Blog Posts in March 2015

Too Many Details Can Hurt You (or Why You Need the Fundamentals First)

The IPv6 Security Summit at the Troopers conference always has a few awesome IPv6 presentations (many people claim Troopers is the conference to attend if you’re serious about IPv6), and this year was no exception. A day after the MLD bashing, Enno Rey delivered a great in-depth presentation on DHCPv6 features and shortcomings.

It seems the DHCPv6 intricacies presented in that talk were too much for some of the attendees – that afternoon I accidentally stumbled upon a visibly distressed gentleman who started our chat with “How could anyone expect us to deploy IPv6 in a production environment?

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Microsegmentation in VMware NSX on Software Gone Wild

VM NIC firewalls have been around for years (they’re also the reason I got my first invitation to the awesome Troopers conference), but it sounds so much better when you call them Microsegmentation (not the one I talked about @ Troopers this year).

Marketing gimmicks aside, VMware NSX includes an interesting in-kernel stateful firewall, and Brad Hedlund was kind enough to explain the intricacies of that feature in Episode 27 of Software Gone Wild

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MLD Considered Harmful

Multicast Listener Discovery (MLD) protocol is well hidden deep in the bowels of IPv6 protocol stack and most of us tend to gloss over it when we discuss IPv6 neighbor discovery process… until MLD raises its ugly head to bite an unsuspecting network administrator.

The problems with MLD are not new (and I wrote exhaustively about them a while ago), but it’s always nice to see other people raise awareness of broken IPv6 features like Enno Rey and his security team did during the IPv6 Security Summit (part of Troopers 15 conference).

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Availability Zones in Overlay Virtual Networks

Amazon Web Services was (AFAIK) one of the first products that introduced availability zones – islands of infrastructure that are isolated enough from each other to stop the propagation of failure or outage across their boundaries.

Not surprisingly, multiple availability zones shouldn’t rely on a central controller (as Amazon found out a few years back), and there are only few SDN controller vendors that are flexible enough to meet this requirement. For more details, watch the free Availability Zones video on my web site (part of Scaling Overlay Virtual Networking webinar).

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You Must Understand the Fundamentals to Be Successful

I was speaking with a participant of an SDN event in Zurich after the presentations, and he made an interesting comment: whenever he experienced serious troubleshooting problems in his career, it was due to lack of understanding of networking fundamentals.

Let me give you a few examples: Do you know how ARP works? What is proxy ARP? How does TCP offload work and why is it useful? What is an Ethernet collision and when would you see one? Why do we need MLD in IPv6 neighbor discovery?

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Evaluation Guide: Encryptors for Metro and Carrier Ethernet

Christoph Jaggi, the author of Metro Ethernet and Carrier Ethernet Encryption Market Overview published an awesome follow-up document: an evaluation guide that lists most of the gotchas one has to be aware of when considering encryption gear, from deployment scenarios, network overhead and key exchange details to operational considerations. If you have to deal with any aspect of network encryption, this document is a must-read.

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We Have to Get Away from the Box-Focused Mentality

I had a great SDN-focused conversation with Terry Slattery during last Interop New York, ago and of course we came to the argument that the CLI is the root of all evil, which started my usual rant. Guess what: not surprisingly that wasn’t what Terry had in mind. He was using the “CLI mentality is bad” as a synonym for “we’re used to configuring our networks one box at a time” (so we should really be talking about box-focused mentality).

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TCP Optimization with Juho Snellman on Software Gone Wild

Achieving 40 Gbps of forwarding performance on an Intel server is no longer a big deal - Juniper got to 160 Gbps with finely tuned architecture - but can you do real-time optimization of a million concurrent TCP sessions on that same box at 20 Gbps?

Juho Snellman from Teclo Networks explained how they got there in Episode 25 of Software Gone Wild… and you’ll learn a ton of things about radio networks on the way.

Enjoy the show!

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Whitebox Switching and Open-Source Networking Are not SDN

One of my readers left this comment to the Four Paths to SDN blog post:

You didn't mention Cumulus. SDN protocols become much less important when you have an open Linux switch platform. You can compile and install your own management daemon and implement whatever protocol best suits the task (and blend local and remote control).

Here’s my usual response to this line of thinking:

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Estimating BGP Convergence Time

One of my readers sent me this question:

I have an Internet edge setup with two routers connected to two upstream ISPs and receiving full BGP routing table from them. I’m running iBGP between my Internet routers. Is there a formula to estimate convergence time if one of my uplinks fail? How many updates will I need to get the entire 512K routes in BGP table and also how much time it would take?

As always, the answer is it depends.

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Scalable Load Balancing with Avi Networks on Software Gone Wild

How many times have you received exact specifications of the traffic the e-commerce platform you have to deploy will generate? How do you buy a load balancer (application delivery controller in marketese) to support that (somewhat unknown) amount of traffic? In most cases, you buy a box that’s several times too big for the traffic the site is receiving most of the time, and still crashes under peak load.

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Cisco ACI – a Stretched Fabric That Actually Works

In mid-February a blog post on Cisco’s web site announced stretched ACI fabric (bonus points for not using marketing grammar but talking about a shipping product). Will it work better than other PowerPoint-based fabrics? You bet!

What’s the Big Deal?

Cisco’s ACI fabric uses distributed (per-switch) control plane with APIC controllers providing fabric configuration and management functionality. In that respect, the ACI fabric is no different from any other routed network, and we know that those work well in distributed environments.

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Free Online Introduction to SDN and Network Automation Training

Want to know more about SDN and network automation/programmability, but don’t know where to start? Why don’t you try the free Introduction to SDN and Network Automation training available on – you’ll get seven hours of high-quality content that will help you understand where it might make sense to use SDN technologies in your network and what SDN, OpenFlow, NFV, NETCONF, Ansible, YAML, Jinja and a few other acronyms are all about.

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Response: Why Technology Still Matters

My good friend Tom Hollingsworth wrote a great blog post about hypermyopia in the networking industry. I agree with most everything he wrote (I have to – I’m always telling people to focus on business needs and to change their mentality before relying on shiny new gizmos), but I still think it’s crucial to consider the technology used in products we’re looking at.

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