Wireless Networking in Africa
Global connectivity in Africa is in an early stage due to installation costs, insufficient basic infrastructures, low quality of available telecommunication services and limited financial support. The application of wireless technology is an effective choice to overcome some of these problems, at least within smaller areas. This is true even if transmission speeds are lower than the ones achieved by wired networks.
Within a university campus, it is easier to install a radio link system than to place cables or expensive optical fibers in the ground. Furthermore, radio installations are easier to protect from external natural phenomena such as flood, landslide, etc. At first glance, wireless LANs look more expensive than wired LANs, but in the long term they have lower maintenance costs and are relatively easy to configure. The use of Linux and standard radio-communication technologies, in conjunction with the many Linux software applications, makes this task even easier.
With this scenario in mind, the “Programme of Training and System Development on Networking and Radio Communications” was initiated in 1995 at the Abdus Salam ICTP, Trieste, Italy. The objective of this programme is to provide technical assistance and training to academic and scientific institutions in developing countries—institutions with a need for small area computer networks and a connection to the Internet, either directly or through national networks.
The Abdus Salam ICTP in Italy and the Obafemi Awolowo University (OAU) of Ile-Ife in Nigeria agreed to collaborate in the establishment and future evolution of a Pilot Educational and Research Computer Network at OAU. Such a network, based principally on personal computers running Linux, today provides connectivity between several faculties and departments on the campus.
Training technical staff on the hardware (PCs, cabling, radio techniques) and software (network and system administration) took place initially in Trieste. The developmental and simulation work was completed in four months, ending in January 1996, when all the necessary equipment was sent to OAU. The system was installed in April 1996. At that time, staff members of other Nigerian universities came to Ile-Ife in order to benefit from this exercise and be introduced to Linux for the first time. Besides getting acquainted with the new technology, this experience led to further connections to the OAUNET. The campus network has been in operation since June 1996 without any major problems and has proven to be highly beneficial for academic life at the University.
As shown in Figure 1, the wireless campus network (OAUNET) is based on a radio system in the UHF band; it initially involved three separate buildings and had the capacity to be rapidly extended to other university structures. The wireless link uses a spread-spectrum, direct-sequence technique providing data transmission at 2Mbps. The so-called “spread-spectrum” is a digital coding method in which the signal is transformed or spread so that it cannot be received by any receiver except the designated one that understands the transmitted signal code. It minimizes interference to other users and normally does not require an operation license in the ISM (International Scientific and Medical Band), depending on the regulation adopted by the country.
Inside each building, an Ethernet 10-BASE 2 cabling structure is installed in order to keep the initial costs as low as possible (i.e., no hubs, less cable) and to ensure the local availability of spares (BNC), etc. In each of these buildings, a Linux PC acts as “faculty server” and provides mail services for the local users and does routing to the backbone. This strategy has been selected to keep the user-generated traffic local and reduce the access to the main backbone. All services are TCP/IP-based to keep the system as standard as possible with Internet protocols, avoiding future modifications when full connectivity might be provided to the university.
The academic network gateway and the main mail host are located the Department of Computer Science at the university. Due to national regulations and the lack of a permanent connection to the Internet, the gateway is linked on a dial-up base (uucp) using an international direct-dialing line to the ICTP computer network in Trieste, Italy. Software was developed by OAU staff with some assistance from ICTP to refine the basic uucp mail transfer: a custom sendmail delivery program batches mail in intermediate-sized, BSMTP (batch simple mail transfer protocol) formatted files; these files are compressed as much as possible before being transferred over uucp. To cope with telephone line instabilities, a uucp relay was placed in Lagos; the uucp configuration takes care of selecting the path either directly to Trieste or through the Lagos relay, automatically choosing the one that works.
Practical Task Scheduling Deployment
July 20, 2016 12:00 pm CDT
One of the best things about the UNIX environment (aside from being stable and efficient) is the vast array of software tools available to help you do your job. Traditionally, a UNIX tool does only one thing, but does that one thing very well. For example, grep is very easy to use and can search vast amounts of data quickly. The find tool can find a particular file or files based on all kinds of criteria. It's pretty easy to string these tools together to build even more powerful tools, such as a tool that finds all of the .log files in the /home directory and searches each one for a particular entry. This erector-set mentality allows UNIX system administrators to seem to always have the right tool for the job.
Cron traditionally has been considered another such a tool for job scheduling, but is it enough? This webinar considers that very question. The first part builds on a previous Geek Guide, Beyond Cron, and briefly describes how to know when it might be time to consider upgrading your job scheduling infrastructure. The second part presents an actual planning and implementation framework.
Join Linux Journal's Mike Diehl and Pat Cameron of Help Systems.
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With all the industry talk about the benefits of Linux on Power and all the performance advantages offered by its open architecture, you may be considering a move in that direction. If you are thinking about analytics, big data and cloud computing, you would be right to evaluate Power. The idea of using commodity x86 hardware and replacing it every three years is an outdated cost model. It doesn’t consider the total cost of ownership, and it doesn’t consider the advantage of real processing power, high-availability and multithreading like a demon.
This ebook takes a look at some of the practical applications of the Linux on Power platform and ways you might bring all the performance power of this open architecture to bear for your organization. There are no smoke and mirrors here—just hard, cold, empirical evidence provided by independent sources. I also consider some innovative ways Linux on Power will be used in the future.Get the Guide