DC Fabric Segment Routing Use Case (5)

7 September 2016 | Comments Off on DC Fabric Segment Routing Use Case (5)

In this, the last post on DC fabrics as a Segment Routing use case, I mostly want to tie up some final loose ends. I will probably return to SR in the future to discuss other ideas and technical details. Anycast Anyone who keeps up with LinkedIn knows anycast plays a major role in many…

On Definitions: Whatever is Forwarding Information?

5 September 2016 |

After last week’s, a reader left a comment noting “I2RS doesn’t manipulate forwarding data.” If I2RS isn’t “manipulating forwarding data,” then what, precisely, is it doing? I thought it’s worth a post to try and help folks understand the definitions in this space—except, as you’ll soon discover, there are no definitions here. In fact, it’s…

An I2RS Overview

31 August 2016 |

What is the Interface to the Routing System (I2RS), and why do we need it? To get a good I2RS overview, consider the following illustration for a moment— What does the interface between, say, BGP and the routing table (RIB) actually look like? What sort of information is carried over this interface, and why? A…

On the ‘net: I2RS on Packet Pushers

24 August 2016 | Comments Off on On the ‘net: I2RS on Packet Pushers

While Greg was at the IETF in Berlin, Sue Hares and I—the two current co-chairs of the I2RS working group—had a general discussion around what the big idea is and where the working group is headed. You can listen to the recording at Packet Pushers.

DC Fabric Segment Routing Use Case (4)

22 August 2016 |

In the last post in this series, I discussed using SR labels to direct traffic from one flow onto, and from other flows off of, a particular path through a DC fabric. Throughout this series, though, I’ve been using node (or prefix) SIDs to direct the traffic. There is another kind of SID in SR…

DC Fabric Segment Routing Use Case (3)

10 August 2016 | Comments Off on DC Fabric Segment Routing Use Case (3)

In the second post in this series, we considered the use of IGP-Prefix segments to carry a flow along a specific path in a data center fabric. Specifically, we looked at pulling the green flow in this diagram— —along the path [A,F,G,D,E]. Let’s assume this single flow is an elephant flow that we’re trying to…

Layer 2 Routing—Haven’t we been here before?

2 August 2016 | Comments Off on Layer 2 Routing—Haven’t we been here before?

We often think the entire Internet, as we know it, just popped out of “thin air,” somehow complete and whole, with all the pieces in place. In reality, there have been many side roads taken, and many attempts to solve the problem of pushing the maximum amount of data across a wire along the way.…

DC Fabric Segment Routing Use Case (2)

28 July 2016 |

In the first post we covered a bit of the basics around segment routing in the data center. Let’s return to the first use case to see if we can figure out how we’d actually implement the type of traffic steering needed to segregate mouse and elephant flows. Let’s return to our fabric and traffic…

On the ‘net: What does a control plane do?

21 July 2016 | Comments Off on On the ‘net: What does a control plane do?

To really understand Software Defined Networks (SDNs), we need to start from a place far different than the top of the current hype cycle. Instead, where we need to start is thinking about what a control plane actually does in a packet switched network. There seem to be just a few specific things involved in…

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…