Re: bridging issues

["Matt Wakeley" <matt_wakeley@agilent.com>]

julian_satran@il.ibm.com wrote:

<snip>

> Another bridging issue is the initiator tag-translation mechanism.
> iSCSI is requiring the initiator issue a unique tag for each task but does
> not require any structure for the tag. This way an implementer may choose
> the most efficient structure for his implementation (e.g.,
> use the address of it's control structure representing the task as a tag).
>
> FCP on the other hand demands some structure for the tag.

FCP does not demand any structure for the tag.  The only difference between FCP
and iSCSI is the FCP tag is 16 bits (the "OX_ID") and the iSCSI tag is 32
bits.  FCP does not demand how those 16 bits are used.

>
>
> A stateless bridge would want to pass the tag unchanged from initiator to
> target or translate it with a stateless rule.

well, it would be a problem to try and translate a 32 bit space (iscsi) into a
16 bit space (FCP).

>
>
> If we restrict the design space to gateways that present a "homogenous"
> view of the device conglomerate behind them (e.g., all devices are FCP)
> and we may pass this information to the initiator - then the initiator can
> use the slightly more restrictive FCP tagging mechanism.
>
> Julo

-Matt Wakeley
Agilent Technologies