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Re: [hybi] CML

John Tamplin <jat@google.com> Mon, 23 August 2010 03:32 UTC

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From: John Tamplin <jat@google.com>
Date: Sun, 22 Aug 2010 23:32:19 -0400
Message-ID: <AANLkTi=G-gZ1+7uoYE=fhiKFUXoziWacx5_k-HfxC-0z@mail.gmail.com>
To: "Thomson, Martin" <Martin.Thomson@andrew.com>
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Subject: Re: [hybi] CML
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On Sun, Aug 22, 2010 at 11:27 PM, Thomson, Martin <Martin.Thomson@andrew.com
> wrote:

> CML, which I presume signifies "complete message length", has appeared in
> some of the later framing proposals.  Can anyone provide me with a succinct
> summary of the reasons for its inclusion?
>

There were objections to fragmentation without it, as the receiver would
then have to realloc/copy the buffer it will hand off the client code
without it.  Since fragmentation support is a requirement, even if a sender
writes a message in one large frame, an intermediary might choose to break
it up into multiple frames.  With CML, the  fragmenter can still indicate to
the ultimate receiver the size of the original message.

It is optional so that it is only included when it is useful and available,
and may be an estimate that is updated (which facilitates a UI for reporting
progress).

-- 
John A. Tamplin
Software Engineer (GWT), Google

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