Subject: [ipfix-protocol] padding and NUL characters

From: Benoit Claise <[email-masked]>
Date: Tue, 06 Dec 2005 15:45:24 +0100

Dear all,

I realized that [IPFIX-PROTO] specifies that:
    In case of fixed length Information Element, if padding is required, 
padding MUST be composed of NUL character(s).

However, we don't mandate NUL character(s) if padding is used with a 
variable length information element.
I would like to propose the modification of the sentence to:
    In case of fixed length or variable length Information Element, if 
padding is required, padding MUST be composed of NUL character(s).

Any objections?

Regards, Benoit.

---

From: Paul Aitken <[email-masked]>
Date: Tue, 06 Dec 2005 20:22:27 +0000

Benoit,

> padding is required, padding MUST be composed of NUL character(s).

I would eliminate naming the specific instances when it must be used, 
and simply say:

"If padding is required, it MUST be composed of NUL character(s)."

That's what 3.3.1 (almost) says:

        Padding
           The Exporting Process MAY insert some padding octets, so that
           the subsequent Set starts at an aligned boundary.  Padding
           MUST be composed of zero (0) octets.

-- 
Paul Aitken
Cisco Systems Ltd, Edinburgh, Scotland.

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---

From: Benoit Claise <[email-masked]>
Date: Thu, 08 Dec 2005 09:14:45 +0100

Paul Aitken wrote:
>>     In case of fixed length Information Element, if padding is 
>> required, padding MUST be composed of NUL character(s).
>>
>>     In case of fixed length or variable length Information Element, 
>> if padding is required, padding MUST be composed of NUL character(s).
>>
>> Any objections?
>
Ok. What I have now is:
- Padding

The Exporting Process MAY insert some padding octets, so that the 
subsequent Set starts at an aligned boundary.  For security reasons, the 
value of any padding octet MUST be composed of the NUL character.  ...

- no notion of padding in the section 6.1.5 "string and octetarray"

I think that makes more sense.

Regards, Benoit.

---

From: Stewart Bryant <[email-masked]>
Date: Thu, 08 Dec 2005 17:54:15 +0000

Benoit Claise wrote:

> subsequent Set starts at an aligned boundary.  For security reasons, 
> the value of any padding octet MUST be composed of the NUL character.  ...
>
I think that "octets with the value zero" is more precise than
NUL characters. The length of a character is not defined
and technically may include parity :)

- Stewart