Re: [bmwg] Comment on meth-18.

["McLendon, John" <[e-mail]>]

Hi Kris,
I'm still not sure what "discard" traffic means in terms of a test
device.
If the test device is monitoring both ports simultaneously (and all of
the testers I am knowledgeable about are capable of this), then my
understanding of the test scenario is that the test device either
detects/causes the switchover, captures the time of the Convergence
Event Instant onset, and can then apply the equation once full
convergence occurs. 

If this is correct, then nothing needs to be said about traffic received
by the tester on the Preferred Egress Interface unless one wishes to
measure the delta between the onset of the Convergence Event Instant and
the end of the Convergence Event, i.e. one wants to measure the time
between first packet loss and all traffic stopping on the Preferred
Egress Interface, i.e. the Ta/Tb/Ta'/Tb'/Ta"/Tb" timestamps in Figure 6.
In this case, one might want to state that the tester collects stats on
the both interfaces for the entire test, altho' this is implicit in the
equations and in Figure 6.

I also have one other comment - the current measurement period is
reported in seconds. The test devices I am aware of can capture the
timestamps with millisecond accuracy (presuming there is a minimum
transmission rate of at least two packets per millisecond for each
route). One might want to put in a MAY for this.

Make sense?
J...

-----Original Message-----
From: Kris Michielsen [mailto:[e-mail]] 
Sent: Friday, July 17, 2009 11:46 AM
To: McLendon, John; 'Al Morton'; [e-mail]
Subject: RE: [bmwg] Comment on meth-18.

John,

Thanks for reviewing the draft!

What do you think of the following suggestion?
OLD:
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.

NEW:
For Convergence Events caused by the Tester, such as an IGP cost change,
the Tester may start to discard all traffic received from
the Preferred Egress Interface at the Convergence Event Instant, or may
be able to separately observe packets received from the
Preferred Egress Interface prior to the Convergence Event Instant, to
achieve the same result.

Thanks,
Kris

> -----Original Message-----
> From: [e-mail] [mailto:[e-mail]] On 
> Behalf Of McLendon, John
> Sent: 16 July 2009 00:00
> To: Al Morton; [e-mail]
> Subject: [bmwg] Comment on meth-18.
> 
> Hi all,
> I have a comment on the following statement in Sec 4, top of pp. 9, in
> meth-18:
> 
> "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."
> 
> The word "drop" implies that the test device forwards or 
> drops traffic.
> In my experience, test devices neither forward or drop 
> traffic. They may generate or analyze traffic, but a test 
> device dropping traffic doesn't seem helpful to the desired 
> measurement. Many test devices can bring a link down at the 
> physical layer.
> 
> J...
> 
> 
> 
> -----Original Message-----
> From: [e-mail] [mailto:[e-mail]] On 
> Behalf Of Al Morton
> Sent: Wednesday, July 15, 2009 3:48 PM
> To: [e-mail]
> Subject: Re: [bmwg] WGLC: draft-ietf-bmwg-igp-dataplane drafts
> 
> Comments on meth-18, all nits,
> Al (mostly as participant)
> 
> At 01:44 PM 7/14/2009, Al Morton wrote:
> >...This message begins a Last call on the IGP-Dataplane Convergence 
> >Time Benchmarking drafts.
> >
> >http://tools.ietf.org/html/draft-ietf-bmwg-igp-dataplane-conv-term-18
> >http://tools.ietf.org/html/draft-ietf-bmwg-igp-dataplane-conv-meth-18
> >http://tools.ietf.org/html/draft-ietf-bmwg-igp-dataplane-conv-app-17
> >
> >The Last Call will end on July 31, 2009.
> 
> 
> Section 4, top of page 10,
> s/At least one condition need to /At least one condition needs to /
> 
> 
> 5.7.  Measurement Accuracy
> ...  When packet jitter is much less than the convergence
>     time, it is a negligible source of error and therefor it 
> will be s/therefor/therefore/
> 
> 5.9 Tester Capabilities
> Add "Also see section 6 for method-specific capabilities."
> 
> 6.1.3.  Measurement Accuracy
> 
>     TBD
> (can't leave this TBD, if there's no obvious material, delete 
> section ?)
> 
> 
> Section 7, Reporting Format
> 
>          Maximum Packet Delay Threshold      seconds
> this is called "Forwarding Delay Threshold" in the term doc, right?
> pick one for both...
> 
> Section 9, same as terms, use the standard BMWG paragraphs...
> 
> 
>     
> 
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