Documentation on writing a custom socket
Hans Petter Selasky
hselasky at c2i.net
Mon Mar 10 17:50:46 UTC 2008
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.
On Monday 10 March 2008, Alexander Leidinger wrote:
> Quoting Julian Elischer <julian at 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?
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