Subject: Re: [Tsvwg] FW: I-D ACTION:draft-culley-iwarp-mpa-00.txt

From: Joe Touch <[email-masked]>
Date: Fri, 27 Sep 2002 14:09:19 -0700

Teisberg, Robert wrote:
> 
>>-----Original Message-----
>>From: Joe Touch [mailto:[email-masked]]
>>
>>Agreed. But placing it in a buffer shared by an application requires 
>>in-order placement. Otherwise, there need to be locks that 
>>prevent the 
>>application from getting at data _until_ the TCP has ACK'd it.
> 
> Or API conventions that forbid the application to peek at the buffer
          ^^^^^^^^^^^      ^^^^^^
> prior to delivery.  Such an API seems to be explicitly allowed by RFC 793
> where it says:

I'm not sure about the juxtaposition of "conventions" and "forbid". 
You'd need a mechanism to enforce that.

>         A more sophisticated implementation would permit several
>         RECEIVEs to be outstanding at once.  These would be filled as
>                                              ^^^^^^^^^^^^^^^^^^^^^^^^
>         segments arrive.  This strategy permits increased throughput at
>         ^^^^^^^^^^^^^^^
>         the cost of a more elaborate scheme (possibly asynchronous) to
>                                              ^^^^^^^^^^^^^^^^^^^^^
>         notify the calling program that a PUSH has been seen or a buffer
>         filled. 

This statement talks about filling as segments arrive, but also later 
states that segments passed to the application must be ackd. IMO, it is 
talking more about sending a partial reply - as in 1/2-filled no-gap 
buffer, not about sending a buffer with gaps.

> If the application knows it shouldn't look at the buffer until the
> network software tells it to, it doesn't matter whether the buffer is
> filled front-to-back, back-to-front or inside-out.

That implies trust. There has to be enforcement, or this isn't TCP. The 
trust boundary is where TCP ends; if that has to include the 
application, then the bundling goes further up the stack than most would 
want.

Joe

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From: "Teisberg, Robert" <[email-masked]>
Date: Fri, 27 Sep 2002 15:25:24 -0500