MavEtJu's Distorted View of the World - 2009-10

tzsetup(8) changes
128 bit Operating Systems
Riverbed Blog Authorism
Distributed telephony done properly
Nintendo Wii hardware problems
How my brain works
DST is here again!
Project VP - 50% successrate

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tzsetup(8) changes

Posted on 2009-10-22 09:00:00
Tags: FreeBSD, zoneinfo

In the last couple of days I have scratched a couple of the itches I had with regarding to the timezone database on the FreeBSD Operating System, all related to the (in)ability to update /etc/localtime automatically or quickly:

  • After running tzsetup(8), it will keep the name of the select zoneinfo file in /var/db/zoneinfo.
  • You can automatically reinstall the last selected zoneinfo name (after an upgrade with cvsup or the misc/zoneinfo port) via the command tzsetup -r.
  • Support for installation of installation with the DESTDIR variable set via the -C option.
  • If you want to change your timezone and you know the zoneinfo name you want to change it to, you can do it quickly via the command tzsetup Australia/Sydney.

This feature is currently only available in FreeBSD -CURRENT, after the release of 8.0 I will merge it back into FreeBSD 8.0 and 7.0.

The port misc/zoneinfo and the installation script of src/share/zoneinfo do support these new features.

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128 bit Operating Systems

Posted on 2009-10-18 22:00:00
Tags: Numbers

While Microsoft is preparing Windows 8 to be 128 bit compatible, a lot of people went from "as if we ever need that much space!". 64 bit to address your Random Access Memory, that is indeed enough (for now), but as a Storage Offset number it is nearly there: The terabyte harddisks already need 41 bits offsets!

bits addressable space
 1                   1 byte
 2                   2
 3                   4
 4                   8
 5                  16
 6                  32
 7                  64
 8                 128
19                 256
10                 512
11                1024	kilobyte
12                2048
13                4096
14                8192 <- memory of my first computer (Philips P2000T, 1982)
15               16384
16               32768
17               65536
18              131072
19              262144
20              524288
21             1048576 megabyte <- memory of my first "own" computer (AT 286, 1992)
22             2097152
23             4194304
24             8388608
25            16777216
26            33554432 <- my first harddisk in 1992.
27            67108864
28           134217728
29           268435456
30           536870912
31          1073741824 gigabyte <- memory of my computer in 2001 (p6)
32          2147483648
33          4294967296
34          8589934592
35         17179869184
36         34359738368
37         68719476736
38        137438953472
39        274877906944
40        549755813888
41       1099511627776 terabyte <- Fits on one single harddisk in 2008 for AU$ 130
42       2199023255552
43       4398046511104
44       8796093022208
45      17592186044416
46      35184372088832
47      70368744177664 <- for US$ 7,867 (Backblaze, September 2009)
48     140737488355328
49     281474976710656
50     562949953421312
51    1125899906842624 petabyte
52    2251799813685248
53    4503599627370496 <- Internet Archive in March 2009
54    9007199254740992
55   18014398509481984
56   36028797018963968
57   72057594037927936 <- Addressable in a 64 bit offset
59  144115188075855872
58  288230376151711744
59  576460752303423488
60 1152921504606846976 exabyte
61 2305843009213693952
62 4611686018427387904
63 9223372036854775808

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Riverbed Blog Authorism

Posted on 2009-10-12 22:00:00
Tags: Riverbed

Guess what! After a "Social Media Introduction Course" last week, today I've been approved as an author for the Riverbed Blog Website.

I still don't know what the first article will be about, but I will give it my best try (Did you expect anything else here?)

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Distributed telephony done properly

Posted on 2009-10-12 19:00:00
Tags: Asterisk, Voice over IP

Recently I have been involved in the design and installation of a global VoIP telephone system and learned a few valuable lessons.

The call-flow design and requirements were as follows:

  • Every office had its own unique four-digit number range.
  • Every office has its own PSTN connection, either a handfull of BRIs or a big PRI.
  • Calls to a local number or national number go out via the local PSTN connection.
  • Calls to an international number should go, if possible, via the IP network and then via their local PSTN. If it wasn't possible, just deliver it via the local PSTN.

So far nothing spectacular, but the issues came when mapping calls on the network.

Normally people differentiate between internal and external calls by dialing the 0 (or 9 if you are stuck with an American based PABX, or 91 if you want to make a long distance call in the USA) before dialing the local number. After the 0, you more or less have captured a channel on the PRI and are able to call anything via that, local or national or international as long as you play via the rules of that PSTN. For example in Sydney, Australia: You can dial an eight digit local number, a ten digit local number or a ten digit national number. And if you prefix your call with a 0011, you end up on an international call.

On a distributed telephone system connected to various PSTNs, this will be a nightmare for the people to remember (0, 0011, 86 plus a string of numbers for China) which has to be translated by the PABX to +86 plus a string of numbers which has to be send to the PABX in China so it knows how to translate it back to the a China local number etc etc etc. Both a nightmare for the users and for the PABX maintainers, plus a nightmare for the travelling salesman.

So, instead of having a single prefix for an external line for a local or national call and an international call, let's split it: Prefix local or national calls with a 0 and make the international access an *. Yes, that's a * because it looks most like the international prefix +. So the PABX maintainers now know when to handle local calls and national calls.

The only tricky part is left over with the international calls, but it is less tricky than what it was. Instead of having to write a different parser for for each country to figure out when an international call is placed, they just check for the * prefix: No check of 0,0011 in Australia, an 9,011 in the USA, 0,00 in Europe, just check for the *. Next is to map of the next one, two or three numbers on the remote destination telephone system, which we just send their national call telephone number and wait for it to be connected.

So, if you have enough local offices, you will be able to call a lot of international telephone numbers for the cost of a national telephone call!

So no more 9,0011 1 415 123 4567 to call, just *1 415 123 4567! It will save money (It will be a cheap local call for the telephone system. Or a free call if the destination is a free number), it will reduce the number of buttons to press (9,0011 -> *) and it will prevent from making silly counting mistakes (missing 1 in the string of numbers to be pressed).

The whole system was implemented on the open source PABX Asterisk and a central monitoring / configuration server which kept track of which international prefixes needed to be forwarded to which telephone system. The implementation showed that its fail-safe design worked as expected when the office in Germany lost its internet connectivity for a three days and nobody complained that their calls to Germany didn't work anymore.

The overal telephone bill got reduced to 20% of the original cost, having the whole system paying for itself it as little as eleven months! (Although we still have three months to go :-)

So: Stop thinking about local calls and national calls and international calls, only think about local / national calls and international calls. Don't think about local international call prefixes, handle that on the PABX. International calls should be routed to remote PABXs which handle it locally. And only if a remote call can't be completed due to no free PRI channels or the remote PABX not being reachable, then handle it locally.

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Nintendo Wii hardware problems

Posted on 2009-10-07 12:30:00
Tags: Happiness, My Computers, Electronics

Last weekend Hanorah managed to break the Nintendo Wii: Forcing a second DVD into the chassis kind of ruined it for everybody. On its own this isn't a big issue, but considering that this month everybody in the family got addicted to Super Mario Galaxy, the tensions in the house rose faster than a couple of neighbouring countries with old wounds and money to spend on armies.

As usual, fixing this thingie seemed impossible. This guide on how to disassemble your Nintendo Wii talked about a tri-wing screwdriver (which I didn't have (but found in a shop in Bankstown)) and a normal small screwdriver.

Thanks to the above mentioned guide, I knew which screws to unscrew. Three minutes later I had found the problem (some metal bars of the disk lifting mechanics were bended) and rectified the problem. The disk spinned again!

I had removed a total of 20 screws, in six different shapes and sizes. In the good engineering tradition I managed to put the Nintendo Wii back in into its original shape leaving seven screws on my desk which didn't properly fit in any of the holes currently still unoccupied. And this metal cover also didn't make it back into the box... Nintendo, please reduce the amount of different screws because this is just bad design.

Anyway, I'm off to collect Star Bits and Stars and Grand Stars, because Bowser still has Princes Peach in his captivity!

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How my brain works

Posted on 2009-10-05 09:00:00
Tags: Memories, TV

With the move to Australia I have learned a particular thing about my brain: I can't remember names without seeing them written down. This presents itself mostly when watching television or movies: The names of persons (an overal problem), but also about medical issues (Skully in the X files, House), city names and star systems (Star Trek :-).

Last week I was reminded about this when discussing the latest episode of The United States of Tara: I didn't kow the names of any of the characters except for Tara. I know there is a husband, a son and a daughter (and on the side line a sister, a fast-food shop-manager, a boyfriend of the son and a psychiator), but I don't know any of their names. Neither the name of any of the personages Tara transforms in (except for Buck, which is a name I saw in the subtitles of Kill Bill).

I have seen numerous episode of The Bill (UK Police series), but I won't be able to name any of the characters in there. I have seen numerous episodes of House but can't name his colleagues or female boss.

This issue has never been a problem when I lived in the Netherlands, because all the foreign television series and movies are subtitled. So I know all the names of the people in Star Trek and Babylon 5, and I know part of them in Battlestar Galactica (Starbuck, Apollo (is he in the new one?), Boomer and Adama because they were in the old series which I saw with subtitles) but the name of the president or the second in command on the Galactica or the name of the scientist are all unknown to me.

That didn't mean that having the BBC was useless for me, thanks to the subtitles on the Teletext system "behind" the broadcast I was able to follow everything.

So, what does this leave for me in Australia? Not much, there is no Teletext system on the normal channels and there is only one channel, SBS, which has subtitled movies and series (because they are non-english). Before the re-run of every episode of Dr Who and Torchwood I read up on the TARDIS Wikimedia website to make sure I know who is who this time.

At least I know the limitations and the workarounds, but it's very tricky sometimes!

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DST is here again!

Posted on 2009-10-04 17:45:00
Tags: Rant, Happiness, DST

For the next six months, we will have DST in large parts of Australia again. The blogosphere is full with people who don't like it (for the right or wrong, the good and dumb reasons) and are under the impression that their opinion on this issue is important. See also Parkinson's Law of Triviality and the example of the Colour of the Bikeshed.

I for one am happy with the extra hour of daylight.
My two children wake up when the sun starts to shine (which was at 05:30 this week, making me wake up two hours before my train leaves for work (my boss doesn't allow me to start earlier)), this will give me a less reasonable time I get woken up. And it gives me one extra hour of sunlight when I come home from work, I can't wait until we have dinner outside again!

Give me the DST time of days all of the year!

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Project VP - 50% successrate

Posted on 2009-10-04 17:30:00
Tags: Project VP

After two months a quick status update: The beetroot looks fine, we will hopefully have three rows of beetroot in a couple of months. The carrots is a full failure: Of the seven rows, only ten plants came up. So today I aborted them all and started with a new batch of seeds. We also fertilized it with a full year worm-farm output, which will hopefully kickstart the process again.

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