[j-nsp] Latency FastEthernet & Testing with Anritsu, Agilent, SmartBits

[McCoy, Chris]

Hi Alex,

  I happen to work for Spirent, so I can't speak for the other companies.
SmartBits uses "LILO" (last in-last out) measurement for latency.  The
timestamp that is inserted at the end of the frame is based on the last bit
of the frame that egresses the test port and by the same token, the
timestamp is noted when the last bit of the frame enters another test port.
It then computes the difference.  Some companies use FIFO or LIFO (see
RFC-1242 section 3.8).  This could be the source of your inconsistent
results.

Chris M.

-----Original Message-----
From: Alex Kitschkiruk [mailto:juniper.m20 at gmail.com] 
Sent: Thursday, April 28, 2005 4:32 AM
To: juniper-nsp at puck.nether.net
Subject: [j-nsp] Latency FastEthernet & Testing with Anritsu, Agilent,
SmartBits


Hello everybody! I tested M20 (RFC 2544).
The results:
(Juniper M20, 4 Port FastEthernet, Average Latency, in microseconds)

128 Byte
------------------------------------------------------
NetStat   26 mcs
Anritsu MD1230B  20 mcs
Agilent N2X   48 (!!!) mcs (Min=32, Max=71)
Spirent SmartBits 600B  N/A (Min=26, Max=51)
------------------------------------------------------

1024 Byte
------------------------------------------------------
NetStat   100 mcs
Anritsu MD1230B  28 mcs
Agilent N2X   177 (!!!!) mcs (Min=106, Max=293)
Spirent SmartBits 600B N/A (Min=99, Max=289)
------------------------------------------------------

Which are correct? What is in specifications?

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