Re: [Dime] AD evaluation of draft-ietf-dime-load-06

Stephen Farrell <stephen.farrell@cs.tcd.ie> Thu, 12 January 2017 11:54 UTC

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To: Steve Donovan <srdonovan@usdonovans.com>, dime@ietf.org
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Subject: Re: [Dime] AD evaluation of draft-ietf-dime-load-06
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Hiya,

Just one thing below I'd like to figure out before
IETF LC...

On 09/01/17 22:28, Steve Donovan wrote:
> Stephen,
> 
> Thanks for the review and for the ping.  Comments below.
> 
> Regards,
> 
> Steve
> 
> On 1/6/17 10:33 AM, Stephen Farrell wrote:
>> Just bumping this, post holidays. I believe the
>> ball is not in my court for this one:-)
>>
>> Cheers,
>> S.
>>
>> On 16/12/16 17:38, Stephen Farrell wrote:
>>> Hiya,
>>>
>>> Thanks for getting this stuff progressed. I've done my
>>> AD evaluation and have a few questions I'd like to ask
>>> before starting IETF last call. Those are below along
>>> with some more nitty comments that can be handled now or
>>> later as the authors/WG prefer.
>>>
>>> Cheers,
>>> S.
>>>
>>> Things to chat about before starting IETF LC:
>>> ---------------------------------------------
>>>
>>> (1) Is "server selection" sufficiently clear? Where is
>>> that defined? I was a bit confused as to what this means
>>> that is not next-hop selection.
> SRD> Server selection is touched on in RFC7638 (DOIC) and the concept
> carries over to Load.  It refers to selection of the specific server
> instance that will be handling the request.  This is according to the
> Diameter Client, Server model.  I think it is well understood what is
> meant by those who understand Diameter and would be implementing this
> spec.  We can, if needed, add some definition. That would have been best
> do be in the DOIC RFC but it can go here if needed.

Ok, let's handle that as an IETF LC comment. If others
think a definition would be good you can add it later.
If it's just me, don't bother.

>>>
>>> (2) PEER reports that are first received at a
>>> non-supporting node will be left in place and will reach
>>> the destination of the message. If that destination is in a
>>> different domain then that leaks some internal structure
>>> (the SourceID) to outsiders. Is that desirable?  Why not
>>> have the first node that does support this AVP delete the
>>> PEER report even if the node that added the PEER report is
>>> not a peer of this node? (Note: I see this risk is ack'd
>>> in section 8, I'm asking if we can avoid it almost
>>> entirely by removing PEER reports that are useless.)
> SRD> There is no formal mechanism in place in Diameter to do "topology
> hiding".  There are many other places where topology information can
> leak, so it isn't an issue specific to Load.  It is addressed today
> through proprietary implementations.

Sure, that's not a good reason to make it harder though.
But see below...

> 
> SRD> Having a node that does not support would go against the Diameter
> extensibility strategy.  Nodes that don't understand an AVP are required
> to pass it on.  Nodes that do support the mechanism and see a Load
> report of type peer that isn't of type peer are supposed to remove it.

I don't understand what " a Load report of type peer that
isn't of type peer" can mean.

> Doing anything other than this would require a change to the base
> Diameter specification.

Either I'm mis-remembering the draft or we're talking at
cross purposes. My reading was that nodes that do support
the mechanism could delete a peer report that actually
comes via a node that does not support the mechanism. Am
I wrong? If so maybe there's a clarity issue. If not, I
don't see why that makes sense.

Cheers,
S.

PS: The rest below is fine to handle later as you suggest.

>>>
>>> (3) This spec is a bit like RFC7944 (DRMP) in that it
>>> defines some but not all of the things one needs to end up
>>> with a workable system. That aspect of DRMP caused some
>>> discussion during IESG evaluation. Have the authors of
>>> this reviewed that discussion to see if we can avoid any
>>> likely iterations being needed at that point? I'm hoping
>>> that Steve, as an author of both, won't find this too
>>> hard to do:-) If that's been done, great. If not, please
>>> consider if there's any additional explanatory material
>>> that could be added that might help us not to have to
>>> iterate to discuss the same kinds of concern.
> SRD> I'll go back and review that discussion and see if there is
> something that needs to be added.  I'm hoping that the fact that we made
> it through the discussion with DRMP will make it easier to do so with
> Load (and maybe agent overload).  I'm doubtful that we can fully
> inoculate the draft from some of this level of discussion as we are
> dealing with Diameter here.
>>>
>>> nits (fine to be considered last call comments):
>>> -------------------------------------------------
> SRD> I'll deal with these as part of last call.
>>>
>>> abstract: maybe put the 1st sentence last? that might read
>>> better
>>>
>>> 4.1: the "opinion of the authors" isn't really of interest
>>> at this point - is this also the opinion of the WG? (I
>>> assume it is)
>>>
>>> section 5 says "The load report includes a value
>>> indicating the load of the sending node relative load of
>>> the sending node, specified in a manner consistent with
>>> that defined for DNS SRV [RFC2782]." I can't parse that.
>>>
>>> - 6.2: What is a Diameter "connection?" I thought that
>>> Diameter could use UDP as well as TCP so is that really
>>> the right term? Maybe "message sender" is a better way to
>>> identify the peer?
>>>
>>> - section 8: "might require a transitive trust model" is
>>> far too coy IMO. I think you should say that DOIC and this
>>> entirely require transitive trust because we have no
>>> Diameter mechanism that allows authenticated adding and
>>> removal of AVPs as messages transit a network. (We did try
>>> develop that ages ago but it was too complex, so I'm not
>>> arguing to try again, just that we clearly ack the fact
>>> that this stuff requires transitive trust.)
>>>
>>>
>>>
>>>
>>> _______________________________________________
>>> DiME mailing list
>>> DiME@ietf.org
>>> https://www.ietf.org/mailman/listinfo/dime
>>>
>>
>>
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> 
> 
> 
> 
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