3725 and Half Speed DS3

Unanswered Question
Jan 13th, 2010
User Badges:

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!

  • 1
  • 2
  • 3
  • 4
  • 5
Overall Rating: 0 (0 ratings)
Loading.
Giuseppe Larosa Wed, 01/13/2010 - 05:41
User Badges:
  • Super Silver, 17500 points or more
  • Hall of Fame,

    Founding Member

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

1800petmeds Wed, 01/13/2010 - 05:44
User Badges:

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.

Giuseppe Larosa Wed, 01/13/2010 - 05:50
User Badges:
  • Super Silver, 17500 points or more
  • Hall of Fame,

    Founding Member

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

Actions

This Discussion