> Date: Sun, 10 Sep 2000 19:41:13 -0700
> From: Priscilla Oppenheimer <[EMAIL PROTECTED]>
> Subject: Re: what is wire-speed?
>
> Wire speed means the switch can pump out packets as fast as
the medium can handle. For example, the maximum packets-per-
second rate on 10-Mbps Ethernet with 64-byte packets is 14,880
packets per second. This comes from
Preamble = 64 bits
64 Byte frame = 512 bits
Interframe gap = 96 bits
Total = 672 bits
> Max packets per second on 10 Mbps Ethernet = 10,000,000 / 672
= 14,880 packets per second. A wire-speed switch, which most
are, would have no problem outputting that number of packets
per second.
>
> If you were to use 1024 byte packets, the number is 1197
packets per second on 10Mbps Ethernet.
>
> So, yes, vendors do tend to use 64-byte packets when quoting
their results, because it gives them better numbers.
>
> The other thing vendors do is quote the results when using
Gigabit Ethernet. That's where numbers like millions of
packets per second come from. In addition, if the vendor's
numbers are based on tests that output to multiple ports, then
you can get astronomical numbers, for example, 1.48 million
packets per second multiplied by 100 ports. As you can probably
> guess, this is a rudimentary way of specifying the
performance of a switch that is fraught with the over-
zealousness of marketing drones. &;-)
>
> Priscilla
Priscilla Makes some excellent points about switch performance
and performance benchmarks. A couple of extra notes on the
subject. There are actually some RFCs that cover this topic,
namely RFC 1944 (somehwat relevant), RFC 2285 (relevant), RFC
2289 (adds to RFC 2285). Both of the 2200 series RFCs are
titled, "Benchmarking Methodology for LAN Switching Devices."
Please keep in mind, they are informational, and as such do not
represent an Internet Standard. Additionally, there was an
excellent Networkers brief that covered this very topic from
the bowels of Cisco's testing labs :-) It was pretty
informative and if anybody is interested, I can dig up the URL
for the presentation.
HTH,
Paul Werner
p.s. The definition of a 64 byte packet? - Ethernet
marketing packet :-)
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