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This is the archive for all posts from 2019.

A new beginning

It's time for something new: after three years as a network architect at Logius, I'm going back into business for myself.

I'm going to focus on providing advice about connectivity to the internet to organizations for which an internet connection is a critical asset.

Watch this space for more information!

Permalink - posted 2019-02-28

Een nieuw begin

Het is tijd voor een nieuwe uitdaging: na drie jaar als netwerkarchitect bij Logius begin ik vanaf 1 maart weer voor mezelf.

Hierbij richt ik me op het adviseren over connectiviteit naar het internet aan organisaties waarvoor een internetverbinding een kritisch bedrijfsmiddel is.

Hou deze plek in de gaten voor meer informatie!

Permalink - posted 2019-02-28

How elastic is your network traffic?

How much bandwidth do I need? Always a hard question. It gets harder as you use more network links, and have to start considering what happens when one or more links fail, leaving you with reduced bandwidth.

The simple way to determine how much total bandwidth you need is to make a guess, and then adjust until the peaks in your bandwidth graphs stay below the 100% line. The more complex answer is that it depends on the bandwidth elasticity of the applications that generate your network traffic.

Applications are bandwidth elastic (sometimes known as "TCP friendly") when they adapt how much data they send to available bandwidth. They're inelastic when they keep sending the same amount of data even though the network can't handle that amount of data. Let's look at a few examples in more detail.

I'm assuming the bandwidth need throughout the day shown in this graph:

Between 21:00 and 22:00, normal bandwidth use reaches a peak of just over 80% of available capacity. But now we lose 25% of our bandwidth, so we have a higher bandwidth need than we can accommodate between 18:00 - 19:00 and 20:00 - 22:00, shown in red below:

Let's look at the behavior of applications with different bandwidth elasticity.

Read the article - posted 2019-03-18

Dark mode!

Last year Apple introduced dark mode in MacOS. This is really nice at night because your eyeballs aren't blasted with tons of white backgrounds in pretty much all windows. Unfortunately, most web pages still use a white background. Obviously you can redesign your website to conform to dark mode, but this looks rather stark on computers in light mode.

The solution would be to have your website render dark on a system in dark mode and light on a system in light mode. As of the new version of Safari included in MacOS 10.14.4 Mojave that was released just now, you can actually do that, as you can see here. Just switch your system between light and dark mode and you'll see this webpage switch over accordingly.

I like to use this terminal command to switch between light and dark mode:

sleep 2; osascript -e 'tell application "System Events" to tell appearance preferences to set dark mode to not dark mode'

(Change the last "not dark mode" to "true" or "false" to enable or disable dark mode. The line above toggles back and forth.)

On your website you need to set up conditional CSS with media queries. This is what I use:

<style type="text/css" media="screen, print">
  body { background-color: #f0f0f0; }
  A { color: #c00000; text-decoration: underline; }
  A:visited { color: #700000; text-decoration: underline; }
  H1 { font-family: futura, arial, sans-serif; font-size: 14pt; }
</style>
<style type="text/css" media="screen and (prefers-color-scheme: dark)">
  body { background-color: #202020; color: #d0d0d0; }
  A { color: #ff6734; }
  A:visited { color: #d82000; }
</style>

The first part between sets everything up for light mode, with a very light gray background.

Then the second style section (in bold) with (prefers-color-scheme: dark) overrides those earlier color settings. Note that all the font settings from the first style section are inherited by the second style section; no need to restate all of those.

That's it! Pretty cool, right?

Update: have a look here for more information, including how to use dark mode with javascript.

Permalink - posted 2019-03-26

Dubbele regenboog!

Image link - posted 2019-04-25

→ πŸ‡ͺπŸ‡Ί Ja, er valt echt iets te kiezen bij de verkiezingen voor het Europees Parlement

Morgen zijn de verkiezingen voor de Nederlandse afgevaardigden naar het Europees Parlement. Ik had half-en-half het plan om hier een stukje te schrijven over wat nu de relatie is tussen de Nederlandse partijen en de Europese fracties waar zij deel van uitmaken. Maar: Stuk Rood Vlees heeft dit veel beter gedaan dan ik kon!

Absolute aanrader om deze blogpost te lezen.

De echte uitslagen komen pas zondagavond om 23 u nadat de stembussen de alle overige landen ook gesloten zijn, maar naar verwachting zal er donderdagavond wel een exitpoll zijn en wat uitslagen van individuele stembureaus.

Ik ben ook erg benieuwd naar de Britse uitslagen en de consequenties die met name de Tories hieraan zullen verbinden voor de brexit.

Read the article - posted 2019-05-22

→ Happy Birthday BGP

Geoff Huston has written a post on the APNIC blog congratulating BGP with its 30th birthday. BGP version 1 was published as RFC 1105 in June of 1989. Five years later, the BGP version 4 was published as RFC 1654. And we're still using BGP-4 today, 25 years later! Lots of things, including IPv6 support, were added later in backward compatible ways.

As usual, Geoff's story is comprehensive with lots of interesting details. For instance:

❝From time to time we see proposals to use geo-based addressing schemes and gain aggregation efficiencies through routing these geo-summaries rather than fine-grained prefixes.❞

Sorry about that. πŸ˜€ I still think it could work, though.

Well worth a read.

Read the article - posted 2019-06-10

Let's fix those BGP route leaks

Last week, there was a large route leak that involved Swiss hosting company Safe Host and China Telecom. The route leak made internet traffic for European telecoms operators KPN, Swisscom and Bouygues Telecom, among others, flow through Safe Host and China Telecom against the wishes of the telecom operators involved. See this Ars Technica story for more details.

In this post, I'm going to explain how the interaction between the technical and business aspects of internet routing have made this issue so difficult to fix. At the end I'll briefly describe a proposal that I think can actually make that happen.

Read the article - posted 2019-06-13

Path validation with RPKI draft

Last week, I suggested it's time fix those BGP route leaks. I live by the words everybody complains about the weather, but nobody does anything about it, so as such I wrote an Internet-Draft with the protocol changes necessary:

draft-van-beijnum-sidrops-pathrpki-00

I think we can stop these route leaks with a relatively modest change to RPKI: by combining the ASes the origin trusts and the ASes the operator of an RPKI relying party server trusts, we have a list of all the ASes that may legitimately appear in the AS path as seen from this particular vantage point.

Read the article - posted 2019-06-20

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