how to calculate packet loss from a binary TCPDUMP file

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You can measure packet retransmits from the client to the server by counting the number of duplicate sequence numbers.

Packet retransmits from the server to the client can be measured by counting duplicate Ack numbers.

Note that a retransmit is triggered by more than just total loss (= timeout); if the remote machine rejects the packet, or the packet is corrupted, the local machine must also retransmit.

via networking – how to calculate packet loss from a binary TCPDUMP file – Server Fault.

I needed a way to measure this on a wifi network where packet loss can be very high and bursty.  This answer seems relatively simple to implement — just store off  ACK sequence numbers into an array of limited size and count how many times every new ACK matches in that array.  By monitoring this count I can determine where and when certain areas are getting bad and perhaps alert or alarm based upon a certain threshold.

Kepler’s Three Laws

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Kepler’s three laws of planetary motion can be described as follows:

  • The path of the planets about the sun is elliptical in shape, with the center of the sun being located at one focus. (The Law of Ellipses)
  • An imaginary line drawn from the center of the sun to the center of the planet will sweep out equal areas in equal intervals of time. (The Law of Equal Areas)
  • The ratio of the squares of the periods of any two planets is equal to the ratio of the cubes of their average distances from the sun. (The Law of Harmonies)

via Kepler’s Three Laws.

Pluto-bound spacecraft ends hibernation to start mission

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New Horizons is now so far away that radio signals traveling at the speed of light take four hours and 25 minutes to reach Earth.

The scientific observation of Pluto, its entourage of moons and other bodies in the solar system’s frozen backyard begins Jan. 15, program managers said. The closest approach is expected on July 14.

via Pluto-bound spacecraft ends hibernation to start mission | Reuters.

The Cost of the “S” in HTTPS

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 HTTPS may introduce overhead in terms of infrastructure costs, communication latency, data usage, and energy consumption. Moreover, given the opaqueness of the encrypted communication, any in-network value added services requiring visibility into application layer content, such as caches and virus scanners, become inef fective.

Via The Cost of the “S” in HTTPS

The Mathematical Trick That Helped Smash The Record For The Largest Number Ever Factorised By A…

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And in any case, because this trick works using only 4 qubits, it can easily be reproduced on any classical computer. So it’s not so useful after all.

via The Mathematical Trick That Helped Smash The Record For The Largest Number Ever Factorised By A… — The Physics arXiv Blog — Medium.

Here’s a paper on this subject:

[1411.6758] Quantum factorization of 56153 with only 4 qubits.

CoreOS is building a container runtime, Rocket

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What is Rocket?

Rocket is an alternative to the Docker runtime, designed for server environments with the most rigorous security and production requirements. Rocket is oriented around the App Container specification, a new set of simple and open specifications for a portable container format.

via CoreOS is building a container runtime, Rocket.

Nasty Lockup Issue Still Being Investigated For Linux 3.18

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It might be related to the kernel’s watchdog code due to research by Linus Torvalds. “So I’m looking at the watchdog code, and it seems racy [with regard to] parking and startup…Quite frankly, I’m just grasping for straws here, but a lot of the watchdog traces really have seemed spurious…”

via [Phoronix] Nasty Lockup Issue Still Being Investigated For Linux 3.18.

Turning Customers Into Cultists

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A number of Bay Area companies have come to incorporate this insight into their marketing strategies. In 2004, shortly after launching the restaurant-review site Yelp, the founders were struggling to grow the company. They decided to convene a gathering of about 100 power-users. The get-together “was a big success,” Ligaya Tichy, who later served as Yelp’s senior community manager, told me. “Bringing users together to share what they loved about the site led to a huge spike in activity. What we realized is that people aren’t really motivated by companies. They’re motivated by other people. We needed to get the message across: you are what makes this product cool.” The number of reviewers on the site grew from 12,000 in 2005 to 100,000 in 2006.

via Turning Customers Into Cultists – The Atlantic.

Slack now letting employers tap workers’ private chats

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The data collection does not happen automatically. There is a several-step process for team owners to request access, which includes sending a signed letter on company letterhead to Slack stating that the company’s policies allow that kind of access. Each request is reviewed by Slack for approval, the company says.

Once granted, workers on the team are notified of the data access, which includes all messages from that point forward. The feature is not retroactive.

via Slack now letting employers tap workers’ private chats | ITworld.

From: Slack: Be less busy.

Slack is a platform for team communication: everything in one place, instantly searchable, available wherever you go.

Weather.com Moves to Drupal

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When the new Weather.com launches it will be the highest trafficked Drupal site in existence with over 1 billion page views per month.

via Mediacurrent | Weather.com Moves to Drupal.

On the technical side, our approach was to increase cache efficiency by utilizing Javascript and Edge Side Includes (ESI) for client side rendering as well as optimizing calls made to their content delivery network (CDN), Akamai.