Re: Fwd: Re: [bmwg] WG Last Call: OSPF convergence benchmarking

[Scott Poretsky <[e-mail]>]

Folks,

While I think that IGP Convergence testing is very worthwhile work for the 
BMWG to undertake, these drafts do not address IGP Convergence.  These 
proposed drafts focus on LSA propagation benchmarking.  Due to the extreme 
interest in industry for IGP convergence measurements, I was working on IGP 
Convergence terminology and benchmarking methodology drafts when these 
proposed drafts were submitted.  I have provided the IGP Convergence drafts 
to Kevin and they should soon be posted.  My comments to the proposed LSA 
Propagation benchmarking drafts are below.

Scott
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Terminology
Internal Measurements and External Measurements are already defined as 
White Box and Black Box.

Point-to-Point, Broadcast, SPF, Hello Interval, and Router Dead Interval 
are already defined in IETF RFCs

Incremental-SPF is a vendor-specific feature.

Convergence is stated as " A network is termed to be converged when all of 
the devices within the network have a loop free path to each possible 
destination. "   The definition is then modified for  a single DUT as 
follow "Since we are not testing network convergence, but performance for a 
particular device within a network, however, this definition needs to be 
narrowed somewhat to fit within a single device view.  In this case, 
convergence will mean the point in time when the DUT has performed all 
actions needed to react to the change in topology represented by the test 
condition ".   This must include updating the FIB and hardware as 
externally verified with data traffic.  This draft contradicts its own 
definition by verifying convergence through measurement of only LSA 
propagation.  In fact, updating the FIB is explicitly excluded from 
measurement.

Methodology
Section 5. Overview and Scope
Control Plane measurements are not convergence measurements.  Convergence 
is benchmarked by time to reroute traffic.

Section 6. Test Conditions
Bullet 2  It cannot be assumed that there is zero delay to execute the SPF 
or  LSA processing.  Reference [5] actually _recommends_ router vendors 
implement zero delay to achieve low convergence.  The benchmarking 
methodology should allow convergence measurements to be made regardless of 
implementation.

Bullet 3  Data traffic is actually required to make a deterministic 
measurement of route convergence.
Unlisted: Number of IGP routes is a critical parameter for convergence time.

Sections 7. through 9.
The biggest problem with the methodology is that not all components for 
convergence time are measured.  Focus is on LSA Processing, which is only 1 
of 4 major components.

Route change due to cost or next-hop change is not considered.  This is the 
most common reason for route convergence.

Well -defined Convergence methodology can be applied to ISIS or OSPF.  The 
Link-State IGP does not matter.  In fact the methodology should be able for 
use to benchmark one IGP against the other given the same DUT.

All procedures meet one or more of the following flaws:
White box measurements are part of the procedure.
Time to install route (update FIB), update hardware, and reroute traffic 
are not considered.
Test case is Implementation-specific.
Test case has nothing to do with convergence - more OSPF performance test.

Applicability
The applicability document explains that convergence testing is needed using
1. White box benchmarks
2. DUT intrusive measurements
3. Knowledge of DUT implementation
4. Absence of traffic results in impractical benchmarks.  Convergence time 
is benchmarked by traffic loss.
1 through 3 violate basic test methodology requirements.  4 makes invalid 
convergence tests.
This work is less about convergence benchmarking and more about LSA 
propagation benchmarking.


>>>>>At 08:42 PM 2/7/03 -0500, you wrote:
>>>>>
>>>>>>BMWG'ers:
>>>>>>
>>>>>>A WG Last Call period for the Internet-Drafts regarding
>>>>>>OSPF convergence benchmarking terminology, methodology, and
>>>>>>benchmark applicability:
>>>>>>
>>>>>>    <draft-ietf-bmwg-ospfconv-term-02.txt>,
>>>>>>    <draft-ietf-bmwg-ospfconv-intraarea-03.txt>,
>>>>>>    <draft-ietf-bmwg-ospfconv-applicability-01.txt>
>>>>>>
>>>>>>will be open from 7 February 2003 until 28 February 2003.
>>>>>>
>>>>>>Please weigh in on whether or not you feel each individual draft
>>>>>>should not be given to the Area Directors for consideration in 
>>>>>>progressing the draft to an Informational RFC.  Send your comments
>>>>>>to this list or [e-mail].
>>>>>>
>>>>>>
>>>>>>URLs for the Internet-Drafts are:
>>>>>>
>>>>>>http://www.ietf.org/internet-drafts/draft-ietf-bmwg-ospfconv-term-02.txt
>>>>>>http://www.ietf.org/internet-drafts/draft-ietf-bmwg-ospfconv-intraarea-03.txt 
>>>>>>
>>>>>>http://www.ietf.org/internet-drafts/draft-ietf-bmwg-ospfconv-applicability-01.txt 
>>>>>>
>>>>>>
>>>>>>-Kevin
>>>>>>
>>>>>>
>>>>>>_______________________________________________
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