Re: ISCSI: Urgent Flag requirement violates TCP.

[Michael Krause <krause@cup.hp.com>]

At 02:57 PM 11/13/00 -0800, Matt Wakeley wrote:

>I'll bet most TCPs lie about how much they could buffer if all open 
>connections
>suddenly experienced a burst of data and the application(s) where busy doing
>something other than reading from TCP...

They don't lie because in general they do not know.  They rely upon the 
adapters to be able to receive datagrams or not and if the adapters cannot 
allocate buffers, the adapters drop the inbound datagram packet and TCP 
treats this as a proper congestion event, i.e. resource shortage somewhere 
below it.  Statistically this works well as most windows are not all 
actively receiving packets at the same time.

>Yep - the way SCSI works, the application provides the buffers when it 
>issues the
>command.

Hence, SCSI throughput will be limited by the available target memory since 
these targets are advertised to the NIC as part of the operation.  This is 
really independent of the using iSCSI / transport / phy.

Mike