AN OPEN LETTER TO THE PARISH

The Catholic parish priest at Wells, Somerset is a burly man. His face used to be rather shiny - what we call 'baby-faced' - until he grew a beard which now makes him look somewhat like an Eastern Orthodox patriarch when he's dressed up in his robes. He freely admits to over-liking pie shops and has the grounded bonhomie typical of the ESTJ. The priest is a convert from Evangelical Protestantism and it shows.

Last week, as I reported in this bombshell, he spoke directly to the congregation about 'concerns focused on his own person' and suggested that if these were widespread he might resign. This week he reported that he would be staying after all: the 'Open Letter' below was distributed with the Bulletin.

As we understand it, the previous priest was forced out under mysterious circumstances. His replacement is obviously not finding things too easy - maybe there is a mysterious cabal in the local Catholic community which secretly comes to judgement and then begins its subterranean agitation: it's all a mystery to us.

I could believe that the priest's homespun homilies and literalist reading of the Bible might jar with an intelligent, sophisticated parish which expects its religion to be woven from allusion and metaphor. But trust me, Wells is not that kind of parish.

Anyway, here is what the priest had to say in his open letter today (slightly edited).

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AN OPEN LETTER TO THE PARISH

Dear Brothers and Sisters,

I want to take this opportunity to thank the parish for its response to my words last Sunday. I asked you to tell me whether I was “the problem” and you have told me. That now being an answered question, we can move on together. I am touched by and undeserving of your many kind words. I am truly sorry that, in the process, I have caused upset and anger by what I said. That was never my intention. Nor did I mean to make people fear that events are repeating themselves.

I need to say very firmly that events have not repeated themselves. There is no pastoral breakdown or falling apart. There is no problem between myself and the Pastoral Council. For good or ill, I am not my predecessor and that changes the complexion of things completely. Present difficulties are not insurmountable and offer us rich opportunities for growth.

...

I have to tell you what you already know - that I am not a perfect priest and aspects of my personality and thought processes are not always helpful. In these last few days, I have reflected on the sometimes flamboyant excesses of my outgoing nature. The Liturgy of the Church exists to enable the People of God to meet Him in a rich diversity of ways. I need to be aware that I can get in the way of that life-giving contact, if I am not careful. There is no place for a prima donna priest, entertainment or the cult of personality. I will try much harder in future by God’s grace to efface self and put on Christ in the offering of Sunday Mass.

I have a tendency to digress when preaching, which can be distracting and unhelpful. I cannot promise to eliminate this tendency, but I am aware of this aspect of who I am. I will attempt to stay focussed and to the point, but I crave your understanding of my faults and foibles.

...

Yours in Christ

Yves St Laurent cream

Yes, the famous Forever Youth Liberator cream has arrived, based on "Glycobiology". Apparently it emulates the effects of natural Glycans which regenerate the skin.

I expect to be monitoring progress over the next week. (Not on me!)

I've been working hard this morning on a client document - just surfaced for a breather.

An Ode to Clumper

Oh Clumper, you titan of sinew and bone
I bought you, not stole you, so don't run off home
I dismount, defend you and kill off your foes
I look but where are you now? God only knows!

Clare says "Too many 'I's" but Alex will appreciate this homage to a 1,000 gold piece nag in Skyrim.

"Back me or sack me!"

At the end of Mass this morning the priest asked us to sit, as he usually does, so he can deliver the notices. After a brief remark about a mistake in the Bulletin ("The Ecumenical Service will be at 6.30 this evening") he moved on to mention that "Some concerns have been expressed within the Parish."

I guess I was expecting some feedback on fundraising for the roof fund or the like. Far from it: what came next was truly astonishing. Here is what the priest had to say.

"Concerns have been expressed within the Parish, and of course we have to take concerns seriously. Particularly when the concerns are about me."

At this point the congregation noticeably stiffened.

"I hear the some people are concerned about the style of preaching from the altar. Well, I now need to know what the whole Parish thinks. If concerns are widespread then of course I will resign."

At this point you could have heard a pin drop.

"If the problem is confined to just part of the Parish, then other measures will be necessary. Now, please stand."

And with that there was the final prayer and hymn and the Mass was ended.

The priest delivered this bombshell in a perfectly matter-of-fact voice, without the slightest trace of emotion.

As we walked towards the newspaper shop I asked Clare whether this was normal behaviour for a priest. In a lifetime of Mass-attendance, she said, she had never heard the like.

As I write this with the Sunday afternoon light fading, Clare is playing online scrabble with Alex (who is in Reading), with Skype providing the voice channel.

"Are you winning, Clare?"

"Yes."

Google Sky Map

If there's one thing a smartphone has got to be good for, it's astronomy. In a flash of inspiration this evening I downloaded the free Google Sky Map app.

It's augmented reality: you stand outside and look at the stars, holding the phone in front of you. The phone knows its own orientation so you see the same night sky on the screen - but everything's named.

The constellations are drawn in and you can enter the name of an object (eg the Andromeda galaxy, M31) and the screen will point you to where it is (pretty much overhead after dinner this evening).

In other news, the next phase of my contract has started and I was huddled over a laptop for most of the day.

Now if I could only get some of that new Yves Saint Laurent Forever Young Liberator cream.

Crashing The Courtesy Car

I stood forlornly on the freezing forecourt, buffeted by icy gusts. Looking up at the leaden pre-dawn sky with its scudding dark clouds, I reflected that it did indeed look very much like a TV screen tuned to a dead channel. I pulled my coat tighter against the flurries of snow and walked into the service center.

I had booked my car in for its 30,000 mile service a few weeks ago. After completing the paperwork and handing over the keys, the guy behind the desk got around to the Courtesy Car, which I would need to continue on to work. But there was a catch.

‘If you happen to have an accident,’ he said, ‘There’ll be a $1,000 excess to pay. But if you hand over $10 for an insurance deal right now, that excess will be reduced to only $100.’

I was thinking furiously: so they want me to pay them $10 but is it really value for money? How likely is it, I thought to myself, that I’m going to crash their car today? But perhaps there’s a different, more informative question: what does this guy’s proposal tell me about the garage’s assessment of my chances of damaging their vehicle?

Let the crash probability be p. I have to start with the assumption that the garage has set the pricing on this offer so that they’re indifferent to whatever option I end up taking. This would be their rational position, so I’d end up paying the same expected amount to cover repair costs whether I took the offer or not.

Let’s equalize my expected outlay on both sides of the deal – this is the amount I spend times the probability of the accident happening. So:

1000p = 10 + 100p

recalling that I have to pay them $10 regardless in the second case.
So clearly p = 1/90.

This seems a rather high probability of crashing. Driving 270 days a year at this probability I would expect to have three crashes a year (I don’t). But of course, I don’t drive an unfamiliar courtesy car every one of those 270 days. I believe the chances of my crashing their courtesy car are considerably less than 1.1% but would I pay $10 to avoid a very remote risk of paying an additional $900?

They obviously expect a continuing cash-flow from risk-averse drivers with this deal!

With the car rocking under the impact of successive wintry squalls, I drove into the morning traffic without handing over any cash; amazingly, I didn’t crash that day. I was, however, considerably confused by the way the engine turned itself off every time I halted at traffic lights: something about combating global warming, I believe.

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This would have been my last "science feature" article for sciencefiction.com, had they chosen to use it. They evidently thought it was not 'SFnal enough' and I have to agree.

A modest proposal re: affordable child benefit

Clare asked me to publish her thoughts on affordable child benefit as follows.

"The issue of reducing the bill for child benefit is hotly debated in the media and I have a suggestion. Universal child benefit should be continued, with a modification which would reduce its cost. All parents currently receiving the benefit should continue to receive it in full: this would circumvent the issues relating to increasing poverty for existing large families.

New parents should receive the benefit for two children only, however.

Personally I found child benefit a very useful addition to family income but (like many others, I suspect) I would never have considered applying for any state aid which was not in the form of a universal grant."

When will we see the Kindle Fire in the UK?

I have decided I'm a convert to eReaders. It's incredibly convenient to order a book via the Kindle app and get it a few seconds later. There are other advantages these cold winter evenings: a dimly-lit secluded living room with the fire burning away merrily and Clare watching alpha-male Trevor Eve in "Waking the Dead" on DVD ... I can relax and read Lawrence Krauss's latest or Ian Mcdonald's remarkable The Dervish House which reminds me of our Andante trip to Istanbul.

But ... reading on a smartphone screen is just a little too constricting: I want the larger, Kindle-sized view of the page and I want backlit for that comfy gloom. So come on Kindle Fire, I promised myself I'd hold off to release 2 (never buy at release 1.0!) but now I'm not so sure. I hear rumours my plight will be resolved as early as the end of this month.

My contract has finished for the time being (it was for some preparatory work for the client) and the experience has sent me back to my "Voice Teletraffic Systems Engineering" book to produce this white paper. There may be a further phase of work: watch this space.

White Paper: Sizing WAN Access Links

A PDF version of this paper is available here.

Table of Contents

1. INTRODUCTION
2. USING THE POISSON DISTRIBUTION FOR TRAFFIC MODELLING
3. DIMENSIONING VIRTUAL CIRCUITS
    3.1 MULTIMEDIA STREAMING DATA
    3.2 NON-REAL-TIME DATA
4. TRAFFIC DIMENSIONING
5. NOTES

1. INTRODUCTION

Imagine an office, part of a multi-site company. It has 12 staff who undertake normal office activities: access their email (with attachments); download Word, PowerPoint and Excel files from the remote data centre; make multimedia calls from their desktop conferencing software. All this traffic needs to enter/exit their site on the Wide-Area Network (WAN) access link, so what capacity link do they require? This White Paper describes a process to work it out.

In the old days, networking was circuit-switched telephone calls. Suppose there were 12 desk phones for the 12 staff. If they all phoned at once, the access circuit would need to carry 12 voice channels (at 64 kbps each this would be a 768 kbps link). But what a needless expense: the chances of 12 simultaneous phone calls being made are vanishingly small in normal business.

Instead, a model is used to work out the probability of 0, 1, 2, 3, 4, 5, ... calls being made simultaneously. If the probability of making a phone call in the Busy Hour is 0.1 (a six minute phone call during that hour) then 12 users contribute 12 * 0.1 = 1.2 Erlangs of traffic. If we want no more than a 1% chance of someone getting an engaged tone when they try to dial, we turn to the Erlang-B tables. These tell us that we need to provide no more than 5 circuits on our access link: it’s certainly cheaper than provisioning 12 circuits.

The Erlang-B formula is the Poisson distribution modified to capture more life-like behaviour when someone calls and can’t get through. However, in the high-level modelling of this paper we will just use the Poisson distribution.

2. USING THE POISSON DISTRIBUTION FOR TRAFFIC MODELLING

Whether it’s multimedia conferencing or data traffic, it’s convenient to conceptualise it in terms of old-fashioned voice calls. Suppose there are a very large number of desk phones, n, and each phone has a probability of being in-use at a particular time of p. This means that if we inspect any phone at a random time, the probability of finding it in use when we look is p.

Given n phones, the expected number (i.e. the average number) of phone calls we expect to see if we take a random look is n * p. Call this number l.

Example: for our 12 people with their desk phones, if each has a probability of 0.83 of making a call at any moment (in the Busy Hour) then the expected number of simultaneous voice calls will be 1.

We would now like to know the probability, at a random moment, of observing k = 0, 1, 2, 3, etc simultaneous phone calls. This is what the Poisson distribution gives us: the formula is:

P(k;l) = (l^k/k!)e^-l where e is 2.71828... and k is 0, 1, 2, 3, etc. Here is the table for l=1.

Figure 1. Poisson distribution for l = 1 (l is the mean)

In this table k is indicating how many simultaneous phone calls and P(k;l) is the probability of seeing each value of k. if we add up the probabilities for all values of k, from zero to infinity we’ll get 1. As you see, the probabilities get very small, very rapidly.

Looking at this table, the probability of k = 0, 1, 2, 3 or 4 = 99.6%. So if we supplied 4 voice circuits, we’d satisfy the site’s phone needs 99.6% of the time. The remaining 0.4% of the time 5 or more people would be trying to call at the same time and some people would get the engaged tone.

In this example, the number of Erlangs was one (l = 1). In the Introduction we considered the case with 1.2 Erlangs and found we just needed an extra circuit (5 circuits) to give us the required grade of service.

Fine, you may say, but these days we don’t do circuit-switched voice, we do data:- streaming data and bursty data. This is true, but we can use the same method of analysis.

3. DIMENSIONING VIRTUAL CIRCUITS
3.1 MULTIMEDIA STREAMING DATA

Let’s return to the 12 people back at the office. Now they’re making multimedia call using a desktop conferencing system. Let’s suppose that they each make a multimedia call of ten minutes duration during the Busy Hour. So for each user the system is working 10 minutes out of 60, therefore with a probability of 1/6. So the mean number of simultaneous multimedia sessions, l, equals 12 * (1/6) = 2.

So now we can ask what is the probability of seeing k = 0, 1, 2, 3, ... simultaneous multimedia calls? Here is the Poisson table for l = 2.

Figure 2. Poisson distribution for Multimedia calls, l = 2

If we add up the probabilities of k = 0-6 we get: 99.55%. So if we supply enough bandwidth for six simultaneous multimedia sessions we will only encounter capacity problems if 7 or more people want to make calls at the same time. The probability of this is less than half a percent.

*** Bottom line: provision capacity for six simultaneous sessions ***

Let’s assume a multimedia session occupies 512 kbps = 0.5 Mbps. We will need this when we come to size the access link below.

3.2 NON-REAL-TIME DATA

What about the Word, PowerPoint and Excel downloads; the email attachments; the Internet pages? We proceed by turning these downloads into ‘calls’.

Suppose that each of our 12 users downloads 64 MB in the Busy Hour. If there is contention, TCP will simply slow down the download so let’s decide on a minimum rate we’re prepared to give users: say 1 Mbps each.

The second assumption we need to make is how many separate files get downloaded per user (a file download looks like a ‘call’) during the Busy Hour. Let’s assume 16 files per user spread over the data files, email attachments and Internet traffic. We’re assuming therefore that the average file is 64/16 = 4 Megabytes = 32 Megabits.

At 1 Mbps, the slowest speed we find acceptable, this will take 32 seconds. This file download has a probability of ‘occupying’ the access link of 32/3,600 = 2/225 during the Busy Hour.

Note that if the access line rate is greater than 1 Mbps (which it almost certainly will be) then many file downloads will be a lot faster, which lowers the overall probability of contention, so it’s the worst case scenario we’re dealing with here.

So we now imagine 12 * 16 = 192 little ‘file daemons’ all wanting to do their file download (= ‘make a call’) during the Busy Hour, with probability 2/225 each. The expected number of simultaneous downloads = l = 192 * (2/225) = 1.7.

We now need to know the probabilities of k = 0, 1, 2, 3 ... simultaneous file downloads as shown in figure 3 below.

Figure 3. Poisson distribution for Data/Internet traffic, l = 1.7

If we add up the probabilities for k = 0 – 5, we get 99.2%. So we can achieve the required service level if we provision enough bandwidth for five simultaneous file downloads (at 1 Mbps each).

As I mentioned, this analysis assumes that ALL file downloads occur at 1 Mbps. In fact most of them would happen much nearer the (faster) basic line rate, so freeing up more time for other downloads in a virtuous circle: in other words, this is very much the worst case.

4. TRAFFIC DIMENSIONING

We are now in a position to dimension the access link so that both multimedia conferencing users and data users meet their expectations more than 99% of the time.

We decided that we need to budget for:

* 6 simultaneous multimedia sessions at 0.5 Mbps each = 3 Mbps.
* 5 simultaneous file downloads at 1 Mbps = 5 Mbps.

Total bandwidth required for the site access link is 3 + 5 = 8 Mbps.

This analysis is conservative but to allow for some headroom and growth, we might order a 10 Mbps access link.

5. NOTES

5.1 Because of the non-linearity of the Poisson distribution, there is not a direct connection between number of users and the required access link bandwidth. If we considered 24 users, the access bandwidth required would be less than 16 Mbps.

5.2 We have considered the streaming real-time and data non-real-time traffic requirements separately and simply added them together. This is conservative: there would be further stochastic gains in reality – but not sufficient to invalidate the analysis here.

5.3 Traffic is uploaded as well as downloaded. However the links are bidirectional and downloads are normally greater in volume than uploads.

5.4 In practice the analysis of this paper should be used to create a spreadsheet which automates all the calculations shown above.

5.5 Many file downloads can be expected to gain access to the full line access rate (10 Mbps in the example here). At this rate a 4 MB file will be received in just over three seconds. This is roughly equivalent to the service a UK residential broadband service could provide, close to the exchange.

The Iron Lady

Seen this afternoon at the Wells Film Centre. We thought we'd be the only ones there but it was jam-packed.

The story is centred around present-day Thatcher, living like any other elderly lady: mostly housebound, occasionally confused, prone to hallucinations of her husband Denis.

The flashbacks of the major Thatcher events (miners, Falklands, poll tax) are familiar to any middle-aged brit.

The film is good though, and reminds us that we're back to the same point in the cycle: too much public spending, too many entitlements, not enough get up and go. It's a message which has resonance.

Lost in Hilbert Space

In an SF story I was once writing I needed to get the hero out of his closed prison cell. In the old physics, he could simply have blown a hole in the wall with some explosives – but of course, the guards never let him have any.

In physics terms, the scientist is trapped by inter-molecular forces in the cell walls. An explosion simply dumps energy which disrupts these bonds – the fragments (and our hero) burst free.

But how to make things work with the new physics?

My first thought was new fields. So I started to look at the inflation field of the early universe , or some of the new stuff in supersymmetry. This is still something I continue to research but I’ve come to believe they don’t really help. The coupling between new fields and the potential barrier would still be via energy transfer so it’s just another explosion – I’ve no idea what a controlled local inflation field would do but it doesn’t seem very survivable.

Continue reading at sciencefiction.com.

This article is really an extended joke, the 'victim' being Michael Lockwood whose "Many Worlds Interpretation of Quantum Mechanics" doesn't seem to say too much which is new.

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Back in Reading, finishing up some documentation for the client at this moment. Alex is in process of geting a Plusnet phone service and WiFi broadband network installed here.

At this moment the phone works while the broadband should be up within a couple of days. I'm getting my Internet connectivity as I write this from my HTC smartphone which can be configured as a WiFi hotspot, backhauling via its 3G connection.

Not bad, but it doesn't beat copper.

The Daily Telegraph?!?

So how did I find myself with The Daily Telegraph on my phone? Here were my choices: Financial Times (6 pounds a week); The Times (2 pounds a week but an unusable registration process & a poor layout); The Guardian (I Am Not A Teacher); or The Telegraph (2 pounds a week and acquired painlessly via Amazon Kindle).

Perhaps I've suddenly become an old person :-)

Was it smart of The Telegraph to use the Kindle as its channel to market? They lose direct control of their smartphone customers - Amazon has the credit card numbers and customer data - but they surf Amazon's remarkable market penetration and ease-of-use. I reckon they're right.

Tube Life

Back on the tube, after a year. In the centre of the carriage there are four seats on either side. I was standing in the crush and counted three kindles out of the four people sat there.

Yesterday it was only 50%: a kindle and an iPad, which was showing the Daily Mail.

I was squashed next to a guy reading ... a book! I wanted to scream at him: what are you doing? Where is your kindle? (I managed to control myself).

I've had The Times app for the last couple of weeks but today it was uninstalled. Hey guys, your design is poor - articles turn up under too many categories; also I was even tempted to subscribe at two pounds a week till you asked me for a ton of irrelevant personal information and then your registration screen locked-up. Take a look at the London Evening Standard for how an app should be done.

I'm trying to work out whether I should be more concerned about the crisis in Iran (will it be war?) or the crisis in Hungary (authoritarianism, default?) or whether I get the client document written tomorrow. Events, dear boy, events!

Drowned in Reading

First meeting with the client today. I left the flat mid-morning for the ten minute walk to Reading station. As I stepped on to the Thames-side path the skies opened and I was engulfed by torrential rain slammed into my very body by extreme gusts of wind.

It's strange walking through the ricochets of fast-impact raindrops on the pavement; like walking through long grass. My socks were soon soaked; my shoes provided no protection. I haven't been so wet since arduous training with the army cadets in Snowdonia (the 1960s).

I had partially dried out by the time we met with the client ...

Friends and Lovers

You may have first learned your Myers-Briggs personality-type indicator (MBTI) through work. Perhaps you went for a job and they gave you a battery of psychometric tests; or maybe there was a team-building or personal development program and the instructor told you about the different personality types – usually they tell you it’s about how to get the best out of people.

Personality types are real and also say a lot about your friendships and relationships. Before we get deeper into this, you may need to discover your own personality type – take an assessment here.

Read more at sciencefiction.com.

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This is quite a complex article - it goes deeper into the Myers-Briggs/Jungian theory than is usual. But the payoff is an insightful view of how relationships work - so much more profound than untrained intuition would deliver.

I'm writing this from Reading: I have a client meeting tomorrow in London where I hope to discover more about the scope of the work and how long this particular contract is likely to last.