Recent Changes in LSR

11 December 2018 | 0 Comments

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.…

Video: Do Remote LFAs really solve microloops?

11 September 2017 | 2 Comments

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

27 July 2017 | 1 Comment

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.

iSPF verse PRC

7 June 2017 | 3 Comments

Microloops Explained (in video)

22 May 2017 | 4 Comments

This is the blog post by Ivan I discuss in the video, and this is an older post here on Rule11 about the same topic, if you prefer your explanations written.

DC Fabric Segment Routing Use Case (1)

11 July 2016 | 3 Comments

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 | 6 Comments

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 | 2 Comments

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 | 2 Comments

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…