Simple network monitoring with ping
In the Spring of 2005 Comcast experienced a major DNS outage. Since then many Comcast users have switched to DNS servers that belong to Verizon and other ISPs. Comcast started taking a lot of flak from its competition upset by Comcast customers using their resources. Finaly, a year later Comcast networking gurus remedied the problem by introducing dynamic DNS. Or so they thought.
Since about late March of 2006 I’ve been having a lot of issues with my Comcast broadband. DNS was sluggish and the network was slow and unstable. Calling Comcast service department was a problem: I have Vonage VoIP that, naturally, uses my Comcast connection. Calling Comcast on my cell phone and spending my expensive Cingular minutes to listen to Michael Bolton while waiting for a service rep became very frustrating very quickly. So I turned to the good old US Postal Service.
Eventually, Comcast people contacted me and, as it turned out, they were well aware of widespread problems caused by their recent DNS changes. Still, they claimed that signal strength to my modem was good and the line was clean. Whatever that means. So I provided them with network performance data I collected over the past few days and theatened to file a BBB complaint. As if by miracle, a few hours later my network was fully functional.
Apparently, if you are a Comcast customer, simply paying your monthly bill is not enough to get service you’ve been promised. You also need to be a computer professional with a very big mouth. However, let’s not dwell on the unpleasant and instead consider the simple Shell script I used to collect and store network performance data produced by ping. MySQL was used to store collected data and GNUPlot was used to visualize it.
#!/bin/sh # April 8, 2006 # This script uses ping to monitor quality of network connection to # selected hosts and notifies the admin when packet loss ratio # exceeds defined thresholds. # PINGHOST www.comcast.net 204.127.195.15 # PINGHOST www.yahoo.com 216.109.112.135 # PINGHOST www.google.com 64.233.187.99 # PINGHOST www.mit.edu 18.7.22.83 MYSQL="/usr/bin/mysql" DBUSER="dbuser" DBPASS="password" DBNAME="netmon" LOST_PACKET_THRESHOLD=10 PACKET_SIZE=64 PACKET_COUNT=10 PING_INTERVAL=1 TIMEOUT=2 PING="/bin/ping" GNUPLOT="/usr/bin/gnuplot" cat /var/adm/bin/netmon.sh | grep PINGHOST | grep -v grep | while read LINE do NAME=`echo "$LINE" | awk '{print $3}'` IP=`echo "$LINE" | awk '{print $4}'` $PING -s $PACKET_SIZE -c $PACKET_COUNT -i $PING_INTERVAL -W $TIMEOUT $IP | egrep "packet loss|rtt min" | while read LINE2 do if [ `echo "$LINE2" | egrep -c "packet loss"` -eq 1 ] then echo "$LINE2" | awk '{print $6}' | awk -F'%' '{print $1}' > /tmp/netmon_packet_loss.txt echo "$LINE2" | awk '{print $1}' > /tmp/netmon_packets_sent.txt echo "$LINE2" | awk '{print $4}' > /tmp/netmon_packets_received.txt elif [ `echo "$LINE2" | egrep -c "rtt min"` -eq 1 ] then echo "$LINE2" | awk -F '/' '{print $5}' > /tmp/netmon_avg.txt echo "$LINE2" | awk -F '/' '{print $6}' > /tmp/netmon_max.txt fi done if [ -f /tmp/netmon_packet_loss.txt ] && [ -f /tmp/netmon_avg.txt ] && [ -f /tmp/netmon_max.txt ] && [ -f /tmp/netmon_packets_sent.txt ] && [ -f / tmp/netmon_packets_received.txt ] then DATE=`date +'%Y-%m-%d %T'` PACKETS_SENT=`cat /tmp/netmon_packets_sent.txt` PACKETS_RECEIVED=`cat /tmp/netmon_packets_received.txt` PACKET_LOSS=`cat /tmp/netmon_packet_loss.txt` AVG=`cat /tmp/netmon_avg.txt` MAX=`cat /tmp/netmon_max.txt` rm /tmp/netmon_packet_loss.txt /tmp/netmon_avg.txt /tmp/netmon_max.txt /tmp/netmon_packets_sent.txt /tmp/netmon_packets_received.txt echo "$DATE, $NAME, $IP, $PACKET_SIZE, $PACKET_COUNT, $PING_INTERVAL, $PACKETS_SENT, $PACKETS_RECEIVED, $PACKET_LOSS, $AVG, $MAX" $MYSQL -u$DBUSER -p$DBPASS $DBNAME < < EOF INSERT INTO pinger (datetime,hostname,ip_address,packet_size,\ packet_count,ping_interval,packet_sent,packet_received,\ packet_lost,response_avg,response_max) values('$DATE','$NAME','$IP','$PACKET_SIZE',\ '$PACKET_COUNT','$PING_INTERVAL','$PACKETS_SENT',\ '$PACKETS_RECEIVED','$PACKET_LOSS','$AVG','$MAX'); EOF fi done cat /var/adm/bin/netmon.sh | grep PINGHOST | grep -v grep | awk '{print $3}' | while read hostname do $MYSQL --column-names=0 -u$DBUSER -p$DBPASS $DBNAME << EOF > /tmp/netmon_gnuplot_${hostname}.dat SELECT hostname, datetime, packet_lost, response_avg, response_max FROM pinger WHERE hostname LIKE '${hostname}' AND DATE_SUB(CURDATE(),INTERVAL 3 DAY) < = datetime; EOF cat << EOF > /tmp/netmon_gnuplot_${hostname}.gnu set title '$hostname' set xdata time set key box set key bottom right set size 1.5,1.5 set xlabel 'Date' set ylabel 'Ping Response' font 'Arial,12' set autoscale set timefmt "%Y-%m-%d %H:%M:%S" set term png color set output '/WD120GB_01/htdocs/netmon/${hostname}_1.png' plot '/tmp/netmon_gnuplot_${hostname}.dat' using 2:4 title 'Packet Loss (%)' with linespoints, \ '/tmp/netmon_gnuplot_${hostname}.dat' using 2:5 title 'Average Response (ms)' with linespoints, \ '/tmp/netmon_gnuplot_${hostname}.dat' using 2:6 title 'Maximum Response (ms)' with linespoints EOF $GNUPLOT < /tmp/netmon_gnuplot_${hostname}.gnu > /dev/null done cat < < EOF > /WD120GB_01/htdocs/netmon/index.htm EOF cat /var/adm/bin/netmon.sh | grep PINGHOST | grep -v grep | awk '{print $3}' | while read hostname do hostname2=`echo "$hostname" | sed 's/\.//g'` cat < < EOF >> /WD120GB_01/htdocs/netmon/index.htm <a href="#${hostname2}" target="_self">${hostname}</a> EOF done cat /var/adm/bin/netmon.sh | grep PINGHOST | grep -v grep | awk '{print $3}' | while read hostname do hostname2=`echo "$hostname" | sed 's/\.//g'` cat < < EOF >> /WD120GB_01/htdocs/netmon/index.htm <img src="http://www.krazyworks.com/wp-admin/${hostname}_1.png" alt="" width="960" height="720" /><a name="${hostname2}"></a> EOF done cat < < EOF >> /WD120GB_01/htdocs/netmon/index.htm EOF rm /tmp/netmon_gnuplot* chown -R wwwrun:www /WD120GB_01/htdocs/netmon chmod -R 755 /WD120GB_01/htdocs/netmon
And the end result is a page on my Web server with several graphs showing network performance for the selected hosts. Here’s one of the graphs:
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