After my last post, some readers were asking what tool did I used for testing the QoS and how satisfied I’m with it.

The name of the tool is Packgen. According to its developer developers, “Packgen is a simple network packet generator handling diffserv markers, useful for testing network bandwidth and QoS.” It support features like:

– Network packet flows generation with given bandwidth (packets sent at each time interval depending on the bandwidth to produce and the size of the packets to generate);

– UDP and TCP flows;

– DSCP marking;

– Log generation which gives the possibility to compute statistics on the flows (to come later).

The main difference between IPerf (which is also a great testing tool, especially for bandwidth, jitter, packet loss tests…) and Packgen, is that the last one support diffserv marking natively. Of course you can achieve the same results with IPerf, with and ACL and inbound marking of the packets matched in the access-list, but with Packgen this is straight forward.

I had a little issue when downloading this tool, as the first result in Google search engine directed me to a page with no download link: http://packgen.rubyforge.org. This contains all the needed information about features, installation and how to use it (actually one of the best README that I ever saw for such tools), but no suggestion where to download the package. I search a little bit and you can download it from this official link.

To install this tool, you need to have Ruby on your system and then just run from inside the unpacked Packgen folder:

ruby ./setup.rb

Now some words about how to use it. From my post about AutoQoS, you can see that you need at least one client and one server. This 2 devices, use different files with Packgen (Don’t worry as the files come in the source package and if not, it’s very easy to create them).

First the server file, called listen.yml (if you create it, you can give whatever name you want) looks like this:

LISTEN: udp:

–

ports: !ruby/range 17000..17002

tcp:

–

ports: !ruby/range 5002..5004

As you can see, there are 2 sections defined for UDP and TCP traffic. Then with “!ruby/range” you define a range where the server will listen. However, you can also simply use an Integer port number.

Then on the client side, there is file called sent.yml:

SEND: udp:

–

name: Voice

host: 10.10.10.100:17000

bandwidth: 700Kb

packet_size: 252B

dscp: ef

from..to: !ruby/range 0.0..60.0

–

name: Video

host: 10.10.10.100:5002

bandwidth: 2.8Mb

packet_size: 750B

dscp: cs4

from..to: !ruby/range 10.0..60.0

tcp:

–

name: Best Effort

host: 10.10.10.100:5002

bandwidth: 3.2Mb

packet_size: 1KB

from..to: !ruby/range 20.0..60.0

–

name: Background

host: 10.10.10.100:5002

bandwidth: 3.2Mb

packet_size: 1KB

dscp: cs1

from..to: !ruby/range 30.0..60.0

Here it’s a little bit more complex, but still human readable. This file also have 2 sections for UDP and TCP traffic, with the following paramters being defined:

-name: I believe it say everything

-host: ServerIP:port

-bandwidth: bandwidth to simulate

-packet size: packet in size in B, KB

-dscp: value

-from..to: !ruby/range: time intervals

After everything is defined, you just have to run Packgen to test.

On Server side first:

packgen -i listen.yml

Then on Client side:

packgen -i sent.yml

Optional you can add the -l file option, which will log the traffic send:

1258663872.6248 SEND dest=10.10.10.100:16385

1258663882.62591 SEND dest=10.10.10.100:5001

1258663895.65219 SEND dest=10.10.10.100:5002

1258663905.66876 SEND dest=10.10.10.100:5003

1258663933.72797 STOP dest=10.10.10.100:16385

or received:

1258663869.80496 LISTEN port=16384 proto=udp

1258663869.81079 LISTEN port=16385 proto=udp

1258663869.81441 LISTEN port=5002 proto=tcp

1258663869.81506 LISTEN port=5003 proto=tcp

1258663872.5886 RECV sent_at=1258663872.64102 flow=0 size=252 id=6

1258663872.58893 RECV sent_at=1258663872.64613 flow=0 size=252 id=7

1258663872.58903 RECV sent_at=1258663872.64719 flow=0 size=252 id=8

1258663872.58915 RECV sent_at=1258663872.65052 flow=0 size=252 id=9

1258663872.58924 RECV sent_at=1258663872.6742 flow=0 size=252 id=10

The configuration files and logs excerpt were from my AutoQos test. If you have any issues with using it, please contact me, or just check in details the documentation from developers site.

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