Something Old, Something New…

19 April 2016 |

Some time back a reader sent this question in— Is there some list of design fundamentals which were “true” or at least “good rules of thumb” in the past (2 months to 20 years and beyond) which are still proclaimed as true and good, which we need to throw out, or at least question closely…

The Design Mindset (5)

11 April 2016 | Comments Off on The Design Mindset (5)

So far, in our investigation of the design mindset, we’ve— Observed, specifically asking what, applying questions about state, surface, and optimization in our examination of the network as it’s actually deployed. Oriented, asking why, really focusing in on the questions around what we’re optimizing, and how that drives state and surface in the design. Decided…

The Design Mindset (4)—Interaction Surfaces

8 April 2016 |

Before talking the final point in the network design mindset, ,act, I wanted to answer an excellent question from the comments from the last post in this series: what is surface? The concept of interaction surfaces is difficult to grasp primarily because it covers such a wide array of ideas. Let me try to clarify…

The Design Mindset (3)

28 March 2016 |

So you’ve spent time asking what, observing the network as a system, and considering what has actually been done in the past. And you’ve spent time asking why, trying to figure out the purpose (or lack of purpose) behind the configuration and design choices made in the past. You’ve followed the design mindset to this…

CAP Theorem and Routing

25 March 2016 |

In 2000, Eric Brewer was observing and discussing the various characteristics of database systems. Through this work, he observed that a database generally has three characteristics— Consistency, which means the database will produce the same result for any two readers who happen to read a value at the same moment in time. Availability, which means…

The Design Mindset (2)

21 March 2016 |

In a comment from last week’s post on the design mindset, which focuses on asking what through observation, Alan asked why I don’t focus on business drivers, or intent, first. This is a great question. Let me give you three answers before we actually move on to asking why? Why can yuor barin raed tihs?…

The Design Mindset (1)

14 March 2016 |

How does a network designer, well, actually design something? What process do you use as a designer to get from initial contact with a problem to building a new design to deploying a solution? What is the design mindset? I’ve been asking myself just this question these last few months, going through old documentation to…

Slicing and Dicing Flooding Domains (2)

9 March 2016 | Comments Off on Slicing and Dicing Flooding Domains (2)

The first post in this series is here. Finally, let’s consider the first issue, the SPF run time. First, if you’ve been keeping track of the SPF run time in several locations throughout your network (you have been, right? Right?!? This should be a regular part of your documentation!), then you’ll know when there’s a…

Slicing and Dicing Flooding Domains (1)

2 March 2016 | Comments Off on Slicing and Dicing Flooding Domains (1)

This week two different folks have asked me about when and where I would split up a flooding domain (IS-IS) or area (OSPF); I figured a question asked twice in one week is worth a blog post, so here we are… Before I start on the technical reasons, I’m going to say something that might…

Why you should care about complexity

29 February 2016 |

If you look across a wide array of networking problems, you will see what is an apparently wide array of dissimilar and unrelated problems engineers deal with on a daily basis. For instance— Should I split this flooding domain into multiple parts? If so, where should I divide it? Which routing protocol should I use…