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.

Imagine you’d design your network by documenting the desired traffic flow across the network under all failure conditions, and only then do a low-level design, create configurations, and deploy the network… while being able to use the desired traffic flows as a testing tool to verify that the network still behaves as expected, both in a test lab as well as in the live network.

You might remember all the fuss about various encapsulations used in overlay virtual networking… just because one wouldn’t be good enough (according to Andrew Lerner “we provide users with choice” actually means “we can’t decide which product to offer you”).