Re: [Lsr] Flow Control Discussion for IS-IS Flooding Speed

[Robert Raszuk <[e-mail]>]

Hi Les,

Yes this "small delay" of ACK aggregation is something which I am a bit
worried here from SNPs sender side.

Now as indeed draft mentioned prioritizing SNPs on reception let me
indicate that some platforms I have not so long ago dealt with do not even
prioritize any IGP packet over other packets at neither ingress LC nor
queue to RE/RP. If that channel takes 100s of ms within the box I am
afraid all bets for flooding improvement are off.

Thx
R,.


On Wed, Feb 19, 2020 at 6:48 PM Les Ginsberg (ginsberg) <[e-mail]>
wrote:

> Robert –
>
>
>
> Thanx for your input.
>
>
>
> Note that one of the suggestions in
> https://datatracker.ietf.org/doc/draft-ginsberg-lsr-isis-flooding-scale/
>  is to prioritize the reception of SNPs over LSPs so that we are less
> likely to drop ACKs.
>
> It is not clear to me why you think SNP generation would be an issue.
>
> Once a received LSP is processed one of the outputs is to set a per
> interface flag indicating that an ACK (PSNP) needs to be sent (SSN flag).
> Implementations usually implement some small delay so that multiple ACKs
> can be sent in a single PSNP – but I do not see why this should be viewed
> as a bottleneck.
>
>
>
> If your concern is that we need to emphasize the importance of sending
> timely ACKs, I think we could look at text that makes that point.
>
>
>
>    Les
>
>
>
>
>
> *From:* Lsr <[e-mail]> *On Behalf Of * Robert Raszuk
> *Sent:* Wednesday, February 19, 2020 1:07 AM
> *To:* Les Ginsberg (ginsberg) <[e-mail]>
> *Cc:* [e-mail]
> *Subject:* Re: [Lsr] Flow Control Discussion for IS-IS Flooding Speed
>
>
>
> Hi Les & all,
>
>
>
> Watching this discussion I would like to state that IMO going with
> transmitter based rate limiting (I would not call it flow control) is much
> easier option to deploy and operate. It also has no dependency across other
> side of p2p adj which is a very important factor. The only issue here is if
> generation of [P|C]SNPs is fast enough.
>
>
>
> Receiver based flow control is simple in flow theory however I have a
> feeling that if we are to go that path we would be much better to actually
> run ISIS flooding over DC-TCP and avoid reinventing the wheel.
>
>
>
> Thx,
>
> Robert.
>
>