Wednesday, December 31, 2008
The requirements for Internet connectivity management are broadly speaking as follows.
• CPE authentication and authorisation.
• Allocation of system parameters (DNS, local gateway addresses; STB/SIP configuration).
• IP address allocation and lease management.
• Session management (VC set-up, integrity, tear-down; QoS and service management).
• Recording of time-connected and bytes-transmitted for billing.
Point-to-Point Protocol over Ethernet (PPPoE)
Coming from an established protocol family, PPPoE makes certain things easy.
• Username/password authentication using PAP/CHAP/EAP.
• Allocation of IP address, e.g. from RADIUS.
• The establishment of a virtual circuit with session-id, providing fine-grained link management.
• Easy to apply lawful intercept.
The disadvantages are:
• Maintenance of substantial per-session state at the BRAS/Broadband Network Gateway (BNG).
• Difficulties of rapid failover (given this state).
• Needs additional and more sophisticated protocols for service management and configuration.
DHCP is more lightweight and is a more natural fit to Ethernet access networks. It also provides more sophisticated mechanisms for IP address assignment and device configuration.
Circuit authentication can be implemented via DHCP option 82 where the CPE attached-circuit identifier (at the DSLAM or Ethernet Aggregation Switch - EAS) is sent to the DHCP server. This is better than trusting the MAC. An alternative is to use the combination of CPE VLAN tag + EAS stacked VLAN tag if these also uniquely identify the CPE.
An issue with DHCP is the lack of a convenient session ‘keep-alive’ mechanism. PPP has echo-request/echo-reply protocol units exchanged when data is not being sent. This can swiftly indicate if a circuit has failed, or if the user has disconnected – important information both for service management and billing.
Although not part of the PPP protocol, a BRAS/BNG will typically report to the RADIUS server both time-connected and bytes-transferred at session disconnect. This cannot be achieved purely by DHCP (the IP address lease mechanism is far too coarse-grained). Alternative mechanisms such as the persistent web-page/captive-portal concept of public WiFi networks have to be employed, at least until a suitable mechanism for DHCP is standardised.
PPP excels at session authentication and management, at the expense of costly and cumbersome state management in the BRAS/BNG.
DHCP is considerably lighter-weight and more powerful from a service configuration and management point of view, but requires the integration of additional protocols for authentication and fine-grained session management.
Tuesday, December 30, 2008
The beach at Tenby after Sunday Mass
The headland east of Manorbier
Mysterious words on the sand (click on picture to enlarge)
Clare at the castle at Carew
Nigel at Carew - dressed up like an astronaut.
View Larger Map
Thursday, December 25, 2008
It began yesterday with a certain mental lethargy as I was reviewing the pros and cons of PPPoE vs. DHCP (alternative methods of providing Internet access - if this means nothing to you, ignore it, but be warned that there'll be a write-up here sometime next week).
As the afternoon progressed a sore throat kicked in and my self-diagnosis became definitive. I went public and thereby permitted myself the general hang-dog persona of the somewhat-ill. A certain degree of sympathy was consequently elicited.
I am a keen self-observer of the cold, noting that the sore throat phase is the most unpleasant, but the running nose phase more protracted and irritating.
Today I was hoping for the in-between transition where symptoms subside, and one merely feels slightly euphoric and odd, but no, the sore throat has persisted.
And so we are under the regime of Lemsip, but unlike Andrew Motion in the Wikipedia reference, I haven't noticed any acceleration of creativity...
Wednesday, December 24, 2008
For the last couple of weeks it's been confined to the house as we struggled to figure out how to install a catflap. Rejecting expensive solutions through the double-glazing on the back door or tunnels through the kitchen brickwork, we eventually settled on a DIY catflap through the front door (pictured). Never mind that this is generally considered to have lowered the tone of the entire little group of houses to which we are privileged to belong.
The new catflap in the front door
Notice how much light it adds to the hall.
Shadow himself currently reacts with paranoid fear to any attempt to coax him to the scary outside. Opinions differ amongst we humans in the house as to how much persuasion and how much coercion to apply.
Shadow restingA persuasive approach is to put the litter just outside the back door (pictured below) and then close the kitchen door. He is then meant to do what he has to do, and find his way back into the front of the house through the catflap.
Litter trainingOn our first trial of this strategy, it took him two hours to figure out how to do this, and the litter remained undisturbed. In fact the real objective is to 'wean' him off litter altogether, relocating him to the new sand area which Clare dug for him at lunchtime today (pictured below) at the back of the garden.
The target objectiveAt present rate of progress this is surely a project for 2009.
I should say that when Shadow is not being 'persuaded' to use the new catflap, or to encounter the outside world, he remains a contented and happy creature, albeit one addicted - day and night - to duvets.
Tuesday, December 23, 2008
The Spire of Salisbury Cathedral from the CloistersWe passed the stall selling mulled wine (£2.75) and mince pies (50p each) and waited for almost an hour in the queue (pictured below) whch stretched all around the cloisters.
The queue waiting to get inInside there were seats aplenty, and eventually the Cathedral was full.
The audience faces the altar just before the service beginsThe singing was as beautiful as always.
Monday, December 22, 2008
VLANs - virtual LANs - were originally a method of partitioning enterprise LANs into distinct forwarding segments. A VLAN switch forwards on both the normal Ethernet destination address (DA) and the VLAN tag. A switch associates a VLAN with a specific port so that a VLAN-tagged frame can only be forwarded along a port which has enabled that tag. There is space for 4,094 different usable tags in the 12 tag-bits available (see diagram).
VLANs have local significance within a routed domain, so that if a network is partitioned into a number of layer-2 segments each connecting to its own port on a PE router (which interconnects them all at layer-3) then each of the segments can reuse the 4,094-sized tag space.
VLAN (Q-in-Q) Ethernet headerIn an equal access metro network, there is a requirement to separate traffic on a per-service (VoIP, Internet, IPTV), per-user (= the final switch port facing the customer premises) or in the most fine-grained mode, a separate VLAN per-service per-user. In this case we have almost recreated a point-to-point virtual circuit.
The reason for VLAN segregation is predominantly stability and security. Broadcast traffic, e.g. ARP messages, are constrained within a VLAN thereby avoiding uncontrollable broadcast 'storms'. A positive security advantage is that broadcast traffic from one carrier's customers are not accessible by customers of rival carriers. Also, the possibilities of malicious attack are reduced.
If customers are already using VLAN tags themselves in their own enterprise networks, then carrier VLAN separation may be implemented by a second, overlaid tag. This is called "Q-in-Q" after the 802.1Q standard defining VLANs.
VLAN Q-in-Q can also be used in the metro network as a way of managing a proliferation of user-specific VLAN tags - a form of tag aggregation similar to the VC-VP usage in ATM. However, since all forwarding is done on the combination of destination address (DA) and outermost VLAN tag, scalability resulting from Q-in-Q is limited.
Getting Ethernet to the levels of manageability and scalability expected of a carrier transport layer remains a work in progress.
Saturday, December 20, 2008
The pseudowire construct - more properly Pseudo Wire Emulation Edge-to-Edge (PWE3) - is an architecture more than a protocol suite. The implementation of PWE3 doesn't, for example, necessarily need MPLS, although that's the usual implementation.
RFC3985 tells us that "The required functions of PWs include encapsulating service-specific bit streams, cells, or PDUs arriving at an ingress port and carrying them across an IP path or MPLS tunnel. In some cases it is necessary to perform other operations such as managing their timing and order, to emulate the behavior and characteristics of the service to the required degree of faithfulness."
The pseudowire definition includes higher-layer service adaptation and convergence functions which are service specific. When MPLS is the underlying packet transport network, a four byte control word may be used to carry this information (see diagram below - 'Flags, Frag, etc').
The pseudowire protocol also includes a 'pseudowire demultiplexer' (also below - 'PW Label') which specifically identifies the individual PW. A number of different PWs may be carried over the same label-switched path (LSP), which then operates as a kind of pseudowire 'trunk'.
PWE3 over MPLSIn most state-of-the-art networks, PWE3 will be carried between MPLS edge devices and will be carrying Ethernet traffic (or possibly TDM).
Pseudowires can be set up manually (through OAM&P), or via signalling using LDP or BGP.
Friday, December 19, 2008
Keanu has the extreme Green position that humans are causing a global biocide, and for the sake of galactically-precious-biosphere-preservation, must be removed from the scene forthwith .
The idiotic American military do their militaristic best to buttress this possibly-shaky premise, but the heroic female scientist and her adopted trans-racial child convince Keanu - sorry, Klaatu but where's the difference? - that there is hope yet for human redemption.
Redemption appears in the end to be the complete and utter destruction of technology, which would reduce the Earth's carrying capacity for humankind to maybe a few million at most. Let the die-off commence!
The CGI special effects were beautifully wonky.
We loved it!
Note: No angular momentum was unconserved in this film.
Note: No cliche was left unturned in this film. For example, it is well known that 'biologist Lewis Thomas was asked what message he thought should be sent to outer space aliens. He answered, "the complete works of J.S. Bach". And then he added as an afterthought, "But that would be boasting"' (here).
Inevitably then, as Keanu is in the home of the distinguished research scientist who is trying to impress him that we're worth saving, what is playing loudly in the background but the Goldberg Variations. The female scientist says helpfully "It's Bach".
Wednesday, December 17, 2008
Yesterday in the pre-dawn I was on the 6.15 a.m. train out of Reading to Manchester for a client meeting. The locomotive ambled its way via Oxford, Birmingam, Crewe and Stoke for a very leisurely arrival at Manchester Piccadilly at twenty to ten.
It took a similar three and a half hours at the end of a day's client engagement, and I had then to drive back to Andover through the fog, finally arriving home just before ten p.m.
With its flat topography and dense population, England ought to be a natural for high-speed trains. But as soon as both ends of the route aren't London, you've had it.
Next time I'm flying.
Sunday, December 14, 2008
However, the Iran case is quite asymmetric and the payoff matrix looks something like the above.
If the US does nothing, then Iran gets the bomb and scores +5, while the US has to deal with the negative foreign policy implications and scores -x (how big is x?).
The US therefore prefers Iran not to get the bomb, which motivates a first strike. If the US gets away with it, Iran scores -5 and the US scores +1 as its foreign policy problem has now gone away.
If however Iran retaliates: massive destabilisation in Iraq; attacks on Israel via Hezbollah in Lebanon; or more generically via a wider Islamic/world reaction against the US; then Iran would get battered again and scores -10 but the US has a negative outcome of -y.
Given a credible posture that Iran would retaliate, the US has to figure out whether -y is worse than -x, and Iran has to persuade the US that it would not take an attack lying down. The latter case is a lot easier to make than second-strike retaliation in the MAD case, although Iran would no doubt come off even worse if it retaliated.
For the US there are no stable good outcomes, and it's still a case of a "subgame perfect Nash equilibrium".
Arguably, there is the missing option where 'the West' persuades Iran not to acquire nuclear weapons, and 'play nice'. But that's a different game.
Saturday, December 13, 2008
Here's the payoff matrix. Both sides can do one of three things: strike first, retaliate with an equally-destructive second strike, or sit on their hands. The fourth option, make friends and play nice, is a different game altogether.
Not all alternatives make sense. For example, both sides can't retaliate, and it's unlikely that both sides could exactly synchronise a first strike. Those cells are left blank.
Note that the payoff matrix format best suits a game where both players make their move at the same time. However, nuclear war is typically a sequential game which, as we shall see, has consequences.
Note that the scores indicate that if both parties strike, the result is armageddon, with payoff minus infinity for both parties.
If you strike and your opponent does not, they are obliterated and you have won. As you handle the fallout, you can reassure yourself that at least your enemy no longer exists: minus infinity to them and a modest +1 to you.
If you both do nothing, then you each get a score of zero, reflecting your continuing insecurity.
The first point to note is that the "do nothing strategy", while pareto-optimal (i.e. welfare maximising by most people's reckoning), is not a Nash equilibrium. Each side can improve its payoff by striking first, on the assumption that the other side will not retaliate because it doesn't increase its payoff (-∞) by so doing. In either case it's annihilated.
The scoring method is explained here (Nash equilibria in a payoff matrix).
However, recall that this is a sequential game, so the appropriate model is a "subgame perfect Nash equilibrium". To compute this we have to eliminate 'non-credible moves'. To prevent the first strike option being the Nash equilibrium it's necessary to make not-retaliating non-credible.
Hence the onus on all politicians with fingers on the button to solemnly state that in the event of a nuclear attack there is not the faintest chance that they would do anything else but retaliate at once. There: (-∞, -∞) guaranteed (!).
Looks like sticking with the insecurity is the best bet after all.
Next: MAD and Iran
Thursday, December 11, 2008
'Prince Harry failed his four week selection course to be an army air corps helicopter pilot. As a result, despite previous announcements, Harry will not now be relocating to Middle Wallop to learn how to fly a variety of helicopters.'
As they fly over our house, I propose to be extra careful this coming month.
Wednesday, December 10, 2008
"Yes, I read that article yesterday. Having read Mandelbrot last year and having just finished the much commented on Taleb's Black Swan book it seems increasingly the case that the Financial Industry has gotten their mathematical model basics wrong.
Specifically the use of the "normal = gaussian distribution" where it is not (always) appropriate. Both Mandelbrot and Taleb see themselves as ignored outsiders in that industry promoting a new mathematical approach to unthinking insider "experts". Mandelbrot is more the "Darwin" whereas Taleb is more the "Huxley" taking on everyone he can find (hence getting interviewed a lot now). Quite a familiar story, in a sense.
Also biilionaire trader Soros describes this as the end of not just the recent housing bubble but of an economic-theory driven "super-bubble" that began in 1980. Surely these things have some sort of link to events that have happened in the wider industry, but what is the link I wonder?"
"I saw Taleb on Newsnight and he appeared to be a bumptious self-promoter with barely an original idea in his head. He went into my 'dud' file straightaway.
"There seem to be lots of physicists at the moment busily trying to 'straighten out' the economists (e.g. here but it's all over). Peston has argued that the purely local nature of specific bank and financial institutional models means they are blind to systemic correlations across the entire industry. They therefore assume independence wrt unlikely events, which is not of course the case when a global disaster strikes. Where, for example, was the primal, unsustainable level of global debt factored into these models?
"My own belief, for what little it's worth, is that the financial sector is a human activity in pursuit of local optimisations (profits), driven through a series of feedback loops with delay, and that this non-linearity always leads to overshoots. So I automatically filter out all the stupidity which says that we'll set things up in future so that such crises will never occur again. "
Twin cats with my mother and sisterMy father now has two sets of batteries to deal with - it doesn't appear to have put him off. The two cybercats seem to recursively drive each other's behaviour. Very cute, if a little tough on the power.
Fred Seel: chief cat mechanic (and nice jumper)To my utter and complete amazement, I managed to get a Bluetooth link working between my father's Nokia camera-phone and his computer, so he can transfer photos.
Tuesday, December 09, 2008
Just a reminder to self how I belatedly realised that a much better solution is to run MPLS pseudowires edge-to-edge from the CLE (customer located equipment). Of course, this means that the CLE must be MPLS-capable.
Important to ensure that the CoS indicators in the payload headers are replicated in the MPLS Exp bits and the Ethernet 802.1p indicators across the switched Ethernet network.
Also need to worry about how end-to-end protection is to be ensured (e.g. is RSTP good enough in the Ethernet part of the network? What are the alternatives?).
A good summary, although a few years old, here.
We also saw for the first time in our lives, a white barn owl. It launched itself about twenty feet above our heads from its tree-home and did a couple of circuits: long enough for us to get a very clear view. It was as white as milk with wings perhaps two feet from tip to tip. We hung around, waiting for a re-appearance and photo-op, but that was that.
Our adopted cat, Shadow, is settling in and squeeking piteously less. Today Clare has been on the phone to various tradespeople as regards installing a catflap. The quote to locate it in the back door (double-glazed top and bottom panes) came to more than £280 so we're examining alternatives.
The catflap itself, from Homebase, came in at less than a tenner.
Monday, December 08, 2008
Clare painting longshipHere's the picture itself in its current, early state, taken just before we left for Hastings..
The paintingWe went down at Hastings yesterday to collect Clare's niece's cat, Shadow. The one which keeps running back to their previous house. Try that from Andover!
ShadowShadow spent the evening whining piteously and was locked in the kitchen overnight with Iams and litter.
This morning, it had pulled the bin over in search of old chicken bones, and was still whining piteously. It is currently hiding under the bed.
They say the first three days are the worst.
Friday, December 05, 2008
Clare in Harewood ForestIt was extremely quiet, so far from the roads, and recent rain had made the ground soggy underfoot.
The author showing his new hatAfter a while the path changed from fallen-leaves-over-mud to pine needles, strewn in a red carpet over a surfaced track.
A conifer carpetNow, to the left, the ground opened out and rose up to a ridge, where winter trees stood distanced and exposed.
Winter treesFinally we came down to the Longparish Road via the old Roman Road. As we approached Wherwell again, the river Test appeared close by, flowing full and languorous, at the Winchester Road bridge, where previously tolls were collected.
The river Test at WherwellEven at noon, when we started our walk, the winter sun was astonishingly low in the sky, but out of the wind, there was warmth in it.
Just a piece of breaking news: we are to go down to Clare's niece this weekend to formally adopt their runaway cat, which we shall bring back to live with us in the Pentons. More later.
Thursday, December 04, 2008
The stealthy crossbow also pleased him. He would lie against the trunk of an ancient elm for hours in complete repose, musing on issues philosophic and historic, until a baby boar happened by. Whoosh! Thwack! The bolt would fly home. An infant life, wild and free, transformed into dinner.
Prince Michael had a much younger sister, Gabriella who – all agreed – was perfection herself. Quiet, modest in appearance and demeanour, she devoted herself to the feminine arts: painting, playing the harpsichord, singing the local atonal folk songs, tapestry work, and helping the poor.
The prince loved her absently until the time came to leave his strenuous but comfortable life, to wander and adventure through the wider, unsuspecting world.
He made a start by righting smaller wrongs, killing trolls and maiming goblin hordes. He then progressed to bigger things: the slaying of dragons, the saving of minor female royalty and the leading of morally well-founded protest movements. Finally, after many years and having acquired a modest fortune, he bought a castle somewhat adjacent to the one where Gabriella now lived with her royal consort and family, and re-opened their acquaintance.
Initially he and his sister were strangers to one another, and were guarded in their conversation. Michael would wax enthusiastic about his latest choice of weapons, while Gabriella would mutter asides to her family along the lines of “What was that all about?”
After a while they took to riding round the countryside together in Michael’s open wooden carriage, which he had bought new from a carriage-wright known for his reliability.
Sat next to Michael in the swaying seat, watching his expert hand wielding the reins, and feeling every lurch of the wooden wheels as they bounced at speed from rut to pothole to jut-out stone, Gabriella would make accommodating conversation.
“It is much to your credit that you have devoted yourself to the benefit of our local community.” Gabriella would say.
“Really? Do you think so?” Prince Michael would reply. “You know, I’m full of energy, and anything new really fascinates me. If there’s some novel engine to speedily dispatch an evil-doer, I have to be the first to understand its principles of operation and try it out ...”
‘Will he never stop?’ whispered Gabriella to herself.
“... and indeed I heard the other days of some new kind of bow which literally stuns its victim with a strange electromotive force. I placed an order at once and soon you will see me lurking in vales and droves, the electro-scourge of local ill-doers.”
Prince Michael drove the horses forward down his favourite lane, ducking with pleasure beneath the suddenly-emergent low-hanging boughs which formed such an interesting random canopy over this section of the track.
Dodging this way and that, in imminent fear of decapitation, Gabriella wondered again at the utter obtuseness of her elder brother. God save us, she thought, from those obsessional, self-centred, self-indulgent, mediocre-dressed-as-learned, puppyish, faux-self-deprecatory people, who by position or family connection have power over us.
Michael started a new story about a smoke box which, he claimed, would let the merest peasant have the equivalent of several horses at his disposal. In as short a time as maybe one hundred years?
An unsuspected branch suddenly whipped from nowhere, striking prince Michael a fearsome blow on his right temple, and dispatching him instantly.
After Gabriella had stopped the carriage, calmed the horses and seen to the proper disposal of the prince, she tried to think of a suitable epitaph for Michael.
“Absence makes the heart grow fonder”?
“Don’t just do something, stand there”?
They all sounded appropriate, but surely that last one was a board game?
Wednesday, December 03, 2008
Many years ago I left an underpaid research job to run a high-touch consulting group. My new boss, K., was an interesting guy. He had been a founder of the company, but had never surfed the growth of the organisation to its executive summits. The reason he remained a senior middle-manager was that he was ENFJ (think a male version of Germaine Greer).
K. was warm, emotional, paternal and the immediate recipient of the vexed issue of my under-remuneration. A few months later, he informed me that he had succeeded in getting me a substantial rise. What happened next changed our relationship for ever.
I nodded in appreciation and moved on to the next topic of our meeting. He looked surprised and nonplussed. “What’s the matter?” I said.
“You could at least show some gratitude.”
So here were my thoughts. I had been objectively underpaid for my new role. It was the job of my manager to fix this problem. Heavens, it was my day-job to fix problems and I didn’t expect personal gratitude for doing so. That was my job!
What I didn’t appreciate (typical INTP) was that in his psychological worldview he had gone out of his way to show appreciation of my abilities and to lobby for me in the organisation, and my lack of a warm, generous response wounded him deeply and forever. Instantaneously, I had moved from being a protégé to a viper in the nest.
I had a colleague, J., who with my later knowledge of the MBTI I would rate as ESTJ.
J. was somewhat vain and prickly, intelligent but not conceptual, and we were as alike as chalk and cheese. J. did, however, have the SJ traits of loyalty and hierarchy, and was able to give K. the kind of emotional support which I had so lamentably failed to provide.
After a while, I moved on and eventually J. got K.’s job when he retired.
A postscript: I was always rather fond of K., and even his rejection of me seemed curiously idiosyncratic and perverse, but not damning. On his final day there was a big farewell ‘do’ and people lined up to walk past him, shake his hand and wish him well.
I made the effort to turn up, and when I got to him, he was horribly embarrassed, turning away as if I was some spawn of hell itself. He could not bring himself to speak with me.
What a shame.
Having abandoned the more educated part of its demographic, this is the way the BBC now does ‘science’ for non-intellectuals (the ‘sensors’ of Jungian type theory).
- Pandering to the non-intellectual comfort zone of ‘curious facts’ rather than challenging the audience with novel paradigms.
- Contemptuous of its audience by serving up inconsistencies and plain errors with nary a concern (see below).
- Science-pornographic - leaving a nasty aftertaste of watching but not touching.
It is not true that everyone has their own time-flow which is different from anyone else’s: this is only true for observers in relative motion or at different curvature points within gravitational fields. Relativity is meaningless without clarity about this.
It is not true that a quantum granular theory of time restores the ‘common-sense truth’ of ‘flowing time’ with a frozen past and open future, and that's not what the somewhat-photogenic young female researcher from Imperial College actually said. Special Relativity, which no-one is rejecting, has already destroyed that idea for good with the death of universal simultaneity. (But see here).
And can we finally lose for ever all those tiresome and lying graphics of the big bang as a vast CGI explosion within space and time, when it was a mode of expansion of space-time itself?
Any moderately intelligent viewer who eschewed ‘Survivors’ to watch this will have come away with a number of mutually inconsistent factoids in their head and will have reached the conclusion that modern science is incomprehensible.
Maybe it is, but not for the reasons presented in this programme.
Meanwhile, there is an essay competition currently running on the nature of time which may interest people disappointed with Horizon. The full list of essays is here, with some recommendations from Arcadian Functor here.
A particularly interesting essay, by Sean Carroll, can be found here.
Tuesday, December 02, 2008
The Y-chromosome type of this lineage is technically R1b, called 'Oisin' by Bryan Syke's company Oxford Ancestors, and 'Ruisko' by Stephen Oppenheimer's company Ethnoancestry (all of which will sell you a DNA test!).
However, as water levels rose in the Mesolithic, some of the R1b descendant population moved up the channel and then the Seine or the Rhine to colonise Northern France, Germany and Denmark. Previously, other R1b descendants had progressed round the north of Scotland to Norway and spread into Scandinavia.
There the basal R1b-type Y-chromosome accumulated further mutations, and its bearers became Vikings, Jutes, Angles and Saxons - and Celts. Some of them diffused back into England from the east, as discussed in the previous post.
It follows that possession of the R1b male Y-chromosome type cannot indicate whether one's more immediate ancestors were Britain's former 'Celtic-speaking' inhabitants, or whether they were part of the Saxon, Anglic, Jutish or Norse population who carried the R1b gene cluster. To achieve a further level of discrimination one must look at the details of the Y-chromosome.
In DNA analysis, certain marker points are located on the Y chromosome where a sequence of nucleotides (G, A, C, T) repeats. The number of such repetitions is the mutation variable. The sites are labelled with a code such as "DYS 19" where DYS stands for DNA Y-chromosome Segment (see the Wikipedia description here). So DYS 19 = 14 means 14 repetitions at this marker site.
By looking at the exact number of repetitions at each marker point, the more recent paternal ancestry can be narrowed down to a much more specific region, based on databases of samples from today's population, carefully chosen to have had ancestors living in the same small area for as long as possible. Up to a few hundred years ago populations were pretty geographically localised.
Much of this information is proprietary, and is used to drive the business models of DNA-testing companies, but there is some on the web, and you can google for matches. For example, try googling R1b DYS 390 23 and you will see sites suggesting that this R1b variant is Germanic! Another interesting site is here.
To help in the process, here is my Y-chromosome data (from Oxford Ancestors).
DYS 19 = 14 repetitions
DYS 388 = 11
DYS 390 = 23
DYS 391 = 11
DYS 392 = 13
DYS 393 = 13
DYS 389i = 10
DYS 389ii-i = 16
DYS 425 = 12
DYS 426 = 12
This is the Atlantic Modal Haplotype, described here.
In case this seems awfully male chauvinist, it should be pointed out that the Y-chromosome shows considerably greater variation than mitochondrial DNA, and this greater mutation rate is what allows recent variations of geography to be determined.
I have no plans to spend any more money on further refining my more recent paternal ancestry - it seems more likely to be German/Danish than 'Celtic'. Perhaps it will all end up being free on the web for future Google searches: you can already get a long way.
Previous: The Origins of the British
Monday, December 01, 2008
In the very beginning was the unique exodus out of Africa, around 85,000 years ago at the southern end of the Red Sea. Europe itself was populated by the Cro-Magnon people from around 50,000 years ago – exploiting a favourable climatic change which opened up a northerly route through the fertile crescent of Mesopotamia. However, the most recent ice-age reversed the colonisation process in northern Europe.
At the peak of the last ice age, the Last Glacial Maximum between 22,000 and 17,000 years ago, sea levels were 120 metres lower than today. The British Isles were merely the north west peninsula of Europe (no North Sea or Channel) and ice caps covered Britain down to Oxford. The rest of the British Isles and Northern France was a polar desert, uninhabitable, and our European ancestors had retreated to more temperate refuges: the Basque refuge around northern Spain and southern France; a Ukrainian refuge to the east; and a Balkans refuge near the Black Sea.
Britain was recolonised as the ice age came to an end, around 15,000 years ago. Who were these people? They came from the Basque refuge, were genetically similar to the Basque people today, and probably spoke a language similar to Basque - this was before Indo-European languages. They were hunter-gatherers who brought down big game on the grass steppes which had replaced the polar desert in Britain and Ireland (at this stage still all one peninsula).
Between 13,000 and 11,500 years ago it again got very, very cold (the Younger Dryas). However, a small population hung on in Britain and Ireland. The period after the Younger Dryas is called the Mesolithic, extending from around 10,000 to 6,500 years ago. During the Mesolithic, a further wave of recolonisation entered the British Isles from Northern Spain, again following the ‘beachcombing’ coastal route up the Atlantic coast of France and past Brittany. The present day populations of Wales and Ireland are 80-90% genetically identical to this original founding population.
These founders did not, of course, stop at Britain/Ireland. They continued to Scandinavia and beyond, and penetrated inland along the river systems into France, Germany and Denmark. There, they met different gene flows coming West from the other two refuges in Ukraine and the Baltic. These more mixed groups would become the Saxons, Angles, Jutes, Vikings and so on.
Around 6,500 years ago the Neolithic farming revolution finally arrived at Britain. Again, there were two routes: one along the Atlantic coast, the other via central and north-west Europe. At this stage the North Sea was still a plain, and there was much tribal mixing between adjacent populations in ‘England’ and the ‘near-Continent’.
The climate had meanwhile changed, creating vast forests in north-west Europe. These were not good for hunter-gatherers, who tended to live more at the coast. Neolithic farming could, however, cut down trees and plant crops, or husband domestic animals; so there was a kind of possible symbiotic ecology between the hunters and farmers.
With the farmers came Indo-European languages (Celtish, Germanic and Romance, etc). The Celts appear to have been a large tribal grouping of Gauls who occupied the region between northern Spain and the line of the Seine-Marne in Northern France. As they controlled the bulk of the Atlantic coast, they dominated trade links with Cornwall, Wales and Ireland to their north. This seems to be the original introduction mechanism of Celtic languages such as Cornish, Welsh and Gaelic, supplanting the previous languages in those countries.
However, there appears to have been very little incursion of Celtic population: Oppenheimer’s genetic analysis suggests less than 4% in Ireland, 10% in Wales and 8-11% in Southern England. Meanwhile, as we move to around 3,000 years ago, he suggests that there were stable and substantial Saxon communities in the English South-East – linked to the Belgae across the water, while Scandinavian Angles and Jutes (from today’s Denmark) occupied East Anglia and points farther north on England’s north-east side.
This, then, would have been the situation when the Romans arrived. Subsequent Dark-Ages ‘invasions’ of Saxons, Angles, Jutes, Vikings etc didn’t change the population genetics much – just a few percentage points. They tended to congregate where their kinsfolk had previously established themselves. As the Dark Ages moved to a close, the Anglo-Saxons finally seized political control in England from the Celtic-speaking groups (the Britons) and then defeated the ‘Danelaw’ Viking incursions.
So the main bottom line here is that it’s a mistake to think that the aboriginal inhabitants of these islands were ‘Celts’. Genetically most of the people here are from the original South-West Europe founding population, more than 8,000 years ago. And Celtic, a relatively recent new language, was never spoken across the whole of the Isles. Ancient English, a Germanic language, would have been spoken in the South East while a Scandinavian (‘proto-Norse’) language would have been spoken in the North-East. And there were no genocides – just a process of normal tribal warface and acculturation.
Interestingly, Oppenheimer mentions the well-known genetic divide (roughly following the line of Offa’s Dyke) between the Welsh and the English. Despite the similarity in Y-chromosome and maternal mitochondrial DNA lines between the peoples of the British Isles, we all have many more ancestors than these two extremal lines. Most English people will have a complex admixture of ‘Celtic’, Angle, Saxon and Scandinavian genes in their complete family tree. The Welsh and Irish have had far, far less exposure over the millennia to these ‘non-Celtic’ populations.
So I take back my conclusion in a previous post, that on both maternal and paternal sides, my genes say I’m Celt. They actually say that my paternal and maternal lines are aboriginal British (which is not pejorative).
I suspect that my maternal ancestor around 2-3,000 years ago did speak a Welsh-like Celtic language, based on where she probably was, in the English South-West - for the paternal ancestor, see the next post.
But before that they spoke a non-indo-European Basque-like language - which I have no plans to learn in solidarity!
However, I will have many, many other ancestors who contributed genes from the other English peoples, which is why I’m English and not –for example – genetically part of the Welsh or Irish clusters.
For more, in particular about the Scots and Picts, which I have entirely ignored, read Oppenheimer’s book.
Next Post: more about detailed Y-Chromosome testing
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