***SPAM*** Re: [ofa-general] uDAPL DTO completion question.

[Caitlin Bestler]

On Tue, Mar 31, 2009 at 6:01 PM, Jie Cai <Jie.Cai at cs.anu.edu.au> wrote:
> Local side dat_ep_post_send message to remote side,
> with DAT_COMPLETION_DEFAULT_FLAG.
> Then the local side dat_evd_wait for the send completes.
>
> Does the DTO completion event at local side of the
> send indicates the data has been received at remote side
> as well?
>
> I am bit confused about this.
>
A DAT DTO send completion means that the DAT Provider and its
underlying Transport no longer require your buffers -- and that barring
an error that tears down the connection, the data has been or will be
delivered to the remote peer.

This may mean as little as the transport layer has linearized your send
into its own buffer. Since most transport providers are not eager to
volunteer vast amounts of transmit buffering it will frequently mean
s that the remote host has acked the data. That is the lowest cost
method for the sender to know that the source buffers are no longer
needed.

Even when the underlying transport guarantees that the data is in the
remote host's buffers, it does NOT guarantee that it is in the remote
peer's cache or that the remote peer has been scheduled or has
in any way noticed that the memory has been updated.

The only guarantee that the remote peer *application* has gotten your
message is when it responds to it.