Subject: Re: [core] WG Last Call on draft-ietf-core-new-block (Congestion Control)

From: <[email-masked]>
Date: Wed, 3 Feb 2021 08:15:09 +0000

Re-,

FWIW, we significantly updated the congestion control as you can see in: https://tools.ietf.org/html/draft-ietf-core-new-block-06#section-6 

We finally added this text to point to how some parameters can be tweaked by an application: 

      Note: For the particular DOTS application, PROBING_RATE and other
      transmission parameters are negotiated between peers.  Even when
      not negotiated, the DOTS application uses customized defaults as
      discussed in Section 4.5.2 of [RFC8782].  Note that MAX_PAYLOADS,
      NON_MAX_RETRANSMIT, and NON_TIMEOUT can be negotiated between DOTS
      peers as per [I-D.bosh-dots-quick-blocks].

We believe that we addressed your initial concern, but having an ACK would be appreciated. Thanks. 

Cheers,
Jon & Med

> -----Message d'origine-----
> De : [email-masked]
> [mailto:[email-masked]]
> Envoyé : mercredi 23 décembre 2020 10:14
> À : Christian Amsüss <[email-masked]>; draft-ietf-core-new-
> [email-masked]
> Cc : [email-masked] WG ([email-masked]) <[email-masked]>; [email-masked]
> Objet : RE: [core] WG Last Call on draft-ietf-core-new-block
> (Congestion Control)
> 
> Re-,
> 
> You are completely right that the default probing-rate is to be
> increased for the DOTS case. FYI, this is why we went with the
> following in RFC8782:
> 
>       |  Given that the size of the heartbeat request cannot exceed
>       |  ('heartbeat-interval' * 'probing-rate') bytes, 'probing-
> rate'
>       |  should be set appropriately to avoid slowing down heartbeat
>       |  exchanges.  For example, 'probing-rate' may be set to 2 *
>       |  ("size of encrypted DOTS heartbeat request"/'heartbeat-
>       |  interval') or (("size of encrypted DOTS heartbeat request" +
>       |  "average size of an encrypted mitigation
> request")/'heartbeat-
>       |  interval').  Absent any explicit configuration or inability
> to
>       |  dynamically adjust 'probing-rate' values (Section 4.8.1 of
>       |  [RFC7252]), DOTS agents use 5 bytes/second as a default
>       |  'probing-rate' value.
> 
> We also allow DOTS peers to negotiate the transmission parameters
> (and probing rate) with the following as default:
> 
>    "The RECOMMENDED values of
>    transmission parameter values are 'ack-timeout' (2 seconds), 'max-
>    retransmit' (3), and 'ack-random-factor' (1.5).  In addition to
> those
>    parameters, the RECOMMENDED specific DOTS transmission parameter
>    values are 'heartbeat-interval' (30 seconds) and 'missing-hb-
> allowed'
>    (15)."
> 
> We avoided to include a pointer to these details as these are
> application-specific and that, even if the draft is motivated by the
> DOTS use case, other applications can make use of the new block
> functionality.
> 
> For NSTART, we already have the following:
> 
>   " NSTART will also need to be increased from the default
>    (1) to get faster transmission rates."
> 
> Cheers,
> Med
> 
> > -----Message d'origine-----
> > De : Christian Amsüss [mailto:[email-masked]] Envoyé :
> mercredi
> > 23 décembre 2020 06:01 À : [email-masked]
> > Cc : [email-masked] WG ([email-masked]) <[email-masked]>;
> [email-masked]
> > Objet : Re: [core] WG Last Call on draft-ietf-core-new-block
> >
> > * Also on parameters: This document is describing flow control
> stuff
> >   around a situation CoAP was not originally designed for. Wouldn't
> it
> >   make sense to include a set of parameters (PROBING_RATE,
> > MAX_LATENCY,
> >   ACK_TIMEOUT) that's suitable for the DOTS use case? I doubt that
> >   PROBING_RATE will be left to 1 byte/second for any DOTS
> application
> >   using this (for sending 10KiB in the initial 10-package
> MAX_PAYLOADS
> >   burst would mark that connection as unusable for about 3 hours if
> > they
> >   all get lost), so better give justifiable numbers here than rely
> on
> >   implemnetors to come up with unreviewed numbers or disregard
> >   PROBING_RATE altogether.
> >
> >   I don't know if it needs additional justification, but an
> increased
> >   N_START may be justifiable there.
> >

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