Linux and the Next Generation Internet
A goal of our demonstration environment, in addition to concisely demonstrating the effect of differentiated services, was to prove that the queuing mechanisms within the Linux Diffserv implementation were robust enough to enforce various SLAs throughout our Diffserv domain. As shown in Figure 1, the domain was composed of three routers (one core router, two leaf routers), two Litton CAMVision-2 MPEG-2 codecs (up to 15Mbps) or two Vbrick MPEG-1 codecs (up to 3Mbps), two client workstations, one web server and one network management workstation (NMS).
In the figure, the classification of traffic is performed by the leaf routers “obiwan” and “nimitz”, and the core router “quigon” is configured for the corresponding DSCP-based forwarding and queueing. The traffic streams are color-coded to correspond to particular types of PHBs (blue=BE, red=EF and so on). Notice from the figure that the link between quigon and nimitz is 10 MBps Ethernet and is consistently oversubscribed with multiservice traffic. This is the situation where differentiation between SLAs is critical. To make sure the instantaneous change between SLAs was clearly visible to the casual observer, we used the MPEG video stream as well as some interactive, web-based streaming media (RealAudio, RealVideo, etc.).
As shown in Table 1 and Figure 1, we were able to configure several service levels with our approach, each of which was available via a single mouse click. Note that the values and configurations shown in Table 1 and Figure 1 reflect a particular set of SLAs which used only BE and EF traffic classes. When the user clicks on the desired SLA icon, the value from the HTML form field is passed to the web server via an HTTP POST operation. The form values are passed via CGI to a Perl script that processes the POST, then reconfigures each router in the domain. The routers are contacted one by one, and the SLA chosen by the administrator is invoked. Sample Perl pseudocode for the client portion of router control is shown in Listing 4, and the server portion is shown in Listing 5. As can be seen from the Perl client code in Listing 4, the NMS (or other web server) can easily pass the “current SLA” to all routers in the domain based on input from the network manager. This “control channel” interface was protected in all network configurations by a high-priority, low-rate queuing configuration, shown as the black line in Figure 1.
To provide positive user feedback at the NMS, the web interface is refreshed for the administrator while each router begins its unique network setup. Each Diffserv-enabled router in the domain receives the desired SLA and must set up its rules accordingly, depending on its position within the domain and the collection of statically defined SLAs. This is done dynamically via a system call to ipchains-restore according to the new SLA. When the ipchains-restore command finishes, the network setup is complete. The Perl pseudocode for this operation is shown in Listing 5 for a typical core router. As our system is defined, we maintain essentially a simple “database” of network/SLA configurations in pre-stored ipchains mappings.
To attempt to simulate some typical end-user traffic in addition to the constant MPEG stream, we used a number of FTP downloads, some streaming audio/video sources and a small flood ping throughout the network. Due to the interactive nature of our demonstration environment, these network-based data sources were also available “on demand” from a web-based GUI.
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