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Category: OpenFlow

Is Flow-Based Forwarding Just Marketing Fluff?

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.

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Software-Defined Hardware Forwarding Pipeline on HP Switches

Writing OpenFlow controllers that interact with physical hardware is harder than most people think. Apart from developing a distributed system (which is hard in itself), you have to deal with limitations of hardware forwarding pipelines, differences in forwarding hardware, imprecise abstractions (most vendors still support single OpenFlow table per switch), and resulting bloated flow tables.

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Video: Implementing VLAN-aware Bridge with OpenFlow

Reinventing the wheels makes little sense. Implementing old solutions with new tools might be in the same category, but at least it shows you the power and shortcomings of the new tools.

Building a VLAN-aware bridge in OpenFlow is thus a mandatory case study, and as you’ll see in the video from the OpenFlow Deep Dive webinar, it’s not as easy as it looks. For more details, watch the whole OpenFlow webinar (6 hours of in-depth videos), which you also get by buying Advanced SDN Training or subscription.

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Link Aggregation in OpenFlow Environment

One of my readers couldn’t figure out how to combine Link Aggregation Groups (LAG, aka Port Channel) with OpenFlow:

I believe that in LAG, every traditional switch would know how to forward the packet from its FIB. Now with OpenFlow, does the controller communicate with every single switch and populate their tables with one group ID for each switch? Or how does the controller figure out the information for multiple switches in the LAG?

As always, the answer is “it depends”, and this time we’re dealing with a pretty complex issue.

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Do We Need NAC and 802.1x?

Another question I got in my Inbox:

What is your opinion on NAC and 802.1x for wired networks? Is there a better way to solve user access control at layer 2? Or is this a poor man's way to avoid network segmentation and internal network firewalls.

Unless you can trust all users (fat chance) or run a network with no access control (unlikely, unless you’re a coffee shop), you need to authenticate the users anyway.

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OpenFlow in HP Campus Solutions on Software Gone Wild

When I finished my SDN workshop @ Interop Las Vegas (including a chapter on OpenFlow limitations), some attendees started wondering whether they should even consider OpenFlow in their SDN deployments. My answer: don’t blame the tool if people use it incorrectly.

Two days later, I discovered HP is one of those companies that knows how to use that tool.

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