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Und wieder hat Deutschland sein neues "Littleton". Wie an dem aus Michael Moores Film "Bowling for Columbine" bekannten Ort, an dem zwölf Schüler ihr Leben verloren, stürmte Sebastian B. am 20. November 2006 seine ehemalige Schule in Emsdetten. Bewaffnet mit vier Gewehren und drei Rohrbomben schoss er um sich. Rund 30 Menschen wurden verletzt, drei davon schwer. Der 18-jährige Amokläufer tötete sich noch im Schulgebäude selbst. Ein Kommentar über die Hintergründe.

Die Ehe wird erst beschlossen, dann geschlossen, in beiden Fällen von der Familie. Die Verheirateten haben kein Wort mitzureden. Nach ihren Gefühlen fragt niemand. Es geht um Ehre, um Tradition, um Geld. Allein in Deutschland werden laut Terre des Femmes jährlich 30.000 Zwangsehen geschlossen.

Die Umschau ist das älteste, regelmäßig erscheinende Magazin im deutschen Fernsehen. Die Sendung hat eine bewegte Geschichte: Das einstige DDR-Wissenschaftsmagazin, das mit revolutionären Themen Furore machte, läuft heute als Wirtschaftsmagazin mit Schwerpunkt Ostdeutschland im MDR . Die Zuschauer sind ihm treu geblieben.

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This is not only a H.323 topic, but since H.323 also uses TCP connections, it applies to H.323 as well:

To detect network errors and signaling connection problems, you can enable TCP keep alive feature. It will increase signaling bandwidth used, but as bandwidth utilized by signaling channels is low from its nature, the increase should not be significant. Moreover, you can control it using keep alive timeout.

The problem is that most system use keep alive timeout of 7200 seconds, which means the system is notified about a dead connection after 2 hours. You probably want this time to be shorter, like one minute or so. On each operating system, the adjustment is done in a different way.

After settings all parameters, it's recommended to check whether the feature works correctly - just make a test call and unplug a network cable at either side of the call. Then see if the call terminates after the configured timeout.

Linux systems

Use sysctl -A to get a list of available kernel variables
and grep this list for net.ipv4 settings (sysctl -A | grep net.ipv4).
There should exist the following variables:

net.ipv4.tcp_keepalive_time:   time of connection inactivity after which
                               the first keep alive request is sent
net.ipv4.tcp_keepalive_probes: number of keep alive requests retransmitted
                               before the connection is considered broken
net.ipv4.tcp_keepalive_intvl:  time interval between keep alive probes

You can manipulate with these settings using the following command:

sysctl -w net.ipv4.tcp_keepalive_time=60 net.ipv4.tcp_keepalive_probes=3 

    net.ipv4.tcp_keepalive_intvl=10

This sample command changes TCP keepalive timeout to 60 seconds with 3 probes,
10 seconds gap between each. With this, your application will detect dead TCP
connections after 90 seconds (60 + 10 + 10 + 10).

FreeBSD and MacOS X

For the list of available TCP settings (FreeBSD 4.8 an up and 5.4):

sysctl -A | grep net.inet.tcp

net.inet.tcp.keepidle - Amount of time, in milliseconds, that the (TCP) 
connection must be idle before keepalive probes (if enabled) are sent.

net.inet.tcp.keepintvl - The interval, in milliseconds, between 
keepalive probes sent to remote machines. After TCPTV_KEEPCNT (default 
8) probes are sent, with no response, the (TCP)connection is dropped.

net.inet.tcp.always_keepalive - Assume that SO_KEEPALIVE is set on all 
TCP connections, the kernel will periodically send a packet to the 
remote host to verify the connection is still up.

therefore formula to calculate maximum TCP inactive connection time is 
following:

net.inet.tcp.keepidle + (net.inet.tcp.keepintvl x 8)

the result is in milliseconds.

therefore, by setting
net.inet.tcp.keepidle = 10000
net.inet.tcp.keepintvl = 5000
net.inet.tcp.always_keepalive =1 (must be 1 always)

the system will disconnect a call when TCP connection is dead for:
10000 + (5000 x 8) = 50000 msec (50 sec)

To make system remember these settings at startup, you should add them 
to /etc/sysctl.conf file

Solaris

For the list of available TCP settings:

ndd /dev/tcp ?

Keepalive related variables:
- tcp_keepalive_interval - idle timeout

Example:
ndd -set /dev/tcp tcp_keepalive_interval 60000

Windows 2000 and Windows NT

Search Knowledge Base for article ID 120642:
http://support.microsoft.com/kb/120642/EN-US

Basically, you need to tweak some registry entries under
HKEY_LOCAL_MACHINESYSTEMCurrentControlSetServicesTcpipParameters

I am fascinated with the success of the Amazon Echo. A company founded on selling books has worked very hard to become a hardware powerhouse and I think they achieved that goal with the Amazon Echo. I bought an Echo to play with home automation but when Amazon posted instructions on how to build your […]

I had to get an Arduino IDE up and compiling on a Kubuntu 18.04 install. In order to not forget what I did, I made this little post. This is not super detailed but it should get the job done. Grad the 64-bit version of the Arduino IDE (or the 32-bit version if you absolutely […]

Long Term Life Tips: Top 5 Regrets People Make on their Deathbed:

An astonishing “top 5 list” blog comes to us via longtermtips and I’m pleased to say I’m pretty sure I won’t have any of these regrets when my time inevitably comes.

By Bronnie Ware (who worked for years nursing the dying)

For many years I worked in palliative care. My patients were those who had gone home to die. Some incredibly special times were shared. I was with them for the last three to twelve weeks of their lives.

People grow a lot when they…

Go read. It’s worth it. Then think on it.

In a couple of weeks time, it will be the first anniversary of a 35-year old intellectual killing himself on the steps of a church on the Harvard campus.

I discovered Mitchell Heisman’s “Suicide Note” via a concise article on responses to the story.

I’ve been reading “Suicide Note” since I found the article, on and off. Mitchell might have benefitted from an editor, but there is no doubt the work is philosophically an opus par excellence.

Nihilism is not my thing - I do not agree with his core philosophy that life is entirely without meaning - but the way he gets there, and some of the ideas he presents are wonderful. There are things to take away from it all that will likely resonate with me for the rest of my life - as works by all good philosophers have.

To this day, Wikipedia have repressed information about him based on a subjective rules that don’t recognise that the guy’s work is actually worth reading. I expect in due course academics will start to cite him, and that situation will change.

Out there is a growing movement to recognise him. There have already been calls from some - perhaps over-excited - individuals for him to be award a Nobel Prize in literature posthumously. I wouldn’t go that far, but I would encourage those who can deal with it to consider his work. 

The moment Steve Jobs’ and Apple’s work first came into my life was back in 2002. That first brush, I hated it. 

In time, I came to see him for the genius and pioneer that he was, and the work that Apple did - and does - as amongst the most extraordinary in the World today.

First some context:

In 2002, I was at the European BSD conference and Jordan Hubbard, founder of FreeBSD and then newly-employed release engineer at Apple, had secured for the “terminal room” a sponsorship from Apple which meant the room was full of the 2002 iMacs. The 2002 iMac was a little “alien” in that each machine was a dome with a flexible protruding screen. Installed on them was OS X, an operating system I had beta tested before its first release on an ancient iBook, and I had very mixed feelings about.

It was pretty. But was it really a Unix? The other developers of BSD Unix in the room needed very little convincing. The command line was Unix, but the desktop and applications on there were beautiful. It was what they dreamed a Unix should be. Many of them left that conference committed to buying Apple equipment and moving to OS X within the year.

I resented this “attack” on the community, but could see where they were coming from. It was - and remains - a key part of Apple’s renaissance: build great tools for developers and alpha-geeks, and in turn the developers will build an ecosystem that users crave. Instill in the developers an aesthetic and teach them a way to do the things they struggle with (human interface guidelines, for example), and they will reward you with loyalty.

In short: empower your customers, and they’ll empower you.

No technology firm had done this as successfully before as Apple were doing between 2002 and 2004.

By 2004, I had just about had it with the drain away from the community Apple had “caused”. On one mailing list I wrote a very angry email in response to somebody else’s request for configuration advice on their latest Apple laptop:

http://lists.freebsd.org/pipermail/freebsd-chat/2004-October/002684.html

“Yes, of course. My advice is that you sell your over-priced fashion-victim toy with it’s Fisher Price Unix installed, and use the money instead to buy yourself a top of the range Thinkpad. It will outperform it, run FreeBSD, not look out of fashion next season, has been built by a company that is truly committed to the open source movement and whose execs don’t patronise you by assuming you travel to work on a skateboard in cargo pants or worse, pander to your girlfriend’s idea of what a computer should be.”

Ashamed by my petulant anger, about six month later I decided to reconsider, step back and think about what they were doing in a wider scheme of the industry I was in. This was when I started to “get it”. It was when I could see what others lauded about Apple and its founders.

Within 14 months of writing that email I had acquired a 12” iBook. It was all I could afford at the time, and even then it was subsidised by the fact that I was working in a University faculty and so got a discount.

I immediately loved the fact I had a Unix machine with WiFi and Bluetooth that I didn’t need to spend a week configuring. I loved the software I could buy, and that all the open source tools I loved would work too. I loved the thought that had gone into developing that code underlying OS X. I loved the developer tools and Safari. I found myself thinking more and more about aesthetics and craftsmanship as part of what I do as a developer. Suddenly programming wasn’t just a dry science of mathematics and engineering: Steve’s ideas were getting to me through the product of his and Apple’s work.

Two things then happened like thunderbolts. 

First, I had found a copy of Steve’s commencement speech to Stanford in 2005.

Steve’s speech stuck with me. I had studied rhetoric, and was pleased by the simple construct he had used - a structure I would begin to notice he used in product announcements - but the content had hit me somewhere deep.

In it he talked about three things:

• Follow your intuition, because in hindsight the dots will join up. You can’t plan to be great, you just have to let the intuition guide you.
• Do what you love, and change things if you find yourself not enjoying life
• Death is inevitable. It’s coming. Deal with it as an agent of change, and don’t waste your life.

The second thing that happened around then, was that I discovered the Ruby programming language, a language that was designed to be beautiful and enjoyable for programmers to work with.

It astonished me.

I don’t think it would have done if by that point I had not started to “get” aestheticism in software, the Apple way. It’s no secret that the Ruby on Rails framework is developed almost entirely on Apple OS X machines. A Ruby conference is basically a hang-out of Apple fans. The two seem to go hand-in-hand together, just like how in 2002 it was Apple and the BSD guys.

Last night as I watched the speech again on YouTube (on my iPhone, natch), I realised I was connecting dots back, and in hindsight the impact this speech and this discovery had on me was immense.

Coupled with the discovery of Ruby, what happened next was perhaps inevitable, but still surprised me.

I went and started my own business.

I had always wanted to, but right there and then, something clicked, and I got rid of all the fear and doubt and realised that when I looked back on my life I wanted to be able to say that for a while at least I had been an “entrepreneur”.

I made the decision that I would not work on projects in that business I did not enjoy. I would only work on things that brought me joy: that is to say, I would only write code in Ruby. A brave choice in early 2006 when Rails had yet to reach v1.0 and Ruby was still considered a “toy” language by many.

I had no money, no client roster, and survived the first six months coding away on that tiny, slow little 12” iBook for friends who had piece work for me. I had never been happier.

I ate noodles and beans on toast, drank donated Guinness and chose to love my work. Working from home I would love waking late on a Monday morning, but I could never lie-in: I always wanted to just get started.

I spent the next few years helping other businesses, talking about development as a craft, not just a science.

I went into schools and told kids that learning how to write beautiful software was the most powerful skill you could cheaply acquire in this generation. Like me, they could come up with an idea and with a laptop and internet connection share it with the World in a weekend.

In the years since, I have helped dozens of start-ups, spoken to thousands of teenage children (and hopefully inspired a few to give programming with an artistic flair a go), and changed my life substantially.

I am not the same man I was in 2005. The depression and anxiety I had suffered prior to then have more or less gone. I have a brilliant relationship with an amazing girl who I consider to be my best friend, and I do work that makes me excited almost every day.

The decisions I made in those few months in 2005 and early 2006, looking back, are what made me who I am today.

I had to call time on my main business in 2010 partly because I was finding myself looking in the mirror and not looking forward to the day ahead any more - just like Steve had said, I decided I needed to change something. As sales had dried up I realised I was doing something I no longer enjoyed.

I then turned down one job offer for another on a quarter of the salary because it felt right, it felt like more interesting work and ultimately I knew it might lead to an exciting adventure I had dreamed about.

Today I work on an amazing product with brilliant people and finding myself learning new things every day.

Looking back I realise I have developed a new sense of intense curiosity. I will wander in my work, inquisitively poking whole areas I know little about. I read more, listen more and learn more. I teach where I can, I play, and I explore.

I realise that my time on this little rock is limited, and I try and make sure every day I do something that makes me smile.

In hindsight then, Steve’s words and work have had a substantial impact on who I am today professionally. Because that impact made my work more joyful, pleasant and fulfilling, in turn, his words and work have made my life better than it would have been without his impact.

“This was a very typical time. I was single. All you needed was a cup of tea, a light, and your stereo, you know, and that’s what I had.”

It’s all the more impressive because according to “the rules” society is meant to work by, he should have been another liberal arts wash-up. As I said on Facebook earlier:

“I don’t think the economically right-wing anywhere - US, UK, Eurozone, China, anywhere - would be able to deal with the idea that the largest company on the planet was founded by a Buddhist counter-culturalist of complex family origins who made decisions based on intuition, aestheticism, love and curiosity.

Yet, it makes perfect sense to me.”

I never met him, never got close to knowing him the way that his friends and family did, or even his colleagues, but in my own way I learned to love him. His impact will be with me for the rest of my life, and late last night as the news broke here in the UK, despite it being on the cards for a while, the news came as a shock and I had to hold back the tears.

His critics’ words (and there are many!), sound very much like my own before I “got it”. Right now - today - though, it is petulant, angry, juvenile scribbling, and unworthy of any mature grown-up, given it is less than 24 hours since his dying.

Some call him a fascist, others a megalomaniac. In essence all he was trying to do was produce the best - and most human-friendly - technological products humanity was capable of producing right now. He did so within the rules shareholders gave him along with their money, because after being fired once, he didn’t want to mess up and be fired again. As ever, he exceeded their expectations and produced a company larger than any other on earth in terms of market capitalisation.

When you have a vision, as long as nobody gets hurt along the way, there’s no harm in following it ruthlessly. That’s what he did.

Some point to the fact that he didn’t donate much to charity in his life time, but I’m quietly confident that is because he didn’t want the ego stroking whilst he was still alive, and in coming years and months his wealth will quietly reach parts of the World that need it. He felt that shareholders’ money was their, and he shouldn’t give it away. He felt the best way he could help the World was by empowering as many people as possible. There’s no real shame in that. And in that, he was immensely successful.

He was also a subversive, and this is a point that his critics miss - or point to - the most. Biologically he was a half-Syrian Muslim, which when acknowledged in the last decade caused the conservative right in the US a huge problem: was the leader of the hottest thing on Wall Street one of them? They needn’t have worried - he’d discovered Buddhism many years ago. Adoptively he grew up to be a counter-culture Bay Area “hippie” and counter-culture type that worried some in the establishment even more.

His critics point to the consumerist message of Apple, without realising its founding principle was to go against the grain and to help people push further than the establishment wanted them to. The fact that he was able to make a living - a good living - as reward for that vision should not be seen as a fault or flaw.

Those unfamiliar with this background with questions to ask might want to start here. It might change your mind about him.

He wasn’t perfect. Nobody is. But regardless, he was an inspiration to millions who right now are working at building the next generation of technology. He showed us what we were capable of when we tried, and his death some 20-30 years “before his time” shows what a great leveller pancreatic cancer can be. So, if you are a critic: please shut the hell up and let us deal with paying tribute to him in our own way. You’ll reap the benefits as we march forward, inspired by his vision, into giving you the technology you deserve to make the World a better place.

I genuinely believe those who hate him haven’t given him - specifically what lay beneath his vision - a chance, in the same way I hadn’t.

The moment I did though and started to use the tools he and his company produced the way they were designed, my life got better and my attitude to what I wanted to do with my life improved.

I can’t think of another businessman I could say that about. I can’t think of another businessman anybody will be able to say that about when they die.

As I watched that commencement speech another time, the words were as fresh and as poignant as ever. His final few words seem particularly appropriate to me today, and so I will leave you with them. You may love him, you may hate him, but you can’t disagree that his vision was sharp, and worth sharing.

My thoughts and condolences today are of course with his family, his friends and colleagues, and all who were impacted by Steve from a distance the way I was. Steve was an amazing man, who inspired so many and has changed the World for the better, forever.

No one wants to die. Even people who want to go to heaven don’t want to die to get there. And yet death is the destination we all share. No one has ever escaped it. And that is as it should be, because Death is very likely the single best invention of Life. It is Life’s change agent. It clears out the old to make way for the new. Right now the new is you, but someday not too long from now, you will gradually become the old and be cleared away. Sorry to be so dramatic, but it is quite true.

Your time is limited, so don’t waste it living someone else’s life. Don’t be trapped by dogma — which is living with the results of other people’s thinking. Don’t let the noise of others’ opinions drown out your own inner voice. And most important, have the courage to follow your heart and intuition. They somehow already know what you truly want to become. Everything else is secondary.

When I was young, there was an amazing publication called The Whole Earth Catalog, which was one of the bibles of my generation. It was created by a fellow named Stewart Brand not far from here in Menlo Park, and he brought it to life with his poetic touch. This was in the late 1960’s, before personal computers and desktop publishing, so it was all made with typewriters, scissors, and polaroid cameras. It was sort of like Google in paperback form, 35 years before Google came along: it was idealistic, and overflowing with neat tools and great notions.

Stewart and his team put out several issues of The Whole Earth Catalog, and then when it had run its course, they put out a final issue. It was the mid-1970s, and I was your age. On the back cover of their final issue was a photograph of an early morning country road, the kind you might find yourself hitchhiking on if you were so adventurous. Beneath it were the words: “Stay Hungry. Stay Foolish.” It was their farewell message as they signed off. Stay Hungry. Stay Foolish. And I have always wished that for myself. And now, as you graduate to begin anew, I wish that for you.

Stay Hungry. Stay Foolish.

Thank you all very much.

This is not an exciting story, despite the title. But it’s true. And it happens to dozens of people every day, and is the reason why getting to work in London can sometimes take so long.

First, let me explain that this is not a story of me causing a fire alarm to go off, for anti-terrorist police to close a station for half an hour, or some dramatic incident that has left TfL seeking an ASBO against me.

This is a story that starts with a strap of a backpack. This strap, in fact:

This morning I caught a tube from Baron’s Court on the District Line heading East. Normally I change at South Kensington for a Circle Line to Moorgate, or hop off at Mansion House and walk up to the office through the City. This morning I had decided to stay on the District line until Blackfriars, and change there for a Circle line. It’s a man’s perogative, etc.

The tube this morning was very busy. During the Olympics it has on the whole been very quiet, but this morning it was the normal 8:15-8:45am peak time crush. I was stood right next to the door at the very front of the train, crushed in by about 20 other souls attempting to share the exact same square foot I was stood on.

At Victoria, as is often the way for the District Line, a lot of hustling and bustling went on as people fought their way out to the platform, and others tried to struggle onto the train. After around a minute, the doors closed.

Except for the one next to me. Looking down, it was jammed on my bag strap.

Swearing, I attempted to free it. It was jammed solid because the hydraulic pressure of the door was pushing against it, but not with sufficient force for the door to close. The guy next to me tried to help. The guy on the platform waiting for the next train also tried to help. Neither of us could free it. Moving it simply led to the door moving along a bit, keeping the strap jammed.

Then the sound of hydraulics releasing was heard, all the doors on the train went to open, and the driver climbed out of the cab. The release of pressure had allowed me to unjam the strap, and recover it into the train. The driver confirmed we were all fine, climbed back into the cab, closed the doors, and off we went.

I apologised to those around me for delaying their journey, even though the total delay was perhaps 60-90 seconds.

Then realised everybody else on the train was delayed, too.

Then a thought about queuing theory and a little knowledge about how loaded that line is with train traffic at that time of the morning hit me: I had delayed tens of thousands of people.

Let me explain how I worked this out.

The District Line is composed of rather large gauge trains. I estimate that conservatively, each train is capable of shifting 2,000 people during peak times. There were certainly at least 2,000 people on my train this morning. Yes, they are only 6 carriages each, but each is certainly capable of holding nearly 350 people, and frequently does. I’m prepared to revise my numbers down if shown evidence.

In addition, the District Line platforms are not just used by the District Line. They’re also used by the Circle line between Gloucester Road and Tower Hill.

A glance at any “passenger information display” on a platform along this part of the network during rush hour will tell you the mean time between trains is 1 minute. There are close to 60 trains an hour going along that piece of track during rush hour.

Because my train was delayed for over a minute, this must have caused the train behind it to be given a red signal. This in turn would have caused the train behind that to be given a red signal, and so on. This buffer effect would be dampened beyond Gloucester Road going West, because the Circle and District lines diverge, giving more time for the red signals to switch to green, meaning scheduled trains would not have to stop in an unscheduled manner.

However, there would have been at least - I think - 5 trains affected by this delay in addition to my own. So we’re now up to 12,000 people in total delayed by my bag strap jamming a door.

It gets worse.

I changed at Blackfriars to a Circle line train. I got off the train I had delayed, waited 60 seconds on the platform and got on the Circle line train immediately following it, obviously now delayed. Cautiously making sure my bag was far from any doors, I boarded aware this train was now at least 2 minutes late against schedule.

Satisfied at the figure I had come up with of around 12,000 delayed passengers, I had assumed I had done no more damage, until we got to Aldgate.

The tube system has a tendency to expect passengers always want to be moving all of the time. Any delay of more than a minute or two at a station is always explained via an announcement. As we sat at Aldgate, the driver announced we were being “regulated” by a red signal. Looking out of the window, I could see an East-bound Metropolitan line train crossing our tracks to head across to East London.

That’s when it hit me. We were “out of position”. The train was a couple of minutes late, and so the guys running the switching had decided to give priority to the Metropolitan Line train, and we were held for approximately 4-5 minutes.

Whilst this part of the Circle line between Aldgate and Tower Hill was not as busy as the District/Circle line Tower Hill back West, a 4 minute delay was enough to ensure that the train behind us was going to be red signalled waiting for us to clear the platform.

That would be enough for the train behind that to be stopped.

And that would be enough for the train behind that to be stopped, which would probably be on the shared part of the network. That would be enough to cascade across the whole part of that line back to Gloucester Road, causing delays to perhaps 12 trains in total.

By now the numbers per carriage were down a little as we were close to the end of peak, but there was probably at least 1,000 people per train out there. Rounding up for the few more probably still around the Victoria area, and we’re up to 25,000 people.

There’s obviously some fudging here - people boarding trains at the “correct time” for them, did not realise the train they were getting was in fact the one after the one they had expected, and they did not suffer any delay. But I also suspect that this effect wasn’t dampened until after the peak ended at around 9:30am, and there were people who boarded their trains at 8:30am or before still out there (it can take 60 minutes easily to get from the “end” of a line into central London), whose journey had taken at least a few minutes longer than normal.

I doubt many noticed. I doubt anybody cares.

But it did make me think about how queueing theory applies to real world problems, and how when TfL moan about people keeping coats, bags and belongings clear of the doors, or jamming the doors to squeeze on rather than wait 6 more minutes for the next train, that they might have a point.

If you cause a train to be delayed, you are not simply inconveniencing the dozen or so people glaring at you in your vicinity. Or the people on the rest of the train who would glare at you if they could. But in fact, you have a cascade effect down the rest of the network. Tens of thousands of people delayed, because you didn’t want to wait 5 minutes. Or because you didn’t keep an eye on your belongings near the door.

I’ll certainly be more careful in future.

The next time I’m sat waiting for a signal to clear or am told that we are “being regulated”, I’ll wonder about whose bag or foot was to blame, and how the numbers of people flowing through London make butterflies flapping their wings on the network capable of huge cascading effects on transport infrastructure.

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