Re: ISCSI: Urgent Flag requirement violates TCP.

[Glen Turner <glen.turner@aarnet.edu.au>]

Matt Wakeley wrote:
> 
> Nope.  Machines today using "off the shelf" stacks utilizing 1Gbps ethernet max out the CPU
> running the TCP/IP stack, with no processing power left over for doing any work.  Machines
> will not be able to fully utilize the new 10Gbps links if the TCP/IP processing is not
> offloaded out of the main kernel.

But that's an argument for iSCSI *not* using TCP services beyond the
socket API.  To use such services the general purpose
computer running TCP/IP offload would then need to change the
code in the operating system *and* the code in the ethernet adapter.

For commodity hardware you then need support from multiple
manufacturers to get a computer that will run a complaint
iSCSI client.  This is inviting maintenance issues (eg:
need to install Windoze 2002 to fix security issue, but
the driver for the particular ethernet card doesn't
work with Win2002, and you can't just use any off-the-shelf
TCP-offload card becuase you need iSCSI-socket support).

I trying not to harp on about this, but it seems to me that
people haven't thought out the software options at the client
end in the same detail that they appear to have put into
the target end.

My feeling is that if the client can't use off-the-shelf
gear then iSCSI is only going to displace Fiber Channel
and will not become a widespread network service.  For
example, ISPs attempting to add value to their service
will need to find another mechanism to offer a storage
and backup service to their customers, whereas iSCSI
could be an ideal candidate for that application.

Best regards,
Glen