Date: Sun, 22 Nov 1998 11:10:23 -0800 From: bmah@CA.Sandia.GOV (Bruce A. Mah) To: Andrey Tchoritch <andy@moldsat.md> Cc: "Bruce A. Mah" <bmah@california.sandia.gov>, "Nick A. Fikouras" <nick@dcs.shef.ac.uk>, "freebsd-questions@FreeBSD.ORG" <freebsd-questions@FreeBSD.ORG> Subject: Re: Timestamps and nonces in IP packets Message-ID: <199811221910.LAA13033@stennis.ca.sandia.gov> In-Reply-To: Your message of "Sun, 22 Nov 1998 20:58:55 %2B0200." <Pine.BSF.3.96.981122205742.12983A-100000@faust.moldsat.md>
next in thread | previous in thread | raw e-mail | index | archive | help
--==_Exmh_-371930521P Content-Type: text/plain; charset=iso-8859-1 Content-Transfer-Encoding: 8bit If memory serves me right, Andrey Tchoritch wrote: > On Sun, 22 Nov 1998, Bruce A. Mah wrote: > > If memory serves me right, "Nick A. Fikouras" wrote: > > > > > I've noticed while monitoring TCP communications between FBSD machines > > > that every IP packet contains timestamps and nonces that take up an > > > extra 40 octets in the packets. Does anybody know how I can turn off > > > this setting? > > > > Haven't seen anyone write an answer to this yet, so: > > > > Edit /etc/rc.conf, and set: > > > > tcp_extensions="NO" > > > > > What is this extensions for? The timestamp option in the TCP header allows to sender of a TCP segment to compute the round-trip time (RTT) for every segment sent and acknowledged. It places a timestamp in every outgoing segment it sends...the receiver (assuming it support this option) copies this timestamp back to an appropriate field in the ACK it sends back for that segment. Without the use of the timestamp extension, the sending TCP can only estimate the RTT once per round trip. IIRC, the other option controlled by tcp_extensions is window scaling. This allows larger TCP congestion windows than the 64K allows by the original specification, by multiplying the window sizes by an agreed-upon power of 2. Useful mostly for high-delay, high-bandwidth paths, such as satellite links. Bruce. --==_Exmh_-371930521P Content-Type: application/pgp-signature -----BEGIN PGP MESSAGE----- Version: 2.6.2 iQCVAwUBNlhhn6jOOi0j7CY9AQHlCAP+KcTxDsS3NbI18tsYXF7IyEin4WSnOZDR ZTaCgGhF0MHu9bJ8XYJ8HSASJif8HYlkfQWsmhl/SF14UKY+X+73J52kNiHBITCe XEjUHnyl0lCbRImFMV3SNDJuwyS6ZTmCSY8J3nr81YkVAf67j6qznnKEWQh6mXmR ceYYdQCf1Rs= =//r8 -----END PGP MESSAGE----- --==_Exmh_-371930521P-- To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-questions" in the body of the message
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?199811221910.LAA13033>