RE: Keep-alive traffic (was iSCSI: more on StatRN)

["Y P Cheng" <ycheng@advansys.com>]

Glen:

For a TOE adapter to assist TCP to achieve zero-copy, we need to change the
BSD socket interface.  What we do is to split the TCP segment by sending TCP
header back and by sending the payload directly to the application software.
Therefore, the adapter must parse through the segments and identify the
boundary of the header and payload.  In doing so, I assume we can pick out
the ping.  When I said that I could generate an automatic ping-reply, I was
referring to the behavior of a 1394 adapter.  I don't know if this is
acceptable to iSCSI.

Y.P.

> -----Original Message-----
> From: owner-ips@ece.cmu.edu [mailto:owner-ips@ece.cmu.edu]On Behalf Of
> Glen Turner
> Sent: Wednesday, November 01, 2000 1:58 PM
> To: 'Ips@Ece. Cmu. Edu'
> Subject: Re: Keep-alive traffic (was iSCSI: more on StatRN)
>
>
> Y P Cheng wrote:
>
> > You are referring to TCP implementation with software.  In an
> > TCP-Offload-Engine (TOE) adapter, there is no queue.  Every
> incoming frame,
> > including the ping is served at the speed of the wire...
>
> The BSD socket API won't allow this sort of look-ahead for a
> standard TCP segment.
>
> So for iSCSI Ping and Ping Response to be worthwhile to allow
> software implementations to implement fail-over schemes, the Ping
> and Ping Response should use TCP's Urgent feature to allow
> out-of-order delivery of the Pings to the socket held open by the
> iSCSI target?
>
> So maybe we need to add:
>
>    Ping and Ping Response SHOULD be marked by TCP as urgent data [RFC793].
>
> Do we need to allow for that BSD4.2 mis-interpretation of the TCP
> urgent pointer?  Does iSCSI have a Null command that we can require
> as padding before the Ping commands?
>
> --
>  Glen Turner                                 Network Engineer
>  (08) 8303 3936      Australian Academic and Research Network
>  glen.turner@aarnet.edu.au          http://www.aarnet.edu.au/
> --
>  The revolution will not be televised, it will be digitised
>