Network Working Group Vishwas Manral
Internet Draft Netplane Systems
Russ White
Cisco Systems
Aman Shaikh
Expiration Date: December 2004 University of California
File Name: draft-ietf-bmwg-ospfconv-intraarea-10.txt June 2004
Benchmarking Basic OSPF Single Router Control Plane Convergence
draft-ietf-bmwg-ospfconv-intraarea-10.txt
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Abstract
This draft provides suggestions for measuring OSPF single router
control plane convergence. Its initial emphasis is on the control
plane of single OSPF routers. We do not address forwarding plane
performance.
NOTE: Within this document, the word convergence relates to single
router control plane convergence only.
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Table of Contents
1. Introduction........................................................1
2. Specification of Requirements.......................................2
3. Overview & Scope....................................................2
4. Reference Topologies................................................3
5. Basic Performance Tests.............................................4
5.1 Time Required to Process and LSA................................4
5.2 Flooding Time...................................................5
5.3 Shortest Path First Computation Time............................5
6. Basic Intra-Area OSPF Tests.........................................7
6.1 Forming Adjacencies on Point-to-Point Links (Initialization)....8
6.2 Forming Adjacencies on Point-to-Point Links.....................8
6.3 Forming Adjacencies with Information Already in the Database....9
6.4 Designated Router Election Time on a Broadcast Network.........10
6.5 Initial Convergence Time on a Broadcast Network, Test 1........11
6.6 Initial Convergence Time on a Broadcast Network, Test 2........11
6.7 Link Down with Layer Two Detection.............................12
6.8 Link Down with Layer Three Detection...........................12
7. IANA Considerations................................................13
8. Security Considerations............................................13
9. Acknowledgements...................................................13
10. Normative References..............................................13
11. Informative References............................................14
12. Author's Addresses................................................14
13. Full Copyright Statement..........................................15
14. Intellectual Property.............................................15
1. Introduction
There is a growing interest in routing protocol convergence testing,
with many people looking at various tests to determine how long it
takes for a network to converge after various conditions occur. The
major problem with this sort of testing is that the framework of the
tests has a major impact on the results; for instance, determining
when a network is converged, what parts of the router's operation are
considered within the testing, and other such things will have a
major impact on what apparent performance routing protocols provide.
This document attempts to provide a framework within which Open
Shortest Path First [OSPF] performance testing can be placed, and
provide some tests with which some aspects of OSPF performance can be
measured. The motivation of the draft is to provide a set of tests
that can provide the user comparable data from various vendors with
which to evaluate the OSPF protocol performance on the devices.
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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 interpreted as described in [RFC2119]. RFC2119
keywords in this document are used to assure methodological control,
which is very important in the specification of benchmarks. This
document does not specify a network related protocol.
3. Overview & Scope
While this document describes a specific set of tests aimed at
characterizing the single router control plane convergence
performance of OSPF processes in routers or other boxes that
incorporate OSPF functionality, a key objective is to propose
methodologies that will produce directly comparable convergence
related measurements.
Things which are outside the scope of this document include:
o The interactions of convergence and forwarding; testing is res-
tricted to events occurring within the control plane. Forwarding
performance is the primary focus in [INTERCONNECT] and it is
expected to be dealt with in work that ensues from [FIB-TERM].
o Inter-area route generation, AS-external route generation, and
simultaneous traffic on the control and data paths within the
DUT. While the tests outlined in this document measure SPF time,
flooding times, and other aspects of all OSPF convergence per-
formance, it does not provide tests for measuring external or
summary route generation, route translation, or other OSPF
inter-area and external routing performance. These are expected
to be dealt with in a later draft.
Tests should be run more than once, since a single test run can-
not be relied on to produce 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 information
on what items should be recorded in the test results).
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4. Reference Topologies
Several reference topologies will be used throughout the tests
described in the remainder of this document. Rather than repeating
these topologies, we've gathered them all in one section.
o Reference Topology 1 (Emulated Topology)
( )
DUT----Generator----( emulated topology )
( )
A simple back-to-back configuration. It's assumed that the link
between the generator and the DUT is a point-to-point link,
while the connections within the generator represent some emu-
lated topology.
o Reference Topology 2 (Generator and Collector)
( )
Collector-----DUT-----Generator--( emulated topology )
\ / ( )
\------------/
All routers are connected through point-to-point links. The cost
of all links is assumed to be the same unless otherwise noted.
o Reference Topology 3 (Broadcast Network)
DUT R1 R2
| | |
-+------+------+-----.....
Any number of routers could be included on the common broadcast
network.
o Reference Topology 4 (Parallel Links)
/--(link 1)-----\ ( )
DUT Generator--( emulated topology )
\--(link 2)-----/ ( )
In all cases the tests and topologies are designed to allow perfor-
mance measurements to be taken all on a single device, whether the
DUT or some other device in the network. This eliminates the need for
synchronized clocks within the test networks.
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5. Basic Process Performance Tests
These tests will measure aspects of the OSPF implementation as a pro-
cess on the device under test, including:
o Time required to process an LSA
o Flooding time
o Shortest Path First computation
5.1. Time required to process an LSA
o Using reference topology 1 (Emulated Topology), begin with all
links up and a full adjacency established between the DUT and
the generator.
Note: The generator does not have direct knowledge of the state
of the adjacency on the DUT. The fact the adjacency may be in
Full on the generator does not mean that the DUT is ready. It
may still (and is likely to) be requesting LSAs from the genera-
tor. This process, involving processing of requested LSAs, will
affect the results of the test. The generator should either wait
until it sees the DUT's router-LSA listing the adjacency with
the generator or introduce a configurable delay before starting
the test.
o Send an LSA that is already there in the DUT (a duplicate LSA),
note the time difference between when the LSA is sent to when
the ack is received. This measures the time to propagate the LSA
and the ack, as well as processing time of the duplicate LSA.
This is dupLSAprocTime.
o Send a new LSA from the generator to the DUT, followed immedi-
ately by a duplicate LSA (LSA that already resides in the data-
base of DUT, but not the same as the one just sent).
o The DUT will acknowledge this second LSA immediately; note the
time of this acknowledgement. This is newLSAprocTime.
The amount of time required for an OSPF implementation to pro-
cess the new LSA can be computed by subtracting dupLSAprocTime
from newLSAprocTime.
Note: The duplicate LSA cannot be the same as the one just sent
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because of the MinLSInterval restriction.[RFC2328] This test is
taken from [BLACKBOX].
Note: This time may or may not include the time required to per-
form flooding-related operations, depending on when the imple-
mentation sends the ack--before it floods the LSA further or
after, or anywhere in between. In other words, this measurement
may not mean the same thing in all implementations.
5.2. Flooding Time
o Using reference topology 2 (Generator and Collector), enable
OSPF on all links and allow the devices to build full adjacen-
cies. Configure the collector so it will block all flooding
towards the DUT, although it continues receiving advertisements
from the DUT.
o Inject a new set of LSAs from the generator towards the collec-
tor and the DUT.
o On the collector, note the time the flooding is complete across
the link to the generator. Also note the time the flooding is
complete across the link from the DUT.
The time between the last LSA is received on the collector from the
generator and the time the last LSA is received on the collector from
the DUT should be measured during this test. This time is important
in link state protocols, since the loop free nature of the network is
reliant on the speed at which revised topology information is
flooded.
Depending on the number of LSAs flooded, the sizes of the LSAs, the
number of LSUs, and the rate of flooding, these numbers could vary by
some amount. The settings and variances of these numbers should be
reported with the test results.
5.3. Shortest Path First Computation Time
o Use reference topology 1 (Emulated Topology), beginning with the
DUT and the generator fully adjacent.
o 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].
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o The generator should inject a set of LSAs towards the DUT; the
DUT should be allowed to converge and install all best paths in
the local routing table, etc..
o Send an LSA that is already there in the DUT (a duplicate LSA),
note the time difference between when the LSA is sent to when
the ack is received. This measures the time to propagate the LSA
and the ack, as well as processing time of the duplicate LSA.
This is dupLSAprocTime.
o Change the link cost between the generator and the emulated net-
work it is advertising, and transmit the new LSA to the DUT.
o Immediately inject another LSA which 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 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 will be started the duplicate LSA is acked.
o 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 subtract-
ing dupLSAprocTime from totalSPFtime.
The accuracy of this test is crucially dependant on the amount of
time between the transmission of the first and second LSAs. If there
is too much time between them, the test is meaningless because the
SPF run will complete before the second (duplicate) LSA is received.
If there is too little time between the LSAs being generated, then
they will both be handled before the SPF run is scheduled and
started, and thus the measurement would only be for the handling of
the duplicate LSA.
This test is also specified in [BLACKBOX].
Note: This test may not be accurate on systems which implement OSPF
as a multithreaded process, where the flooding takes place in a
separate process (or on a different processor) than shortest path
first computations.
It is also possible to measure the SPF time using white box tests
(using output supplied by the OSPF software implementer). For
instance:
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o Using reference topology 1 (Emulated Topology), establish a full
adjacency between the generator and the DUT.
o Inject a set of LSAs from the generator towards the DUT. Allow
the DUT to stabilize and install all best paths in the routing
table, etc.
o 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, although
only one piece of information is changed.
o Measure the amount of time required for the DUT to compute 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 using a white box method of
measuring SPF time; for instance, such white box tests are only
applicable when testing various versions or variations within a sin-
gle 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.
There is some interesting relationship between the SPF times reported
by white box (internal) testing, and black box (external) testing;
these two types of tests may be used as a "sanity check" on the other
type of tests, by comparing the results of the two tests.
See [CONSIDERATIONS] for further discussion.
6. Basic Intra-Area OSPF tests
These tests measure the performance of an OSPF implementation for
basic intra-area tasks, including:
o Forming Adjacencies on Point-to-Point Link (Initialization)
o Forming Adjacencies on Point-to-Point Links
o Link Up with Information Already in the Database
o Initial convergence Time on a Designated Router Electing (Broad-
cast) Network
o Link Down with Layer 2 Detection
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o Link Down with Layer 3 Detection
o Designated Router Election Time on A Broadcast Network
6.1. Forming Adjacencies on Point-to-Point Link (Initialization)
This test measures the time required to form an OSPF adjacency from
the time a layer two (data link) connection is formed between two
devices running OSPF.
o 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.
o Inject a set of LSAs from the generator towards the DUT.
o Bring the link up at the DUT, noting the time that the link car-
rier is established on the generator.
o Note the time 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, including 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 in
order to prevent timing skews due to retransmitted acknowledgements
or LSAs.
6.2. Forming Adjacencies on Point-to-Point Links
This test measures the time required to form an adjacency from the
time the first communication occurs between two devices running OSPF.
o Using reference topology 1 (Emulated Topology), configure the
DUT and the generator so traffic can be passed along the link
between them.
o Configure the generator so OSPF is running on the point-to-point
link towards the DUT, and inject a set of LSAs.
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o Configure the DUT so OSPF is initialized, but not running on the
point-to-point link between the DUT and the generator.
o Enable OSPF on the interface between the DUT and the generator
on the DUT.
o Note the time of the first hello received from the DUT on the
generator.
o 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. The
acknowledgement for the last LSA transmitted is used instead of the
last acknowledgement received in order to prevent timing skews due to
retransmitted acknowledgements or LSAs.
6.3. Forming adjacencies with Information Already in the Database
o Using reference topology 2 (Generator and Collector), configure
all three devices to run OSPF.
o Configure the DUT so the link between the DUT and the generator
is disabled .
o Inject a set of LSAs into the network from the generator; the
DUT should receive these LSAs through normal flooding from the
collector.
o Enable the link between the DUT and the generator.
o Note the time of the first hello received from the DUT on the
generator.
o Note the time of the last DBD received on the generator.
o Note the time of the acknowledgement from the DUT for the last
LSA transmitted on the generator.
The time between the hello received from the DUT by the generator 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
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LSAs injected. In this test, the DUT is already aware of the entire
network topology, so the time required should only include the pro-
cessing of DBDs exchanged when in 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 in order to prevent timing skews
due to retransmitted acknowledgements or LSAs.
6.4. Designated Router Election Time on A Broadcast Network
o 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.
o Enable OSPF on the common broadcast link on all the routers in
the test bed.
o Disable the broadcast link on R1.
o Note the time of the last hello received from R1 on R2.
o 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 compu-
tation. Note this test includes the dead interval timer at the DUT,
so this time may be factored out, or the hello and dead intervals
reduced to make these timers impact the overall test times less. 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 this hello is received instead of the time of the last
hello received would provide a more accurate measurement.
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6.5. Initial Convergence Time on a Broadcast Network, Test 1
o 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.
o Enable the broadcast link between R1 and the DUT. Note the time
of the first hello received by R1.
o Note the time the first network LSA is flooded by the DUT at R1.
o The differential 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 conver-
gence time when the DUT is not the designated router as well.
This test may be performed with varying numbers of devices attached
to the broadcast network, and varying sets of LSAs being advertised
to the DUT from the routers attached to the broadcast network. Varia-
tions 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 Desig-
nated Router Election Time on A Broadcast Network, above, may be sub-
tracted from the results of this test to provide just the convergence
time across a broadcast network.
Note all the other tests in the 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 conver-
gence time, because initial route calculation may occur after the
first network LSA is flooded.
6.6. Initial Convergence Time on a Broadcast Network, Test 2
o 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.
o 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.
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o Note the time the first network LSA is flooded by the DUT at R1.
o The differential between the first hello with a designated
router lists and the first network LSA is the time required by
the DUT to converge on this new topology.
6.7. Link Down with Layer 2 Detection
o Using reference topology 4 (Parallel Links), begin 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.
o Disable link 1; this should be done in such a way that the
keepalive timers at the data link layer will have no impact on
the DUT recognizing the link failure (the operating system in
the DUT should recognize this link failure immediately). Discon-
necting the cable on the generator end would be one possibility,
or shutting the link down.
o Note the time of the link failure on the generator.
o 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 in the time between the initial link failure and
the receipt of the LSA on the generator across link 2 should be
taken as the time required for an OSPF implementation to recog-
nize and process a link failure, including the time required to
generate and flood an LSA describing the link down event to an
adjacent neighbor.
6.8. Link Down with Layer 3 Detection
o Using reference topology 4 (Parallel Links), begin with OSPF in
the full state between the generator and the DUT.
o Disable OSPF processing on link 1 from the generator. This
should be done in such a way so it does not affect link status;
the DUT MUST note the failure of the adjacency through the dead
interval.
o 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.
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The difference in the time between the initial link failure and the
receipt of the LSA on the generator across link 2 should be taken as
the time required for an OSPF implementation to recognize and process
an adjacency failure.
7. IANA Considerations
This document requires no IANA considerations.
8. Security Considerations
This document does not modify the underlying security considerations
in [OSPF].
9. 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 as well.
10. Normative References
[OPSF]Moy, J., "OSPF Version 2", RFC 2328, April 1998.
[TERM]Manral, V., "OSPF Convergence Testing Terminology and Con-
cepts", draft-ietf-bmwg-ospfconv-term-10, June 2004
[CONSIDERATIONS]
Manral, V., "Considerations When Using Basic OSPF Convergence
Benchmarks", draft-ietf-bmwg-ospfconv-applicability-07, June
2004
[RFC2119]
Bradner, S., "Key words for use in RFCs to Indicate Requirement
Levels", BCP 14, RFC 2119, March 1997
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11. Informative References
[INTERCONNECT]
Bradner, S., McQuaid, J., "Benchmarking Methodology for Network
Interconnect Devices", RFC2544, March 1999.
[MILLISEC]
Alaettinoglu C., et al., "Towards Milli-Second IGP Convergence"
draft-alaettinoglu-isis-convergence
[FIB-TERM]
Trotter, G., "Terminology for Forwarding Information Base (FIB)
based Router Performance", RFC3222, October 2001.
[BLACKBOX]
Shaikh, Aman, Greenberg, Albert, "Experience in Black-Box OSPF
measurement"
12. Authors' Addresses
Vishwas Manral
Netplane Systems
189 Prashasan Nagar
Road number 72
Jubilee Hills
Hyderabad, India
vmanral@netplane.com
Russ White
Cisco Systems, Inc.
7025 Kit Creek Rd.
Research Triangle Park, NC 27709
riw@cisco.com
Aman Shaikh
AT&T Labs (Research)
180, Park Av
Florham Park, NJ 07932
ashaikh@research.att.com
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