Latency simulation over long fat network
One of our clients asked us how we handle latency, and not just a few ms across racks but 2 and even 3 digit ms latency that indicates geographically separate locations across continents, not just a country. Not only that, the “pipes” involved are 10Gbps and we had to fill them. We have the theories and made models of how it would work. We perhaps might not be able to fill a 10Gbps fully with one stream, we could fill it with multiple streams but we had to validate this conclusion.
The question now becomes, how do we test this. We’ve done our research and there are only a few commercial solutions available like the Netropy 10G2 which is a 4 port, 2 lane hardware latency simulator for $30,000 new. Not only is that outside my budget, it is still limited to simulating 2 10Gbps pipes while we need at least 3 lanes (6 ports) and possibility to expand to more as necessary. We decided it was cheaper in terms of total cost to put the research into creating our own Latency Simulator.
Introducing worldsynth for your world generation and building needs
After many years of development in my spare time, I’ve decided to release Worldsynth as a Free and Open Source Software. As a world generator, it fills the roll and can also be rapidly extended to support additional features. The source might not be of top quality, but the main purpose of creating it has been fulfilled and I want to share it. I only hope that others will find it useful and want to build upon it.
There is still much more functionality that I would like add and additional polishing to the user interface. Midway through I switched from pygame to pyside or Qt4 for the GUI. I consider it ready for “Alpha” at this point, meaning there might be bugs and few experimental features that may break but otherwise usable.
Dell DSET on Ubuntu 10.04 and 12.04
Dell System E-Support Tool (DSET) is an informative tool used by Dell’s support engineers to help diagnose problems for their clients. It is almost a requirement now and Dell usually refuses to continue support without a DSET report.
The problem is that DSET is only supported on Redhat and SuSE Linux and there isn’t any information on how to get it running in Ubuntu. I’ve assembled a rough guide on how to get DSET up and running on Ubuntu 10.04 and 12.04 and it is tested against a Dell R610 and R620.
Finding and making a network subnet calculator
Doing subnet calculations by hand can be tedious and thankfully there are tools available online to help with that. One in particular Subnet Calculator with a PHP backend was handy and compact.
Wireless BCM4312 3.2 kernel
Since there is an Ubuntu package ‘firmware-b43-lpphy-installer’ which is up to date and will work against the 3.0 kernel, my earlier posts are obsolete. If you are not running Ubuntu, then you will still need to reference my post.
The latest 3.2 Linux kernel however has a few ABI changes, most notably in the network stack which effects the Broadcom’s wl module. Most notably is: .ndo_set_multicast_list which was replaced with .ndo_set_rx_mode.