Re: [tsvwg] Secdir last call review of draft-ietf-tsvwg-le-phb-08

"Bless, Roland (TM)" <roland.bless@kit.edu> Fri, 15 February 2019 08:43 UTC

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To: Kyle Rose <krose@krose.org>
Cc: IETF SecDir <secdir@ietf.org>, IETF Discussion Mailing List <ietf@ietf.org>, tsvwg@ietf.org
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From: "Bless, Roland (TM)" <roland.bless@kit.edu>
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Organization: Institute of Telematics, Karlsruhe Institute of Technology
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Date: Fri, 15 Feb 2019 09:43:14 +0100
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Subject: Re: [tsvwg] Secdir last call review of draft-ietf-tsvwg-le-phb-08
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Hi Kyle,

see inline, please.

Am 14.02.19 um 21:22 schrieb Kyle Rose:
>> > and/or behavior. The reason the privacy impact is unremarkable is
> that it is
> 
>     > highly likely the case that such traffic is already classifiable
>     as unimportant
>     > via the sort of traffic analysis that troubles privacy advocates, when
>     > considering the endpoint, payload length, pacing, etc.
> 
>     The LE DSCP marking does not say that this traffic is "unimportant",
>     it basically classifies the traffic as being of low priority/urgency.
> 
> 
> Right, "unimportant" is the wrong word. I meant "uninteresting" from the
> perspective of an observer interested in learning about the user behind
> some traffic (e.g., a state level actor). Software downloads, for
> instance, are less likely to be interesting for surveillance purposes
> than general web traffic, which is not going to be LE. The net effect of
> marking some packets LE is to reduce the chaff/noise from which
> wheat/signal can be extracted.

Thank you for this explanation, now I got your point!

>     I think that the statement "However, this disclosed information is only
>     useful if some form of identification happened at the same time" is
>     still correct, but probably needs a bit more explanation that this
>     is often given due to the IP addresses in the packet. Compared to the
>     plethora of traffic analysis possibilities and general privacy threats
>     (e.g., see RFC 6973) the impact of disclosed information by the LE DSCP
>     is likely negligible in most cases. So my suggestion is the following
>     text:
> 
>     "However, this disclosed information is only useful if some form of
>     identification happened at the same time, which is often given due to
>     the presence of IP addresses in the packet. Compared to the numerous
>     traffic analysis possibilities and general privacy threats (e.g., see
>     [RFC 6973]) the impact of disclosed information by the LE DSCP is likely
>     negligible in most cases."
> 
> 
> I think the wording here is a bit awkward, and simultaneity isn't really
> the limiting factor. I might start with:
> 
> "However, this disclosed information is useful only if correlation with
> metadata (such as the user's IP address) and/or other flows reveal user
> identity. ..."

My apologies, but I'm not a native speaker, so some phrases may be
awkward indeed (I think that the RFC editor will catch the most
obvious ones). Thanks for the suggestion. I tried to rephrase
that paragraph based on the better understanding of your point
(will be in the next draft revision).

>     I agree that the multicast congestion-induced loss in LE is no worse
>     than congestion problems with multicast in general, but there is a
>     subtle difference. the multicast LE replication problem is covered in
>     section 9. Depending on the implementation replication of LE multicast
>     packets inside a node may impact other traffic in an undesired way:
>     the expectation is that LE packets only scavenge otherwise unused
>     resources. I think that this is covered by the first sentence of the
>     last paragraph in sec.9:
>        While the resource contention problem caused by multicast packet
>        replication is also true for other Diffserv PHBs, LE forwarding is
>        special, because often it is assumed that LE packets get only
>        forwarded in case of available resources at the output ports.
> 
>     So what is missing in your point of view for a better understanding?
> 
> 
> Nothing. I think I'm happy with this explanation.

Ok, great.

Regards,
 Roland