From owner-freebsd-current Fri Nov 1 13:52:49 1996 Return-Path: owner-current Received: (from root@localhost) by freefall.freebsd.org (8.7.5/8.7.3) id NAA27182 for current-outgoing; Fri, 1 Nov 1996 13:52:49 -0800 (PST) Received: from irz301.inf.tu-dresden.de (irz301.inf.tu-dresden.de [141.76.1.11]) by freefall.freebsd.org (8.7.5/8.7.3) with SMTP id NAA27125 for ; Fri, 1 Nov 1996 13:52:34 -0800 (PST) Received: from sax.sax.de (sax.sax.de [193.175.26.33]) by irz301.inf.tu-dresden.de (8.6.12/8.6.12-s1) with ESMTP id WAA23458; Fri, 1 Nov 1996 22:51:49 +0100 Received: (from uucp@localhost) by sax.sax.de (8.6.12/8.6.12-s1) with UUCP id WAA03011; Fri, 1 Nov 1996 22:51:48 +0100 Received: (from j@localhost) by uriah.heep.sax.de (8.8.2/8.6.9) id VAA23065; Fri, 1 Nov 1996 21:52:36 +0100 (MET) From: J Wunsch Message-Id: <199611012052.VAA23065@uriah.heep.sax.de> Subject: Re: Any ISDN-BRI cards work under FreeBSD? To: FreeBSD-current@FreeBSD.ORG, isdn@muc.ditec.de Date: Fri, 1 Nov 1996 21:52:36 +0100 (MET) Reply-To: joerg_wunsch@uriah.heep.sax.de (Joerg Wunsch) In-Reply-To: <199611010818.JAA19813@freebie.lemis.de> from Greg Lehey at "Nov 1, 96 09:18:21 am" X-Phone: +49-351-2012 669 X-PGP-Fingerprint: DC 47 E6 E4 FF A6 E9 8F 93 21 E0 7D F9 12 D6 4E X-Mailer: ELM [version 2.4ME+ PL17 (25)] MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-current@FreeBSD.ORG X-Loop: FreeBSD.org Precedence: bulk As Greg Lehey wrote: > Synchronous transmission is block oriented. Various techniques are > used to recognize the beginning and end of the block, and all the data > in a block are sent without any delay between the bits. When > transmitting 8 bit bytes (octets), there's a ratio of 8 bits per > octet, so 64 kbps becomes 8 kB/s. I think that's not 100 % correct. You've still got some flagging in HDLC (01111110 IIRC) which needs to be escaped whenever the flag occurs within the data stream. However, while the overhead for async transmission is >= 25 % (at least 2 bits per 8 data bits), it's much lower for sync transmission (but dependant on the data pattern). -- cheers, J"org joerg_wunsch@uriah.heep.sax.de -- http://www.sax.de/~joerg/ -- NIC: JW11-RIPE Never trust an operating system you don't have sources for. ;-)