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Category Archives for "Russ White"

CoDel and Active Queue Management

Buffering packets in a network is both good and bad. It is good because a buffer can hold packets from one stream while another stream’s packets are being processed, to take up and release short bursts of traffic, to hold and then release packets when there is a very short interruption on the wire (or during a route change), and in many other situations. However, queues are bad when there is a standing queue, which means a particular flow always has some number of packets in a particular queue along the path between the source and the destination. This normally occurs at the narrowest point along the path, or rather the link with the lowest bandwidth. In a previous post, I looked at BBR, a change to the way TCP computes its window sizes, that attempts to reduce the amount of traffic “in flight” between a sender and receiver to reduce the number of packets being held in a particular buffer along the way.

This post will consider another solution: CoDel. CoDel is essentially an improved tail drop mechanism that provides the correct signals to TCP to slow down its send rate, or rather to reduce the window size (and Continue reading

Administravia 030417

Just a few notes on the blog site in general. I’ve rebuilt the sixty books pages without tables. I don’t know if this is better, but it does load a bit faster. I’ve also added links to my GoodReads and Feedly profiles just in case you’re interested in what I’m currently reading/read on a regular basis. I didn’t include all the RSS feeds I read in the shared Feedly profile, just general, culture, and technology.

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Why no YANG??

I was at Cisco Live in Berlin last week, and I came away with a question: why no YANG?

 

Here is a YANG model represented in YIN—this one describes an interface in Quagga, and is easy to read:

YANG can be expressed in many ways, such as YIN, or in a model format (which is still easy to read), or in json format. This is an example of HTML, taken from the Vimeo site:

The YIN representation of YANG is XML, and XML is also a superset of HTML.

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Into the Gray Zone: Considering Active Defense

Most engineers focus on purely technical mechanisms for defending against various kinds of cyber attacks, including “the old magic bullet,” the firewall. The game of cannons and walls is over, however, and the cannons have won; those who depend on walls are in for a shocking future. What is the proper response, then? What defenses are there The reality is that just like in physical warfare, the defenses will take some time to develop and articulate.

One very promising line of thinking is that of active defense. While the concept is often attributed to some recent action, active defense has been one form of warfare for many centuries; there are instances of what might be called active defense outlined in the Bible and in Greek histories. But it is only recently, in light of the many wars around Israel, that defense in depth has taken on its modern shape in active defense. What about active defense is so interesting from a network security perspective? It is primarily this: in active defense, the defender seeks to tire an attacker out by remaining mobile, misdirecting the attacker, and using every opportunity to learn about the attacker’s techniques, aims, and resources to reflect Continue reading

The Perfect and the Good

Perfect and good: one is just an extension of the other, right?

When I was 16 (a long, long, long time ago), I was destined to be a great graphis—a designer and/or illustrator of some note. Things didn’t turn out that way, of course, but the why is a tale for another day. At any rate, in art class that year, I took an old four foot spool end, stretched canvas across it, and painted a piece in acrylic. The painting was a beach sunset, the sun’s oblong shape offsetting the round of the overall painting, with deep reds and yellows in streaks above the beach, which was dark. I painted the image as if the viewer were standing just on the break at the top of the beach, so there was a bit of sea grass scattered around to offset the darkness of the beach.

And, along one side, a rose.

I really don’t know why I included the rose; I think I just wanted to paint one for some reason, and it seemed like a good idea to combine the ideas (the sunset on the beach and the rose). I entered this large painting in a local Continue reading