Hi Carles, On Mon, Jun 20, 2016 at 10:08 AM, Carles Gomez Montenegro < [email protected]> wrote:
> Dear Michael, > > Thank you very much for your detailed comments (and sorry for the late > response). > > Please find below some inline responses: > > > Just out-of-curiosity: In 1981, when the current TCP spec was published, > > end hosts had significant processing and memory limitations. Quite a bit > > of the TCP protocol mechanisms were designed to deal with senders and > > receivers that have very small buffers, e.g., of the order of the maximum > > segment size.RFC 793 is very carefully designed to deal with these > > constraints. And current TCP implementations are still backward > compatible > > to RFC 793. > > > > When quickly scanning through this document, some observations (the list > > is not comprehensive): > > > > - TCP counts window sizes in bytes, which > > draft-gomez-core-tcp-constrained-node-networks-00 seems to ignore. > > Agreed. We'll address this in the next draft revision. > > > - Out-of-my-head, nothing prevents a TCP sender from limiting the > > congestion window to a small window (e.g., one MSS). This basically turns > > TCP into a stop-and-wait protocol. A TCP sender can unilaterally decide > to > > limit its congestion window if it wants to simplify its implementation. I > > am not sure if RFC 2119 language is needed for that at all. > > > > - A TCP receiver can use the receive window to prevent the sender from > > sending data, e.g., if it can only deal with one MSS. It may be > > interesting to look into whether advertising a maximum receive window > e.g. > > of at most one MSS would solve some of the problems discussed in the > > draft. > > Right, one thing to provide details about in the document is which are the > available ways to enable the intended stop-and-wait operation. > I'm guessing clamping window size won't be a good way to make TCP perform stop-and-wait operation and there is no good way for it. Because TCP is basically not designed to perform stop-and-wait operation, I think you'll have to describe the operation explicitly if you want to do it. Thanks, -- Yoshi
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