Responding to Readers: Questions on Microloops

5 March 2018 |

Two different readers, in two different forums, asked me some excellent questions about some older posts on mircoloops. Unfortunately I didn’t take down the names or forums when I noted the questions, but you know who you are! For this discussion, use the network show below. In this network, assume all link costs are one,…

Thoughts on Open/R

21 November 2017 | Comments Off on Thoughts on Open/R

Since Facebook has released their Open/R routing platform, there has been a lot of chatter around whether or not it will be a commercial success, whether or not every hyperscaler should use the protocol, whether or not this obsoletes everything in routing before this day in history, etc., etc. I will begin with a single…

On the ‘web: Openfabric and the trash can of the Internet

27 July 2017 |

I sat with Greg Ferro over at Packet Pushers for a few minutes at the Prague IETF. We talked about Openfabric and how we are overusing BGP in many ways, as well as other odds and ends.

Open Source Routing at NANOG

21 June 2017 |

  If you want to find out more about open source and disaggregated routing for large scale network design, take a look at the recent webinar on this topic over at

Anycast and Latency

30 May 2017 | Comments Off on Anycast and Latency

One of the things I hear from time to time is how smaller Internet facing service deployments, with just a few instances, cannot really benefit from anycast. Particularly in the active-active data center use case, where customers can connect to one data center or another, the cost of advertising the service as an anycast, and…

One the ‘net: The Network Collective and Choosing a Routing Protocol

26 April 2017 |

The Network Collective is a new and very interesting video cast of various people sitting around a virtual table talking about topics of interest to network engineers. I was on the second episode last night, and the video is already (!) posted this morning. You should definitely watch this one! In episode 2 our panel…

Reaction: Openflow and Software Based Switching

6 December 2016 |

Over at the Networking Nerd, Tom has an interesting post up about openflow—this pair of sentences, in particular, caught my eye— The side effect of OpenFlow is that it proved that networking could be done in software just as easily as it could be done in hardware. Things that we thought we historically needed ASICs…

I2RS and Remote Triggered Black Holes

24 October 2016 |

In our last post, we looked at how I2RS is useful for managing elephant flows on a data center fabric. In this post, I want to cover a use case for I2RS that is outside the data center, along the network edge—remote triggered black holes (RTBH). Rather than looking directly at the I2RS use case,…

Elephant Flows, Fabrics, and I2RS

3 October 2016 |

The last post in this series on I2RS argues that this interface is designed to augment, rather than replace, the normal, distributed routing protocol. What sort of use case could we construct that would use I2RS in this way? What about elephant flows in data center fabrics? An earlier post considers how to solve the…

Can I2RS Keep Up? (I2RS Performance)

20 September 2016 |

What about I2RS performance? The first post in this series provides a basic overview of I2RS; there I used a simple diagram to illustrate how I2RS interacts with the RIB— One question that comes to mind when looking at a data flow like this (or rather should come to mind!) is what kind of performance…