C) The Internet Society (2005). 🌈

Abstract ✨

This doc gives you suggestions for measuring OSPF single router control plane convergence 🧚 The main focus is the control plane of one OSPF router, and we are not covering forwarding plane performance. Not me skipping that part 💀

NOTE: In this document, the word "convergence" relates to single router control plane convergence only.

Table of Contents 🍓

   1.  Introduction....................................................2
   2.  Specification of Requirements...................................2
   3.  Overview and Scope..............................................3
   4.  Reference Topologies............................................4
   5.  Basic Performance Tests.........................................5
       5.1.  Time Required to Process an LSA...........................5
       5.2.  Flooding Time.............................................6
       5.3.  Shortest Path First Computation Time......................6
   6.  Basic Intra-area OSPF Tests.....................................8
       6.1.  Forming Adjacencies on Point-to-Point Links
             (Initialization)..........................................9
       6.2.  Forming Adjacencies on Point-to-Point Links...............9
       6.3.  Forming Adjacencies with Information Already in the
             Database.................................................10
       6.4.  Designated Router Election Time on a Broadcast Network...11
       6.5.  Initial Convergence Time on a Broadcast Network,
             Test 1...................................................11
       6.6.  Initial Convergence Time on a Broadcast Network,
             Test 2...................................................12
       6.7.  Link Down with Layer Two Detection.......................12
       6.8.  Link Down with Layer Three Detection.....................13
   7.  Security Considerations........................................13
   8.  Acknowledgements...............................................13
   9.  Normative References...........................................14
   10. Informative References.........................................14
   Authors' Addresses.................................................15
   Full Copyright Statement...........................................16

1. Introduction 🌷

Okay so people are getting really into routing protocol convergence testing 👀 Everyone wants to know how long a network takes to settle down after something changes. The big problem is that the way you set up the test changes the results a lot. Like, deciding when the network counts as converged, or which parts of the router's job get counted, can totally change how good a routing protocol looks 😭

This doc gives a framework for testing Open Shortest Path First [OSPF] performance, plus some tests for measuring specific parts of OSPF. The whole point is to give users a set of tests that produce data they can actually compare across different vendors, so they can judge how OSPF runs on each device 💖

2. Specification of Requirements 🎀

The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be read as described in [RFC2119]. The RFC 2119 key words are used here to keep the methodology controlled, which matters a lot when you're specifying benchmarks 🧠 This document doesn't specify a network-related protocol, btw 💅

3. Overview and Scope 🦋

So this doc describes a specific set of tests for the single router control plane convergence performance of OSPF processes in routers or other boxes that have OSPF built in. The big goal is to propose methods that give you directly comparable convergence measurements 🔥

Here's what's not in scope:

  • The interactions between convergence and forwarding. Testing only covers events happening in the control plane. Forwarding performance is the main focus of [INTERCONNECT], and it's expected to be handled in work that follows from [FIB-TERM].
  • Inter-area route generation, AS-external route generation, and simultaneous traffic on the control and data paths within the DUT. The tests here do measure SPF time, flooding times, and other parts of OSPF convergence, but they don't test external or summary route generation, route translation, or other inter-area and external routing performance. Those are expected to be covered in a later document 🌈

Also, the tests should be run more than once, because one test run can't be trusted to give statistically sound results 🙈 The number of test runs and any variations between the tests should be recorded in the test results. See [TERM] for more on what should be recorded in the results.

4. Reference Topologies 🧚

Several reference topologies get used across the tests, and they're all described in this section so we don't have to repeat ourselves 🍓

Reference Topology 1 (Emulated Topology)

                     (                   )
DUT----Generator----(  emulated topology  )
                     (                   )

This is a simple back-to-back setup. The link between the generator and the DUT is assumed to be point-to-point, and the stuff inside the generator stands in for some emulated topology ✨

Reference Topology 2 (Generator and Collector)

                                    (                   )
Collector-----DUT-----Generator--(  emulated topology  )
       \              /           (                   )
        \------------/

All the routers are connected through point-to-point links. Unless it says otherwise, the cost of every link is assumed to be the same 💜

Reference Topology 3 (Broadcast Network)

DUT     R1     R2
 |      |      |
-+------+------+-----.....

Any number of routers can be on the shared broadcast network 🫶

Reference Topology 4 (Parallel Links)

  /--(link 1)-----\           (                   )
DUT               Generator--(  emulated topology  )
  \--(link 2)-----/           (                   )

In every case, the tests and topologies are built so that you can take all the performance measurements on a single device. That device can be the DUT or some other device in the network. This means you don't need synchronized clocks across the test networks, which is honestly such a relief 😭🌸

5. Basic Performance Tests 💅

These tests measure aspects of the OSPF implementation running as a process on the device under test, including:

  • time required to process an LSA,
  • flooding time, and
  • Shortest Path First computation.

5.1. Time Required to Process an LSA 🦋

  • Using reference topology 1 (Emulated Topology), start with all links up and a full adjacency between the DUT and the generator.
Note: The generator doesn't directly know the state of the adjacency on the DUT. Just because the adjacency looks Full on the generator doesn't mean the DUT is ready. It may still be requesting LSAs from the generator, and it probably is. That processing of requested LSAs will affect the results. The generator should either wait until it sees the DUT's router-LSA listing the adjacency with the generator, or add a configurable delay before the test starts 🙈
  • Send an LSA that the DUT already has (a duplicate LSA). Note the time between when the LSA is sent and when the ack comes back. This measures how long it takes to propagate the LSA and the ack, plus the processing time for the duplicate LSA. This is dupLSAprocTime 💖
  • Send a new LSA from the generator to the DUT, followed right away by a duplicate LSA. This duplicate is an LSA that's already in the DUT's database but isn't the same one just sent ✨
  • The DUT will acknowledge this second LSA immediately. Note the time of that acknowledgement. This is newLSAprocTime 🔥

To work out how long the OSPF implementation took to process the new LSA, subtract dupLSAprocTime from newLSAprocTime 🧮

Note: The duplicate LSA can't be the same as the one just sent, because of the MinLSInterval restriction [OSPF]. This test is taken from [BLACKBOX].
Note: This time may or may not include the time spent on flooding-related operations. It depends on when the implementation sends the ack: before it floods the LSA further, after it does, or somewhere in between. So this measurement might not mean the same thing across every implementation 👀

5.2. Flooding Time 🌊

  • Using reference topology 2 (Generator and Collector), turn on OSPF on all links and let the devices build full adjacencies. Then configure the collector to block all flooding toward the DUT, but keep it receiving advertisements from the DUT 🍓
  • Inject a new set of LSAs from the generator toward the collector and the DUT 🚀
  • On the collector, note when flooding is complete across the link to the generator. Also note when flooding is complete across the link from the DUT ⏱️

The time from when the last LSA arrives at the collector from the generator to when the last LSA arrives at the collector from the DUT is what this test should measure. This matters a ton in link state protocols, because the loop-free nature of the network depends on how fast revised topology information gets flooded 🔁

Depending on the number of LSAs flooded, their sizes, the number of LSUs, and the flooding rate, these numbers could vary by some amount. The settings and the variances should be reported with the test results 💜

5.3. Shortest Path First Computation Time 🧚

Okay bestie, this one is all about how long the DUT takes to run its SPF calculation 💅 Let's go through the black box version first 🖤

  • Use reference topology 1 (Emulated Topology), beginning with the DUT and the generator fully adjacent.
  • The default SPF timer on the DUT should be set to 0 so that any new LSA that arrives immediately results in the SPF calculation [BLACKBOX].
  • The generator should inject a set of LSAs toward the DUT. The DUT should be allowed to converge and install all best paths in the local routing table, etc. ✨
  • Send an LSA that is already in the DUT (a duplicate LSA), and note the time difference between when the LSA is sent and when the ack is received. This measures the time taken to propagate the LSA and the ack, as well as the processing time of the duplicate LSA. This is dupLSAprocTime. 🫶
  • Change the link cost between the generator and the emulated network it is advertising, and transmit the new LSA to the DUT.
  • Immediately inject another LSA that is a duplicate of some other LSA the generator has previously injected (preferably a stub network someplace within the emulated network).

Note: The generator should make sure that outbound LSA packing is not performed for the duplicate LSAs, and that they are always sent in a separate Link-state Update packet. Otherwise, if the LSA carrying the topology change and the duplicate LSA are in the same packet, the SPF starts after the duplicate LSA is acked. 💀

  • Measure the time between transmitting the second (duplicate) LSA and the acknowledgement for that LSA. This is the totalSPFtime. The total time required to run SPF can be computed by subtracting dupLSAprocTime from totalSPFtime. 👑

The accuracy of this test is crucially dependent on the amount of time between the transmissions of the first and second LSAs. 🥺 If too much time elapses, the test is meaningless, because the SPF run will complete before the second (duplicate) LSA is received. If the time elapsed is less, then both LSAs will be handled before the SPF run is scheduled and started, so the measurement would only be for handling the duplicate LSA. Timing is everything, babe ⏱️

This test is also specified in [BLACKBOX].

Note: This test may not be accurate on systems that implement OSPF as a multithreaded process, where the flooding takes place in a separate process (or on a different processor) than the shortest path first computations. 🙈

It's also possible to measure the SPF time using white box tests (using output supplied by the OSPF software implementer). Here's how that goes:

  • Using reference topology 1 (Emulated Topology), establish a full adjacency between the generator and the DUT.
  • Inject a set of LSAs from the generator toward the DUT. Allow the DUT to stabilize and install all best paths in the routing table, etc.
  • Change the link cost between the DUT and the generator (or the link between the generator and the emulated network it is advertising), such that a full SPF is required to run, even though only one piece of information is changed. 🔥
  • Measure the amount of time required for the DUT to compute a new shortest path tree as a result of the topology changes injected by the generator. These measurements should be taken using available show and debug information on the DUT.

Several caveats MUST be mentioned when a white box method of measuring SPF time is used. For instance, white box tests are only applicable when testing various versions or variations within a single implementation of the OSPF protocol. Further, the same set of commands MUST be used in each iteration of such a test to ensure consistent results. > Not being careful here is how you get wrong numbers, and nobody wants that 😭

There is an interesting relationship between the SPF times reported by white box (internal) testing and black box (external) testing. Each of these two types of tests can be used as a "sanity check" on the other by comparing results. 🦋

See [CONSIDERATIONS] for further discussion.

6. Basic Intra-area OSPF Tests 🌸

These tests measure how well an OSPF implementation handles basic intra-area tasks, including:

  • Forming Adjacencies on Point-to-Point Link (Initialization)
  • Forming Adjacencies on Point-to-Point Links
  • Link Up with Information Already in the Database
  • Initial convergence Time on a Designated Router Electing (Broadcast) Network
  • Link Down with Layer 2 Detection
  • Link Down with Layer 3 Detection
  • Designated Router Election Time on A Broadcast Network

This test measures the time required to form an OSPF adjacency, counted from the moment a layer two (data link) connection is formed between two devices running OSPF. ⏰

  • Use reference topology 1 (Emulated Topology), beginning with the link between the generator and DUT disabled on the DUT. OSPF should be configured and operating on both devices.
  • Inject a set of LSAs from the generator toward the DUT.
  • Bring the link up at the DUT, noting the time when the link carrier is established on the generator.
  • Note the time when the acknowledgement for the last LSA transmitted from the DUT is received on the generator.

The time between the carrier establishment and the acknowledgement for the last LSA transmitted by the generator should be taken as the total amount of time required for the OSPF process on the DUT to react to a link up event with the set of LSAs injected. That includes the time required for the operating system to notify the OSPF process about the link up, etc. The acknowledgement for the last LSA transmitted is used instead of the last acknowledgement received, so that timing skews from retransmitted acknowledgements or LSAs don't mess with the results 🧁

This test measures the time required to form an adjacency, counted from the first communication between two devices running OSPF. 📡

  • Using reference topology 1 (Emulated Topology), configure the DUT and the generator so that traffic can be passed along the link between them.
  • Configure the generator so that OSPF is running on the point-to-point link toward the DUT, and inject a set of LSAs.
  • Configure the DUT so that OSPF is initialized, but not running on the point-to-point link between the DUT and the generator.
  • Enable OSPF on the interface between the DUT and the generator, on the DUT.
  • Note the time of the first hello received from the DUT on the generator.
  • Note the time of the acknowledgement from the DUT for the last LSA transmitted on the generator.

The time between the first hello received and the acknowledgement for the last LSA transmitted by the generator should be taken as the total amount of time required for the OSPF process on the DUT to build a FULL neighbor adjacency with the set of LSAs injected. Again, the acknowledgement for the last LSA transmitted is used instead of the last acknowledgement received, to avoid timing skews from retransmitted acknowledgements or LSAs 💖

6.3. Forming Adjacencies with Information Already in the Database

  • Using reference topology 2 (Generator and Collector), configure all three devices to run OSPF.
  • Configure the DUT so that the link between the DUT and the generator is disabled.
  • Inject a set of LSAs into the network from the generator. The DUT should receive these LSAs through normal flooding from the collector.
  • Enable the link between the DUT and the generator.
  • Note the time of the first hello received from the DUT on the generator.
  • Note the time of the last DBD (Database Description) received on the generator.
  • Note the time of the acknowledgement from the DUT for the last LSA transmitted on the generator.

The time between the hello received by the generator from the DUT and the acknowledgement for the last LSA transmitted by the generator should be taken as the total amount of time required for the OSPF process on the DUT to build a FULL neighbor adjacency with the set of LSAs injected. Here the DUT already knows the entire network topology, so the time required should only include processing the DBDs exchanged while in the EXCHANGE state, the time to build a new router LSA containing the new connection information, and the time required to flood and acknowledge this new router LSA. 🧠

The acknowledgement for the last LSA transmitted is used instead of the last acknowledgement received, to prevent timing skews due to retransmitted acknowledgements or LSAs 🎀

6.4. Designated Router Election Time on a Broadcast Network

  • Using reference topology 3 (Broadcast Network), configure R1 to be the designated router on the link, and the DUT to be the backup designated router.
  • Enable OSPF on the common broadcast link on all the routers in the test bed.
  • Disable the broadcast link on R1.
  • Note the time of the last hello received from R1 on R2.
  • Note the time of the first network LSA generated by the DUT as received on R2.

The time between the last hello received on R2 and the first network LSA generated by the DUT should be taken as the amount of time required for the DUT to complete a designated router election computation. This test includes the dead interval timer at the DUT, so that time may be factored out, or the hello and dead intervals may be reduced to lessen these timers' impact on the overall test times. All changed timers, the number of routers connected to the link, and other variable factors should be noted in the test results. 🗳️

Note: If R1 sends a "goodbye hello" (typically a hello with its neighbor list empty) in the process of shutting down its interface, using the time when this hello is received instead of the time when the last one was received would provide a more accurate measurement. 🫧

6.5. Initial Convergence Time on a Broadcast Network, Test 1

  • Using reference topology 3 (Broadcast Network), begin with the DUT connected to the network with OSPF enabled. OSPF should be enabled on R1, but the broadcast link should be disabled.
  • Enable the broadcast link between R1 and the DUT. Note the time of the first hello received by R1.
  • Note the time when the first network LSA is flooded by the DUT at R1.
  • The difference between the first hello and the first network LSA is the time required by the DUT to converge on this new topology. 🌈

This test assumes that the DUT will be the designated router on the broadcast link. A similar test could be designed to test the convergence time when the DUT is not the designated router. 👑

This test can be performed with a varying number of devices attached to the broadcast network, and with varying sets of LSAs being advertised to the DUT from the routers attached to the broadcast network. Variations in the LSA sets and other factors should be noted in the test results. 📝

The time required to elect a designated router, as measured in Section 6.4, above, may be subtracted from the results of this test to provide just the convergence time across a broadcast network. 🧮

Note that although all the other tests in this document include route calculation time in the convergence time, as described in [TERM], this test may not include route calculation time in the resulting measured convergence time, because initial route calculation may occur after the first network LSA is flooded. Plot twist 😳

6.6. Initial Convergence Time on a Broadcast Network, Test 2 🦋

  • okay so, use reference topology 3 (Broadcast Network) 💖 and start with the DUT connected to the network with OSPF enabled. OSPF should be enabled on R1, but the broadcast link should be disabled 🙈
  • enable the broadcast link between R1 and the DUT. Note the time of the first hello transmitted by the DUT with a designated router listed ✨
  • note the time when the first network LSA is flooded by the DUT at R1 📣
  • the time difference between the first hello with a designated router listed and the first network LSA is the period required by the DUT to converge on this new topology 🎀 literally that's the whole vibe, bestie.
  • using reference topology 4 (Parallel Links), start with OSPF in the Full state between the generator and the DUT. Both links should be point-to-point links with the ability to notify the operating system immediately upon link failure 💅
  • disable link 1, but do it in a way where the keepalive timers at the data link layer have no impact on the DUT recognizing the link failure. The operating system in the DUT should recognize this link failure immediately ⚡ unplugging the cable on the generator end is one option, and shutting the link down is another 🍓
  • note the time of the link failure on the generator ⏰
  • at the generator, note the time of the receipt of the new router LSA from the DUT notifying the generator of the link 2 failure 🫶

Okay, so the difference between the initial link failure and the receipt of the LSA on the generator across link 2 is the time required for an OSPF implementation to recognize and process a link failure. That includes the time needed to generate and flood an LSA describing the link down event to an adjacent neighbor 🧚

  • using reference topology 4 (Parallel Links), start with OSPF in the Full state between the generator and the DUT 💜
  • disable OSPF processing on link 1 from the generator. This should be done in a way that does not affect link status. The DUT MUST note the failure of the adjacency through the dead interval 🙈
  • at the generator, note the time of the receipt of the new router LSA from the DUT notifying the generator of the link 2 failure 🫶
The difference between the initial link failure and the receipt of the LSA on the generator across link 2 is the time required for an OSPF implementation to recognize and process an adjacency failure. This is the one where the adjacency itself is the thing that gets dropped, so pay attention 👀

7. Security Considerations 🔐

Okay, bestie, this document does not modify the underlying security considerations in [OSPF]. So all the security drama lives over in [OSPF], and that's where you need to go, no cap 💀

8. Acknowledgements 🫶

Thanks to Howard Berkowitz (hcb@clark.net) for his encouragement and support. Thanks also to Alex Zinin (zinin@psg.net), Gurpreet Singh (Gurpreet.Singh@SpirentCom.com), and Yasuhiro Ohara (yasu@sfc.wide.ad.jp) for their comments 💖

9. Normative References 📚

  • [OSPF] Moy, J., "OSPF Version 2", STD 54, RFC 2328, April 1998.
  • [TERM] Manral, V., White, R., and A. Shaikh, "OSPF Benchmarking Terminology and Concepts", RFC 4062, April 2005.
  • [CONSIDERATIONS] Manral, V., White, R., and A. Shaikh, "Considerations When Using Basic OSPF Convergence Benchmarks", RFC 4063, April 2005.
  • [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997.

10. Informative References 🌈

  • [INTERCONNECT] Bradner, S. and J. McQuaid, "Benchmarking Methodology for Network Interconnect Devices", RFC 2544, March 1999.
  • [FIB-TERM] Trotter, G., "Terminology for Forwarding Information Base (FIB) based Router Performance", RFC 3222, December 2001.
  • [BLACKBOX] Shaikh, A. and Greenberg, A., "Experience in Black-box OSPF measurement", Proc. ACM SIGCOMM Internet Measurement Workshop (IMW), November 2001

Authors' Addresses 💌

Vishwas Manral
SiNett Corp,
Ground Floor,
Embassy Icon Annexe,
2/1, Infantry Road,
Bangalore, India

EMail: vishwas@sinett.com


Russ White
Cisco Systems, Inc.
7025 Kit Creek Rd.
Research Triangle Park, NC 27709

EMail: riw@cisco.com


Aman Shaikh
AT&T Labs (Research)
180 Park Av, PO Box 971
Florham Park, NJ 07932

EMail: ashaikh@research.att.com

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