On Fri, Apr 09, 2004 at 06:22:06PM +0100, Jim Dixon wrote:
On Fri, 9 Apr 2004, Eugen Leitl wrote:
Internet is mostly a tree (if you look at the connectivity maps).
Not at all. A tree has a root; the Internet doesn't have one. Instead you have several thousand autonomous systems interconnecting at a large number of peering points.
A modestly high dimensional grid of some billion nodes doesn't look like this: http://members.easynews.com/L4/opte/www.opte.org/maps/static/1069646562.LGL.... D.700x700.png This is clearer: http://research.lumeta.com/ches/map/gallery/wired.gif It should look a lot like a Golgi stain of your neocortex, though, the horizontal component being dominating (until we've get several million birds zooming over our heads in the starry sky). The neocortex and the human CNS in general is also laid out in a specific way, because it's also been/is subject to massive optimisation, both evolutionary and in course of operation.
For a long time, most traffic between European countries was routed through Virginia. This has improved only in the last few years. In the same way a lot of Pacific traffic still runs through California. In each case what matters is not geography but politics and quixotic regulations.
You're proving my point. The network started as a bureacratic, static, tiny, suboptimal configuration. As it grew bigger, and started participating in economy it started minimizing itself. This isn't just connectivity, but goes down to the protocol level. We know IPv6 isn't the answer, mostly because it is largely geography agnostic, can't handle nodes moving with orbital speeds (or even a speeding car), doesn't handle interplanetary latencies and isn't local-knowledge routed/switched in general. It also can't handle relativistic speed cut-through, which is the killer requirement.
Within most countries the same sort of illogic applies. In the UK, for example, most IP traffic flows through London, and within London most IP traffic flows through the Docklands area, a geographically small region of East London. It's fractal: even within Docklands, almost all traffic flows through a handful of buildings, and there is a strong tendency for most of that inter-building traffic to pass through a very small number of ducts.
You're correct, currently. Things will become better as network ages, and especially if we get cellular radio architectures in densely populated areas (there's about a GBit/s worth of wireless bandwidth within a small cell, when we ignore THz and optical wavelengths).
Current flow is mostly dictated by frozen chance, politics (peering arrangements). Automating peering arrangments and using agoric load levelling in the infrastructure will tend to erode that over time. Over time, physical lines will tend to
be
densest along densest traffic flow.
Very true -- but this has nothing to do with geodesics.
Human societies optimize. Geodesic is a shortest path on Earth surface. Look at Christaller and followup (Christaller and geodesics is good first start).
? City layouts that I am familiar with are either haphazard or built around rings or some mixture of the two. MFS built a US national ring, a ring in New York City, a ring in London, and rings elsewhere in Europe. Other carriers tended to follow the same pattern.
I'm not going to dive into city architecture, but compare these two adjacent cities: http://www.redtailcanyon.com/items/18393.aspx
connected with traffic ducts (rail, highway) which is typically loosely geodesic (but for obstacles in the landscape). Fiber typically follows railway or highway.
That's certainly true, but now you are talking about political decisions made ages ago. Many roads in England were built by the Romans. These
A road is a place channeling traffic from A to B. Roman roads which are still used (I use one quite frequently) were created between areas of major human activity, requiring traffic frequent enough to warrant an expediture (in terms of wealth fraction, roman roads were just as expensive as autobahns).
roads lead to London. You see the same pattern on the Continent, of course, with the roads leading to the local capital (Paris, say) and then on to Rome. That is, fiber optic paths today reflect the strategic requirements of the Roman Empire, not geometry.
1) today, EU today, elsewhere, looks different. future, everywhere, looks even more different. We're at the beginning of the optimization process. You can't cheat physics in a relativistic universe, in an economic/evolutionary context. -- Eugen* Leitl <a href="http://leitl.org">leitl</a> ______________________________________________________________ ICBM: 48.07078, 11.61144 http://www.leitl.org 8B29F6BE: 099D 78BA 2FD3 B014 B08A 7779 75B0 2443 8B29 F6BE http://moleculardevices.org http://nanomachines.net [demime 1.01d removed an attachment of type application/pgp-signature]