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Category Archives for "Networking"

Steady State Markov Process

A Markov chain or Markov process is a stochastic model describing a sequence of possible events in which the probability of each event depends only on the state attained in the previous event. It is named after the Russian mathematician Andrey Markov.

Markov chains help model many real-word processes, such as queues of customers arriving at the airport, queues of packets arriving at a Router, population dynamics. Please refer to this link for a quick intro to Markov chains.

Problem

Let’s use a simple example to illustrate the use of Markov Chains. Assume that you own a barber shop, and You notice that Customers don’t wait if there is no room in the waiting room and will take their business elsewhere. You want to invest to avoid this, and you have the following info in hand:

  • You have two barber chairs and two barbers.
  • You have a waiting room for four people.
  • You usually observe 10 Customers arriving per hour.
  • Each barber takes about 15mins to serve a single customer. So each barber can serve four customers per hour.

You have finite space in the shop, so add two more chairs in the waiting room or add another barber. Now Continue reading

Broken commit diff on Cisco IOS XR

TL;DR

Never trust show commit changes diff on Cisco IOS XR.

Cisco IOS XR is the operating system running for the Cisco ASR, NCS, and 8000 routers. Compared to Cisco IOS, it features a candidate configuration and a running configuration. In configuration mode, you can modify the first one and issue the commit command to apply it to the running configuration.1 This is a common concept for many NOS.

Before committing the candidate configuration to the running configuration, you may want to check the changes that have accumulated until now. That’s where the show commit changes diff command2 comes up. Its goal is to show the difference between the running configuration (show running-configuration) and the candidate configuration (show configuration merge). How hard can it be?

Let’s put an interface down on IOS XR 7.6.2 (released in August 2022):

RP/0/RP0/CPU0:router(config)#int Hu0/1/0/1 shut
RP/0/RP0/CPU0:router(config)#show commit changes diff
Wed Nov 23 11:08:30.275 CET
Building configuration...
!! IOS XR Configuration 7.6.2
+  interface HundredGigE0/1/0/1
+   shutdown
   !
end

The + sign before interface HundredGigE0/1/0/1 makes it look like you did create a new interface. Maybe there was a typo? No, the diff is just broken. If you Continue reading

Worth Reading: Egress Anycast in Cloudflare Network

Cloudflare has been using ingress anycast (advertising the same set of prefixes from all data centers) for ages. Now they did a giant leap forward and implemented another “this thing can never work” technology: egress anycast. Servers from multiple data centers use source addresses from the prefix that’s advertised by all data centers.

Not only that, in the long-established tradition they described their implementation in enough details that someone determined enough could go and implement it (as opposed to the typical look how awesome our secret sauce is approach from Google).

Heavy Networking 658: Using Batfish To Model And Test Your Network

Today on Heavy Networking, modeling your network with Batfish. Batfish is an open-source project that builds a model of your production network based on a snapshot of your network and device configurations. Engineers can then test and validate changes against this model before making those changes to the production network. Guest Rick Donato walks us through how Batfish works, use cases, and more.

The post Heavy Networking 658: Using Batfish To Model And Test Your Network appeared first on Packet Pushers.

Heavy Networking 658: Using Batfish To Model And Test Your Network

Today on Heavy Networking, modeling your network with Batfish. Batfish is an open-source project that builds a model of your production network based on a snapshot of your network and device configurations. Engineers can then test and validate changes against this model before making those changes to the production network. Guest Rick Donato walks us through how Batfish works, use cases, and more.

Weekend Reads 120222


Nearly every application has at least one vulnerability or misconfiguration that affects security and a quarter of application tests found a highly or critically severe vulnerability, a new study shows.


75% of lookalike domains are registered with unrelated third parties and target these companies.


China’s antitrust watchdog, the State Administration for Market Regulation (SAMR), has proposed a revision of the nation’s competition law that targets tech firms.


A new report claims that Meta’s tracking Pixel has been used to collect your financial information when using popular tax filing services to send in your return.


Did you know that a Magniber ransomware infection can cost you a ransom of as much as US$2,500?


New York State has banned a practice becoming more common in the crypto-mining industry – the rescuing and repurposing of mothballed fossil fuel plants to exclusively provide energy for mining digital currency.


DDoS attacks target certain networks, flooding them with unwanted traffic from many different sources and causing interruptions to online services for legitimate users.


John the Ripper (JtR) is a popular password-cracking tool. John supports many encryption technologies for Windows and Unix systems (Mac included).


While in the near future most devices in the car will Continue reading

Surviving a Mastodon stampede

By now you’ve probably heard about Mastodon, the open-source microblogging platform that’s been gaining popularity since Elon Musk took over Twitter.A major feature of the platform is it’s de-centralized, distributed architecture that provides resilience, but a downside is that it can cause congestion and increase latency for the unprepared.Here’s how Mastodon works. Its servers (instances) operate semi-independently of each other, and users register with servers geared toward communities that interest them. But users can follow and interact with others from across the Fediverse—users hosted on other Mastodon instances as well as other services utilizing the open-source ActivityPub protocol from the Worldwide Web Consortium.To read this article in full, please click here

Hedge 156: Functional Separation in Network Design with Kevin Myers

Modularization is a crucial part of network design because it supports interchangeability, reduces the size of failure domains, and controls security domains. One critical aspect of modularization is functional separation, which argues for separating services onto specific physical and logical resources. Kevin Myers joins Tom Ammon and Russ White on this episode of the Hedge to discuss the theory and importance of functional separation in network design.

download

Kubernetes Unpacked 014: Using GitOps And AKS To Build And Deploy Applications

In today's episode of Kubernetes Unpacked, Michael catches up with Steve Buchanan, Principal Program Manager at Microsoft, to talk about using GitOps and Azure Kubernetes Service (AKS) to automate the building and deployment of applications. Microsoft has been working incredibly hard on AKS, including integrating different tools and platforms to make the lives of DevOps and Platform Engineers easier.

The post Kubernetes Unpacked 014: Using GitOps And AKS To Build And Deploy Applications appeared first on Packet Pushers.

Kubernetes Unpacked 014: Using GitOps And AKS To Build And Deploy Applications

In today's episode of Kubernetes Unpacked, Michael catches up with Steve Buchanan, Principal Program Manager at Microsoft, to talk about using GitOps and Azure Kubernetes Service (AKS) to automate the building and deployment of applications. Microsoft has been working incredibly hard on AKS, including integrating different tools and platforms to make the lives of DevOps and Platform Engineers easier.

IPv6 flow analytics with Containerlab

CONTAINERlab is a Docker orchestration tool for creating virtual network topologies. The sflow-rt/containerlab project contains a number of topologies demonstrating industry standard streaming sFlow telemetry with realistic data center topologies. This article extends the examples in Real-time telemetry from a 5 stage Clos fabric and Real-time EVPN fabric visibility to demonstrate visibility into IPv6 traffic flows.

docker run --rm -it --privileged --network host --pid="host" \
  -v /var/run/docker.sock:/var/run/docker.sock -v /run/netns:/run/netns \
  -v $(pwd):$(pwd) -w $(pwd) \
  ghcr.io/srl-labs/clab bash

Run the above command to start Containerlab if you already have Docker installed. Otherwise, Installation provides detailed instructions for a variety of platforms.

curl -O https://raw.githubusercontent.com/sflow-rt/containerlab/master/clos5.yml

Download the topology file for the 5 stage Clos fabric shown above.

containerlab deploy -t clos5.yml

Finally, deploy the topology.

The screen capture shows a real-time view of traffic flowing across the network during an iperf3 test. Click on the sFlow-RT Apps menu and select the browse-flows application, or click here for a direct link to a chart with the settings shown above. 
docker exec -it clab-clos5-h1 iperf3 -c 2001:172:16:4::2

Each of the hosts in the network has an iperf3 server, so running the above command will test bandwidth between Continue reading

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