Subject: [ipfix-info] prefix "pre" for Information Element naming convention

From: Benoit Claise <[email-masked]>
Date: Thu, 14 Jul 2005 16:54:23 +0200

Dear all,

While looking at the differences between IPFIX version 7 and 8, I 
noticed this new addition.

   o  If the 'other' side of the middlebox is located on the data path
      of a Flow before the middlebox, i.e. the middlebox observes the
      modified packets, then the names of Information Elements reporting
      the original Flow properties SHOULD have the prefix "pre", for
      example preIpDiffServeCodePoint.

Maybe I missed the justification of this change... However, I disagree 
with this addition.

If we observed the packets after packet treatment, the Information 
Element name SHOULD contain the prefix "post". This is fine, as was 
agreed upon a long time ago.
However, if we observe the packets on an observation point at the entry 
of a middlebox (so the observation point is the incoming interface of 
the middlebox), from the observation point of view, we're not supposed 
to know that we belong to a middlebox.
In this case, there is no differences whether the observation point 
belongs to a middlebox or not.

BTW, if we keep this convention, we should duplicate all the information 
elements with a prefix "pre".
A flow observed on the incoming interface of a middlebox would export 
preSourceIPv4Address, for example.
A flow observed on the incoming interface of a non-middlebox would 
export sourceIPv4Address.
 From the Collecting Process point of view, I'm not sure what 
information we gain if we receive preSourceIPv4Address instead of 
sourceIPv4Address

Note that we don't have a single information element in the draft that 
starts with "pre"
 
So I'm convinced we should remove this prefix "pre" convention.

Regards, Benoit.

--
Help        mailto:[email-masked] and say "help" in message body
Unsubscribe mailto:[email-masked] and say
"unsubscribe ipfix" in message body
Archive     http://ipfix.doit.wisc.edu/archive/