Thanks Thomas and Martin!
I think I did cause some confusion. My problem is, that the VoIP
application alone works perfectly fine. But I get severe jitter once I
start a up- or download.
Thomas Graf schrieb:
* Kurt Huwig <42C98CEA.3080000@xxxxxxxxx> 2005-07-04 21:24
I have quality-problems with my VoIP connection caused by two causes:
1. head of line blocking
My MTU is somewhere between 1400 and 1500 and my upstream is
16kBytes/sec. VoIP sends a packet every 20ms, so one 1500 byte package
blocks the sending of 4.6 packets on time.
There is no possible way to solve this problem without lowering
the bandwidth requirements of your VoIP application. You could
try using a stronger compression algorithm by using another codec
or reduce the quality. Even the most brilliant QoS setup cannot
push more data through a pipe than physically possible.
The VoIP application sends only 75-150 byte packages. The problem are
the "normal" applications like SMTP and HTTP traffic that are using
larger packets.
2. queuing on remote side
If I run a download, the queue on my provider's side is filled up and I
get long delays.
Up to a certain amount of connections you can teach all the involved
nodes to always send below the threshold which would end in a queue
at your isp.
My problem is the downstream, e.g. a HTTP download. I thought it should
be possible to lower the incoming datarate by using a smaller TCP
window, resulting in the remote host waiting for acknowledgement of each
packet and therefore reducing the datarate. Maybe together with delaying
the TCP-ACK packets if there are a lot of downloads.
I did already try the traffic shaper, keeping my upstream bandwidth
below the line bandwith thus having empty upstream queues all the time.
But it did not fix the jitter especially on downloads, so I think
something else must be done as boxes like the AVM Fritz VoIP box is
quite unaffected when up-/downloading while using VoIP.
--
Mit freundlichen Grüßen
Kurt Huwig iKu Systemhaus AG http://www.iku-ag.de/
Vorstand Am Römerkastell 4 Telefon 0681/96751-0
66121 Saarbrücken Telefax 0681/96751-66
GnuPG 1024D/99DD9468 64B1 0C5B 82BC E16E 8940 EB6D 4C32 F908 99DD 9468
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