Subject: ips : padding of ahs & data segment.

From: Santosh Rao <[email-masked]>
Date: Tue, 23 Oct 2001 11:00:08 -0700

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 : [email-masked]
Phone : 408-447-3751
##################################

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From: "Barry Reinhold" <[email-masked]>
Date: Tue, 23 Oct 2001 14:13:27 -0400

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: [email-masked] [mailto:[email-masked]]On Behalf Of
>Santosh Rao
>Sent: Tuesday, October 23, 2001 2:00 PM
>To: IPS Reflector
>Subject: ips : padding of ahs & data segment.
>
>
>All,
>

---

From: Santosh Rao <[email-masked]>
Date: Tue, 23 Oct 2001 13:55:41 -0700

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