RE: (no subject)

 

> -----Original Message-----
> From: [email protected] [mailto:[email protected]] On 
> Behalf Of Barry Reinhold
> Sent: Tuesday, November 30, 2004 5:36 AM
> To: RDDP
> Cc: [email protected]
> Subject: [rddp] (no subject)
> 
> 
> I would like to know if there is agreement on the following:
> 
> Given a Marker supporting Data Source that sends:
> 
> ++++++++++++++++++++++++++++
> | TCP SEG #1               |
> ++++++++++++++++++++++++++++
> Contains FPDU A (write STag 1, loc 100 with 100 A's)
> 
> ++++++++++++++++++++++++++++
> | TCP SEG #2               |
> ++++++++++++++++++++++++++++
> Contains FPDU B (write STag 1, loc 200 with 100 B's)
> 
> ++++++++++++++++++++++++++++
> | TCP SEG #3               |
> ++++++++++++++++++++++++++++
> Contains FPDU C (write STag 1, loc 300 with 100 C's), and 
> FPDU D (Read STag 1, 100 bytes from loc 300)
> 
> A marker falls in FPDU D.
> 
> During transmission TCP SEG #2 is lost, such that TCP SEG #3 
> arrives out of order at the Data Sink. The iWARP receiver 
> recovers FPDU sync by using the marker in FPDU D. TCP SEG #2 
> then arrives.
> 

Recovering the marker for FPDU D allows DDP to process FPDU D.
That allows the RDMA Read Request to be *placed*, presumably
Into an internal IRD queue. But it cannot be acted upon by
The RDMAP layer until it is deliverable, as described in 
The section you cited (5.4).  Therefore all prior writes,
including to location 300, will have been placed before
FPDU D is "delivered" to the RDMAP layer. And until it 
is delivered it is not an RDMA Read Request, ad the DDP
layer it is just an untagged message to queue 1.

> Is it the case that for a "conformant" Data Sink the contents 
> in the RDMA READ RESPONSE SHALL be "C"s?
> 
> This is interesting in that there is no gap in the TCP 
> sequence space as delivered by TCP to MPA, but there is a gap 
> in terms of what MPA has "processed".
> 
> Since clause 5.4 states that:
> 
> At the Data Sink, DDP MUST Deliver a DDP Message if and only if all 
>    of the following are true: 
> 
>      * the last DDP Segment of the DDP Message had its Last 
> flag set,  
> 
>      * all of the DDP Segments of the DDP Message have been Placed, 
> 
>      * all preceding DDP Messages have been Placed, and 
> 
>      * each preceding DDP Message has been Delivered to the ULP.
> 
> I assume that we can expect "C"s in the READ RESPONSE.
> 
> This is scheduled to become a conformance test, so I would 
> like to ensure there is agreement.
>  
>