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History of DECnet with Dave Oran

16 April 2019 | Comments Off on History of DECnet with Dave Oran

Dave Oran joins Donald and I to talk about the history of DECnet at Digital Equipment—including the venerable IS-IS interior gateway protocol. Outro Music: Danger Storm Kevin MacLeod (incompetech.com) Licensed under Creative Commons: By Attribution 3.0 License http://creativecommons.org/licenses/by/3.0/

Recent Changes in LSR

11 December 2018 | Comments Off on Recent Changes in LSR

IS-IS Multi Instance: RFC8202

16 October 2017 | Comments Off on IS-IS Multi Instance: RFC8202

Multi-Instance IS-IS One of the nice things about IS-IS is the ability to run IPv6 and IPv4 in the same protocol, over a single instance. So long as the two topologies are congruent, deploying v6 as dual stack is very simply. But what if your topologies are not congruent? The figure below illustrates the difference.…

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.

DC Fabric Segment Routing Use Case (1)

11 July 2016 |

A couple of weeks ago, I attended a special segment routing Networking Field Day. This set me to thinking about how I would actually use segment routing in a live data center. As always, I’m not so concerned about the configuration aspects, but rather with what bits and pieces I would (or could) put together…

DR versus DIS: What’s the Diff?

10 May 2016 |

OSPF and IS-IS, both link state protocols, use mechanisms that manage flooding on a broadcast link, as well as simplify the shortest path tree passing through the broadcast link. OSPF elects a Designated Router (or DR) to simplify broadcast links, and IS-IS elects a Designated Intermediate System (or DIS—a topic covered in depth in the…

Flooding Domains versus Areas

26 April 2016 |

At a fundamental level, OSPF and IS-IS are similar in operation. They both build neighbor adjacencies. They both use Dijkstra’s shortest path first (SPF) to find the shortest path to every destination in the network. They both advertise the state of each link connected to a network device. There are some differences, of course, such…

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…

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…

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