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

Benoit Claise <bclaise@cisco.com> Wed, 11 May 2016 16:53 UTC

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To: Steve Donovan <srdonovan@usdonovans.com>, Ben Campbell <ben@nostrum.com>
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From: Benoit Claise <bclaise@cisco.com>
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Date: Wed, 11 May 2016 12:53:05 -0400
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Cc: draft-ietf-dime-drmp@ietf.org, dime-chairs@ietf.org, dime@ietf.org, The IESG <iesg@ietf.org>
Subject: Re: [Dime] Benoit Claise's No Objection on draft-ietf-dime-drmp-05: (with COMMENT)
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On 5/10/2016 5:16 PM, Steve Donovan wrote:
> 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. 
BC> This assumption should be spelled out.
> 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.
BC> That would help yes.

regards, B.

>>
>> Regards, Benoit
>>
>>>
>>> (And I guess that does make it a bit like DSCP ;-)  )
>>>
>>> Ben.
>>> .
>>>
>>
>
> .
>