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Category: overlay networks

Video: Scale-Out NAT

Network Address Translation (NAT) is one of those stateful services that’s almost impossible to scale out, because you have to distribute the state of the service (NAT mappings) across all potential ingress and egress points.

Midokura implemented distributed stateful services architecture in their Midonet product, but faced severe scalability challenges, which they claim to have solved with more intelligent state distribution.

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Hardware Gateways in Overlay Virtual Networks

Whenever I’m running an SDDC workshop or doing on-site SDN/SDDC-related consulting, the question of hardware gateways between overlay virtual networks and physical world inevitably pops up.

My usual answer: You have to understand (A) what type of gateway you need, (B) what performance you need and (C) what form factor will give you that performance. For more details, watch the Hardware Gateways video from Scaling Overlay Virtual Networks webinar

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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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Scaling Overlay Networks: Scale-Out Control Plane

A week or so ago I described why a properly implemented hypervisor-based overlay virtual networking data plane is not a scalability challenge; even though the performance might decrease slightly as the total number of forwarding entries grow, modern implementations easily saturate 10GE server uplinks.

Scalability of the central controller or orchestration system is a totally different can of worms. As I explained in the Scaling Overlay Networks, the only approach that avoids single failure domain and guarantees scalability is scale-out control plane architecture.

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Scaling Overlay Networks: Distributed Data Plane

Thou Shalt Have No Chokepoints” is one of those simple scalability rules that are pretty hard to implement in real-life products. In the Distributed Data Plane part of Scaling Overlay Networks webinar I listed data plane components that can be easily distributed (layer-2 and layer-3 switching), some that are harder to implement but still doable (firewalling) and a few that are close to mission-impossible (NAT and load balancing).

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Just Published: Overlay Virtual Networks in Software Defined Data Centers

Overlay virtual networks are one of my favorite topics – it seems I wrote over a hundred blog posts describing various aspects of this emerging (or is it reinvented) technology since Cisco launched VXLAN in 2011.

During the summer of 2014 I organized my blog posts on overlay networks and SDDC into a digital book. I want to make this information as useful and as widely distributed as possible – for a limited time you can download the PDF free of charge.

Learn more about the book

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Scaling the Cloud Security Groups

Most overlay virtual networking and cloud orchestration products support security groups more-or-less-statefulish ACLs inserted between VM NIC and virtual switch.

The lure of security groups is obvious: if you’re willing to change your network security paradigm, you can stop thinking in subnets and focus on specifying who can exchange what traffic (usually specified as TCP/UDP port#) with whom.

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Does a Cloud Orchestration System Need an Underlying SDN Controller?

A while ago I had an interesting discussion with a fellow SDN explorer, in which I came to a conclusion that it makes no sense to insert an overlay virtual networking SDN controller between cloud orchestration system and virtual switches. As always, I missed an important piece of the puzzle: federation of cloud instances.

2014-11-04 16:48Z: CJ Williams sent me an email with information on SDN controller in upcoming Windows Server release. Thank you!

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Overlay-to-Underlay Network Interactions: Document Your Hidden Assumptions

If you listen to the marketing departments of overlay virtual networking vendors, it looks like the world is a simple place: you deploy their solution on top of any IP fabric, and it all works.

You’ll hear a totally different story from the physical hardware vendors: they’ll happily serve you a healthy portion of FUD, hoping you swallow it whole, and describe in gory details all the mishaps you might encounter on your virtualization quest.

The funny thing is they’re all right (not to mention the really fun part when FUDders change sides ;).

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