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How fast is your Net?

So, as I have been trying to make a copy of my ReadyNAS NV+ data, I decided to take another look at my overall home network bandwidth between computers.

In a past survey of TCP benchmarking tools, I came across an excellent TTCP utility. Its simple, its easy to compile under Unix variants including MacOS, and there’s a pre-compiled binary for Windows platforms as well.

I thought I’d jot down a few notes before I forget them and have to figure it all out again.

First, lets remind ourselves of the maximum bandwidth for various types of connectivity, this table sums it up.

Medium Gbit/sec Mbit/sec Mbytes/sec bytes/sec
1 GigE 1 1024 ~128 134217728
Fast Ethernet 100 ~12 13107200
802.11g 19 ~2 2490368
802.11n 160 ~20 20971520

A couple of notes about the wireless specifications –

802.11g – Operates at a maximum physical layer bit rate of 54 Mbit/s exclusive of forward error correction codes, or about 22 Mbit/s average throughput.

802.11n – Operates at a maximum raw data transfer rate ranging from 54 Mbit/sec  to 600 Mbit/sec. Actually achieved speeds range from 130 to 160 Mbit/sec.

Ok, so now on to some quick reference configurations for TTCP and some of my real world numbers.

TTCP Parameters Bytes Sent Computed Duration Actual Duration Bandwidth
-l 65536 -n 2048 134217728 1 sec @ 1Gbit
-l 32768 -n 4096 134217728 1 sec @ 1Gbit
-l 16384 -n 8192 134217728 1 sec @ 1Gbit
-l 32768 -n 76 2490368 1 sec @ 19Mbit
-l 16384 -n 152 2490368 1 sec @ 19Mbit
-l 32768 -n 2280 74711040 30 sec @ 19Mbit 27.1 21.02 Mbit/sec
-l 16384 -n 4560 74711040 30 sec @ 19Mbit 27.8 20.45 Mbit/sec
-l 65536 -n 122880 8053063680 60 sec @ 1Gbit 68.2 900.63 Mbit/sec
-l 32768 -n 245760 8053063680 60 sec @ 1Gbit 68.3 899.59 Mbit/sec
-l 16384 -n 491520 8053063680 60 sec @ 1Gbit 133.3 460.64 Mbit/sec

For my tests, I was transferring between a Windows 7 Desktop and a Apple Mac-Mini with two switches between the two. All the numbers look pretty good in my book. For the wireless tests, I flipped off the Ethernet interface on the Mac-Mini to force it though the AirPort connected to an AT&T U-Verse Residential Gateway (which is 802.11g.)

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Categories: Computing
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