Date: Mon, 10 Mar 2008 10:57:27 +0100 From: Alexander Leidinger <Alexander@Leidinger.net> To: Julian Elischer <julian@elischer.org> Cc: freebsd-hackers@freebsd.org, Robert Watson <rwatson@freebsd.org>, Hans Petter Selasky <hselasky@c2i.net> Subject: Re: Documentation on writing a custom socket Message-ID: <20080310105727.ah4y31sh40o04gw4@webmail.leidinger.net> In-Reply-To: <47D41160.9070901@elischer.org> References: <200803081133.02575.hselasky@c2i.net> <20080308171435.J88526@fledge.watson.org> <200803091027.39843.hselasky@c2i.net> <47D41160.9070901@elischer.org>
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Quoting Julian Elischer <julian@elischer.org> (from Sun, 09 Mar 2008 =20 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 y= ou >>> 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 =20 >> which is the Terminal Entity Identifier. This kind of like an IP =20 >> address. >> >> Besides from the signalling there are 2 B-channels which can =20 >> transport data or audio. One of my goals is to achive zero copy =20 >> when moving data to/from an ISDN line and also in combination to =20 >> Voice over IP. Currently data is moved through userland (Asterisk =20 >> typically) which is usable in the short term, but in the long run I =20 >> want this extra copying removed. The idea is that I can route [IP] =20 >> packets (mbufs) through various filters in the kernel without the =20 >> 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 =20 packets (VoIP)? Where do you draw the line between powerful enough and =20 how do you chose this line? Bye, Alexander. --=20 http://www.Leidinger.net Alexander @ Leidinger.net: PGP ID =3D B0063FE7 http://www.FreeBSD.org netchild @ FreeBSD.org : PGP ID =3D 72077137
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