Re: ips : padding of ahs & data segment.

[Santosh Rao <santoshr@cup.hp.com>]

Julian,

I noticed that in certain other sections of the draft such as Appendix
F, the following tighter wording is used to describe the use of padding
:

"Zero to three bytes set to zero shall be appended as padding so that
the total length of the designation is a multiple of four."

I suggest that wording along the lines of the above be used in Section
3.2.2.2 & 3.2.4, in order to avoid possible mis-interpretation of the
number of pad bytes used in AHS and data segments.

Thanks,
Santosh


Barry Reinhold wrote:
> 
> Santosh,
>         I was not aware of any need to pad beyond the next word (adding 0-3
> bytes)when we were working on the format. I agree that you can read the
> standard to imply that any 4 byte boundary would be valid and the wording
> could be tightened.
> 
> >-----Original Message-----
> >From: owner-ips@ece.cmu.edu [mailto:owner-ips@ece.cmu.edu]On Behalf Of
> >Santosh Rao
> >Sent: Tuesday, October 23, 2001 2:00 PM
> >To: IPS Reflector
> >Subject: ips : padding of ahs & data segment.
> >
> >
> >All,
> >
> >Can somebody clarify what the below wording is supposed to imply :
> >
> >3.2.2.2 AHSLength
> >
> >The AHS is padded to an integer number of 4 byte words.
> >
> >3.2.4 Data Segment
> >
> >The Data Segment is also padded to an integer number of 4 byte words.
> >
> >
> >Does the above imply that there are EXACTLY 0 - 3 pad bytes so as to
> >align the AHS and data segment to the nearest 4 byte aligned boundary,
> >or can the AHS and data segment be aligned on any integer number of 4
> >byte words ??
> >
> >For ex :
> >Assume a data segment length of 41 bytes. Does the above wording imply
> >that the data segment MUST be exactly padded to a length of 44 bytes, or
> >does it allow for padding to 44, 48, 52, 56... bytes ? (multiple integer
> >of 4 byte words.)
> >
> >My interpretation is that the wording is loose and allows for the latter
> >(i.e. any multiple integer of 4 byte words.)
> >
> >However, in order for this to work, the padding must be to the next
> >highest 4 byte word boundary beyond the ahs length or data segment
> >length. i.e. The pad bytes MUST range between 0 - 3 bytes.
> >
> >I think the wording needs to be tightened to clarify this.
> >
> >Comments ?
> >
> >Thanks,
> >Santosh
> >
> >
> >--
> >##################################
> >Santosh Rao
> >Software Design Engineer,
> >HP-UX iSCSI Driver Team,
> >Hewlett Packard, Cupertino.
> >email : santoshr@cup.hp.com
> >Phone : 408-447-3751
> >##################################

-- 
##################################
Santosh Rao
Software Design Engineer,
HP-UX iSCSI Driver Team,
Hewlett Packard, Cupertino.
email : santoshr@cup.hp.com
Phone : 408-447-3751
##################################