Re: ISCSI: Why the use of the Urgent Pointer

["Dick Gahan" <Dick_Gahan@eur.3com.com>]

Matt

     You wrote:-

>There could be an Urgent Pointer use negotiation mechanism, where if an iSCSI
>implementation indicates during login that it wants (requires) to receive the
urgent pointer,
>the other side must send it, even if it does not want to receive it.

I wouldn?t call this negotiation. It sounds more like coercion, the other side
does not have an option.
The function MUST be provided when requested thus not an option.

You also state that:-

>In order for iSCSI to succeed it must be able to be cost competitive with
>other solutions (10Gig Fibre Channel, etc).  This means that it must be
>implementable without putting gobs of (costly) memory on the adapter cards.
>In order to avoid this memory requirement in the presence of lost frames, the
>adapter will either have to place data in host memory were it belongs
>*requiring a framing mechanism* or throw it away.  Fibre Channel adapters
>today are able to operate in this manner today without a lot of memory because
>they can place data that arrives out of order directly where it belongs in
>host memory [because framing is provided].

This TOE adapter you mention seems dedicated for iSCSI. Other applications
that talk gig Ethernet over TCP do not seem to use this TOE. If they did use it
what does the TOE do for those other (not iSCSI) streams when data is lost ?.
They have not an URG framing mechanism built in and the adapter has not much
memory to buffer up
data while the missing piece is retransmitted.
Are you advocating a second gigabit NIC with a TOE function which has memory ?
or
a general purpose gigabit adapter which uses host memory and slow host tcp/ip
stack ?.

So I don?t see any reason to support your proposal right now.

Dick Gahan
3Com




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