Re: [colorforth] End-to-End Internet Packet Dynamics

[Mark Slicker <maslicke@xxxxxxxxxxx>]

On Wed, 28 Apr 2004, Samuel A. Falvo II wrote:

> On Tuesday 27 April 2004 10:22 pm, Mark Slicker wrote:
> > I question why they didn't use a data rate for flow control. Also all
>
> Because data rate isn't flow control, in the sense of achieving a
> reliable link.  At best, it's flow throttling and bandwidth control.
> Sending data slower does not guarantee a reliable delivery of a packet.

Data rate could vary just as the window varies. It could go to zero if
needed. The window is not for reliability, it is for perfomance, to
reduce the number of unACKed packets sent. Packets that are not
ACKnowledged are automatically retrasmitted, this is the reliability
portion of TCP. Flow control is for performance.

>
> > the ACKs returning to the server seems wasteful, especially in
>
> Wasteful, but necessary, due to the liberty that IP gives underlying
> network technologies to not use forward error correction bits.  If
> underlying technologies employs ECC, then this would be less of an,
> though certainly not a non-existant, issue.  For more information on
> this, see Phil Karn's documentation
> (http://www.ka9q.net/papers/newlinkpaper.ps.gz) for more details on what
> would be necessary to ameliorate the work-arounds that TCP implements to
> make up for the underlying protocol's lack of integrated support for
> reliability.  Note the paper is in the context of an amateur radio
> application, but the information presented is universal regardless of
> user domain.

I think you missed my point.

In TCP, ACK is required to prevent retransmission. I belive for every two
segments in a bulk transfer 1 ACK is recomended. This is a transfer ratio
of 2:1 for a completely unidirectional transfer.

Mark

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