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.


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.

Thoughts on Auto Disaggregation and Complexity

15 November 2021 | Comments Off on Thoughts on Auto Disaggregation and Complexity

Way in the past, the EIGRP team (including me) had an interesting idea–why not aggregate routes automatically as much as possible, along classless bounds, and then deaggregate routes when we could detect some failure was causing a routing black hole? To understand this concept better, consider the network below.

Hedge 105: Johan Gustawsson and Changing Provider Architectures

20 October 2021 |

Many service providers have the feeling that they “didn’t do anything wrong, but somehow we still lost.” How are providers reacting to the massive changes in the networking field, and how are they trying to regain their footing so they can move into the coming decades better positioned to compete? Join Johan Gustawsson, Tom Ammon, and Russ White as we discuss the impact of merchant silicon and changing applications on the architecture of service providers.

Thoughts on the Collapsed Spine

21 September 2021 |

One of the designs I’ve been encountering a lot of recently is a “collapsed spine” data center network, as shown in the illustration below.

Russ’ Rules of Network Design

14 September 2021 | Comments Off on Russ’ Rules of Network Design

We have the twelve truths of networking, and possibly Akin’s Laws, but is there a set of rules for network design? I couldn’t find one, so I decided to create one, containing 18 laws I’ve listed below.

The Grass is Always Greener

9 August 2021 |

This last week I was talking to someone at a small startup that intends to eliminate all the complex routing from campus networks. In the past, when reading blog posts about Kubernetes, I’ve read about how it was designed to eliminate routing protocols because “routing protocols are so complex.”

Color me skeptical.

NATs, PATs, and Network Hygiene

13 July 2021 | Comments Off on NATs, PATs, and Network Hygiene

While reading a research paper on address spoofing from 2019, I ran into this on NAT (really PAT) failures—

In the first failure mode, the NAT simply forwards the packets with the spoofed source address (the victim) intact … In the second failure mode, the NAT rewrites the source address to the NAT’s publicly routable address, and forwards the packet to the amplifier. When the server replies, the NAT system does the inverse translation of the source address, expecting to deliver the packet to an internal system. However, because the mapping is between two routable addresses external to the NAT, the packet is routed by the NAT towards the victim.

The Hedge 85: Terry Slattery and the ROI of Automation

26 May 2021 | Comments Off on The Hedge 85: Terry Slattery and the ROI of Automation

It’s easy to assume automation can solve anything and that it’s cheap to deploy—that there are a lot of upsides to automation, and no downsides. In this episode of the Hedge, Terry Slattery joins Tom Ammon and Russ White to discuss something we don’t often talk about, the Return on Investment (ROI) of automation.

Is it really the best just because its the most common?

24 May 2021 | Comments Off on Is it really the best just because its the most common?

I cannot count the number of times I’ve heard someone ask these two questions—

  • What are other people doing?
  • What is the best common practice?

While these questions have always bothered me, I could never really put my finger on why. I ran across a journal article recently that helped me understand a bit better. The root of the problem is this—what does best common mean, and how can following the best common produce a set of actions you can be confident will solve your problem?

The Effectiveness of AS Path Prepending (2)

17 May 2021 | Comments Off on The Effectiveness of AS Path Prepending (2)

Last week I began discussing why AS Path Prepend doesn’t always affect traffic the way we think it will. Two other observations from the research paper I’m working off of were:

  • Adding two prepends will move more traffic than adding a single prepend
  • It’s not possible to move traffic incrementally by prepending; when it works, prepending will end up moving most of the traffic from one inbound path to another

A slightly more complex network will help explain these two observations.