Internet DRAFT - draft-bmwg-ospfconv-intraarea
draft-bmwg-ospfconv-intraarea
Network Working Group Vishwas Manral
Internet Draft Netplane Systems
Russ White
Cisco Systems
Aman Shaikh
Expiration Date: October 2002 University of California
File Name: draft-bmwg-ospfconv-intraarea-00.txt May 2002
Benchmarking Methodology for Basic OSPF Convergence
draft-bmwg-ospfconv-intraarea-00.txt
1. Status of this Memo
This document is an Internet-Draft and is in full conformance with
all provisions of Section 10 of RFC2026.
Internet Drafts are working documents of the Internet Engineering
Task Force (IETF), its Areas, and its Working Groups. Note that other
groups may also distribute working documents as Internet Drafts.
Internet Drafts are draft documents valid for a maximum of six
months. Internet Drafts may be updated, replaced, or obsoleted by
other documents at any time. It is not appropriate to use Internet
Drafts as reference material or to cite them other than as a "working
draft" or "work in progress".
The list of current Internet-Drafts can be accessed at
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The list of Internet-Draft Shadow Directories can be accessed at
http://www.ietf.org/shadow.html.
2. Abstract
This draft establishes standards for measuring OSPF convergence
performance on a single router (SR-Convergence [4]). Its initial
emphasis is on the control plane of single OSPF routers. We do not
address forwarding plane performance.
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3. Conventions used in this document
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 [1].
4. Motivation
There is a growing interest in routing protocol SR-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) [2] 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.
5. Overview & Scope
While this document describes a specific set of tests aimed at
characterizing the SR-Convergence performance of OSPF processes in
routers or other boxes that incorporate OSPF functionality, a key
objective is to propose methodology that will standardize the
conducting and reporting of convergence-related measurements.
Things which are outside the scope of this document include:
o The interactions of SR-Convergence and forwarding; testing is
restricted to events occurring within the control plane. For-
warding performance is the primary focus in [3] and it is
expected to be dealt with in work that ensues from [6].
o Inter area routing, AS-external routing, and simultaneous
traffic on the control and data paths within the DUT.
Other drafts in the future may cover some of the items noted as not
covered in the scope of this draft. For a discussion of the
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terminology used in this draft (in relation to the tests themselves),
refer to [4].
6. Test Conditions
In all tests, the following test conditions will be assumed:
o The link speed should be high enough so that does not become
a bottleneck. Link speeds of 10MBps or higher are recom-
mended. The link speed between routers should be specified in
the test report.
o For all point-to-point links, it is assumed that a link
failure results in an immediate notification to the operating
system, and thus to the OSPF process; this is explained
thoroughly in [5].
o No data traffic will be running between the routers during
these tests.
o Optional capabilities which can reduce performance, such as
authentication, should be noted in the test results if they
are enabled.
o Optional changes in the default timer values, such as the
SPF, hello, router dead, and other intervals, should be noted
in the test results.
o All places where injecting a set of LSAs is referenced, the
set can include varying numbers of LSAs of varying types
representing a varying number of reachable destinations. See
[4] for further information about issues with LSA sets and
network topologies.
Tests should be run more than once, since a single test run
cannot 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 [4] for more
information on what items should be recorded in the test
results).
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7. 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
( )
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 emulated topology.
o Reference Topology 2
( )
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
DUT R1 R2
| | |
-+------+------+-----.....
Any number of routers could be included on the common broad-
cast network.
o Reference Topology 4
/--(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
syncronized clocks within the test networks.
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8. 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
8.1. Time required to process an LSA
o Using reference topology 1, begin with all links up and a
full adjacency established between the DUT and the generator.
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 pro-
pagate 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
immediately by a duplicate LSA (LSA that already resides in
the database 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
process the new LSA can be computed by subtracting
dupLSAprocTime from newLSAprocTime.
Note: The duplicate LSA cannot be the same as the one just
sent because of the MinLSInterval restriction.[RFC2328] This
test is taken from [7].
8.2. Flooding Time
o Using reference topology 2, enable OSPF on all links and
allow the devices to build full adjacencies. Configure the
collector so it will block all flooding towards the DUT,
although it continues receiving advertisements from the
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DUT.
o Inject a new set of LSAs from the generator towards the
collector 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.
Two measurements can be taken from this test:
o The time between the last LSA is received on the collec-
tor from the generator and the time the last LSA is
received on the collector from the DUT.
o The time between the last LSA is received on the collector
from the generator and the time the first LSA is received
on the collector from the DUT.
Depending on the number of LSAs flooded, the sizes of the
LSAs, 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.
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.
8.3. Shortest Path First Computation Time (Internal Test)
o Using reference topology 1, 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
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injected by the generator. These measurements should be
taken using available show and debug information on the
DUT.
The test results should note what available commands were
used to determine the length of the shortest path first run,
and should note any performance implications of monitoring
the SPF calculations using information available from the DUT
itself.
8.4. Shortest Path First Computation Time (External Test)
o Use reference topology 1, 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 [7].
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 emu-
lated network it is advertising.
o Immediately inject another LSA which is a duplicate of
some other LSA the generator has previously injected
(preferrably a stub network someplace within the emulated
network).
o Measure the time between transmitting the second (dupli-
cate) 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 totalSPF-
time.
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
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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 dupli-
cate LSA.
This test is also specified in [7].
Note: This test may not be accurate on systems which imple-
ment OSPF as a multithreaded process, where the flooding
takes place in a separate process (or on a different proces-
sor) than shortest path first computations.
9. 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 SR-Convergence Time on a DR electing (broadcast) network
o Point-to-point Link Down with Layer 2 Detection
o Broadcast Media Link Down with Layer 3 Detection
o Designated Router Election Time on A Broadcast Network
9.1. Forming Adjacencies on Point-to-Point Link Initialization
o Use reference topology 1, 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 carrier is established on the generator.
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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 ack-
nowledgement 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.
9.2. Forming Adjacencies on Point-to-Point Links
o Using reference topology 1, configure the DUT and the gen-
erator 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.
o Configure the DUT so OSPF is initialized, but not running
on the point-to-point link between the DUT and the genera-
tor.
o Enable OSPF on the interface between the DUT and the gen-
erator 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 ack-
nowledgement 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 acknowledge-
ment received in order to prevent timing skews due to
retransmitted acknowledgements or LSAs.
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9.3. Link Up with Information Already in the Database
o Using reference topology 2, configure all three devices to
run OSPF.
o Configure the DUT so the link between the DUT and the gen-
erator 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 acknowledgement from the DUT for the
last LSA transmitted on the generator.
The time between the hello received from the DUT by the gen-
erator 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. In this
test, the DUT is already aware of the entire network topol-
ogy, so the time required should only include the processing
of each LSA from the generator and transmitting an ack-
nowledgement. The acknowledgement for the last LSA transmit-
ted is used instead of the last acknowledgement received in
order to prevent timing skews due to retransmitted ack-
nowledgements or LSAs.
9.4. Initial SR-Convergence Time on a DR electing (broadcast) network
o Using reference topology 3, 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.
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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 SR-Convergence time when the DUT is not the desig-
nated 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. Variations in the LSA sets and other fac-
tors shoul dbe noted in the test results.
9.5. Point-to-point Link Down with Layer 2 Detection
o Using reference topology 4, 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). Disconnecting the cable on the gen-
erator 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 implementa-
tion to recognize and process a link failure.
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9.6. Broadcast Media Link Down with Layer 3 Detection
o Using reference topology 4, 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.
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 implementa-
tion to recognize and process an adjacency failure.
9.7. Designated Router Election Time on A Broadcast Network
o Using reference topology 3, configure R1 to be the desig-
nated 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 Disble 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 computation. Note this test includes the dead
interval timer at the DUT, so this time can 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.
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10. Acknowledgements
Thanks to Howard Berkowitz, (hcb@clark.net), for his encouragement
and support. Thanks also to Gurpreet Singh
(Gurpreet.Singh@SpirentCom.COM) for his help as well.
11. References
[1] Bradner, S., "Key words for use in RFCs to Indicate Requirement
Levels", RFC2119, March 1997.
[2] Moy, J., "OSPF Version 2", RFC 2328, April 1998.
[3] Bradner, S., McQuaid, J., "Benchmarking Methodology for Network
Interconnect Devices", RFC2544, March 1999.
[4] Manral, V., "OSPF Convergence Testing Terminiology and Concepts",
draft-bmwg-ospfconv-term-00.txt, My 2002
[5] draft-alaettinoglu-isis-convergence-01.txt
[6] Trotter, G., "Terminology for Forwarding Information Base (FIB)
based Router Performance", RFC3222, October 2001.
[7] Shaikh, Aman, Greenberg, Albert, "Experience in Black-Box OSPF
measurement"
>IP [8] draft-ietf-ospf-scalability-01.txt
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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
University of California
School of Engineering
1156 High Street
Santa Cruz, CA 95064
aman@soe.ucsc.edu
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