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…

Micromanaging networks considered harmful: on (k)nerd knobs

2 September 2015 | Comments Off on Micromanaging networks considered harmful: on (k)nerd knobs

Nerd Knobs (or as we used to call them in TAC, knerd knobs) are the bane of the support engineer’s life. Well, that and crashes. And customer who call in with a decoded stack trace. Or don’t know where to put the floppy disc that came with the router into the router. But, anyway… What…

Liskov Substitution and Modularity in Network Design

17 August 2015 | Comments Off on Liskov Substitution and Modularity in Network Design

Furthering the thoughts I’ve put into the forthcoming book on network complexity… One of the hardest things for designers to wrap their heads around is the concept of unintended consequences. One of the definitional points of complexity in any design is the problem of “push button on right side, weird thing happens over on the…