Re: [Dime] Benoit Claise's No Objection on draft-ietf-dime-drmp-05: (with COMMENT)

Steve Donovan <srdonovan@usdonovans.com> Tue, 10 May 2016 21:16 UTC

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To: Benoit Claise <bclaise@cisco.com>, Ben Campbell <ben@nostrum.com>
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From: Steve Donovan <srdonovan@usdonovans.com>
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Date: Tue, 10 May 2016 16:16:18 -0500
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Subject: Re: [Dime] Benoit Claise's No Objection on draft-ietf-dime-drmp-05: (with COMMENT)
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Benoit,

Please see my comments inline.

Regards,

Steve

On 5/8/16 7:09 AM, Benoit Claise wrote:
> Ben,
>> I will jump in on one point, since this is related to the discussion 
>> on whether nodes need a common approach to selecting/interpreting 
>> priority values:
>>
>> On 4 May 2016, at 12:02, Benoit Claise wrote:
>>
>>>
>>> -
>>>
>>>  1.  Request sender - The sender of a request, be it a Diameter Client
>>>        or a Diameter Server, determines the relative priority of the
>>>        request and includes that priority information in the request.
>>>
>>> Question: what is the risk of DMRP ending up as the DSCP, i.e.
>>> Every end point changes the value to best service, and in the end, it's
>>> useless, and uniquely set by the operator.
>>
>> I think there's a trusted network assumption here, which would 
>> include an assumption that trusted clients do not intentionally game 
>> the system. (in contrast with _accidentally_ gaming the system by 
>> using a different scheme to set priority values.)
>>
>> However, I think that this sort of assumption should be explicitly 
>> mentioned. 
> I believe so.
>> IIRC, DOIC included some guidance about crossing trust boundaries; 
>> perhaps DRMP should do the same.
> Yes.
> That makes me think. I wonder how the following two statements are 
> interoperable?
>
>    Diameter nodes MUST have a default priority to apply to transactions
>    that do not have an explicit priority set in the DRMP AVP.
>
>    Diameter nodes SHOULD use the PRIORITY_10 priority as this default
>    value.
>
>
> Shouldn't the last SHOULD be a MUST?
SRD> The reason it is a SHOULD is to allow for an operator to define a 
priority scheme with a different value, much as you outline below.
>
> Let me explain: a Diameter node wants to send Diameter messages with 
> priority above average, so PRIORITY = 12 (because his default is 10). 
> Along the path (potentially crossing a boundary), a Diameter node 
> doesn't support the DRMP AVP. The next node, which does, sets his 
> default priority. The default priority on that node has been 
> configured as 13. And now, my Diameter messages will be treated as 
> below average.
> Do I miss anything?
SRD> Yes, as described, this would be an issue.  This is one of the 
reasons that the DISCUSS threads have focused on the need to emphasize 
that this mechanism only works if a consistent priority scheme is 
applied to all messages and that it only works within a trusted 
environment.  This implies that priority values received from other 
Diameter networks likely can't be trusted.

SRD> It may be necessary to add a requirement that the priority value 
MUST be the same for all nodes within the Diameter network using a 
defined priority scheme.
>
> Regards, Benoit
>
>>
>> (And I guess that does make it a bit like DSCP ;-)  )
>>
>> Ben.
>> .
>>
>