Short Range Devices in Europe A Short Range Device (SRD) is a radio transmitter with low interference capability. They usually operate on the ISM (Industrial, Scientific and Medical) unlicensed band, and they must accept interference caused by other ISM devices. The European Conference of Postal and Telecommunications Administrations (CEPT) is in charge of frequency assignments [...]
Cisco has it’s Application Extension Platform which provides hardware modules to plug in to some of its routers that allow to run a Linux environment that can interface with the IOS. 3Com has its Open Network Initiative. For a good overview of the topic read this. The article mentions some obvious applications, but one of [...]
There is a new open source revolution in the way. Open source software is being used to compete in the routing market against giants as Cisco. For low end routers an open source solution has fantastic performance and much lower cost. It can also be deployed on standard blade servers and runs on familiar Linux [...]
Another network related problem with the Linux kernel I can't explain. The following example code receives a multicast stream RX_MC_IP:RX_MC_PORT and resends it to TX_MC_IP:TX_MC_PORT. Then it tries to receive from the stream we are just producing, and it succeeds. I wouldn't expect the kernel to loop the stream we are producing back to the [...]
Good tip from a working colleague. Ubuntu 8.10 (Intrepid Ibex) is configured not to receive certain ranges of multicast traffic. The 225.0.0.0 range works, but for example the 233.0.0.0 doesn’t. This probably has to do with it being reserved for internet wide multicast. The solution is to edit /etc/sysctl.d/10-network-security.conf, and change the two lines ending [...]
Just a reminder for the future – with time the NAT traslation tables on our office Cisco router get full and you start to get timeout on connections. You usually notice it when a NATted browser can’t access a page, but you can ping the server from the router. To clear the dynamic translation table [...]
I haven't found any example on the net of an asynchronous I/O UDP server, that is one that uses signals to receive UDP packets. I enclose an example which can be compiled with or without asynchronous I/O. Note that in my final implementation I'll use real time signals which pass the socket descriptor to the [...]
Download the latest client version from here. For version 4.8.02.0030, tar xvzf vpnclient-linux-x86_64-4.8.02.0030-k9.tar.gz sudo vpnclient/vpn_install You may need to install the kernel headers: sudo apt-get install linux-headers-`uname -r` Modify the /etc/opt/cisco-vpnclient/Profiles/sample.pcf file with your access details (maybe rename it to something more descriptive of the connection, for example myconnection.pcf) The vpnclient service will start [...]
Traditionally I have been using NISTnet for all my network simulation needs. Nowadays NISTnet is an unmaintained application that runs under Linux 2.4.x, and as such it is not the best choice. Today in the lab I was trying to simulate an IP video quality problem. I wanted to simulate a 4Mbit capped link with [...]