Blog Posts in December 2022

Happy Holidays and All the Best in 2023!

Two hundred forty blog posts and sixteen webinar sessions later, it’s time for yet another “year gone by” blog post – I’m shutting down my virtual office and will disappear until mid-January. I’ll read my email should someone experience an urgent support problem but won’t reply to 90% of the other stuff coming in.

I hope you’ll find a few days to disconnect from the crazy pace of the networking world, forget all the marketing shenanigans you encountered in 2022, and focus on your loved ones. I would also like to wish you all the best in 2023!

Finally, I couldn’t resist posting a few teasers of what’s coming in early 20231:

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A Quick Look at AWS Scalable Reliable Datagram Protocol

One of the most exciting announcements from the last AWS re:Invent was the Elastic Network Adapter (ENA) Express functionality that uses the Scalable Reliable Datagram (SRD) protocol as the transport protocol for the overlay virtual networks. AWS claims ENA Express can push 25 Gbps over a single TCP flow and that SRD improves the tail latency (99.9 percentile) for high-throughput workloads by 85%.

Ignoring the “DPUs could change the network forever” blogosphere reactions (hint: they won’t), let’s see what could be happening behind the scenes and why SRD improves TCP throughput and tail latency.

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DPU Hype Considered Harmful

The hype generated by the “VMware supports DPU offload” announcement already resulted in fascinating misunderstandings. Here’s what I got from a System Architect:

We are dealing with an interesting scenario where a customer had limited data center space, but applications demand more resources. We are evaluating whether we could offload ESXi processing to DPUs (Pensando) to use existing servers as bare-metal servers. Would it be a use case for DPU?

First of all, congratulations to whichever vendor marketer managed to put that guy in that state of mind. Well done, sir, well done. Now for a dose of reality.

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vagrant-libvirt Dependency Hell

One of the tiny details Open Networking preachers conveniently forget to mention is the tendency of open-source software to use a gazillion small packages from numerous independent sources to get the job done. Vendors selling commercial products (for example, Cumulus Linux) try their best to select the correct version of every package involved in their product; open-source projects could quickly end in dependency hell.

netlab tries to solve the dependency conundrum with well-defined installation scripts. We recommend you start with a brand new Ubuntu server (or VM) and follow the four lines of instructions1. In that case, you usually get a working system unless something unexpected breaks behind the scenes, like what we experienced a few days ago.

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Worth Reading: NetOps Requires AI/ML and Rules

Here’s some common-sense view on hard-coded rules versus machine learning in network operations by Mark Seery – quite often we can specify our response to an event as a simple set of rules, but if we want to identify deviation from “normal” behavior, machine learning might not be a bad idea.

For more details, watch the Event-Driven Network Automation part of Building Network Automation Solutions online course.

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Arista EOS Configuration Automation

I keep getting questions along the lines of “is network automation practical/a reality?” with arguments like:

Many do not see a value and are OK with just a configuration manager such as Arista CVP (CloudVision Portal) and Cisco DNA.

Configuration consistently is a huge win regardless of how you implement it (it’s perfectly fine if the tools your vendor providers work for you). It prevents opportunistic consistency, as Antti Ristimäki succinctly explained:

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Why Would You Need an Overlay Network?

I got this question from one of subscribers:

My VP is not a fan of overlays and is determined to move away from our legacy implementation of OTV, VXLAN, and EVPN1. We own and manage our optical network across all sites; however, it’s hard for me to picture a network design without overlays. He keeps asking why we need overlays when we own the optical network.

There are several reasons (apart from RFC 1925 Rule 6a) why you might want to add another layer of abstraction (that’s what overlay networks are in a nutshell) to your network.

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Running Routing Protocols over MLAG Links

It took vendors like Cisco years to start supporting routing protocols between MLAG-attached routers and a pair of switches in the MLAG cluster. That seems like a no-brainer scenario, so there must be some hidden complexities. Let’s figure out what they are.

We’ll use the familiar MLAG diagram, replacing one of the attached hosts with a router running a routing protocol with both members of the MLAG cluster (for example, R, S1, and S2 are OSPF neighbors).

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netlab: VRF Lite over VXLAN Transport

One of the comments I received after publishing the Use VRFs for VXLAN-Enabled VLANs claimed that:

I’m firmly of the belief that VXLAN should be solely an access layer/edge technology and if you are running your routing protocols within the tunnel, you’ve already lost the plot.

That’s a pretty good guideline for typical data center fabric deployments, but VXLAN is just a tool that allows you to build multi-access Ethernet networks on top of IP infrastructure. You can use it to emulate E-LAN service or to build networks similar to what you can get with DMVPN (without any built-in security). Today we’ll use it to build a VRF Lite topology with two tenants (red and blue).

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Worth Reading: Egress Anycast in Cloudflare Network

Cloudflare has been using ingress anycast (advertising the same set of prefixes from all data centers) for ages. Now they did a giant leap forward and implemented another “this thing can never work” technology: egress anycast. Servers from multiple data centers use source addresses from the prefix that’s advertised by all data centers.

Not only that, in the long-established tradition they described their implementation in enough details that someone determined enough could go and implement it (as opposed to the typical look how awesome our secret sauce is approach from Google).

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Are DPUs Any Good?

After VMware launched DPU-based acceleration for VMware NSX, marketing-focused websites frantically started discussing the benefits of DPUs. Although I’ve been writing about SmartNICs and DPUs for years, it’s time for another closer look at the emperor’s clothes.

What Is a DPU

DPU (Data Processing Unit) is a fancier name for a network adapter formerly known as SmartNIC – a server repackaged into an interface card form factor. We had them for decades (anyone remembers iSCSI offload adapters?)

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