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
  • 2

Accepted Solution

ibanez7 earned 0 total points
Comment Utility
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

Comment Utility
still no answer or help so i wil close the question

Featured Post

Enabling OSINT in Activity Based Intelligence

Activity based intelligence (ABI) requires access to all available sources of data. Recorded Future allows analysts to observe structured data on the open, deep, and dark web.

Join & Write a Comment

New Server  was moved from behind Router R2 f0/1 to behind router R1 int f/01 and has now address But we want users still to be able to connected to it by old IP. How to do it ? We can used destination NAT (DNAT).  In DNAT…
The Cisco RV042 router is a popular small network interfacing device that is often used as an internet gateway. Network administrators need to get at the management interface to make settings, change passwords, etc. This access is generally done usi…
After creating this article (, I decided to make a video (no audio) to show you how to configure the routers and run some trace routes and pings between the 7 sites…
After creating this article (, I decided to make a video (no audio) to show you how to configure the routers and run some trace routes and pings between the 7 sites…

744 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question

Need Help in Real-Time?

Connect with top rated Experts

17 Experts available now in Live!

Get 1:1 Help Now