Re: [tcpm] timestamp options (was Re: New Version Notification for draft-touch-tcpm-tcp-edo-01.txt)

[Mark Allman <[e-mail]>]

> The TWHS establishes the TS for the new connection, which means old
> packets will be seen as old and discarded by TS processing.

OK, sure, fair enough.  But, again, we have plenty of non-timestamped
connections seemingly running perfectly fine today.  So, it is pretty
hard for me to get worked up about this "problem" the timestamp option
is "solving".

> >> 	- a new connection that either avoids TS in SYN or
> >> 	uses just "use TS" (two-byte) flag can't know when
> >> 	to engage the timestamp and what initial value to use
> >
> > This is just bogus.  On both counts.
> 
> FWIW, I'm saying that receiver has these problems. You're correct
> that the first TS value in an *acked* segment should be the one used
> and that the sender can know when to turn it on.

It doesn't matter if the receiver just follows the sender's lead.  The
sender can trigger things when they are needed and the receiver can
follow. 

> However, what if the receiver doesn't support TS at that point? 

If only I had said something about that in the note you are responding
to ... oh wait, I did! :-)

    Do we have to account for sending a TS mid-stream and it not being
    supported by the other end?  Sure.  It seems the answer is to ensure
    the sending rate is less than 4GB/MSL.  Is that extra work?  Sure.
    Is it worth it to save a wad of useless bytes in lots of packets on
    the Internet?  That is a judgment call where reasonable people could
    disagree, I guess.

This is pretty much a cwnd cap, so it isn't like it is rocket science
here. 

> One question is - how many connections use TS that don't expect to
> use long connections or large numbers of connections where the
> sequence number wrap is an issue?

I would say nearly all of them.

I'd bet a beer that you go look in your favorite pile of traces and
it'll be a Damn Long Time before you find even a potential problem that
timestamps will solve.

allman