Re: [Dots] Opsdir last call review of draft-ietf-dots-signal-filter-control-04

[[e-mail]]

Re-, 

Please see inline. 

Cheers,
Med

> -----Message d'origine-----
> De : Tim Chown [mailto:[e-mail]]
> Envoyé : mardi 16 juin 2020 16:57
> À : BOUCADAIR Mohamed TGI/OLN
> Cc : [e-mail]; [e-mail];
> [e-mail]; [e-mail]
> Objet : Re: Opsdir last call review of draft-ietf-dots-signal-filter-
> control-04
> 
> Hi,
> 
> Some comments on your comments in line….
> 
> > On 16 Jun 2020, at 06:51, [e-mail] wrote:
> >
> > Hi Tim,
> >
> > Thank you for the review. Much appreciated.
> >
> > A candidate version that takes into account your review is available at:
> >
> > https://github.com/boucadair/filter-control/blob/master/draft-ietf-dots-
> signal-filter-control-05.txt
> 
> [TC] what would be great is a diff to the version I reviewed.
> 

[Med] Here it is: https://github.com/boucadair/filter-control/blob/master/diff-review-Tim-Chown.pdf 

The changes includes your comments on the proposed new introduction text. 


> > Please see inline.
> >
> > Cheers,
> > Med
> >
> >> -----Message d'origine-----
> >> De : Tim Chown via Datatracker [mailto:[e-mail]]
> >> Envoyé : lundi 15 juin 2020 17:08
> >> À : [e-mail]
> >> Cc : [e-mail]; last-
> >> [e-mail]; [e-mail]
> >> Objet : Opsdir last call review of draft-ietf-dots-signal-filter-
> control-04
> >>
> >> Reviewer: Tim Chown
> >> Review result: Has Nits
> >>
> >> Hi,
> >>
> >> I have reviewed this document as part of the Operational directorate's
> >> ongoing
> >> effort to review all IETF documents being processed by the IESG.  These
> >> comments were written with the intent of improving the operational
> aspects
> >> of
> >> the IETF drafts. Comments that are not addressed in last call may be
> >> included
> >> in AD reviews during the IESG review.  Document editors and WG chairs
> >> should
> >> treat these comments just like any other last call comments.
> >>
> >> This document is one of a set of documents produced by the DDoS Open
> Threat
> >> Signalling (DOTS) working group, and builds on previously published RFCs
> >> (RFC
> >> 8782, 8783). It describes a mechanism by which the DOTS signalling
> channel
> >> defined in RFC 8782 can be used to allow a DOTS client that is under
> attack
> >> to
> >> change the filtering rules and thus the mitigation behaviour being
> applied
> >> to
> >> it via a DOTS server, even when the downstream to it may be saturated.
> >>
> >> The text is well-written with a good structure and a healthy number of
> >> examples. I would asses its current state as Ready with Nits.  The new
> >> capability seems very useful.
> >>
> >> General comments:
> >>
> >> I am not wholly clear about some terms, e.g. “idle time” seems to be
> when
> >> no
> >> mitigation is in place, but does this mean no filtering rules are
> active,
> >> or no
> >> anti-DDoS rules are active?  Or are all DOTS rules there for mitigation
> >> rather
> >> than general protection?
> >
> > [Med] Idle time refers to when there is no active mitigation. This is
> mentioned in Section 1.1:
> >
> >   A typical case is a DOTS client which configures during 'idle' time
> >   (i.e., no mitigation is active) ...
> >
> > Filtering can be activated even if no mitigation is active. This is
> controlled by the DOTS client by setting "activation-type" to "immediate".
> >
> > I updated the abstract as follows:
> >
> > OLD:
> >   Particularly, this extension allows a DOTS client to activate or de-
> >   activate existing filtering rules during a DDoS attack.  The
> >   characterization of these filtering rules is supposed to be conveyed
> >   by a DOTS client during an idle time by means of the DOTS data
> >   channel protocol.
> >
> > NEW:
> >   Particularly, this extension allows a DOTS client to activate or de-
> >   activate existing filtering rules during a DDoS attack.  The
> >   characterization of these filtering rules is supposed to be conveyed
> >   by a DOTS client during an idle time (i.e., no mitigation is active)
> >                                        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
> >   by means of the DOTS data channel protocol.
> 
> [TC] I think the problem (for me) here is I don’t understand how the client
> knows whether there is active mitigation;

[Med] Mitigations can be initiated by the client or triggered by a signal loss. In both cases, the client is aware whether a mitigation is ongoing. All these details are supposed to be covered in the base specs. That's said, and for the reader's convenience, we have now a sentence that recalls that a client sends a mitigation request. 

 does the client have a state
> stable of which filters it has requested the server to activate?

[Med] Yes. 

> 
> Is there a difference between filters being active, and mitigation being
> active? 

[Med] Yes. Mitigation is said to be active if there is a mitigation request received from the client or when a pre-configured mitigation is triggered upon signal loss. Filters can be active even if no attack is detected. 

 Are all filters mitigation against a current attack?

[Med] No. see above. 

> 
> >> If I understand correctly, this extension allows new filter rules to be
> >> added,
> >> such as rate limits, so it’s not just that the signal channel can be
> used
> >> to
> >> control (activate and deactivate) existing filters.
> >


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