Manufacturer: Metricom, Inc.
Price: $350 US
Reviewer: Randy Bentson
First a confession, I didn't have to buy a laptop computer to use the Ricochet modem radio. The reality is that these devices work quite nicely on desktop systems as well as on laptops.
I read of these modems in the local free computer newspaper, but since I was quite happy with my 56Kbps frame-relay connection, I didn't give them much consideration. Then one day my connection failed and I realized I had no backup for Internet access. After a quick trip to a local computer store and a few minutes configuring a PPP connect script, I was back in action. The frame relay was fixed shortly thereafter, but I still have my Ricochet modem. I use it when visiting client sites and when testing firewall configurations, and I used it on the one occasion when the frame went down again. I've also loaned it to friends suffering from phone noise and ISP mismanagement.
Plug it into your serial port. It has two connections: one for external power and one to connect to your computer. The computer sees it as a Hayes-compatible modem with a few additional AT (i.e., standard modem) commands.
I mentioned that I had to fiddle with the PPP connection scripts. As with most computer hardware, Metricom provides software for operation with the Apple and Microsoft operating systems. Since Linux comes with support for PPP dial up, there is no need to load their software. One has only to make some small but crucial changes to the scripts. The ppp-on-dialer script needs to send the strings:
to the modem to ensure that the configuration is correct. My ppp-on script needed the line:
route del defaultbecause my system is also on a local LAN and normally gateways through the frame relay. The phone number, 777**PPP, looks unusual; it means “connect to the regular Internet service using the PPP protocol.” The script doesn't need a user name or password because the modem's serial number is used for authentication. As long as your account is current, your connection is established with a dynamically allocated IP address. Listings of these two scripts are available by anonymous download in the file ftp.linuxjournal.com/pub/lj/listings/issue45/2493.tgz.
First, the Ricochet is not a cell-phone modem. It is based on an infrastructure which is independent of the various telephone systems. Metricom has been in the wireless communication business since 1985—providing remote-access monitoring of meters to public utilities. The Ricochet division was started two years ago in order to offer wireless Internet connectivity to the public. They're currently offering service in the metropolitan areas of Seattle, San Francisco Bay, West Los Angeles and Washington, D.C. Metricom plans to extend coverage in the Los Angeles area by the end of this year and installation is underway in New York City.
If you pay attention, you'll see cell-phone antenna towers or roof-top clusters appearing everywhere. The Ricochet system is quite a bit harder to spot. There are three elements: the “modem radio” attached to your computer, a shoe box sized “microcell radio” attached to streetlamp poles at quarter mile intervals and “wired access points” to serve thirty or so microcell radios. (Seattle has 1800 microcell radios and 50 wired access points.) For instance, in this map of a Seattle neighborhood the small dots are the microcell radios, the red stars are wired access points, and the blue star is the home of Linux Journal. (The map is a product of a U.S. Census bureau server using the URL (without breaks) http://tiger.census.gov/cgi-bin/mapbrowser? lat=47.676&lon=-122.366&wid=0.10&ht=0.050& on=GRID&murl=http://www.aa.net/~bentson/tms& iwd=640&iht=720. (See Figure 1.)
Just as the Internet uses a store-and-forward model to get data from one place to another, Ricochet packets are forwarded from pole to pole from the modem radio to the wired access point, at which point they enter the conventional Internet routing. Because this service is packet based, you don't consume resources when you're not sending or receiving bits. Therefore, you're welcome to establish a connection and leave it live for as long as you wish. This is a dramatic change from telephone-based Internet services.
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.
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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