Subject: Latency and load

From: [email-masked] (Randy Forsland)
Date: Mon, 23 Aug 1999 09:31:06 -0800

I have another question regarding the Latency and Load issue. 

How many port pairs are you utilizing when running the latency test  ?? If you
were testing a 12 port switch ,for example, are you running the test on all 6
port-pairs simultaneously or are you only utilizing a single port-pair. I have
seen it done both ways by different test labs and I was wondering which is the
correct way.

Randy Forsland
Allied Telesyn Int'l

---

From: Steve Bell <[email-masked]>
Date: Mon, 23 Aug 1999 17:57:38 -0700

Randy,  FYI, when testing multi-port devices (switches) we
normally we do run our latency tests utilizing ALL port
pairs of the DUT.  This allows us to catch things like different
latency performance on different ports, due to (e.g.) "clustering" of
ASIC architectures.  e.g. many implementations cover 4 to 8 ports per ASIC,
so there is a different switching path (latency performance) between the
4-8 'local' ports, and the other ports in the switch (intra and inter ASIC).

With one recent SUT, at high loads we were seeing inconsistencies in the
latency measurements
which seemed to be somewhat randomly distributed (by port), probably
indicating some sort of
architectural limitation or resource starvation.  This sort of thing is a
red flag for us regarding
the performance of the DUT, which we would miss if only testing port-pairs.

-Steve Bell, SVNL
 www.svnl.com

-----Original Message-----
From: [email-masked]
[mailto:[email-masked]]On Behalf Of Randy Forsland
Sent: Monday, August 23, 1999 10:31 AM
To: [email-masked]
Subject: Latency and load

How many port pairs are you utilizing when running the latency test  ?? If
you
were testing a 12 port switch ,for example, are you running the test on all
6
port-pairs simultaneously or are you only utilizing a single port-pair. I
have
seen it done both ways by different test labs and I was wondering which is
the
correct way.

Randy Forsland
Allied Telesyn Int'l