Date: Fri, 1 Nov 1996 21:52:36 +0100 (MET) From: J Wunsch <j@uriah.heep.sax.de> To: FreeBSD-current@FreeBSD.ORG, isdn@muc.ditec.de Subject: Re: Any ISDN-BRI cards work under FreeBSD? Message-ID: <199611012052.VAA23065@uriah.heep.sax.de> In-Reply-To: <199611010818.JAA19813@freebie.lemis.de> from Greg Lehey at "Nov 1, 96 09:18:21 am"
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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. ;-)
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