Test 3: Response Times & Packet Loss for Specific DNS Records

DNS Benchmark is great but it doesn’t allow you to run a query for the same specific DNS record repeatedly and record the response time and packet loss. A script like the below is required for that:

#List of Variables
$countiterations
$date
$startdatetime
$enddatetime
$numberofqueries
$dnsresponse
$timetaken

#Create Array List
$dnsresponsearray

#Create Array List Item
$arrayitem

#Initialize ArrayList
$dnsresponsearray = New-Object Collections.ArrayList 

#Defining Variable Initial Values
$countiterations = 0
$date = $(Get-date -format dd-MM-yyyy_HH-mm)
$startdatetime = $(Get-date -format dd-MM-yyyy_HH-mm-ss)
$numberofqueries = 20


#Loop To Collect all data

do {

$timetaken = measure-command {$dnsresponse= resolve-dnsname portal.office.com -server 192.168.1.1 -type A -dnsonly | Select-object -ExpandProperty IP4Address -ErrorAction SilentlyContinue} | select-object -ExpandProperty TotalMilliseconds -ErrorAction SilentlyContinue

#Initialize Array Item
$arrayitem = New-object PSobject

#Specify Array Item Values
$arrayitem | Add-Member -type NoteProperty -Name 'DNSResponse' -value $dnsresponse
$arrayitem | Add-member -type NoteProperty -name 'DNSResponseTime_in_ms' -value $timetaken




$dnsresponsearray += $arrayitem

#Clear Array Item Values for reuse
$arrayitem =$null

$countiterations++

#wait 30 seconds between queries
#start-sleep -s 30

} until($countiterations -eq $numberofqueries)

$enddatetime = $(Get-date -format dd-MM-yyyy_HH-mm-ss)
$dnsresponsearray | Export-Csv -Encoding Unicode $("C:\JSON-Scripts\dns-queries_" + $date + ".txt")
Add-Content $("C:\JSON-Scripts\dns-queries_" + $date + ".txt") $("_______________________________________________________")
Add-Content $("C:\JSON-Scripts\dns-queries_" + $date + ".txt") $("File started at " + $startdatetime)
Add-Content $("C:\JSON-Scripts\dns-queries_" + $date + ".txt") $("Number of queries: " + $numberofqueries)
Add-Content $("C:\JSON-Scripts\dns-queries_" + $date + ".txt") $("Number of successes: " + $dnsresponsearray.count)
Add-Content $("C:\JSON-Scripts\dns-queries_" + $date + ".txt") $("File ended at " + $enddatetime)

The script isn’t perfect – it works for short form DNS responses containing a single item called “IP4Address” but not all DNS servers respond in this manner. The below command is the main element:

$timetaken = measure-command {$dnsresponse= resolve-dnsname portal.office.com -server 192.168.1.1 -type A -dnsonly | Select-object -ExpandProperty IP4Address -ErrorAction SilentlyContinue} | select-object -ExpandProperty TotalMilliseconds -ErrorAction SilentlyContinue

“resolve-dnsname” is the powershell equivalent of the command line “nslookup” command, and measure-command monitors how long this takes to execute. Note that the “-dnsonly” switch ensures the results come from a DNS query not the local cache – to test the cache only use “-cacheonly”. The results from these two commands (filtered) are stored in a powershell array list. At the end of the script after the loop has run the “export-csv” command and “add-content” commands output the results into a file.