Re: iSCSI: new draft

[Matt Wakeley <matt_wakeley@agilent.com>]

They will *not all* be retransmitted if SACK (rfc2018) and fast retransmit
(rfc2581) is implemented.

-Matt

David Robinson wrote:

> Are we again presuming that you can do anything to a TCP stream
> out of order? If you miss a segment there is not much you
> can do with the segments that may follow out of order. Although
> you can buffer them, you might as well throw them away as they
> WILL be resent. So even if you know the next message boundary
> it gives you NO useful information until the entire
> contents of the message arrives.  The easy way to minimize
> tempory storage is to just drop it if you are memory
> constrained.
>
>         -David
>
> julian_satran@il.ibm.com wrote:
> >
> > JP,
> >
> > No. If a packet arrives very late and others precede it, or a packet is
> > lost and recovered with SACK later
> > you end up having to pile-up a lot of data in an adaptor or a separate
> > memory area until you can figure where to put it. The amount can be
> > minimized if you can rapidly figure out where the next boundary is.
> > Obviously you do not really hand the data to the user until you have it all
> > but you gain by having a place to store it sooner and minimize the amount
> > you have to keep in "temporary storage".
> >
> > Julo
> >
> > Raghavendra Rao <jpr@divyaroot.India.Sun.COM> on 08/11/2000 03:23:50
> >
> > Please respond to Raghavendra Rao <jpr@divyaroot.India.Sun.COM>
> >
> > To:   Julian Satran/Haifa/IBM@IBMIL
> > cc:
> > Subject:  iSCSI: new draft
> >
> > Julian
> >
> > I've trouble in interpreting this in the new draft
> >
> > >   Unfortunately, when relying solely on the "message length in the
> > >  iSCSI message" scheme to delineate iSCSI messages, a missing TCP
> > >  segment that contains an iSCSI message header (with the message
> > >  length) makes it impossible to find message boundaries in subsequent
> > >  TCP segments. The missing TCP segment must be received before any
> > >   following segments can be processed.
> >
> > This suggests that TCP might deliver a stream with a missing segment !
> > TCP will not deliver to session layer until the missing segment arrives
> > to satisfy the streaming protocol it defines.
> >
> > Have I misread something ?
> >
> > Thanks
> >
> > -JP