Re: [Lsr] New draft on Flex-Algorithm Bandwidth Constraints

Peter Psenak <ppsenak@cisco.com> Wed, 03 March 2021 10:31 UTC

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To: Robert Raszuk <robert@raszuk.net>
Cc: Tony Li <tony.li@tony.li>, Gyan Mishra <hayabusagsm@gmail.com>, DECRAENE Bruno IMT/OLN <bruno.decraene@orange.com>, Shraddha Hegde <shraddha@juniper.net>, Rajesh M <mrajesh@juniper.net>, "lsr@ietf.org" <lsr@ietf.org>, William Britto A J <bwilliam=40juniper.net@dmarc.ietf.org>
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From: Peter Psenak <ppsenak@cisco.com>
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Date: Wed, 3 Mar 2021 11:31:42 +0100
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Subject: Re: [Lsr] New draft on Flex-Algorithm Bandwidth Constraints
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On 03/03/2021 11:27, Robert Raszuk wrote:
> 
> I am not sure I follow your logic here ...
> 
> If we are already advertising "Min Unidirectional link delay" as 
> described in https://tools.ietf.org/html/draft-ietf-lsr-flex-algo-13 why 
> would we need to define it again here in this draft ?

we are not defining the metric here, we are defining the constraint that 
says what is the maximum value of that metric that can be used.

thanks,
Peter
> 
> Also does it really make sense to advertise maximum value of 
> minimum value ?
> 
> Thx,
> R.
> 
> On Wed, Mar 3, 2021 at 11:22 AM Peter Psenak <ppsenak@cisco.com 
> <mailto:ppsenak@cisco.com>> wrote:
> 
>     Robert,
> 
>     On 03/03/2021 11:10, Robert Raszuk wrote:
>      > Hey Peter,
>      >
>      >      > Authors stated: "Whether egress queueing delay is included
>     in the
>      >     link
>      >      > delay depends on the measuring mechanism."
>      >
>      >     I disagree with that statement - the Min Unidirectional Link
>     Delay is
>      >     the value that does not include the queueing delay - that's
>     why it is
>      >     called Min.
>      >
>      >
>      >
>      > But draft we are discussing here does not talk about "Min" delay.
>      > Contrary it talks about "Max"
>      >
>      > *Maximum*  Delay sub-TLV
>      >
>      > That is also I asked that very question up front.
> 
>     I'm afraid you misunderstood it. FA uses "Min Unidirectional Link
>     Delay"
>     as one of its metrics. The "Maximum Delay sub-TLV"  is used to
>     advertise
>     the maximum value of the "Min Unidirectional Link Delay" that is
>     allowed
>     for the particular FA.
> 
>     The text should be improved in that regard though, it's not obvious,
>     but
>     I believe that's what it is.
> 
>     thanks,
>     Peter
> 
>      >
>      > Thx,
>      > R.
>      >
>      >
>      >
>      >
>