In the Three Paths of Enterprise IT part of Business Aspects of Networking webinar I covered the traditional networking vendor landscape. Let’s try to do the same for SD-WAN.

It’s clear that we had two types of SD-WAN vendors:

A few months ago Johannes Weber sent me a short email saying “hey, I plan to write a few NTP posts” and I replied “well, ping me when you have something ready”.

In the meantime he wrote a veritable NTP bible - a series of NTP-related blog posts covering everything from Why Should I Run My Own NTP Servers to authentication, security and monitoring - definitely a MUST READ if you care about knowing what time it is.

Listening to (some) industry evangelists you would believe that there’s no future in being a networking engineer. After all, all workloads will move into the cloud, and all clients will connect through a universal 5G network… but even if that utopia eventually comes true, you can’t get away from the laws of physics (and the need networking infrastructure).

TL&DR: our new online course will help you master the shiny new world. You can register right now or keep reading ;)

An anonymous (for reasons that will be obvious pretty soon) commenter left a gem on my Disaster Recovery Test Faking blog post that is way too valuable to be left hidden and unannotated.

Here’s what he did:

Once I was tasked to do a DR test before handing over the solution to the customer. To simulate the loss of a data center I suggested to physically shutdown all core switches in the active data center.

That’s the right first step: simulate the simplest scenario (total DC failure) in a way that is easy to recover (power on the switches). It worked…

A subscriber sent me this intriguing question:

Is it not theoretically possible for Ethernet frames to be 64k long if ASIC vendors simply bothered or decided to design/make chipsets that supported it? How did we end up in the 1.5k neighborhood? In whose best interest did this happen?

Remember that Ethernet started as a shared-cable 10 Mbps technology. Transmitting a 64k frame on that technology would take approximately 50 msec (or as long as getting from the East Coast to the West Coast). Also, Ethernet had no tight media access control like Token Ring, so it would be possible for a single host to transmit multiple frames without anyone else getting airtime, resulting in unacceptable delays.

TL&DR: You automate the whole process. What else do you expect?

During the Tech Field Day Extra @ Cisco Live Europe 2019 we were taken on a behind-the-stage tour that included a chat with people who built the Cisco Live network, and of course I had to ask how they automated the whole thing. They said “well, we have the guy that wrote the whole system onsite and he’ll be able to tell you more”. Turns out the guy was my good friend Andrew Yourtchenko who graciously showed the system they built and explained the behind-the-scenes details.

Gregor Hohpe published an excellent series on Martin Fowler’s web site focusing on various aspects of lock-in. If nothing else, you SHOULD read the shades of lock-in part, and combine it with my thoughts on lock-in in data center networking.

Grouping the features needed in a networking stack in a bunch of layered modules is a great idea. Unfortunately, you could place several essential features like error recovery, retransmission, and flow control in several different layers, from the data link layer dealing with individual network segments, to the transport layer dealing with reliable end-to-end transmissions.

Where should we put those modules? As always, the correct answer is it depends, in this particular case, on transmission reliability, latency, and bandwidth cost. You’ll find more details in the Retransmissions and Flow Control part of How Networks Really Work webinar.

How nice would it be to have a fabric health dashboard displaying a summary of numerous parameters you’re interested in (number of operational uplinks, number of BGP sessions…) for every switch in your fabric.

I’m positive you could hack something together using the customization capabilities of your favorite network management system… or you could write a simple data gathering solution like Stephen Harding did while attending the Building Network Automation Solutions online course.

I had an interesting discussion with someone running VMware NSX on top of VXLAN+EVPN fabric a while ago. That’s a pretty common scenario considering:

• NSX’s insistence on having all VXLAN uplink from the same server in the same subnet;
• Data center switching vendors being on a lemming-like run praising EVPN+VXLAN;
• The reluctance of non-FAANG environments to connect a server to a single switch.

Apart from the weird times when someone started tons of new VMs, his fabric was running well.