Tag: network

Novatel Merlin U740 using only Windows 7 onboard tools

I have lost the install CD of my Novatel Merlin U740, an older PCMCIA UMTS card. As a consequence I got no “Mobilink Connection Manager” after installing Windows 7 on my notebook. Fortunately I found this guide by Novatel Wireless which explains how to connect using only on-board tools in Windows Vista, by setting up a dial-up connection. It still works in Windows 7. The important part is to set the APN as part of the driver’s initialization string.

The telephone number you have to set is *99#, which should be provider-independent.

The following settings are for yesss.at only:
Username: web
Passwort: web

Remember to set the APN as part of the driver’s connection string in Window’s “Device Manager” as described in the PDF.

Again, for yesss.at this is: AT+CGDCONT=1,"IP","web.yesss.at"

For this to work properly, the SIM must not have a PIN set, as otherwise the SIM will be locked and the dialer cannot dial out. For me this is ok, as it is a pre-paid card which can hardly be abused if it gets stolen, but your situation might be different, so please consider the security implications. (I suspect that it should be possible to unlock the SIM card somehow using the AT+CPIN=1234 command, but I did not research how to separate several initialization strings, as it did not work immediately.)

The solution works quite well for me, even under Windows 7. Disadvantage is that there is no way to tell the signal strength and exact mode of operation (despite the color-coded status led on the Merlin U740).

Test-driven network management

Article Teaser RJ45 close-upTest-driven development has proven to increase quality of software in many cases. I believe that the same principle should be applied to network management. From time to time, I am occupied in managing quite large and distributed networks, consisting of many different network segments, routers, servers, etc.

Primary tool in managing any network is using monitoring software which tells you if everything is alright or if you should worry. For various reasons I have become a huge fan of Nagios for monitoring networks I am responsible for, especially for the simple extensibility by writing your own check scripts (plugins).

While working through some issues in a network, I suddenly decided to try an approach I spontaneously called “test-driven network management”¹. The steps are easy (and are a one-to-one translation of agile software-development principles):

  1. Write a Nagios test which checks for the requested/required feature.
  2. This test will fail.
  3. Implement a solution satisfying the test.

The same advantages of automated testing (better: unit testing) in software development also apply to the network management tasks:

  • The test documents what you want to achieve in a quite formal way.
  • You will (almost) immediately know when your solution breaks other requirements (if tests exist for them).
  • As networks tend to be even more fragile then software, you have to monitor whatever you implemented anyways 🙂

Whenever possible, I try to add a test (or tweak an existing one) for any trouble-ticket / feature request I come around. In my experience, customer satisfaction tends to increase, because you start noticing problems before they do and you also implement measures to prevent the same problems to occur over and over again.

¹ I am quite sure there is another technical term for it, as I am quite sure I am not inventing anything new here… If you know how this is called by others, please tell me in the comments.

[tags]development, network, sysadmin, network management, test-driven development, nagios[/tags]