Subject: [ipfix-protocol] draft-ietf-ipfix-protocol-11.txt: 6.2 Reduced Size Encoding of Integer Types

From: "STEPHAN Emile RD-CORE-LAN" <[email-masked]>
Date: Thu, 7 Apr 2005 12:09:33 +0200

Dear Benoit,

This section says that an exporter MAY use shorter IE length than in the
info model but does not clearly say that in this case it is mandatory to
declare these length in the template.

I propose to replace the beginning of this section with:

"Information Elements containing integer types in the information 
model MAY be encoded using fewer octets than those implied by their 
type in the information model definition [IPFIX-INFO], in this case the
exporter MUST indicate these lengths in the template ...

Regards
Emile

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From: Stewart Bryant <[email-masked]>
Date: Thu, 07 Apr 2005 12:15:08 +0100

> declare these length in the template.

That is already stated in section 3.2

"Field Length
     The length of the corresponding encoded Information Element,
     in octets.  Refer to [IPFIX-INFO].  The field length may be
     smaller than the definition in [IPFIX-INFO] if reduced size
     encoding is used (see section 7.2)."

> exporter MUST indicate these lengths in the template ...

I don't think that your added text "in this case the
exporter MUST indicate these lengths in the template"

is needed since you have to send exactly the number of octets
that you declared in the template.

BTW - the reduction would also apply to a fixed length string
object, say a name, that might be defined as an IE of max length
X (to tell the collector DB the max size it needs to store)
but which the exporter knew woud only ever take Y<X to describe.
We should therefore increase the scope to include any
primative type where the collector can figure out the semantics
of a reduced size export.

Regards

Stewart