Date: Mon, 10 Mar 2008 11:13:07 -0700 From: Julian Elischer <julian@elischer.org> To: Hans Petter Selasky <hselasky@c2i.net> Cc: Alexander Leidinger <Alexander@leidinger.net>, Robert Watson <rwatson@freebsd.org>, freebsd-hackers@freebsd.org Subject: Re: Documentation on writing a custom socket Message-ID: <47D57A33.1070209@elischer.org> In-Reply-To: <200803101751.48055.hselasky@c2i.net> References: <200803081133.02575.hselasky@c2i.net> <47D41160.9070901@elischer.org> <20080310105727.ah4y31sh40o04gw4@webmail.leidinger.net> <200803101751.48055.hselasky@c2i.net>
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Hans Petter Selasky wrote: > ISDN can have more than 2-data channels per logical unit. There is something > called E1 and T1 which has 30 and 24 B-channels respectivly per D-channel. I know, but neither of these represent any challenge to modern hardware. > > --HPS > > On Monday 10 March 2008, Alexander Leidinger wrote: >> Quoting Julian Elischer <julian@elischer.org> (from Sun, 09 Mar 2008 >> >> 09:33:36 -0700): >>> Hans Petter Selasky wrote: >>>> On Saturday 08 March 2008, Robert Watson wrote: >>>>> On Sat, 8 Mar 2008, Hans Petter Selasky wrote: >>>>> >>>>> For example, do you >>>>> anticipate using or even needing the routing facilities, and how might >>>>> you map ISDN telephony parts into the normal network stack >>>>> infrastructure of addresses, routing, interfaces, etc? >>>> Hi Robert, >>>> >>>> ISDN is very simple. In the ISDN world there is a term called TEI >>>> which is the Terminal Entity Identifier. This kind of like an IP >>>> address. >>>> >>>> Besides from the signalling there are 2 B-channels which can >>>> transport data or audio. One of my goals is to achive zero copy >>>> when moving data to/from an ISDN line and also in combination to >>>> Voice over IP. Currently data is moved through userland (Asterisk >>>> typically) which is usable in the short term, but in the long run I >>>> want this extra copying removed. The idea is that I can route [IP] >>>> packets (mbufs) through various filters in the kernel without the >>>> need for copy. >>> Given the speed of ISDN connections, It is not worth doing zero copy >>> on ISDN unless you have more than 1000 of them, which seems unlikely. >>> given a total throughput of 128000 b/s and the speed of current >>> hardware, the number of packets per second is probably not high >>> enough to make the difference even noticable. >> What about low-power embedded systems and a high count of small >> packets (VoIP)? Where do you draw the line between powerful enough and >> how do you chose this line? >> >> Bye, >> Alexander. >
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