Learning to Ride

1 August 2022 |

Have you ever taught a kid to ride a bike? Kids always begin the process by shifting their focus from the handlebars to the pedals, trying to feel out how to keep the right amount of pressure on each pedal, control the handlebars, and keep moving … so they can stay balanced. During this initial learning phase, the kid will keep their eyes down, looking at the pedals, the handlebars, and . . . the ground.

After some time of riding, though, managing the pedals and handlebars are embedded in “muscle memory,” allowing them to get their head up and focus on where they’re going rather than on the mechanical process of riding. After a lot of experience, bike riders can start doing wheelies, or jumps, or off-road riding that goes far beyond basic balance.
Network engineer—any kind of engineering, really—is the same way.

On Building a Personal Brand

13 June 2022 | Comments Off on On Building a Personal Brand

How do you balance loyalty to yourself and loyalty to the company you work for?

This might seem like an odd question, but it’s an important component of work/life balance many of us just don’t think about any longer because, as Pete Davis says in Dedicated, we live in a world of infinite browsing. We’re afraid of sticking to one thing because it might reduce our future options. If we dedicate ourselves to something bigger than ourselves, then we might lose control of our direction. In particular, we should not dedicate ourselves to any single company, especially for too long.

Revisiting BGP Convergence

6 June 2022 |

My video on BGP convergence elicited a lot of . . . feedback, mainly concerning the difference between convergence in a data center fabric and convergence in the DFZ. Let’s begin here—BGP hunt and the impact of the MRAI are very real in the DFZ. Withdrawing a route can take several minutes.

What about the much more controlled environment of a data center fabric?

Several folks pointed out that the MRAI is often set to 0 in DC fabrics (and many implementations by default). Further, almost all implementations will use an MRAI of 0 for the first received update, holding the second and subsequent advertisements by the MRAI. Several folks also pointed out that all the paths through a DC fabric are the same length, so the second part of the equation is also very small.

These are good points—how do they impact BGP convergence? Let’s use the network below, a small slice of a five-stage butterfly fabric, to think it through. Assume every router is in a different AS, so all the peering sessions are eBGP.

BGP Policy (Part 7)

9 May 2022 | Comments Off on BGP Policy (Part 7)

At the most basic level, there are only three BGP policies: pushing traffic through a specific exit point; pulling traffic through a specific entry point; preventing a remote AS (more than one AS hop away) from transiting your AS to reach a specific destination. In this series I’m going to discuss different reasons for these kinds of policies, and different ways to implement them in interdomain BGP.

There are cases where an operator does not traffic to be forwarded to them through some specific AS, whether directly connected or multiple hops away. For instance, AS65001 and AS65005 might be operated by companies in politically unfriendly nations. In this case, AS65001 may be legally required to reject traffic that has passed through the nation in which AS65005 is located. There are at least three mechanisms in BGP that are used, in different situations, to enforce this kind of policy.

BGP Policy (Part 6)

3 May 2022 | Comments Off on BGP Policy (Part 6)

At the most basic level, there are only three BGP policies: pushing traffic through a specific exit point; pulling traffic through a specific entry point; preventing a remote AS (more than one AS hop away) from transiting your AS to reach a specific destination. In this series I’m going to discuss different reasons for these kinds of policies, and different ways to implement them in interdomain BGP.

In this post I’m going to cover local preference via communities, longer prefix match, and conditional advertisement from the perspective of AS65001 in the following network—

BGP Policies (Part 5)

25 April 2022 | Comments Off on BGP Policies (Part 5)

At the most basic level, there are only three BGP policies: pushing traffic through a specific exit point; pulling traffic through a specific entry point; preventing a remote AS (more than one AS hop away) from transiting your AS to reach a specific destination. In this series I’m going to discuss different reasons for these kinds of policies, and different ways to implement them in interdomain BGP.

In this post I’m going to cover AS Path Prepending from the perspective of AS65001 in the following network—

BGP Policies (Part 4)

4 April 2022 | Comments Off on BGP Policies (Part 4)

At the most basic level, there are only three BGP policies: pushing traffic through a specific exit point; pulling traffic through a specific entry point; preventing a remote AS (more than one AS hop away) from transiting your AS to reach a specific destination. In this series I’m going to discuss different reasons for these kinds of policies, and different ways to implement them in interdomain BGP.

In this post, I’ll cover the first of a few ways to give surrounding autonomous systems a hint about where traffic should enter a network. Note this is one of the most vexing problems in BGP policy, so there will be a lot of notes across the next several posts about why some solutions don’t work all that well, or when they will and won’t work.

There are at least three reasons an operator may want to control the point at which traffic enters their network, including:

BGP Policies (Part 2)

14 March 2022 | Comments Off on BGP Policies (Part 2)

At the most basic level, there are only three BGP policies: pushing traffic through a specific exit point; pulling traffic through a specific entry point; preventing a remote AS (more than one AS hop away) from transiting your AS to reach a specific destination. In this series I’m going to discuss different reasons for these kinds of policies, and different ways to implement them in interdomain BGP.

There are many reasons an operator might want to select which neighboring AS through which to send traffic towards a given reachable destination (for instance, 100::/64). Each of these examples assumes the AS in question has learned multiple paths towards 100::/64, one from each peer, and must choose one of the two available paths to forward along. This post wil consider selecting an exit point from the perspective of two more autonomous systems.

BGP Policies (part 1)

7 March 2022 |

At the most basic level, there are only three BGP policies: pushing traffic through a specific exit point; pulling traffic through a specific entry point; preventing a remote AS (more than one AS hop away) from transiting your AS to reach a specific destination. In this series I’m going to discuss different reasons for these kinds of policies, and different ways to implement them in interdomain BGP.

Quality is (too often) the missing ingredient

3 January 2022 | Comments Off on Quality is (too often) the missing ingredient

Software Eats the World?

I’m told software is going to eat the world very soon now. Everything already is, or will be, software based. To some folks, this sounds completely wonderful, but—leaving aside the privacy issues—I still see an elephant in the room with this vision of the future.

Quality.

Let me give you some recent examples.

First, ceiling fans. Modern ceiling fans, in case you didn’t know, don’t rely on the wall switch and pull chains. Instead, they rely on remote controls. This is brilliant—you can dim the light, change the speed of the fan, etc., from a remote control. No unsightly chains hanging from the ceiling.