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Hi, I'm Iljitsch van Beijnum. I'm a freelance network architect, specializing in internet routing (BGP) and interconnection between networks (peering and more).

On this site I post both work related and somewhat less work related articles, for purely work-related information, see Some of the blog posts here are in Dutch, others are in English.

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.

Full article / permalink - posted 2019-03-18

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 - English version

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 - Nederlandse versie

Finally: native IPv6 at home!

It took a while, but I finally got native IPv6 at home from Ziggo, my cable ISP a few months ago. All it took was a new cable modem / home router, because they don't support IPv6 on the one I've had since I signed up with them six years ago. And lo and behold: I got myself some IPv6:

$ ifconfig en0
en0: flags=8863 mtu 1500
  ether xx:xx:xx:xx:xx:xx 
  inet6 fe80::8d:5a:e4d:176f%en0 prefixlen 64 secured scopeid 0x8 
  inet netmask 0xffffff00 broadcast
  inet6 2001:1c00:d00:7300:xxxx:xxxx:xxxx:xxxx prefixlen 64 autoconf secured 
  inet6 2001:1c00:d00:7300:75bf:1d31:ac76:d080 prefixlen 64 autoconf temporary 
  nd6 options=201
  media: autoselect
  status: active

Full article / permalink - posted 2018-11-11

NL-ix BGP security update event in Copenhagen

This Thursday I'll be at the NL-ix BGP security update event in Copenhagen, talking about BGP security topics, especially RPKI and BGPsec. I remember the first time I went to the IETF in 2002, where I heard about S-BGP and soBGP. And now last September that finally resulted in the publication of the BGPsec RFC (RFC 8205).

It's not too late to register, so I hope to see you there! Be sure to come say hi.

Permalink - posted 2018-04-15

Aantal kilometer gerold in 2017

In 2015 en 2016 was mijn doel om gemiddeld 10 km per dag op mijn inline skates te rijden. Dat is ook gelukt, beide jaren heb ik 3700 km afgelegd op acht wieltjes. In 2017 ging het een stuk minder goed, en kon ik net/bijna 100 km per maand halen:

Het begon redelijk in het voorjaar, maar in juni/juli had ik het druk met de voorbereidingen op mijn verhuizing. In augustus en september met reizen en dingen in het huis op orde krijgen en toen werd het weer snel slechter... De afgelopen week zijn meerdere malen lagers vastgeroest vanwege alle nattigheid.

Op naar 200 km per maand in 2018!

Permalink - posted 2017-12-31

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