Subject: [Ips] RE: draft-ietf-rddp-rdmap

From: "Caitlin Bestler" <[email-masked]>
Date: Tue, 6 Dec 2005 07:29:00 -0800

> Date: Mon, 5 Dec 2005 16:01:07 -0500
> From: "Sanjay Goyal" <[email-masked]>
> Subject: [Ips] Qs: draft-ietf-rddp-rdmap-05
> To: <[email-masked]>
> Message-ID: <[email-masked]>
> Content-Type: text/plain; charset="us-ascii"
> 
> Hi,
> As per draft-ietf-rddp-rdmap-05.txt,
> 
> page 50, Item14:
>     "A Send or RDMA Write Message MUST NOT be considered Complete
> 
>     at the Local Peer (Data Source) until it has been successfully
> 
>     completed at the DDP layer."
> 
> Q1. What does "successfully completed at the DDP layer" mean?
> Is it referring to TCP ack?
> 
> 

It means that the DDP layer has informed the RDMAP layer
that it no longer requires the original source buffers,
this is typically because the LLP has so informed it.

This could because the LLP has received an ACK of that
output, or merely that it has its packets formulated
and buffered and no longer needs the original buffers.

It is important to note that completion of a Send or Write
does NOT mean that the Data Sink has received the data.

> 
> Also Section 8.2.1 item 1 mentions:
> 
>   "An RNIC MUST ensure that a specific Stream in a  specific
> Protection Domain cannot access an STag in a different
> Protection Domain."
> 
> Q2. What does Protection Domain mean?
> 
>

A Protection Domain encloses a set of RDMA Endpoints ("QP")
and STags that can be used on those endpoints. It is an
arbitrary scoping mechanism, typically matching a user
process but sometimes narrower. For example iSER could
scope a Protection Domain to match an iSCSI session.

However a Protection Domain is used by the ULP, it prevents
STags from being used on the wrong connection, especially
somebody else's connection.

So basically, other than the enforcement it provides, a
Protection Domain has very little meaning at the DDP layer.
It's real meaning and purpose is determined by the ULP that
decides what Protection Domains to create, and why.

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