[e2e] Are we doing sliding window in the Internet?

Wesley Eddy weddy at grc.nasa.gov
Wed Jan 3 13:48:11 PST 2007

On Tue, Jan 02, 2007 at 10:07:48PM -0800, Joe Touch wrote:
> Lachlan Andrew wrote:
> > Greetings,
> > 
> > This is probably not related to the original thread (on what happens
> > in real networks, as distinct from what *should* happen), but the word
> > "bug" bugged me...
> > 
> > On 02/01/07, Joe Touch <touch at isi.edu> wrote:
> ...
> >> > delayed ACKs (as Linux receivers don't when the window is small),
> >>
> >> Delayed ACKs are strongly encouraged.
> >> Both good reasons to fix these bugs in Linux.
> > 
> > I don't follow the logic of that at all.
> Please review RFC2581.

The exact wording in RFC 2581 says that ACKs should be sent "at least" for
every 2 packets, which allows for an ACK to be sent for every packet, as
Linux does when it assumes the other side is in slow start.  I believe the
Linux behavior is perfectly allowable under the letter of RFC 2581.  I do
not consider this behavior buggy whatsoever.

One separate thing to note with regards to ABC is that the RFC2581bis
document in TCPM right now RECOMMENDS to increase CWND by the number of
bytes ACKed during slow-start - i.e. ABC is RECOMMENDED by that document
intended as an update to RFC 2581.

Wesley M. Eddy
Verizon Federal Network Systems
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