Am Donnerstag, 16. November 2006 17:37 schrieb Larry Brigman:
> On 11/15/06, Daniel Musketa <Daniel@musketa.de> wrote:
> > I can watch traffic coming in on ppp0 with `iftop` and it never exeeds
> > 900kbit. Why could a 2000kbit headroom be not enough for clean receiving
> > of 80kbit VoIP data?
>
> Because [...] what comes first, goes out first. Also if the download
> side can send at a higher rate than you line can handle, there
> will be a queue of packets at the router handling the bandwidth
> limititation.
`iftop` shows me a rate of 800kbit for packets going out to the LAN on eth1.
This is the ceil value for egress shaping from router to LAN. But I also can
watch the download rate of packets coming in from ppp0. And it's never more
than 900kbit, so TCP's mechanism of lowering TX speed after delayed/missing
ACKs seems to work. To me it looks as if there wasn't a filled queue on the
ISP's side of the line.
`tc -s ...` shows me a backlog of about 20p in the "download class".
I still can't understand why more than 2 Mbit free bandwith and an empty queue
can cause drop outs ... mmh ...
Daniel
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