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A host is considered unreachable if none of the pings sent to it are responded to. To illustrate this we chose a reliable host at SLAC (pinger.slac.stanford.edu) and analyzed the unreachability of Pakistani hosts seen from SLAC.
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Table of unreachability seen from SLAC to Pakistani hosts in 2010. Higher values (bad) are colored redder. The data is sorted by increasing unreachability in Jan 2011. [SpreadsheetIEPM:Pakistan^pak-unreach.xlsx] | | Chart of the unreachability of Pakistani hosts seen from SLAC Dec 2010 and Jan 2011 | Smokeping examples of unreachabilltyseen unreachabillty seen from SLAC for 120 days Oct 2010 - Jan 2011. |
It is seen that several hosts exhibit high unreachability. The reasons behind the high unreliability are usually site specific and vary from lack of reliable power and a source of backup power, floods, lack of access to the site when there are problems that require physical access, lack of expertise, and lack of interest from a site.
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RTT and Losses for 2010
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The average of the minimum RTT measured between regions of Pakistan between Dec-2009 and November 2010. Spreadsheet | Various percentiles for the Inter Packet Delay Variation (IPDV or jitter) between Pakistani monitoring hosts and remote host pairs. The line shows the number of pairs with measurements contributing to the results. Spreadsheet | The blue dots are the median losses seen between all pairs of monitoring and remote hosts for each month. The error bars show the extent of the 25 and 75 percentiles. The red dots are the number of pairs contributing to the packet loss measurements. Spreadsheet |
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The minimum RTT to Peshawar and to Islamabad (left hand graph) appears to have reduced dramatically after April 2010. This is partially due to bringing on new hosts that have lower RTT between them. In April there was a factor of 2 increase in the number of host pairs (this is seen in the middle and right hand graphs).
Throughput
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We derive the throughput from the loss and RTT measurements as _throughput = 1460*8\[bits\]/(RTT\[msec\]*sqrt(loss)) kbits/s. _ |
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Median derived throughput (blue line) with the 25% and 75% seen from SLAC to hosts in Pakistan from Dec 2003 - Dec 2010. The number of hosts being monitored in Pakistan is seen in the brown line. Spreadsheet | Derved throughput between Pakistani region in 2010. Spreadsheet |
The derived throughput seen from SLAC in the graph on the left, has increased by roughly a factor of 2 in 5 years. Within Pakistan (graph on the right) the throughput to Quetta is the poorest, followed by Karachi. Since mosts
Mean Opinion Score (MOS)
The telecommunications industry uses the Mean Opinion Score (MOS) as a voice quality metric. The values of the MOS are: 1= bad; 2=poor; 3=fair; 4=good; 5=excellent. A typical range for Voice over IP is 3.5 to 4.2 (see VoIPtroubleshooter.com). In reality, even a perfect connection is impacted by the compression algorithms of the codec, so the highest score most codecs can achieve is in the 4.2 to 4.4 range. Using the RTT, loss and jitter we derive the MOS.
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