9 posts tagged with "Programming"

I've always been more interested in the plumbing of the internet than the web pages sitting on top of it. Every time you load a page, your packets hop across a patchwork of independent networks called Autonomous Systems (ASes), each with its own ASN (Autonomous System Number). Who connects to whom, and how, is what I wanted to map. Now that it's so easy to vibe code with AI, any idea or interest can be turned into a project in minutes. So I built an interactive map of the internet's AS-level topology, and here's how it works and what it shows.

Yesterday I saw a post, now removed, on Reddit that revealed that ESET uses DNS queries to do MAC address OUI lookups. This is quite smart because it allows a client to avoid maintaining a local copy of the OUI database and also means that the databases can be queried without having to have direct or proxied http access to an external API endpoint.

I was having a conversation recently and Vercel came up. The organisation I am currently working with has been exploring it as it seems to offer a lot of benefits for developers who have been let down by the promises of cloud. I have to admit that I had not really looked at Vercel before, so I decided to take a look and while I was at it ended up building and deploying a simple web application that has been on the bottom of my to-do list for a while.

More than just an interview question​

I've sat on both sides of countless technical interviews over my years in networking. There's this familiar dance that happens when discussing OSPF: the candidate confidently states "OSPF uses Dijkstra's algorithm for route calculation," and I'll nod approvingly. But here's the thing - in hundreds of these exchanges, I've never once asked a candidate to explain what that actually means, and no one's ever asked me to explain it either.

Introduction: Beyond the Basics​

FizzBuzz has long been a staple of programming interviews. The problem is deceptively simple: print numbers from 1 to n, but replace multiples of 3 with "Fizz", multiples of 5 with "Buzz", and multiples of both with "FizzBuzz". It's not meant to be a challenging algorithmic puzzle; most candidates with basic programming knowledge should solve it without difficulty.

So why does this trivial problem persist in the interview landscape? Because I believe FizzBuzz's true value isn't in filtering out candidates who can't code—it's in opening discussions about complexity, language characteristics, optimisation, and the subtle costs of different operations. The best interviewers don't just ask candidates to solve FizzBuzz; they use it as a starting point for a deeper technical conversation.

A little while ago I set out to find a way to measure the overhead that FQDN filtering places on HTTPS web traffic. I've shared the results here, but I thought I'd take the opportunity to discuss the methodology in a bit more detail.

Introduction​

I've been asked to explain networks to people with no experience several times and it's hard to know where to start. There's so much history and so many computer science concepts that have led us to where we are today. I've always believed that to truly understand something, you need to be able to explain it to someone else. My goal here isn't just to explain the bits that make the internet work, but also to organise my own understanding and explore areas where I've taken things on faith instead of questioning why they exist. I'll start from nothing and rebuild the internet from scratch, solving the same problems that got us where we are today.

I've put together a summary of some common search algorithms and how they work. This post covers key search algorithms used in computer science, explaining their approaches, strengths, weaknesses, and showing Python implementation examples.

There used to be a great little website for route summarisation and it did it far more intelligently than Cisco kit does it. It looks like the site has dropped off the internet which is a shame but there is a handy python library called netaddr with has the same capabilities.

I have written a little wrapper for it which will regex the prefixes out of a ‘show ip bgp’ and then list the summary routes. You pass the output of ‘show ip bgp’ as a text file, it’s the only argument the script expects.