Re: iSCSI: DLB's Comment on SCSI Port Names

["Jim Hafner" <hafner@almaden.ibm.com>]

David,

You wrote: 

>[T.9] 2.4.2  SCSI Architecture Model
>
>  The SCSI Port Name is mandatory in iSCSI. When used in SCSI
>  parameter data, the SCSI port name MUST be encoded as:
>  - The iSCSI Name in UTF-8 format, followed by
>  - a comma separator (1 byte), followed by
>  - the ASCII character 'i' (for SCSI Initiator Port) or the 
>    ASCII character 't' (for SCSI Target Port), followed by
>  - a comma separator (1 byte), followed by
>  - zero to 3 null pad bytes so that the complete format is a
>    multiple of four bytes long, followed by
>  - the 6byte value of the ISID (for SCSI initiator port) or the
>    2byte value of the portal group tag (for SCSI target port) in 
>    network byte order (BigEndian).

> That's a peculiar format with padding nulls in the middle and
> a number concatenated after the padding - for example, it can't
> be passed in iSCSI login without format conversion.  How about
> converting the number to 4 or 12 bytes of hex (ASCII characters)
> and moving the padding to the end so the result is actually a
> string, and excluding the padding from the definition of the name?
> This will increase the maximum length of port names, but produce
> names that are easier to deal with.

Admittedly that's an odd format, however here was the reason for this layout.
1) it's not used directly in iSCSI "Text" strings; it's intended to be a description of how this information is packed into a byte array for representation in "SCSI parameter data" (as it says!) -- that is, it's NEVER "passed in iSCSI login" (in this form).
2) the padding after the string was to force the binary values of the ISID or PGT to be better word aligned and can be more easily extracted as a value direct from the byte array without conversion.

What do you think?

Jim Hafner