ISDN / BT home highway

Brian Somers brian at Awfulhak.org
Fri Oct 6 01:57:46 BST 2000


> On Tue, Oct 03, 2000 at 06:37:44PM +0100, Brian Somers wrote:
> > =

> > =

> > A TA that does the MP stuff itself isn't a great deal of use with =

> > standard 115200bps UARTs - link bandwidth is higher than DTR =

> > bandwidth.
> > =

> =

> Is this not true of external modems as well though? I've got an interna=
l
> one and can regularly exceed 115200bps:
> =

>    PPP ON parish> show phy
>    Name: deflink
>     State:           open (with carrier)
>     Device:          /dev/cuaa2
>     Link Type:       interactive
>     Connect Count:   1
>     Physical outq:   0
>     Queued Packets:  0
>     Phone Number:    1234567890
> =

>    Defaults:
>     Device List:     "/dev/cuaa2"
>     Characteristics: 115200bps, cs8, no parity, CTS/RTS on
>     CD check delay:  device specific
> =

>    Connect time: 1:00:51
>    10416974 octets in, 164815 octets out
>      overall     2898 bytes/sec
>      currently    115 bytes/sec in, 51 bytes/sec out (over the last 5 s=
ecs)
>      peak       23908 bytes/sec on Thu Oct  5 23:57:40 2000
>    PPP ON parish> =

> =

> That's 239080bps (at 10bits/byte including the stop bits), over double =
the
> rate of a 16650 UART, so if this was an external modem what would happe=
n?
> Reduced transfer rates or would the modem buffer the data?

Interesting.... I guess the limitation is only on the agreed DTR =

speed between the UART and the external modem (agreed at AT time).
Your internal modem is not emulating that limitation ;-)

-- =

Brian <brian at Awfulhak.org>                        <brian@[uk.]FreeBSD.org=
>
      <http://www.Awfulhak.org>                   <brian@[uk.]OpenBSD.org=
>
Don't _EVER_ lose your sense of humour !






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