Linux Teleconferencing: Improving the Wireless Network
A stated goal of the Third Generation cellular standards bodies (3G) is for the wireless network to function as a seamless extension to the Internet and other IP-based packet network services. The brunt of the ground-breaking work we still await has been passed from companies to standards bodies to the Internet Engineering Task Force (IETF). IP transparency extends a plethora of services to the mobile devices already available to those with a wire line to the Internet, as well as simplicity and ease of adding new and more creative services explicitly designed to enhance wireless experience. An obvious result is an increase in the demand for wireless minutes by customers of the 3G carrier members.
The bandwidth available for broadband data transmission is both restricted and costly. Licenses for the frequency spectrum needed to support 3G services have been auctioned to network operators in the UK for $36 billion. More recently the Federal Communications Commission (FCC) raised a net $17 billion in a similar auction to US-based operators. This prompts carriers to improve the efficiency with which they employ the spectrum. The use of IP as a transport mechanism for voice (e.g., VoIP) requires the wireless network to carry real-time multimedia, even as it struggles to do non-real-time multimedia. For example, a full rate voice encoder like the G721.1 used by GSM-type networks generates 30ms (milliseconds) of payload, straddled with 40 bytes of a combined IP, UDP and real-time protocol (RTP) header as prescribed in the H.323 International Telecommunications Union (ITU) protocol for the delivery of multimedia. The 30ms of speech payload typically translates to 20 bytes, thereby giving us an efficiency of only 33%.
Header compression algorithms proposed to the IETF reduce the header down to one byte in steady state but have varying degrees of hobbling complexity. The header compression algorithm is required to present both bit-exact payload and an encapsulating IP protocol header to the mobile device. This is referred to as loss-less compression.
The benefits presented by header compression prove to be an imperative measure in increasing the spectral efficiency of multimedia communications, particularly since CRTP, proposed in the late 1990s by Cisco, is deemed insufficient, or not robust enough, by the involved steering committees of the IETF, as well as the Third Generation Partnership Project (3GPP).
The details of which header compression algorithm the IETF will choose have not been fully determined. Nonetheless, the requirements have been hammered out and are summarized in Table 1. In fact, the current proposals meet many of the requirements but are peppered with intellectual property rights—something that defeats the objective of the IETF. A second round of proposals are under consideration so that different methodologies may be solicited. The current algorithms exploit the nature of the IP/UDP/RTP streams. Tables 3, 4 and 5 classify the nature of the header field for each protocol IP, UDP and RTP respectively. Table 2 defines the classifications.
The essences of these algorithms are the strategies borne from these classifications. They are “never send”, “communicate at least once”, “communicate at least once or update”, “communicate update and/or refresh frequently”, “guarantee continuous robustness”, “communicate as is in all packets and establish” and “be prepared to update delta”.
Telecommunications companies that have pursued this approach to compress packet headers range from Nokia, Matsushita and Cisco to, most notably, Ericsson, for their heavyweight effort. The full details of their proposed algorithm have been submitted in IETF draft form and can be found at http://www.dmn.tzi.org.org/ietf/rohc/.
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