Do you need VXLAN in your data center or could you continue using traditional bridging? Do layer-2 fabrics make sense or are they a dead end in the evolution of virtual networking?

I tried to provide a few high-level answers in the Introduction to VXLAN video which starts the VXLAN Technical Deep Dive webinar. The public version of the video is now available on ipSpace.net Free Content web site.

Marek Majkowski published an awesome real-life story on CloudFlare blog: users experienced occasional short-term sluggish performance and while everything pointed to a network problem, it turned out to be a garbage collection problem in Linux kernel.

Takeaway: It might not be the network's fault.

Also: How many people would be able to troubleshoot that problem and fix it? Technology is becoming way too complex, and I don’t think software-defined-whatever is the answer.

When writing the Packet- and Flow-Based Forwarding blog post, I tried to find a good definition of flow-based forwarding (and I was not the only one being confused), and the one from Junos SRX documentation is as good as anything else I found, so let’s use it.

TL&DR: Flow-based forwarding is a valid technical concept. However, when mentioned together with OpenFlow, it’s mostly marketing fluff.

If you’re a host running on an IPv6-only network, you might want to detect the IPv6 prefix used for NAT64 (for example, to transform IPv4 literals a clueless idiot embedded into a URL into IPv6 addresses).

Apple has a wonderful developer-focused page describing NAT64 and DNS64, including the way they synthesize IPv6 addresses from IPv4 literals. You (RFC 6919) MUST read it.

I don’t like to correct my friends in public, but if someone says “I still believe that flow-based technologies will exceed the capabilities of packet-based technologies” (see Network Break 53), it’s time to revisit the networking fundamentals.

What is a flow?

According to Wikipedia (but what do they know…):

You might be familiar with the idea of using BGP as an SDN tool that pushes forwarding entries into routing and forwarding tables of individual devices, allowing you to build hop-by-hop path across the network (more details in Packet Pushers podcast with Petr Lapukhov).

Researchers from University of Louvain, ETH Zürich and Princeton figured out how to use OSPF to get the same job done and called their approach Fibbing. For more details, listen to Episode 45 of Software Gone Wild podcast with Laurent Vanbever (one of the authors), visit the project web site, or download the source code.

Wow, another year swooshed by. I can’t believe it’s almost gone. Maybe it’s all the travels I had throughout the year, and I MUST start with a huge THANK YOU to whoever is watching after me – there wasn’t a single major SNAFU.

Next, I’d like to thank the people who caused all that travel: attendees of my workshops.

A while ago I described why some storage vendors require end-to-end layer-2 connectivity for iSCSI replication.

TL&DR version: among other things, they might have been too lazy to implement iSCSI checksums and rely on Ethernet checksums because TCP/IP checksums are not good enough.

It turns out even Ethernet checksums fail every now and then.

I love stumbling upon new networking-focused blogs. Many of my old friends switched to the dark side vendors and stopped blogging, others simply gave up, and it seems like there aren’t that many engineers that would like to start this experiment.

One of the obvious first questions is always “what should I write about” and my reply is always “it doesn’t really matter – make sure it’s useful.”

I love listening to the Datanauts podcast (Ethan and Chris are fantastic hosts), starting from the very first episode (hyper-converged infrastructure) in which Chris made a very valid comment along the lines of “with the hyper-converged infrastructure it’s possible to get so many things done without knowing too much about any individual thing…” and I immediately thought “… and what happens when it fails?”

Do you want to know more about Cumulus Linux after learning what data center architectures it supports, what base technologies it uses, and how you can use it to simplify network configurations? It’s time to explore Cumulus Linux architecture (part 5 of the presentation Dinesh Dutt had during the Data Center Fabrics webinar).

One of the engineers listening to my DMVPN webinars sent me a follow-up question (yes, I always try to reply to them) asking how to implement direct Internet access from the spoke sites (aka local exit) in combination with split default routing you have to use in DMVPN Phase 2 or Phase 3 networks.

It’s really simple: either you have a design requirement that requires split default routing, or you don’t.

One of my readers read the Ars Technica article on ads communicating with other devices via ultrasound and wondered whether something similar could be done for IP.

Not surprisingly, someone already did it. A quick google search found this tutorial which explains how to run IP stack over Gnuradio (at speeds that were last experienced with dial-up modems 30 years ago).

I was asked to present a data-center-related talk last week and decided to focus on one of my favorite topics: because most people don’t have more than a few hundred servers in their data center, they don’t need more than two switches (or a rack of servers).

Not surprisingly, an equipment reseller sitting in the room was not amused.

The video and the slide deck are already online, but there’s a minor challenge: the whole event was in Slovenian ;) However, I plan to record the same topic in English once my SDN travels stop.

I was really excited when Juniper announced Junos Fusion. I hoped for QFabric Done Right, but after watching the NFD10 video describing the architecture, I was disappointed: they reinvented Fabric Extenders.

The blog post was slightly updated on November 14th 2015 based on feedback received from Juniper engineers.