Aug 212019
 

How not to build and manage a transcontinental data network

I am reading an article in The Register about a major Internet outage that occurred last December, when a handful of rogue packets managed to clog up a backbone network for more than a day and a half, blocking even VoIP 911 calls.

There are two rather frightening aspects of this fiasco. Both rather horrifying, as a matter of fact.

First, that in this day and age, in late 2018, a backbone service provider can still be brought to its knees by something as simple as a malformed packet. What on Earth are you doing, people? Have you heard of penetration testing? Fault tree analysis? Auditing your equipment and system software? Or have these essential steps been dropped just so that you can report some cost savings to your shareholders?

But it really is the second point that I find particularly upsetting. To quote, “the nodes along the fiber network were so flooded, they could not be reached by their administrators”.

Say what? Are you telling me that you had no alternate means to access your nodes? Like, you know, something as crude and simple as a dial-up port with a command-line based management interface? I mean, this is something even my little home office network used to have, and when I dropped it last year, reacting to rising landline costs and the fact that I no longer used that data/Fax phone line at all, I did so because I have dual network connections. To learn that a major backbone provider doesn’t have the kind of redundancy that I take for granted for my own little network is disconcerting, to say the least.

I suppose I should stop rambling now, though. Truth to tell, I am ignorant as to how CenturyLink’s actual network is configured, and I certainly never managed a fiber optic backbone network. I am simply reacting to the main points of The Register‘s article even though I cannot independently confirm its veracity. In my defense, The Register‘s articles tend to be well written and accurate. Even so, criticizing from a position of ignorance is never a smart thing to do.

Nonetheless, if The Register is correct, this really is not how a transcontinental data network should be configured and managed. This also seems to be the FCC’s conclusion.

 Posted by at 5:04 pm
Aug 202019
 

I have been reading dire predictions about the increasingly likely “no deal” Brexit that will take place this Halloween.

Today, I ran across two things that drove the point home for me more than anything else.

First (actually, this came second, but let me mention it first), this warning by GoDaddy to their UK-based customers who happen to hold a .EU Internet domain name:

And then there is this: An article from three years ago by a Fedja Buric (judging by the name, probably from the region) who offers a sobering comparison between the breakup of Yugoslavia and Brexit.

It may have been written back in 2016, but I think its dire warning is even more relevant today, now that a no-deal Brexit is rapidly becoming a near certainty.

 Posted by at 9:00 pm
Aug 112019
 

Dear American friends: please stop calling your President “the leader of the free world”.

I live in what you call the free world but Trump is no leader of mine. I have not elected him. He does not represent my values.

On the contrary, he seems hell-bent on destroying the values that I consider fundamental to the free world. He already managed to drag his own country down (though arguably, other politicians and long-term partisan trends played an equally important role) so that it no longer qualifies as a full democracy on The Economist’s democracy index. Why would the rest of the free world want him to lead us down the same path?

 Posted by at 12:41 pm
Aug 072019
 

Yesterday, we posted our latest paper on arXiv. Again, it is a paper about the solar gravitational lens.

This time around, our focus was on imaging an extended object, which of course can be trivially modeled as a multitude of point sources.

However, it is a multitude of point sources at a finite distance from the Sun.

This adds a twist. Previously, we modeled light from sources located at infinity: Incident light was in the form of plane waves.

But when the point source is at a finite distance, light from it comes in the form of spherical waves.

Now it is true that at a very large distance from the source, considering only a narrow beam of light, we can approximate those spherical waves as plane waves (paraxial approximation). But it still leaves us with the altered geometry.

But this is where a second observation becomes significant: As we can intuit, and as it is made evident through the use of the eikonal approximation, most of the time we can restrict our focus onto a single ray of light. A ray that, when deflected by the Sun, defines a plane. And the investigation can proceed in this plane.

The image above depicts two such planes, corresponding to the red and the green ray of light.

These rays do meet, however, at the axis of symmetry of the problem, which we call the optical axis. However, in the vicinity of this axis the symmetry of the problem is recovered, and the result no longer depends on the azimuthal angle that defines the plane in question.

To make a long story short, this allows us to reuse our previous results, by introducing the additional angle β, which determines, among other things, the additional distance (compared to parallel rays of light coming from infinity) that these light rays travel before meeting at the optical axis.

This is what our latest paper describes, in full detail.

 Posted by at 9:10 pm