At 03:35 PM 1/27/2009, rkruz@xxxxxxx wrote:
I could use some hints.
I have a single link between host router/switches and host with
several miles between the routers (fiber optic). This is TCP/IP data.
I'd like to measure or analyze the quality of the link. I could
mirror a port with Wireshark on each router for both ends.
After reviewing Wireshark some notions I had are:
A) Checksum: Run applications from host, capture all data and analyse
captured data at far end for "Checksum" errors to create a close
estimate of Bit Error Rate by counting total packets to packets
w/Checksum errors. This with checksum offloading off.
Won't work. There are no modern switches that will mirror errored
frames (Cabletron MMAC's being the last ones that had this
option) So you will never see frame level errors. What you will see
are packet losses but that can happen due to queue starvation, buffer
overruns etc. What routers do you have? Assuming Cisco, you'll be
much better off doing sho commands "sho controller..." "sho int..."
to find pertinent error stats.
B) Round Trip Time (RTT): Send continuous ping from host, capture
lots of data and analyze RTT times. I could do this by exporting data
and using a spreadsheet to analyze. Does Wireshark do this already?
It doesnt look like the Service Response Time feature would do this.
There are RTT graphs and various other methods of getting this info.
But unless you suspect problems, you may be spinning your wheels
looking for too much information. If you have a Cisco router, you
could enable IP SLA and monitor the RTT. It's not accurate to
microsecond granularity, but I don't think you're looking for that
level.
Are you having some performance issues that you are trying to
resolve?
