How to use TTCP from router to router to test 100Mbps link?

Posted on 2009-04-07
Last Modified: 2012-05-06
I'm trying to find information on how to use TTCP and enter the right
information in order to calculate the speed of a 100 Mbps link. The test
will be  taken from router to router but am not sure on which settings (or
should i use default settings ex: nbuffers 2048 , buflen 8192 etc..)should
be used for a link at that speed (100Mbps)and how to calculate the readings
properly in order to get an accurate reading. I have found these documents
but am still a little confused on how to do this and get accurate results
and how to enter the right configurations and which numbers to use in the
calculation again for a 100Mbps link.
Here are the documents that i have checked:
 Using Test TCP (TTCP) to Test Throughput
 Network Performance Testing with TTCP
 Like i mentionned before the tests will done from router to router and not
 from router to pc.
 Thanks for any help with this issue.
Question by:ibanez7
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Accepted Solution

ibanez7 earned 0 total points
ID: 24098629
Hello again.
Since i am not getting a reply i figured i would add a little info in order to clarify a bit what i am trying to do.
We took readings using TTCP on cisco 2851 (routers at both sites, from router to router) to test the link and here are the results.
Note: i did change the addresses and used only the default configs while performing the tests.
I was the transmitter at first then on second test i was the receiver(again we used the default settings).
In the example below of the first test,  i used the results of my transmitted document with the results of the received document from the other end in order to perform the calculations.(is this correct?)

transmit or receive [receive]: trans
Target IP address:
perform tcp half close [n]:
send buflen [8192]: *****USE THIS NUMBER MULTIPLIED BY THE BUFFER NUMBER*** -----------|2048 BUFFERS X 8192 BYTES
send nbuf [2048]:   *****USE THIS NUMBER FOR BUFFER NUMBER CALCULATION***CORRECT?------|= 16,777,216 BYTES
bufalign [16384]:                                                                    
bufoffset [0]:
port [5001]:
sinkmode [y]:
buffering on writes [y]:
show tcp information at end [n]:

ttcp-t: buflen=8192, nbuf=2048, align=16384/0, port=5001  tcp  ->
ttcp-t: connect (mss 1460, sndwnd 4128, rcvwnd 4128)
ttcp-t: 16777216 bytes in 21460 ms (21.460 real seconds) (~762 kB/s) +++
ttcp-t: 2048 I/O calls
ttcp-t: 0 sleeps (0 ms total) (0 ms average)

transmit or receive [receive]:
*Apr  5 11:26:44.287: %LINEPROTO-5-UPDOWN: Line protocol on Interface GigabitEthernet0/0, changed state to up
perform tcp half close [n]:
receive buflen [8192]:
bufalign [16384]:
bufoffset [0]:
port [5001]:
sinkmode [y]:
rcvwndsize [4128]:
delayed ACK [y]:
show tcp information at end [n]:

ttcp-r: buflen=8192, align=16384/0, port=5001
rcvwndsize=4128, delayedack=yes  tcp
ttcp-r: accept from (mss 1460, sndwnd 4128, rcvwnd 4128)
ttcp-r: 16777216 bytes in 21460 ms (21.460 real seconds) (~762 kB/s) +++  ***USE THE REAL SECONDS FOR THE CALCULATIONS
ttcp-r: 0 sleeps (0 ms total) (0 ms average)                                          

2048 buffers * 8192 bytes = 16,777,216 bytes
8548 IP packets * 40 bytes of header = 341,920 bytes
Total data transmitted = 17,114,816 bytes     *****NOW ADD BOTH FOR A TOTAL*****  16,777,216 BYTES + 341,920 bytes  = 17,119,136 BYTES  
17,119,136 BYTES  * 8 bits/byte = 136,953,088 bits  
136,953,088 bits  / 21.460 seconds =   6,381,784.157 bits/second

6,381,784.157 bits/second / 1024 = Kbps
6,232.21 Kbps
6,232.21 Kbps / 1024 = Mbps
6.09 Mbps  ****THIS SHOULD BE A 100Mbps link but the speed on the interface is set at:       duplex full, speed 10
So i`m wondering is this what i am actually getting? or are my calculations way off track?or should i use different settings
instead of default settings when configuring the test?

Again thanks you for any help with this.

Author Comment

ID: 24149757
still no answer or help so i wil close the question

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