Hi, I wonder why Iperf uses 1024*1024 for megabytes and 1000*1000 for megabits ?
I think, It should follow either 1000 * 1000 (International System of Units)convention or 1024 *1024 convention .
Any specific reason for such a methadology ?
Any ideas ?
Thx in advans, Karthik Balaguru
I couldn't say for sure, but in general, when you are talking about the speed of a line in kilobits per sec, megabits per sec, etc. Those lines are all measured in units of 1,000 (ie. a 64kbps circuit is
64,000 bits per sec, a 3mbps line is 3,000,000 bits per sec).Almost everyone still refers to a Metabyte as 1048576 bytes, drive manufacturers and the mebibyte people withholding.
They probably are just going with the normal convention that most people use.
Hi, Byte is originating from binary. When binary numbers are converted to decimal that is what happens. Binary 111111111 > Octal 777 >512 decimal
One thing to note is that Iperf uses 1024*1024 for Megabytes and 1000*1000 for Megabits.
Data formatting: (-f argument)
The -f argument can display the results in the desired format: bits(b), bytes(B), kilobits(k), kilobytes(K), megabits(m), megabytes(M), gigabits(g) or gigabytes(G).
Generally the bandwidth measures are displayed in bits (or Kilobits, etc ...) and an amount of data is displayed in bytes (or Kilobytes, etc ...).
As a reminder, 1 byte is equal to 8 bits and, in the computer science world, 1 kilo is equal to 1024 (2^10).
For example: 100'000'000 bytes is not equal to 100 Mbytes but to 100'000'000/1024/1024 = 95.37 Mbytes.
-- Jeff Liebermann jeffl@cruzio.com 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558
Meanwhile, at the alt.internet.wireless Job Justification Hearings, karthikbalaguru chose the tried and tested strategy of:
If it bothers you, you can always Use The Source, Karthikbalaguru :-)
On second thoughts, two different types of iperf floating around the internet could lead to much confusion when trying to compare speed test results.
-- (AIM:troffasky) (UnSoEsNpEaTm@ale.cx) 19:41:52 up 28 days, 23:36, 5 users, load average: 0.00, 0.03, 0.47 DIMENSION-CONTROLLING FORT DOH HAS NOW BEEN DEMOLISHED, AND TIME STARTED FLOWING REVERSELY
For some entertainment value, try TTCP:
and see how the results compare.
-- Jeff Liebermann jeffl@cruzio.com 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558
Really? I always thought that (in digital-land) since 1 Kbyte = 1024 bytes, a Mbyte is 1024*1024 = 1,048,576 bytes. And a Gbyte = 1024 (1k) mBytes =
1024^3 = 1,073,741,824 bytes. In other words, "digital" SI prefixes are a little bit larger than "engineering" ones, and conveniently follow power-of-two groupings (kilo=2^10, mega=2^20, giga=2^30, tera=2^40). Wikipedia seems to agree-- Mark Moulding
The real reason for this difference, which for some reason is rarely given, is because of address decoding. If you have a RAM chip, the memory cells are addressed by a binary address, so this leads naturally to blocks of memory that are powers of 2. One could design RAM chips with 1000 byte blocks say, but it makes the address decoding unnecessarily complex. Binary addressing is the most efficient method.
For disk drives the magnetic recording medium is linear, so the block size and cylinder/head/sector addressing can be arbitrary and not based on powers of 2. For convenience, the sector size is chosen to be a power of 2 to match how memory is arranged. Whether the overall storage size of a disk is quoted in SI or K is down to preference, but the manufacturers prefer the standard SI units.
For communications, the bit rate is determined by a clock, which is also somewhat arbitrary and doesn't need to be based on powers of 2. Therefore it is natural to use the standard SI units.
So in general, SI units are the preferred units. For directly addressed RAM chips (or ROM, Flash etc) a binary unit reflects the underlying layout, and gives an integral value. For storage media like disks, it's a gray area, and usage depends on choice. For communications and bit rates, SI units are normally used. In all cases, I recommend to use the IEEE binary prefixes (KiB, MiB etc) where appropriate to make it clear which unit is being used.
[snippety snip]
The more cynical among us may contend that usage depends on marketing.
Since, for a given quantity, an SI enumerated size is "bigger" than the equivalent binary size, which sells more? A 500 SI-gigabyte drive or a
466 binary-gigabyte drive? Or even a 480 binary-gigabyte? Who looks at the fine print?Some of us are old enough to remember when 64 Kbyte machines were the top of the line. Naturally, some advertising copy referred to
*their* machines as "65 Kbytes!" and a few even noted that 65,536 conventionally rounds to "66 Kbytes" and, yes, advertised them that way.-- Rich Webb Norfolk, VA
Interesting point of view :-) :-)
Karthik Balaguru
IMO, 'contend' should be 'believe'. :-)
And I think that the world would be a lot better off if most marketing types (along with a few other groups) suffered the fate of "The marketing division of the Sirius Cybernetics Corporation". :-)
-- ArarghMail912 at [drop the 'http://www.' from ->] http://www.arargh.com BCET Basic Compiler Page: http://www.arargh.com/basic/index.html To reply by email, remove the extra stuff from the reply address.
Okay, i posted it to iPerf mailing list. Pls find the responses in the below link -
Yes !
Okay, this seems reasonable ! Maybe, if iPerf sticks to one convention, it would be better.
Karthik Balaguru
Meanwhile, at the alt.internet.wireless Job Justification Hearings, karthikbalaguru chose the tried and tested strategy of:
I think it would be nice if it printed both types of output, to keep pedants happy :-)
-- (AIM:troffasky) (UnSoEsNpEaTm@ale.cx) 09:48:06 up 31 days, 13:43, 5 users, load average: 2.82, 1.06, 0.90 DIMENSION-CONTROLLING FORT DOH HAS NOW BEEN DEMOLISHED, AND TIME STARTED FLOWING REVERSELY
Except for floppy drives, where they split the difference and use
1024*1000-byte megabytes (e.g. 1.44MB = 1440 * 1024 bytes).
One of my customers used something called BRICKS, a GUI thing that was proprietary to some networking company.
It defaulted to UDP, leading to some performance numbers that the customer wanted to see matched by the production data which was running TCP.
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