Pytest for Automated Network Testing (II)

Pytest for Automated Network Testing (II)

In part one, we covered the basics of pytest and wrote our first network tests. We tested BGP and OSPF on a single device, then extended it to multiple devices. We also looked at parametrization and how it helps treat each device and each neighbour as an independent test.

In this part, we will cover inventory management with Nornir and pytest fixtures.

Pytest for Automated Network Testing
Pytest gives you full control. You write the test, you decide exactly what to check, and you get a clear pass or fail result. You can test one device
Pytest for Automated Network Testing (II)PacketswitchSuresh Vinasiththamby
Pytest for Automated Network Testing (II)

Nornir Introduction

Nornir is a Python automation framework designed for network engineers. Instead of writing your own logic to connect to devices, manage inventory, and run tasks in parallel, Nornir handles all of that for you. We have a dedicated series on Nornir, which you can check out here, so we are not going to do a deep dive in this post.

The reason we are using Nornir here is for inventory and task management. Instead of hardcoding a list of IP addresses in our collection file, we define our devices in a hosts file with groups, credentials, and Continue reading

PP109: ThreatLocker Enforces Zero Trust With Strict Application Control (Sponsored)

ThreatLocker takes an opinionated approach to Zero Trust. The company, our sponsor for today’s episode, starts with application control. It uses endpoint software that runs on PCs and servers to allow or deny applications to run. It can also monitor and control the behavior of allowed applications. ThreatLocker has extended its platform to include network... Read more »

When “idle” isn’t idle: how a Linux kernel optimization became a QUIC bug

CUBIC, standardized in RFC 9438, is the default congestion controller in Linux, and as a result governs how most TCP and QUIC connections on the public Internet probe for available bandwidth, back off when they detect loss, and recover afterward. At Cloudflare, our open-source implementation of QUIC, quiche, uses CUBIC as its default congestion controller, meaning this code is in the critical path for a significant share of the traffic we serve.

In this post, we’ll tell the story of a bug in which CUBIC's congestion window (cwnd) gets permanently pinned at its minimum and never recovers from a congestion collapse event.

The story starts with a Linux kernel change aimed at bringing CUBIC into line with the app-limited exclusion described in RFC 9438 §4.2-12 — a fix to a real problem in TCP that, when ported to our QUIC implementation, surfaced unexpected behaviors in quiche. It has a happy ending: an elegant (near-)one-line fix that broke the cycle.

CUBIC's logic in a nutshell

Before we dive into the core problem, a quick refresher on Congestion Control Algorithms (CCAs) may help to set the stage.

The central knob a CCA turns is the congestion window (cwnd Continue reading

Worth Reading 051226


The screenshot feature has cultivated a wide range of impactful academic research across computing and social scientific fields.

 


When Motorola unveiled its Iridium global satellite-based mobile telephony service in the late 1990’s everything augured well for a revolution in the satellite communications market, only it didn’t happen.

 


While the software industry has made genuine strides over the past few decades to deliver products securely, the furious pace of AI adoption is putting that progress at risk.

 


The analytic company IDC says the U.S. economy will be generating 394 trillion zettabytes of data annually by 2028 (a zettabyte is a trillion gigabytes).

 


Enterprise strategists need to worry about securing their environments against AI-powered attacks.

Reorganized ipSpace.net Segment Routing Resources

I created nine sample SR-MPLS topologies for the ITNOG 10 SR-MPLS workshop, and of course, we ran out of time. I plan to cover those topologies and resulting printouts in a series of blog posts; to prepare for those, I cleaned up and reorganized the Segment Routing blog category, which is now split into two:

Hope you’ll find them useful! Also, if you know of other non-vendor Segment Routing resources, please leave a comment, email me, or submit a pull request.

Quantum safe amateur radio secure shell

I’ve previously pointed out that the AX.25 implementation in the kernel is pretty poor. It’s not really being maintained, and even when it gets fixes after I reported it, with people running LTS OSs it can take like 5 years before before the fix actually reaches users, if ever. So when writing applications, you still have to work around kernel bugs from a decade ago. This makes it kind of pointless to upstream patches.

The exception is security patches, and reading between the lines of why the AX.25 code is now being removed from the kernel, it sounds like maybe some LLM (like the looming “Mythos” and the related Glasswing) may have found some severe problems. But even if there aren’t any known security problems yet, having code is now more of a liability than ever. Code needs to be removed, or taken responsibility of. (tangent about ffmpeg at the bottom of this post)

With the kernel code removed, say goodbye to the old walkthrough.

The new API

Well, not “new”, per se, but “replacement”.

With the socket based API about to be gone, we need some other way for applications to send packets and Continue reading

Worth Reading 050926


These milestones highlight the significance RPKI has gained over the past decade. Starting off as an experimental technology, it has become a central component of the Internet, affecting a large percentage of its networks.

 


More than 9.7 million third-party businesses sell goods on Amazon, and Amazon makes a lot of money charging those third parties to sell on its platform—$117.7 billion in 2022, representing 23% of Amazon’s total revenues.

 


For much of the history of computing, it was reasonably safe to assume that a machine was doing what you told it to do (and what its creators promised it would do), because its operations were local.

 


There is always the case that the unexpected happens, and X.509 certificates are no exception. There are circumstances where the certificate should be marked as unusable immediately, which is before the notAfter expiration time.

 


Our investigation uncovers two sophisticated telecom surveillance campaigns and, for the first time, links real-world attack traffic to mobile operator signalling infrastructure.

SecureCRT to SuperPutty – Migrate Your Sessions with One Python Script

If you’ve ever had to move a large session library from SecureCRT to SuperPutty, you know the pain — there’s no built-in migration path, and manually re-entering dozens (or hundreds) of sessions is a miserable afternoon. I wrote SCRT_2_SPUTTY to handle it automatically. Point it at your SecureCRT XML export, and it spits out a ready-to-import SuperPutty XML file. No third-party libraries, no configuration files — just Python and a single command.

SecureCRT to SuperPutty – Migrate Your Sessions with One Python Script

If you’ve ever had to move a large session library from SecureCRT to SuperPutty, you know the pain — there’s no built-in migration path, and manually re-entering dozens (or hundreds) of sessions is a miserable afternoon. I wrote SCRT_2_SPUTTY to handle it automatically. Point it at your SecureCRT XML export, and it spits out a...

The post SecureCRT to SuperPutty – Migrate Your Sessions with One Python Script first appeared on Fryguy's Blog.

Hedge 304: Deep Dive into a Network Master’s Program

If you’ve ever been curious about what an advanced degree in network engineering looks like, you’ll want to join us for this episode of the Hedge. Levi Perigo from the University of Colorado at Boulder joins Tom and Russ to talk through what earning a Master’s in Networking involves and what kinds of things you would learn.
 

 
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