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

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

> > You are 100% correct.  If we have a table defining all possible error,
not
> > receiving the PDU with the right StatRN is one.  The question becomes
how
> > long do you wait?  I also understand your position in using ping every
10
> > seconds so we don't need to wait four minutes to decide if TCP
> > connection is gone.
>
> Wouldn't the ping simply queue up behind other undelivered TCP
> data?
> --
>  Glen Turner                                 Network Engineer
>  (08) 8303 3936      Australian Academic and Research Network
>  glen.turner@aarnet.edu.au          http://www.aarnet.edu.au/

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 .  This is must a
because BB-Credit only slows the adapter down to match the incoming frame
rate to the host memory bus speed rate.  The TOE adapter takes the ping
frame from incoming FIFO and sends reply back immediately to the outgoing
FIFO, no queuing and no waiting.  The adapter does the same for the Fibre
Channel ACK frames.  The same mechanism can even be used to TCP ACK's, if
properly designed.