Howdy!
As you're surely aware, UDP does not guarantee delivery.
Now to the testing: when you try to transmit traffic with a certain
speed and there's some bottleneck between sending party (iperf client)
and receiving party (iperf server), then packets get either delayed or
dropped. In case of TCP, delaying packets mean decreasing throughput
(sending party throttles TX rate down), while in case of UDP sending
party doesn't care about it and packets will evenually get dropped.
The thing is: you can't tell where the bottleneck is unless it's the
first leg (USB data terminal in your case). But then some data terminals
behave like they were kind of routers, meaning they accept whatever it's
thrown at and then drop surplus data. Most of data terminals, though,
throttle down TX rate so that OS' IP layer sees decreased throughput and
you don't get too many dropped packets.
Peace!
Mkx
-- perl -e 'print $i=pack(c5,(41*2),sqrt(7056),(unpack(c,H)-2),oct(115),10);'
-- echo 16i[q]sa[ln0=aln100%Pln100/snlbx]sbA0D4D465452snlb xq | dc
------------------------------------------------------------------------
BOFH excuse #166:
/pub/lunch
Alfredo Alcantara je dne 29/06/10 15:11 napisal-a:
Hello,
I´ve been doing some Packet Loss tests and i´ve been noticed the
following,
I´m using a USB modem and the following config. in the client, iperf
-c x.x.x.x -u -b 2.1m (2.1m because this is the max Throughput i can get)
so, sometimes the packet loss is 0 % (when the th is high and the
network is free) but sometimes when the TH is like 1000 Kbps or 1500 Kbps
the Packet Loss start to increase (like 20 %).
the thing is, if i drop the -b parameter to 1.5 m or 1 m the Packet
Loss drops too (to 0 %).
in other example if i have a -b option in 2.1m and the th is 1600 Kbps
the Packet Loss is 5 %, but when i have -b 1.4 and the th is 1600 i
have 0%.
This why i wonder if the iperf, with the -b option is improving the
packet loss. (maybe the packet get lost between the computer and the
USB modem).
Hoping you can help me with this issue,
best of regards and thank in advance.
Alfredo Alcantara
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