Subject: [IPFIX] Semantic and structured data - summary

From: Benoit Claise <[email-masked]>
Date: Sun, 21 Mar 2010 17:52:51 -0700

Dear all,

Thanks for the lively discussion on the mailing list.
Summarizing all the thoughts, below is what we believe the consensus is 
regarding the semantic. This should also help the others to give their views
The authors goal is get the agreement by the end of the WG, so that we 
can create a new draft version. So please express your views, either on 
the mailing list, or during the WG meeting.

- completely ignoring the semantic is not an option
- the solution is for the structured data only, so the semantic of the 
IEs within a structured data
- not change to RFC5101.
- add a semantic field in the 3 list types.

     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0|               Field ID    |       Element Length            |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Semantic  |             BasicList Content ...                 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|                           ...                                 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

- the Semantic is a single list, as opposed to a bit vector
- the required semantics are:

	0x00: undefined (default)
	0x01: allOf
	0x02: oneOrMoreOf
	0x03: exactlyOneOf
	0x04: noneOf
	0x05: ordered

     An example of ORDERED is the BGP AS-PATH 10 20 30 40 {50,60}
     (basicList, ORDERED, (basicList, ORDERED, AS10,AS20,AS30,AS40), 
(basicList, exactlyOneOf, AS50, AS60))

     Open issue:  RANGE. Required by Gerhard, but is is in scope for 
this draft?

- an IANA registry is required, to have an extensible solution, exactly 
like for the "MPLS label type" registry.
- no "semanticless" versions of the IPFIX structured data types.
- A few statements are required.
     * "semantic interpretations of recieved Data Records at or beyond 
the CP remain explicitly undefined, unless that data is transmitted 
using this extension with explicit semantic information" (or something 
like it) reduces the scope for confusion.
     * So in Structured Data we should have a statement as well that 
semantically meaningless combinations are legal, and up to the CP to 
interpret.

Example: an aggregated observation point, composed of multiple template 
records
template 1: exporterIPaddress
template 2: exporterIPaddress, basicList of interfaces
     template 3: exporterIPaddress, LC
Those three templates are linked with the semantic "exactlyOneOf"

I hope this summary helps.

Regards, Benoit.