Re: [Lsr] Doubt regarding A bit set/clear

[Gurusiddesh Nidasesi <[e-mail]>]

Hi Les,

Thank you very much for your response.
On top of your response, I have a few more queries. Please find them below.

1. For Min/Max Unidirectional Link Delay Sub-TLV, there is only one *A-bit.*


     0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |   Type        |     Length    |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |A| RESERVED    |                   Min Delay                   |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |   RESERVED    |                   Max Delay                   |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


Does this mean A-bit is applicable only for Min-delay?

IF not, then should we maintain 2 different maximum threshold and
reuse thresholds?

And if both min-delay and max-delay values fall below reuse threshold
we have clear A-bit.


Will below example follow the RFC?
min-delay reuse threshold : 50 usec
min-delay maximum threshold : 100 usec

max-delay reuse threshold : 200 usec
max-delay maximum threshold : 300 usec
*1st measured value:*

min-delay: 110 usec

max-delay: 190 usec


conclusion: Set A bit. (As min-delay value has exceeded max-threshold value?)

*2nd measured value :*

min-delay: 40 usec

max-delay: 320 usec

conclusion : Do nothing (Maintain pervious state of A bit as max-delay
value has exceeded max-threshold value?)

*3rd measured value :*

min-delay: 40 usec

max-delay: 150 usec

conclusion : Clear A bit (As both min-delay and max-delay values are
falling below resue threshold?)


Thanks & Regards,

Gurusiddesh V N



On Fri, Apr 23, 2021 at 4:51 PM Les Ginsberg (ginsberg) <[e-mail]>
wrote:

> Gurusiddesh –
>
>
>
> The short answer to all your questions is “yes”.
>
> More inline.
>
>
>
> *From:* Gurusiddesh Nidasesi <[e-mail]>
> *Sent:* Thursday, April 22, 2021 10:33 PM
> *To:* Acee Lindem (acee) <[e-mail]>
> *Cc:* [e-mail]; [e-mail]; [e-mail]; Les
> Ginsberg (ginsberg) <[e-mail]>; Dona Maria John <
> [e-mail]>; Vikram Agrawal <[e-mail]>;
> Mahalakshmi Kumar <[e-mail]>
> *Subject:* Re: [Lsr] Doubt regarding A bit set/clear
>
>
>
> Hi All.
>
>
>
> *Gentle Reminder!*
>
>
>
> Regards,
>
> Gurusiddesh V N
>
>
>
> On Mon, Apr 19, 2021 at 6:54 PM Acee Lindem (acee) <[e-mail]> wrote:
>
> Gurusiddesh,
>
>
>
> I’ll defer to the RFC authors on your question. However, please refrain
> from referring to bits as being “unset”. They are set or clear.
>
>
>
> Thanks,
>
> Acee
>
>
>
> *From: *Lsr <[e-mail]> on behalf of Gurusiddesh Nidasesi <
> [e-mail]>
> *Date: *Monday, April 19, 2021 at 6:13 AM
> *To: *"[e-mail]" <[e-mail]>
> *Cc: *Spencer Giacalone <[e-mail]>, Stefano Previdi <
> [e-mail]>, "Les Ginsberg (ginsberg)" <[e-mail]>,
> Dona Maria John <[e-mail]>, Vikram Agrawal <
> [e-mail]>, Mahalakshmi Kumar <
> [e-mail]>
> *Subject: *[Lsr] Doubt regarding A bit set/unset
>
>
>
> Hi All,
>
>
>
> I had a query regarding setting/unsetting A bit.
>
>
>
> https://tools.ietf.org/html/rfc8570#section-4.1 states that
>
> A bit:  This field represents the Anomalous (A) bit.  The A bit is
>
>       set when the measured value of this parameter exceeds its
>
>       configured maximum threshold.  The A bit is cleared when the
>
>       measured value falls below its configured reuse threshold.  If the
>
>       A bit is cleared, the sub-TLV represents steady-state link
>
>       performance.
>
>
>
> So does it mean we have to have two configurations one for reuse and another for maximum threshold?
>
> *[Les:] Yes. The goal is to prevent altering the advertisement due to small oscillations of the advertisement. If you had a single value then if the measured value bounced between (for example) +1/-1 of the threshold) the advertisement of the A-bit would change rapidly – this is undesirable.*
>
> *So the max threshold triggers setting of the A-bit and the reuse threshold triggers clearing of the bit. The reuse threshold provides some confidence that the measurement has stabilized below the maximum anomalous threshold.*
>
>
>
>
>
> Will below example follow the RFC?
>
> reuse threshold : 50 usec
>
> maximum threshold : 100 usec
>
> 1st measured value : 110 usec
>
> conclusion: Set A bit.
>
>
>
> 2nd measured value : 75 usec
>
> conclusion : Do nothing (Maintain pervious state of A bit as the value is less than reuse or greater than threshold)
>
>
>
> 3rd measurement value : 30 usec
>
> conclusion: Unset A bit.
>
>
>
> *[Les:] Yes this conforms to specified behavior.*
>
>
>
>  If we have to have two configuration for threshold to set/unset A bit, will they be different from the threshold that we use for advertisements?
>
> *[Les:] **Yes . ** This is clearly stated in Section 5:*
>
>
>
> *“4.  For sub-TLVs that include an A bit, an additional threshold*
>
> *       SHOULD be included corresponding to the threshold for which the*
>
> *       performance is considered anomalous (and sub-TLVs with the A bit*
>
> *       are sent)…”*
>
> *   Les*
>
>
>
>
>
>
>
> Regards,
>
> Gurusiddesh V N
>
>
> .
>
>
>
>
> --
>
> Thanks,
>
> Gurusiddesh V N
>
>
> .
>


-- 
Thanks,
Gurusiddesh V N

-- 
.