Subject: [midcom] Re: draft-aoun-midcom-cops-01.txt

From: "Joel M. Halpern" <[email-masked]>
Date: Tue, 23 Apr 2002 10:53:05 -0400

A few comments on this draft:

The first thing that struck me is that the draft was not clear as to 
whether it was discussing COPS or COPS-PR.  While these are closely 
related, fom a practical point of view they are different, and it would 
help the reader if the assumption in the comparison was a specific one of 
the two or both.  Given that operations are driven by the midcom agent 
which is a COPS PDP, I conclude that you primarily intended COPS-PR.

The second thing that struck me is that in several places the document 
suggests that one could instantiate multiple PEPs to address the 
interaction with multiple managers (PDPs).  The document states that 
requirement 2.1.3 is fully met by this mechanism.  The best way I can say 
this is that such a statement assumes facts not in evidence.  The rules for 
COPs PEPs specifically require non-overlapping domains of 
responsibility.  In fact, this partitioning of manager responsibility is 
one of the biggest differences between COPS-PR and SNMP.  If you see a way 
to bend things to make it work for this, significantly more clarity on how 
to do so is needed for tose a little more removed to evaluate the comparisons.

Some might feel that my comment above is asking for too much from a 
comparison document.  I feel it is reasonable to ask that ways in which the 
protocol can be bent to meet the requirements be spelled out in more detail 
in the evaluation than those ways which are a natural fit for the protocol, 
such as the representation of actions and properties of requests.

Additionally, the description of the handling of aggregation seems weak.  I 
actually think COPS can address the midcom requirement (2.2.3), but the use 
of hierarchy is unlikely to be the way to do so.  Hierarchical structure is 
done a priori when the PIBs are defined.  Aggregations are likely t be 
needed by specific applications making use of the common midcom 
services.  We should not need to define new PIBs in order for agents to 
make new collections of requests if the elements they need are present.

Yours,
Joel M. Halpern

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