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3725 and Half Speed DS3

I have 3725's at each end of a full DS3 circuit and using iperf tcp test I am getting almost perfect half of the speed I should be, about 21-22Mbits.  The config is a very simple one, mostly defaults.  I have had the carrier test the circuit and they say it is running perfectly.  Help!

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3 REPLIES
Hall of Fame Super Silver

Re: 3725 and Half Speed DS3

Hello 1800petmeds,

are you doing TCP based tests or UDP based tests?

TCP based tests are affected by delay on the link. Try to use UDP flows for your test

Hope to help

Giuseppe

Community Member

Re: 3725 and Half Speed DS3

The latency on the pipe is 21ms.  Is there a way to calculate what the throughput should be?  I did try a UDP test and was able to fill the pipe but was told by several people that using UDP was not an accurate way to measure.

Hall of Fame Super Silver

Re: 3725 and Half Speed DS3

Hello,

in this datasheet

http://www.cisco.com/en/US/prod/collateral/modules/ps2797/ps4909/product_data_sheet09186a008010fba2_ps282_Products_Data_Sheet.html

C3725 is declared to support a single DS3 full rate.

>> did try a UDP test and was able to fill the pipe but was told by several people that using UDP was not an accurate way to measure.

It is exactly the opposite in this case UDP provides real forwarding capabilities (raw sending like traffic generators like smartbits, IXIA, router tester that are used in lab environments)

see

http://www.psc.edu/networking/projects/tcptune/

I had the some trouble during some tests years ago

It is a question of the TCP window size and delay. The TCP sender sends up to the window size and then has to wait an ACK from the receiver.

Using two parallel TCP sessions worked for me to demonstrate full use of available bandwidth

You can try this

Hope to help

Giuseppe

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