Subject: Re: Important question re: new TCP options on data segments

From: Bob Braden <[email-masked]>
Date: Wed, 9 Aug 2000 19:55:19 GMT

*> 
  *> Actually you made me realise a worse problem. It isnt the options and option
  *> space that is a pain, its the sudden change of MSS relative to the MTU due
  *> to additional header overhead
  *> 
  *> 
  *> 
Why should a "sudden" change of MSS by a few bytes matter to TCP
dynamics?

Bob Braden

---

From: Alan Cox <[email-masked]>
Date: Wed, 9 Aug 2000 22:38:46 +0100 (BST)

> Why should a "sudden" change of MSS by a few bytes matter to TCP

It depends how people implement delayed ack handling. Traditionally you play
guess the MSS in order to skip delayed ack on smaller frames so Nagle doesnt
bite you hard.

Alan

---

From: Frank Solensky <[email-masked]>
Date: Fri, 11 Aug 2000 12:55:25 -0400

> Why should a "sudden" change of MSS by a few bytes matter to TCP

Some implementations may break up the transmit window into MSS-sized blocks so
that transmission just becomes a matter of dropping the headers in front.  As
you say, though, that's just an implementation detail -- the sender could just
as easily assume worst-case and fragment into MSS - (IPv* + 20) for the life
of the connection.
								-- Frank