Re: iSCSI : Negotiable padding, was More issues.... Digest related.

[julian_satran@il.ibm.com]

Rod,

On the wire padding is not required at all and many of us have resisted
padding up to the advent of markers.

Please do explain what will a padding option do that you can't do by
yourself in the endsystem with buffer alignment - or how can padding on the
wire stop you from getting buffer alignment all bad.

Julo

"Rod Harrison" <rod.harrison@windriver.com> on 20/04/2001 20:30:14

Please respond to "Rod Harrison" <rod.harrison@windriver.com>

To:   ips@ece.cmu.edu
cc:
Subject:  iSCSI : Negotiable padding, was More issues.... Digest related.




Julian,

     I have a request with respect to data padding. Can we make
the pad size login negotiable please? Preferably on a per
direction basis. This would allow the pad to be optimized
for a receivers specific requirements, e.g. cache line
alignment. Restricting padding to powers of 2 by specifying
the size as a power of 2 seems reasonable.

     For example:

     IPadSize=<any-power-of-two>
     TPadSize=<any-power-of-two>

     IPadSize=0
     TPadSize=2

     Would result in the initiator padding data to 4 byte
boundaries for the target, and the target inserting no pad
for the initiator.

     Also, a related question, if the pad is to remain mandatory
is it expected data will be padded if no data digests are in
use?

     - Rod

-----Original Message-----
From: owner-ips@ece.cmu.edu [mailto:owner-ips@ece.cmu.edu]On
Behalf Of
julian_satran@il.ibm.com
Sent: Friday, April 20, 2001 1:45 AM
To: ips@ece.cmu.edu
Subject: Re: iSCSI : More issues.... Digest related.




1.The padding is to the next 4 byte word boundary .
2. There is a Security - Appendix

and there is a numbering /formating error in the appendix

Julo

Santosh Rao <santoshr@cup.hp.com> on 20/04/2001 03:25:49

Please respond to Santosh Rao <santoshr@cup.hp.com>

To:   IPS Reflector <ips@ece.cmu.edu>
cc:
Subject:  iSCSI : More issues.... Digest related.




Julian & All,

2 more issues :

1) If the DataSegmentLength in the BHS excludes padding
bytes, how does
the initiator determine the location of the data digest
[which is placed
after the padded data] ?
There is no knowledge of what amount of padding is in use,
since padding
can be 4 bytes or a multiple of that quantity.


2) While on the subject of digests.....are'nt there supposed
to be
login keys to indicate the use or non-use of header and data
digests ? I
can't seem to find any such login keys in the latest revs
5.91....5.92....6.000...(?)

(Section 2.2.1 states :
"The digest types are negotiated during the login phase. ").

- Santosh
 - santoshr.vcf